JPH10185159A - Combustion method and apparatus for simultaneous decomposition of ammonia and complete combustion of hydrogen sulfide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion method and an apparatus for completely burning hydrogen sulfide in the same furnace and decomposing ammonia into nitrogen and water without simultaneously converting ammonia to NOx as much as possible. A reduction by introducing primary air of NH ₃ auxiliary fuel gas containing gas and the NH ₃ containing gas and the auxiliary fuel gas less air volume than the amount of air to complete combustion from the nozzle of the hearth of the combustion furnace of because when the combustion in the primary combustion zone atmosphere NH ₃ is a shortage of oxygen, most not the NOx is decomposed into N ₂ and water, a portion remains remains NH _3. In addition, the auxiliary fuel gas partially remains as unburned gas in the form of CO or H ₂ due to partial combustion. When the secondary air and the H ₂ S-containing gas are blown into the furnace downstream of the primary combustion zone to completely burn unburned components and H ₂ S in the primary combustion zone,
The unburned gas becomes CO ₂ and water vapor, and NH ₃ is partially NOx
The other is decomposed into N ₂ and H ₂ O, and the outlet 2 of the combustion furnace 5
Most of the gas derived from NH ₃ and H ₂ S discharged from 3 is water vapor, SO ₂ and N ₂ .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a combustion method and a combustion apparatus for simultaneously decomposing ammonia and completely oxidizing hydrogen sulfide.

[0002]

2. Description of the Related Art In a process such as petroleum refining, hydrogen sulfide and ammonia are obtained as by-products. It is necessary to fix or detoxify the obtained hydrogen sulfide and ammonia.
Conventionally, a method generally used as a method for immobilizing or detoxifying hydrogen sulfide and ammonia generated in the above-described oil refining process is to introduce hydrogen sulfide into a Claus furnace and partially burn it, and fix it to elemental sulfur. This is the Claus-Scott method, in which elemental sulfur is recovered, and ammonia is blown into the same Claus furnace and burned in a reducing atmosphere to decompose into nitrogen and water to render it harmless.

[0003]

However, there are the following problems in the fixing or detoxification treatment of hydrogen sulfide and ammonia using the Claus furnace. The market for using elemental sulfur is saturated, and it is unlikely that demand for sulfur will increase from the current level. If the elemental sulfur cannot be used effectively, it must be disposed of. However, in addition to the fact that elemental sulfur is designated as a dangerous substance by the Fire Service Law and oxidized when it is oxidized, it is necessary to adopt a strict and permanent management system, such as putting it in a drum and storing it in a building. If the effective detoxification or immobilization treatment of the elemental sulfur cannot be performed, the operation of a plant such as petroleum refining will be hindered.

[0004] Therefore, as an alternative to the Claus-Scott method, sulfur-hydrogen produced in a process such as petroleum refining is completely burned to form sulfur dioxide, and the obtained sulfur dioxide is reacted with a limestone slurry and recovered as gypsum. A method is conceivable.

[0005] However, in the method of recovering sulfur content as gypsum, when combusted in the same furnace, ammonia is also completely combusted when sulfur-hydrogen is completely combusted, so that ammonia is not decomposed into nitrogen and water. A significant portion of the ammonia is converted to NOx. For example, in gas turbine combustion, it has been reported that when a gas containing ammonia is burned, about 30% of the ammonia is converted to NOx.

Therefore, it is necessary to install high-performance flue gas denitration equipment in the exhaust gas flow path downstream of the combustion furnace from the viewpoint of pollution prevention, and this equipment cost and running cost are required. Operation becomes complicated.

It is an object of the present invention to provide a combustion method and apparatus for completely burning hydrogen sulfide in the same furnace while decomposing ammonia into nitrogen and water without converting ammonia to NOx as much as possible. Another object of the present invention is to provide a combustion method and apparatus which simultaneously decompose hydrogen sulfide and ammonia and decompose into harmless nitrogen and water other than sulfur oxides.

