Gas separation – Means within gas stream for conducting concentrate to collector
Patent
1987-06-15
1988-10-18
Hart, Charles
Gas separation
Means within gas stream for conducting concentrate to collector
55 70, 55 73, 423237, B01D 5314
Patent
active
047784903
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a National Phase application corresponding to PCT/EP86/00535 filed Sept. 17, 1986 and based, in turn, upon a German National application P35 33 799.0 of Sept. 20, 1985 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a process for removal of volatile matter such as ammonia, hydrogen sulphide, and prussic acid from coke-oven plant waters by means of gas in a stripper.
BACKGROUND OF THE INVENTION
During the coking of coal, waters are produced which contain not only organic and non-volatile anorganic matter, but also volatile inorganic matter such as ammonia, hydrogen sulphide and prussic acid. These volatile inorganic compounds need to be removed to the maximum possible extent before these waters are recycled to the process for washing and scrubbing purposes, or--in the majority of cases after further treatment for removal or partial removal of other noxious matter--are discharged into the sewage. The removal of volatile inorganic matter contained in such waters is normally carried out in the coke-oven plant in stripper columns by means of steam. Aside from steam, other gases can be used as stripping gases.
German patent document DE-OS No. 14 44 972 contains a proposal to subject water from the gas collecting main of a coke-oven plant to a stripping process with an inert gas such as air, flue gas, or a blend of both for removing ammonia and phenols.
Because of the unsatisfactory proceeds from ammonia sales more and more ammonia destruction units are operated in coke-oven plants (E. TH. Herpers; Haus der Technik, lecture, Vortragsveroffentlichung 470, p. 41 to 50). These cracking units are run on vapors from stripping columns which contain mainly ammonia, carbon dioxide, and steam; generally also present prussic acid and hydrogen sulphide. While prussic acid is cracked completely, and ammonia as well, except for a small remainder, the hydrogen sulphide remains unaffected. Accordingly, the cracked gases need to be cleaned. This is normally done by cycling cracked gases after waste-heat recovery and cooling to the raw-gas cleaning process. After waste-heat recovery (steam production), the cracking gas still contains energy which, however, is qualified as of low value, and therefore is discharged (Gas- und Wasserfach, Heft 9 (1964), p. 225 to 232).
OBJECT OF THE INVENTION
The object of the invention is to provide a process which can make use of the energy contained in the tail gases of ammonia destruction plants, and which normally is discharged as waste-heat.
SUMMARY OF THE INVENTION
This object is attained in a process for removing volatile matter such as ammonia, hydrogen sulphide, and prussic acid from coke-oven plant waters by means of a stripping gas in a stripper. According to the invention, the tail gas of an ammonia destruction unit is used as the stripping gas.
The tail gas from a Claus plant can be proportioned to the tail gas of ammonia destruction unit and the tail gas from the ammonia destruction unit can be fed through a Claus plant prior to being fed to the stripper.
Advantageously, the operation temperature of the stripper is higher than 70.degree. C., preferably in the range between 70.degree. C. and 90.degree. C., while the gas/liquid ratio is held in the range between 50 and 500 m.sup.3 (STP, dry) per 1 m.sup.3, preferably between 80 and 250 m.sup.3 (STP, dry) per 1 m.sup.3. Steam can be proportioned to the stripping gas.
The process covered by this invention can be integrated cost-effectively into operations of coke-oven plants operating with an ammonia destruction unit. It is merely required to integrate a stripper into the tail gas main of the ammonia destruction unit. An additional cleaning step for the gas leaving the stripper is not required since the gas is recycled to the raw-gas cleaning process anyhow.
Surprisingly, tests have shown that stripping by means of the tail gas, even though the latter contains high concentrations of hydrogen sulphide (approx. 5-20 g/m.sup.3, STP, dr
REFERENCES:
patent: 3540189 (1970-11-01), Siewers et al.
patent: 3754376 (1973-08-01), Kent
patent: 4250160 (1981-02-01), Eakman
patent: 4486299 (1984-12-01), Kettinger
Optimum Design of Sour Water Strippers, Melin et al., Chemical Eng. process, vol. 71), Jun. 1975, pp. 78-83.
Konzeption einer modernen Nebengewinnung in einer Huttenkokerei, Vom. E. Th. Herpers, Haus der Technik Vortragsveroffentlichungen 470, Kokereitechnik, pp. 41-50.
Flachblatt fur Gastechnik und Gaswirtschaft sowie fur Wasser und Abwasser, 105 Jahrgang, Heft 9, Feb. 28, 1964, G. Choulat, Verfahren fur die Aufarbeitung des in Kokereien. und . . . pp. 225.232.
Bergwerksverband GmbH
Dubno Herbert
Hart Charles
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