Thermochemical Conversion

Thermo-Chemical Conversion of Biomass – a Retrospective and a Prospective

From the article:

The work on thermo-chemical conversion of biomass was initiated at the Institute with the financial support from the Karnataka State Council for Science and Technology in 1981. During the first five years, one of the key question addressed was: Can a 3.7 kWe gasifier be built to produce engine consistent quality gas from woody biomass – even though small systems are prone to unfavorable thermal conditions? Studies showed that this question could be answered in the positive. The period 1985-90 was characterized by the demonstration of the possibility of new technologies that emerged from innovations in the laboratory. Soon there was a need to address requests for medium capacity systems. An automated 100-kWe gasifier with data acquisition system was set up at Port Blair. This system operated from 1990 led to several modifications and improved versions. The period 1990 – 1995, was studded with ‘crossing several milestones’ related to ‘technology improvement’ and device longevity. The problems addressed during this period related to enhancing reactor life using ceramics. These efforts led to emergence of landmark reactor technology – rammed mass technology and hard high allumina tile face.

The period of 1995 to 2000 was characterized by great interest from the Ministry of Non-conventional Energy Sources (MNES) and some interest from international groups, broadening the biomass feedstock types, adaptation to various type of engines, etc. The principal questions addressed were: Can feed stock range be enhanced to include other agro residues and urban solid waste. Can turbo-charged engines be run on producer gas without any technical problems? Can the issues related to gas engines be understood and technology elements built here. These led improving the scientific base. In doing so, many scientific questions were tackled. This period was also characterized by scientific developments involving, (a) modeling of combustion of individual biomass in specific geometric like sphere, (b) reactor as thermo-chemical device, (c) reactor design, (d) producer gas as a combustible medium, (e) physics of flame propagation vis-à-vis smooth burning in a high compression engines, heat balance and combustion in CI and SI engines has led to better science and engineering. This vast experience has enabled evolving, designing; field-testing and installing a large number of open top reburn gasification systems from 3 kW – 1 MWe. Technological improvements on the reactor were accompanied by improvements in the gasifier subsystems also. Manufacturing process also has been examined to ensure good quality assurance. These studies have led to,

a. interpreting gasification process as a two staged combustion process

b. using a staged conversion process to achieve clean combustion-(high efficiency and low pollutant emission)

c. adapting technology to low grade fuels like, agro wastes (sugar cane trash, agro residues), weeds (ipomea with high alkaline ash) and poorly segregated urban solid wastes.