Recovery of waste heat, from boiler in gasification plant, involves addition of dust to improve heat transfer

摘要

A dust is added to the raw gas stream, to improve heat transfer in the waste heat boiler (2) An Independent claim is included for the corresponding plant. Preferred Features: The dust is metered into the gas stream, before and/or inside the waste heat boiler, in regions of flow ahead of the heat transfer surfaces. Quench gas (5) is branched from the cooled raw gas and recycled into hot raw gases leaving the gasification reactor (1). This cools and solidifies molten suspended particles before entering the waste heat boiler. Some or all of the dust is added to the quench gas flow, before introduction into the raw gas stream. The dust is pneumatically-conveyed by carrier gas for supply into the raw gas stream and/or quench gas stream. The dust is mechanically apportioned into the flows. It is a fly ash, feedstock to be gasified, slag, limestone, marl, clay, cinder, roast pyrites, bauxite, diatomaceous earth or their mixtures. The additive stream dosed, amounts to 0.1-5 times the suspended solids in the raw gas stream. Additive mean particle size is 5-100 micro m. Fines separated from the cooled raw gas, are recycled into the gasification reactor.