[0008]

The above object of the present invention is attained by the following constitution. That is, the primary combustion of the reducing atmosphere is performed by introducing the auxiliary fuel gas into the ammonia-containing gas and the primary air having a smaller air volume than the air for completely burning the ammonia-containing gas and the auxiliary fuel gas from the nozzle at the furnace end of the combustion furnace. Combustion in the zone, secondary air and hydrogen sulfide-containing gas are blown into the furnace downstream of the primary combustion zone, and the unburned portion and the hydrogen sulfide-containing gas in the primary combustion zone are completely burned. This is a combustion method that performs complete combustion simultaneously.

In the above combustion method, the secondary air and the hydrogen sulfide-containing gas are blown into the combustion furnace at a position where oxygen of the primary air reacts and is almost completely digested or at a downstream side thereof. Hydrogen sulfide-containing gas is blown into the downstream part of the blowing position of hydrogen to convert hydrogen sulfide to sulfur oxides and to react a small amount of nitrogen oxides generated by unburned ammonia and secondary air with hydrogen sulfide. Nitrogen oxides can be converted to nitrogen.

The present invention also includes a combustion apparatus having the following combustion furnace. That is, a nozzle for introducing the ammonia-containing gas into the auxiliary fuel gas and a primary air having an air amount smaller than the amount of air for completely burning the ammonia-containing gas and the auxiliary fuel gas is provided at the furnace end of the combustion furnace, and reduced in the combustion furnace. Forming a primary combustion zone of an oxidizing atmosphere, providing a nozzle for blowing secondary air and a hydrogen sulfide-containing gas in a furnace downstream of the primary combustion zone, and forming a secondary combustion zone of an oxidizing atmosphere in the furnace, This is an apparatus having a combustion furnace provided with an exhaust gas outlet downstream of the secondary combustion zone to simultaneously perform decomposition of ammonia and complete combustion of hydrogen sulfide.

Further, any two or three of the ammonia-containing gas, auxiliary fuel gas and primary air introduced from the nozzle at the furnace end of the combustion furnace can be premixed and introduced into the furnace. Alternatively, they may be introduced into the furnace and diffused without premixing. In either case, it is necessary to form a primary combustion zone in a reducing atmosphere.

The primary air amount is an air ratio of 1 to the theoretical air amount for completely burning the ammonia-containing gas and the auxiliary fuel gas.
It is necessary to ensure that the flow rate is as follows and that the flow rate of the primary combustion zone is stable. The air ratio is 1
If it exceeds 300, a reducing combustion zone cannot be formed, and ammonia is easily converted to NOx.

[0013] The secondary air amount is 1 or more as an air ratio to the theoretical air amount at which complete combustion of the unburned gas and the hydrogen sulfide-containing gas in the primary combustion zone is achieved. If the air ratio is less than 1, part of the hydrogen sulfide remains without being oxidized.

Further, in the combustion furnace of the present invention, as described above, the hydrogen sulfide-containing gas is provided at the downstream portion of the secondary air blowing nozzle by providing a nozzle for blowing hydrogen sulfide, thereby converting hydrogen sulfide to sulfur oxide. And a small amount of nitrogen oxides generated by the remaining unburned ammonia and secondary air can be reacted with hydrogen sulfide to convert the nitrogen oxides into nitrogen. Further, by directing the gas blowing direction of the secondary air blowing nozzle and / or the hydrogen sulfide-containing gas blowing nozzle to the upstream part of the combustion furnace, the gas discharged from each nozzle is sufficiently diffused into the furnace. Can be.

In the primary combustion zone (partial combustion zone) of the reducing atmosphere in the combustion furnace, the ammonia-containing gas does not turn into nitrogen oxide due to lack of oxygen, and most of the gas is decomposed into nitrogen and water, and part of the gas is decomposed into nitrogen and water. It remains as ammonia.

