JPS6034411B2 - Activated carbon regeneration and sulfur recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering sulfur by regenerating activated carbon used for flue gas desulfurization, and at the same time decondensing and reducing adsorbed sulfur compounds. It is an object of the present invention to provide a method in which sulfur can be recovered at the same time in one apparatus during the regeneration of used activated carbon.

To date, many wet and dry methods have been reported for removing sulfur oxides from exhaust gas.The wet method involves absorbing and removing sulfur oxides with an aqueous solution or suspension of calcium hydroxide or calcium carbonate. A typical method is to recover it as gypsum, and a typical dry method is an adsorption method using activated carbon.

Since the wet method is a neutralization method, it has good desulfurization efficiency, but because it uses a large amount of water, there are problems in wastewater treatment, equipment corrosion, and scale formation.

Also, as the temperature of the treated exhaust gas decreases, the treated gas (smoke)
In order to improve the diffusion of water vapor and prevent white smoke caused by water vapor, it is necessary to raise the temperature of the processing gas. Furthermore, not only is the quality of the by-product stone pipes poor, which poses problems in their treatment, but also the problem is that they require a large amount of water, which has recently become difficult to secure. The activated carbon adsorption method, which is a dry method, is a good method, but the adsorption rate of sulfur dioxide is slow, so the adsorption equipment is large, and activated carbon is generally expensive.
There are problems with activated carbon regeneration equipment and treatment of released components.

However, a method of improving the sulfur dioxide adsorption capacity of activated carbon by injecting hair ammonia into the exhaust gas and relatively inexpensive activated carbon are emerging.Recently, the activated carbon adsorption method, which does not have the problems of the wet method described above, is being reconsidered. . However, there is still much room for improvement in the activated carbon adsorption method, especially in the method of regenerating activated carbon. There are two methods of regenerating activated carbon: a water-washing method and a heating method, but the water-washing method yields only dilute sulfuric acid as a regenerating material. In the heating method, it is possible to recover high-concentration S02 gas using a heat regeneration device, but if this is to be recovered as sulfuric acid or sulfur, a separate production device is required. As a method for recovering sulfur from high-concentration S02 gas, many reduction methods using hydrocarbons such as methane, natural gas, gaseous reducing agents such as carbon monoxide or hydrogen, or carbon sources such as coal and coke have been reported. There is. On the other hand, unlike this activated carbon regeneration method, there is a method in which activated carbon is regenerated by using hydrogen sulfide during regeneration to reduce sulfuric acid adsorbed on activated carbon to sulfur, but this method also requires hydrogen sulfide production equipment. Moreover, it is difficult to operate. The present invention is completely different from these known methods in that sulfuric acid or ammonium sulfate salts adsorbed on activated carbon are reduced to sulfur in a moving bed regenerator in the coexistence of carbonaceous materials such as coal and coke. Moreover, the present invention provides a method for regenerating activated carbon.

In other words, the present invention provides the following method: ``Activated carbon used for desulfurization of exhaust gas is sent to a moving bed type regenerator together with other carbonaceous materials, and heated gas that does not contain oxygen is sent to the top of the moving bed to cool the inside of the regenerator. The maximum temperature is maintained at 700 oo or higher to decompose and remove sulfuric acid or ammonium sulfate adsorbed on activated carbon and reduce it to sulfur. Regenerated activated carbon is obtained from the bottom of the regenerator, and a gas containing free sulfur generated in the regenerator is mixed. ``A method for regenerating activated carbon and recovering sulfur, which is characterized by extracting sulfur from a moving lower part and separating sulfur from it''.

According to the present invention, it is possible to regenerate activated carbon and recover sulfur using only a single device, and it is possible to easily regenerate activated carbon and recover sulfur without requiring a desorption S02 reprocessing device or a reducing gas production device. Collection can be done at the same time. The present invention will be explained in more detail below. When sulfur oxides in exhaust gas are adsorbed and removed by activated carbon, the sulfur oxides are adsorbed in the activated carbon as sulfuric acid according to the following formula m.

Lee 02 10 2 2 LO → 2nd 2S04 → ・
...[1] Also, when sulfur oxides are adsorbed and removed with activated carbon after ammonia is injected into the exhaust gas, the sulfur oxides are (N ratio)
It is adsorbed as ammonium salts such as 2S04 and Nratio HS04.

