From fossil to biogenic feedstock – exploring different technology … · sults also show that...

ECEEE 2012 SUMMER STUDY on EnERgY EffiCiEnCY in inDUSTRY 269

From fossil to biogenic feedstock – exploring different technology pathways for a Swedish chemical cluster

Johanna JönssonSP Technical Research Institute of SwedenEnergy Technology, Section for Systems AnalysisGibraltargatan 35SE-400 22 Gö[email protected]

Roman HacklChalmers University of Technology, Energy and Environment, Heat and Power TechnologyKemivägen 4SE-412 96 Gö[email protected]

Simon HarveyChalmers University of Technology, Energy and Environment, Heat and Power TechnologyKemivägen 4SE-412 96 Gö[email protected]

Christian JensenUniversity of Gothenburg, School of Business, Economics and Law, Business Administration, Management and OrganizationBox 600SE-405 30 Gö[email protected]

Anders SandoffUniversity of Gothenburg, School of Business, Economics and Law, Business Administration, Industrial and Financial ManagementBox 600SE-405 30 Gö[email protected]

Keywordsenergy efficiency investments, waste heat, strategy, biomass, vision-driven multi-party cooperation, technology pathways

AbstractThis paper presents a case study of the chemical cluster in Ste-nungsund, Sweden. The cluster is Sweden’s largest agglomera-tion of its kind and consists of five companies producing a va-riety of chemical products. For the cluster, different options for enhanced energy efficiency and converting to biogenic feed-stock are investigated. Based on these options, nine different technology pathways are defined – representing different ways to fully or partly transform the cluster into an energy efficient biorefinery. For the pathways an impact analysis is made in which the pathways are analysed and discussed from different perspectives. The results show that up to 120 MW of heat can be saved if the plants were to implement extensive heat integra-tion measures. This is equal to ~100 % of the heat currently supplied by boilers based on purchased fuels. With moderate enhancement of the heat integration, roughly half of this poten-tial can be reached. In the fossil feedstock is to be replaced with biogenic feedstock the feedstock demand is extensive, however, the exact amount and type of feedstock depends on the tech-nology chosen, degree of heat integration and on whether full or partial substitution is to be achieved. Full substitution of the fossil ethylene demand by ethylene based on imported bioetha-nol would for example demand ~1,230 kt-bioethanol/yr. If the ethanol for the ethanol-to-ethylene process were to be pro-duced on site (based on lignocellulosic biomass), 4,725 kt-dry biomass/yr of forest biomass would be required (more than the biomass demand for four large pulp and paper mills). The re-sults also show that the scenarios for enhanced heat integration

and introduction of biogenic feedstock, to different extents, are interdependent. Furthermore, one important finding from the impact analysis is that regardless of which pathway the cluster wants to travel in their journey towards sustainable chemistry, collaboration is a key issue.

IntroductionGlobal chemicals and manufacturing industries have been of great importance for our modern industrial society, develop-ing and producing the key chemicals, materials, medicines and other products. Seen to the global market, Europe stands for ~20 % of the total production of chemical products. The production of chemicals and chemical products is mainly based on fossil feedstock and ~5 %–10 % of the world’s petro-leum output is dedicated to chemicals manufacturing (mainly feedstock). In the climate-conscious Europe of today, with in-creasing energy prices, the threat of depletion of fossil fuels and the introduction of new policy instruments, not least for reduction of greenhouse gas emissions, large changeovers are to be expected for the European industry’s energy and production systems in the near future. Already today, the European chemical industry is investigating alternative ways of switching to bio-based feedstock and to recycle and reuse waste materials in order to forestall these changes and main-tain its competitiveness – thereby gradually transforming the chemical plants into so-called biorefineries. When planning and implementing large changes in the energy and produc-tion systems – such as the switch from fossil to biogenic feed-stock – it is important to look at the industry as an integrated system as opposed to a collection of independent sites. This way, integration opportunities and synergies can be identi-

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270 ECEEE 2012 SUMMER STUDY on EnERgY EffiCiEnCY in inDUSTRY

2. SUSTAInABLE PRODUCTIOn DESIGn, SUPPLY CHAIn InITIATIVES

fied, improving the overall efficiency and possibly enhancing the transformation.

The chemical cluster in Stenungsund is Sweden’s largest agglomeration of its kind. The cluster consists of five differ-ent companies producing a variety of chemical products. The cluster is a major fossil fuel consumer accounting for ~5 % of Sweden’s total fossil fuel usage (mainly feedstock) and cur-rently also a major emitter of fossil CO2. However, this could be about to change. In 2011 the companies within the cluster adopted a joint vision: “Sustainable Chemistry 2030”. The vi-sion states that, by 2030, the cluster should be based mainly on biogenic feedstock and renewable energy. Achieving this vision requires well-developed cooperation between different actors, implementation of new technologies and efficient technical system solutions (here called technology pathways), and that a number of non-technical barriers are overcome. As discussed by Boons and Baas (1997), industrial ecology objectives span across company boundaries and thus demand coordination of the activities of several economic actors, which often consti-tutes a complicating factor. Thus, it is important to investigate the technical as well as organisational dependency relations between the organisations.

