JPH11263607A - Sulfuric acid producing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce concd. sulfuric acid at a low cost by drastically reducing the cost related to the treatment of spent exhaust gas discharged from an absorption tower. SOLUTION: This sulfuric acid producing equipment is provided with a combustion furnace 3 for burning molten sulfur 2 (elemental sulfur) to form SO2 gas 6, a converter 8 for oxidizing the SO2 gas 6 from the combustion furnace 3 into SO3 gas 9 and an absorption tower 11 for absorbing the SO3 gas 9 from the converter 8 in dil. sulfuric acid 12 to form concd. sulfuric acid 13. In this case, an oxygen supply means 26 for supplying pure oxygen 25 as the combustion supporting gas necessary to combustion to the combustion furnace 3 is connected, and a circulating line 27 is provided to return the exhaust gas 18 from the absorption tower 11 to the combustion furnace 3. Further, the energy of the SO2 gas discharged from the combustion furnace is effectively recovered as the electric power and used in the equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a sulfuric acid production facility.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional sulfuric acid production facility, in which molten sulfur 2 stored in a sulfur dissolving tank 1 is melted.
(Combustion air) from the blower 4 in the combustion furnace 3
Generate SO ₂ gas 6 by mixing to be burned and, after the SO ₂ gas 6 to recover the exhaust heat through waste heat boiler 7, the SO ₂ gas 6 by the action of a catalyst such as platinum in the converter 8 It is oxidized and converted into SO ₃ gas 9, and the reaction heat generated at that time is recovered by a heat exchanger 10 A, and the heat is further recovered by a heat exchanger 10 B arranged as a cooler on the outlet side of the converter 8 to adjust the temperature. Then, the SO ₃ gas 9 whose temperature has been adjusted is absorbed in diluted sulfuric acid 12 in an absorption tower 11 to generate concentrated sulfuric acid 13, and a part of the concentrated sulfuric acid 13 generated here is diluted with dilution water 14.
The diluted sulfuric acid is added to dilute sulfuric acid 12 so as to be circulated and used in the absorption tower 11.

[0003] Further, a waste heat boiler 7 and a heat exchanger 10A,
In 10B, the supplied water 15 is converted into steam 16 by the recovered heat.
The steam 16 is effectively used in the facility. For example, the steam 16 having a high pressure is guided to a steam turbine generator to be used for power generation.

Further, the exhaust gas 18 from the absorption tower 11 containing the unreacted SO ₂ gas 6 which is not converted into SO ₃ gas 9 in the converter 8 and is not absorbed in the diluted sulfuric acid 12 in the absorption tower 11 , is emitted to the atmosphere after being absorbed SO ₂ gas 6 in the neutralizing agent 20 such as caustic soda (NaOH) in SO ₂ scrubber 19, the liquid 21 that has absorbed SO ₂ gas 6 in the SO ₂ scrubber 19, in the tank 22 Further, after a neutralizing agent 23 such as caustic soda (NaOH) is mixed in, it is sent to a wastewater treatment device 24.

The reaction in the combustion furnace 3 is as follows:

S + O ₂ → SO ₂ , and the reaction in the converter 8 is

2SO ₂ + O ₂ → 2SO ₃ , and the reaction in the absorption tower 11 is as follows:

## EQU3 ## SO ₃ + H ₂ O → H ₂ SO ₄

[0006]

However, in the conventional sulfuric acid production facility, the exhaust gas 18 containing the unreacted SO ₂ gas 6 is continuously discharged from the absorption tower 11, and this exhaust gas Gas processing for removing the SO ₂ gas 6 from 18 and drainage processing of the liquid 21 having absorbed the SO ₂ gas 6 are disadvantageous in that the cost increases, and
Although only the removal of unreacted SO ₂ gas 6 is shown in the figure, the exhaust gas 18 also contains NOx (nitrogen oxide) generated by reacting with nitrogen contained in the combustion air 5. Therefore, there is a problem that if the process up to the NOx denitration treatment is completely performed, the cost will further increase.

The present invention has been made in view of the above-mentioned circumstances, and has a sulfuric acid production facility capable of producing concentrated sulfuric acid at a low cost by drastically reducing the cost involved in treating the used exhaust gas discharged from the absorption tower. It is intended to provide.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a combustion furnace for producing SO ₂ gas by burning elemental sulfur, and a converter for oxidizing SO ₂ gas generated in the combustion furnace to produce SO ₃ gas. A high-concentration oxygen as a combustion-supporting gas necessary for combustion in a sulfuric acid production facility having an absorption tower for producing concentrated sulfuric acid by absorbing SO ₃ gas from the converter into diluted sulfuric acid. It is characterized in that a circulation line is provided for connecting oxygen supply means and returning exhaust gas from the absorption tower to the combustion furnace.

