JP2016112516A - Method for treating excess ammoniacal liquor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating excess ammonia liquor continuously and stably over a long period of time.SOLUTION: A part of excess ammonia liquor generated during purifying coke oven gas is introduced into a decompression type ammonia stripper 1 and subjected to vacuum distillation, ammonia is removed from a part of the excess ammonia liquor and ammonia-containing steam distilled from the decompression type ammonia stripper 1 is introduced into a condenser 11, followed by cooling and condensation. At this time, the ammonia-containing steam is condensed while spraying the other part of the ammonia liquor to the vicinity of an introduction port into which the ammonia-containing steam is introduced of an inner surface of the condenser 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for treating surplus water that is generated during the purification of coke oven gas.

  The coke plant purifies coke oven gas with ammonia water circulating between the dry main and tar decanter of the coke oven. Water "). The surplus hot water (hereinafter sometimes referred to as “surplus water”) may be treated to remove ammonia by a vacuum distillation facility.

  When the surplus water is treated, the condenser that condenses the vapor distilled from the distillation tower is blocked by the components contained in the surplus water, and the vacuum distillation equipment can be operated continuously and stably over a long period of time. Since there is a possibility that it cannot be performed, a technique for preventing clogging of the condenser has been proposed. For example, Patent Document 1 proposes a method in which condensation is performed in two stages, upstream and downstream, and downstream condensation is performed by two condensers, a switchable main condenser and a precondenser. . However, the method disclosed in Patent Document 1 requires a total of three condensers, which increases the initial cost of the vacuum distillation facility.

JP 2005-239934 A

  Then, this invention makes it a subject to solve the trouble which the above prior arts have, and to provide the processing method of the surplus safe water which can be operated continuously and stably over a long period of time.

  In order to solve the above-described problem, the surplus water treatment method according to one aspect of the present invention includes introducing a part of surplus water generated during refining of coke oven gas into a vacuum distillation column and performing distillation under reduced pressure. Introducing ammonia-containing steam from the inner surface of the condenser, including removing ammonia from a portion of the water and introducing ammonia-containing steam distilled from the vacuum distillation column into the condenser to cool and condense The gist is to condense the ammonia-containing vapor while spraying the other part of the surplus water in the vicinity of the mouth.

  According to the present invention, surplus water can be treated continuously and stably over a long period of time.

It is a flowchart explaining one Embodiment of the processing method of the surplus safe water of this invention.

  An embodiment of the present invention will be described. In the coke factory, hot water is generated because the coke oven gas is refined with ammonia water circulating between the dry main of the coke oven and the tar decanter. Of the generated hot water, surplus water is treated by a vacuum distillation facility to remove ammonia.

In the surplus water treatment method of this embodiment, a part of surplus water generated during the purification of coke oven gas is introduced into a vacuum distillation column of a vacuum distillation facility, and ammonia is removed by vacuum distillation. And the ammonia containing vapor | steam distilled from the vacuum distillation tower is introduce | transduced into the condenser of a vacuum distillation equipment, is cooled, and is condensed.
At this time, components such as tar oil contained in the ammonia-containing vapor may solidify or precipitate in the vicinity of the introduction port where the ammonia-containing vapor is introduced on the inner surface of the condenser, and the condenser may be blocked. .

  However, in the surplus water treatment method of the present embodiment, among the surplus water generated at the time of refining the coke oven gas, the other part that was not introduced into the vacuum distillation tower was replaced with the ammonia-containing steam on the inner surface of the condenser. As the ammonia-containing vapor is condensed in the condenser while spraying in the vicinity of the inlet where the oil is introduced, the clogging cause substance derived from tar oil etc. contained in the ammonia-containing vapor is Washed. Therefore, the vacuum distillation equipment can be operated continuously and stably over a long period of time while avoiding blockage of the condenser, and surplus water can be treated.

  According to the surplus water treatment method of this embodiment as described above, for example, a plurality of condensers are not required and one condenser is sufficient, so that the initial cost of the vacuum distillation facility is small. In addition, since it is not necessary to operate the condenser at a temperature at which the solidification and precipitation of the clogging cause substances do not occur in order to avoid the clogging of the condenser, the capacity (displacement volume) of the vacuum evacuation device (for example, vacuum pump) of the vacuum distillation equipment ) May be low. Furthermore, since surplus water is processed by vacuum distillation, it is not necessary to make the surplus water in a vacuum distillation tower high temperature, and it can process at low energy cost.

  Note that the temperature of the surplus water to be sprayed may be a temperature at which the temperature difference from the top temperature of the condenser is 10 ° C. or less. If it does so, since the sprayed surplus water is easy to absorb ammonia and acidic gas, the quantity of the gas introduce | transduced into the vacuum exhaust apparatus of a vacuum distillation equipment is reduced. Therefore, the capacity | capacitance (evacuation amount) of the vacuum exhaust apparatus of a vacuum distillation equipment can be reduced. If the temperature of the surplus water to be sprayed is too high, the sprayed surplus water will not easily absorb ammonia or acid gas. On the other hand, if the temperature of the surplus water to be sprayed is too low, there is a possibility that the clogging cause substance is deposited in the sprayed surplus water.

