Design Features and Performance Data of a New 400 kWel Biomass Gasification Power Plant of Downdraft Type

Abstract

A   new   biomass-gasification   power   plant,   of   medium-size downdraft  type,  is  presented  and  discussed  in  its  design  features and  performance  characteristics.  Its  configuration  and  overall dimensions,  initially  conceived  for  800  kWel,  were  recently  re-tuned,  from  a  functional  point  of  view  and  on  the  base  of  a parallel theoretical analysis, by decreasing to about 400 kWel the former design power level.  This provision, jointly  with the basic design  choice  of  adopting  a  long  and  amply  dimensioned  inlet-biomass  thermal  pretreatment  section,  turned  out  quite  effective in achieving high gasification temperatures and a low-tar content in  the  produced  gas  at  fuel-to-air  ratios  well  below  the  usually imposed,  to  the  advantage  of  the  heat  value  of  the  product-gas gas.  The  paper  discusses  the  numerical  analysis  results  which helped   to  properly   adjust   the  operational   parameters   of   the gasifier  and  then  presents  the  experimental  performance  data  of the    overall    power    plant    including    biomass    consumption, gasification   temperatures,   gas   production,   composition   and pollutants  content,  cold-gas  conversion  efficiency  and  global electric  efficiency.  Special  care  is  devoted  to  investigating  the issue of a significant production of carbon-containing particulate matter  in  the  product  gas,  which  turns  out  made  up  of  char  and fixed carbon much more than of tar species.