JPS609550B2 - Method for recovering waste heat from coke oven gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for effectively recovering low-temperature waste heat from currently discarded coke oven gas without significantly changing coke oven gas cooling equipment.

Conventionally, as shown in the flow sheet of FIG. 1, about 100 qo of coke oven gas generated from a coke oven 1 is cooled down to about 80 qo by gas liquid 4 sprayed in a 0 dry main 3.

It is then cooled down to about 35q0 by an indirect gas cooler 6 and/or a direct gas cooler 7. In the direct gas cooler 7, diluted diluted water 10 cooled by seawater in diluted diluted water cooler 8 or cooled by circulating water 9 from a cooling tower is circulated.

In this way, the heat retained in the coke oven gas 2 is transferred to the gas liquid 4, seawater 9, or cooling water tower circulating water 9, and then radiated into the atmosphere.
It is being released outside the system by releasing warm seawater. 0 As mentioned above, not only is the huge amount of heat possessed by coke oven gas not used at all, resulting in a waste of valuable energy resources, but if seawater is used as cold soot, a large amount of warm seawater will be discharged. It may cause pollution such as red tide.

Here, as an example of the retained heat of coke oven gas, the heat balance in the case where coke oven gas is generated at 13,500 m3/hour (H) is as follows.

(i) In the dry main, coke oven gas → atmospheric heat radiation 8,000,000 KCal/day (ii) In the gas circulation line, coke oven gas → gas liquid → atmospheric heat radiation 15,000,000 〃 Side In the pipe and direct gas cooler, coke Furnace gas → seawater → warm seawater heat radiation - 〆 74,000,000 〃 Diluted ammonium water total 97,000,000 〃 If 30 pm seawater is used as cold soot, 32 plates of warm seawater at about 53℃ will be discharged per day. become.

On the other hand, in coke factories, a large amount of gas purification equipment including absorption towers, stripping towers, etc. and waste liquid treatment equipment are used to remove or recover harmful substances such as hydrogen sulfide, hydrogen cyanide, and ammonia contained in coke oven gas. Since equipment that requires heat coexists, it is desired to make effective use of the heat retained in coke oven gas.In response to this demand, the present invention has been developed to efficiently utilize coke oven gas cooling equipment without significantly changing the current coke oven gas cooling equipment. This relates to a method for recovering waste heat from coke oven gas, which aims to effectively utilize the heat retained in the oven gas, and is a method for recovering waste heat from coke oven gas, which is a poor absorption method from which harmful or useful substances have been removed from the dispersion tower of coke oven gas purification equipment. The liquid is used for cooling coke oven gas, the heat-exchanged poor absorption liquid is returned to the stripping tower, and the rich absorption liquid containing harmful or useful substances from the absorption tower of the coke oven gas purification equipment is heated. By supplying V to the stripping tower, harmful substances or useful substances are separated in the stripping tower, and as a poor absorption liquid, the liquid is circulated for coke oven gas cooling and absorption*, and is used in the above-mentioned method of the present invention. I was able to achieve my goal.

In this case, a process that involves a dissipation operation in a vacuum and at low temperatures is introduced into the coke oven gas purification equipment, such as the vacium carbonate method for hydrogen sulfide removal, or a waste liquid treatment process that involves concentration operations at low temperatures such as vacuum evaporation. The indirect gas cooler can be used as a reboiler and/or heater by introducing a boiler and/or a radiator to use the hot gas liquid circulating in the dry main as a heat source. Make use of it. Furthermore, by insulating the gas liquid circulation piping as necessary, it is possible to improve the heat utilization efficiency.

Next, the present invention will be explained in detail by way of examples.

Embodiment 1 (When the present invention is used in hydrogen sulfide removal equipment) As shown in FIG. 2, an example of its implementation, the coke oven gas 2 from the coke oven 1 is transferred to the dry main 3 as in the case of FIG. It is cooled to about 80 qo by the gas liquid 4 sprayed at
It is cooled to about 35q0. The indirect gas cooler 6 is used as a reboiler by passing the poor absorption liquid 15 from the bottom of the harmful substance dissipation link 12 instead of the conventional seawater or cooling tower circulating water. If the amount of heat is insufficient, a boiler 17 is installed using hot gas liquid from the dry main 3 as a heat source. In this way, the poor absorption liquid 15 that has exited the indirect gas cooler 6 is sent to the harmful substance dispersion tower 12 for heating, and a portion of the heated water that has exited the harmful substance dispersion tower 12 is returned to the indirect gas cooler 6 and the reboiler. 17 and used as described above. The remainder is sent to the absorption tower 111 via the heat exchanger 14 and the absorption liquid cooler 13, and is used for absorbing harmful substances from the coke oven gas. The rich absorption liquid 16 that has absorbed harmful substances is sent to the harmful substance dispersion tower 12 and is heated by the heated circulation water of the poor absorption liquid from the indirect cooler 6 to remove harmful substances, such as hydrogen sulfide 1 in this case.
8 is dissipated. In this case, install heat insulation on the gas liquid circulation piping as necessary. When the present invention was used as described above to treat 13,500 m3/day of coke oven gas containing hydrogen sulfide at 6.16 m3/day, the coke oven gas was a gas liquid dispersed in the dry main at 200 m3/day. 81qo
cooled to.

