UNDERGRADUATE THESIS PROJECT PROPOSALDepartment of Chemical Engineering

De La Salle University – Manila

Efficiency of Carbon Capture by Aqueous Ammoniafrom Combustion of Semirara Industrial Grade Sub-bituminous Coal

Submitted by:

Stephanie Jane P. SiyChemical Engineering Minor in Semiconductor Processing

Janina Charisse VillanuevaChemical Engineering

Alexis PulhinChemical Engineering

MERECHESection EA1 (8 a.m.)November 30, 2010

Thesis Adviser: PhD. Susan A. RocesThesis Co-Adviser: PhD. Nathaniel P. Dugos

On my honor as a University student, on this assignment I have neither given norreceived unauthorized aid as defined by the Guidelines on Academic Honesty

of the Student Handbook.Signed ___________________________________

Table of Contents

List of Tables....................................................................................................................................iList of Figures..................................................................................................................................iiChapter 1: Introduction....................................................................................................................1

1.1 Background of the Study...................................................................................................11.2 Problem Statement............................................................................................................11.3 Objectives..........................................................................................................................2

1.3.1 General Objectives.....................................................................................................21.3.2 Specific Objectives....................................................................................................2

1.4 Significance of the Study..................................................................................................21.5 Scope and Limitations.......................................................................................................2

Chapter 2: Review of Related Literature.........................................................................................42.1 Coal: Its General Properties and its Uses..........................................................................4

2.1.1 World Coal Consumption..........................................................................................42.1.2 Environmental Impacts of Coal Consumption and Implemented Regulations.........62.1.3 Coal Consumption and CO2 Emission in the Philippines..........................................72.1.4 Coal in the Philippines...............................................................................................72.1.5 Regulations implemented on Reducing CO2 Emissions in the Philippines...............8

2.2 Carbon Capture Technologies...........................................................................................92.2.1 Chemical Looping Combustion or Chemical Looping Reforming...........................92.2.2 Adsorption...............................................................................................................102.2.3 Absorption...............................................................................................................11

2.3 Incorporation of Ammonia in Decarbonisation Absorption...........................................14Chapter 3: Theoretical Framework................................................................................................16

3.1 Chemical Properties of Ammonia...................................................................................163.2 Reactions Involved in Ammonia Decarbonization.........................................................173.3 NH3-CO2 –H2O Equilibrium Diagram.............................................................................183.4 Absorption.......................................................................................................................18

3.4.1 Material balance.......................................................................................................183.4.2 Limiting Gas-Liquid Ratio......................................................................................193.4.3 Multicomponent Absorption....................................................................................19

3.5 Wetted-Wall Column......................................................................................................20Chapter 4: Materials and Methodology.........................................................................................21

4.1 Materials..........................................................................................................................214.2 Experimental Setup.........................................................................................................214.3 Experimental Procedures................................................................................................22

4.3.1 Combustion of Semirara Coal.................................................................................224.3.2 Preparation of Aqueous Ammonia Sample............................................................23

References......................................................................................................................................24Appendix........................................................................................................................................29

A. Calculations.....................................................................................................................29B. Materials Safety Data Sheet................................................................................................30

List of Tables

Chapter 2

Table 2.1 Updated coal consumption statistics (in thousand short tons) of the world and top 40 countries as conducted by the Energy Information Administration during the year 2008....................................................5

Table 2.2 Update coal CO2 emission statistics (in million metric tons) of the world and top 40 countries as conducted by the Energy Information Administration during the year 2008..............................................................6

Table 2.3 Industrial grade Semirara coal constituents obtained from the Semirara Mining Corporation.............................................................................8

Chapter 3

Table 3.1 Physical properties of ammonia (NH3) obtained from Perry’s Chemical Engineering Handbook..............................................................16

Table 3.2 Vapor pressure of ammonia (NH3) and corresponding temperatureas obtained from Perry’s Chemical Engineering Handbook..........................................................16

Table 3.3 List of equilibrium reactions involved in ammonia absorption...................................................................................................................17

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List of Figures

Chapter 2

Figure 2.1 Rapid screening apparatus incorporated in the methodologies of Aronu et al. and Ma’mun et al. as obtained from Aronu et al. (2009).............................................................................................13

Figure 2.2 Schematic diagram of the procedures used by Puxty et al. (2010)in determining the load capacities of ammonia and MEA.............................................................14

Chapter 3

Figure 3.1 Ternary diagram of NH3-CO2 –H2O system at 40˚C and 1 baras presented in UNIQUAC model.................................................................................................18

Figure 3.2 Overall volumetric mass transfer coefficient vs.gas-liquid ratio (Qiu et al., 2010)...................................................................................................19

Chapter 4

Figure 4.1 Qian’s wetted-wall column design...............................................................................21

Figure 4.2 Experimental setup.......................................................................................................21

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Chapter 1: Introduction

1.1 Background of the Study

As the world is experiencing the dilemmas brought about by global warming, scientist are growing more aware about the consequences that result from technological advancement. As the preservation of the stability of nature is deemed crucial at these times, various researches are conducted to determine the sources that caused this and to find solutions that would prevent further degradation of the environment. Recently, there devised methods of controlling, hiding and, even highly recommended the total elimination of greenhouse gases.

Researches were conducted in order to find the solution to this problem and thus lead to the emergence of green technologies. However, due to economic and political means, coal and fossil fuels still play a big role in generating energy in industrial sectors since it is made a spectacle in the international market. Considering this situation, carbon dioxide capture is opted as a means of preventing air pollution while the presence of said fuels is still abundant.

So far, methods involved in sequestration of carbon dioxide can be applied before (pre-combustion) or after (post-combustion). Among the said methods are membrane technology, adsorption, absorption, cryogenics, carbon extraction, biotechnology (cyanobacteria) and energy conversion (Feron & Hendriks, 2005). Just recently, among these also include the new carbon capture methods namely chemical looping cycle (CLC) which involves the transfer of oxygen with both the gas and fuel separated (Yang et al., 2008) and chemical looping reforming (CLR) which are done whilst producing synthesis gas (Rydén, Lyngfelt, & Mattisson, 2006). Efficiency of each method will depend on the different parameters applied on the medium, kinds of fuel and the properties of the flue gas produced before, during or after combustion.

CO2 capture and storage (CCS) is currently available for large companies that produce large emissions(Kirchsteiger, 2008). Although promising as it sounds, applying it at a global scale may yet be costly for most to afford. Furthermore, this method could potentially amount to grave hazards. CCS involves storing the collected CO2 underground and that requires transport through pipes. In addition to that, there are uncertainties of situations that may arise from accidental release of CO2 from pipe leaks and what’s worse is that effects may reach globally(Kirchsteiger, 2008). Moreover, the fact that the CO2 gas does not undergo any significant reaction would only lead to its accumulation over the years (Kirchsteiger, 2008). But since solutions are called for at a sooner time, CCS may serve as an off-setter for the time being.

1.2 Problem Statement

In fulfilment of alleviating the effects of greenhouse gases and to increase awareness of this issue, this paper shall disseminate information about one of the clean coal technologies that can be used in third world countries such as the Philippines. One of which is what this paper focuses on, carbon capture using aqueous ammonia.

Previous studies so far elucidate absorption capacities of aqueous ammonia through the generation of artificial flue gas, thus this paper will involve the combustion of Semirara sub-

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bituminous industrial grade coal to produce the flue gas for testing the absorption of aqueous ammonia at different concentrations. Absorption of different aqueous ammonia concentrations shall be determined through the material balance of input and output fluids. Comparison of gas composition before and after absorption process will indicate the efficiency solvent given its corresponding concentration.