Activated carbon that has adsorbed these compounds is used in a regenerator to
When heated to 0q0, the adsorbate is decomposed by a reaction opposite to that during adsorption, S02 gas is released, and the activated carbon is regenerated. This decomposition reaction is shown by the following formula. 2nd 2S040, C→Ru02
10C02 12th 20...{2) Shuhi HS04
10C → 2NH3 10$02 10C02 12th 20...{3
}2 (N ratio) 2S04 → 4NH3 ten $02 ten C02 ten 2
Day 20...■Fun ratio HS041 N ratio 10$020N20 mother L○...■3(N is)2S04→4NH314NH
30$ 20N 20 days 20 days... (6) In the conventional activated carbon regeneration method, the activated carbon and the decomposed gas are separated and the activated carbon regeneration is completed, but in the present invention, the activated carbon and the decomposed gas are separated. While maintaining mixed contact with the gas, the temperature is further increased to 700 q0 or more.

This heating causes the next reduction reaction of the S02 gas.
$0212C → S212C02 ・
The decomposition reaction of the formula ■~{6} is an endothermic reaction, and the decomposition reaction of the formula (
7} is a weak exothermic reaction, but both the decomposition reaction and the reduction reaction involve consumption of carbon.

The true advantage of the present invention is that it has established a heating and temperature raising means that allows two contradictory reactions to occur in the same device, and that it has established a heating and temperature raising means that allows two contradictory reactions to occur within the same device, and that it has a separate carbon source that is fed to the regenerator together with the activated carbon instead of relying on the activated carbon itself as a carbon source to be consumed. The present invention succeeded in achieving its intended purpose for the first time by using it as a carbon source. In the present invention, the regenerator has a charging port for activated carbon and carbon material at the top, a discharge port for the recycled activated carbon at the bottom, a distributor for supplying inert gas at the top of the moving bed forming part in the vessel, and a sulfur at the bottom. Using a device having a distributor for discharging the contained cracked gas, the gas and activated carbon for regeneration are made to flow together from above to below.

If an inert gas heated to 700 oo or more is used as the inert gas to be supplied, the charged activated carbon and carbon material will rise in temperature as they descend above the gas distributor and reach the decomposition temperature. The decomposition reaction shown by Tsukuda occurs, and the reduction reaction {7) occurs sequentially between the gas supply distributor and the gas release distributor, and the entire reaction is completed during the descent. will be played. Since the action of the present invention is as described above, the carbon tribute used in combination with activated carbon for regeneration is more easily reactive than activated carbon, but is preferable, and suitable examples include coal pulverized to a size of 1 to 3 or more grains, and coke. etc. Next, modes for industrially implementing the present invention will be explained with reference to the drawings. Activated carbon and carbon particles to be regenerated are introduced into the regenerator 3 through the respective feed lines 1 and 2, and inert gas heated to 700 qC or more is sent through the pipe 5 from the distributor 4 at the top of the regenerator. is introduced, the activated carbon and carbonaceous material gradually descend, and the inert gas flows downwardly between the activated carbon and carbonaceous mixture together with the gas decomposed above the distributor 4.

Therefore, in the upper part of the distributor 4, the adsorbate is completely decomposed in the temperature range of 300 to 600 oo due to heat transfer from the injected thermal inert gas, and in the lower part of the distributor 4, a sequential reduction reaction (carbon The system is adjusted so that the entire reaction is completed when the oxidation reaction (oxidation reaction) occurs and reaches the lower distribution point for extracting the produced gas. All of the decomposed gas in the regenerator 3 is drawn out from the distributor 6 at the bottom, passes through a dust collector 7 such as a cyclone, and reaches the sulfur condenser 8, where the sulfur is liquefied and pumped out from the pipe 9. , some unreacted S02,
Sulfur and by-reaction products of slag recovery, glue ○, CO
Till gas containing S, CS2, etc. is sent to a combustion furnace (not shown) through a pipe 101, and then returned to the S02 gas adsorption device. On the other hand, the regenerated activated carbon is discharged from the bottom of the regenerator together with ash and unreacted carbon and reaches the vibrating screen 11. Afterwards, they are collected and disposed of. The inert gas that does not contain oxygen used in the present invention refers to an inert gas that does not contain oxygen in an amount that actually contributes to oxidation, and includes combustion exhaust gas, carbon dioxide, nitrogen, etc. . The size of the activated carbon used for regeneration is approximately 4 to 10 willows. Next, examples will be shown. Example 1 Anthracite with a grain size of 1 grain was added to activated carbon with a grain size of 4 grains (sulfur oxide adsorption amount is 135 9 / night activated carbon in terms of S02) used for exhaust gas treatment at a weight ratio of 0 to 1 activated carbon. .3 The condensed material was continuously supplied at a rate of 600 m/hour to a moving bed regenerator kept warm in an electric furnace with an inner diameter of 102 and an effective packed bed height of 1.84 m.

