DESALINATION OF SEA WATER

CHY1001 CHEMISTRY PROJECT FIRST SEMESTER Batch :- BME08

Submitted to Prof. Akella Shivaramakrishna

2

MEMBERS OF THE GROUP INVOLVED:BATCH REGISTRATION NO. NAMEBME08 16BME0357 ABHISHEK SAVANIBME08 16BME0368 ABHINAV AGRAWALBME08 16BME0653 MAYANK AGRAWALBME08 16BME0723 RISHAVDEB GHOSHBME08 16BME0798 NEELANJYAN DUTTABME08 16BME0896 NEEL NADKARNIBME08 16BME0922 UJJWAL MANI SHUKLABME08 16BME0923 SRIVATSAN C.BME08 16BME0978 SHOMI DEEP MAULIKBME08 16BME0987 JEFFREY THOMSON

STANLY

3

INTRODUCTION : Significance Desalination process helps

remove minerals from sea water to make it consumable.

75% of the Earth’s surface is covered by water

97.5% of that water is oceans Only 1% is available for drinking Desalination is particularly

relevant in dry countries such as Australia, which traditionally have relied on collecting rainfall behind dams for water.

1.5 billion people lack ready access to drinking water

4

The Primary process of desalinating sea-water to obtain potable water

evaporator

condensermembrane

evaporator

condensersaltwater

vapour

brine

vapour

waste tank

clean water

water

Water

drinking water

brine

brine

5

VARIOUS PROCESSES AVAILABLE FOR DESALINATION :

REVERSE OSMOSIS Distillation Multi-stage Flash Multi-Effect Distillation Electro Dialysis

6

1. REVERSE OSMOSIS This is an example of

membrane desalination process.Saltwater is forced through

membrane sheets at high pressuresSemi-Permeable Membrane sheets

are designed to catch salt ionsProcess produces clean water and

brine

In case of Reverse Osmosis, Saltwater is forced through a membrane at 600 to 1000 psi to overcome the vapor pressure of the saline water.

LIMITATIONS

BACK

Detailed Study of Reverse Osmosis:- Reverse osmosis or hyper

filtration is actually a way of filtering water to reduce particles to a molecular level. It significantly decreases the salts and other potential impurities in the water, resulting in a high quality and great-tasting product.

Reverse osmosis is comparatively newer method of treating water and purifying it but has emerged to be one of the best.

Reverse osmosis (RO) is a water purification technology that uses a semi-permeable membrane to remove ions, molecules, and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property, that is driven by chemical potential differences of the solvent, a thermodynamic parameter. Reverse osmosis can remove many types of dissolved and suspended species from water, including bacteria, and is used in both industrial processes and the production of potable water.

7

What is a “Semi-permeable Membrane”? A semipermeable membrane, also termed a selectively permeable membrane (or a

differentially or partially permeable membrane), is a type of biological or synthetic, polymeric membrane that will allow certain molecules or ions to pass through it by diffusion—or occasionally by more specialized processes of facilitated diffusion, passive transport or active transport. The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Depending on the membrane and the solute, permeability may depend on solute size, solubility, properties, or chemistry.

An example of a biological semi-permeable membrane is the lipid bilayer, on which is based the plasma membrane that surrounds all biological cells. A group of phospholipids(consisting of a phosphate head and two fatty acid tails) arranged into a double-layer, the phospholipid bilayer is a semipermeable membrane that is very specific in its permeability. The hydrophilic phosphate heads are in the outside layer and exposed to the water content outside and within the cell. The hydrophobic tails are the layer hidden in the inside of the membrane. The phospholipid bilayer is the most permeable to small, uncharged solutes. Protein channels float through the phospholipids, and, collectively, this model is known as the fluid mosaic model.

8

Semi-permeable Membrane:- The diffusion of water through a

selectively permeable membrane is called osmosis. This allows only certain particles to go through including water and leaving behind the solutes including salt and other contaminants. In the process of reverse osmosis, thin film composite membranes (TFC or TFM) are used. These are semipermeable membranes manufactured principally for use in water purification or desalination systems.

9

Steps Involved in Reverse Osmosis 1st Step - Removal of sediments from the water. In this step all the sediments

like clay, silt and stones are removed from the water. For this, a 5-micron filter is used. The sediments are filtered in order to make sure that no damage is done to the membrane. The micron filter does not let these particles pass by and thus they are suspended. 

2nd Step - The Reverse osmosis treatment is the usage of carbon filter. The carbon filter is used to remove the chlorine and other harmful chemicals that enter the water sources. The chemicals can be harmful to human health and thus it is necessary to remove them.

3rd Step - Reverse osmosis treatment generally focuses on passing the water from a dense and compacted carbon filter. The water that we get may have some unpleasant characteristics and this third step helps in the removal of all such characteristics. All the contaminants left in the water are removed at this stage and water becomes almost clean.

4th Step - Water passes through the membrane and all the heavy metals present in the water are removed. Along with the metals, radioactive metals too are removed. In this step, the impurities are drained out of the reverse osmosis system and clean water is separated.

10

5th Step - The whole process of reverse osmosis is post filtration. This may be the last step but is the most important of all. In this last stage, the bacteria, chlorine, and bad odour are removed from water. After water passes from this stage, it comes out of the faucet and is perfect for consumption.

11

Limitations of R.O. Process : Because of low back pressure in household systems; about 85% of the

water entering the plant is not recovered as clean. Due to the selectively permeable membrane in use, the water is

mostly demineralised, i.e. ,the water is devoid of important minerals. Depending upon the desired product, either the solvent or solute

stream of reverse osmosis will be waste.

