JPS60129127A - Desulfurization and denitration process for waste gas - Google Patents

Abstract

PURPOSE:To perform desulfurization and denitration of waste gas simultaneously by improving the activity of catalyst and to improve rate of desulfurization and denitration remarkably by using active carbon incorporated with a metal component such as V as desulfurizing and denitrating agent. CONSTITUTION:Gaseous ammonia is admixed with waste gas contg. NOx and SOx and the mixture is guided to a desulfurization and denitration stage 1 from an inlet 3 of the gas. The waste gas moves in the horizontal direction to cross with a moving bed 4 of packed active carbon incorporated with a metal component such as V, W, etc. moving vertically from above to below, and SOx is converted to SO3 to deposit on the active carbon in the moving bed, and NOx is reduceed to innoxious material simultaneously. Purified gas is discharged from an outlet 5. On one hand, the active carbon contg. deposited SO3 moves downward through the moving bed and is discharged from an outlet 6 and is guided to a regeneration stage 2 where it is regenerated by heating at 300-400 deg.C, and transported again to the desulfurization and denitration stage. Replenishing active carbon is fed to compensate discharged pulverized active carbon.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a method for desulfurization and denitration of exhaust gas, and in particular, a method for improving the activity by using activated carbon to which a metal component such as vanadium is added as a desulfurization and denitration agent. , with sharp sulfur content,
Detril that can significantly improve both the denitrification rate
lRelating to a denitrification method.

[Technical background of the invention and its problems] Generally, exhaust gas discharged from a combustor such as a boiler contains SOx (sulfides) and NOx (nitrogen oxides), so it is necessary to desulfurize the exhaust gas. After denitration treatment,
Emitted into the atmosphere.

Conventionally, this desulfurization method has mainly been carried out using a wet desulfurization method (lime plaster method) that uses limestone as an absorbent because of its relatively good desulfurization efficiency. Not only does this require water, but there is also the risk of secondary pollution caused by wastewater. Furthermore, this desulfurization method can hardly remove SOi, so it may not be sufficient from the viewpoint of preventing pollution, and there is also the problem that diffusion is not good because the exhaust gas temperature is low. .

On the other hand, in conventional denitrification methods, for example, ammonia is injected into the exhaust gas and NOx is removed under the titanium-vanadium catalyst.
Dry denitrification method in which x is reduced and denitrified (processing temperature approximately 350℃)
), but in this method, acidic ammonium sulfate, which is a compound of leaked ammonia and Sox during denitrification, condenses on the subsequent air heater, causing blockage of the exhaust gas passage and corrosion of the equipment. It was causing problems.

Recently, a method has been devised to simultaneously perform desulfurization and denitrification using activated carbon in order to solve these conventional problems all at once. At present, it has not been put to practical use because not only is it not possible to obtain a high desulfurization and denitrification rate, but it is also not practical.

The present invention has focused on the above-mentioned problems and has been devised to effectively solve them.

[Objective of the Invention] The object of the present invention is to use activated carbon to which a metal component such as vanadium is added as a desulfurization and denitrification agent to improve the activity and perform sulfurization and denitration at the same time. It is an object of the present invention to provide an exhaust gas desulfurization and denitrification method that can significantly improve both the denitrification rate and the denitrification rate.

[Summary of the Invention] The present invention involves mixing exhaust gas with ammonia and bringing it into contact with activated carbon that has been highly activated by adding at least one metal component of vanadium, tungsten, etc. to achieve desulfurization and denitrification. At the same time, the above purpose is achieved.

In other words, the present inventors have found that desulfurization and denitrification activities can be significantly improved by adding metal oxides such as vanadium to carbonized char (activated carbon) produced by carbonizing coal etc. By obtaining the following, we have completed the present invention.

[Embodiments of the invention] The method of the present invention will be explained in detail below with reference to the accompanying drawings.

FIG. 1 does not show a process diagram for explaining the method of the present invention.

As shown in the figure, the method of the present invention includes a desulfurization and denitration step 1 in which activated carbon to which metal components such as vanadium and tungsten are added is brought into contact with SOX and NOX-containing exhaust gas mixed with ammonia to desulfurize and denitrate; S discharged
It mainly consists of a regeneration step 2 in which OX adsorbing carbon is heated to remove H1SO4 (sulfuric acid) and regenerate activated carbon.