As the auxiliary fuel gas, any fuel may be used as long as it does not hinder the combustion of the ammonia-containing gas. A coke oven gas containing carbon monoxide and hydrogen as main components can be used. The fuel gas partially remains as unburned gas in the form of carbon monoxide or hydrogen due to partial combustion. Therefore, the partially combusted gas contains a mixture of nitrogen, carbon dioxide, and water vapor partially containing unburned gas and ammonia.

In addition, the inside of the furnace on the downstream side where the secondary air is blown is in a combustion state with excess air, and a small amount of unburned gas and ammonia generated in the upstream part of the furnace are completely burned, and the unburned gas is formed of carbon dioxide. Carbon and water vapor are converted, and ammonia is partially decomposed into nitrogen oxides, and the other is decomposed into nitrogen and water vapor.
At the same time, some thermal nitrogen oxides are generated.

Further, a hydrogen sulfide-containing gas is also injected into the furnace. Since the hydrogen sulfide-containing gas is also introduced into the combustion zone with excess air, all of the hydrogen sulfide is finally oxidized to sulfur oxides. Some of the hydrogen is nitrogen oxide from the upstream,
Reacts with thermal nitrogen oxides and contributes to the decomposition of these nitrogen oxides. Most of the gas derived from ammonia and hydrogen sulfide discharged from the outlet of the combustion furnace is water vapor, sulfur oxides, and nitrogen. The sulfur oxide is fixed as gypsum by a flue gas desulfurization method such as a limestone-gypsum method. FIG. 2 shows a conceptual diagram of the reaction in the combustion furnace of the present invention.

[0019]

FIG. 1 is a schematic view of a combustion apparatus including a cross section of a combustion furnace according to an embodiment of the present invention. In this embodiment, about 1 to 60% of H ₂ S-containing gas generated from a regeneration step of an acid gas removing device such as petroleum refining and up to about 50% of NH ₃ -containing gas discharged from an NH ₃ stripper or the like are treated. An example is shown below.

The NH ₃ -containing gas and the auxiliary fuel gas are introduced into the cylindrical combustion furnace 5 from the respective gas supply pipes 3 and 4. At this time, the gas supply pipes 3 and 4 are provided with flow control valves 7 and 8, respectively, and the gas supply pipes 3 and 4 are connected to a mixer 9 where the NH ₃ -containing gas and the auxiliary fuel gas are supplied. The mixture is premixed and introduced into one side of the cylindrical combustion furnace 5 from a nozzle 12 through a pipe 11. Further, a primary air introduction pipe 17 having a flow control valve 15 is connected to the pipe 11 on the one side surface of the combustion furnace 5.

The nozzle 1 depends on which of NH ₃ -containing gas, auxiliary fuel gas and primary air is premixed.
The structure of the piping system leading to 2 can be changed as appropriate. In addition, when a single nozzle 12 cannot cope with it, it can be divided into a plurality of nozzles.

A secondary air supply pipe 2 equipped with a flow control valve 19 is provided near the center of the cylindrical combustion furnace 5 in the longitudinal direction.
0 is connected, and a secondary air supply nozzle 21 that communicates with the inside of the furnace is provided at a tip end thereof. A gas outlet 23 after the reaction is provided at the other end of the combustion furnace 5, and an H ₂ S supply nozzle 24 is provided between the secondary air supply nozzle 21 and the gas outlet 23. An H ₂ S-containing gas is supplied from an H ₂ S gas supply pipe 26 provided with a control valve 25.

In such a combustion apparatus, the theoretical air amount is calculated based on the measured values of the respective compositions and flow rates of the NH ₃ -containing gas and the auxiliary fuel gas, or manually set flow rates, and is introduced from the pipe 17. The flow rate of the primary air is controlled by the flow control valve 15 to a flow rate slightly smaller than the theoretical air rate (eg, 95%), and the premixed fuel gas of the NH ₃ -containing gas and the auxiliary fuel gas is mixed to form a nozzle at the end of the combustion furnace. It is spouted from 12. Thus, the decomposition of the NH ₃ -containing gas by partial combustion is performed. In this case, when the composition of the gas fluctuates over time, it is desirable to always measure and use it as the input value of the arithmetic unit.

