JPS609551B2 - How to recover waste heat from ammonium water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is to remove harmful and useful substances mixed in circulating hot ammonium water produced when coke oven gas is cooled and purified, and then to use surplus ammonium water in a non-polluting state. Circulating heat that uses the waste heat of circulating heat ammonium water as heating for supplying it to an ammonia stripping device to remove and recover ammonia, etc. in the surplus ammonium water under reduced pressure in order to discharge it out of the system. The present invention relates to a method for recovering waste heat from cheap water.

Conventionally, in order to remove and recover ammonia, etc. contained in surplus ammonium water in order to release the surplus ammonium water to the outside of the system, as shown in Fig. After heating by 7, the steam 13 is introduced into the ammonia stripping tower 14.
Ammonia is separated at normal pressure by directly injecting the steam 13 into surplus ammonium water or by indirectly heating the bottom liquid of the ammonia stripping tower 14, and the ammonia is removed.
A method of discharging as waste water 12 is used.

In this case, under normal pressure, the temperature of the ammonia stripping tower is usually about 100° C. or more on average, and the temperature of the entire ammonia stripping tower is high.

When the above-mentioned steam is directly blown into the solution, hot ammonium water as a stock solution is heated to near its boiling point to evaporate ammonia and the like. Therefore, the steam containing ammonia etc. plays a role as a carrier zero gas, and the vapor containing ammonia etc. leaving the ammonia stripping tower is condensed by a condenser or sent to the next step in the form of steam as it is.

In addition, when the bottom liquid of the ammonia stripping tower is indirectly heated with steam, the moisture in the bottom liquid of the ammonia stripping tower evaporates, and the evaporated steam plays the same role as in the case of direct injection steam. However, the amount of wastewater decreases by the amount of water that evaporates. In any of the above cases, in the secondary method, as long as steam is used as a heat source for evaporating ammonia gas, etc. in the ammonia stripping tower, the amount of steam consumed in the ammonia stripping tower is equal to the surplus ammonium water supplied to the ammonia stripping tower. Approximately 0.15 to 0.2 tons per ton is required.

Alternatively, even if the equipment is improved and the steam consumption is minimized, about 0.05 to 0.07 tons are required per ton of surplus hot ammonium, and the cost for removing ammonia from surplus ammonium is extremely high.

Furthermore, because the surplus ammonium aqueous solution used as the processing fluid is an ammonia aqueous solution containing acidic content, ``in addition to being highly corrosive,
The operating temperature conditions of the ammonia stripping tower and related equipment are high, resulting in severe corrosion, and there are currently drawbacks such as the lack of suitable materials with sufficient resistance.

In view of the above, the inventors of the present invention have developed a solution for heating an ammonia stripping tower by effectively utilizing the waste heat of hot ammonium water, which conventionally had a medium temperature of about 75 qo and was unused and wasted. As a result of intensive research aimed at recovering waste heat, we found that by operating an ammonia stripping tower under reduced pressure, low-temperature operation is possible. can be effectively used as a heat source for heating surplus ammonium water.
The waste heat of hot ammonium water is effectively recovered within the system, and since it is operated at a low temperature, corrosion of the ammonia stripping tower and related equipment, which was considered a drawback in the past, is prevented, and the quality of the materials used in the equipment used is reduced. The present invention was completed by discovering that this is possible, and the present invention involves operating an ammonia stripping device under reduced pressure to remove ammonia gas, etc. from surplus ammonium water generated during the purification of coke oven gas, supplying hot ammonium water used for cooling coke oven gas to the ammonia stripping device, and using the waste heat of the hot ammonium water as a heat source for the ammonia stripping device;
Ammonia gas, etc. is removed from the surplus ammonium water supplied to the ammonia stripping equipment, whose heat is recovered by the ammonia stripping equipment, and the hot ammonium water is recycled to cool and purify coke oven gas. This method provides a method for effectively recovering the waste heat of medium-temperature hot ammonium water, which is abundantly available.By using the waste heat of circulating hot ammonium water, the ammonia stripping equipment can be operated under reduced pressure. This eliminates the need for steam at all or significantly reduces the need for steam for stripping ammonia, etc. from approximately 5,000 surplus ammonium water, and the operating temperature conditions for the ammonia stripping equipment and related equipment are low. This has the advantage of preventing corrosion of them.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 shows a flow sheet of an embodiment of the apparatus used in the present invention. In order to cool the coke oven gas 2 discharged from the coke oven 1, the hot ammonium water 4 sprayed on the dry main 3 is It is collected in a decanter 5, and after removing tar and sludge, it is circulated again to the dry main 3 and used for cooling the coke oven gas 2.