The metal component-added activated carbon used in the desulfurization and denitrification process 1 exhibits a desulfurization effect that adsorbs SOx in the exhaust gas and separates it from the gas, and at the same time, ammonia (Nl-1s) mixed with NOx in the exhaust gas ＞It exhibits a catalytic effect that makes it non-polluting by reacting with other substances, producing two effects.

Specifically, the desulfurization effect described above is not simply adsorption by activated carbon (as shown in the following formulas (1), (21, and (3), Soy is oxidized to SOi, and further reacts with water vapor to form HxSOi). (sulfuric acid) and is adsorbed.

Here, the metal component such as vanadium acts as a catalyst for oxidizing SO+, and is an important factor in desulfurization performance.

So2 → SOS' ... (1) SOx +1/2 Qy →SQi"-・-ri>1
SO3+l-h O→H2$oa" - (No adsorption state is shown in 31.

In addition, No is subjected to a severe reduction reaction as shown in the following formula (4),
Harmless N2 roars.

4 N O+ 4 N H! + Or -) 4N+ +61-120 - (41 The activated carbon used here can be carbonized carbonized carbon material made by carbonizing wood, coal, etc., or petroleum-based char made from petroleum residue. In particular, coal with a low degree of coalification, such as lignite and brown coal, is preferable from the viewpoint of activity and economic explosiveness.

Regarding the method of adding metal components, for example, taking vanadium as an example, ammonium metavanadate, which is an oxide, can be dissolved in water. i (approximately 80°C) with activated carbon (spray may be used) and dried. Further, it is desirable that the vanadium addition rate be 1100 pp or more.

Note that the addition method is not limited to the above-mentioned impregnation;
In addition to vanadium, the additive element may be tungsten, germanium, titanium, niobium, copper, or iron, or a mixture thereof.

As described above, by using activated carbon to which a metal oxide is added (contained) as a 1152 sulfur denitrification agent, the 1112 sulfur and denitrification performance can be significantly improved.

In other words, the oxidation catalytic activity and adsorption area (specific surface area) of sol are important factors for desulfurization properties, but the former oxidation catalytic activity is affected by the synergistic effect of the added metal oxide and activated carbon. Activated carbon has an effective effect on the latter adsorption area, and carbonized char of coal with a low degree of coalification is particularly good.

Regarding the denitrification property, that is, the ability of No to reduce ammonia, although titanium-vanadium catalysts have been put into practical use at high temperatures (approximately 350°C) as described in the prior art, their activity is extremely low at low temperatures, so they are not used. However, the denitrification agent according to the present invention has significantly improved denitrification properties due to the synergistic effect of activated carbon and the added metal oxide. do.

Next, the activated carbon used in I]52 sulfur denitrification step 1 is
Since the desulfurization and denitrification performance deteriorates due to the adsorbed 1-hsO4' (sulfuric acid), it is transferred to regeneration process 2, and then
By heating to ~400°C, th-hsO4 is desorbed and regenerated as shown in the following formula (5).

1-h 804 +1/2 C →SO+ +I-h O+ 1/2 CO+ ・-(b
) The tree shows an adsorption state.

As a result of the regeneration, the generated 80'y is transferred to the sulfur recovery process, while the recycled activated carbon is transferred to the desulfurization and denitrification process 1 and used again as a desulfurization and denitration agent.

Example 1 As an example of the present invention, a moving bed cross-flow desulfurization and denitrification method will be explained according to a process diagram.

Exhaust gas (S 0 +
: 200+1DII1. N0: 7001)
l) Add and mix 1.2 times (molar ratio) of ammonia gas to No in m), and then lead it to the resulfur denitrification process 1 from the gas inlet 3. ) is filled and moves horizontally across the moving bed 4 moving from above to below, where desulfurization and denitrification are performed. That is, SO2 and SOx are adsorbed on activated carbon as sulfuric acid, and at the same time, NO is subjected to a reduction reaction with ammonia or the like to be rendered harmless.

The purified exhaust gas is discharged from the exhaust port 5 as clean gas.

On the other hand, activated carbon that adsorbs SOx etc. as sulfuric acid is used in the moving bed 4.
The adsorbed coal gradually descends and is discharged from the adsorbent discharge port 6, and is then transferred to the regenerated culm 2 and led out to this process via the introduction lower.

