Among the low temperature biomass thermochemical processes slow pyrolysis producesa solid material, the char, and, at the same time, gaseous and liquid energy carrers. Interest in char production comes from its numerous applications: fuel in traditional and advanced power generation facilities, fertilizer and carbon sink, activated carbons precursor, filler in wood and polymer composites, contaminants adsorbent in wastewater and soil, catalyst or adsorbent in gas cleaning, catalyst for syngas conversion to liquid hydrocarbons and bio-diesel production [1]. Since pyrolysis is an endothermic process, feeding the gas stream produced from pyrolysis to a subsequent combustion stage provides for a heat recovery, and this could allow to operate in autothermal regime, thus to have a system able to produce continuously char from biomass. Pyrolysis gas consists of a homogeneous gaseous phase strongly diluted in CO2 and water vapor. A MILD combustion process is particularly suitable because in this process fuel is supplied under high dilution (fuel con-centration outside the flammability limits) and strong preheating (higher temperature than self-ignition one) conditions [2]. One solution for the integrated system provides for the recirculation of the combustion exhaust gas to the pyrolysis reactor, so that it acts as carri-er gas and heats the biomass directly. At our knowledge data about the effect of the pres-ence of combustion exhaust gas on the characteristics of char produced under slow pyroly-sis conditions are scarce in literature. On the contrary, the effect of the presence of a reac-tive agent (CO2, water vapor) during biomass one-step pyrolysis/activation treatment at 700-900°C is well-known [3]. In the present work, slow pyrolysis of poplar branches in presence of N2, CO2, water vapor and a model mixture whose composition is representa-tive of the output from the combustion unit was carried out to understand the effect of the carrier gas on the characteristics of char. Three final pyrolysis temperatures, 450, 480 and 550 °C were investigated because this is the desired temperature range for the pyrolysis unit in the integrated system.
Effect of the presence of combustion exhaust gas on the characteristics of char produced by slow pyrolysis of biomasses
P Giudicianni;R Ragucci
2017
Abstract
Among the low temperature biomass thermochemical processes slow pyrolysis producesa solid material, the char, and, at the same time, gaseous and liquid energy carrers. Interest in char production comes from its numerous applications: fuel in traditional and advanced power generation facilities, fertilizer and carbon sink, activated carbons precursor, filler in wood and polymer composites, contaminants adsorbent in wastewater and soil, catalyst or adsorbent in gas cleaning, catalyst for syngas conversion to liquid hydrocarbons and bio-diesel production [1]. Since pyrolysis is an endothermic process, feeding the gas stream produced from pyrolysis to a subsequent combustion stage provides for a heat recovery, and this could allow to operate in autothermal regime, thus to have a system able to produce continuously char from biomass. Pyrolysis gas consists of a homogeneous gaseous phase strongly diluted in CO2 and water vapor. A MILD combustion process is particularly suitable because in this process fuel is supplied under high dilution (fuel con-centration outside the flammability limits) and strong preheating (higher temperature than self-ignition one) conditions [2]. One solution for the integrated system provides for the recirculation of the combustion exhaust gas to the pyrolysis reactor, so that it acts as carri-er gas and heats the biomass directly. At our knowledge data about the effect of the pres-ence of combustion exhaust gas on the characteristics of char produced under slow pyroly-sis conditions are scarce in literature. On the contrary, the effect of the presence of a reac-tive agent (CO2, water vapor) during biomass one-step pyrolysis/activation treatment at 700-900°C is well-known [3]. In the present work, slow pyrolysis of poplar branches in presence of N2, CO2, water vapor and a model mixture whose composition is representa-tive of the output from the combustion unit was carried out to understand the effect of the carrier gas on the characteristics of char. Three final pyrolysis temperatures, 450, 480 and 550 °C were investigated because this is the desired temperature range for the pyrolysis unit in the integrated system.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
