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The potential of Biomass Combined Heat and Power in the Wood Based Panel Industry
Edited by Alessandro Guercio
Abstract
A simple look inside our houses, schools or offices reveals the importance of the Wood Based Panel Industry (WBPI). As our cities and houses are made of concrete, so our homes and furniture are made of wood based panel.
Although much has been done in terms of product quality and healthiness, much must be still done in terms of sustainability in the WBPI.
The Biomass Combined Heat and Power (CHP) has been proven to reduce primary energy consumption and greenhouse gas emissions compared to the separate generation of heat and power. The WBPI have favorable conditions to implement the Biomass CHP, such as: familiarity with Biomass combustion systems, low cost Biomass available as process residues, simultaneous demand along the year for heat and power. The specific cost of electricity production from Biomass CHP can be competitive with the market price.
The implementation of the Biomass CHP in the WBPI can be technically possible and economically sustainable.
keywords: Wood Based Panel Industry (WBPI); Combined Heat and Power (CHP); Steam Rankine Cycle (SRC); Organic Rankine Cycle (ORC); Particle Board (PB); Oriented Strand Board (OSB); Medium Density Fiberboard (MDF); Plywood
1. Introduction
A simple look inside our houses, schools or offices reveals the importance of the Wood Based Panel Industry (WBPI). As our cities and houses are made of concrete, so our homes and furniture are made of wood based panel.
The thermal demand in the WBPI production process is covered mostly by the combustion of the production residues: waste wood, barks and wood dust. Sometimes conventional fossil fuels are used, mainly in thermal oil boiler to fed the press. The power demand is covered by the electric grid. In some cases Internal Combustion Engines fueled by natural gas are used. Rarely Biomass CHP systems are present.
The Biomass Combined Heat and Power (CHP) has been proven to reduce primary energy consumption and greenhouse gas emissions compared to the separate generation of heat and power. In the WBPI there are favorable conditions to implement the Biomass CHP, such as: familiarity with Biomass combustion systems, low cost Biomass available as process residues, simultaneous demand along the year for heat and power. The specific cost of electricity production from Biomass CHP can be competitive with the market price.
The reliable and mature technologies for Biomass CHP are the Steam Rankine Cycle (SRC) and the Organic Rankine Cycle (ORC), both associated to a reciprocating grate combustion system. The two technologies compete each-other in the Biomass CHP market in the range of size between 2 and 5 MW electric power. The SRC are fed by super-heated steam at high pressure, so a dedicated super-heated steam boiler is needed. The ORC are fed by thermal oil at 300°C, which is anyway present in the Particle Board (PB) and Medium Density Fiberboard (MDF) production process.
The specific cost of electricity production of a Biomass CHP system depends primarily from the related investment cost. It can be assumed the following specific cost of electricity production for Biomass CHP with ORC technology in the size between 2MW electric - 10 MW thermal and 5 MW electric - 25 MW thermal. In case of SRC it can be assumed roughly the same specific cost of electricity production in this range of size.
|
|
Differential investment |
Overall investment |
|
2MW electric, 10 MW thermal @ 110°C |
102€/MWh |
154€/MWh |
|
5MW electric, 25 MW thermal @110°C |
81€/MWh |
117€/MWh |
Table 1: Specific cost of electricity production for Biomass CHP with ORC ( data from: Guercio, A., Bini, R. - “Biomass-fired Organic Rankine Cycle combined heat and power”, chapter 15 of “Organic Rankine Cycle (ORC) Power System”. Edited by Ennio Macchi and Marco Astolfi. Woodhead Publishing, Elsevier)
To check whether the Biomass CHP in the WBPI can be more than technically possible, also economically sustainable, it is important to match the different production processes with the appropriate biomass CHP solutions. In this study the Particle Board (PB) and the Medium Density Fiberboard (MDF) production processes are discussed. The Plywood production, also interesting to be implemented with the Biomass CHP, has different process compared to PB and MDF, for this reason it is not treated in this study (...to be continued).
2. Particle Board (PB) and Oriented Straw Board (OSB).
The thermal demand in the PB production process is generated by the drying of the wood particles and the presses. The electric demand is generated by the dryer, presses, mills and conveyors. The dryer is typically a rotary drum dryer fed by hot gas at 400°C. The presses are feed by thermal oil at 280°C (see pics 1: Energy flow of a typical PB production process with rotary drum dryer).
No relevant cases of Biomass CHP in the PB production process have been currently reported within this scenario. To implement the Biomass CHP a change in the drying process is needed.
Some examples of low temperature belt dryer in the PB production process have been experimented with interesting results. Using low temperature belt dryers, the demanded temperature is compatible with the main technologies of Biomass CHP.
Further advantage of low temperature belt dryers compared to rotary drum dryers is the reduction of pollutant emissions, such as particulate matter and Volatile Organic Compounds (VOC), with no need of additional active filters.
