Abstract: A slagging gasifier has a hearth comprising an annular solid cast structure formed from a high thermal conductivity metal such as copper and shaped to fit above a slag tap of the gasifier. The hearth is provided with one or more integrally formed passageways for circulating a coolant liquid therethrough and has an upper tundish surface with a slope of at least 10.degree. to the horizontal (preferably between 25.degree. and 45.degree.), across which tundish surface the molten slag flows downwardly and inwardly towards to slag tap. The annular structure may be formed from at least three sector-shaped cast parts secured together in situ in the gasifier.

Abstract: A method of operating a gasifier having at least four, and preferably eight, tuyeres, so as to bring about a rapid turndown from full operational loading to a relatively lower operational loading without the risk of either a temporary or permanent loss of a tuyere. The gasifying medium is arranged to be supplied to the tuyeres at either a first velocity and loading or a second, lower, velocity and loading and in carrying out the method the gasifying medium supplied to some or all of the tuyeres is changed abruptly from the first to the second velocity and loading at selected frequent intervals, in a predetermined pattern, so that a selective pulsing operation of the tuyeres occurs to bring about the required reduction in loading.

Abstract: A removable annular hearth member, shaped to fit over the slag outlet member of a slagging gasifier, comprises a cast body of high thermal conductivity having integral liquid coolant passageways, the central openings of the annular hearth member and slag outlet member being arranged in vertical alignment for the discharge of slag, and the lower portion of the hearth member opening having a lip or beak extending downwardly so as to form a sealed joint with the slag outlet opening whereby in operation of the gasifier to prevent preparation of molten slag therebetween.