28.     --------------. [ALLNER, W.] [Brown Coal Gas for City and Synthetic Purposes – The Kassel Parallel Current Chamber, Bubiag-Didier System.]  Gas- u. Wasserfach, vol. 78, 1935, pp. 438-456; Tech. Blätter, vol. 25, 1935, p. 392; British Chem. Abs., 1935, B, p. 756; Chem. Abs., vol. 29, 1935, p. 6731.

                Brown coal or brown-coal briquets are carbonized in vertical chambers heated externally to 1,000°-1,300°.  The brown coal gradually passes down through the chamber, and the distillation products are cracked by passing down through the hot coke before being removed through outlets at various heights.  The coke in the lower part of the chamber is steamed to generate water gas, which mixes with the gas produced by carbonization.  Provision is made for the continuous removal of the coke, which is used to generate producer gas for heating the chambers.  The yield and quality of the gas may be varied within wide limits by adjusting operating conditions, so as to produce a gas of 450 B.t.u. per cu. ft. or higher, or a gas containing less than 4% CH₄ suitable for synthetic purposes.  Gas similar in composition to coal gas may be made if the excessive amount of CO₂ is washed out.  This is accomplished by means of a 20%, K₂CO₃ solution, the regeneration of this solution requiring about 1 lb. of steam per 3 cu. ft. of CO₂.  Possible uses for CO₂ are discussed, and costs for its removal are given.  Losses of the wash solution are negligible, less than 20% per yr.  The tar is similar to high-temperature tar, but the yield is much lower.  The light-oil content is about 0.095-0.16 gal. per 1,000 cu. ft., but this may be increased by introducing petroleum oils or brown-coal tar into the chamber during carbonization.  Gas manufactured by this process has been used successfully in ordinary gas-burning appliances both alone and mixed with the ordinary city gas and the experimental plant has been in continuous operation since October 1934, covering 1/5-1/7 of the Kassel gas requirements.  Cost data are given for German conditions.  A laboratory apparatus for carbonizing brown coal is described, which permits comparison of various brown coals.