1.3 Objectives

1.3.1 General Objectives

This paper aims to prove and evaluate the effectiveness of aqueous ammonia in absorbing carbon dioxide from multi-component flue gas such as combustion products from coal.

1.3.2 Specific Objectives

1. Determine the percent conversion of coal fuel to flue gas by the analysis of the contents of the following gases: CO2, CO, H2, O2, N2, H2O, and SO2.

2. Compute for the pressure of flue gas prior to achieving CO2 partial pressure of 20 kPa.

3. Obtain CO2 content before and after flue gas is made to pass through absorption column.

1.4 Significance of the Study

This main purpose of the study is to help in alleviating pollution and global warming. It aims to discover ways to capture carbon efficiently and effectively. It is designed for lessening carbon emissions (on a large scale) using processes and materials suitable for the Philippine setting; low-cost, abundant, practical and economical techniques which may be easily available to the country’s industries.

So far, studies had gone as far as using mixed CO2 and N2 in order to simulate the flue gas. This time natural flue gas is used to simulate actual combustion of coal in power plants. A small sample of Semirara coal shall be combusted to test the CO2 absorption capacities of aqueous ammonia in different concentrations. The amount of other fuel constituents such as sulphur and hydrogen and their products shall be taken into account since they are absorbable as well. This will determine whether prior processes have to be done to isolate CO2 or CO2

absorption from mixed flue gas is efficient that additional process need not be added.

1.5 Scope and Limitations

The research shall cover the use of ammonium absorption decarbonisation technology in the post combustion setting. Variables such as different concentrations of ammonia shall be used against the combustion of Semirara industrial grade coal. Hence, absorption principles shall be applied. To conform to the space provided by the laboratory, small amounts of samples (10 grams of coal and 10 grams of solvent) and a small scale design of the wet wall column of which dimensions vary from existing literature will be utilized. Since other coal constituents will be

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included as previously mentioned, analysis of the actual conversion of fuel into flue gas is required before doing the analysis of the absorbent. Then after the production of flue gas from combustion, absorption capacity shall be determined from the CO2 content and other absorbed gas content from circulated solvent. The wet wall column shall be fabricated such that dimensions that simply allow contact between solvent and solute. Also, temperature at the absorption part will have to be maintained at 20˚C to prevent the vaporization of ammonia as suggested by literature. Absorption will be indicated by the change of pressure, and through the calculation of the mass fraction of flue gas components at the inlet and outlet.

Factors excluded in this research are the rate of absorption and the gas used for stripping the absorbent of CO2 content for regeneration. Hence this might yet exclude the determination of the mass transfer coefficient. Furthermore, preloading of CO2 gas shall not be included in the procedures.   

 

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Chapter 2: Review of Related Literature

2.1 Coal: Its General Properties and its Uses

Coal is a carbon rich, combustible sedimentary rock that is formed from accumulated fossilized remains of prehistoric colossal life forms, otherwise known as fossil fuel (National Energy Education Development Project). Properties of coal such as their carbon content, inorganic traces and calorific value may vary from the way fossil fuel coalifies. Quality of coalification depends on the organic composition of the material, temperature and pressure related to the depth of the coal’s burial, and the length of time it was left to coalify (World Coal Association). In order to rank coal by its quality, coal is classified into four categories namely anthracite, bituminous, sub-bituminous and lignite.

Coal mainly starts with peat which is usually an immature coal that is previously left to coalify for more or less a million years (Roces, 2010). If given a few million more years, the coal may become lignite which is characterized with a dark brown to black color. Lignite has a calorific value of 4000 to 8300 Btu/lb and this is sufficient to provide energy for generating electricity (Kentucky Educational Television). Then billion years more could gradually coalify the once lignite into sub-bituminous, bituminous and then anthracite. Sub-bituminous coal’s calorific value of 8300 to 13000 Btu/lb is considered to give a cleaner flue gas with its high energy, while bituminous coal has a calorific value of 10000 to 15500 Btu/lb is highly favourable enough to supply intense heat for metallurgic processes (Kentucky Educational Television). Lastly, anthracite, the hardest coal yielding a calorific value of more or less 15000 Btu/lbm and is rarely used in any operations but house heating, therefore lowering its demands in the market (Kentucky Educational Television). The more immature coal contains more combined water.

Besides obtaining coal from mines that contain natural reserves of fossil fuels, coal can also be processed manually. It is important to consider the impurities and non-organic traces that would lower the energy value that coal produces. Therefore, the coal will have to be heated to allow the polymerization of aromatics, releasing impurities and retaining the volatile carbon content (Menendez & Alvarez).

2.1.1 World Coal Consumption

The following history is as stated by the National Energy Education Development Project. Before coal was discovered by the European colonizers, coal was long used by indigenous people such as the native North Americans. Upon the discovery of the European colonizers, it was not given much significance until it became widely used in mass production during the 1800’s. However during the 20th century the demand for coal began its decline as there appeared an increased in demand for petroleum as America enters the “motorized” trend in machinery (Smiley, 2010). It was at the 70’s when coal made a turning point, until its consumption broke the average record until year 2008. Currently, it comprises 23% of the America’s energy supply. Also, according to the latest statistics conducted by the World Coal Association (2010) during 2008, China was the top producer of hard coal, Australia was the top exporter of coal, while Japan was the top importer of coal.

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Coal is widely used by the domestic and industrial sectors to provide energy in daily operations. Being an abundant high energy source, given the fact that it also readily provides energy in its raw form by being burned directly into combustion engines, coal was priced to be one of the cheapest fuels since the 70’s. Another factor that contributed to its low market price would be the expansion of coal markets which was once initiated by European countries and colonies and the improvement of transnational transportation (Ellerman, 1995), therefore leading to the lowering of transportation costs and then the price of oil.

The increasing demand made coal one of the bases of evaluating the GDP of countries since this vein of black gold is what makes a country capable of circulating its economy through the industries that rely on this energy and the exports that will yet supply other industries off-coast. Also this requires tremendous amount of labor force to obtain it. Furthermore, coal has reserves that could last for about 122 years which is longer compare to other fuel sources like oil and gas, which are estimated to last for only about 42 and 60 years based on the current rate of consumption (World Coal Institute, 2010). Reasons like these plus the demand for energy makes coal an object of politics. Currently, the United States, being the residual supplier of coal, is the one dictating the price of coal in the market.

Table 2.1 shows the coal consumption of some countries and the total world consumption during the year 2008. According to the table, the world consumes a total of about 7.3 billion short tons of coal.

Table 2.1 Updated coal consumption statistics (in thousand short tons) of the world and top 40 countries as conducted by the

Energy Information Administration during the year 2008

1 China3004414.6

5 21 Serbia 43805.85

2 United States1120548.4

4 22 Thailand 38282.713 India 632357.45 23 Bulgaria 36385.094 Germany 267881.50 24 Korea, North 33161.935 Russia 249795.88 25 Spain 28553.176 Africa 227447.62 26 Italy 27203.947 Japan 203803.04 27 Brazil 24610.208 Australia 157896.18 28 Vietnam 24588.169 Poland 148914.55 29 France 21119.1810 Korea, South 110522.15 30 Estonia 17415.4211 Turkey 108836.71 31 Mexico 16709.9412 Ukraine 78009.47 32 Israel 14257.3013 Kazakhstan 75922.80 33 Netherlands 14061.0814 Greece 71822.20 34 Philippines 13099.8715 Indonesia 71497.02 35 Hungary 12760.3616 Taiwan 69396.03 36 Bosnia and Herzegovina 12697.5217 United Kingdom 64506.16 37 Hong Kong 12505.6818 Canada 61858.41 38 Pakistan 9249.49

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19 Czech Republic 59851.10 39 Slovakia 8992.6620 Romania 44472.75 40 Chile 8589.82

World 7345641.28

2.1.2 Environmental Impacts of Coal Consumption and Implemented Regulations

The increase consumption of fossil fuels amounted to an increase in the production of greenhouse gases, which in effect led to global warming. The abrupt change in climate raised the awareness of many nations and therefore began the search for alternatives and strategies to prevent the total degradation of the environment. In comparison of the data in Table 2.1 and Table 2.2 (which shows the emissions taken by the same source as that of the previous during the same year) 7 billion short tons of coal during the year 2008 and in turn produced CO2 emission that amounted to over 12 billion metric tons. Also, the same top 40 countries appeared in both tables with the first three having the same order of coal consumption and CO2 emission. Although the rest of the countries are not the same as that of the first three, it is clearly implied that the increase of emission is dependent of the amount of coal burned.

