DISCUSSION WITH KOPPERS
The discussion with Koppers concerned the difficulties with the Louisiana unit and Totzek’s views on how to overcome these difficulties. Many of Totzek’s current views are in direct opposition to some of his original ideas which form the basis of the Koppers design. For example, Totzek now thinks that the presence of steam at the instant of combustion is essential and recommends leaving as much as 15% H2O in the coal, whereas, formerly he was interested in forming an intensely hot high temperature zone for primary reaction of O2 and coal with subsequent reaction of the products with steam.
In Totzek’s opinion the ungasified residue from the Louisiana unit in tests that he witnessed could not have attained a temperature greater than 600 to 700°C. as indicated by the residual volatile matter. This is an indication of chilling and is one of the reasons why Totzek favors homogeneous mixing of reactants.
Totzek’s tests have shown that it is easy to get 80-85% carbon utilization, but the last 10% is exceedingly difficult to convert. According to Totzek, this conversion can be effected by using excess steam or by having excess carbon present and recycling or using the residue in another process. Totzek favors the use of excess carbon in the reactor. Under conditions where 90-95% of the carbon is gasified, the handling of the residue in settling tanks, etc., presents no difficulties.
Regarding recycling of residue, Totzek points out that it should be very reactive since it is a low temperature coke and should, therefore, be easier to gasify than the original coal.
Totzek has done recent experimental work in a unit having a capacity of 50 kg./hour. We did not see this unit. Work has been done with brown coal containing 15% H2O and 20% O2. At a 1200°C. gasification temperature and with a tail gas temperature of 900°C., 92-94% of the carbon was gasified when making a gas containing 13% CO2, 34.6H2, and 52.4% CO. With steinkohle the carbon utilization was 80-85%. According to Totzek, 300 cu. ft. of O2 were used per M cu. ft. of CO+H2 when producing gas from brown coal.
As indicated in discussions with Charbonnage de France, the Koopers Company is building a gasifier for them. According to Koppers, this unit will gasify 100 metric tons/day, whereas the French stated 50 tons/day. The dimensions of this unit are shown in figure 5. It is apparently designed for a throughput of 10 lb. coal/cu.ft./hour.