Woodall-Duckham Process

Upon entering the gasifier, which operates at atmospheric pressure, the coal (0.25-1.5 in. [6-38 mm]) is contacted with upward flowing hot gases from the gasification zone and any moisture present in the 

The product gas from the gasifier is withdrawn at two points in the vessel the gas withdrawn between the distillation and drying zones is known as clear gas whereas the gas withdrawn near the top of the vessel is called top gas. Varying the portion of gas withdrawn through the lower tap affords a means of control of the temperature of the distillation zone. Thus, as the flow of clear gas is reduced, more hot gas is forced through the distillation zone, thus increasing the temperature. 

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The Woodall-Duckham process employs a gasifier (Figure 21.6) which is a vertical cylindrical vessel having a rotating grate in the bottom for ash removal (Howard-Smith and Werner, 1976). There are three functional zones within the reactor (1) a water-jacketed gasification zone, (2) a refractory-lined distillation zone, and (3) a refractory-lined drying zone. 

Woodall-Duckham Also called the Babcock W-D process. A process for recovering hydrochloric acid and metal oxides from spent metal chloride solutions, such as those obtained from metal pickling and ilmenite beneficiation. The liquor is first concentrated by evaporation, and then atomized in a heated spray-tower. Water evaporates from the droplets in the upper part of the tower, and chlorides are converted to oxides in the hotter, lower part. Developed by Woodall-Duckham in the 1960s by 1992, over 150 installations were in use worldwide. Now offered by Babcock Woodall-Duckham, United Kingdom. 

Data from Holly, Kenney, Schott, Inc. of Pittsburgh, PA. based on use of Woodall-Duckham coal gasification process. 

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