JPS5837245B2 - sulfur sulfur sulfur - Google Patents

Description

[Detailed Description of the Invention] The present invention enables the smooth recovery of elemental sulfur from a low concentration hydrogen sulfide-containing gas containing ammonia and/or hydrogen cyanide with a hydrogen sulfide content of 60% by volume or less. This paper relates to a new sulfur recovery method.

Conventionally, hydrogen sulfide-containing gas generated from petroleum refineries is called acid gas and contains 90% or more of H2S, and elemental sulfur is recovered by passing this gas through a sulfur recovery device based on the Claus reaction.

In this case, combusting 1/3 of H2S to produce SO2 and reacting with the remaining 2/3 H2S as follows to produce sulfur is well known as the Claus reaction.

Hydrogen sulfide Sulfur dioxide gas Sulfur Claus reaction 2H2S + SO2 →3S water vapor + 2H O ・・・・・・・・・・・・・・・・・・
... ...(1)2 In this case, if the concentration of H2S is high, the heat required for the reaction can be covered by the heat generated when hydrogen sulfide 173 burns, but When the concentration of hydrogen decreases, even if 1/3 of the hydrogen sulfide content is burned, there will be insufficient heat, the temperature will not rise, the Claus reaction will not proceed smoothly, and the sulfur recovery rate will eventually decrease. becomes.

When the H2S content is less than 60% by volume, natural gas, off-gas, or coke oven gas is used as an auxiliary fuel to compensate for this amount of heat, and this is combusted, and this combustion gas is combined with the reaction gas. It is common practice to raise the temperature of the reactant gas.

However, this low concentration hydrogen sulfide gas often contains NH.
3. Nitrogen compounds such as HCN may be mixed in, and if the combustion temperature is low, NH3 will not decompose, but HCN will hydrolyze to become NH3, which will be produced during the process and become SO.
3, crystals of acidic ammonium sulfate (NH4HSO4) or ammonium sulfate ((NH4)2SO4) are formed, which clog the catalyst layer and condenser, reducing the activity of the catalyst and increasing the internal resistance of the device. In the end, this made long-term operation of the device impossible.

In order to overcome this drawback, the temperature of the combustion gas should be raised to 1300-1400℃ in the reactor, so that all NH3 and HCN
It is necessary to decompose it into H20, N2 and CO2.

For this reason, the inventors of the present application modified the structure of the reactor and the operating method as follows.

(1) The reactor was divided into three parts: an auxiliary fuel combustion chamber, a hydrogen sulfide combustion chamber, and a heat exchange chamber.

(2) Part of the auxiliary fuel and hydrogen sulfide is completely combusted in the first chamber with excess air, and in the second chamber, the remaining air is used so that 1/3 of the total hydrogen sulfide added is combusted in the reactor. The remaining hydrogen sulfide was burned off.

(3) In order to reduce the amount of auxiliary fuel and increase the efficiency of the device, the raw material hydrogen sulfide-containing gas and the air necessary to burn 1/3 of the auxiliary fuel and hydrogen sulfide are preheated to approximately 400°C. Add to the reactor.

By doing the above, the temperature inside the reactor can be raised to 1300-1400℃.
It became possible to raise the temperature to 00°C, and almost all of the NH3 and HCN contained became H20, N2 and CO2, so there was no blockage due to ammonium sulfate or acidic ammonium sulfate crystals in the subsequent stage.

The present invention will now be explained in detail based on Figure South.

FIG. 1 is an example of a flow sheet of a Claus-type sulfur recovery facility for recovering sulfur from gas containing sulfur and arsenic, and the first half of the flow sheet shows an example of the apparatus and method according to the present invention.

FIG. 2 is a cross-sectional view of the auxiliary fuel combustion chamber, and FIG. 3 is a view taken along line AA in FIG.

From (1), so-called acid gas containing 60% by volume or more of H2S is introduced, and No. 6 preheater (normally a salt bath is used).

), preheated to approximately 400°C, and passed through conduit 24 to approximately 400°C.
It is led to the hydrogen sulfide combustion chamber 9 of the reactor 1 (partly to the auxiliary fuel combustion chamber).