Table 2.2 Update coal CO2 emission statistics (in million metric tons) of the world and top 40 countries as conducted by the

Energy Information Administration during the year 2008

1 China5381.9981

4 21 France 51.836432 United States 2125.1675 22 Brazil 50.69332

3 India1025.5486

5 23 Spain 49.541014 Russia 447.70069 24 Netherlands 45.4125 Japan 441.20269 25 Romania 41.04856 Germany 318.50847 26 Malaysia 35.986597 Korea, South 248.42308 27 Serbia 34.732178 Australia 239.02891 28 Greece 32.873029 Poland 204.02507 29 Hong Kong 32.1758210 Indonesia 179.16124 30 Israel 31.7254611 Taiwan 162.85313 31 Bulgaria 31.6004112 United Kingdom 147.7496 32 Mexico 29.6918713 Kazakhstan 141.45375 33 Philippines 28.4555614 Ukraine 140.17408 34 Pakistan 25.3451215 Canada 128.43991 35 Belgium 19.6902616 Turkey 115.21266 36 Denmark 17.4911617 Korea, North 67.59087 37 Chile 17.1607418 Italy 62.57542 38 Slovakia 15.1938219 Thailand 61.31154 39 Finland 14.7660120 Czech Republic 57.58739 40 Bosnia and Herzegovina 14.29348

World 12897.92507

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The Kyoto Protocol has long fulfilled its part as a policy governing the regulation of greenhouse gases in an international scale. Among the mechanisms involved was the Clean Development Mechanism wherein countries are highly encouraged to implement projects that will help reduce the emission of greenhouse gases (United Nations Framework Convention on Climate Change). This includes the application of scientific research, breaking ground for innovations that could introduce solutions that are not only effective but also economically friendly.

In the long run, there emerged several green innovations that were proven to reduce global warming. However, reluctance in releasing these products due to economical and political causes (Sy, 2008) only nullified the efforts made by the UN to achieve the said objective. In other words, most companies find it difficult to give up the cheapest means of producing energy and resort to it, even if it will contribute to global warming. As mentioned in Kirchsteiger’s (2008) paper, the G8, otherwise known as the group of big eight countries have been supporting the improvement of coal fired power-stations in its efficiency through the help of modern technology, hence resorting to “capturing carbon dioxide”

2.1.3 Coal Consumption and CO2 Emission in the Philippines

Based on the latest updated statistics on coal consumption presented by Table 2.1 and Table 2.2, Philippines ranked 34th in global coal consumption and 33rd in CO2 emissions respectively. According to the DOE of the Philippines, industries that cater cement, energy generators and other processes are the major coal consumers. Their recent studies (as of December 12, 2006) show that out of the 9.5 million metric tons of coal, 73% is used for the generation of energy, 22.5% is used for the processing of cement while the rest of the 3.75% is used by other industries.

Considering this fact, Philippines is among the countries that consume considerable amounts of coal without being able to implement effective methods that could either way reduce or eliminate greenhouse gases.

2.1.4 Coal in the Philippines

According to the Department of Energy (DOE) of the Philippines, our country’s reserves are scattered all over the Philippines, but the largest deposit is located in Semirara Island, Antique, thereby also having the largest coal producer is Semirara Mining Corporation (SMC), which contributes about 92% of the local coal production, but there are also coal mines located in Cebu, Zamboanga Sibuguey, Albay, Surigao and in the Negros Provinces. According to the DOE, and basing it on the 2006 Update of the Philippine Energy Plan (PEP), coal production in 2004 surpassed the 2003 level by 34% from 2.0 MMMT in 2003 to 2.7 MMMT in 2004, owing to improved coal production of big mining companies as well as good weather conditions. Coal production in 2006 as of December 12 stands 2.3 MMT run-of-min, 2.5% which came from small-scale coal mining operations. The DOE claims that there are Philippines coals which are of such high quality that they can be used without the need for coal preparation or blending with imported coals, like the coal deposits from Malangas by the Philippine National Oil Company

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(PNOC) with its Taiwanese partner, in Southern Cebu by Ibalong Resources and Development Corporation (IRDC), and in Batan Island by Rock Energy International Corporation (REIC).

The coal to be used in this research is that mined by Semirara (Semirara Mining Corporation). Semirara coal is classified as sub-bituminous. A pound of this fuel harnesses energy that amounts to around 8600 Btu to 10450 Btu. Other contents that comprise the coal exist in the following ratio: 11-15% moisture, 5-10% ash, 0.3-0.9% sulphur. The industrial grade of Semirara coal particularly contains the following components as shown in table 2.3.

Table 2.3 Industrial grade Semirara coal constituents obtained from the Semirara Mining Corporation

Gross calorific value, Btu/lb (air dried) 8650-9600Proximate anlaysis (air dried, ASTMD3172)  

Ash, % 9-18Fixed carbon, % 32-41Volatile combustible matter 34-41Total sulfur, % (air dried,

ASTMD2015) 0.40-0.90Total Moisture, % (as received) 20-28Residual moisture, (air dried), % 11-15Hardgrove grindability index,% 40-50

Ash fusion temperature, ˚C  Initial deformation temperature,

˚C 1120-1300Hemispherical temperature, ˚C 1140-1380Flow temperature, ˚C 1170-1490

Elemental ash analysis, % (dry basis)  

Sodium (Na2O) 2.00-4.00

Potassium (K2O) 1.00-2.00

2.1.5 Regulations implemented on Reducing CO2 Emissions in the Philippines

Laws and/or acts have been passed in the Philippines concerning the control of carbon dioxide emissions and of other gases (greenhouse gases) imposing harm to Filipinos and to the country’s physical nature. They have been formulated to directly serve the Philippines’ environment (air, land, water resources), to prevent damage and destruction of natural resources and maintain clean, green and healthy surroundings.

Section 2 of the Climate Change Act of 2009 or Republic Act No. 9729 affirms that it is the duty of the state to create policies protecting the people and providing them a clean and healthy environment. The Philippine Agenda 21 allows for the fulfillment of this duty and maintenance of a well and orderly environment. Furthermore, RA 9729 has been established to protect the climate system and for its risk management. One of the primary objectives of this act

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is to stabilize greenhouse gases to prevent the harm they cause – ecologically, socially and economically. In line with this, projects and plans on climate change-related disasters must be implemented. This policy is also in line with the global community’s policy towards climate change. It is also stated in the policy that participation of other industries and institutions in the realization of this act is a must. It is important to control climate change because as the section two of this RA recognizes, the Philippines is susceptible to the consequences brought by climate change (Klima Climate Change Center).

