JPS5843223A - Dry type desulfurization and denitration method - Google Patents

Abstract

PURPOSE:To prevent blocking of a flue or the inlet of a moving bed due to production and attachment of ammonium sulfate, to reduce pressure drop of flue gas, and to prevent its uneven flow, by injecting ammonia directly into the moving bed of a carbonaceous adsorbent. CONSTITUTION:Ammonia or diluted ammonia 3 is directly injected into the moving bed 4 of a carbonaceous adsorbent 2 through an ammonia distributor 7, and a flue gas 1 is passed through the bed 4 at right angles to the moving direction of the bed 4 at the same time to remove SOx and NOx from the gas 1, thus permitting ammonium sulfate or hydrogensulfate to be produced only on the adsorbent 2 moving in the bed 4, and carried out of the bed 4 continuously, therefore prevented from blocking the flue or the inlet of the bed 4 as often happened in the conventional process caused by deposition and growth of the sulfate etc. on the perforated plate or the louvers of the inlet, pressure drop of the gas 1 to be reduced, uneven flow of the gas 1 to be prevented, and the uniform flow to be ensured for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an ammonia injection method in a dry desulfurization and denitrification method.

The dry simultaneous desulfurization and denitration method involves passing waste gas through a moving bed formed by a carbonaceous adsorbent to remove sulfur oxides from the waste gas and at the same time removing nitrogen oxides by adding ammonia. well known. In this case, the conventional method is to dilute ammonia alone with ammonia gas or other suitable gas, and then inject it into the waste gas duct before it flows into the moving bed (see Figure 1). That is, in the figure, the waste gas 1 is mixed with the temponia mixing device 6.
The ammonia gas or ammonia-containing gas injected from the carbonaceous adsorbent 2 is brought into contact with the moving bed 4 in cross flow. In this method, ammonium sulfate or acidic ammonium sulfate is generated and adhered to the flue and the exhaust gas inlet part of the moving layer held by a louver or perforated plate, and grows, reducing the flow path area of the exhaust gas. This has the disadvantage that it increases the pressure loss of the gas, causes the waste gas to drift, and completely reduces the denitrification and denitrification performance.

In addition, the temperature of the waste tortoise handled in the dry simultaneous desulfurization and denitrification equipment is usually between pleasant temperature and 180℃, and in this temperature range, the reaction between ammonia and sulfur oxides precedes the reaction between ammonia and nitrogen oxides. The conventional method of using a single moving bed and injecting ammonia into the waste gas before it flows into the moving bed has the disadvantages that a high denitrification rate cannot be obtained and that the amount of ammonia consumed is significantly increased. there were. Therefore, the second
As shown in the figure, two moving beds made of carbonaceous adsorbent 2 are installed, and after 1L of waste gas passes through the first moving bed 4r, it passes through the second moving bed 5, and before the first moving bed. Then, either no ammonia is added or a small amount of ammonia 6' is added, and ffL'fr is mainly removed by the adsorption action of the carbonaceous adsorbent, and then three doses of ammonia are injected into the waste gas that has passed through the first moving bed pipe. A method has also been proposed in which denitrification is mainly carried out in the second moving bed, but this method has the disadvantage of requiring two moving beds 'fr, which increases the cost of the equipment.

The inventors of the present invention have conducted extensive research to eliminate all of the drawbacks of the conventional methods described above, and have found that this objective can be achieved by adding ammonia directly to a moving bed made of an all-carbon monocarbon adsorbent. This discovery led to the present invention.

That is, in the present invention, waste gas containing sulfur oxides and nitrogen oxides is passed through a moving bed formed by a carbonaceous adsorbent, and sulfur oxides and nitrogen are simultaneously removed by the reducing action of ammonia added separately. This dry desulfurization and denitrification method for removing oxides is characterized by directly injecting ammonia into a packed bed of carbonaceous adsorbent.

Examples of carbonaceous adsorbents used in and-- include commonly used activated carbon and semi-formed coke, and ammonia is used in a tube diluted with ammonia gas or an appropriate gas. Further, the temperature of the moving layer is usually maintained at room temperature to 180°C.

FIG. 3 shows one embodiment of the present invention, in which ammonia or diluent gas of ammonia 3t-1 and an ammonia dispersion device 7t- installed inside a moving bed 4 formed by a carbonaceous adsorbent 2 are shown. The waste gas 1 is injected directly into the moving bed through the pump, and at the same time the waste gas 1 is passed in cross-flow contact with the moving bed.

