JPS59130522A - Dry desulfurizing method - Google Patents

Abstract

PURPOSE:To improve desulfurizing rate and to reduce cost by passing repeatedly waste gas zigzag through a moving bed of a dry desulfurizing agent in contact therewith along the flow direction thereof and using the deteriorated desulfurizing agent as a reducing agent for a sulfur recovering stage. CONSTITUTION:The inside of a desulfurizing column 1 is segmented to many upper and lower stages by plural guide plates 8 to form a zigzag passage 9. The waste gas 10 through an introducing port 4 ascends zigzag by intersecting repeatedly orthogonally the moving bed 6 of a desulfurizing agent and is thus desulfurized. The desulfurizing agent adsorbing SOx is fed through a passage 13 to a regenerating tower 2, where the desulfurizing agent is heated and regenerated. The powdered desulfurizing agent is separated with a screen 17 and thereafter a regenerated desulfurizing agent 20 is fed through a passage 19 to the column 1, and is thus cyclically used. A part of the agent 20 is fed together with a powdered agent 18 through a passage 21 to a reducing column 3 and is used as a reducing agent. The adsorbed gaseous SO2 from the column 2 is fed to the column 3 where simple substance sulfur 26 is produced. A high desulfurizing rate is obtd. by using the inexpensive desulfurizing agent having relatively low activity such as carbonized char of brown coal and the above-mentioned method is economical.

Description

[Detailed Description of the Invention] Desulfurization treatment is carried out by repeatedly bringing exhaust gas into contact with the moving bed of the agent in a meandering manner along the flow direction, and the deteriorated desulfurization agent is used as a reducing agent in the sulfur recovery process. The present invention relates to a dry desulfurization method in which even coal with relatively low activity and low degree of carbonization can be used as a desulfurization agent, and running costs can be greatly reduced.

In general, combustion equipment such as large boilers in thermal power plants etc. contain sulfur oxides (hereinafter abbreviated as SOX) such as sulfur dioxide gas in the exhaust gas emitted from them. A flue gas desulfurization device is provided to remove Sox to prevent air pollution.

The desulfurization methods used in this flue gas desulfurization equipment can be roughly divided into wet desulfurization methods that use an aqueous solution such as calcium carbonate as a desulfurization agent, and dry desulfurization methods that use granular activated carbon as a desulfurization agent. Desulfurization methods require a large amount of water to produce the desulfurization agent, wastewater must be treated after desulfurization, and secondary pollution caused by this wastewater must be prevented, among other problems. However, in the latter dry desulfurization method,
It has the advantage of not having the problems mentioned above, and its versatility is attracting attention.

However, despite the dry desulfurization method having the above-mentioned advantages, it has not been fully put into practical use due to the following reasons, such as insufficient desulfurization performance or high desulfurization cost. is the current situation.

(1) When semi-formed coke of steam coal or lignite is used as a desulfurization agent.

In the conventional method, semi-formed coke is
Since residual carbon from semi-formed coke used as a reducing agent for sulfur recovery is used as a desulfurization agent, the desulfurization activity is inherently low, and the desulfurization activity increases by adsorption and reuse of the desulfurization agent. It was not possible to obtain sufficient performance.

Furthermore, when bringing the desulfurization agent into contact with the exhaust gas, methods with low desulfurization efficiency such as the so-called single-stage cross-flow moving bed method, which only brings the desulfurization agent into contact with the exhaust gas once, are used. The method using formed coke cannot achieve a high desulfurization rate and is difficult to put into practical use.

(2) When using a highly active desulfurizing agent.

High desulfurization can be achieved by using a highly active desulfurization agent, but this type of desulfurization agent is generally expensive, and a separate inexpensive carbon material is still required as reducing carbon for sulfur recovery. Furthermore, the desulfurization cost was extremely high and it was not economically viable at all, and as mentioned above, it was difficult to put it into practical use due to the fact that the reducing power of the used residual coal has already decreased and there is no use value. .

In particular, in the dry desulfurization method, approximately 50% of the desulfurization cost is the cost of supplementary desulfurization agent, so it has become desirable to obtain a high desulfurization rate by using a low-friction desulfurization agent.