The Biofuels Act of 2006 or Republic Act No. 9367 is an act concerning Biofuel usage in the country. The policy is in charge of lessening reliance on non-domestic fuels regarding the country’s environment and human protection and economic growth. It also focuses on improvement of livelihood with biofuels such as development of indigenous sources of renewable energy, making clean alternative sources of energy (apart from imported oil) abundant and available to all, alleviate greenhouse gases emissions, and increase in levels of income and employment. The act encourages use of biofuels as a better alternative than gasoline and because of its healthy benefits for the whole state (Senate of the Philippines).

The Philippine Clean Air Act of 1999 or Republic Act No. 8749 is an act concerning the control of air pollution. Its principles are resting on the provision of clean air, harmonious environment, healthy ecology and the human right to a clean surrounding and nature. It also is the preventive measure for pollution but at the same time recognizes measures which are going to help achieve the objectives of the policy. Section 3 of RA 8749 must pursue frameworks for sustaining balance, development and protection of the environment. This section also writes that there must be national and comprehensive programs for air pollution management; programs which encourage cooperation and participation of the citizenry and industries in the management of air pollution and which teach proper public information on air quality and on the ways to maintain cleanliness and prevent air pollution (Environmental Management Bureau).

There are many laws that capture caring for the environment and provide support for projects which have potentials in helping the government to achieve their goals. Many environmental laws are leaning on the deterrence and/or treatment of toxic elements found in our surroundings – gases.

2.2 Carbon Capture Technologies

Due to the impending degradation that coal consumption brought about, the search for clean coal technologies began. Among the clean coal technologies discovered, carbon dioxide sequestration is proved to be most suitable to allow the continuation of the demand and usage of coal. As mentioned earlier, innovations resulted to numerous carbon capture technologies that have various affects depending on the properties of gas and parameters applied on the capturing medium. In this proposal, carbon capture technologies that are inclined to the incorporation of thermodynamic chemical reactions, principles and processes are the scope of discussion. Among the technologies known, chemical looping combustion and reforming (CLC/CLR), adsorption and absorption are given focus in order to gain prior knowledge about the proceeding studies.

2.2.1 Chemical Looping Combustion or Chemical Looping Reforming

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Chemical looping combustion (CLC) and reforming (CLR) are novel fuel conversion technologies allowing inherent CO2 separation. Through the cyclic utilization of metal oxides to bring oxygen to the fuel itself, the main advantage of this method is that there is no gas separation step needed to get a concentrated CO2 stream since air and gaseous products produced after combustion of fuel were not mixed together (Yang, et al., 2008). Which means that energy requirements are much lower that for pre- or post combustion capture or for oxyfuel combustion. This technology was first introduced by Richter and Knoche (1983) and Ishida et al. (1987) primarily to increase reversibility of combustion processes so as to utilize materials more effectively. These systems consist of two reactors where different gas streams are in contact with circulating solids, which transports oxygen and heat from one reactor to another. Metal oxides allow such a transport. In the fuel reactor, fuel is oxidized by the metal oxide, and in the second, which is called the air reactor, the metal oxide is reoxidized. If hydrocarbons are used as fuel in CLC (although in princicple, any kind of major fuel can be utilized in CLC), the primary products of the fuel reactor exhaust gas are CO2 and H2O. After condensation of water, a relatively pure CO2 stream is left, which leaves a high potential for CO2 capture, which is really the main advantage of CLC because it avoids usage of too much energy. The air reactor exhaust has consists mainly of nitrogen with some excess oxygen. In the study of Bolhàr-Nordenkampf et al. (2009), two different Ni-based oxygen carriers in a 120kW chemical looping pilot rig was used, and a dual circulating fluidized bed (DCFB) system was designed to obtain high solid circulation, very low residence times and a high power solid inventory ratio, the pilot rig was fuelled with methane at 140kW fuel power. For both oxygen carriers high CH4 conversion and CO2 yield is achieved. In this study, air to fuel ratio and temperature are varied. Higher air to fuel ratio and temperature, decreased CH4 conversion, the problem with this is that they used the word “seemed” to explain this phenomena connecting it to the Ni/NiO ratio, which very much appeared like they didn’t find anything conclusive to really explain why this happened which is why at their conclusion, they stated that further investigation is surely required (Bolhàr-Nordenkampf, et al., 2009). Another study connected to this, is when they used natural ilmenite and natural olivine (only as an additive) as an oxygen carrier material, this study showed that there was reasonable conversion of CO and H2 but, the conversion of natural gas is relatively low, but the adding of natural olivine resulted to a moderate increase of CH4 conversion (Pröll et al., 2009). This basically showed that natural minerals such as oxygen carriers aren’t as effective as metals, when converting hydrocarbons. Another study by Jerndal et al. (2009), used 24 different oxygen carriers, based on NiO, with NiAl2O4 and/or MgAl2O4 and were produced with spray-drying, and found that oxygen carriers supported by MgAl2O4, or where a small amount of MgO was added, displayed an increased fuel conversion when compared to oxygen carriers of NiO supported by NiAl2O4, (Jerndal, et al., 2009) which is quite adverse, because, according to most studies, Ni is the most effective oxygen carrier to convert hydrocarbons.

Another study, de Diego, presented results using CLR in a 900 ˚C circulating fluidized bed reactor using a methane as fuel, again they used an oxygen carrier based on NiO and supported on γ-Al2O3 was used during more than 50 hours of operation and the effect of

different operating variables like temperature, molar ratio and solid circulation rate on CH4 conversion and gas product distribution was analyzed. They found in all conditions, CH4 conversion was very high (greater than 98%) and the most important variable affecting the gas product distribution was the solid circulation rate, that is NiO/CH4 molar ratio. During the

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operation, it was found that the oxygen carrier particles maintained their physical and chemical properties, which suggested the popular notion today that Nickel has a very high durability, which makes it suitable to be an oxygen carrier for a CLR system which was actually used in the aforementioned study (de Diego et al., 2008).

2.2.2 Adsorption

Adsorption is the process which will be used for this study. It is the process wherein a substance of gas and liquid becomes attached to a solid; similar to absorption. The substance adsorbed by the special solid is called an adsorbate. Adsorption happens every day in our environment. The best examples of adsorbates are the pollutants in our environment such as carbon and greenhouse gases (Mithra, 2010).

Many successful carbon capture experiments were done using the process of adsorption and CO2 with a special solid. Plaza et al. (2007) affirmed successful CO2 capture depending on the development of the special solid used and the adsorption capacity. In their study, they used low cost sorbent. They sought different alkylamines as potential sources of sites for CO2 capture. They also considered the effect of impregnation with the use of commercially activated carbon. Their results showed that the amine coating, making the carbon more basic and also increased the amount of nitrogen found in carbon, caused the significant decrease in microporous volume of carbon. As a succeeding result, CO2 physisorption occurred, reducing raw carbon capacity. Another study by Martín et al. (2010) showed the effectiveness of adsorption to capture carbon through techniques on characterization of carbon. They used physical adsorption to determine maximum capacity of carbon to CO2 before and after combustion processes. The adsorption isotherms yielded the values of micropore volume and the energy characteristic of the carbons. They followed on the theoretical framework of Dubinin’s theory. The analysis of these results also gave the equilibrium CO2 uptake of the carbons at various temperatures and pressure. They also noted special cases which resulted to higher values which indicated that CO2 uptake upper-bound around10–11 wt% seemed more realistic for standard activated carbon after combustion. The limit of the before combustion cases would not exceed 60-70%.