On the other hand, from (2) auxiliary fuel, such as natural gas, off-gas or coke oven gas, which is easily combustible, is supplied to conduit 1.
9 to the auxiliary fuel combustion chamber 8 of the reactor T.

18 is the air in which part of the auxiliary fuel and acid gas sent by the burner is sent from (3) through the fan 4 and after being preheated to a temperature of about 400°C in the preheater C6, it is sent through the conduit 1T. It is injected and completely combusted, and the combustion generated gas is approximately 1
The temperature reaches a temperature of 200°C to 1300°C and is sent to the next chamber, the hydrogen sulfide combustion chamber 9.

In addition to the air needed to burn the auxiliary fuel, the amount of air sent through the 1γ conduit is
The amount of 1/3 of the hydrogen sulfide sent to the hydrogen combustion chamber 9 and the auxiliary fuel combustion chamber 8 is adjusted so as to be the total amount of air required to convert it into sulfur dioxide gas in the next step.

Hydrogen sulfide Oxygen Sulfur dioxide gas Water vapor H2S+'!
/202→SO2+H20 Therefore, in the combustion of the auxiliary fuel in the auxiliary fuel combustion chamber 8, excessive air is blown in and a special burner (structure in which excess air enters the air mixing chamber 18 in the tangential direction) is used. The auxiliary fuel is completely combusted without generating soot, and the combustion gas reaches a predetermined temperature.

A portion of the preheated combustion air is passed through the conduit 11 to the burner 18.
The air is separated from the primary air and blown from the conduit 11' as primary air.

When the concentration of hydrogen sulfide sent from (1) is very low, it is possible to preheat the auxiliary fuel as well as the acid gas and the required air.

In the hydrogen sulfide combustion chamber 9, the excess oxygen contained in the hot gas coming from the auxiliary fuel combustion chamber 8 is combusted so that 1/3 of the hydrogen sulfide sent to the device becomes sulfur dioxide gas. Adding the amount of heat generated, the overall strength is 13
The temperature rises to 00-1400°C.

According to this, ammonia (
NH3) and hydrogen cyanide scum (HCN) are all H20
, N2 and CO2, and no trouble will occur in subsequent processes.

The boundary between the auxiliary fuel combustion chamber 8 and the hydrogen sulfide combustion chamber 9 may be formed of refractory bricks in the form of a grid, or may have an appropriate passage in the center.

This is provided to completely burn the auxiliary fuel separately.

Next, N containing gas with a ratio of H2S:SO2-2:1
The combustion generated gas that does not contain H3, HCN, etc. is transferred to the next heat exchange chamber 10 (usually called a reactor boiler).

)to go into. Here, boiler feed water is introduced from 26, heat exchanges with the generated gas coming from the hydrogen sulfide combustion chamber 9, and at the same time, part of the Claus reaction takes place.

The heat generated in the heat exchanger is converted into steam 27, and the gas is discharged to the outside through a conduit 21. The sulfur vapor and water vapor generated by the Claus reaction in the reactor T are cooled in the cooler 12, and then converted into molten sulfur in the conduit 20. It is guided to the storage tank 13.

The lower unreacted gas passes through the conduit 21 to the line burner 14.
(After adjusting the temperature to an appropriate temperature for the Claus reaction (approximately 200°C) using an auxiliary heating device, the reactor is led to the front stage 11' of the reactor 11.

The shelf of the reactor 11 is filled with an alumina-based catalyst, and here the harmful gas of H2S:SO2-221 is 20
The Claus reaction of formula (1) is carried out at a temperature of 0 to 250°C, and sulfur vapor and water vapor are generated.

The Claus reaction is 90% in the reactor end and first stage reactor 11'.
is completed.

The gas is cooled to about 140° C. in the first cooler 12' to condense the sulfur, and the molten sulfur is stored in the molten sulfur storage tank 13 via the conduit 23'.