The present invention has been devised to effectively solve the above-mentioned problems, and its purpose is to create a moving layer of dry desulfurization agent that flows down in one direction from the top to the bottom. The exhaust gas is passed repeatedly in a meandering manner along this flow direction to perform desulfurization treatment, and the deteriorated desulfurization agent is used as a reducing agent in the sulfur recovery process, thereby reducing carbonization with relatively low activity. To provide a dry desulfurization method in which carbonized char of high-grade coal (for example, lignite, lignite, bituminous coal, etc.) can be used as a desulfurization agent, and running costs can be greatly reduced.

In the present invention, when bringing the exhaust gas and the desulfurization agent into contact,
Rather than desulfurizing a highly concentrated exhaust gas by contacting it once with a large amount of desulfurizing agent, it is possible to achieve a higher desulfurization rate by bringing the exhaust gas into contact with a small amount of the desulfurizing agent multiple times to gradually lower the SOa degree, and to reduce the degree of de-sulfurization. This was achieved by discovering that the desulfurization agent obtained by the above method can be fully utilized as reducing carbon in the sulfur recovery process.

Hereinafter, a preferred embodiment of the present invention will be described in detail based on the accompanying drawings.

The figure is a schematic system diagram showing a dry desulfurization apparatus for carrying out the method according to the present invention.

First, to explain an example of this device, this device includes a desulfurization tower 1 that desulfurizes exhaust gas, a desulfurization agent regeneration tower 2 that regenerates the used desulfurization agent, and a desulfurization agent regeneration tower 2 that regenerates the S02 gas desorbed within this regeneration tower 2. It mainly consists of a reduction tower 3 for recovering elemental sulfur.

The above-mentioned desulfurization tower 1 is used to carry out the operation which is a feature of the present invention, and a treatment gas inlet 4 for introducing the exhaust gas to be treated is provided below the desulfurization tower 1, and a desulfurization tower 1 is provided above the desulfurization tower 1. A treated gas outlet 5 is provided for discharging the treated exhaust gas to the outside of the tower. A desulfurizing agent moving layer 6 is formed in the desulfurizing tower 1, and the desulfurizing agent flows downward from the top to the bottom at a constant speed or intermittently. It is now possible to do so. Inside the desulfurization tower 1, two guide plates 8, 8 are installed at different mounting heights so as to divide the inside of the tower 1 into three stages, upper and lower, with the moving bed 6 at the center. As shown in the figure, a meandering passage 9 is formed that extends upward from the IJ side of the tower 1.

Therefore, the exhaust gas 10 introduced from the bottom of the column 1 repeatedly crosses the moving bed 6 at right angles and ascends in the passage 9 in a meandering manner. In addition, in the illustrated example
Although it is formed in three stages below 1, it may be formed in more stages so that the exhaust gas and the desulfurizing agent are brought into contact three times or more.

The regeneration tower 2 is for regenerating the desulfurization agent that has adsorbed SOx discharged from the desulfurization tower 1, and a conventional device is used. Most of the desulfurizing agent regenerated in the regeneration tower 2 is circulated and transferred to the desulfurizing tower 1, as will be described later, and is used again as a desulfurizing agent.

The reduction tower 3 is a device for recovering elemental sulfur by reducing the SO2 gas desorbed in the regeneration tower 2, and as will be described later, the reducing agent used in the reduction tower 3 A part of the regenerated desulfurization agent discharged from the regeneration tower 2 is used as the (reduced coal).

Next, the method according to the present invention will be explained based on the above device example.

Exhaust sludge 10 discharged from combustion equipment (not shown) such as a boiler is introduced into the desulfurization tower 1 from a treated sludge inlet 1]4 provided at the 1st part of the desulfurization tower 1.

This exhaust gas 10 contains, for example, SO-iloooppm.

The temperature is about 130°C, and first, the lower part of the moving layer 6
3 in a direction perpendicular to this, passing through and contacting the SOx
A part of it is removed by adsorption. Next, this exhaust gas is directed upward along the meandering path 9, and at the middle stage of the moving layer 9.
/:3, the SO is adsorbed and removed by passing it in contact with it in the same way as if it were perpendicular to this. Furthermore, this exhaust gas is caused to ascend upward in the passage 9 in a meandering manner, and is brought into contact with the upper 1/3 of the moving layer 6 again perpendicularly thereto, thereby eliminating the SOx contained in the exhaust gas. It absorbs dirt. The desulfurized exhaust gas is then discharged to the outside of the system from the treated gas outlet 5 at the top of the tower.