In the study of Plaza et al. (2010), they used almond shells as adsorbents for carbon dioxide. They used the process of carbonisation followed by CO2 activation or heat treatment with ammonia (amination). The said procedures resulted to CO2 with high adsorption capacity in pure CO2 and in 15% CO2 in N2. Carbon dioxide activation produced porosity in most of the micropore domain. Heat treatment with ammonia at 800 ˚C on the other hand, produced narrow microporosity in the char and incorporated stable nitrogen functionalities enhancing CO2 selectivity. This process also gave greater carbon yield and shorter soaking time than CO2 activation (M. G. Plaza, et al., 2010).

2.2.3 Absorption

Absorption is another carbon capture process that involves the use of sorbent liquid solvents, usually amine based solvents, to trap CO2 gases, therefore separating it from the other gases that would provide the heat required prior to energy conversion (Feron & Hendriks, 2005). This can be applied in both combustion and pre-combustion stages but according to Feron and

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Hendriks (2005), this process is favoured when decarbonisation was done at pre-combustion. However, the hydrogen gas (H2) must be taken into account since this gas provides significant amount of heat to power steam turbines or fuel cells.

First to be discussed are the parameters considered for different combustion stages where absorption is to be employed. Absorption can be held at the pre-combustion stage or the post-combustion stage. As said earlier, absorption decarbonisation is favoured at pre-combustion. In order to avoid corrosion of equipment due to the acidic properties of CO2 (Ma'mun, Svendsen, Hoff, & Juliussen, 2007), absorption can be preferably done right after gasification of gases before allowing entrance to the equipments. Furthermore, Pennline (2008) stressed the fact that precombustion absorption requires gasification of fuel produces more concentration of CO2

against CO, and then by design, collecting and transporting the CO2 through lower pressure at a higher elevation, therefore making carbon capture process more effective. As for post-combustion absorption process, the volume of the gas should be considered since carbon capture requires the exiting gases to be at low pressure, and thus the design of high volume reactors (Alix et al.). To address that problem, physical designs are incorporated along with absorption like packed columns (Khan, Krishnamoorthi, & Mahmud) and specifically designed fabric membranes of which their efficiencies conform to the principles of hydrodynamics (Alix, et al.).

Next is the selection of the solvent for absorption. According to by Aronu et al. (2009), absorption efficiency of solvents would depend on physical properties such as its solubility, vapour pressure, molecular mass, foaming tendencies and its ability to wear equipment, and also including principles in physical chemistry such as reaction kinetics, energy regeneration and cyclic capacity are also significant in analyzing the absorption capacity of solvent. In addition to that, mass transfer of incoming gases and equilibrium between absorbed particles and absorbent must also be considered (Blauwhoff, Versteeg, & Van Swaaij, 1983). Alkanoamines, like monoethanol for instance, have been one most commonly used since industries sought to address problems on pipe corrosion due to acidification of H2S and CO2. Its rate of reaction (being found with utmost accuracy among all other alkanolamines) was given by the following as compiled and formulated by Blauwhoff et al. (1983):

log10 k2=10.99−2152T ( 1

mol ∙ sec )The availability of such data therefore makes monoethanolamine a good specimen to study absorption. But for the other alkanolamines, equations cannot be justified due to the variations of methodology and concentrations, as Blauwhoff pointed.

The use of MEA however is not economically friendly as it used to be. In fact, according to Yang (2008), equipments that will have to control the parameters such like letting CO2 react with MEA to form a carbamate and heating it later for the release of CO2. What Yang would like to point out, basing upon the study conducted by Idem et al. (2005), was that the repetitive regeneration and reheating of MEA actually constitutes 70% of an energy plant’s total cost. Moreover, Yang also justified that MEA has a small CO2 loading, it is easily worn out by other absorbable waste gases such as SO2, NO2, HCl, HF and oxygen and it also corrodes equipments(Yeh, Resnik, Rygle, & Pennline, 2005).

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Recent studies proved that there are other solvents that could compete with the absorption capacities of MEA in terms of cost and efficiency. One such study conducted by Ma’mun et al. (2007) operated the screening apparatus illustrated in Figure 2.1 at 80˚C atmostpheric pressure to observe the absorption/desorption capacities of the nearly pure assays following solvents: monoethanolamine (MEA), 2-(butylamino)ethanol (BEA), N-methyldiethanolamine (MDEA), 2-(methylamino)ethanol (MMEA), 2-(ethylamino)ethanol (EMEA), 2-(2-aminoethyl-amino)ethanol (AEEA). In so far, AEEA exhibited an almost consistent, linear relationship of loading CO2 and its capacity to absorb CO2 from the water bath at 40˚C up until it reaches 80˚C at the end of the cycle. Also, the fact that AEEA has a lower vapour pressure which indicates that it has lesser volatility.

Figure 2.1 Rapid screening apparatus incorporated in the methodologies of Aronu et al. and Ma’mun et al.

as obtained from Aronu et al. (2009)

Another study conducted by Aronu et al. (2009), evaluates solvents of almost pure concentrations (ranging from 85-99.9% by mass) namely monoethanolamine (MEA), tetraethylenepentamine (TEPA), piperazine (PZ), 2-amino-2-methyl-1-propanol (AMP), N, N’-di- (2 hydroxyethyl) piperazine (DIHEP), N-2-hydroxyethylpiperzine (HEP) and potassium salt of sarcosine (KSAR). In this study, comparison of the efficiency of each sorbent was based off monoethanolamine as a common material used in industrial operations. To determine the sorbents’ the same screening apparatus for analyzing the solvents shown in Figure 2.1 was utilized at the same conditions as the previous. Among the solvents TEPA was able to absorb the most CO2 among other sorbents. However, there appeared to have a decrease in performance due to viscosity when concentration is increased. Nevertheless, TEPA exhibits the capture of more CO2 compared to MEA whose efficiency lowers upon continuous cycles. But since TEPA had the least tendency of desorption, storing captured CO2 and regeneration of this medium may be a problem.

Although there may still be considerations in analysis, like for instance, taking into account the differential increase in temperature as the gas travels through the apparatus, the lean loadings (by mols of CO2 per mol of solvent) given the same reaction rate is sufficient to prove that there are more economic alternatives than the use of MEA. It may still be necessary to conduct experiments that could determine the diverse effects due to the different concentrations on one particular solvent.

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Besides the use of alkanolamine other amine derivatives, there also proposed the use of ammonia (Resnik, 2004; Yeh, et al., 2005) as solvent and liquid sorbent-membrane systems that uses chemical and physical means to sequester CO2 (Teramoto, Takeuchi, Maki, & Matsuyama, 2001). Since the main focus of the research is the ammonium absorption technology, this will be discussed in detail in the following section.

2.3 Incorporation of Ammonia in Decarbonisation Absorption

Ammonia decarbonisation technology has not yet been employed in actual industrial settings however Puxty et al. (2010) stated that ammonia has been proposed as a medium for carbon capture due to its high loading, low energy requirement for regeneration and its resistance against oxidation, although it has to be kept at a low temperature due to its volatility. Example of procedures testing the loading of ammonia as compare to the commercial absorbent, MEA, is based upon the mass of CO2 transferred upon passing through an absorbent wetted wall column (Puxty, et al., 2010). The overall schematic diagram of the procedures used by the author is as shown in figure 2.2. In the said procedures, temperature is kept low, ranging from 5˚C to 20˚C at CO2 partial pressure range of 0 to 20 kPa which is different from the usual method of analyzing the loading capacities of alkanolamines which are held at temperatures from 40˚C to 80˚C. Results showed relationship of absorption flux as a function of CO2 loading, temperature and CO2 partial pressure of both solvents and comparison of the values. The end concluded that in order for MEA can absorb CO2 around 1.5 to 2 times than ammonia does. However, MEA will have to be kept at a temperature not lower than 40˚C, whereas ammonia could be used at temperatures as ambient as 20˚C. But in order to make up for the decrease in reactivity with the lowering of temperature, a larger contact area by enlarging the dimensions of the absorber column.

