Process for the separation of the water resulting during the cok

Details Process for the separation of the water resulting during the cok Process for the separation of the water resulting during the cok

1986-02-14

1987-12-01

Wyse, Tom

Liquid purification or separation

Processes

Preventing, decreasing, or delaying precipitation,...

210774, 210805, 55 9, C02F 500, C10K 100

Patent

active

047103027

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a process for the separation of the coal water resulting from a coking process into a small salt-rich fraction and a large salt-poor fraction and, more particularly, to a process for treating a hot gas from a coking process which contains water vapor in addition to salts or salt-forming components and tars.


BACKGROUND OF THE INVENTION

During the coking of coal, normally 140 l of coal water per ton of coal can result, approximately 100 l thereof coming from the initial moisture content of the coal and approximately 40 l resulting from the coking process itself. During coking, in addition to the volatile noxious substances like NH.sub.3, H.sub.2 S and HCN, fixed salts, mainly NH.sub.4 Cl can be produced, can be dissolved in the gas condensate, and cannot be removed again by desorptive processes. Therefore, up to now it has not been possible to reuse as service water the gas condensate resulting from such cleaning steps as dephenolizing or stripping in the still, because its salt content remains high even after the release of the fixed ammonia with lime or alkali.
Normally, in a coking plant, the hot gas at about 800.degree. C. coming from the rising main is cooled in the condenser down to the dew point of about 80.degree. C. by the gas condensates guided in closed circuit. Thus only a part of the fixed salts reach the closed-circuit condensate partially; the rest goes together with the gas into the cooler condensate, so that the separation of the gas condensate into a salt-containing and a salt-free fraction cannot take place.
However, a process for the production from a condensate free of fixed salts is known, wherein the crude gas is scrubbed between the condenser and the primary cooler, in order to eliminate the fixed salts from the gas (U.S. Pat. No. 1,747,616). An examination of this process dating from the year 1922 shows that this process has not been a success, because the fixed salts are present in the form of aerosols, which can not be eliminated through scrubbing.


OBJECT OF THE INVENTION

It is therefore the object of this invention to remove from the gas the fixed salts not eliminated at the condenser nozzles, prior to the gas condensation in the primary cooler, so that the major part of the water resulting from the coking process can be salt-free and returned, after further cleaning steps, into the system of the coking plant as service water.


SUMMARY OF THE INVENTION

This object is attained in accordance with the invention in a process in which a crude gas is cooled in a condenser and is then passed through an electrofilter prior to entering the primary cooler or coolers for further cooling. The condensate resulting from the condenser and the discharge from the electrofilter are united in the tar separator. The condensate from the primary cooler or coolers is partially returned to the condenser circuit while the balance is subjected to further treatment as a salt-poor fraction. The aqueous phase of the tar separator is partially subjected to further treatment as a salt-rich fraction.
By passing the crude gases of the coking plant through an electrofilter, between the condenser and primary coolers, the fixed salts are eliminated in proportion of over 96% from the steam-saturated crude gas.


BRIEF DESCRIPTION OF THE DRAWING

The invention is described in greater detail below with reference to the drawing. The sole FIGURE is a flow diagram which represents schematically the gas scrubbing operation downstream of the coking furnaces.


SPECIFIC DESCRIPTION

The tar and water condensed in the condenser 1 run via the duct 2 to the tar separator 3 and further over the duct 4 back to the condenser 1. The gas stream, on the other hand, exits the condenser 1 passing through the electrofilter 5 and entering the primary cooler 6. The outflow of the electrofilter 5 is directed via the duct 7 into the condenser circuit, for instance into the tar separator 3. In the primary cooler 6 a condensate is obtained which is practically free from fixed salts and

REFERENCES:
patent: 4370236 (1983-01-01), Ferguson
patent: 4382866 (1983-05-01), Johnson
patent: 4416754 (1983-11-01), Merchant et al.

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