JPS6034414B2 - Regeneration method of carbonaceous adsorbent for desulfurization - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION As a method for dry desulfurization of exhaust gas from a fixed source, a method has been put into practical use in which a carbonaceous adsorbent, typically activated carbon, is brought into contact with activated carbon in the form of a moving bed.

In this dry desulfurization method, the carbonaceous adsorbent is gradually inactivated by contact with activated carbon, so it is customary to regenerate it at an appropriate time to restore adsorption capacity and use it again for contact with activated carbon. For regeneration in this case, a method is adopted in which the inactivated carbonaceous adsorbent is heated to a temperature of 300 to 650 qC in an inert gas atmosphere. However, this thermal regeneration method uses the carbonaceous adsorbent itself as a reducing agent to remove the sulfuric acid adsorbed on the inactivated carbonaceous adsorbent.
Since the carbonaceous adsorbent is decomposed and desorbed as shown in 2C→S0211/2C02Toka20, not only is the carbonaceous adsorbent inevitably consumed during regeneration, but also the S○ of the carbonaceous adsorbent is There is a problem that the k adsorption capacity decreases.

The present invention aims to solve this problem, and by bringing an inert carbonaceous adsorbent into contact with ammonia gas in advance to convert the sulfuric acid adsorbed onto the adsorbent into ammonium salt, an inert gas atmosphere is created. The aim is to suppress consumption of the carbonaceous adsorbent during heating and regeneration in the chamber, and to improve the S○k adsorption capacity of the regenerated carbonaceous adsorbent.

Therefore, the method for regenerating carbonaceous adsorbent for desulfurization according to the present invention is as follows:
Prior to heating and regenerating the inactivated carbonaceous adsorbent used for dry flue gas desulfurization in an inert gas atmosphere, at least the sulfuric acid adsorbed on the inactivated carbonaceous adsorbent is removed by contacting it with ammonia gas in advance. It is characterized by converting a portion of the adsorbent into ammonium salt, and then regenerating the adsorbent by heating in an inert gas atmosphere. According to the method of the present invention, the carbonaceous adsorbent that has been inactivated by contact with exhaust gas is first heated with ammonia gas at 60 to 1800C, preferably 90 to 1500C.
Contact is made at a temperature of 0.

Through this contact, ammonia is adsorbed on the inactivated carbonaceous adsorbent, and at least a portion of the sulfuric acid already adsorbed on the adsorbent is converted into an ammonium salt as shown in the following formula. day 2s
040N ratio → NH4HS04 ・・・・・・(
1) Sun 2S04 10 ga Sun 31 (NH4) 2S04 ・
(b) The amount of ammonia adsorbed on the inactivated carbonaceous adsorbent may be in the range of 0.1 to 2 moles per mole of sulfuric acid adsorbed on the adsorbent.

If the ammonia adsorption amount is less than this, it is not possible to suppress consumption of the carbonaceous adsorbent during thermal regeneration, and it is also not possible to improve the S○k adsorption capacity. On the other hand, if the amount of ammonia adsorption is too large, a large amount of ammonia will be mixed into the S02 gas recovered during subsequent thermal regeneration, resulting in a problem. The inactivated carbonaceous adsorbent, in which some or all of the sulfuric acid has been converted into ammonium salt by contact with ammonia gas, is then heated in an inert gas atmosphere for 350 min in a conventional manner.
It is heated to a temperature of ~600 oo and regenerated. The details of the chemical reaction that occurs during this heating regeneration are not necessarily clear, but the main reaction is presumed to be expressed by the following formula. Shuu Melon HS041 NH30$020 Mother L
03(NA)2S04-4NH30$020N2
Jugumi 202/Suhichi 30 (0) *→ 1/Shu 20 ratio ○ *Represents surface oxygen on the adsorbent.

In any case, most of the ammonia adsorbed on the inert carbonaceous adsorbent in the form of ammonium salts such as NH4HS04 and (NH4)2S04 is decomposed into nitrogen during thermal regeneration.
The decomposition rate depends on the amount of ammonia adsorbed and the heating temperature during regeneration, but is usually 80 to 99%.