Next, the surplus water treatment method of the present embodiment will be described with reference to a more specific example (see FIG. 1).
Part of the surplus water produced during the refining of the coke oven gas is introduced through the path 2 into the reduced pressure ammonia stripper 1 of the reduced pressure distillation facility (corresponding to the “reduced pressure distillation column” which is a constituent of the present invention). . The inside of the decompression type ammonia stripper 1 is decompressed by a vacuum pump 16.

  The surplus water introduced into the depressurized ammonia stripper 1 is sent from the bottom of the tower to the reboiler 3 via the path 6 by the pump 5, heated by heat exchange, and then the tower of the depressurized ammonia stripper 1 through the path 6. Returned to the bottom. As a result, the heated surplus water becomes steam under reduced pressure, and the ammonia-containing steam containing ammonia and acidic gas at a high concentration reaches the top of the reduced-pressure ammonia stripper 1. As a result, surplus water is stripped, and ammonia and acidic gas are removed from the surplus water. Excess ammonia water from which ammonia and acid gas have been removed is extracted from the bottom of the reduced pressure ammonia stripper 1 by a pump 8 and fed via a path 9.

The heat source of the reboiler 3 is not particularly limited, but hot and cold water circulating between the dry main and the tar decanter of the coke oven may be used. That is, the circulating hot and cold water may be introduced into the reboiler 3 via the path 4 to serve as a heat source.
The ammonia-containing vapor removed from the surplus water is distilled from the top of the reduced pressure ammonia stripper 1 and introduced into the condenser 11 of the reduced pressure distillation facility via the path 10. A large number of tubes (not shown) are arranged in the condenser 11 along the vertical direction, and ammonia-containing vapor is introduced into these tubes. And ammonia containing vapor | steam condenses by being cooled with the cooling water which flows the exterior of a tubular body.

  At this time, the other part of the surplus water generated at the time of refining the coke oven gas is sprayed on the portion 11a near the introduction port into which the ammonia-containing vapor is introduced on the inner surface of the condenser 11. For this reason, the ammonia-containing vapor is condensed while the surplus water is sprayed onto the vicinity 11a. Since the clogging cause substance derived from tar oil or the like contained in the ammonia-containing vapor is washed by the surplus water spray, clogging of the condenser 11 is suppressed. Surplus water for spraying is cooled to 40 ° C., for example, and introduced through a path 12 connected to a portion of the condenser 11 upstream of the tube.

  Ammonia water obtained by condensing the ammonia-containing vapor is extracted from the bottom of the condenser 11 by the pump 18 and fed through the path 17. This ammonia water can be used as circulating hot water, or it can be distilled to obtain highly pure ammonia. In addition, the ammonia-containing vapor that has not been condensed is discharged from the bottom of the condenser 11 via the path 15 by the vacuum pump 16 and sent to the deammonia facility of the coke oven gas purification facility for processing.

〔Example〕
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The reduced-pressure distillation equipment shown in FIG. 1 was used, and surplus water was treated in the same manner as in the above embodiment (Example). The amount of surplus water introduced into the reduced pressure ammonia stripper 1 is 100 tons / h. The composition of this surplus water is 8000 ppm of ammonia, 1600 ppm of hydrogen sulfide, 8000 ppm of carbon dioxide, 800 ppm of hydrogen cyanide, and the balance is water.

The reboiler 3 was introduced with 77 ° C. hot and cold water (hot and cold water circulated between the coke oven dry main and the tar decanter), thereby supplying a surplus of low water with a calorific value of 10,000 Mcal / h. The operating conditions of the decompression type ammonia stripper 1 are as follows.
Pressure at the bottom of the tower: -70 kPaG
Tower bottom temperature: 70 ° C
Pressure at the top of the tower: -71 kPaG
Tower top temperature: 67 ° C
Surplus water spray rate: 10 Nm ³ / h
Surplus water temperature to spray: 69 ℃
The operating conditions of the condenser 11 are as follows.
Cooling temperature: 40 ° C

  As a result of treating surplus water under such conditions, the ammonia concentration of the treated surplus water discharged from the route 9 was 600 ppm. In addition, as a result of continuous operation of the vacuum distillation facility for one month, no significant decrease in the heat transfer performance of the condenser 11 was observed, and the vacuum distillation facility was operated continuously and stably over a long period of time. Water treatment could be performed. From this result, it can be seen that the condenser 11 was not blocked.

  On the other hand, the surplus water treatment was performed in the same manner as in the above example except that the surplus water was not sprayed (comparative example). As a result, the heat transfer performance of the condenser 11 gradually declined after about one week, and after one month, only about 80% of the initial amount of surplus water could be treated. From this result, it can be seen that the condenser 11 is blocked. The ammonia concentration in the treated surplus water discharged from the route 9 was 600 ppm.

1 Depressurized ammonia stripper (vacuum distillation tower)
11 Condenser

Claims (2)

Introducing a portion of surplus water generated during refining of coke oven gas into a vacuum distillation column and performing distillation under reduced pressure, removing ammonia from a portion of the surplus water and containing ammonia distilled from the vacuum distillation column Including the step of introducing steam into the condenser to cool and condense,
The surplus water is obtained by condensing the ammonia-containing steam while spraying the other part of the surplus water on the inner surface of the condenser near the inlet to which the ammonia-containing steam is introduced. Processing method.   2. The surplus water treatment according to claim 1, wherein the temperature of the other part of the surplus water is such that the temperature difference from the temperature at the top of the condenser is 10 ° C. or less. Method.

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