The area between the nozzle 12 and the secondary air supply nozzle 21 in the combustion furnace 5 becomes a primary combustion zone (partial combustion zone) of a reducing atmosphere. In this primary combustion zone,
Due to lack of oxygen, most of the NH ₃ gas does not become NOx but is decomposed into N ₂ and water, and a part remains as NH ₃ . In addition, the auxiliary fuel gas partially remains as unburned gas in the form of CO or H ₂ due to partial combustion. Therefore, the partially combusted gas is converted to a mixture of N ₂ , CO ₂ ,
It contains H ₃ . In this example, a coke oven gas containing CO and H ₂ as main components was used as an auxiliary fuel gas.

Next, secondary air is blown into the furnace from a secondary air supply nozzle 21 provided downstream of the primary combustion zone in the combustion furnace 5, and a secondary combustion zone in an oxidizing atmosphere is introduced into the furnace. Let it form.

Thus, the combustion furnace 5 has a primary combustion zone in a reducing atmosphere and a secondary combustion zone in an oxidizing atmosphere. The flow rate of the secondary air is based on the amounts of the H ₂ S-containing gas blown into the furnace further downstream of the position where the secondary air is blown and the NH ₃ -containing gas and auxiliary fuel gas blown into the primary combustion zone. The theoretical air amount is calculated by a computer (not shown), and the target air amount of the entire combustion furnace 5 is calculated from the manually set air ratio (slightly larger than 1), and the primary air flow rate already input is subtracted. The secondary air flow rate control valve 19
Is adjusted to control the amount of secondary air. The inside of the furnace downstream of the secondary air nozzle 21 is in a combustion state with excess air,
A small amount of unburned gas and NH ₃ generated in the upstream part of the furnace are completely burned, the unburned gas becomes CO ₂ and water vapor, NH ₃ partially becomes NOx, and the other decomposes into N ₂ and H ₂ O Is done. At the same time, some thermal NOx is generated.

The amount of air introduced from the secondary air nozzle 21 in addition to the flow rate of the NH ₃ containing gas and auxiliary fuel gas, H ₂
The composition and the flow rate of the S-containing gas are also measured, and the theoretical air amounts for all the gases supplied to the combustion furnace 5 are obtained by a computer. On the other hand, the target air amount of the entire combustion furnace 5 is obtained from the manually set air ratio (however, slightly more than 1), and the target amount of the secondary air amount is determined by reducing the already supplied primary air flow rate, The secondary air flow control valve 19 is adjusted to control the amount of secondary air.

Next, H ₂ S is supplied from the nozzle 24 further downstream.
The H ₂ S-containing gas is injected into the furnace, but the H ₂ S-containing gas is also introduced into the combustion zone with excess air, so that all the H ₂ S is eventually oxidized to SO ₂ , but a part of the H ₂ S Reacts with NOx and thermal NOx from upstream, which contribute to the decomposition of NOx. Most of the gas derived from ammonia and hydrogen sulfide discharged from the outlet 23 of the combustion furnace 5 is H ₂ O
And SO ₂ and N ₂ .

FIG. 2 is a conceptual diagram of the reaction in the combustion furnace. An experiment was actually performed as described below, and as a result, a result was obtained that complete combustion of hydrogen sulfide gas and decomposition of NH ₃ were possible. <Experimental Results> - NH ₃ containing gas _{NH 3: 43%, N 2} : Hydrogen balance weight sulfurized containing gas _{H 2 S: 10%, N} 2: balance weight, the auxiliary fuel gas coke oven gas (COG: main components CO, H ₂ ) ・ Ratio of flow rate NH ₃ -containing gas: H ₂ S-containing gas: auxiliary fuel gas = 6: 6: 10 ・ Air ratio Primary combustion zone: 0.95 Up to secondary air introduction section: 1.18 whole (After H ₂ S combustion): 1.05 Temperature Primary combustion zone: 1000 to 1200 ° C. Near secondary air introduction part: 900 to 1100 ° C. Secondary combustion zone: 800 to 1000 ° C.

<Experimental Results> Table 1 shows data of a comparative example in which NH ₃ gas and H ₂ S gas were not introduced simultaneously and an example of the present invention.

[Table 1]

As shown in the above table, the following values were obtained in the experimental examples and comparative examples according to the present invention. Until NH ₃ remaining moles / turned NH ₃ moles 0.6% secondary air injection unit: the primary combustion zone NOx moles / turned NH ₃ molar total number 3.1% (after hydrogen sulfide combustion): NOx molar number / turned NH ₃ moles 1.6% H ₂ S moles / input H ₂ prior to about 30% of the ammonia in the case of the combustion of ammonia only S moles 0.04% oxidizing combustion zone is converted to NOx Compared with the technology, it is understood that the present invention has a remarkable effect of reducing the NOx generation amount.

Further, as is apparent from the comparison between Experimental Example 1 and Comparative Example 4 in Table 1, the concentration of NOx produced is reduced by half by introducing hydrogen sulfide into the secondary combustion zone. Further, the concentration of hydrogen sulfide in the produced gas is significantly lower than that of the input amount of hydrogen sulfide, which indicates that the decomposition rate is high.

[Brief description of the drawings]

FIG. 1 is a combustion apparatus according to one embodiment of the present invention.

FIG. 2 is a conceptual diagram of a reaction in the combustion furnace of the present invention.

[Description of Signs] 3 NH ₃ -containing gas supply pipe 4 Auxiliary fuel gas supply pipe 5 Combustion furnace 7, 8, 15, 1
9 and 25 the flow control valve 9 mixer 11 premixed gas pipe 12 premixed gas injection nozzle 17 primary air introduction pipe 20 secondary air supply pipe 21 the secondary air supply nozzle 23 gas outlet 24 H ₂ S feed nozzle 26 H ₂ S gas Supply piping

Claims (5)

[Claims] 1. A reducing atmosphere by introducing an auxiliary fuel gas into an ammonia-containing gas and primary air having an air amount smaller than an air amount to completely burn the ammonia-containing gas and the auxiliary fuel gas from a nozzle at a furnace end of a combustion furnace. Combustion in the primary combustion zone, blowing secondary air and hydrogen sulfide-containing gas into the furnace downstream of the primary combustion zone, and completely burning unburned components and hydrogen sulfide-containing gas in the primary combustion zone. Combustion method that simultaneously decomposes ammonia and complete combustion of hydrogen sulfide. 2. The combustion method according to claim 1, wherein hydrogen sulfide-containing gas is blown into a downstream portion of the secondary air blowing position. 3. A combustion furnace having a nozzle for introducing an ammonia-containing gas into an auxiliary fuel gas and a primary air having an air amount smaller than an air amount to completely burn the ammonia-containing gas and the auxiliary fuel gas is provided at a furnace end of the combustion furnace. A primary combustion zone of a reducing atmosphere is formed therein, a nozzle for blowing secondary air and a hydrogen sulfide-containing gas is provided in a furnace downstream of the primary combustion zone, and a secondary combustion zone of an oxidizing atmosphere is formed in the furnace. A combustion device having a combustion furnace for forming ammonia and providing complete combustion of hydrogen sulfide simultaneously, wherein an exhaust gas outlet is provided downstream of the secondary combustion zone. 4. The combustion for simultaneously decomposing ammonia and completely combusting hydrogen sulfide according to claim 3, wherein a nozzle for blowing hydrogen sulfide-containing gas is provided downstream of the position of the nozzle for blowing secondary air. A combustion device having a furnace. 5. The method according to claim 3, wherein the gas blowing direction of the secondary air blowing nozzle and / or the hydrogen sulfide-containing gas is directed toward the upstream of the combustion furnace. A combustion device having a combustion furnace that simultaneously performs complete combustion of hydrogen sulfide.