JPS60257824A - Denitration of coke oven exhaust gas - Google Patents

Abstract

PURPOSE:To contrive to conserve energy, in the denitration method of coke oven exhaust gas, by evaporating aqueous ammonia recovered from coke oven gas by the sensible heat of exhaust gas before introducing the same into the denitration reactor provided to a flue outlet. CONSTITUTION:The coke oven gas generated from a carbonization chamber 2 is introduced into a gas purification process 6 where impurities such as acidic gas or NH3 are removed to obtain purified gas 8 while a recovery substance 7 and aqueous ammonia 13 are recovered from the impurities. The exhaust gas generated from a combustion chamber 3, to which fuel 9 is added, enters a heat accumulation chamber 4 to recover heat and is introduced into a denitration reactor 12 through a flue 10. Recovered aqueous ammonia is guided to an evaporator 20 and a flash device 21 to be taken out as NH3-vapor 16 which is, in turn, supplied as an NOx reducing agent from a nozzle 19 to perform the denitration reaction with exhaust gas in the direction reactor and purified gas 18 is exhausted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to catalytic flue gas denitrification using ammonia as a reducing agent for coke oven combustion chamber flue gas.

(Prior Art) In recent years, various types of exhaust gas have been subject to fiox regulations from the viewpoint of preventing air pollution, and coke oven combustion chamber exhaust gas has also been targeted. As a method for reducing LOZ in flue gas, ammonia gas is used as a reducing agent to reduce 1 (Ox to 2) in flue gas.
A flue gas denitrification method in which nitrogen is reduced and removed by contacting with a catalyst at around 00°C to 400°C has been put into practical use.

On the other hand, coke oven gas generated from the carbonization chamber by coal carbonization contains ammonia gas as an impurity, and is recovered as aqueous ammonia in the coke oven gas purification process.

Therefore, if this ammonia water can be used as a reducing agent for flue gas denitrification, there will be no need for ammonia purchase and storage equipment, which is very preferable. However, since ammonia needs to be supplied as a gas to the denitration equipment, in order to use the relatively low concentration ammonia water recovered from coke oven gas, a heat source is required to evaporate the ammonia water. There were other problems.

(Problems to be Solved by the Invention) The present invention is accomplished by developing a purposeful method that enables ammonia water recovered from coke oven gas to be used as a reducing agent for denitration of coke oven combustion chamber exhaust gas. The purpose is to eliminate the need for transporting and storing ammonia from outside the plant.

(Another means to solve the problem) The present invention installs an ammonia water evaporator at the flue outlet attached to a coke oven, and uses the concentrated ammonia gas generated from the evaporator as a reducing agent for denitration into the flue. The 1qOX in the exhaust gas is
This is an economical and energy-saving denitrification method for coke oven combustion exhaust gas that does not require a heat source from outside the plant.

Embodiments of the present invention will be described below in conjunction with the accompanying drawings.

FIG. 1 is an example of a flow sheet of the entire apparatus for carrying out the method of the present invention.

In Fig. 1, 1 is the coke oven main body, 2 is the carbonization chamber, and 6
is a combustion chamber, and 4 is a heat storage chamber. The coke oven gas 5 generated from the carbonization chamber 2 undergoes a gas purification process 6 to remove impurities such as acid gases such as hydrogen sulfide and hydrogen cyanide and ammonia, and is sold as purified gas 8 for use as city gas. Recovered materials 7 such as sulfur and aqueous ammonia 13 are recovered.

On the other hand, the coke oven combustion chamber exhaust gas generated from the combustion chamber 6 with the addition of fuel 9 undergoes heat recovery in the heat storage chamber 4, and then passes through the flue 1.
It leads to 0. Conventionally, the flue outlet gas 11 is normally discharged directly into the atmosphere, but in the present invention, the NOx contained in the exhaust gas is reduced and decomposed in the denitrification reactor 12 filled with a denitrification catalyst according to the reaction formula shown below. Clean exhaust gas 18
Discharge as.

4 Ho + 4 NK$ + 02--→41? ,
+ 6I (, 0 ---- (1) In the present invention, the source of ammonia (NHs) as a reducing agent is a part of the recovered ammonia water 1 filtration outside the system 14 and a part of the ammonia water 1 for the reducing agent.
This ammonia water is used as denitrification reactor 1.
The concentrated ammonia vapor 16 is introduced into the ammonia water evaporator 20 and flasher 21 installed downstream of the denitrification reactor 12, and the concentrated ammonia vapor is used as a NOx reducing agent from the ammonia 1 supply nozzle 19 installed in the denitrification reactor 12. supply In addition, in the figure, 17 is the outlet exhaust gas of the reactor 12, and 22 is the bottom water of the flasher 21.

Example The flue outlet exhaust gas 11 generated from a coke oven of 45 t/h is as shown in Table 1, and about 9 wt of aqueous ammonia 700 and 11 were obtained from the gas purification step 6.

Table 1 300 Kq of ammonia water was separated and the evaporation tube area was 6R.
is supplied to an evaporator with a pressure of 3 kg/h1. -G.

Ammonia vapor at 145°C was obtained, introduced into a flasher 21, and flashed to normal pressure to obtain ammonia gas 16 containing water vapor at about 1[]0°C.

There are 16 ammonia gases totaling 32! ', the ammonia concentration was 28X. The ammonia water 23 still obtained from the flash tank bottom was a total of 268 Kq;
The ammonia concentration was approximately 66 wt%.

The ammonia gas 16 was supplied to the denitrification reactor 12 from an ammonia supply nozzle 19, and the amount of supply was controlled such that only an amount sufficient to provide a predetermined value for the NOX concentration of the log gas 17 coming out of the denitrification reactor 12 was supplied.

In other words, the ammonia gas 16 necessary to supply ammonia so that the outlet NOX concentration is 20 ppm (approximately 90% denitrification rate) is the flue outlet exhaust gas flow rate 4.
0.000 Kn? /h, 1 (Ox a degree 200
At ppm hour, the total amount was 22 kg/h, and it was sufficient to supply about 215 kg/h of the total ammonia gas 32 in the flash unit 21.

The remainder, about 10 K4/h, can be used for other purposes as recovered ammonia. In addition, the reactor outlet gas 17
The unreacted ammonia gas concentration is about 15 ppm,
The gas temperature was about 20° C. lower than the inlet gas 18, and there were no particular problems.

The denitrification reactor uses the well-known anatase titanium oxide (Tie) and vanadium oxide (Tio).
This is a lattice-shaped catalyst packed with 10 m of lattice-shaped catalyst.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of the entire apparatus showing how the present invention is implemented for the deaf. Sub-agents 1) Meifuku agent Ryo Hagiwara -

Claims (1)

[Claims] In a method of catalytically reductively decomposing dox contained in coke oven exhaust gas discharged from multiple combustion chambers with ammonia, ammonia water recovered from coke oven gas generated from multiple carbonization chambers is used to absorb the sensible heat of the coke oven exhaust gas. A method for denitrifying coke oven exhaust gas, which comprises vaporizing the ammonia vapor into ammonia vapor and introducing the ammonia vapor into a denitrification reactor installed at the outlet of the flue.