12

BACK

R.O. Plant in Barcelona, Spain

13

2.Distillation Distillation is a process

of separating the component substances from a liquid mixture by selective evaporation and condensation. 

In case the process exploits differences in the volatility of mixture's components.

Different types of Distillation Processes performed in laboratory:-• Simple distillation• Fractional Distillation• Steam Distillation • Vacuum Distillation• Short-path Distillation• Zone Distillation BACK

14

A New Approach for the Removal of Salts from Sea Water

Method of DesalinationSalt Water (RO Reject) + Hydrophilic directional solvents (Adepic Acid)

Heating thoroughly

Salt will come out of water dissolved mostly in the directional solvent(high

concentration)Water + Adepic acid mixture is without

salt cooling

Pure Water Adepic acid

Zero Water Wastage

R.O. Membrane(Thin Film Composite)

21

Energy Consumption of Seawater Desalination methods:- Energy consumption of seawater desalination has reached as low as 3

kWh/m3 including pre-filtering and ancillaries, similar to the energy consumption of other fresh water supplies transported over large distances but much higher than local fresh water supplies that use 0.2 kWh/m3 or less.

A minimum energy consumption for seawater desalination of around 1 kWh/m3 has been determined, excluding pre-filtering and intake/outfall pumping. Under 2 kWh/m3 has been achieved with Reverse Osmotic membrane technology, leaving limited scope for further energy reductions.

Supplying all US domestic water by desalination would increase energy consumption by around 10%, about the amount of energy used by domestic refrigerators. Domestic consumption is a relatively small fraction of the total water usage.

22

Desalination Method

Multi-stage Flash (MSF)

Multi-effect Distillation

Simple Distillation

Reverse Osmosis

Electrical energy (kWh/m3)

4–6 1.5–2.5 7–12 3–5.5

Thermal energy (kWh/m3) 50–110 60–110 None None

Electrical equivalent of thermal energy (kWh/m3)

9.5–19.5 5–8.5 None None

Total equivalent electrical energy (kWh/m3)

13.5–25.5 6.5–11 7–12 3–5.5

23

Cogeneration Cogeneration is generating excess heat and electricity generation

from a single process. Cogeneration can provide usable heat for desalination in an integrated, or "dual-purpose", facility where a power plant provides the energy for desalination. Alternatively, the facility's energy production may be dedicated to the production of potable water (a stand-alone facility), or excess energy may be produced and incorporated into the energy grid. Cogeneration takes various forms, and theoretically any form of energy production could be used. However, the majority of current and planned cogeneration desalination plants use either fossil fuels or nuclear power as their source of energy. Most plants are located in the Middle East or North Africa, which use their petroleum resources to offset limited water resources. The advantage of dual-purpose facilities is they can be more efficient in energy consumption, thus making desalination more viable.

24

The current trend in dual-purpose facilities is hybrid configurations, in which the permeate from reverse osmosis desalination is mixed with distillate from thermal desalination. Basically, two or more desalination processes are combined along with power production. Such facilities have been implemented in Saudi Arabia at Jeddah and Yanbu.

A typical Super-carrier in the US military uses nuclear power to desalinate 400,000 US gallons (1,500,000 l; 330,000 imp gal) of water per day.

The Shevchenko BN350, a nuclear-heated desalination unit

25

Economics Costs of desalinating sea water

(infrastructure, energy, and maintenance) are generally higher than fresh water from rivers or groundwater or water recycling or conservation, but alternatives are not always available. Desalination costs in 2013 ranged from US$0.45 to $1.00/cubic metre ($US2 to 4/kgal). (1 cubic meter is about 264 gallons.) More than half of the cost comes directly from energy cost, and since energy prices are very volatile, actual costs can vary substantially.

The cost of untreated fresh water in the developing world can reach US$5/cubic metre.

Factors that determine the costs for desalination include capacity and type of facility, location, feed water, labour, energy, financing and concentrate disposal. Desalination plants control pressure, temperature and brine concentrations to optimize efficiency. Nuclear powered desalination might be economical on a large scale.

Area/Country Desalinated Water Cost US$/person/day

USA 0.38

Europe 0.19

Africa 0.06

UN recommended 0.05

Israel 0.40

Singapore 0.49

26

Desalination WorldwidePlant Name/Location Capacity

(mgd)Tampa Bay Desalination Plant, USA 25.0

Point Lisas, Trinidad 28.8Almeria, Spain 13.2Las Palmas – Telde 9.2Larnaca, Cyprus 14.2Muricia, Spain Design-Bid-Build 17.2

The Bay of Palma/Palma de Mallorca

16.6

Dhekelia, Cyprus 10.6Marbella – Malaga, Spain 14.5

27

Large R.O. Seawater Desalination Plants In Design/ConstructionPlant Name/Location Capacity Installed/Avg. (mgd)Fujairah, UAE 45Carboneras – Almeria, Spain 32Ashkelon, Israel 35.4 expandable to 75Singapore 36Cartagena – Mauricia, Spain 17.2Campo de Cartagena – Mauricia, Spain 37

Almeria, Spain 13.2Alicante, Spain 13.2

28

Bibliography : Class notes Book(s) : Engineering Chemistry

Jain & Jain O.G. Palanna

en.wikipedia.org Google images. Central Library, VIT University-

Vellore