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Resource-efficient drying methods applied to the biomass fired CHP plant. System Study; Resurseffektiva torkmetoder applicerade paa biobraensleeldade kraftvaermeverk. Systemstudie

Technical Report:

Abstract

The study shows that the existing heat-load for the CHP plant can be increased by drying the wet fuel by using the district heating (hot-flow) as heat source, which increases the operating time for the plant and allow for higher electricity production. A drying method which is appropriate is based on the bed drying technique that can be adapted to the temperatures used in district heating systems or which is available in various waste heat sources. The degree of maturity of the bed drying technology for drying of wet fuel consisting of different size fractions is somewhat uncertain. Technical difficulties have been identified and it seems difficult to dry slash. Application of a drying process with the purpose to increase the heat load can be justified for various reasons related to the products to be produced in the plant and combine. In this study, attention is drawn to the drying of fuel for the use in the boiler of the CHP plant and for the production of pellets for sale. Two different plant sizes of CHP plants have been studied. One of 20 MW and one of 50 MW electrical power. For each plant size different combinations of drying, to  More>>
Authors:
Joensson, Mikael; Nystroem, Olle; Hermann, Fredrik [1] 
  1. Grontmij AB (Sweden)
Publication Date:
Dec 15, 2010
Product Type:
Technical Report
Report Number:
ELFORSK-11-05
Resource Relation:
Other Information: 30 refs., 46 figs., 14 tabs.
Subject:
09 BIOMASS FUELS; DRYING; COGENERATION; WOOD FUELS; PELLETS; POWER GENERATION; COST; DISTRICT HEATING; EFFICIENCY
OSTI ID:
1008102
Research Organizations:
Elforsk AB, Stockholm (Sweden)
Country of Origin:
Sweden
Language:
Swedish
Other Identifying Numbers:
TRN: SE1107053
Availability:
Available from: Elforsk AB, SE-10153 Stockholm, Sweden; e-mail: kontakt@elforsk.se or from homepage: www.elforsk.se
Submitting Site:
SWD
Size:
89 p. pages
Announcement Date:
Mar 14, 2011

Technical Report:

Citation Formats

Joensson, Mikael, Nystroem, Olle, and Hermann, Fredrik. Resource-efficient drying methods applied to the biomass fired CHP plant. System Study; Resurseffektiva torkmetoder applicerade paa biobraensleeldade kraftvaermeverk. Systemstudie. Sweden: N. p., 2010. Web.
Joensson, Mikael, Nystroem, Olle, & Hermann, Fredrik. Resource-efficient drying methods applied to the biomass fired CHP plant. System Study; Resurseffektiva torkmetoder applicerade paa biobraensleeldade kraftvaermeverk. Systemstudie. Sweden.
Joensson, Mikael, Nystroem, Olle, and Hermann, Fredrik. 2010. "Resource-efficient drying methods applied to the biomass fired CHP plant. System Study; Resurseffektiva torkmetoder applicerade paa biobraensleeldade kraftvaermeverk. Systemstudie." Sweden.
@misc{etde_1008102,
title = {Resource-efficient drying methods applied to the biomass fired CHP plant. System Study; Resurseffektiva torkmetoder applicerade paa biobraensleeldade kraftvaermeverk. Systemstudie}
author = {Joensson, Mikael, Nystroem, Olle, and Hermann, Fredrik}
abstractNote = {The study shows that the existing heat-load for the CHP plant can be increased by drying the wet fuel by using the district heating (hot-flow) as heat source, which increases the operating time for the plant and allow for higher electricity production. A drying method which is appropriate is based on the bed drying technique that can be adapted to the temperatures used in district heating systems or which is available in various waste heat sources. The degree of maturity of the bed drying technology for drying of wet fuel consisting of different size fractions is somewhat uncertain. Technical difficulties have been identified and it seems difficult to dry slash. Application of a drying process with the purpose to increase the heat load can be justified for various reasons related to the products to be produced in the plant and combine. In this study, attention is drawn to the drying of fuel for the use in the boiler of the CHP plant and for the production of pellets for sale. Two different plant sizes of CHP plants have been studied. One of 20 MW and one of 50 MW electrical power. For each plant size different combinations of drying, to varying moisture content, and with different amount of pellets production has been examined in different plant cases. The drying means that the electricity production can be increased with maintained or reduced electricity production cost. The majority of the increase in generated electricity is created by the drying of wet fuel for the CHP's own needs, i.e. drying of the pellet production is less significant. In this study logging slash (branches and tops from felling) has been used as fuel both for operating the boiler of the CHP and as raw material for pellet production. Since pelleted logging slash is not a fully established product, it has been difficult to determine its value. It is likely that the price will be below what is established for sawdust pellet, in part because of the slash-pellet contains more impurities and thus probably has/will have a somewhat limited audience. The estimated production cost for electricity for the reference plants of 20 and 50 MW{sub e} are 1.16 and 0.86 SEK/kWh excluding electricity-certificates based on a fuel price of 175 SEK/MWh and a heat credit on 0.25/kWh. That is in line with the level of 'Electricity from new plants' (2007) Elforsk Report 07:50, adjusted to the current level of investment and operation and maintenance. The production cost of electricity in the facilities of 20 and 50 MW{sub e} equipped for drying and pellet production are in the range 0.90-1.05 and 0.74-0.82 SEK/kWh with the electricity certificate excluded. In the case where pellet production is prioritized the production cost of electricity is generally reduced with increased pellet production and decreases if the cost of investment represents a small portion of the cost base, which favours 'small' plants with large pellet production. Electricity production costs are strongly influenced by the credit level of pellet. This study is based on a credit level of 250 SEK/MWh. Sensitivity analysis show that the production cost of electricity increases significantly with lower credit levels. The increase is smaller for the larger facility due to, among other things, higher electrical efficiency. In cases where the district heating production is priority, the drying heat needed to run a continuous drying process will not be available during the heating season. Then dried fuel is retrieved when from a fuel stock that is filled during the other time of year when the heating demand is so low that the dryer can be operated at higher capacity than what is equivalent of continuous consumption of the boiler. In the smaller 20 MW{sub e} plant a higher electricity production cost (0.99 SEK/kWh) is obtained compared to the case where the pellet production for sales is priority (0.90-0.98 SEK/kWh), which is due to that the increased investment, that particularly the dryer and storage of dried fuel, does not offset by revenue from the increase in electricity. In the larger 50 MW plant a lower cost (0.74 SEK/kWh) is obtained compared with the case where the pellet production for sale is priority (0.76-0.80 SEK/kWh), depending on the economies of scale and higher electrical efficiency. Based on the accuracy level (budget quotes) that is applied in this study the conclusion is that drying and pellet production does not seem to give any convincing profitability. One reason for the lack of profitability may be sought in the difficulties that arise if the raw material used is logging slash at market price. A production of logging slash pellets are to compete with businesses that produce wood pellets. Production of wood pellet is a product that in some cases may be linked to the access of sawdust in large quantities in which the sawdust supplier even may have a disposal problem and is willing to reduce their prices due to this.}
place = {Sweden}
year = {2010}
month = {Dec}
}