In addition, high-temperature heated nitrogen gas is supplied from the top of the reactor,
The maximum temperature inside the regenerator was maintained at 780 oo. Analysis of the gas from the gas outlet at the bottom of the regenerator revealed that the recovery rate as sulfur was 80%. In addition, S0 as a sulfur compound
2, day 2S, COS, and CS2 of the feature were generated. or,
The dust and activated carbon pulled out from the bottom of the reactor were separated using a ring on the 1.68 side, and an activated carbon recovery rate of 97.2% was obtained. Comparative Example Using only the same used activated carbon as in Example 1, 300 to 600 carbon per hour was continuously supplied to the regenerator.
It was carried out under the same conditions.

When the gas from the gas outlet at the bottom of the reactor was analyzed, the recovery rate as sulfur was 70-71%. Further, the dust and activated carbon pulled out from the bottom of the reactor were separated on the 1.68 side, and the activated carbon recovered was 95 to 96%.
Example 2 Activated carbon with a particle size of 4 used for exhaust gas treatment (
The sulfide adsorption amount is 119 in terms of S02, activated carbon, and the ammonia adsorption amount is 20 in terms of activated carbon), and a mixture of Luoqing coal with a particle size of 1 rib at a weight ratio of 0.3 to 1 part of activated carbon. As in Example 1, 600 liters per hour were continuously supplied to the regenerator.

In addition, high-temperature heated nitrogen gas is supplied from the top of the reactor,
The maximum temperature inside the regenerator was maintained at 770 oo. When the gas from the gas outlet at the bottom of the reactor was analyzed, the recovery rate as sulfur was 81%. S as other sulfur compounds
02, day 2S, COS and feature CS2 were generated. In addition, the dust and activated carbon pulled out from the bottom of the reactor were reduced to 1.68
The activated carbon was divided into knots using willow knots, and an activated carbon recovery rate of 97.8% was obtained. Example 3 The same activated carbon as used in Example was mixed with coke having a grain size of 1 willow in a weight ratio of 1 to 0. The resulting mixture was continuously supplied to the regenerator in the same manner as in Example 1 at a rate of 600 hours per hour.

In addition, high-temperature heated nitrogen gas is supplied from the top of the reactor,
The maximum temperature inside the regenerator was maintained at 800°C. When the gas from the gas outlet at the bottom of the regenerator was analyzed, the recovery rate as sulfur was 81%. S02 as other sulfur compounds
, day 2S, COS, and CS2 of the features were generated. Further, the dust and activated carbon pulled out from the bottom of the reactor were divided into stripes at 1.68 ribs, and an activated carbon recovery rate of 97% was obtained.

[Brief explanation of the drawing]

The figure is an explanatory diagram diagrammatically showing an embodiment of the present invention. 1... Regeneration activated carbon feed path, 2... Carbonaceous material feed path, 3
... Regenerator, 4... Upper distributor, 5... Inert gas feed pipe, 6... Lower distributor,
7... Dust collector, 8... Sulfur condenser, 9... Tube, 10... Tube, 11... Vibration screen, 12...
- Discharge path, 13... Discharge path.

Claims (1)

[Claims] 1 Activated carbon used for desulfurization of exhaust gas is sent to a moving bed type regenerator together with other carbon substances, and heated gas that does not contain oxygen is sent to the top of the moving bed to raise the maximum temperature inside the regenerator to 700℃.
The sulfuric acid or ammonium sulfate, etc. adsorbed on the activated carbon are decomposed and desorbed by keeping the temperature above ℃ to reduce it to sulfur. Regenerated activated carbon is obtained from the bottom of the regenerator, and the gas mixture containing free sulfur generated in the regenerator is moved. A method for regenerating activated carbon and recovering sulfur, which is characterized by extracting sulfur from the lower part and separating sulfur from it.