JPS58223426A - Dry type stack gas desulfurization method - Google Patents

Abstract

PURPOSE:To improve the regeneration rate of a desulfurizing agent and the efficiency in recovery of sulfur and to prevent the corrosion in a regeneration column by by-passing a cleaning gas for regeneration of the desulfurizing agent in the heating part on the uppermost stream side of a moving layer and discharging the same. CONSTITUTION:A desulfurizing agent adsorbed with SOX in a desulfurization column is introduced through an introducing port 16 into a regeneration column 15, and is heated in the heating part 17 in the internal upper part of the column 15 to desorb the SOX. The desulfurizing agent descending in the column 15 is further brought into contact with the cleaning gas from an introducing port 18 and is cooled in a cooling part 20, whereafter the agent is transferred again from a discharge port 21 into the desulfurization column 10. The cleaning gas ascends in countercurrent with the moving layer of the desulfurizing agent descending in the column 15 and is discharged from a cleaning gas discharge port 19 formed in the downflow part of the part 17. Since the SOX of a high concn. desorbed from the desulfurizing agent is discharged on the downstream side of the part 17, there is no possibility that the SOX cooled and desorbed by contact with the unheated desulfurizing agent in the port 16 is adsorbed again on the desulfurizing agent as in the prior art, and the corrosion by the condensation in the column 15 is prevented. The SOX of a high concn. is discharged at high temp. and the rate of recovery of S is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry flue gas desulfurization method for removing sulfur oxides from combustion exhaust gas discharged from combustion equipment such as boilers, and particularly improves desulfurization agent regeneration rate and sulfur recovery efficiency. The present invention also relates to a dry flue gas desulfurization method that prevents corrosion within a regeneration tower.

In general, as a dry flue gas desulfurization method, the sulfur oxides in the gas are adsorbed and removed using a desulfurization agent, the desulfurization agent that has adsorbed the sulfur oxides is heated, and then the gas is washed to regenerate it as a desulfurization agent. A method is known in which sulfur dioxide released from a desulfurizing agent is reduced during heating of the desulfurizing agent to recover sulfur.

Specifically, as shown in Figure 1, combustion exhaust gas (hereinafter referred to as exhaust gas) discharged from combustion equipment such as a boiler is first introduced into a desulfurization tower 1, where it comes into contact with activated carbon, which is a desulfurization agent, and oxidizes the sulfur in the exhaust gas. substances (SOx) are adsorbed and removed by activated carbon. The treated exhaust gas from which sulfur oxides have been removed is discharged outside the system. On the other hand, the activated carbon that has adsorbed sulfur oxides is transferred to the regeneration tower 2, where it is heated and sulfur dioxide is released. The activated carbon from which sulfur dioxide has been removed by heating is gas-washed and then returned to the desulfurization tower 1 to be reused as a desulfurization agent. Further, the sulfur dioxide separated from the activated carbon in the regeneration tower 2 is transferred together with the cleaning gas to the sulfur recovery tower 3, where it is reduced by a reducing agent such as coal and the sulfur is recovered.

By the way, conventionally, in the regeneration tower 2, the desulfurization agent is supplied through the desulfurization agent inlet 4 formed at the upper end of the regeneration tower 2, as shown in FIG.
The desulfurizing agent is introduced from the column, descends inside the column while being heated by a heating section 5 provided at the upper part of the column, and is discharged from a regenerated desulfurization agent outlet 6 formed at the lower end of the column. on the other hand,
The cleaning gas for cleaning the heat-treated desulfurization agent is supplied to the regeneration tower 2.
Highly concentrated carbon dioxide is introduced from the cleaning gas introduction lower formed at the bottom, rises inside the column countercurrently to the moving layer of the desulfurization agent, and is released from the desulfurization agent through the cleaning gas outlet 8 formed at the top. It is discharged to the outside along with sulfur.

However, since the cleaning gas discharge port 8 is formed above the heating section 5 of the regeneration tower 2, the cleaning gas or high concentration sulfur dioxide discharged from the discharge port 8 flows into the desulfurization agent inlet 4 in the upper part of the regeneration tower 2. It came into contact with the unheated desulfurization agent introduced into the tower and was cooled. Therefore, a problem arises in that the sulfur dioxide released by heating is adsorbed by the desulfurizing agent again, and the desulfurizing agent cannot be regenerated sufficiently.

In addition, when the cleaning gas or high concentration sulfur dioxide is cooled, a part of it condenses inside the regeneration tower 2, and the SO contained therein becomes dew.
There was a problem that ions such as 4" and ct- corroded the inside of the regeneration tower 2.2 Also, when recovering sulfur from high concentration sulfur dioxide in the sulfur recovery tower 3, approximately 800
Sulfur dioxide is reduced at a temperature of
The reduction process was carried out by burning part of the reducing agent inside the tank to raise the temperature. Therefore, a large amount of expensive reducing agent must be used, which is not economical.