ScopeThis paper presents a case study of the chemical cluster in Ste-nungsund, Sweden. For the cluster nine different technology pathways are defined. The technology pathways are combina-tions of different levels of heat integration and new technolo-gies for substituting fossil feedstock with biogenic feedstock. Thus, the pathways all represents different ways for the cluster to fully or partly transform into an energy efficient biorefin-ery, producing chemical products based on biogenic feedstock. The paper also explores and discusses the suggested technology pathways from a business and organisational perspective and analyses to what extents the technology pathways demand co-operation between the companies in the cluster.

DeScrIptIon of the cluSterThe chemical cluster in Stenungsund consists of five different companies, AGA Gas AB, Akzo Nobel Sverige AB, Borealis AB, INEOS Sverige AB and Perstorp Oxo AB, producing a variety of chemical products such as polyvinyl chloride (PVC), polyethylene (PE), ethylene, amines, surfactants, oxygen/ni-trogen and plasticisers. An overview of the five companies in the cluster and their main feedstocks and products are given in Figure 1. As can be seen in the figure, the cluster currently is a major fossil feedstock consumer as well as a major emitter of CO2 – the cluster’s cracker plant alone accounts for 1.2 % of Sweden’s emissions of fossil CO2. The heart of the cluster is the Borealis steam cracker plant which supplies the other plants with ethylene, fuel gas, propylene and hydrogen. The cracker capacity is, however, not sufficient and ethylene is also imported (~30 %).

A fact that characterizes the Stenungsund cluster, compared to most petrochemical clusters, is that the companies do not compete with each other. The constituent process plants are profiled towards different business segments, which facilitates cooperation and knowledge transfer. They are, however, all parts of larger international company groups which compete in some market segments.

The cluster in Stenungsund is by international standards rather small. However, the cluster is located very strategi-cally within reach of Sweden’s largest industrial harbour (on a freight volume basis), the natural gas grid (to which increas-ing amounts of biogas are fed), the oil refineries in Lysekil and Göteborg (producing the majority of Sweden’s transport fuels) and local district heating grids (to which parts of the plants excess heat is delivered). Furthermore, both pulp and paper in-dustries and heat and power producers having ongoing projects regarding biomass gasification and new biomaterials are lo-cated within the cluster’s reach. This means that not only are the infrastructural pre-requisites in place for a transformation towards a more “green” chemical industry in Stenungsund, fur-thermore the transformation could also be enhanced thorough knowledge exchange and networks with other industry sectors (the forestry, pulp and paper and heat and power sectors) inter-ested in the same new technologies.

DeScrIptIon of the vISIon of SuStAInAble chemIStry In 2030In 2011 the companies within the cluster adopted a joint vi-sion: “Sustainable Chemistry 2030”. A detailed description of the aims of the vision is given in the left part of Figure 2. To be implemented fully, the vision requires well-developed coopera-tion between different actors, that new technologies and effi-cient technical system solutions are implemented (here called technology pathways), and that a number of non-technical barriers are overcome. The challenges related to realizing the vision are of three types: technical, organizational and business, see the right part of Figure 2.

If the cluster manages to realise the vision of a Sustainable Chemistry in 2030, it can take the lead in the European work with organizing and realising the challenge of increased heat integration and implementation of biogenic feedstock in the chemical industry. However, the cluster is also exposed to the risk of major loss of credibility for the companies involved if the work does not gather momentum and the vision is not achieved. Further, there is a “first-actor” advantage for estab-lishing operations within the new niche of thermoplastics and chemicals based on renewable feedstock. However, the Ste-nungsund cluster is not the only actor currently planning to establish itself within this niche. On a global level, for example, Braskem (one of the largest producers of thermoplastics in the world) has a vision to be world leading in sustainable chemistry by 2020 and a clearly set goal to be the largest producer of ther-moplastics based on renewable feedstock (Braskem, 2012a). Furthermore, Braskem is already producing biogenic ethylene based on sugarcane ethanol in their plant in Triunfo, Brasil (Braskem, 2012b; ChemicalsTechnology.com, 2012).

Inventory of options for enhanced energy efficiency and biogenic feedstockOne important building block in the work towards reaching the vision is efficiency. One way to increase energy efficiency is to use the excess heat from one plant to cover the heat demand of another (where it is possible), i.e. implement thermal process integration (Kemp, 2007; Klemeš et al., 1997). In this way, the primary heat demand can be reduced. Table 1 presents three different technology scenarios for energy efficiency in the clus-ter through different levels of heat integration. To realise the




vision the cluster also needs to substitute fossil feedstock with biogenic feedstock. As can be seen in Figure 1, one of the main feedstocks used within the cluster is ethylene, both imported and produced in the cracker plant. Thus, to achieve extensive use of renewable feedstocks within the cluster, the ethylene needs to be based on biogenic feedstock. Table 2 presents three different technology scenarios for how biogenic feedstock can be introduced in the cluster. The scenarios for heat integration and biogenic feedstock are presented more thoroughly in the following.