However, if the decomposition of ammonia into nitrogen is insufficient, ammonia will be mixed into the S02 gas desorbed from the inactivated carbonaceous adsorbent. Therefore, when attempting to produce sulfuric acid or sulfur from this desorbed S02 gas, there is a possibility that ammonium salts may clog the production equipment, cause corrosion, or reduce the purity of the product. Therefore, if ammonia is expected to be mixed in, nitrogen oxides are additionally injected into the desorbed 602 gas, and this is brought into contact with the regenerated carbonaceous adsorbent to convert the remaining ammonia into nitrogen as shown in the following formula. Decomposition is preferred. 4NH3 Jushu 01 Hada Jugumi 20 Isobi 3 Toshu 02-7N2 Ju-12 0 In the above decomposition reaction, the carbonaceous adsorbent acts as a catalyst and promotes the decomposition reaction.

What is noteworthy here is that the carbonaceous adsorbent is not inactivated despite the coexistence of a high concentration of S02. There is no need to heat the agent again, and satisfactory results can be obtained by injecting nitrogen oxides into the desorbed S02 gas and contacting the regenerated carbonaceous adsorbent.The amount of nitrogen oxides added is 1. 0.75 to 1 mole per mole,
Preferably, a range of 1 to 5 moles is allowed. Furthermore, if oxidizing agents such as oxygen are mixed with nitrogen oxides, the carbonaceous adsorbent will be consumed, so if oxidizing agents are mixed, it is desirable to remove this in advance.The present invention The advantage of this regeneration method is that the carbonaceous adsorbent is less consumed during heating regeneration in an inert gas atmosphere, and the S○× adsorption capacity of the regenerated carbonaceous adsorbent is improved. can be specifically explained with reference to FIGS. 1 and 2.

In other words, in Figure 1, activated carbon activated by adsorbing sulfuric acid (110 9/g activated carbon as adsorption amount S02) was used for dry desulfurization of boiler exhaust gas, so 150 oo of activated carbon containing 3% ammonia gas was used. This figure shows the amount of activated carbon consumed when a predetermined amount of ammonia is adsorbed by contact with nitrogen gas and then heated and regenerated in a nitrogen stream of 38,000 ml.As shown in the figure, after adsorbing ammonia, inactivated activated carbon If activated carbon is regenerated by heating, consumption of activated carbon can be prevented, and the effect of preventing consumption will also increase with respect to an increase in the amount of ammonia adsorption.

Figure 2 shows the fact that when inactivated activated carbon is regenerated by the method of the present invention, the amount of S02 adsorbed by the activated carbon increases each time it is regenerated. In the reactor, 1000 ppm S02 and 10% H20
After passing air containing S02 at 120°C for 5 hours to adsorb S02 as sulfuric acid on activated carbon, nitrogen gas at 150°C containing 3% ammonia was passed for 1 hour, and then inactivated activated carbon adsorbed ammonia. When the activated carbon is heated and regenerated in a nitrogen stream of 38,000 yen, the amount of S02 adsorbed on the activated carbon is measured from the S02 desorbed at this time, and the regenerated activated carbon is inactivated and regenerated in the same manner as above. These are the experimental results.

Next, the method of the present invention will be explained with reference to FIGS. 3 and 4, which show a side sectional view of an example of a reproducing apparatus suitable for implementing the reproducing method of the present invention.

In Figures 3 and 4, the carbonaceous adsorbent (hereinafter simply referred to as adsorbent) that has been inactivated and used for dry desulfurization is supplied to the moving bed regenerator 1 from the upper valve V, and is temporarily stored. Stored in area 2. The deactivated adsorbent then flows down into the mixing zone 3 where it comes into contact with the ammonia-containing inert gas supplied from line 4. Through this contact, part or all of the sulfuric acid adsorbed on the inactivated adsorbent is converted into ammonium salts such as acidic ammonium sulfate and ammonium sulfate. Thereafter, the inactivated adsorbent descends through a plurality of heat transfer tubes 6 arranged substantially vertically within the heating region 5. At this time, heated gas is supplied to the outside of the heat exchanger tube in the heating region 5 from the inlet at the lower part of the region to the outlet at the upper part via the line 7, so that the inactivated adsorbent in the heat exchanger tube 6 is heated by the heated gas. heated to a regeneration temperature of over 30,000°C by indirect heat exchange with Therefore, while the inactivated adsorbent passes through the heat transfer tube 6, S02, N2, etc. are desorbed from the inactivated adsorbent.
These desorbed gases, together with the adsorbent, descend into the separation zone 8 in the regenerator of FIG. As mentioned above, most of the ammonia adsorbed in the form of ammonium salt on inactivated activated carbon is decomposed into nitrogen by being heated to the regeneration temperature in the heat exchanger tube, but if this decomposition is insufficient, In this case, ammonia is mixed into the gas desorbed from the inactivated adsorbent.