Furthermore, combustion air is supplied inside the sulfur recovery tower 3 to burn the reducing agent, but when the combustion air is supplied into the recovery tower 3, the sulfur dioxide inside the υ tower is It was diluted and the sulfur recovery efficiency was not good.

Furthermore, in order to solve the above-mentioned problems, a method has been attempted in which heated sand is introduced into the regeneration tower 2 from the upper part, and the sand is brought into direct contact with the desulfurizing agent as a heat medium to exchange heat. However, after regenerating the desulfurization agent, the recycled desulfurization agent and sand had to be separated, and there were problems in the separation process.

In view of the above-mentioned conventional problems, the present invention was devised to effectively solve the problems.The purpose of the present invention is to introduce a cleaning gas from the downstream side to the upstream side of the desulfurizing agent moving layer. By making countercurrent contact and causing the cleaning gas to bypass the heating section on the most upstream side of the moving bed and flow out, it is possible to improve the desulfurization agent regeneration rate and sulfur recovery efficiency, and to prevent corrosion in the regeneration tower. It is an object of the present invention to provide a dry flue gas desulfurization method that can prevent

The method according to the present invention will be explained below based on the accompanying drawings.

FIG. 3 is a process diagram for explaining the method according to the present invention. 10 is a desulfurization tower, into which exhaust gas discharged from combustion equipment such as a boiler is introduced through an exhaust gas inlet 11 formed on the side thereof. The flue gas introduced into the desulfurization tower 10 is introduced from the desulfurization agent supply port 12 formed at the top of the desulfurization tower 10 and passes orthogonally through a mobile desulfurization agent layer (activated carbon) that descends inside the tower, thereby reducing the amount of waste gas in the flue gas. sulfur oxides are adsorbed and removed by the desulfurization agent. Then, the treated exhaust gas from which yellowish oxides have been removed is discharged from the exhaust gas outlet 13 to the outside of the system.

Further, the desulfurization agent that has adsorbed sulfur oxides is discharged from the desulfurization agent outlet 14 formed at the bottom of the desulfurization tower 10, and is discharged from the regeneration tower 1.
Transferred to 5. The desulfurizing agent transferred to the regeneration tower 15 is passed through the desulfurizing agent inlet 1 formed at the upper end as shown in FIG.
6 into the tower and descend there. Regeneration tower 15
The desulfurizing agent descending inside the tower first passes through a heating section 17 provided at the upper part of the tower, where it is indirectly heat exchanged and heated to 30
Heated from 0 to 600 r. The desulfurizing agent releases the adsorbed sulfur dioxide when heated.

The heat-treated desulfurizing agent further descends within the regeneration tower 15, but while descending, it comes into contact with the cleaning gas introduced from the cleaning gas inlet 18 and is thereby cleaned. The cleaning gas is
The cleaning gas is introduced into the tower from the cleaning gas inlet 18 formed at the lower part of the regeneration tower 15, and is caused to flow countercurrently from the downstream side to the upstream side of the desulfurization agent transfer layer that is heated and descends inside the tower, and rises inside the tower. The cleaning gas is discharged from a cleaning gas outlet 19 formed at a downstream portion of the heating section 17 . The desulfurizing agent that has been washed with the cleaning gas and regenerated passes through the cooling section 20 provided at the lower part of the regeneration tower 15, where it is cooled by indirect heat exchange, and then is sent to the lower end of the regeneration tower 15. The regenerated desulfurization agent is discharged from the formed regenerated desulfurization agent outlet 21 and transferred to the desulfurization tower 10 again, where the exhaust gas is desulfurized.

On the other hand, the highly concentrated sulfur dioxide released from the desulfurization agent in the regeneration tower 15 is discharged together with the cleaning gas at a high temperature of 300 to 600 C from the cleaning gas outlet 19 formed in the downstream part of the heating section 17, and is then removed from the sulfur recovery tower. 22. The highly concentrated sulfur dioxide transferred to the sulfur recovery tower 22 is introduced into the tower from the sulfur dioxide inlet 23, where it is combined with the reducing agent (coal, etc.) introduced from the reducing agent inlet 24 and about 800
C and thereby be reduced to recover elemental sulfur.

In the sulfur recovery tower 22, a part of the reducing agent is burned in order to maintain the temperature inside the tower at about 800C, and combustion air is supplied to the inside of the tower to burn this reducing agent. .

In addition, the desulfurization agent is consumed due to desulfurization and regeneration processing.

When the desulfurization agent is worn out, new desulfurization agent is to be replenished into the desulfurization tower 10.