The unreacted gas is again reheated to an appropriate temperature in the line heater 14' via the conduit 22, and guided to the second stage reactor 11'', where the reaction is carried out at a total reaction rate of 95%. 12'', the produced sulfur is sent to a molten sulfur storage tank 13, and the unreacted gas is sent via conduit 16 to an incinerator or tail gas treatment facility (both not shown).

Furthermore, if the raw gas in (1) contains NH3 or HCN and the temperature in the reactor T remains at around 1,200°C, as mentioned earlier, crystals of acidic ammonium sulfate and ammonium sulfate will form. may be deposited on the catalyst layer of the reactor 11 or the coolers 12, 12.
Crystals precipitate within the reactor, increasing the resistance inside the reactor and reducing the purity of the sulfur produced.

The present invention overcomes the above-mentioned difficulties, and the actual situation thereof will now be illustrated with examples.

Example 0 Equipment used 8 Asahi/Japan Claus type sulfur recovery equipment However, in Example A, the reactor of the present invention was When divided into rooms.

Example B uses heat exchange between the reactor and the combustion chamber as before. If the room is divided into two rooms.

Acid gas composition O Acid gas processing amount 7 3 4 Nrn'/h
r○ Coke oven gas was used as the auxiliary fuel since the acid gas is generated from refining coke oven gas.

Coke oven gas usage: 116Nmhr, acid gas and air required (1155Nrrr'/hr)
The following is an example comparing the case where the sample was preheated to 350°C and the case where it was not preheated.

From the above results, it was found that when the reactor (~) is divided into three chambers and the acid gas and the required air are preheated to about 350°C, the following effects can be obtained.

(1) Even if the acid gas contains NH3 or HCN gas, there is no precipitation of acidic ammonium sulfate or ammonium sulfate crystals during the process, and long-term continuous operation is possible.

(2) The conversion rate of hydrogen sulfide to sulfur by the Claus reaction has increased from 94% to 95%.

(Even with a 1% increase, it will take a considerable amount of time to process the tail gas, etc.) In order to bring the furnace temperature in (3) CB) to the same temperature as in 09, it is necessary to further add auxiliary fuel and ammonium sulfate air, and the momentum equipment is , the amount becomes huge and the reaction components are diluted. ．． Conversion rate decreases (due to low active ingredient partial pressure).

According to the method of the present invention, there is no need to worry about this at all.

(4) There is no formation of abnormal crystals, etc., and the auxiliary fuel is completely combusted, so there is no generation of soot, etc., so the product sulfur has a pure yellow-white color and its purity is 99.9% or more.

As mentioned above, for example, the acid gas generated from the desulfurization of heavy oil (which generally contains NH3 and HCN) and the acid gas generated from the desulfurization of coke oven gas contain a large amount of CO2. Since it contains a small amount of HCN, the concentration of H2S is rarely 0).

The method of the present invention provides a method for recovering sulfur from low-concentration acid gas, which can be operated smoothly and continuously over a long period of time.The method of the present invention is extremely effective from the standpoint of preventing air pollution and recovering useful resources. It is believed that there is.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing one example of the method of the present invention. FIG. 2 is a longitudinal sectional view of the auxiliary fuel combustion chamber, and FIG. 3 is a view taken along line A in FIG. 7 is a reactor, 8 is an auxiliary fuel combustion chamber, 6 is a preheater, 9 is a hydrogen sulfide combustion chamber, 10 is a heat exchange chamber, 12, 12', 12''
is a cooler, 11 is a reactor, 11' and 11'' are first and second stage reactors, respectively, 13 is a molten sulfur storage tank, 14, 14
' is a line burner.

Claims (1)

[Claims] 1. When recovering elemental sulfur from a gas containing ammonia and/or hydrogen cyanide gas as impurities and containing a low concentration of hydrogen sulfide, in which hydrogen sulfide is less than 60% by volume, excess air flows through the reactor T into the air mixing chamber 8'. Burner 1 entering the direction
8, a hydrogen sulfide combustion chamber 9, and a heat exchange chamber 10, and the hydrogen sulfide-containing raw material gas and the required air are preheated and then added to the reactor T. A method for recovering sulfur from gas containing low concentration hydrogen sulfide.