Therefore, if contamination with ammonia is expected,
As shown in the figure, the adsorbent that has descended through the heat exchanger tube 6 is supplied to the NH3 decomposition region 9, and the nitrogen oxides and ammonia sent from the line 10 are decomposed into nitrogen, and then the adsorbent is descended to the separation region 8. In the separation region 8, the gas desorbed from the inactivated adsorbent is discharged to the line 11 together with the inactivated gas, and the regenerated adsorbent is taken out of the regenerator from the lower valve V2.

In addition, the code|symbol 12 shows a rectifier. In addition, in the examples shown in FIGS. 3 and 4, the inactivated adsorbent is flowed inside the heat transfer tube 6 and the heated gas is flowed outside the tube, but this is reversed and the heated gas is flowed inside the tube and the heated gas is flowed outside the tube. There is no problem in flowing an inactivated adsorbent into the tank. The regeneration method of the present invention is applicable to all inactivated carbonaceous adsorbents used in dry flue gas desulfurization, and such carbonaceous adsorbents include activated carbon, coke, etc., as well as vanadium pentoxide, etc. Some metal oxides are supported. Furthermore, the ammonia gas used in the present invention can be used alone or in the form of a mixture with an inert gas, as shown in FIGS. 3 and 4. Furthermore, nitrogen oxides to be injected into the desorption gas are preferably obtained by catalytic air oxidation of ammonia or decomposition of nitrates or nitrites, and when injected into the desorption gas, they can be diluted with an inert gas. shall be. Example Activated carbon used for dry desulfurization of boiler exhaust gas and inactivated by adsorbing sulfuric acid (adsorption amount S02: 9/g of 110)
The activated carbon) was contacted with nitrogen gas at 150oC containing 5% ammonia gas, and the molar ratio of adsorbed NH3/adsorbed S02 was set to 0.6.

Thereafter, this activated carbon was heated in a nitrogen stream to obtain regenerated activated carbon. Also, S02 19 recovered during this heating regeneration
．． 6%, C024.1%, 2044.7%, NH30
．． 2% NO was injected into the desorption gas containing 6% N, 31% N2, and the reactor containing 8.17% of the above regenerated activated carbon was heated to a temperature of 30%.
000 at a flow rate of 1/hour, the NH3 concentration at the reactor outlet was 0.001%.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the molar ratio of adsorbed NH3/adsorbed S02 and the amount of consumed activated carbon. FIG. 2 is a graph showing the relationship between the number of times activated carbon is regenerated and the amount of S02 adsorbed. 3 and 4 are side sectional views of a regenerator through which the method of the present invention may be carried out. 1...
・Regenerator, 2...Storage area, 3...Mixing area, 4...Ammonia-containing inert gas line,
5... Heating area, 6... Heat transfer support, 7... Heating gas line, 8... Separation area, 9...
・NH3 decomposition area, 10... Nitrogen oxide introduction line, 11... Desorption gas line, 12...
...Fluid regulation. Figure l Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. In a method of heating and regenerating a carbonaceous adsorbent that has been inactivated by use in a dry desulfurization method in an inert gas atmosphere, prior to heating and regenerating the inactivated adsorbent, inactivation adsorption is performed. Desulfurization characterized by contacting the agent with ammonia gas in advance to convert at least a portion of the sulfuric acid adsorbed on the inert adsorbent into ammonium salt, and then heating the adsorbent in an inert gas atmosphere. Regeneration method of carbonaceous adsorbent for use. 2. In the upstream region of the moving bed regenerator, the mixed gas of ammonia gas and inert gas is brought into contact with the inactivated adsorbent, and in the middle region of the regenerator, the inactivated adsorbent is subjected to indirect heat exchange with the heated gas. 2. The regeneration method according to claim 1, wherein the deactivated adsorbent is heated to a regeneration temperature in the downstream region of the regenerator, and the desorbed gas from the regenerated adsorbent is separated from the regenerated adsorbent. 3 In the downstream region of the moving bed regenerator, before separating the desorbed gas from the inactivated adsorbent from the regenerated adsorbent, nitrogen oxides are injected into the desorbed gas to bring it into contact with the regenerated adsorbent, and the desorbed gas is The regeneration method according to claim 2, characterized in that ammonia in the gas is decomposed into nitrogen.