Figure 2.2 Schematic diagram of the procedures used by Puxty et al. (2010)in determining the load capacities of ammonia and MEA

In addition to the problems that may yet be encountered in using ammonia to replace alkanolamines would be the energy requirement for the compressor for refrigeration and the fouling of the stripper at temperatures below 50˚F(Mathias, Reddy, & O'Connell, 2009). Mathias et al. (2009) pointed that an increase in pressure is one way to physically reduce the energy needed for compression.

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For the regeneration of ammonia, Yeh et al. (2005) showed and stressed that the reaction mechanisms involved during the dissociation of ammonium bicarbonates to CO2 and H2O have the lowest enthalpy. In addition to that, the exhibited release of CO2 as shown in the said author’s results accounts to 60% to that of the total CO2 originally absorbed. There also stated a precaution procedure in handling absorbed gases, where cold water (at 4˚C) is mixed with the laden absorbent to avoid the evolution of gases before sealing. Having defined other factors to be taken in account for the study of ammonia absorption, Yeh and his colleagues’ paper may serve a good introduction. Details about the theoretical perspectives obtained will be discussed in the next chapter.

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Chapter 3: Theoretical Framework

3.1 Chemical Properties of Ammonia

Ammonia (NH3) is a weak alkaline inorganic compound (Qin, Wang, Hartono, Svendsen, & Chen, 2010) consisting of one nitrogen atom bonded to three atoms of hydrogen. Two free electrons on the nitrogen atom allow this compound to attain a trigonal pyramidal structure.

The physical properties of ammonia recorded in Perry’s Chemical Engineering Handbook (Green & Perry, 2008) are summarized in table 3.1. There, it can be seen that ammonia attains a specific gravity of 0.817 at -79˚C while the specific gravity if 0.5971 at ambient temperature. Boiling point is at -33.4˚C at atmospheric pressure which therefore classifies ammonia as a highly volatile compound. To retain its liquid form, ammonia will have to be mixed with solvents with lesser volatility while vapour pressure contributes to the compression of molecules into liquid form as did Rivera-Tinoco et al. (2010).

Table 3.1 Physical properties of ammonia (NH3) obtained from Perry’s Chemical Engineering Handbook

formula weight 17.03refractive index 1.325 (lq.)

specific gravity 0.817−79°

  0.5971 (A)melting point (˚C) −77.7

boiling point (˚C) −33.4solubility in 100 parts:

cold water 89.90°

hot water 7.496°

other solvents 14.820°

Since low pressure drops are expected upon the entry of the CO2 gas into the reactor, vapour pressures much lower than 1atm must be achieve. Furthermore, since ammonia is less likely to saturate given the operating temperature (20˚C) which is still near ambient, maintaining ammonia in its liquid form will once again depend on the partial pressure the incoming flue gas exerts. The following vapour pressures of 1 mmHg to 760 mmHg and their corresponding temperatures are summarized in table 3.2 as obtained from the previous source.

Table 3.2 Vapor pressure of ammonia (NH3) and corresponding temperatureas obtained from Perry’s Chemical Engineering Handbook

Pressure, mmHg Temperature, °C1 −109.1

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5 −97.510 −91.920 −85.840 −79.260 −74.3

100 −68.4

200 −57.0

400 −45.4760 −33.6

3.2 Reactions Involved in Ammonia Decarbonization

Several journals have stated the reaction mechanisms involved in vapour-liquid equilibrium in literature. Darde et al. (2009) listed down the equilibrium reactions that were observed in a CO2 –H2O-NH3 during the absorption process. Among the reactions were the following as shown in table 3.1:

Table 3.3 List of equilibrium reactions involved in ammonia absorption

Speciation equilibria

N H 4 (aq )+ H 2O ↔ NH 4+¿+OH−¿¿ ¿

(1) CO2 (aq )+H 2O ( l )↔ HCO3−¿+H +¿ ¿¿

(2)

HCO3−¿ ↔CO3

2−¿+H +¿¿¿ ¿(3) H 2 O (l ) ↔OH−¿+H+¿¿ ¿

(4)

NH 3 ( aq )+HCO3−¿ ↔ NH2 COO−¿+H2O ¿ ¿

(5)

Vapor-liquid equilibriaCO2(g)↔ CO2(aq) (6) NH 3(g)↔ NH3(aq) (7)

H 2 O(g)↔ H 2O(l) (8)

Liquid-solid equilibria

NH 4+¿+HCO3

−¿↔ NH4

HCO3(s) ¿¿

(9) NH 4+¿+NH2 COO−¿↔ NH2 COON H 4(s )¿ ¿ (10)

2 NH 4+¿+CO3

2−¿+H 2O ↔ (NH 4)2 CO3∙H 2O (s )¿ ¿ (11) H 2 O(l)↔ H 2 O(s) (12)

4 NH 4+¿+CO3

2−¿+2 HCO3−¿↔¿ ¿¿

( NH 4 )2 CO3 ∙ 2NH 4 HCO3(s) (13)

The author noted that among those equilibrium reactions, five of them include the formation of solids namely ammonia bicarbonate (NH4HCO3), ammonia carbonate ((NH4)2CO3·H2O), ammonia carbamate (NH2COONH4), sesqui-carbonate ((NH4)2CO3·2NH4HCO3) and frozen water. The capability of forming these solids is something to be considered when designing since as Yeh(2005) says, this could build up on walls and eventually clogging pipes at prolonged accumulation.

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Aside from the formation of solid crystals, reactions under the liquid-solid equilibria show that the left side is consisted of binary to ternary reactants of heterogenous gas liquid mixtures. There, it can be seen that Le Chatelier’s principle may apply, in which states that application of pressure at the side containing more reactants may shift the reaction into forming a more compressed product (Maron & Lando, 1974). Hence, pressure plays a significant role optimizing the absorption of CO2 with ammonia.

3.3 NH3-CO2 –H2O Equilibrium Diagram

Since aqueous NH3 form crystals with CO2, factors such that the composition of three compounds must be considered in order to facilitate the flow of gases while controlling the amount of crystals while in contact. To give a fundamental introduction of the appearance of the three liquid diagram, figure 3.1 is as presented by Thomsen’s Extended UNIQUAC model in comparison to Jänecke’s (1917) findings.

Figure 3.1 Ternary diagram of NH3-CO2 –H2O system at 40˚C and 1 baras presented in UNIQUAC model

The solid-liquid ternary diagram is a Type II: Binary Compound Formation in terms of Maron and Lando’s (1974) classification. The blue lines represent tie lines of which systems compositions enable the precipitation of solids indicated while the black line is that solely for the formation of hydrated ammonium carbonate. However, this may not be a reliable basis for determining the equilibrium systems at 20˚C which has yet to be analyzed.

3.4 Absorption

Absorption is defined as the introduction of inert gas into solvent wherein which the former will be soluble (McCabe, Smith, & Harriot, 2005). McCabe (McCabe, et al., 2005) mentioned that the principle of absorption has been used in obtaining high concentrations of gas solute and the remaining solvent maybe discarded and reused. The author further added that the opposite of such operation is known as stripping or desorption wherein there involved the counter flow of an inert gas upon contact with solute laden absorbent.

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Since the thesis only covers the absorption capacities of different ammonia concentrations, the focus will be on mass transfer and physiochemical properties.

3.4.1 Material balance

For any reactor used in absorption, the material balance is as follows:

La xa+V b y b=Lb xb+V a ya (McCabe, et al., 2005)

where L and V represent the molal flow rates, x and y represent the mol ratios of solute in liquid and gas phase respectively. Subscripts a and b indicate the input and output positions respectively.

