Hie Koppers-Totzek Atmospheric Process
Just as with moving-bed and fluid-bed processes, the first entrained-flow slagging gasification process operated at atmospheric pressure. The atmospheric pressure Koppers-Totzek (KT) process was developed in the 1950s, and commercial units were built in Finland, Greece, Turkey, India, South Africa, Zambia, and elsewhere, mostly for ammonia manufacture. The South African unit has been reported as achieving a 95% availability (Krupp-Koppers 1996). In recent years no new units of this type have been built.
The KT reactor features side-fired burners for the introduction of coal and oxygen, a top gas outlet, and a bottom outlet for the slag. The early units had a capacity of 5000Nm3/h and featured two diametrically opposed burners that were situated in horizontal truncated cones (see Figure 5-16). Later units featured four burners that increased the maximum capacity to 32,000 Nm3/h. The gas leaving the top of the gasifier at about 1500°C is quenched with water near the top of the reactor to a temperature of about 900°C so as to render the slag nonsticky before it enters a water tube syngas cooler for the production of steam. The reactor has a steam jacket to protect the pressure shell from high temperatures. A significant portion of the sensible heat is transformed into low-pressure steam in the jacket, which represents a
Figure 5-16. Koppers-Totzek Gasifier
considerable energy penalty for the process. The burners are of the premix type which means that the velocity in the burners must be quite high in order to avoid flash backs. For pressurized burners, premixing is considered too dangerous and has therefore never been applied. The slag is quenched and granulated in a water bath underneath the reactor. The water in the slag bath also provides a water seal to avoid gas escaping via the bottom of the reactor.