A production plant of 1000 m3/day of Particle Board (PB) needs a dryer to evaporate 25 tons of water per hour, with a thermal demand for a belt dryer of 25MW in form of hot water at 110°C. The estimated power output from a dedicated Biomass CHP is 5 MW.
Both the SRC and the ORC technologies are suitable in this case. The ORC can be directly connected with the thermal oil circuit. In case of SRC a dedicated super-heated steam boiler is needed.
The specific cost of electricity production for a 5 MW electric power ORC is in the between of 81€/MWh and 117€/MWh, competitive with the market price in most of the countries (see pics 2: Energy flow of a PB production process with Biomass-fired ORC CHP and low temperature belt dryer).
3. MDF
The thermal demand of the MDF production process is generated by the drying of the wood fibers, the presses, the refiner. The electric demand is generated by the dryer, mills, refiner, presses and conveyors.
The dryer is typically a flash tube dryer fed by hot gas at 180-200°C. No relevant cases of alternative drying system with reduced temperature are currently reported.
The refiner, which transforms the wood chips in wood fibers, is fed by saturated steam at 10 bar.
The presses are fed by thermal oil at 280°C (see pics 3:Energy flow of a typical MDF production process).
A production plant of 1000 m3/day of MDF need 15MW of saturated steam at 10 bar to fed the refiner and 20 MW of hot gas at 180°C to fed the flash dryer.
Some Biomass CHP solutions can be possible:
a) A SRC producing 35 MW of heat as saturated steam at 15 bar to fed both the refiner and an indirect flash tube dryer, can co-generate 3,5 MW power output. In this case a dedicated super-heated steam boiler is required to fed the SRC (see pics 4: Energy flow of a MDF production process with Biomass-fired SRC CHP and indirect flash tube dryer).
b) An ORC producing 10 MW of heat as hot water at 110°C to preheat the make up water to the refiner and the fresh air used to mix the hot gas to a direct flash tube dryer, can co-generate 2MW power output.
The specific cost of electricity production for a 2 MW electric power ORC is in the between of 102€/MWh and 154€/MWh, competitive with the market price in some countries. Similar performances could be achieved with a conventional SRC, but in this case a dedicated super-heated steam boiler is needed (see pics 5: Energy flow of a MDF production process with Biomass-fired ORC CHP preheating the water to the refiner and the fresh air to the mixing chamber of the dryer).
4. Final remarks
The Wood Based Panel Industry (WBPI) have favorable conditions to implement the Biomass Combined Heat and Power (CHP): familiarity with Biomass combustion systems, low cost Biomass available as process residues, combined demand along the year of heat and power. The implementation of the Biomass CHP in the WBPI can be technically possible and economically sustainable.
In the Particle Board (PB) production process the Biomass CHP can be implemented changing the conventional drum dryers with a low temperature belt dryers. The low temperature belt dryers offer further advantages compared to the direct drum dryers, such as the reduction of particulate matter and Volatile Organic Compounds emissions without active filter systems.
In the Medium Density Fiberboard (MDF) production the Biomass CHP can be implemented with no modifications in the process.
The Steam Rankine Cycle (SRC) and the Organic Rankine Cycle (ORC) are reliable and mature technologies suitable to be implemented in the processes. The SRC are operated with super-heated steam at high pressure, so a dedicated super-heated steam boiler is needed. The ORC are operated with thermal oil at 300°C, which is anyway present in the PB and MDF production process.
5. Further reading
Stubdrup, K., Karlis, P., Roudier, S., Delgado Sancho, L., - “Best Available Techniques (BAT). Reference Document for the Production of Wood-based Panels”. European Integrated Pollution Prevention and Control Bureau (EIPPCB) at the European Commission's Joint Research Centre, 2016.
http://eippcb.jrc.ec.europa.eu/reference/BREF/WBP_bref_2016.pdf
Guercio, A., Bini, R. - “Biomass-fired Organic Rankine Cycle combined heat and power”, chapter 15 of “Organic Rankine Cycle (ORC) Power System”. Edited by Ennio Macchi and Marco Astolfi. Woodhead Publishing, Elsevier, 2017.
http://www.sciencedirect.com/science/article/pii/B9780081005101000156
Duvia, A., Bini, R,. Spanring, R., Portenkirchner, K., - “Application of ORC units in the MDF and Particleboard sector – General considerations and overview of the experiences of the first ORC plant in this industry installed at MDF Hallein”. Proceedings of the World Biomass Congress, Berlin, Germany, 2007.
Low-temperature belt dryer for particle board, OSB-strands, sawdust. Stela Laxhuber website.
Low-temperature belt dryer for particle board production plant in China. Swiss Combi website.
https://www.swisscombi.ch/dam/documents/downloads/publikationen/PW_0317_44_Chiping-20170216.pdf
