Thermo-chemical conversion of solid biofuels

Abstract

Biomass in general and solid biofuels in particular has gained increased attention as a renewable source of energy that can contribute to the reduction of greenhouse gas emission as well as the security of supply. Hence, it is increasingly used with an array of different technologies. These different conversion technologies are based on the principles of thermo-chemical conversion. Against this background, the goal of this paper is it to draw an overall picture of the differences and the dependencies of these different thermo-chemical conversion options. To achieve this aim, the influence of fuel composition related as well as process related parameters on the course and the products of the various thermo-chemical conversion processes are analysed and assessed in detail.

Thermochemical Conversion of Rice Straw

“…Pyrolysis serves as the core reaction of thermal conversion processes since the irreversible degradation of the biomass starts at temperatures of about 150-200 °C with the absence of oxygen. According to Pollex et al (2011), even if the feedstock is surrounded by oxygen from the air, it does not participate in the reaction since the pyrolysis gases produced during this process flow out from the biomass particles and prevent oxygen from reaching it. As the temperature goes up and some oxygen (less than the theoretical oxygen) is introduced, the process shifts to gasification.…”

Combined Heat and Power Systems for the Provision of Sustainable Energy from Biomass in Buildings

“…This may include pyrolysis, gasification, combustion or more uncommon processes like hydro-thermal conversion [1]. Additionally, fuel preparation processes like chipping, pelletizing or briquetting might occur.…”

“…The product composition depends on several parameters, including maximum conversion temperature, heating and cooling rate. [1] Gasification is the process of under-stoichiometric oxidation of fuel. This is usually obtained by using a gasification agent like air, steam or carbon dioxide.…”

“…Depending on the process and gasification agent, further product gas components include carbon dioxide, water (steam), nitrogen and several trace components. [1] Full oxidation converts the fuel completely to carbon dioxide and water (steam). This is conducted by using an oxidation agent containing enough oxygen for complete oxidation.…”

“…Depending on the process conditions, different products can be provided, including biochar or synthesis gas. [1] Depending on the product of the previous conversion step(s), especially hot flue gas and combustible syngas, the following process step consists of one or more power production technologies (or secondary conversion technologies) [2]. Typical examples for these are steam turbines or engines, Organic Rankine cycles (ORC), gas turbine or engines or fuel cells.…”