The gas liquid, which took heat from the coke oven gas, radiated heat into the atmosphere and the temperature reached approximately 75:00. Two of the five indirect gas coolers in constant operation were used as reboilers.

As a result, the poor absorption liquid at the bottom of the stripping tower is 1734 m3/day.
3qo to 6 was heated to 0, while coke oven gas was cooled from 81qo to 6ro.

(The other three units were operated as ordinary indirect gas coolers.) In addition, a boiler using gas liquid as a heat source was installed to compensate for the lack of heat in the hazardous substance diffusion tower and to adjust the heat.
417 m3/day of the poor absorption liquid at the bottom of the harmful substance dispersion tower was heated from 0 to 65 degrees Celsius through 100 plates of gas liquid of 3/day. The heated poor absorbent liquid has a temperature of about 100 Torr (To
The mixture was returned to the bottom of the hazardous substance stripping tower operated in a vacuum and the pressure was reduced to generate steam, thereby dissipating hydrogen sulfide from the V-rich absorption liquid supplied from the top of the hazardous substance stripping column.
The gas coming out of the Z indirect gas cooler was cooled to 3FC with diluted water circulated in the direct gas cooler. As a result, 80-90% of hydrogen sulfide was removed from the coke oven gas, and concentrated hydrogen sulfide gas of 40-6% by volume was recovered. There was no consumption of steam due to the high release of harmful substances. In the normal case without the use of the present invention, approximately 38 tons/hour of steam was required.

In addition, the amount of seawater used to cool coke oven gas could be reduced by 100 h3/hour.
2 Example 2 (When the waste heat of coke oven gas of the present invention is used in a concentration treatment facility for activated sludge treatment wastewater) Third
As an example of its implementation is shown in the figure, the coke oven gas 2 from the coke oven 1 is cooled to about 80°C by the gas liquid 4 sprayed by the dry main 3, as in the case of Fig. 1.
The gas is then passed through an intervening gas cooler 6 to be cooled.

The indirect gas cooler 6 is used as a heater by passing activated sludge treated wastewater 20 from the cooling tower or vacuum evaporator 21 instead of seawater or circulating water from the cooling tower. The heated activated sludge treated wastewater 20 exiting the indirect gas cooler 6 is fed to a cooling tower or a vacuum evaporator 21 and recycled for evaporation of the activated sludge treated wastewater 19. In this case, the material of the heat exchanger tubes of the indirect gas cooler 6 is changed depending on the corrosivity of the wastewater. If the amount of heat for concentration in the cooling tower or vacuum evaporator 21 is insufficient, a waste liquid heater 22 using the hot gas liquid 4 from the dry main 3 as a heat source is installed to circulate a part of the activated sludge treated waste water 20. . Heated activated sludge treated wastewater 20' cooling tower or vacuum evaporator 21
The water is concentrated and cooled by evaporation of moisture, and is again circulated to the indirect gas cooler 6 and the waste liquid heater 22.

The concentrated wastewater is extracted from the system and undergoes final treatment such as incineration or crystal separation (not shown). Wastewater 61.8% is treated with activated sludge from surplus ammonium water generated in a coke factory that generates 135,000 m3/day of coke oven gas.
h3/day were treated with the invention.

The properties of the activated sludge treated wastewater are shown in Table 1 together with the concentrated wastewater. Three of the five indirect gas coolers in continuous operation were used as waste liquid heaters, and 390 ml of wastewater was heated to 54 qO by passing through the indirect gas coolers for 16 h3/day.

The coke oven gas was cooled from 81°C to 520°C. The other two were used as conventional indirect gas coolers. 54℃
The wastewater that has been heated to 35°C is led to a natural draft cooling tower 21 where it is cooled to 35°C by evaporating moisture into the air.
It was concentrated and circulated to the indirect gas cooler 6 again.

As a result, in the natural draft cooling water tower 21. 2 tons/
When the water content evaporates, the concentrated wastewater with the properties shown in Table 1 becomes 7.3
Extracted h3/day.

This concentrated wastewater could be easily incinerated by the usual submerged combustion method or waste liquid combustion method, and the wastewater could be completely eliminated.

In this example, all the heat necessary for concentrating the wastewater was provided by the retained heat of the coke oven gas.

If steam is used, approximately 58 tons/day is required.

