JPS5948764B2 - Ammonium sulfate production method using coke oven gas sensible heat - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ammonium sulfate using coke oven gas sensible heat.

In general, ammonia contained in coke oven gas causes corrosion of equipment, generation of NOx, etc. if left in coke oven gas, so it is removed from coke oven gas by recovering it as ammonium sulfate or liquid ammonium.

Among these methods, the method of recovering ammonium sulfate is a process in which coke oven gas is brought into contact with a dilute sulfuric acid solution (hereinafter referred to as ammonium sulfate mother liquor), ammonia is absorbed, ammonium sulfate is produced, and in some cases, it is crystallized and recovered as powdered ammonium sulfate. and a step of growing crystals and granulating them into granular ammonium sulfate.

Conventionally, in the production method of ammonium sulfate, the method for crystallizing crystals in the granulation process is to generate a supersaturated liquid by evaporating the solvent, but in this method, the solvent, that is, water, is removed by evaporation. It is necessary to replenish the amount of heat required.

In addition, there is water that enters from outside the yarn, such as washing water in various parts of the system and added water, which also needs to be removed by evaporation.
The amount of heat required for this also needs to be replenished.

However, on the other hand, the heat generated within the system includes the heat of dissolution of concentrated sulfuric acid added from outside the system and the heat of neutralization of sulfuric acid and ammonia, but the amount of heat generated by these alone is insufficient for the amount of heat required by the system. There is a shortage and heat is supplied by another heat source.

Steam is generally used as this heat source, but the amount of steam used is large, increasing the manufacturing cost of ammonium sulfate.

On the other hand, coke oven gas generated from a coke oven can reach up to 8
Since the temperature is between 00 and 250°C, it is cooled and the tar and ammonium water are separated and sent to the next step.

This coke oven gas is cooled by flushing a large amount of ammonium water into the coke oven gas, and then cooled by seawater in a primary cooler.

Therefore, the amount of heat lost by coke oven gas being cooled is transferred to seawater and ammonium water.

Among these, ammonium water has a relatively low temperature of 70 to 80°C, so it has not been used in the past because there is no effective recovery method for it as a heat source.

The present invention effectively utilizes the heat retained in ammonium sulfate at a low temperature level by combining it with the production process of ammonium sulfate, which is produced as a by-product from coke oven gas.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a diagram showing the manufacturing process of ammonium sulfate according to the conventional method. Coke oven gas 2 is generated from a coke oven 1, ammonium water 4 is flushed in a dry main 3, and then is sent to a primary cooler 5. Cooled by seawater.

Next, the pressure is increased by the blower 6, and the coke oven gas desulfurization equipment 7
and enters the ammonium sulfate saturator 8, where ammonia is removed.

On the other hand, the ammonium water 4 is cooled by separating it in a cool decanter 9, passed through an ammonium water tank 10, and circulated by a pump 11.
Some of it is being blown outside the system.

On the other hand, in the ammonium sulfate manufacturing process, the ammonium sulfate mother liquor 12 that has absorbed ammonia in the ammonium sulfate saturator 8 is pumped to the pump 13 to
It is sent to the crystallization tank 14 at 5°C and then pumped to the vacuum device 1 by the pump 15.
The evaporator 17 is kept under vacuum by the evaporator 6.

Here, water, which is a solvent, evaporates and is cooled to crystallize,
It is granulated in a crystallization tank 14.

The ammonium sulfate mother liquor that has crystallized ammonium sulfate passes through a tar separation tank 18 and returns to the ammonium sulfate saturator 8 by a pump 19.

The amount of heat required for this step is provided by a heater 20 that heats the ammonium sulfate mother liquor with steam while partially withdrawing it from the ammonium sulfate saturator 8 and returning it to the ammonium sulfate saturator 8 again using a pump 21.

Next, an embodiment of the present invention will be described based on FIG.

FIG. 2 is a block diagram showing an embodiment of the present invention, and since some parts overlap with those in FIG. 1, a description of the overlapping parts will be omitted.

The present invention omits the step of partially extracting the ammonium sulfate mother liquor from the ammonium sulfate saturator 8 shown in FIG. is returned to the ammonium sulfate saturator 8 via the heater 20, and a heat exchanger 22 is provided on the way.
The sensible heat of the ammonium sulfate is used to raise the temperature of the ammonium sulfate mother liquor by partially circulating the ammonium 4 to transfer the sensible heat of the ammonium sulfate to the ammonium sulfate mother liquor.

Specific examples of the present invention are shown in Table 1 in comparison with conventional methods.

Table 1 shows the operating conditions and the resulting amount of heating steam used in the heater 20 when the present invention is implemented in comparison with the conventional method.

According to the present invention, as shown in Table 1, ammonium water 4 having a sensible heat of 80 °C is maintained at a temperature of 40 °C by guiding it by 200 m'/H to the heat exchanger 22 according to the present invention. 200771 returned from the crystallization tank 14 to the ammonium sulfate saturator 8
The temperature of the ammonium sulfate mother liquor of ″/H after leaving the heat exchanger 22 is
As a result, the amount of steam used by the heater 20, which conventionally required 1.06 T/T-ammonium sulfate, could be reduced to 0.36 T/T-ammonium sulfate.

As described above, according to the present invention, it is possible to significantly reduce the amount of steam used in the production process of ammonium sulfate, which is produced as a by-product from coke oven gas.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional process for manufacturing ammonium sulfate, and FIG. 2 is a block diagram showing an embodiment of the present invention. 1: Coke oven, 2: Coke oven gas, 3: Dry main, 4: Ammonium water, 5 NIB primary cooler, 6: Blower, 7: Coke oven gas desulfurization equipment, 8: Ammonium sulfate saturator, 9
: Cool decanter, 10: Ammonium water tank, 11: Pump, 12: Ammonium sulfate mother liquor, 13: Pump, 14: Crystallization tank, 15
: Pump, 16: Vacuum device, 17: Evaporator, 18: Tar separation tank, 19: Pump, 20: Heater, 21: Pump, 22: Heat exchanger.

Claims (1)

[Claims] 1. In the manufacturing process of ammonium sulfate, which is a by-product of coke oven gas, the ammonium water recovered by flashing the coke oven gas generated from the coke oven is exchanged with the ammonium sulfate mother liquor to convert the sensible heat of the coke oven gas into ammonium sulfate crystals. A method for producing ammonium sulfate using coke oven gas sensible heat, which is characterized in that it is used as a heat source for crystallizing coke oven gas.