AchIevIng enhAnceD energy effIcIency through ImproveD heAt IntegrAtIonThe cluster’s current energy usage and inter-company energy transfers are presented in Figure 3. The fuels used in boilers are both internal fuels such as process off-gases and combusti-ble residues and external fuels. Currently, the cluster supplies ~90 GWh/yr of excess heat to the local district heating grid (SDHA, 2012). The amount of heat delivered is not limited by the magnitude of excess heat which the cluster could supply but by the heat demand in the district heating grid of the most

INEOS Sverige AB

Borealis ABCracker plant

AGA Gas AB

Perstorp Oxo ABImport terminal

Air

Oxygen

Nitrogen

Naphtha Ethane Butane Propane

Bioeth

anol

Natura

l

gas

Polyvinyl chlorideLiquor

AminesSurfactants

Ethylene

Polyethylene

District heating

District heatingRME

Speciality chemicals

Rapese

ed

oil Natura

l

gas

EthyleneFuel gas

HydrogenPropylene

Inter-‐company material flows Borealis AB

Polyethylene plant

Akzo Nobel Sverige AB

Figure 1. An overview of the chemical cluster in Stenungsund. For each company major inputs and outputs are presented (arrows), as are the material exchanges within the cluster. The nitrogen and oxygen produced by AGA Gas AB are used by the other plants in the cluster as well as exported.

Figure 2. The aims of the vision (left) and the three types of challenges for realising the vision (right). The right part of the figure is based on the information given by the participating companies (Kemiföretagen i Stenungsund, 2012), the left part is an interpretation made by the authors of this paper.

The aims of the vision Three types of challenges for realising the vision

By 2030 the companies in the cluster will: Produce sustainable products

Base their business on renewable feedstock and energy

Produce fuels for the transport sector from renewable feedstock

Use biogas, produced from local waste streams, both for energy and feedstock purposes

Export (more) heat for district heating purposes to an interconnected, regional district heating grid Use re-cycled plastics as feedstock for new products

The companies in the cluster will also contribute to:

A sustainable society

Create an internationally established researched centre for development of methods, products and fuels

An attractive local region, where people thrive and develop, and in which people want to both work and live

BusinessAdapting

existing business models to new

areas of business

Technology Implementing efficient

technical system solutions and adopting new

technologies

OrganisationOrganising for change and collaborative

work




nearby city, Stenungsund, which is rather small (population of ~10,000 in the densely built up area covered by the district heating grid).

In an industrial cluster, industrial plants have the oppor-tunity to make efficient use of common energy and transport infrastructure and/or reduce their total demand for external heating and cooling by exchanging excess heat via a common utility system. Using total site analysis, TSA (described by e.g. Raissi (1994); Klemeš, Dhole et al. (1997); Perry, Klemeš et al. (2008)), the potential for utility savings through implementa-tion of a common utility system has been investigated for both the cluster analysed in this paper and other petrochemical clus-ters (Hackl et al., 2011a; Matsuda et al., 2009; Stijepovic and Linke, 2011).

Hackl et al. (2011a) found that, theoretically, up to 125 MW of external utility savings can be achieved. In addition to this, a surplus of 16 MW of high pressure steam could theoretically be generated from excess process heat. Practical measures re-quired to achieve this savings potential are a circulating hot wa-ter system across the cluster utilising 116 MW of excess process heat and increased steam generation from excess process heat; 25 MW. However, 17 MW out of the 125 MW are not techni-cally possible to implement due to steam pressure restrictions in some heat exchangers. To fully realise the technical poten-tial would require rather extensive and complex changes to the companies’ energy systems such as investments in new equip-ment, changes in steam levels, establishment of common utility systems, redistribution of steam between the individual plants, increased steam generation from excess process heat, etc. In a further study by the same authors, Andersson et al. (2011), the changes were ranked based on feasibility of implementation. Rough cost estimations were also made.

Scenarios for heat integrationBased on the findings from the TSA-analysis made by Hackl et al. (2011) and the extended study by Andersson et al. (2011) three scenarios for heat integration were defined. These sce-narios are presented in Table 1. Figure 4 shows the exchanges of

hot water, steam and internal fuels between the different com-panies in the cluster if the moderate heat integration scenario presented in Table 1 is implemented. As can be seen in the figure, for most of the companies, increased total site energy efficiency implies increased dependency on other companies in the cluster through increased heat, steam and fuel exchanges. For AGA Gas, however increasing the internal heat exchange by rebuilding 2–4 heat exchangers can eliminate the need to purchase ~1MW steam from Akzo Nobel.

An intricate aspect of the heat integration scenarios is that since they are based on an increased level of heat exchange be-tween the companies, it is not necessarily the company making an investment to recover heat which benefits from the invest-ment. Instead it is the company which utilises the recovered heat to replace primary boiler heat which benefits. Thus it is a complex issue to allocate both investment costs and revenues from these investments between the involved companies.Even if the cluster increases the internal heat exchange there will still be substantial amounts of excess heat available which could be used for district heating purposes. The local district heating demand in Stenungsund is, however, already met by the cur-rent level of excess heat delivery. To further utilize the excess heat for district heating it would be necessary to connect the local Stenungsund grid to other nearby district heating grids, creating a regional district heating grid with a larger heat de-mand, e.g. the Kungälv grid and further south, the Göteborg grid. However, there are currently no on-going plans for such a regional district heating grid.

It should be noted that recovery of process heat through in-creased internal heat exchange also decreases the cooling de-mand. This is a very important issue and gives heat integration investments an additional value since the cluster’s cooling water use is restricted for environmental reasons.

