Pressurized pneumatic conveying of pulverized fuels for entrained flow gasification

• Studied pneumatic conveying of pulverized fuels for entrained flow type gasifiers
• A system to continuously convey biomass, lignite, and petroleum coke was designed.
• Sparge gas allows for continuous discharge, but reduces the fuel flux.
• Fluidizing gas was shown to not affecting fuel flux.
• Comparison of existing models showed their validity for pulverized fuels studied.

A pneumatic conveying system has been designed for the continuous conveying of pulverized fuels, namely biomass (in the form of Canadian forestry waste), lignite, and petroleum coke, to an entrained flow gasification unit. All three fuels studied exhibit properties that are challenging for fluidization or conveying. The lignite and petroleum coke are Geldart class C particles and are expected to exhibit difficulties in conveying, while the biomass is a Geldart class A particle but the non-uniform particle shape and large size distribution result in pneumatic conveying challenges similar to class C particles. The conveying system consists of a blow vessel with three points of gas injection to aerate the bed of material and facilitate hopper discharge. The mass flux of each material was studied as the system parameters were varied, which included: fluidizing and sparge gas (two of the three gases aerating the hopper bed), transfer gas (gas injected directly into the solid transfer line), pressure drop, conveying gas type and transfer line diameter. Fuel fluxes were varied in a range of 450 kg/m2s to 1700 kg/m2s for all three fuels. Compared to lignite and petroleum coke conveying, biomass conveying was found to have a smaller gain in mass flux to many conveying parameters investigated. Additionally, several models for pneumatic conveying of powders were compared against the data obtained. The models were found to have various degrees of relative error, with the best fitting model having a relative error of less than 10% for all three fuels with a marginal bias towards underestimation.

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