According to the method of the present invention, ammonia is directly injected into the moving carbonaceous adsorbent layer, so ammonium sulfate and acidic ammonium sulfate are generated only on the moving carbonaceous adsorbent and flow out of the moving layer. Continuously discharged.

Therefore, unlike the conventional method, there is no clogging caused by the formation and growth of ammonium sulfate and acidic ammonium sulfate in the porous holes and loopers at the entrance of the moving bed in the flue, and as a result, the pressure loss of the waste gas is significantly reduced. At the same time, uneven flow of waste gas is prevented, and a uniform flow can be ensured over a long period of time.

FIG. 4 shows another embodiment in which a plurality of ammonia gas dispersion devices 7, 7' are installed in a single moving bed to inject ammonia in portions. In this case, the same effect as when a plurality of moving beds are installed is achieved, so that the amount of ammonia consumed can be reduced and the denitrification rate can be improved with a simple device. In other words, the effect of reducing the equipment cost and operating cost of the dry-type simultaneous desulfurization and denitrification equipment is significant.

It goes without saying that the direct ammonia injection method according to the present invention is not limited to a single moving layer.

Is this invention based on the following examples and comparative examples? This will be explained in more detail.

Example 1 Bo2 performance 860PPms NOx concentration 170pp
7 m of heavy oil combustion waste gas is passed through a moving bed of granular activated carbon with a moving amount of 40 m at a temperature of 155°C and a flow rate of 10.001 n'/H, and 7 m of ammonia is diluted with the waste gas after passing through the moving bed. The waste gas was injected directly into the moving bed through a gas dispersion device installed immediately after the louver on the inlet side. The amount of ammonia injected was α45-37H. The pressure loss of the waste gas in the moving bed changes over time as shown in Figure 6. There is almost no change in the pressure loss. Also, the 802 concentration in the waste gas exiting the moving bed after 100 hours is 80 ppm %NozNOx concentration Oppnc Te @
Friend.

Comparative Example 1 The same equipment, waste gas conditions, movement amount of granular activated carbon, and ammonia injection amount as in Example 1 were used, and the same dilution method and dilution ratio were used, but ammonia was injected into the waste gas duct before flowing into the moving bed.

The change in pressure loss of waste gas in the moving bed over time is shown in Figure 5. The pressure drop gradually increased and reached 255 Aq after 168 hours.

Also, SO in the moving bed heavy waste gas after 100 hours.

The concentration is 'I Ppm, NO, the concentration is 100 ppm
m was 0 Example 2 80 wet density? OOppm5NOx concentration! l OOpp
m of heavy oil combustion waste gas was passed through a moving bed of granular activated carbon with a moving amount of 80 t/H at a temperature of 155°C and a flow rate of 10,001 n"/H. Ammonia was diluted with the waste gas after passing through the moving bed.
To the moving bed inlet part (L 1 @ 1m/H.

The 803 concentration in the waste gas after passing through the moving bed was 0 to 2 ppm.
) The iox concentration was 65 ppm, 4〇,;,・1゜Comparative Example 2'・ Using the same equipment, exhaust gas conditions, and moving amount of granular activated carbon as in Example 2, ammonia was diluted in the same way and entered the moving bed. Injected only in part. 80% in the waste gas after passing through the moving bed. The concentrated Fi was O~2 ppm, and the NOx concentration was 156 ppm.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams showing the ammonia injection method according to the company's conventional method, vK5 and Figure 4 are schematic diagrams showing the ammonia injection method according to the present invention, and Figures 5 and 6 are respectively the case using the conventional method. It is a graph showing the change in pressure loss of waste gas passing through the moving bed over time in the case of the present invention. Agents 1) Akira's agent Ryo Hagiwara - Figure 1 l; ↓

Claims (2)

[Claims] (1) passing waste gas containing sulfur oxides and nitrogen oxides through a moving bed formed by a carbonaceous adsorbent;
In the dry desulfurization and denitration method for removing nitrogen oxides at the same time as sulfur oxides through the reducing action of separately added ammonia, the above method is characterized in that ammonia is directly injected into a packed bed of carbonaceous adsorbent. (2) A method according to claim 1, characterized in that ammonia gas or ammonia-containing gas is supplied from a plurality of dispersion devices provided inside a single moving bed made of a carbonaceous adsorbent.