Final Report Summary - COPOWER (Synergy Effects of Co-processing of Biomass with Coal and Non-toxic Wastes for Heat and Power Generation)
The COPOWER project aimed at determining the limits of the optimised operation that could be beneficial in getting rid of waste and promoting biomass for environmentally acceptable energy generation.
The project defined its main objectives as given below:
1) The evaluation of the biomass resources for three specific countries, namely Portugal, Italy and Turkey.
2) The identification of techno-economic barriers to the utilisation of biomass and other wastes as energy source from either plantation or waste production sites, as energy sources for the three countries. A case study including three countries will be conducted.
3) The analysis of adequate fuel preparation systems to achieve synergy in fuel mixes to be prepared for energy processes.
4) The characterisation of the wastes available to determine their potential for synergy in fuel mixes to be prepared with a particular attention given to reactivity, ash composition and ash fusion point.
5) The understanding of the combustion of fuel mixes in fluidised beds with the aim of determining the limits of optimised synergy for efficiency.
6) The understanding of ash behaviour during the combustion to determine synergy required in the fuel mix preparation to minimise the tendency to slagging and fouling.
7) The determination of the levels of the pollutants resulting from the co-firing system and definition of conditions for synergy of different components in the fuel to minimise the emissions of potential pollutants to the atmosphere.
8) The analysis of ashes produced during co-firing with the aim of their re-utilisation.
9) The socio-economic and environmental impacts of the co-firing technology.
10) Based on the results, the evaluation of co-firing for energy production in an economically acceptable manner by closely analysing the costs involved and the potentials to reduce costs.
Fluidised bed systems are particularly well suited for such a co-firing operation because of their versatility with regard to fuel. The project, by achieving these objectives, addressed the issues related to the whole chain of fuel supply for co-firing, optimising combustion process involving multi-fuels, and ways of optimising its economic and environmental consequences, in order to overcome the above mentioned barriers. The co-firing tests were carried out using fluidised beds which offer the versatility required to deal with different fuels at the same time.
The project was structured into seven work packages (WPs) with the aim of addressing the issues raised in the objectives above. The WPs were:
- WP1: Fuel supply chain analysis
- WP2: Fuel characterisation of biomass and waste materials. WP2 work was carried out during the second year and a final report was elaborated at the end of the second year and all five tasks during year 2 of the project. A major effort was spent on characterising all of the fuels selected for the project, principally a set from CTH (based on Polish coal, straw and sewage sludge), plus one from SD (based on Columbian coal plus meat and bone meal plus wood chips). These fuels were subjected to a whole suite of analyses and a large body of data produced. Subsequent activities focused on assessment of fuel volatility, char combustion and attrition, and ash behaviour using bench-scale equipment. In addition, some raw fuels plus their binary blends have been characterised for their trace element behaviour during simulated fluidised bed combustion conditions.
- WP3: Co-firing trials aiming at the synergy of different fuels to optimize the plant operation and environmental emissions. The results obtained from pilot-scale tests were compared with those from the Duisburg plant. During the tests, the operating parameters and gaseous emissions were recorded and distributed to the contractors. Similar to tests of last year, fuel and ash samples were taken in order to ensure that all tests of the contractors were made with same fuels and ashes. The theoretical work on technology assessment and the simulating tools was also completed and the ecotoxicological risk assessment of ashes delivered were finalised.
- WP4: Environmental impact assessment and socio-economic assessment.
- WP5: Management and optimisation of the whole chain and market analysis. Management and optimisation of the whole chain and market analysis were undertaken in the scope of WP5 and the critical points were identified as:
1. The processes of the different phases are strongly heterogeneous, because the utilities and machines have different characteristics, power and productivity.
2. The type of biomass influences the processes and also the supply chain structure.
3. Storage. This point is critical, especially if it is made either before the transport phase or before the combustion process.
- WP6: Dissemination.
- WP7: Coordination. It is unlikely that a plant would obtain and burn a single waste or biomass for a prolonged period. It is more likely that plant officials would buy or offer to dispose of a number of wastes available to them locally. Therefore, potential problems and synergies arising from the various combinations need to be identified. That is why COPOWER studied different combinations, not only using different coals but also several waste materials which are usually very country specific. In addition, a database was created to get the information about fuels, even those not experimented in the project. The fuels selected reflect the variations in different countries, particularly between the Northern and Southern Europe.
Previous co-firing tests, mostly in pulverised fuel combustion systems were undertaken using coal as the base fuel and admitting relatively small amounts of waste or biomass (no more than 10 % of thermal input). There are presently two main attitudes to co-firing. One regards coal as the problem, largely due to the quantities of CO2 produced and their enhancement of the greenhouse effect. Co-firing, especially with 'CO2-neutral' biomass is a way of displacing coal as a fuel and thus reducing greenhouse gas emissions. A study, undertaken during the execution of this project, analysing the fuel consumption in large-scale power plants has suggested that in energy terms, the substitution of about 10 % of coal by mass with biomass with 15 % humidity levels could reduce the CO2 released more than 8 %, the limit set up in the scope of the Kyoto Protocol.