A part or all of this hot ammonium chloride 4 is supplied to an ammonia stripping device 8 operated under reduced pressure, and converted into hot ammonium water by a surplus ammonium water preheating heat exchanger 7 provided for heating the surplus ammonium chloride 6. Excess ammonium chloride 6 is heated by exchanging heat with surplus ammonium chloride and/or by heat exchange between hot ammonium water and bottom circulating liquid by providing a bottom reboiler 10 for heating bottom circulating liquid 9 of the ammonia stripping equipment. A sufficient amount of heat is obtained to remove ammonia gas, etc., and the steam 11 containing ammonia and the like is extracted from the upper part of the ammonia stripping device 8, and the steam 11 containing ammonia and other harmful substances and useful substances, such as ammonia, is removed from the lower part. The diluted waste water 12 is discharged.

Figure 3 shows the flow around the ammonia stripping device of the embodiment of the device used when heat insulation of circulating hot ammonium water and steam are used together to heat surplus ammonia water supplied to the ammonia stripping device of the present invention. It shows the sheet,
In addition to the apparatus shown in Figure 2, an ammonia stripping apparatus is equipped with a direct injection device for steam 13 into the bottom liquid of the ammonia stripping device or an indirect heating device using steam, which can reduce the amount of heat required to remove ammonia gas, etc. It is suitable to use when there is a shortage or when the equipment is to be converted into 4-type equipment.

Further, FIG. 4 shows that only the bottom reboiler 10 for heating the bottom circulating liquid 9 of the ammonia stripping device 8 is used to heat the surplus ammonium water 6 supplied to the ammonia stripping device 8, and the surplus ammonium water 6 as shown in FIGS. This is a flow sheet of an example of an ammonia stripping device in which the ammonium water preheating heat exchanger 7 is not installed.

Of course, in the case shown in FIG. 4, it is also possible to use the steam 13 in combination as in the case shown in FIG.

Next, the present invention will be explained by examples. ．． Embodiment 1 As shown in FIG. 2, which is a four-sheet diagram of an embodiment of the apparatus used in the present invention, 120,000 N is discharged from the coke oven 1.
Coke oven gas 2 of about 300 qo m3/hr is cooled to about 800 qo by hot ammonium water 4180 m3/hr sprayed in the dryer oven 3.

On the other hand, the hot ammonium water 4 leaving the dry main 3 absorbs harmful and useful substances such as ammonia in the coke oven gas, and
000, and once collected in the decanter 5 and taken out after removing tar and sludge, it is about 75 qo. Of this hot ammonium water 4, 45 m3/hr is supplied to an ammonia stripping device 8 in order to be discharged outside the system.

The surplus ammonium water 645h3/hr is first led to the surplus ammonium water heat exchanger 7 for heating, and if heat exchange is performed using the hot ammonium water 4, the hot ammonium water 4 is reduced to 65 qo, and the surplus ammonium water is Water 6 is heated from 50oo to 60qo. Therefore, here, 4.5×1 Kcal/hr of heat was recovered and used. In addition, 315 m3/hr of hot ammonium water 4 is led to a bottom reboiler for heating the bottom circulation liquid 9 of the ammonia stripping equipment, and when heat exchanged, the hot ammonium water 4 is reduced to 7000 m3/hr, which is used to heat the bottom circulating liquid 9 of the ammonia stripping equipment. Circulating fluid 931 shoes 3/hr is 66qo to 7
It is heated to 1℃, and 1.6 x 1 Kcal/hr of heat is recovered, and the entire device produces 2.05 x 1 Kcal/hr.
This means that the heat amount of hr has been utilized.

On the other hand, the ammonia stripping device 8 is operated at an average operating pressure of 18
When operating under reduced pressure on the 0 side, an ammonia recovery rate of 6 to 9% by weight or more is achieved in excess ammonium water containing an ammonia content of 250. The wastewater 12 has an ammonia content of 250 or less, and is ready for discharge.

The temperature of the ammonium solution after heat recovery will drop when the parts that are bypassed without heat recovery are combined, but this has almost no effect on the thermal balance of the ammonium solution that is distributed and circulated in the dry main 3. .

If the temperature of the circulating hot ammonium water 4 decreases significantly and the temperature of the hot ammonium water led to the surplus ammonium heat exchanger 7 and bottom reboiler 10 decreases significantly, the temperature can be maintained sufficiently by appropriately insulating the pipes. .

Furthermore, depending on the capacity of the ammonia stripping equipment, it is also possible to recover the waste heat of multiple lines of circulating hot ammonium water by using the waste heat of multiple lines of circulating hot ammonium water to remove ammonia from surplus ammonium water. be.

