Gasifier fluidised bed

Other proposals could reduce the capital and operating costs for example, a fluidised bed gasifier could increase... 

In the fluidised-bed gasifier, finely ground coal particles (<5mm) enter the top and are fluidised in upward flowing steam and oxygen, fed from the bottom of the gasifier. Fluidisation results in some carry-over of particles which are separated from the synthesis gas in a cyclone and returned to the gasifier. 

Gasification could conceivably be performed with heat from (concentrating) solar collectors, for example, in a fluidised bed gasifier maintained at 500°C. A probably more economic alternative is to use some of the biomass to produce the required heat, although this would entail environmental emissions that would have to be controlled. 

ABSTRACT This paper describes the main characteristics of a biomass gasification gas sampling system designed and built-up at CIEMAT to characterise the emissions from an atmospheric circulating fluidised bed gasifier when doing research on coal and biomass gasification. 

The aim of the sampling system presented here is to take samples from a circulating fluidised bed gasifier at pilot plant scale (200 Nm /h of gases are released). This one has been extensively operated as a combustor and it has recently been revamped to operate as a gasifier. Different feedstocks tike oak chips, orujillo" (a residue from the olive oil making industry), etc. will be gasified in the first studies. 

For tars sampled from downdraft and fluidised bed gasifiers, it has to be shown whether no solvent" can be as effective as sampling with a solvent. For the first version of the Guideline, the Group of Contractors has chosen to use a solvent. This choice will be evaluated during the running EU project. 

Ergudenler A., Ghaly E- (1992) Quality of gas produced from wheat straw in a Dual-Distributor type Fluidised bed Gasifier. Biomass and Bioenergy, 3(6), 419-430. 

Figure I The air blown fluidised bed gasifier at KTH, inner diameter 0.05m.

Figure 2 The airblown fluidised bed gasifier at TPS, inner diameter 0.2m...

To illustrate the feasibility of the proposed closed loop process, pure iron oxide FejOt was subjected to a producer gas from a 100 kW fluidised bed gasifier (reaction 1) and subsequently exposed to water vapour (reaction 2). For the reduction, Fej04 powder was placed in alumina cmcibles and heated in a tubular furnace at 900 °C and 1000 C, respectively while being exposed to a flow of producer gas for at least 25 minutes. The characterisation of the product by powder X-ray diffractometry and thermal analysis revealed that Fci. O indeed is the main product. Metallic iron and carbonaceous materials were identified as by- products. Generally, samples prepared at... 

M. Kaiser, B. Piepiorka Inert gasification of willow wood in the bench scale pressurised fluidised bed gasifier, DMT (Essen), December 1999. 

Pressurised gasification of biomass and fossil fuels in fluidised bed gasifiers, hot gas cleanup using ceramic filters and pressurised product gas combustion... 

Carbon conversion and main gas composition were similar to data provided in literature by VTT, regarding their 500 kWth pressurised fluidised bed gasifier. 

The design and the geometrical dimensions of the fluidised bed gasifier result from several boundary conditions ... 

The biomass fuelled IGCC demonstration plant at Vamamo consists of a 18 MW pressurised circulating fluidised bed gasifier, a 4,2 MW gas turbine and a 1,8 MW steam turbine. The low heat value gas produced in the gasifier is cooled in a gas cooler and cleaned in a candle filter at a temperature of 350-400°C before it is combusted in the gas turbine. The flue gas from the gas turbine is used for the production of steam in the heat recovery steam generator. The steam is superheated, together with steam from the gas cooler, and supplied to the steam turbine. Besides electricity, 9 MW heat for district heating purposes is produced. 

Tar Formation in the 18 MWth Biomass. IGCC plant in Varnamo and in a 90 kWth Pressurised Fluidised Bed Gasifier at Lund University... 

Ergudenler A. and Ghaly A. E., Agglomeration of silica sand in a fluidised bed gasifier operating on wheat straw . Biomass and Bioenergy, 4(1993) 135-147. 

Figure 14.4. Fast, internally circulating fluidised bed gasifier.

In studies of tar cracking using a separate catalyst bed, two types of tar sources are applied, one directly drawn from a biomass gasifier and the other from model compounds. According to VTTs work [12], the tar consists mainly of highly stable compounds such as benzene (60-70 wt %), naphthalene (10-20 wt %), and other polyaromatic hydrocarbons (10-20 wt %), which can amount to 15-20 g of tar/Nm in biomass gasification. So, benzene and naphthalene were used in this work as tar model compounds with a fixed concentration of 15 g/Nm (4300 ppm) for benzene and 5 g/Nm (875 ppm) for naphthalene, respectively. The gas composition used was 50 vol % N2, 12 vol % CO, 10 vol % H2, 11 vol % CO2, 12 vol % H2O, 5 vol % CH4, 4300 ppm benzene (or 875 ppm naphthalene), which is a typical composition of the product gas from a biomass fluidised bed gasifier operated with air. The reaction tests were performed under three filtration gas velocities 2.5, 4 and 6 cm/s. All experimental points were monitored for at least 60 min after the reaction reached an apparent steady state at the selected operation condition. 

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