There is a need for a new perspective to be introduced in the context of multi-fuel systems which could avoid the dependence on any one fuel for energy production. COPOWER aims at introducing this concept because the trend in the future has to be with systems operating on multi-fuel mixes. For this reason, combinations of coal, biomass and waste will be tried and early results show that multi-fuel use could lead to overcoming many problems like reducing heavy metal vaporisation by the presence of S, Cl, etc. This could also have beneficial effect of fixing S, Cl, etc. in the ashes rather than their emissions to the atmosphere. Combining high S fuels with high Cl ones could have beneficial effect on suppressing dioxin emissions. The limits have to be well defined to give the operators the flexibility of the mixing different combinations. COPOWER aimed at improving the knowledge for fuel blending.
From the results obtained, a list was made summarising the positive synergies achieved during co-firing tests and they were the following:
1) The addition of sludge changes bed inventory and axial solids distribution and improves heat transfer in upper part of combustion chamber (finding in large-scale test supported by bench-scale work on fragmentation).
2) Influence of waste addition on dust emissions, yet unclear (possibly agglomeration of fine dust particles or improvement of EP by addition of water).
3) Sewage sludge captures KCl from biomass.
4) Sulphur in coal helps to avoid KCl formation problems.
5) Coal ash helps to avoid KCl formation problems.
6) The ash of sewage sludge may be beneficial in capture of potassium, because it consists partly of zeolites. It forms potassium-aluminia-silicates.
7) Co-combustion of coal, sewage sludge and straw improves retention of six heavy-metals in bottom ashes.
9) Co-combustion with waste and biomass reduces NOx-emissions.
10) Co-combustion with low sulphur containing biomass reduces lime consumption.
11) No significant change in eco-toxicity and leachability of metals of ashes with co-combustion.
12) Ca-rich waste can reduces the limestone requirement in co-combustion (waste must be low in phosphorous, calcium phosphate is formed).
13) Devolatilisation is increased with co-combustion of coal and straw, at the same time temperature of devolatilisation is decreased.
14) Co-combustion of coal, sewage sludge and biomass reduces the pressure drop in the combustion chamber and thus the energy requirement.
15) Feeding of biomass reduces the amount of residues (attention must be paid for a sufficient bed inventory).
The list giving the negative synergies observed is seen below:
1) Avoid firing fuels highly loaded with Hg.
2) In case high K-containing fuel its amount has to be restricted in the feed to avoid agglomeration.
3) Negative synergies might occur with heavy metals (e.g. Pb, Zn).
4) The water content in the waste increases the flue gas flow. This may increase the heat loss.
5) For the control of dioxins and furans, it is necessary to have high S/Cl ratio to minimise the emission levels.
The project defined its main objectives as given below:
1) The evaluation of the biomass resources for three specific countries, namely Portugal, Italy and Turkey.
2) The identification of techno-economic barriers to the utilisation of biomass and other wastes as energy source from either plantation or waste production sites, as energy sources for the three countries. A case study including three countries will be conducted.
3) The analysis of adequate fuel preparation systems to achieve synergy in fuel mixes to be prepared for energy processes.
4) The characterisation of the wastes available to determine their potential for synergy in fuel mixes to be prepared with a particular attention given to reactivity, ash composition and ash fusion point.
5) The understanding of the combustion of fuel mixes in fluidised beds with the aim of determining the limits of optimised synergy for efficiency.
6) The understanding of ash behaviour during the combustion to determine synergy required in the fuel mix preparation to minimise the tendency to slagging and fouling.
7) The determination of the levels of the pollutants resulting from the co-firing system and definition of conditions for synergy of different components in the fuel to minimise the emissions of potential pollutants to the atmosphere.
8) The analysis of ashes produced during co-firing with the aim of their re-utilisation.
9) The socio-economic and environmental impacts of the co-firing technology.
10) Based on the results, the evaluation of co-firing for energy production in an economically acceptable manner by closely analysing the costs involved and the potentials to reduce costs.
Fluidised bed systems are particularly well suited for such a co-firing operation because of their versatility with regard to fuel. The project, by achieving these objectives, addressed the issues related to the whole chain of fuel supply for co-firing, optimising combustion process involving multi-fuels, and ways of optimising its economic and environmental consequences, in order to overcome the above mentioned barriers. The co-firing tests were carried out using fluidised beds which offer the versatility required to deal with different fuels at the same time.
The project was structured into seven work packages (WPs) with the aim of addressing the issues raised in the objectives above. The WPs were:
- WP1: Fuel supply chain analysis
- WP2: Fuel characterisation of biomass and waste materials. WP2 work was carried out during the second year and a final report was elaborated at the end of the second year and all five tasks during year 2 of the project. A major effort was spent on characterising all of the fuels selected for the project, principally a set from CTH (based on Polish coal, straw and sewage sludge), plus one from SD (based on Columbian coal plus meat and bone meal plus wood chips). These fuels were subjected to a whole suite of analyses and a large body of data produced. Subsequent activities focused on assessment of fuel volatility, char combustion and attrition, and ash behaviour using bench-scale equipment. In addition, some raw fuels plus their binary blends have been characterised for their trace element behaviour during simulated fluidised bed combustion conditions.