3.4.2 Limiting Gas-Liquid Ratio

When operating the absorption column, it is important to know the limiting gas-liquid ratio (L/V) to ensure that the process is done efficiently and economically. Based on findings by Qiu et al. (2010), the overall volumetric mass transfer coefficient with respect to gas-liquid ratio is as follows:

Figure 3.2 Overall volumetric mass transfer coefficient vs.gas-liquid ratio (Qiu, et al., 2010)

It can be seen clearly that the increase in overall volumetric mass transfer was due to the increase in solvent which is the 10% (v/v) aqueous ammonia. With the liquid-gas ratio at 0.0089, the overall volumetric mass flow reaches its highest (Qiu, et al., 2010). However, the line seems to deflect horizontally as it goes beyond which indicates that further increase in solvent’s molal volumetric rate will not result into any significant increase in absorption efficiency. Therefore in this research, gas-liquid ration to be observed will be at 0.007 for all concentrations.

3.4.3 Multicomponent Absorption

Since combustion of fuels such as coal are not often complete, there will be components such as CO2, CO, O2, H2, N2 and SO2. Although it is not yet certain which of the gases except nitrogen shall be absorbed, the material balance for multicomponent absorption is given by:

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V ( yB ,b− y B, a )=L(xB, b¿ −xB ,a) (McCabe, et al., 2005)

where subscript B represents component B of the system, a and b represent the input and output positions respectively. yB and yA is the mol fraction of component B in vapour phase and liquid phase respectively. xB

* is the mol fraction of solute in equilibrium with the liquid phase.

3.5 Wetted-Wall Column

Simple laboratory settings for the determination of CO2 of absorption of different solvents involve the use of wetted-wall columns (WWC) as reactors (Liu, Wang, Zhao, Tong, & Chen, 2009; Puxty, et al., 2010). Wetted-wall columns simulate packed tower reactors such that both involve the counter flow of two different fluids (Puxty, et al., 2010). However the difference is the liquid inlet that is made to flow through a smaller cylinder which is the column, bound by an outer metal jacket. Liu et al. (2009) this instrument is first used by Mshewa (1995), and was since then commonly used by other researches involving the test of absorption.

One of the most recent studies conducted by Qian (2009), using the modified wetted-wall column made of 1mm spaced steel tube annulus column and 23mm spaced annular jacket (where water bath circulates) exhibits the liquid film thickness of N-methyldiethanolamine given by this equation:

ld , mod=( QL/ t c

+π R2

π )12

−R

Where Q is the volumetric flow rate of the solvent, L is the length of the column, t c is the contact time and R is the radius of the inner of the column annulus. This equation may prove crucial in determining the limiting factors when operating the column since increase in thickness (as related to the mass) of the solvent may dilute the solute gas which is to be avoided since it makes stripping of CO2 gas difficult (McCabe, et al., 2005). However, that is only to approximate the workable design since that equation is applicable when no CO2 is yet loaded and when operation is done at atmospheric pressure (Qian & Guo, 2009). Hence, say the wetted-wall column used by Puxty et al. (dimensions for for height and diameter are 0.0821m and 0.0127m respectively) will be converted to one such like Qian’s, while maintaining film thickness of 1.15×10-4, the volumetric flow rate should be at 0.38 mL/s. Calculation is shown in the appendix A.1.

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Chapter 4: Materials and Methodology

4.1 Materials

Carbon dioxide source to be used in this thesis will be from the flue gas produced from the combustion of Semirara industrial grade coal. Absorption of flue gas from the combustion of 10g sample of coal shall be tested upon 10 g samples of aqueous ammonia solutions of different concentrations: 0.1M, 0.2M, 0.3M, 0.4M, 0.5M and 0.6M. Reactor model shall be based upon Qian’s (2009) model where dimensions applied will be the same as that of Puxty’s (2010) wetted-wall column. The following dimensions are as follows: annular metal column with 1mm space and inner diameter of 1.27 cm and outer diameter of 1.37 cm for the plastic tube (assuming metal sheets). The height of the column remains stationary at 8.21 cm. Annular Pyrex glass jacket with an internal diameter of 2.54 cm and an outer diameter of 5.04 cm including inlet and outlet for the water bath. Aperture for the gas inlet however will be enlarged to 10mm for a greater pressure drop at the end of combustion. Steel flanges that seal the reactor will have indentions where thermometer can be placed for the monitoring of temperature. Also, another glass enclosure is provided to protect the mechanism and allow the monitoring of process. In order to show the basis of design, figure 3.2 is provided. Specific materials used as described below the figure may not necessarily apply in actual fabrication for this procedure.

Figure 4.1 Qian’s wetted-wall column design

Lastly, it will require gas analyzing instruments such as gas spectrometers to analyze the content of gases, before and after the absorption is to be done.

4.2 Experimental Setup

For quick reference, the diagram setup is illustrated in figure 4.2.

Figure 4.2 Experimental setup

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This is derived from Puxty’s et al. (2010) experimental setup however there are a few modifications since combusted coal fuel gas is used. At the heat source, Semirara coal is combusted with theoretical air. Since a large amount of heat is expected to evolve, flue has is stored temporarily in flask submerged in circulating water bath. Once cooled, gas will be introduced to the saturator (1/8” stainless steel coil) maintaining a CO2 partial pressure of 20 kPa. Meanwhile, 10 grams of aqueous ammonia sample will be placed in water bath while being circulated with a volumetric rate of 0.83 mL/s through the annular space of the wetted-wall column by the use of pumping force. As for the outer annulus, cold water of 20˚C will be circulated through the annular space of the outer glass jacket.

4.3 Experimental Procedures

The following procedures to be done in the experiment are presented in chronological order.

4.3.1 Combustion of Semirara Coal

As mentioned in the earlier sections, before the absorption of aqueous ammonia will be tested, the composition of the flue gas from combusted Semirara coal (10 gram sample) must be determined separately from the experimental set up. To ensure the accuracy of data, five trials will be held to obtain five records of the flue gas composition (CO2, CO, H2, H2O, O2, N2, SO2). Coal will be combusted such that only ashes remain and there added five minutes of heating after the solid fuels are no longer visible. As for the theoretical air to be introduced, computation will be based upon the data provided by the Semirara Mining Corporation with the assumption that fuel undergoes complete combustion. After the analysis with gas spectrophotometer, the average of five records for each gas composition will be computed for and used for theoretical calculation in material balance.

For the actual determination of absorption, another 10 gram sample will be combusted in the same manner as did the previous five trials. Flue gas will be temporarily stored inside a flask while being gradually cooled in a circulating water bath. Partial pressures of solute gas may be calculated theoretically with gas correlations to determine the control pressure to attain desired gas velocity.

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4.3.2 Preparation of Aqueous Ammonia Sample

For the variation of solvent absorbents, ammonia shall be diluted in water in the following molarities: 0.1M, 0.2M, 0.3M, 0.4M, 0.5M, and 0.6M. These will be loaded into the sample reservoir and pumped within the reactor. No carbon dioxide loading will be done beforehand.

While flue gases are left to cool, 10 g of aqueous ammonia sample will be first placed in water bath for five minutes until it comes to thermal equilibrium. Then liquid will be made to run 0.38mL/sec and will be indicated by an orifice meter.

4.3.3 Absorption Determination

While flow rate of solvent is maintained constant and the molarity increases, there should be an equivalent decrease in flow rate for the incoming flue gas. Gas flow rates for each corresponding molarities above will depend on the partial pressure of CO2 of the flue gas to be analyzed. The gas flow rate will be controlled with the pressure regulator.

