Torrefied biomass fuels as a renewable alternative to coal in co-firing for power generation

journal article in Web of Science

English

This study aims to assess the torrefaction of biomass as alternative renewable energy fuel to coal during co-firing. It was evaluated that torrefaction improves biomass grindability to such an extent that it can be used in coal mills with coal in co-firing without capital intensive modification. Torrefaction of beech wood was performed on a batch scale reactor at three different temperatures (200, 250 and 300 degrees C) with 30 min of residence time. The chemical structural changes in torrefled biomass were investigated with binding energies and FTIR (Fourier transform infrared) analysis. Monocombustion and co-combustion tests were performed to examine the combustion behaviour regarding flue gas emissions (CO, NOx and SO2) at 0.5, 1.5 and 2.5 m distance from the burner opening along with fly ash analysis. The FTIR and binding energies showed that lignin hardly affected during light torrefaction while hemicellulosic material was significantly depleted. The Hardgrove grindability index (HGI) was calculated with three methods (DIN51742, IFK and ISO). The medium temperature torrefled biomass (MTTB) yields HGI value in the range of 32-37 that was comparable with HGI of El Cerrejon coal (36-41). A slight change in temperature enabled the torrefled beech wood to be co-milled with coal without capital intensive modification and improved grindability. Comparing the combustion behaviour of single fuels, low temperature torrefled biomass (LTTB) produces less amount of NOx (426 mg/m(3)), CO (0.002 mg/m(3)) and SO2 (2 mg/m(3)) as compared MTTB and raw beech wood. In the case of co-combustion, it was found that blending of coal with raw biomass does not show a stable behaviour. However, premixing of 50% of coal with 50% of torrefled biomasses (MTTB and LTTB) gives most stable behaviour and reduces NOx almost 30% and SOx up to almost 50% compared to coal. The fly ash contents analysis proved that K2O contents much decreased during co-firing of coal and torrefled fuels that could cause ash related issues during combustion of raw biomass. (C) 2020 Elsevier Ltd. All rights reserved.

Renewable energy; CO2 emissions; Torrefaction; Biomass; Hardgrove grindability index; Co-combustion; Emissions profile and power plant

Sher, F., Yaqoob, A., Saeed, F., Zhang, S., Jahan, Z., Klemeš, J.J

15. 10. 2020

PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND

PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND

0360-5442

Energy

209

United Kingdom of Great Britain and Northern Ireland

118444

118444

13

https://www.sciencedirect.com/science/article/pii/S0360544220315528?via%3Dihub