On the other hand, in this desulfurization tower 1, the regenerated desulfurization agent transferred from the regeneration tower 2 side and the dry desulfurization agent 7a supplied from the hopper 7 are mixed together, and the desulfurization agent is passed through the desulfurization agent population 11. The moving layer 6 is formed by flowing down continuously or intermittently at a constant speed. As the desulfurization agent introduced from the hopper 7, carbonized char of coal with relatively low activity and low degree of carbonization, such as lignite, lignite, and non-caking bituminous coal, is used.

The desulfurizing agent flowing down while forming the moving layer 6 is brought into contact with the exhaust gas as described in 1.
is discharged to the outside of the tower from the outlet 12 in a state in which it has been adsorbed.

Therefore, while the exhaust gas 10 rises inside the tower 1, a total of 3
Desulfurization treatment is carried out by contacting with a multiple desulfurization agent, and the SO concentration is sequentially reduced over three stages.

After the desulfurization agent adsorbing a large amount of SO is discharged from the desulfurization tower 1, it is sent to the regeneration tower 2 via the passage 13 and introduced therein from the regeneration desulfurization agent inlet 14. The introduced used desulfurizing agent gradually flows down inside the regeneration tower 2, and is heated to about 400° C. by an inert gas 15 such as nitrogen, which is heated and supplied from below, and desorbs the adsorbed S02. Furthermore, the desulfurization agent is regenerated by being washed by this inert gas.

After this regenerated desulfurization agent is discharged from the desulfurization agent outlet 16 to the outside of the tower, it is passed through a sieve 17, and while the desulfurization agent 18 that has been abraded and powdered while flowing down the tower is separated and removed, a large amount of the desulfurization agent 18 is separated and removed. A portion of the regenerated desulfurization agent (-j) is circulated through the passage 19 to the desulfurization tower 1 and used as a desulfurization agent again. New desulfurization agent is added and replenished.

Part of the regenerated desulfurizing agent 20 is branched off and transferred together with the separated powdered desulfurizing agent 18 to the reducing tower 3 through the passage 21, where it is used as a reducing agent.

On the other hand, the SO2 desorbed in the regeneration tower 2 is discharged together with the inert gas from the regeneration gas outlet 22 provided at the top of the regeneration tower, and is transferred to the reduction tower 3 side via the passage 23.
The reducing gas is introduced into the lower part of the tower 3 through the reducing gas port 24 .

A mixture of regenerated desulfurization agent (including powdered desulfurization agent) supplied from the regeneration tower 2 side and a used reducing agent to be described later is introduced and filled into the reduction tower 3 via the reducing agent population 25. It's flowing down inside. Then, this reducing agent (reduced coal) is heated and maintained at an appropriate temperature by burning a part of it, and comes into contact with the S02 gas introduced above, which is flowing down inside the tower and rising inside the tower. It acts as a reducing agent and reduces this S02 gas to produce elemental sulfur 26. Note that in order to increase the sulfur recovery rate, a normal Claus reactor should be combined.

On the other hand, the spent reducing agent (reducing carbon) 27 that remains without contributing to the reduction reaction is discharged from the reducing agent outlet 28 at the bottom of the reducing tower 3 to the outside of the tower, is passed through a sieve 29, and is abraded in the reducing tower 3. Only the pulverized coal 30 generated is removed.

The used reduced coal 27a from which only the pulverized coal has been removed is mixed with the regenerated desulfurizing agent 20a that is partially transferred from the regeneration tower 2 side, and is transferred to the reduction tower 3 via the passage 21 where it is circulated again as a reducing agent. will be used.

As described above, according to the present invention, in the desulfurization tower 1, the exhaust gas is made to meander and is brought into contact multiple times with newer desulfurization agent that does not adsorb much SO at each stage. The desulfurization rate can be improved compared to the case where the material is brought into contact with the agent only once. This means that it is not necessary to use relatively highly active and expensive desulfurization agents, i.e. relatively cheap and less active desulfurization agents such as carbonized char of lignite, brown coal etc. can be used instead. It is also possible to obtain a high desulfurization rate.

Among the desulfurization agents that are still recycled in the desulfurization process,
A portion of the degraded recycled desulfurization agent is extracted and used as a reducing agent, eliminating the need for new carbon material.

Next, the results of desulfurization treatment performed using the method according to the present invention will be described.

The desulfurization conditions are as follows.