Cooled flue gas will be made to pass through the saturator, then to the column counter-currently with the solvent sample to be tested. Unabsorbed flue gas composition will then pass through the condenser, conditioner and then be analyzed with the gas spectrometer until liquid and gas finally comes into equilibrium. Then the unabsorbed flue gas after the equilibrium will be recorded. For the next five molarities, another 10 g sample of coal will be loaded, combusted and cooled, and 10 g sample of solvent to be placed in the water bath to attain thermal equilibrium in preparation for another analysis.

Figure 4.3 Flowchart of procedures

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Appendix

A. Calculations

A.1 Approximation of flow rate of aqueous ammonia through the equation suggested by Qin (2010)

Q=¿ π ( (ld , mod+R )2−π R2 ) L

tc

Q=π [(1.15× 10−4+ 0.0127

2 )2

−π ( 0.01272 )

2]0.0821

1

Q=3.8 × 10−7 m3

s∨0.38

cm3

s

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B. Materials Safety Data Sheet

B.1 Ammonia

Description

Chemical name: Anhydrous Ammonia CAS registry number: 7664-417

Synonyms: Ammonia Formula: NH3

Chemical family: Inorganic Molecular weight: 17.03

Composition: 99~% Ammonia  

Physical Properties Hazard Description

Boiling point -33°C (-28°F) Not recognize by OSHA as a carcinogen.

Freezing point -78ºC (-108°F) Not listed in the National Toxicology Program annual report.

Flash point noneNot listed as a carcinogen by the International Agency for Research on Cancer.

Self-ignition temperature

651 ºC (1204ºF) catalyzed by iron

Conditions to Avoid

850 ºC (1562ºF) uncatalyzed

Mixing ammonia with halogens, strong oxidizers, strong mineral acids, NitricAcid, Fluorine, Nitrogen Oxide, etc…Flammable limits in

airLEL 15%

UEL 28% Explosive combustion result with mixture of air and the following: hydrocarbons, Ethanol and Silver Nitrate, Chlorine, etc….

Specific gravity (water=1)

0.682 @ 4°C (39°F)

Vapor/air (air=1) 0.596 @ 0°C (32°F) Reaction with Silver Chloride, Silver Oxide, Bromine, Iodine, Gold, Mercury,Tellurium Halides, etc. form explosive products.Vapor pressure 10 atm @ 25.7ºC

Solubility in water89.9 g/100cc @ 0ºC Ammonia may form hazardous reactions with the following:

Silver, Acetaldehyde, Acrolein, Boron, Halogens, Perchlorate, Chloric Acid, Chloric Monoxide, Chlorites, Nitrogen Tetroxide, Tin, Sulfur, etc….

7.4 g/100cc @100ºC

Surface tension 23.4 Dynes/cm @ 11.1ºC

Percent volatile 100%Ammonia can corrode galvanized surfaces, copper, brass, bronze, aluminum alloys, mercury, gold, and silver.Appearance and

odorColorless gas/liquid and pungent odor

Reactivity

Stable at room temperature

Hazardous Decompositions

Will react exothermicall with acids and water

Hydrogen and nitrogen gases above 450ºC (842ºF) can form high heat. Reaction with metals may help dissipate heat

Exposure limits

Federal OSHA PEL 50 ppm 8 hour (TWA)

NIOSH REL / ACGIH TLV 25 ppm 10 hour (TWA)

  35 ppm 15 min. (STEL)

IDLH 300 ppm  

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Emergency Treatment

Hazard/Symptoms Preventive Measures Fire Extinguishing/First Aid

Lacrimation, edema or blindness to the eye.

Wear goggles when handling chemicalFlush eyes with abundant amount of water for 15 minutes with eyelids held away from each other, exposing the eyeball.

Irritation, corrosive burns, blister formation on skin. Caustic burn may result from tissues freezing upon contact.

Wear personal protective equipments (PPE) at all times until after the cleaning and keeping of equipments.

Remove contaminated clothes and gears and flush inflamed skin with abundant amounts of water for 15 minutes. Carefully remove contaminated attire in case of material frozen to skin that might cause further abrasions. Do not apply any salves or ointment.

Acute irritation of respiratory tract, bronchospasm, edema or respiratory arrest upon inhalation.

Wear masks. Peform transfer under the hood where vapors are drawn away.

Move to area with fresh air. Apply oxygen or artificial respiration if unconscious.

Lung irritation, pulmonary edema and other symptoms similarly occuring in inahalation may occur upon ingestion.

Avoid eating, drinking or smoking inside the lab

Give plenty of water or citrus juice to drink if conscious. Do not induce vomiting.

Formation of explosive compounds and/or reactions as mentioned in Conditions to Avoind and Hazardous Decompositions

Properly label container. Keep away from heat and distance it from other chemicals.

Wear protective clothing and pressure postive SCBA. Cool fire exposed containers with water spray while upwind

Notes:

*There are no chronic effects.

*Spasms, inflammation or edemas due to extreme exposure may cause death.

*To physician, lung injury and pulmonary edema may not appear immediately. Therefore supportive treatment and ventilation should be provided to make sure.

*FOR ALL EXPOSURES, SEEK MEDICAL ATTENTION IMMEDIATELY.

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Spillage Waste Disposal Storage and Handling Labeling/NFPA

While wearing protective attire and respiratory protection, and spray water downwind. Isolate diluted run-offs from sewers and bodies of water. CAUTION: adding water directly to liquid spills increase volatility of ammonia, thus may result to increase in exposure of environment

Ammonia may be used for manufacturing fertilizers but should be kept from entering bodies of water. Disposal should comply with environmental legislations.

Considering ammonia as a hazardous material, it should be kept in a cool, well-ventilated area with container sealed tightly.

3 - Health, 1 - Flammability, 0 - Reactivity, H- Personal Protection

*Information for materials safety data sheet is obtained from Allied Deviation

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B.2 Lignite or Sub-bituminous Coal Fly Ash

Description

Product/Chemical name: Coal Fly Ash CAS registry number: 68131-74-8Synonyms: Ashes(residues),coal ash, fly ash

Physical Properties Health hazards

Boiling point > 1000° C Exposure route: Inhalation

Freezing point none Skin Contact

Flash point none Eye ContactSelf-ignition temperature none Ingestion

Specific gravity 2.2-2.8 Note:Crystalline Silica is classified by

IARC as human carcinogen.

Vapor density not measurable

Vapor pressure Not measurable Personal Protective Equipment

Solubility in water < 5%Respiratory Protection: Appropriate mask

SolidLight tan or beige

powder Eye Protection: Goggles

Reactivity Reacts with water Skin protection: Gloves, shoes and

    protective clothing

Emergency Treatment

Hazard/Symptoms Preventive Measures First Aid Inhalation Wear mask. Move person to fresh air.

 

Contact emergency medical support if the person is not breathing.

Eye Contact Wear google in handling coals.Rinse thoroughly with water at an eye station. Do not rub. Seek medical attention as soon as possible. 

Skin ContactWear appropriate gloves Wash contaminated skin

immediately with water and soap. Seek medical attention for skin irritation.

and proper clothing.

 Ingestion Avoid eating in the working area. Do not induce vomiting, but drink

plenty of water.

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Waste Disposal Storage and HandlingAmmonia may be used for manufacturing fertilizers but should be kept from entering bodies of water. Disposal should comply with environmental legislations.

Avoid accidental release. Store dry and away from water. Dispose of containers in an approved landfill or incinerator.

*Information for materials safety data sheet is obtained from Lafarge North America (2002)

34