IntroDuctIon of bIogenIc feeDStocKThe cluster has a total ethylene consumption of approximately 700 kt/yr. Most of this ethylene is produced in the Borealis con-ventional steam cracker plant, see Figure 1. Feedstocks used in-

INEOSBorealis

Cracker plant

Akzo Nobel

AGA

Excess heat for district heating

purposes

Excess heat for district heating purposesCluster total

Fuel to boilers: 167 MWHeat from boilers: 125 MWCooling: 653 MWHeat recovered by the utility system: 318 MW

Steam1 MW

Steam29 MW Borealis

Polyethylene plant

Perstorp

Figure 3. An overview of the clusters current energy usage and inter-company energy deliveries.




clude naphtha, ethane, propane and butane. The capacity of the cracker plant is limited to approximately 600 kt/yr. Therefore, an additional 100 kt ethylene are imported each year.

The cluster’s vision states that by 2030, production should be based on renewable feedstock and energy sources. One way to realize the vision is to implement a biorefinery producing the feedstocks to the cluster’s processes based on biomass instead of fossil feedstock. For the cluster analysed in this paper, ethylene is by far the most important feedstock. Consequently, in this paper, the focus is on different options for replacing the fossil ethylene with biogenic ethylene. For this purpose, two different biorefin-ery concepts for integration in the cluster are considered:

• Ethylene production from bio-ethanol through ethanol de-hydration

• Olefins (mainly ethylene and propylene) production from synthesis gas generated in a biomass gasification plant

ethylene production from bio-ethanol through ethanol dehydrationThere are several possible options regarding both the type of biomass feedstock used for the ethanol production (sugarcane or lignocellulosic), and the number of production chain sub-processes to be located on-site at the cluster (alternatively etha-nol and/or ethylene can be imported to the cluster).

table 1. Scenarios for heat integration. the scenarios are based on previous work by hackl et al. (2011a) and Andersson et al. (2011).

Extensive heat integration Moderate enhancement of heat integration

Current level of heat integration, baseline

Scenario description

The full potential is implemented.

Only moderate changes and the most efficient integration between the different companies are implemented.

Without collaboration between the companies (heat import/export) only minor improvements are possible and thus the potential for fuel savings through increased heat integration is very limited if collaboration does not take place. Therefore the current integration status (se Figure 3) is considered as a “worst case” scenario.

Heat savings potential

120 MW (~100 % of the heat produced in boilers based on purchased fuels)

67 MW (~50 % of the heat produced in boilers based on purchased fuels)

0 MW

Description of changes needed in order to realise the heat savings potential

Extensive and complex changes with high investment costs are required (new equipment, changes in steam levels, common utility systems, redistribution of steam, increased steam generation from excess process heat, etc.)

Moderate changes. These changes have been judged by technical plant staff to be relatively easy to implement from a technical perspective Requires modifications of heat exchanger area and piping. Sufficient space is available to conduct the modifications and no additional pipe racks are needed.

No changes to the current heat integration scheme and no integration between different companies. Integration only made within each company

Degree of collaboration

High Moderate No collaboration

3 MW

40 MW13 MW

27 MW

4 MW

22 MW

10 MW

7.5 MW

0.5 MW

Low pressure steam

Hot water

Fuel

Perstorp

BorealisPolyethylene plant

BorealisCracker plant

AGA

Akzo Nobel

INEOS

Figure 4. An overview of the energy and fuel exchanges between the different companies if the moderate heat integration scenario described in Table 1 is realised.




In the short term, it is likely that bio-ethanol dehydration for the production of ethylene will be established in regions with cheap access to bio-ethanol, e.g. Brazil, where the etha-nol usage in the transportation sector is on the same level as usage of fossil-based fuels (on an energy basis) (Jones et al., 2010). In a more medium term perspective however, commer-cial introduction of lignocellulosic ethanol in Europe and the US could make direct utilization of bio-ethanol from lignocel-lulosic biomass for ethylene production a viable option (Jones et al., 2010). For example, Stephen et al. (2011) have shown that lignocellulosic ethanol could be competitive with corn ethanol by 2020. Lignocellulosic ethanol production is espe-cially interesting in regions with abundant forest assets and/or pulp and paper industry since the wood handling infrastruc-ture is already in place. Furthermore, older, less efficient kraft pulp mills can be efficiently converted into ethanol production plants (Fornell, 2010).

The production of ethylene by dehydration of ethanol is a proven process (Winter, 1976). As an example, Braskem (a large Brazilian chemical company producing mainly thermoplastic resins) started a full-scale plant in Brazil in 2010 (Braskem, 2012b). The process consists of the dehydration reactor and several subsequent purification steps in order to obtain poly-mer grade ethylene, as described in Kochar et al. (1981).

Figure 5 gives a schematic overview of the ethanol dehydra-tion process considered in this paper. In the process, ethanol is pressurized to reactor operating pressure and then evaporated (Kochar et al., 1981; Barrocas et al., 1980; Morschbacker, 2009). After the reactor, water, unconverted ethanol and other impuri-ties are removed from the effluents in a direct contact quench tower (Winter, 1976). The gas stream leaving the quench tower mainly consists of ethylene. The gas is compressed in a multi-stage compressor with intercooling and then fed to the caustic tower, where CO2 is absorbed with a sodium hydroxide (NaOH) solution. Thereafter the gas enters the final purification stage. In the ethylene column (C2 splitter) heavier impurities, such as ethane, ethanol, diethylether and acetaldehyde are removed by cryogenic distillation. In the stripper column, lighter impuri-ties such as CO, CH4 and H2 are removed. The two columns have a common condenser which operates at -25 °C (Chema-tur, 2010). The lighter impurities are vented from the condenser to the atmosphere. After the stripper column the ethylene has reached polymer grade purity.