- WP3: Co-firing trials aiming at the synergy of different fuels to optimize the plant operation and environmental emissions. The results obtained from pilot-scale tests were compared with those from the Duisburg plant. During the tests, the operating parameters and gaseous emissions were recorded and distributed to the contractors. Similar to tests of last year, fuel and ash samples were taken in order to ensure that all tests of the contractors were made with same fuels and ashes. The theoretical work on technology assessment and the simulating tools was also completed and the ecotoxicological risk assessment of ashes delivered were finalised.
- WP4: Environmental impact assessment and socio-economic assessment.
- WP5: Management and optimisation of the whole chain and market analysis. Management and optimisation of the whole chain and market analysis were undertaken in the scope of WP5 and the critical points were identified as:
1. The processes of the different phases are strongly heterogeneous, because the utilities and machines have different characteristics, power and productivity.
2. The type of biomass influences the processes and also the supply chain structure.
3. Storage. This point is critical, especially if it is made either before the transport phase or before the combustion process.
- WP6: Dissemination.
- WP7: Coordination. It is unlikely that a plant would obtain and burn a single waste or biomass for a prolonged period. It is more likely that plant officials would buy or offer to dispose of a number of wastes available to them locally. Therefore, potential problems and synergies arising from the various combinations need to be identified. That is why COPOWER studied different combinations, not only using different coals but also several waste materials which are usually very country specific. In addition, a database was created to get the information about fuels, even those not experimented in the project. The fuels selected reflect the variations in different countries, particularly between the Northern and Southern Europe.
Previous co-firing tests, mostly in pulverised fuel combustion systems were undertaken using coal as the base fuel and admitting relatively small amounts of waste or biomass (no more than 10 % of thermal input). There are presently two main attitudes to co-firing. One regards coal as the problem, largely due to the quantities of CO2 produced and their enhancement of the greenhouse effect. Co-firing, especially with 'CO2-neutral' biomass is a way of displacing coal as a fuel and thus reducing greenhouse gas emissions. A study, undertaken during the execution of this project, analysing the fuel consumption in large-scale power plants has suggested that in energy terms, the substitution of about 10 % of coal by mass with biomass with 15 % humidity levels could reduce the CO2 released more than 8 %, the limit set up in the scope of the Kyoto Protocol.
There is a need for a new perspective to be introduced in the context of multi-fuel systems which could avoid the dependence on any one fuel for energy production. COPOWER aims at introducing this concept because the trend in the future has to be with systems operating on multi-fuel mixes. For this reason, combinations of coal, biomass and waste will be tried and early results show that multi-fuel use could lead to overcoming many problems like reducing heavy metal vaporisation by the presence of S, Cl, etc. This could also have beneficial effect of fixing S, Cl, etc. in the ashes rather than their emissions to the atmosphere. Combining high S fuels with high Cl ones could have beneficial effect on suppressing dioxin emissions. The limits have to be well defined to give the operators the flexibility of the mixing different combinations. COPOWER aimed at improving the knowledge for fuel blending.
From the results obtained, a list was made summarising the positive synergies achieved during co-firing tests and they were the following:
1) The addition of sludge changes bed inventory and axial solids distribution and improves heat transfer in upper part of combustion chamber (finding in large-scale test supported by bench-scale work on fragmentation).
2) Influence of waste addition on dust emissions, yet unclear (possibly agglomeration of fine dust particles or improvement of EP by addition of water).
3) Sewage sludge captures KCl from biomass.
4) Sulphur in coal helps to avoid KCl formation problems.
5) Coal ash helps to avoid KCl formation problems.
6) The ash of sewage sludge may be beneficial in capture of potassium, because it consists partly of zeolites. It forms potassium-aluminia-silicates.
7) Co-combustion of coal, sewage sludge and straw improves retention of six heavy-metals in bottom ashes.
9) Co-combustion with waste and biomass reduces NOx-emissions.
10) Co-combustion with low sulphur containing biomass reduces lime consumption.
11) No significant change in eco-toxicity and leachability of metals of ashes with co-combustion.
12) Ca-rich waste can reduces the limestone requirement in co-combustion (waste must be low in phosphorous, calcium phosphate is formed).
13) Devolatilisation is increased with co-combustion of coal and straw, at the same time temperature of devolatilisation is decreased.
14) Co-combustion of coal, sewage sludge and biomass reduces the pressure drop in the combustion chamber and thus the energy requirement.
15) Feeding of biomass reduces the amount of residues (attention must be paid for a sufficient bed inventory).
The list giving the negative synergies observed is seen below:
1) Avoid firing fuels highly loaded with Hg.
2) In case high K-containing fuel its amount has to be restricted in the feed to avoid agglomeration.
3) Negative synergies might occur with heavy metals (e.g. Pb, Zn).
4) The water content in the waste increases the flue gas flow. This may increase the heat loss.
5) For the control of dioxins and furans, it is necessary to have high S/Cl ratio to minimise the emission levels.