JPS5851923A - Dry desulfurization of waste gas - Google Patents

Abstract

PURPOSE:To carry out the regeneration of a desulfurizing agent by heat desorption without deteriorating capacities thereof, by supplying steam to the heat desorbing and regenerating tower of a dry waste gas desulfurization apparatus to desorb a gas from the desulfurizing agent. CONSTITUTION:Steam 12 is supplied in the vicinity of the boundary part between the heating part 7 and the cooling part 9 of a dry waste gas desulfurization apparatus and raised to the side of the heating part while uniformly dispersed by a dispersing plate 13 having an L shaped cross area. By this mechanism, the desorbed gas desorbed from a desulfurizing agent 3 can be prevented from being diffused to the side of the cooling part 9 and can be prevented to be again readsorbed by the desulfurizing agent 3. As the result, the SO2 adsorbed desulfurizing agent is regenerated by heat desorption without generating the combustion of the desulfurizing agent and deteriorating the capacities of the regenerated desulfurizing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry flue gas desulfurization method, and particularly to a dry flue gas desulfurization method that includes a step of thermally desorbing and regenerating a desulfurizing agent that has adsorbed sulfur oxides in flue gas, and recycling and reusing it. Regarding.

In the dry flue gas desulfurization method, a desulfurization agent that has adsorbed 5 to 15% of sulfur oxides is regenerated by thermal desorption and recycled as a new desulfurization agent. Normally, a thermal desorption regeneration tower has a heating section at the top and a cooling section at the bottom.The desulfurizing agent that has adsorbed sulfur oxides is moved down from the top and guided to the heating section, and after thermal desorption, it is moved down to the cooling section for desulfurization. The regenerated desulfurization agent is obtained by cooling the agent. At this time, an inert gas is inserted into the boundary between the cooling section and the heating section in order to prevent the desorption gas from diffusing into the cooling section and causing readsorption and to increase the desorption efficiency in the heating section. Since using a pure gas such as N2 gas as the inert gas would be expensive, combustion exhaust gas with a low oxygen content was used.

However, if a trace amount of oxygen gas is contained, 400 to 50
In the heating section at a temperature of 0C, the carbonaceous desulfurization agent burns and its mechanical strength decreases, while oxygen is adsorbed on the surface of the desulfurization agent to form surface oxides, and the SO2 of the desulfurization agent is
This was a factor in reducing the adsorption rate.

The purpose of the present invention is to solve the problems of the prior art described above,
It is an object of the present invention to provide a dry flue gas desulfurization method that can smoothly perform heat adsorption regeneration of a desulfurization agent without deteriorating its performance.

The present inventors discovered that N2 used for thermal desorption regeneration of desulfurization agent
As a result of searching for a purge gas to replace combustion exhaust gas with low oxygen content, they discovered that steam is extremely effective, and arrived at the present invention.

That is, in the present invention, a desulfurizing agent adsorbing sulfur oxides is moved and flowed down the heating section of a thermal desorption regeneration tower having a heating section and a cooling section at the upper and lower parts, respectively, to thermally desorb the sulfur oxides, and then the desulfurizing agent In the dry flue gas desulfurization method in which the desulfurization agent is regenerated by moving and flowing down into the cooling section, steam is supplied to the thermal desorption regeneration tower, and the steam and the desorption gas desorbed from the desulfurization agent are extracted from the heating section. Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

In FIG. 1, exhaust gas containing sulfur oxides is discharged from a boiler 1 and is introduced into an adsorption tower 2, where the sulfur oxides in the exhaust gas are adsorbed by a desulfurizing agent 3.

The desulfurizing agent 3 adsorbing sulfur oxides transported from the adsorption tower 2 is supplied to the upper hopper 5 of the thermal desorption regeneration tower 4 shown in FIG.
Move to flow down. FD temperature 400 in heating section 7? r~50
It is heated to 01T, and the sulfur oxides adsorbed on the desulfurizing agent 3 are desorbed. At this time, the heating medium 8A undergoes indirect heat exchange with the desulfurizing agent 3. The desulfurizing agent 3 that has been thermally desorbed moves down from the heating section 7 and reaches the cooling section 9, where it is cooled to a temperature of 150C or less. The cooling medium 8B exchanges indirect heat with the desulfurizing agent 3 that has been thermally desorbed to obtain a regenerated desulfurizing agent. Regenerated desulfurization agent 10 is valve 11
It is extracted while adjusting the extraction amount, and is recycled to the adsorption tower 2 for use.

In such a thermal desorption and regeneration process of the desulfurizing agent, steam 12 is supplied near the boundary between the heating section 7 and the cooling section 9, and after this steam 12 is uniformly dispersed by the dispersion plate 13 having an angular cross section, It rises to the heating section 7 side. As a result, the desorption gas desorbed from the desulfurization agent 3 is prevented from diffusing to the cooling section 9 side, and the desorption gas is prevented from being readsorbed by the desulfurization agent 3 again.