As stated above, in Europe and the US efficient bio-ethylene production from ethanol is expected with the commercial in-troduction of lignocellulosic ethanol. Sweden has a long tradi-tion of utilizing its’ vast forest resources. Within the cluster the lignocellulosic bio-ethanol and the ethylene production proc-ess could be directly connected to each other. If the ethanol is produced on site this would make the cluster less depend-ent on imports and world market ethanol prices. A graphical representation of the combined bio-ethanol and ethylene pro-duction process is shown in Figure 6. The implementation can be made stepwise, first implementing an ethanol dehydration plant utilising imported ethanol and once the technology is available, implementing a lignocellulosic ethanol plant in order to produce ethanol on-site.

A process for producing bio-ethanol from lignocellulosic biomass as assumed in Figure 6 is shortly described in the fol-lowing (for further reading see e.g. Wingren et al. 2004). The process is not yet commercially available and several potential process routes are investigated by the research and development community. The process assumed in this paper is based on si-multaneous saccharification and co-fermentation (SSCF) of the hemicelluloses and cellulose sugar. For a more detailed descrip-tion see Wooley et al. (1999) and Carvalheiro et al. (2008). The ethanol concentration of the slurry leaving the SSCF reactor is 4–5 wt%. For ethanol purification a two-step process is applied, after which the ethanol concentration is 93 wt%. As a result of co-locating the two processes, it is not necessary to increase the ethanol concentration to more than 92–96 wt%. Thereby energy demanding azeotropic distillation can be avoided (Hamelinck et al., 2005). After evaporation of the solid by products the syrup can be utilised as fuel in a CHP plant. The solid residue (mainly lignin) from the beer column and the concentrated syrup from the evaporation plant can be used to generate heat to the proc-ess and electricity in a CHP plant. If necessary, bark from the debarking process can also be used.

gasification of wood residues to olefins (ethylene and propylene) via methanolGasification is the conversion of carbonaceous fuel to a gaseous product with a usable heating value. The product gas consists mostly of syngas which can be used as a fuel or as a feedstock for fuels and chemicals (Higman and Burgt, 2008). Convert-ing the syngas into olefins could be suitable for the Stenung-

Ethanol (93 wt%)

Ethylene purification

AdiabaticReactor

(11.4 bar)

By-productsAdditional fuel

450 °C

386 °C

FurnaceQuench Tower

Compressor

Caustic TowerDryer

Ethylene(Polymergrade, i.e. 99.95 vol%)

Steam injection

Figure 5. A schematic description of the ethylene production process through ethanol dehydration (based on Chematur (2010)).




sund cluster, as olefins are a major feedstock to several of the production processes. This conversion can be performed in two steps. First the syngas is conditioned and converted into methanol. The methanol then is sent to a methanol-to-olefins process (MTO) where it is converted into mainly ethylene and propylene. The biomass gasification reaction is endothermic and is heated by combustion of parts of the incoming biomass. After gasification the hot syngas has to be cooled, meaning that there is an excess of heat. The methanol synthesis and the MTO reaction are exothermic.

There are a number of different gasifier types which are able to handle different feedstock and have different product out-puts. Figure 7 shows examples of gasifiers, namely indirect, air blown and oxygen blown gasifiers. If an oxygen-blown gasifier were to be implemented in the Stenungsund cluster, it would be of special interest for AGA Gas AB since one of their main products is oxygen. The gas leaving the gasifier mainly consists

of CO, H2, CO2, CH4 and water vapour (Heyne, 2010). In order to make it suitable for further processing it has to be cleaned and conditioned. In some cases it is necessary to adjust the CO/H2 ratio in to make the gas suitable for methanol synthesis. Tars formed during gasification of biomass have to be removed, typi-cally by scrubbing prior the downstream synthesis process. The remaining hydrocarbons in the products gas are converted into CO and H2 in a reforming step. The produced syngas is then converted methanol. The synthesis reactions are exothermic. In the gasification processes heat is released and has to be removed to maintain optimum catalyst life and reaction rate (Hamelinck and Faaij, 2001). Thus, the gasification process has significant amounts of excess heat available which could be used to heat integrate other industrial processes which have a heat demand.

The MTO process is described by e.g. Kvisle et al. (2002). In this paper the UOP/HYDRO process design is assumed. This process can produce both ethylene and propylene – similarly

Two-step dilute acid steam pretreatment

Lignocellulosics(50% moisture)

Enzymatic hydrolysis

Co-fermentation

SSCF*

*SSCF – Simultaneous Saccharification and Co-Fermentation

Ethanol purification

Ethanol (93 wt%)

Evaporation

Solid residues

CHP

Process steam

Utility steam

Electricity

Excess solidresidues

Ethylene purification

Adiabatic

Reactor

(11.4 bar)

By-products

Additional fuel

450 °C

386 °C

FurnaceQuench Tower

Compressor

Caustic TowerDryer

Ethylene(Polymergrade, i.e. 99.95 vol%)

Steam injection

Figure 6. A schematic description of combined ethanol production from lignocellulosic feedstock and ethanol dehydration for ethylene production (based on Wingren et al. (2004)).