(1) Desulfurization gas composition (exhaust gas) SO2: 1000
1000pp:' 1 2.2 (vo 1%)
02:5.1 (//) H2O:, 6.4 (tt) N: 762 (〃) (2) Adsorption conditions Temperature = 130-140°C5v (gas space velocity): '4.00 NM3/I+ r IW
5 Desulfurization tower desulfurization agent residence time: 40 hr (3) Desulfurization agent Under the desulfurization conditions of brown coal carbonization char or higher, the so-called three membrane according to the present invention is By adopting the medium flow moving bed method, a portion of the degraded regenerated desulfurization agent was sent to the sulfur recovery process and used as a reducing agent (reduced coal), resulting in a desulfurization rate of 90% compared to the conventional method. According to this method, the desulfurization rate could be improved to 98%.

Indeed, the sulfur yield in the sulfur recovery process, including the Claus reaction, was maintained at 93% or higher, achieving a high recovery rate.

In this way, by adopting the multi-stage cross-flow moving bed method, it is possible to maintain a high desulfurization rate using the carbonized char of lignite, which is an inexpensive and relatively low-activity desulfurization agent.

In addition, some of the deteriorated regenerated desulfurization agent can be reduced in particle size or powdered and used as a reducing agent, making it possible to effectively utilize carbonaceous material, which is economical. In particular, it is necessary to burn part of the reduced coal in order to raise the reduction reaction temperature, but as mentioned above, it is more economical since the reduced coal is inexpensive.

In summary, the method according to the present invention can exhibit the following excellent effects.

(1) Since the exhaust gas is made to meander and is brought into contact with a newer desulfurizing agent that does not adsorb much SO at each stage multiple times, when the exhaust gas is brought into contact with a large amount of desulfurizing agent only once as in the conventional example. The desulfurization rate can be improved compared to the conventional method.

(2) Therefore, it is possible to use inexpensive carbonized char such as lignite or lignite, which is inexpensive and has relatively low activity, without using an expensive desulfurizing agent, which is economical.

(3) Compared to the conventional single-stage system, the desulfurization rate at the bottom of the desulfurization tower may be lower, so the SO
A desulfurizing agent containing a large amount of can be used. This means that the circulation amount of the desulfurizing agent can be reduced, and therefore, the loss of the desulfurizing agent due to wear etc. can be suppressed. Furthermore, the reduction in the amount of regeneration can reduce heating regeneration energy, making it more economical. can be improved.

(4) The degraded regenerated desulfurization agent is sequentially used as a reducing agent, and the insufficient amount is constantly supplied to the desulfurization tower, so the desulfurization agent in the desulfurization tower is always maintained in a relatively fresh state, further improving the desulfurization rate. be able to.

(5) Since the regenerated desulfurization agent whose desulfurization performance has deteriorated is sequentially extracted from the desulfurization process and used as the SO2 reducing agent, there is no need to use new carbon material separately, which is economical.

(6) For the reasons mentioned above, desulfurization costs and equipment running costs can be significantly reduced.

[Brief explanation of the drawing]

The figure is a schematic system diagram showing a dry desulfurization apparatus for carrying out the method according to the present invention. In the figure, 1 is a desulfurization tower, 2 is a regeneration tower, 3 is a reduction tower, 6 is a moving bed, 7a is a dry desulfurization agent, 8 is a guide plate, 9 is a meandering passage, 10 is an exhaust gas, and 20 is a regeneration desulfurization 20a is a part of the regenerated desulfurization agent, and 26 is elemental sulfur. Patent Applicant: Nobuo Kinutani, Patent Attorney, Ishikawajima-Harima Heavy Industries Co., Ltd.

Claims (1)

[Claims] The exhaust gas is brought into contact with a dry desulfurization agent to adsorb and remove the sulfur oxides contained in the exhaust gas, and then the sulfur oxides are separated from the desulfurization agent that has adsorbed the sulfur oxides to regenerate the desulfurization agent and the separated sulfur. In a dry desulfurization method in which elemental sulfur is recovered by reducing oxides, a moving layer is formed in which the dry desulfurizing agent moves in one direction, and the flow of the dry desulfurizing agent from the downstream side to the upstream side is formed in the moving layer. Sulfur oxides in the exhaust gas are adsorbed and removed by repeatedly passing the exhaust gas along the direction orthogonally to each other, and then heating the desulfurizing agent that has adsorbed the sulfur oxides to separate the sulfur oxides and desulfurization. After that, the regenerated desulfurization agent is recycled as the dry desulfurization agent, and a part of the regenerated desulfurization agent is used as a reducing agent for the separated sulfur oxides. Characteristic dry method