The mixed gas 14 of steam 12 and desorption gas is then introduced into a condenser 15 . Here, the mixed gas 14 is transferred to the condenser 1
The reason for introducing this in Section 5 is as follows.

When the desulfurizing agent adsorbing SO2 is thermally desorbed by steam and the combustion exhaust gas obtained by burning propane gas as an inert gas in a stoichiometric air state, the gas composition of stream 14 in the thermal desorption regeneration tower in Fig. 1 is as follows. Al on the street.

For combustion exhaust gas: 80214.5%, CO212.8
%, N20.36.2%, N236.6%,
For steam, So: 17.2%, CO2: 16.8%.

65.7% of H2O was obtained.

That is, when using steam as a purge gas,
The moisture concentration in the gas discharged from the thermal desorption regeneration tower is high. As a result, when a mixed gas of steam and desorption gas is supplied to a catalytic reduction tower with carbon and a Claus reactor to reduce sulfur oxides to elemental sulfur, in addition to the main reaction of formula (1), in addition to the main reaction of formula (1), 2) - The conversion rate to H2S caused by the side reactions of formulas (5) increases.

C+H20→C0-1-H,,......(2
) CO1H20→CO□10H2・・・・・・・・・(3
) Therefore, before feeding the mixed gas 14 to the catalytic reduction process, the moisture is fractionated to adjust the moisture concentration and to improve the efficiency of the reduction of SO2 to elemental sulfur.

In the condenser 15, supplying a cooling medium from stream 16;
By adjusting the amount of cooling medium while analyzing the gas discharged from stream 17, the H20/sO2 ratio in the gas discharged from stream 17 can be adjusted. The condensed water obtained in the condenser 15 is withdrawn from stream 18 and fed to a steam generator 19 for use as a source of steam for supplying the thermal desorption regeneration tower 4 . Steam generator 19 is supplied with water from stream 20 and generates steam 12. Note that steam can also be supplied from another system 21, so that the required amount of steam can be obtained.

The gas discharged from the condenser 15 is sent to a catalytic reduction tower 22, a sulfur condenser 23. Claus reactor 24 and sulfur condenser 25
It is recovered as elemental sulfur.

Here, if the steam concentration in the desorption gas is high, the condenser 1
In step 5, N20/So□ in the gas is adjusted, but I
-Even if the conversion rate to I□S becomes high, this H2S
Since the reaction between S and SO2 can be carried out in the Claus reactor 24, the final S recovery rate is improved.

In the present invention, instead of the dispersion plate, one having a structure that increases the linear velocity within a range that does not inhibit the movement and flow of the desulfurizing agent may be used.

As described above, according to the present invention, the desulfurizing agent that has adsorbed SO□ can be thermally desorbed and regenerated without burning the desulfurizing agent or deteriorating the performance of the regenerated desulfurizing agent. The broken N2,
When combustion exhaust gas is used, the degassed gas is diluted with N2, etc., so the SO3 concentration decreases, and the reactivity in the catalytic reduction tower and Claus reactor decreases. On the other hand, in the present invention, SO
2 is diluted with N20, and this N20 becomes a factor in generating H2S involved in the Claus reaction.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an example of the present invention, and FIG. 2 is a schematic diagram of the thermal desorption regeneration tower used in FIG. 1. DESCRIPTION OF SYMBOLS 1... Boiler, 2... Adsorption tower, 4... Thermal desorption regeneration tower, 7... Heating part, 9... Cooling part, 10... Regeneration desulfurization agent, 12... Steam, 13... Dispersion plate, 1
5... Condenser, 19... Steam generator, 22...
・Catalytic reduction tower, 23゜25...Sulfur condenser, 24...
- Claus reactor. Agent Patent Attorney Akio Takahashi

Claims (1)

[Claims] 1. A desulfurizing agent adsorbing sulfur oxides is moved and flowed down the heating section of a thermal desorption regeneration tower having a heating section and a cooling section at the upper and lower parts, respectively, to thermally desorb sulfur oxides, In the dry flue gas desulfurization method in which the desulfurization agent is then moved down to the cooling section to regenerate the desulfurization agent, steam is supplied to the thermal desorption regeneration tower, and the steam and the desorption gas desorbed from the desulfurization agent are transferred to the heating section. A dry flue gas desulfurization method that is characterized by extracting gas from 2. The dry flue gas desulfurization method according to claim 1, characterized in that steam is introduced into the boundary between the heating section and the cooling section. 3. In claim 1, a mixed gas of steam and desorption gas is introduced into a condenser, where H20/SO
A dry flue gas desulfurization method characterized by adjusting the two ratios and then introducing the flue gas into a catalytic reduction tower.