Pretreatment(e.g. Drying, Torrefaction)

Gasification(Low pressure – oxygen blown)

Gasification (High pressure – oxygen blown)

Indirect Gasification

Gasification (with hot gas conditioning as future alternative)

Air separation unit (Oxygen production)

Reforming

Shift conversion

Reforming

Hot gas cleaning

Acid gas removal

Methanol synthesis

Carbon Dioxide

MethanolMethanol-‐to-‐Olefins (MTO) process

Ethylene and Propylene

By-‐products, e.g Propane, Ethane, mixed C4 and C5+

Biomass

Figure 7. A schematic overview of thermochemical routes for olefins production by biomass gasification and methanol-to-olefins (MTO) process, based on Bain (1992) and UOP (2004).




to a conventional steam cracker unit such as the one operated in Stenungsund – but is more flexible to adjusting the ratio between ethylene and propylene compared to a conventional steam cracker unit. Possible propylene/ethylene ratios range from 0.77 to 1.33 (Uop, 2004). In the reactor, methanol is con-verted into olefins via DME (dimethyl ether). The MTO reac-tion is exothermic. After the reactor the products are purified in several cleaning steps comparable with the gas cleaning in a conventional steam cracker. Polymer-grade ethylene and pro-pylene are produced.

Just as for the lignocellulosic ethanol to ethylene case, gasi-fication of wood residues to olefins via methanol can be imple-mented stepwise, first implementing a MTO plant based on im-ported methanol and later, when the technology is commercial, implementing a biomass gasification plant.

Scenarios for biogenic feedstockBased on the two biorefinery concepts described above, three scenarios for introduction of biogenic feedstock at the Ste-nungsund cluster were defined. These scenarios are presented in Table 2.1

One challenge for replacing fossil feedstock with biogenic feedstock is the magnitude of the biomass requirements. Even though the cluster is small by international standards, just re-placing the fossil based ethylene which is currently imported with ethylene produced on-site from biogenic feedstock would require ~675 kt-dry biomass/yr of forest biomass. This is equal to approximately half the amount of wood used at a medium sized pulp and paper mill in Sweden. Thus it is important for the cluster to be as material and energy efficient as possible in order to get as much value as possible out of the imported bio-genic feedstock.

technology pathwaysThe scenarios for biogenic feedstock and heat integration (pre-sented in Tables 1 and 2) are interdependent to varying extents and can be combined in different ways. Table 3 presents nine technology pathways possible for the Stenungsund cluster. The pathways are combinations of the scenarios for heat integration and biogenic feedstock presented in Tables 1 and 2.

In summary it can be said that the first option, ethylene from imported ethanol represents a first step towards a green chemical cluster, which can in a second step (production of lignocellulosic ethanol on-site) be completed once the technology is available. Excess heat from a single ethanol dehydration plant can be de-livered to the non-integrated cluster and when implementing an ethanol production on-site this heat can be used for ethanol separation, while the cluster is internally heat integrated.

Heat integration plays an essential role in all biogenic feed-stock scenarios as it determines how efficiently the feedstocks can be utilised. If no heat integration is made between the in-dividual plants in the cluster the potential for heat integration with other (new) processes can seem promising, however, this appearance is somewhat deceptive since the cluster itself still uses heat inefficiently.

1. Imported ethanol to ethylene, degree of collaboration between individual compa-nies: It is, however, not to likely that Perstorp would (alone) invest in such a plant since it is outside their core business and their ethylene consumption is rather low.

Compared to gasification, production of ethanol from ligno-cellulosics has the advantage that the non-utilised biomass (bioenergy) is in form of solid by-products and therefore it does not necessarily need to be utilised on-site. For gasification, the bioenergy is already converted into heat which limits the poten-tial for alternative applications. This fact has a strong influence on the clusters further potential and incentives for heat saving measures once the biogenic feedstock scenario is implemented.

DiscussionAs previously stated, to be implemented fully, the vision of Sus-tainable Chemistry in 2030 requires not only that new technol-ogies and efficient technical system solutions are implemented (here called technology pathways) but also a well-developed cooperation between different actors and that a number of non-technical barriers are overcome. Above, different technol-ogy pathways are presented. In the following, different aspects of these technology pathways and of the vision of Sustainable Chemistry in 2030 are explored briefly. From an organisational perspective, the scenarios for introduction of biogenic feed-stock and heat integration have different characteristics. The scenarios for biogenic feedstock can be implemented by one actor alone as well as by some of the companies together or, as an alternative, by an external party, selling the green ethylene or methane to the companies in the cluster. Conversely, the scenarios for increased heat integration require collaboration between the different companies and cannot be successfully implemented by one company alone. Also, from a business perspective, the scenarios for heat integration are creating value for the companies through reduction of costs whereas the scenarios for biogenic feedstock aim for increased rev-enues (achieved through increased market shares, production of higher-value products, etc.).

Today the work with the vision of Sustainable Chemistry in 2030 is performed by a project group that includes representa-tives from the individual companies and the Swedish Plastics and Chemicals Federation together with a consultant work-ing as the project leader. The representatives all have different positions in their companies and consequently hold different mandates for making decisions during meetings. One draw-back with the current formation is that it is not a legal entity and thus cannot apply for public funding; any funding has to go through the individual companies. This could hinder the work in a later stage if e.g. a demonstration plant for gasifica-tion or fermentation of biomass is projected. Further, this cur-rent organization with a loosely formed project group gives the participants a weak connection to the vision work compared to their connection with their companies.

collAborAtIon moDelSOne issue related to the investments needed to implement the scenarios for introduction of biogenic feedstock and heat in-tegration is that due to the complexity of the material and en-ergy exchanges in the cluster, investments made in one plant/by one company benefits other plants/companies. Thus, it is not necessarily the company making the investment that will gain the most benefits. This of course has an effect on the compa-nies’ willingness to make different investments. Reniers et al. (2012) propose a Multi-plant Collaboration Model (MCM) to




table 2. Scenarios for biogenic feedstock.

Scenario for biogenic feedstock

Scenario description Amount of biogenic feedstock requires/Size considerations

Commercial status

Degree of collaboration between individual companies

Imported ethanol to ethylene

Imported ethanol is used as feedstock in an on-site ethanol dehydration plant producing polymer-grade ethylene. The process has a heat demand of ~3.8 MJ/kg-ethylene of direct steam at ~11.4 bar. Furthermore, 4.86 MJ/kg-ethylene of hot flue gases are used for reactor heating. The process has potential for excess heat export in the form of 2 bar(g) steam, up to ~4.7 MJ/kg-ethylene.

A commercial plant started up in Brazil in 2010 with a capacity of 200 kt-PE/y (Braskem, 2012b). This is approximately the same capacity as the ethylene imports to the cluster. Dow is “very enthusiastic” and has plans for a ca. 350,000 kt/y PE plant using ethylene derived from sugar cane ethanol (Evans, 2011). The ethylene yield is ~0.57 kg/kg-ethanol (Hackl et al., 2011b). Thus, a plant covering the ethylene import to the cluster would demand ~175 kt-ethanol/yr (1,230 kt-ethanol/yr for full substitution).

Commercial process

Low to medium depending on which companies invest in the plant. Borealis has no use for the excess steam from the E-to-E process and therefore collaboration is needed with e.g. Perstorp to sell the steam. If Perstorp invests in such a plant no heat collaboration is needed, as they – to a certain degree – can utilize the excess steam in their own plant.

Ligno-cellulosic biomass (e.g. wood residues) to ethanol to ethylene

Ethanol is produced on-site and directly delivered to an ethanol dehydration plant. The ethanol production process has a large heat demand at temperatures of around 100–120 °C. Excess heat from the E-to-E plant is available in this temperature range resulting in clear integration advantages for these two processes. The ethanol plant also produces an excess of combustible solid residues (ca. 69 MJ/kg-ethylene) which are utilised to generate heat (and electricity) to the ethanol and ethylene processes and could also be used for generating heat (and electricity) to the cluster.

The feedstock logistics is probably the most size-limiting factor. Only app. 16 % of the dry raw material mass is converted to ethylene (Hackl et al., 2011b). A plant covering the ethylene import to the cluster (~100 kt/yr) consumes 675 kt-dry mass/yr. If the ethanol plant delivers heat to the cluster the heat demand of the cluster is another size limiting factor, even though not as important since combustible residues can be exported.

Wood to ethanol is not commercial. However, the process for converting ethanol to ethylene is commercial (see above).

Low for the case where the plant does not supply heat (and electricity) to the cluster. The ethanol plant and the E-to-E plant can be well integrated with each other, giving less integration opportunities with the cluster. High for the case where heat and electricity are delivered to the cluster, requiring development of a common heat supply infrastructure. The ethylene produced can be directly delivered to the existing ethylene distribution network.

Gasification of wood residues to methanol to olefins (ethylene and propylene)

In a biomass gasification plant, solid carbonaceous feedstock is converted into syngas which, via methanol, is converted into olefins (mainly ethylene and propylene). The gasification reaction is endothermic, supplied with heat by combustion of parts of the incoming biomass. The hot syngas has to be cooled, giving an excess of heat at high temperature. The methanol synthesis and the MTO reaction are exothermic. In general, it can be said that, if properly integrated, the biomass to olefins process has an excess of heat which can be used for supplying heat to the surrounding processes and generating electricity.

The size of the plant is mainly limited by the heat demand of the cluster, since utilisation of process excess heat is essential for an efficient use of feedstock and very important for the economy of the process. However, feedstock logistics is also an important factor as is the ethylene/propylene use ratio of the cluster.

Gasification of wood to methanol is not commercial. However, the process for converting methanol to olefins is commercial.

High since heat delivery to the cluster and economics of scale are very important for economic and efficient operation of such a plant. Therefore the development and operation of a common heat supply infrastructure is essential.




way that the investments made by one actor will, in some cases, primarily benefit other actor. Thus, it could be an option to use a similar approach in order to enhance and realize the potential heat collaboration.

the vISIon AS An enD or AS A meAnS for collAborAtIonDepending on whether the vision is analysed from an instru-mental/technical point of view or from an organisational point of view, the vision of Sustainable Chemistry in 2030 can be regarded as an end or as a means for (further) collaboration. Since the vision is rather vague and lacks specific goals, to view

facilitate collaboration for cross-plant prevention in a chemi-cal cluster. Based on game-theory insights, the MCM is used to analyse whether collaboration is (financially) beneficial and to suggest models for how to divide potential (financial) collaboration benefits in order to stimulate cooperation. Fur-thermore, Reniers et al. suggests an independent supra-plant council for the purpose of enhancing and realising collabora-tion. The main purpose of applying an independent supra-plant council is to overcome confidentiality issues. The studied case of collaboration for cross-plant prevention has similarities to the Stenungsund scenarios for increased heat integration in the

table 3. technology pathways. for each technology pathway the degree of collaboration, potential to reach the vision and comments are presented.