Example 2 The amount of surplus ammonium water supplied to the ammonia stripping device 8 using the device shown in FIG. Reduce the amount of hot ammonium water 4 introduced into the bottom reboiler 1 to reduce the amount to 9 dishes 3/hr, and the hot ammonium water 4 is 7
7 decreased from 5° C. to 0, the temperature of the stripping tower bottom circulating liquid 9 was increased from 66oo to 69qo, and a heat amount of 2.7×1 Kcal/hr was recovered and utilized.

The same amount of heat as shown in Example 1 for heating the surplus ammonium water 6 supplied to the ammonia stripping device 8 is 4.5×
If 1 Kcal/hr is recovered from hot ammonium 4, the total will be 7.2 x 1 Kcal/hr, but this is insufficient to ensure the same ammonia recovery rate as in Example 1. Therefore, 6 kg/ground of saturated steam 13 is
．． Direct bale blowing at 3 on/hr is required.

However, this case has the advantage that the equipment for the bottom reboiler 10 is about 1/10 of that in Example 1, and the amount of steam consumed is significantly reduced compared to the conventional method.

Example 3 When the apparatus shown in FIG. 4 is used as a flow sheet of an example of the apparatus used for carrying out the present invention, the amount of surplus ammonium water supplied to the ammonia stripping apparatus 8 is calculated as in Example 1. In almost the same manner as shown in Fig. 4, the amount of hot ammonium water 4 led to the bottom reboiler 1 for heating the bottom circulating liquid 9 of the ammonia stripping equipment was 40 n3/
hr, the hot ammonium water 4 will drop from 75oo to 7000, and the bottom circulating fluid 94 of the ammonia stripping device 8 will
0 h3/hr 6 is heated from o to 71°C, 2.
05×1 piKcal/hr of heat is recovered from hot ammonium water 4,
It will be used.

As a result, the same amount of heat as in Example 1 was supplied to the ammonia stripping device 8, and Example 1
Almost the same ammonia recovery rate can be obtained.

In this case, although the supply amount of hot ammonium water 4 increases, there is an advantage that the secondary heat exchanger 7 for heating the surplus ammonium water 6 can be omitted. Further, a subthermal heat exchanger 7 for heating the surplus ammonium chloride 6 is used, and the bottom of the ammonia stripping device 8 is used in almost the same manner, although the quantitative relationship used for recovering the waste heat of the ammonium chloride 4 is slightly different. The bottom reboiler 10 for heating the circulating fluid can be omitted, or steam can also be used in combination with the ammonia stripping device 8.

[Brief explanation of drawings]

Figure 1 is a flow sheet of the ammonia stripping tower for removing ammonia gas from surplus ammonium water in the conventional method, Figure 2 is a flow sheet of an embodiment of the apparatus used to carry out the present invention, and Figure 3 , and FIG. 4 respectively show flow sheets for other embodiments of the ammonia stripping apparatus used in carrying out the present invention. 1... Coke oven, 2... Coke oven gas, 3... Dry main, 4... Hot ammonium water, 5...
... Decanter, 6 ... Surplus ammonium water, 7 ...
・・Surplus ammonium water sub-thermal heat light sliding device, 8……Ammonia stripping device, 9……Bottom circulating liquid of ammonia stripping device, 10……Bottom repoiler of ammonia stripping device, 11・・...Ammonia vapor, 12...Wastewater, 13...Steam, 14
・・・・・・Ammonia stripping tower with conventional equipment. ※・The murderous machine 2 drawings ○3 drawings Iso 4 drawings

Claims (1)

[Claims] 1. An ammonia stripping device that removes ammonia gas, etc. from surplus ammonium water generated during the purification of coke oven gas is operated under reduced pressure, and the heat used for stripping the coke oven gas is removed. Ammonium water is supplied to the ammonia stripping device, the waste heat of the hot ammonium water is used as a heat source for the ammonia stripping device, and the hot ammonium water whose heat is recovered by the ammonia stripping device is reused in the coke oven. A method for recovering waste heat from hot ammonium water, characterized in that it is recycled and used for cooling gas. 2 Heat exchange between hot ammonium water and surplus ammonium water by providing a heating and preheating heat exchanger for surplus ammonium water to be fed to the ammonia stripping equipment, and/or ammonia stripping equipment 2. The method for recovering hot ammonium water according to claim 1, wherein heat is exchanged between the hot ammonium water and the bottom circulating liquid by providing a bottom reboiler for heating the bottom circulating liquid in the boiler.