MODELING AND DESIGN OF A HIGH TEMPERATURE CHAMBER FED BY A PLASMA TORCH FOR REMOVAL OF TARS

摘要

One way of biomass and/or waste recycling is its thermochemical conversion into combustible gas. Mainly composed of CO,H_2 and CH_4, the gas may also contain varying amounts of impurities (dust, polluting products, tar or soot). Specifically, there is a tar problem: their high condensation temperature is incompatible with an industrial utilization. They can cause rapid fouling, corrosion and abrasion into turbines or engines. Proposed by EUROPLASMA, the CHO-Power process aims to generate electricity from a mixture of municipal waste and biomass using a fixed bed gasifier with conventional gas treatment. Its specificity consists of an unit called Turboplasma. This stage allows to reach very high temperature in order to obtain temperature around 1600K, and so to degrade all tars present, even heavier. Indeed, EUROPLASMA built a gasification pilot unit based on fluidized bed technology, (called KIWI) to qualify the synthesis gas produced. TURBOPLASMA pilot scale will be installed there. The objective of this work is the design of this high temperature stage thanks to numerical modeling. Reaction scheme used previously [4] to modelize tar degradation in the Turboplasma of CHO-Power, has been improved : a discrete phase modeling has been added providing a better view of the TURBOPLASMA internal behavior. Indeed, char particles from syngas can significantly change the reactor performance. This study shows that char particles react primarily with the H_2O and CO_2. Char gasification takes place in areas of high velocity and temperature gradient. Increased understanding of aerodynamics inside the reactor allows a better estimate of the overall performance of the reactor. Performance evaluation of the reactor is based on a set of parameters such as levels of heat loss, velocity gradient, mixing quality, residence time.