Process for biogenic feedstock(vertical) \Heat integration (horizontal)

Integrated: 100 % of theoretical potential

Collaborative: ~50 % of theoretical potential

Base case, current heat integration: 0 % of theoretical potential

Imported ethanol to ethylene

Degree of collaboration: very high

Potential to reach the vision: medium

Comments: first step taken towards a renewables based feedstock supply. Heat integration potential of the cluster with the ethylene dehydration plant is low, since the cluster’s heat demand is covered using internal excess heat.

Degree of collaboration: high


Comments: first step taken towards a renewables based feedstock supply. Heat integration potential of the cluster with the ethylene dehydration plant is rather low, since large parts of the cluster’s heat demand are covered using internal excess heat.

Degree of collaboration: low

Potential to reach the vision: low

Comments: The cluster could be more energy efficient and needs to import large amounts of fossil fuels; a first step is taken to switch to renewables based feedstock supply. Heat integration potential of the cluster with the ethylene dehydration plant is high but the overall energy efficiency of the cluster could be significantly improved.

Lignocellulosic biomass (e.g. wood residues) to ethanol to ethylene

Degree of collaboration: Very high

Potential to reach the vision: high

Comments: Part of the feedstock demand is covered by biogenic feedstock. Optimal heat integration results in a heating demand close to zero which means that by-products from the ethanol/ethylene plant can be exported and used for other purposes (feedstock to other processes, electricity generation, etc.)

Degree of collaboration: High


Comments: Part of the feedstock demand is covered by locally produced renewables. The cluster applies partial site-wide heat integration giving a lower heat demand. The remaining heat demand can be supplied by combustion of renewable by-products from the ethanol/ethylene plant. Still, fairly large amounts of by-products from ethanol/ethylene plant can be exported and used for other purposes.

Degree of collaboration: Low to medium


Comments: The vision doesn’t explicitly state demands for energy-efficiency, only renewables based feedstock. Implementing this type of biorefinery a part (or most) of the raw materials and energy consumption can be based on renewables. Yet, the cluster still consumes an unnecessarily large amount of heat which leads to less (or no) surplus of by-products from the ethanol/ethylene plant remains for export.

Gasification of wood residues to methanol to olefins (ethylene and propylene)

Degree of collaboration: Very high


Comments: if the cluster is perfectly integrated there is no need for excess process heat from a biomass gasification plant. This means that the gasification plant can produce more electricity, but with a lower overall efficiency. For a high total efficiency additional heat sinks are needed, e.g. an extension of the Gothenburg district heating network.



Comments: since the cluster is partly heat integrated there is still a need for external heating which can be delivered by a biomass gasification plant. The size of the heat sink (in this case 60 MW) determines the size of the gasification unit.



Comments: since the cluster is not heat integrated there is a large need for external heating which can be delivered by a biomass gasification plant. Thus the gasification plant produces heat and electricity in an efficient way, but the cluster itself still uses heat inefficiently. The size of the heat sink (125 MW) determines the size of the gasification unit. Large risk for suboptimisation, since once the gasification plant is in place there are no incentives for reduction of the heat demand since it is supplied by excess heat.




process were to be produced on site – based on lignocel-lulosic biomass – 4,725 kt-dry biomass/yr of forest biomass would be required. This is more than the biomass demand for four large pulp and paper mills.

• Enhancing energy efficiency and switching to biogenic feedstock are interdependent technology options. This means that either synergies or lock-in effects can be achieved depending on how they are combined. For gasification, for example, the size of the plant is mainly limited by the heat demand of the cluster, since utilisation of process excess heat is essential for the economy of the process. This fact has a strong influence on the clusters further potential and incen-tives for heat saving measures (e.g. enhanced heat integra-tion) once implemented. To avoid lock-ins and suboptimi-zations for stepwise implementation of heat integration and biogenic feedstock these facts are important to keep in mind.

• Collaboration is a key issue. One important finding from the impact analysis is that regardless of which pathway the cluster wants to travel in their journey towards sus-tainable chemistry, collaboration is a key issue since the companies in the cluster will have to move from loosely material-integrated towards different levels of deep sys-tem-integrated business cooperation through a complex process of change. For the cluster to be successful in their transformation process, it is essential to achieve a double-loop learning system where the vision for Sustainable Chemistry 2030 can be used as means for further collabo-ration between the different companies and reflection of the individual companies underlying strategies and norms.

AbbreviationsCHP Combined heat and powerDME Dimethyl eterE-to-E Ethanol to ethyleneMCM Multi-plant Collaboration ModelMTO Methanol to olefinsPE PolyethylenePVC Polyvinyl chlorideSNG Synthetic natural gasTSA Total site analysis

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