Therefore, since the highly concentrated sulfur dioxide released from the desulfurization agent is discharged downstream of the heating section 17, the sulfur dioxide is removed from the desulfurization agent that has not been heated or heated, unlike the conventional desulfurization agent introduction port 16. There is no risk of cooling due to contact with the desulfurizing agent, and therefore, the released sulfur dioxide will not be adsorbed by the desulfurizing agent again.

In addition, since the sulfur dioxide is not cooled in the regeneration tower 15, no dew condensation occurs therein, thereby preventing corrosion inside the regeneration tower 15 due to ions such as 5042Ct- contained in the sulfur dioxide or cleaning gas. can do.

Historically, since highly concentrated sulfur dioxide was discharged downstream of the heating section 17, it could be discharged at a high temperature of 300 to 600C. Therefore, when reducing sulfur dioxide in the sulfur recovery tower 22, the It is economical because it requires less reducing agent to be burned to raise the temperature.

Moreover, since less air for reducing agent combustion is supplied into the sulfur recovery tower 22, the dilution rate of sulfur dioxide by the air is reduced, and the sulfur recovery efficiency is improved.

In addition, since the cleaning gas was introduced countercurrently from the downstream side to the upstream side of the heat-treated desulfurizing agent moving bed, sulfur dioxide is effectively separated from the desulfurizing agent (!:), and the regeneration efficiency is improved. A high degree of regeneration is possible.

As shown in FIG. 5, a desorption gas inlet 25 is formed at the upper end of the regeneration tower 15, and the desorption gas is introduced from the upper part of the tower through the desorption gas inlet 25. If the cleaning gas is allowed to flow out from the cleaning gas outlet 19 after passing through the heating section 17, the highly concentrated sulfur dioxide discharged from the cleaning gas outlet 19 will be more effectively discharged, and an excellent effect will be exhibited. do.

As is clear from the above explanation, the present invention exhibits the following excellent effects.

(1) Since the sulfur dioxide is discharged downstream of the heating section, the sulfur dioxide released from the desulfurization agent does not come into contact with the unheated desulfurization agent and be cooled. Therefore, the 11111 sulfur dioxide removed from the desulfurization agent is not adsorbed by the desulfurization agent again.

(2) Since sulfur dioxide is cooled in the main tower and does not condense, S04. Corrosion inside the regeneration tower due to ions such as Ct can be prevented, and the durability of the regeneration tower can be improved.

(3) Since the cleaning gas is introduced in a countercurrent manner from the downstream side to the upstream side of the heat-treated & sulfur agent moving bed, sulfur dioxide can be effectively separated from the desulfurization agent, improving the amphibious efficiency. In addition, high-level regeneration can be performed.

(4) Due to the synergistic effect of the above (υ, (3)), the desulfurization agent regeneration rate is improved.

(5) Since sulfur dioxide is discharged downstream of the heating section, it can be discharged at a high temperature, and when sulfur dioxide is reduced in a sulfur recovery tower, it is burned to raise its temperature. It is economical as only a small amount of reducing agent is required.

(6) In addition, less air is needed for combustion of the reducing agent to be supplied into the sulfur recovery tower, so the dilution rate of sulfur dioxide by the air is small, and the sulfur recovery efficiency is improved.

(7) It exhibits excellent effects such as being able to improve the efficiency of the entire flue gas desulfurization device.

[Brief explanation of the drawing]

Figure 1 is a process diagram for explaining the conventional flue gas desulfurization method.
FIG. 2 is a schematic vertical cross-sectional view showing a conventional regeneration tower, FIG. 3 is a process diagram for explaining the flue gas desulfurization method according to the present invention, and FIG.
This figure is a schematic vertical sectional view showing the regeneration tower of FIG. 3, and FIG. 5 is a schematic vertical sectional view showing a modification of the regeneration tower. In the figure, 10 is a desulfurization tower, 15 is a regeneration tower, 17 is a heating section, 1
8 is a cleaning gas inlet, 19 is a cleaning gas outlet, and 22 is a sulfur recovery tower. Patent applicant: Patent attorney representing Ishikawajima-Harima Heavy Industries Co., Ltd.
Nobuo Kinuya

Claims (1)

[Claims] Sulfur oxides in exhaust gas are adsorbed and removed by a desulfurizing agent, and the desulfurizing agent that has adsorbed sulfur oxides is heated and gas washed to regenerate it as a desulfurizing agent, and the sulfur dioxide released from the desulfurizing agent is reduced to produce sulfur. In the dry flue gas desulfurization method that recovers
A moving layer of the desulfurization agent is formed, and the cleaning gas is introduced from the downstream side of the moving layer to the upstream side of the moving layer to bring about countercurrent contact, and the cleaning gas bypasses the heating section on the most upstream side of the moving layer and flows out. A dry flue gas desulfurization method characterized by: