JPS6061024A - Process for removing sox and nox simultaneously - Google Patents

Abstract

PURPOSE:To improve denitration efficiency by regenerating an adsorbent used in a denitration tower by heating, sending the adsorbent to a denitration reaction tower without cooling the adsorbent, and allowing it to contact directly with waste gas which is previously admixed with ammonia. CONSTITUTION:SOX in the waste gas is removed by adsorption in a desulphurization reaction tower comprising a moving bed reactor contg. active carbon packed therein. The active carbon discharged from the desulphurization reaction tower 1 is sent to a regeneration tower 2 where it is regenerated by heating. The active carbon at high temp. is fed as it is from the regeneration tower 2 to the denitration reaction tower 4. Denitration reaction is caused by adding NH3 as reducing agent for NOX to the inlet of the denitration tower 4 stable simultaneous desulphurization and denitration are thus performed. Moreover, a cooler for sctive carbon is unnecessary. Stable operation is possible because formation of ammonium sulphate is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simultaneously and efficiently removing sulfur oxides (SOx) and nitrogen oxides (NOx) from υ1 gas.

The conventional flue gas desulfurization and denitration method is a dry flue gas desulfurization and denitration method in which flue gas is introduced into a moving bed reactor filled with a carbonaceous adsorbent such as activated carbon, and ammonia is added separately to simultaneously remove SOx and NOx. Common. In this method, since the main purpose is desulfurization reaction by adsorption, the adsorption reaction @ g ljA degree is set relatively low, and 150
The conventional method has the disadvantage that the denitrification rate obtained is low due to the low temperature.In addition, in the conventional method, NOx reduction agent is used in the desulfurization reaction tower exhaust gas. Since NH3 is injected and the desulfurization and denitration reaction is carried out in the single-stream denitration reaction tower alone, most of the NH3 is consumed by the sulfuric acid (H2SO4) fixed in the activated carbon and does not contribute to the NOx reduction reaction. .For this reason, the denitrification rate obtained is low.At the same time, ammonium sulfate (
' (NHa) 2SO4), acidic ammonium sulfate (NH4H
8O4), blocking of activated carbon occurs, especially at the gas introduction part of the desulfurization reaction tower, leading to blockage of the reaction tower.
Another disadvantage is that the activated carbon cannot be moved smoothly. The reaction formula in the reaction tower is as follows.

* * NH3+ H2So4+ NH4TTSO4NH3++
40 + 202 + Nz + 7/2H20 Injection of NH3 into the intermediate layer of the activated carbon packed bed, (3) 1 minute of the desulfurization reaction tower and denitrification reaction tower! Among these, (1)
Regarding C), it may be an effective method, but
No promising method has yet been found.

Regarding (2), since a very small amount of NH3 is directly injected into the activated carbon filling 11 7, there are problems with N I-I 30 dispersion and mixing, making it difficult to put it into practical use. Therefore, (3) is the most advantageous solution in terms of both improving the denitrification performance and preventing clogging of the activated carbon-filled bed due to precipitation in the flow chamber. If it is not possible to raise the gas temperature, new problems will arise, such as (1) increased equipment costs and (2) energy loss due to the increased gas temperature.

In view of the above points, the inventors of the present invention conducted extensive inspections, and as a result, introduced exhaust gas containing sulfur oxides and nitrogen oxides into a moving bed reactor containing carbonaceous adsorbent, and separately added ammonia to the reactor. In the dry flue gas desulfurization and denitration method that simultaneously removes sulfur oxides and nitrogen oxides by adding The carbonaceous adsorbent regenerated by heat treatment is fed into the denitrification reaction tower and filled up to a high temperature without passing through a cooler, and ammonia is added to the denitrification reaction tower in advance. It was discovered that the denitrification efficiency could be improved by introducing and directly contacting the desulfurization reaction tower outlet exhaust gas, and the present invention was completed based on this finding.

Hereinafter, the configuration of the present invention will be explained based on the drawings.

In the desulfurization reaction tower, which consists of a moving bed reactor and is filled with activated carbon, the SOx in the exhaust gas is first heated to 150°C.
It is removed according to the following reaction formula at the temperature after IJ. In general, n is 1 to 2 in the case of combustion exhaust gas.

So,,+'102+ (n+1)H2OfI-12
SO4・nH2OSO3+ (n+1) H2O−y
PII□SO4·nH, ○Here, the activated carbon that has adsorbed SOx in the exhaust gas is continuously discharged from the lower part of the desulfurization reaction tower 1 and conveyed to the regeneration tower 2. In the regeneration tower 2, H2SO4 fixed on the activated carbon is heated with a heating gas or the like and is thermally decomposed by the reaction described above, and is desorbed from the activated carbon as S02, and the activated carbon is regenerated.

2H2S○4 + C--n 2H20+ CO2-t 2SO2 Here, the regeneration temperature is generally 350~
The temperature was around 400°C, and S, who had escaped from the trench in Reproduction Tower 2,
The concentration of 02 gas varies depending on the heating method in the regeneration tower 2 and the amount of adsorption on activated carbon, but it is generally on the order of several percent to several tens of percent. , recovered as gypsum, etc.

On the other hand, the activated carbon desorbed and regenerated in the regeneration tower 2 has a
High temperature of about 400°C f Alta W), 150°Cn
It is cooled until after 1T, transported to the desulfurization reaction tower 1, and recycled for reuse. In the present invention, the activated carbon at a high temperature (350 to 400°C) discharged from the regeneration tower 2 is introduced into the denitrification reaction tower 4, which has both cooling and denitrification, without passing through a special cooler. By adding NH3 as a NOx reducing agent to the 4th part of the reaction tower, a denitrification reaction is caused. The size of the denitrification reactor 4 can be set arbitrarily depending on the denitrification activity of the activated carbon used and the required denitrification performance, regardless of the size of the desulfurization reaction tower 1 and the amount of activated carbon discharged from the desulfurization reaction tower 1. It is possible to do so. By providing the regeneration tower integrally above the denitrification reaction tower 4, it becomes possible to directly introduce the high-temperature activated carbon from the regeneration tower into the denitrification reaction tower 4 without having to transport it, which further simplifies the equipment. It's a good idea.

In the method of the present invention, the heat required for heating in the regeneration tower 2 is released into the atmosphere together with the exhaust gas, so there is concern that there will be a large economic loss. In some cases, for example, when water is used as a cooling medium, indirect cooling must be used. However, in the case of indirect cooling, the heat transfer coefficient between liquid and solid (activated carbon and water) is small, so a large amount of water is required, and it is difficult to obtain high-temperature water or steam. Heat cannot be used effectively, and instead requires ancillary equipment such as a cooling tower for circulating cooling water, so there is little economic gain. It is also economically advantageous as it does not require ignition of activated carbon due to exposure to exhaust gas while it is still at high temperature. Further, since the oxygen partial pressure in general combustion exhaust gas is much lower, there is no problem at all at a regeneration temperature of about 350 to 400°C.

As explained above, according to the method of the present invention, the following effects can be obtained.

(1) Stable simultaneous desulfurization and denitration treatment becomes possible.

(2) Since the denitrification reaction is caused by a carbonaceous adsorbent such as high-temperature activated carbon, the denitrification efficiency is improved compared to conventional methods.

(3) No cooler or cooling medium (water, air, etc.) is required to cool the carbonaceous adsorbent discharged from the regeneration tower.

(4) State in which NH3 is adsorbed in the denitrification reaction tower (unreacted NH
By introducing the carbonaceous adsorbent described in 3) into the desulfurization reaction tower, the desulfurization performance was improved, and the desulfurization reaction tower was stabilized without clogging due to the formation of ammonium sulfate or acidic ammonium sulfate or blocking of activated carbon. Driving becomes possible.

Next, embodiments of the present invention will be described.

Example Exhaust gas temperature at the outlet of the desulfurization reaction tower 150°C1 Desulfurization rate 95%
The activated carbon extracted from the desulfurization reaction tower is regenerated at 400°C, and the regenerated activated carbon is charged into the denitrification reaction tower and heated at 150°C.
When passing through the exhaust gas, the average temperature of the exhaust gas increased by about 25°C.

Regarding two types of activated carbon A and B made from various types of coal, S○
22001) pm, NOx 200ppm, 002
4-di-1 with a composition of 10%, H2O1O%, 1q2 balance
Gas, space velocity 1ooo 4, ammonia addition rate 40
011]') m, temperature] 50°C, 175°C, 200
When the denitrification performance was tested under the conditions of °C, the results shown in the table below were obtained.

As is clear from the table, when the reaction temperature increases by about 25°C, the denitrification performance increases by 10-b.

[Brief explanation of drawings]

The drawing is a flow sheet showing an example of an apparatus for carrying out the method of simultaneously removing sulfur oxides and nitrogen oxides of the present invention. 1... Desulfurization reaction tower, 2... Regeneration tower, 3 - Sulfur content recovery device, 4 - Denitrification reaction tower Applicant: Kawasaki Heavy Industries, Ltd.

Claims (1)

[Claims] 1 A dry process in which exhaust gas containing sulfur oxides and nitrogen oxides is introduced into a moving bed reactor filled with a carbonaceous adsorbent, and ammonia is added separately to simultaneously remove sulfur oxides and nitrogen acids and arsenics. In the 1-smoke desulfurization and denitrification method, exhaust gas is introduced into a desulfurization reaction tower, and the spent carbonaceous adsorbent that has adsorbed sulfur oxides in this desulfurization reaction tower is sent to a regeneration tower, where the carbonaceous adsorbent regenerated by heat treatment is It is characterized by charging and filling the denitrification reaction tower in a high temperature state without passing through a cooler, and introducing the desulfurization reaction tower height L1 exhaust gas to which ammonia has been added in advance into the denitrification reaction tower and bringing it into direct contact. A method for simultaneously removing sulfur oxides and nitrogen oxides.