In addition, the amount of seawater used to cool coke oven gas could be reduced by 160 skin 3/H. Table 1 (Properties of wastewater in Examples 2 and 3) A comparison between this example and the conventional method will be described below.

'1 is a method for reprocessing wastewater after activated sludge treatment.
Methods for using coke as fire extinguishing water (2) A method of adsorption treatment using activated carbon, a method of incineration after concentration treatment, etc. are known, but each method has various drawbacks. For example, the method of using coke as fire extinguishing water causes the coke to smell and generates a large amount of corrosive vapor, while the adsorption treatment method using activated carbon requires high equipment and operating costs due to the use of expensive activated carbon. The method of incineration after concentration treatment requires a large amount of thermal energy such as steam to concentrate the wastewater, and the equipment cost is high. On the other hand, the method according to this embodiment is an extremely advantageous method that solves the drawbacks of the secondary concentration method.

In other words, the large amount of thermal energy required for concentrating wastewater is
This is covered by recovering waste heat from coke oven gas.
In order to not only eliminate the need for new thermal energy such as steam, but also to achieve wastewater concentration by mutually using the equipment normally required for refining coke oven gas, new equipment and sites need to be added. is almost unnecessary, making it extremely economical. Furthermore, by combining this method with a normal submerged combustion method or wastewater combustion method, wastewater can be completely eliminated. As explained above with reference to the embodiments, the present invention allows the indirect gas cooler conventionally used in coke oven gas cooling equipment to be used as it is or to partially change the material, and to add heat insulation and three heat exchangers to the gas-liquid circulation system. By installing this system, the retained heat of coke oven gas can be effectively used as a heat source for refining coke oven gas and concentrating waste liquid, reducing thermal energy consumption such as steam in coke factories, and reducing the amount of seawater used as a butterfly. By reducing consumption, the amount of warm seawater discharged can be reduced. Furthermore, since wastewater can be concentrated to a concentration that can be economically processed with conventional submerged combustion or wastewater combustion equipment, in combination with these equipments, wastewater from coke plants can be completely eliminated.

In addition, since the equipment normally used in coke factories is used, there is almost no need for additional equipment for concentrating wastewater, or only a few additions of equipment are required, making it extremely economical.

Furthermore, most of the sites are for wastewater treatment. It has the advantage of not being necessary.

[Brief explanation of drawings]

Fig. 1 is a flow sheet of coke oven gas cooling equipment, Fig. 2 is a flow sheet of an example in which the present invention is used in a hazardous substance dispersion tower, and Fig. 3 is a flow sheet of an embodiment in which the present invention is used for concentration of activated sludge treated wastewater. A flow sheet of an example used in a processing facility is shown. 1...Coke oven, 2...Coke oven gas, 3
...Dry main, 4...Gas liquid, 5...Tar decanter, 6...Indirect gas cooler, 7...
... Direct gas cooler, 8... Diluted water cooler, 9...
... Sea water or cooling water tower circulating water, 10 ... Diluted water, 11 ... Absorption tower, 12 ... Harmful substance dispersion tower, 13 ... Absorption Liquid cooler, 14... Absorption liquid heat exchanger, 15... Poor absorption liquid, 16...
- Rich absorption liquid, 17... Reboiler, 18...
...Hydrogen sulfide, 19...Activated sludge treatment waste liquid,
20... Sannojima wastewater, 2 1... Cold water tower or vacuum evaporator, 22... Waste liquid heater. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A poor absorption liquid from which harmful or useful substances have been removed from a dispersion tower of coke oven gas purification equipment is used for cooling coke oven gas, and the heat-exchanged poor absorption liquid is used to cool coke oven gas. By returning the rich absorption liquid containing harmful or useful substances from the absorption tower of the coke oven gas purification equipment to the stripping tower and heating it and supplying it to the stripping tower, the harmful or useful substances are removed in the stripping tower. A method for recovering waste heat from coke oven gas, characterized in that it is separated and used as a poor absorption liquid for cooling coke oven gas and by circulating it in an absorption tower. 2 Gas liquid 4 from the dry main 3 and poor absorption liquid 15 from the indirect gas absorber 6 are both supplied to the stripping tower 12 for heating to remove hydrogen sulfide from the rich absorption liquid from the absorption tower 11. A method for recovering coke oven gas waste heat according to claim 1. 3. The concentrated waste liquid 19 of the activated sludge treatment waste liquid is used for cooling the coke oven gas and the gas liquid 4 sprayed on the dry main 3 and for cooling the indirect cooler 6, and the heat-exchanged concentrated waste liquid 20 is used as the activated sludge. A method for recovering coke oven gas waste heat according to claim 1, wherein the waste heat is recycled to a waste liquid concentration treatment facility 21 for concentrating treated waste liquid.