This activated carbon is heated to 300 to 400° C. in regeneration step 2, and as a result, sulfuric acid is desorbed to produce pJ of activated carbon.

After being discharged from the activated carbon outlet 8, the regenerated activated carbon is transferred to the desulfurization and denitrification process 1, and is used again as a desulfurization and denitration agent.

Incidentally, since activated carbon tends to be in short supply due to the discharge of powdered coal, supplementary activated carbon is supplied to compensate for this shortage.

On the other hand, in the regeneration process 2, SO+L and tsO+sol generated by 1-hsO4 being subjected to JB2 and W
, ] 9 and then transferred to a conventional sulfur recovery process.

As a result of the nr gas treatment at S V 400h in the above treatment steps, high desulfurization and denitrification rates could be obtained, such as a desulfurization rate of 99.9% and a denitration rate of 87%.

Here, further considering the desulfurization and denitration conditions, the exhaust gas temperature is preferably 110 to 1 GO'C, and the desulfurization rate decreases on the high temperature side, and the denitration rate decreases on the low temperature side.

The SV is preferably 100 to 1000 h; if it is too large, the m2 FA denitrification rate will decrease, and if it is too small, it will be uneconomical. In addition, the amount of ammonia gas added to the exhaust gas is preferably 0.8 to 1.2 (molar ratio) to NOx; if it is too large, the denitrification rate will improve, but leak ammonia will increase, and on the contrary, if it is too small. and the denitrification rate decreases.

Furthermore, the gas flow rate in the moving bed is preferably 0.1 to 3/sac; if the flow rate is too high, the pressure loss will increase and it will be economically disadvantageous, while if the flow rate is too low, it will cause back-mixing of exhaust gas, etc. Denitrification rate decreases.

In addition, the desulfurization and denitrification agent used is an aqueous solution of ammonium metavanadate (
(approximately 80℃) and dried, vanadium addition rate 11
It was manufactured by adjusting the ppm to 00pp or more.

In this example, ammonia gas was injected into the exhaust gas without any treatment; however, the SO in the exhaust gas
If the concentration of 2 is high, acidic ammonium sulfate etc. will be generated if ammonia is injected into the exhaust gas before desulfurization and denitrification treatment.
Not only does the denitrification rate decrease, but various other problems may occur, so to prevent this, a two-stage treatment method is used in which preliminary desulfurization is performed before ammonia injection, and then simultaneous desulfurization and denitrification treatment are performed. It is better to use φ instead of φ, and the dust removal effect is also great.

[Effects of the Invention] In summary, the method of the present invention can exhibit the following excellent effects.

(1) By using activated carbon to which a metal component such as vanadium is added as a desulfurization and denitrification solvent, the desulfurization and denitration activity can be significantly increased, and as a result, a high level of desulfurization can be achieved, and a practical 4T high denitration rate can be obtained. I can do it.

(2) As a result, the activated carbon cycle time becomes longer;
The amount of activated carbon regenerated per hour is reduced, and the heating energy for regenerating activated carbon can be reduced.

(3) Due to dry desulfurization, SOq removal rate is extremely high.
(ioo%), water for slurry and wastewater treatment are not required, and furthermore, there is no need to worry about secondary pollution due to wastewater, and the drawbacks of the wet n calculation method can be overcome.

(3) Since desulfurization and denitration are carried out simultaneously, there is no need to worry about blockage or corrosion caused by acidic ammonium sulfate in the air heater.

(5) In addition, desulfurization and denitrification do not need to be performed in separate devices, but can be performed in one device, which not only allows the adsorption tower to be downsized, but also simplifies operation and maintenance. be able to.

[Brief explanation of drawings]

FIG. 1 shows the first step diagram for explaining the method of the present invention. In the figure, 1 is a desulfurization and denitrification process, 2 is a regenerated culm, and 4 is a moving bed. Patent applicant: Ishikawajima-Harima Ju] Nigyo Co., Ltd. Representative Patent Attorney: Makoto Kinuya

Claims (1)

[Claims] When desulfurizing and denitrating exhaust gas discharged from a combustor such as a boiler, ammonia is mixed into the exhaust gas, and then at least one metal component of vanadium, tungsten, germanium, titanium, niobium, copper, or iron is added to the exhaust gas. A method for desulfurizing and denitrating exhaust gas, characterized in that desulfurization and denitration are carried out by contacting with added activated carbon.