In this case, simple sulfur is burned by high-concentration oxygen in the combustion furnace, and high-purity SO ₂ gas is generated with almost no generation of unnecessary products such as NOx. As a component other than the SO ₂ gas contained in the gas discharged from the combustion furnace, a slight excess of oxygen, nitrogen, and other inert gases are present.

[0010] Therefore, SO ₂ gas containing a very small amount of undesired products is led from a combustion furnace to a converter to be oxidized to be converted into SO ₃ gas, and the SO ₃ gas from the converter is converted into diluted sulfuric acid in an absorption tower. When it is absorbed to form concentrated sulfuric acid,
From the absorption tower, an exhaust gas mainly composed of SO ₂ gas remaining slightly unreacted with surplus oxygen, nitrogen, and other inert gases is discharged. Since most of this exhaust gas is returned to the combustion furnace by the circulation line, excess oxygen in the exhaust gas is consumed by combustion with elemental sulfur, and
The SO ₂ gas is also sent to the converter together with the newly generated SO ₂ gas to be consumed. Incidentally, as for nitrogen and other inert gases accumulated in the system, a part of the exhaust gas may be appropriately extracted from the circulation line and treated with a very small-scale facility as in the conventional case.

In the present invention, it is also possible to provide a gas turbine generator driven by SO ₂ gas as a power source between the combustion furnace and the converter. The high-pressure oxygen supply pressure is raised to about several times the atmospheric pressure and the combustion furnace burns elemental sulfur, leading high-pressure SO ₂ gas to the gas turbine generator to efficiently generate power, and The energy of the discharged SO ₂ gas can be effectively recovered as electric power.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an embodiment of the present invention, and the portions denoted by the same reference numerals as those in FIG. 2 represent the same components.

In the sulfuric acid production facility of the present embodiment, the blower 4 which supplies the combustion air 5 to the combustion furnace 3 in the conventional facility shown in FIG. Oxygen supply means 26 for supplying pure oxygen 25 is connected, and equipment for processing exhaust gas 18 from absorption tower 11 and releasing it to the atmosphere is not required. It is characterized in that a circulation line 27 for returning to the above is provided.

Here, the oxygen supply means 26 produces a liquid oxygen 28 by cooling a component having a higher boiling point than oxygen, such as nitrogen, from the liquefied liquid air which is cooled to a critical temperature or lower and pressurized at the same time. An air fractionation device 29, and a pump 3 that guides liquid oxygen 28 from the air fractionation device 29 to increase the pressure
0, and a vaporizer 31 for vaporizing the liquid oxygen 28 supplied by the pump 30 by utilizing the exhaust heat of the equipment.

In this embodiment, in particular, the SO ₂ is provided upstream of the exhaust heat boiler 7 between the combustion furnace 3 and the converter 8.
Gas turbine generator 32 driven by gas 6 as a power source
In order to be able to drive the gas turbine generator 32 without hindrance, the supply pressure of the pure oxygen 25 supplied from the oxygen supply means 26 to the combustion furnace 3 is reduced. After raising the pressure to about several times the atmospheric pressure, the high pressure SO
_Although it is necessary to generate the _two gases 6, if the oxygen supply means 26 is configured as described above, the liquid oxygen 28 is generated by the air fractionator 29, and the pressure is increased by the pump 30 in the liquid phase, The pure oxygen 25 finally vaporized by the vaporizer 31 and sent to the combustion furnace 3 can be easily pressurized to about several times the atmospheric pressure.

In order to return the exhaust gas 18 from the absorption tower 11 to the combustion furnace 3 through the circulation line 27 together with the pure oxygen 25 which is supplied to the combustion furnace 3 after being pressurized as described above, At an appropriate position in the circulation line 27, a compressor 33 that pressurizes and sends the exhaust gas 18 is provided.

If such a configuration is employed, the molten sulfur 2 (single sulfur) from the sulfur dissolving tank 1 is burned by the pure oxygen 25 in the combustion furnace 3 to generate unnecessary products such as NOx. Thus, pure SO ₂ gas 6 is produced, and substantially only excess oxygen is contained as a component other than SO ₂ gas 6 contained in the gas discharged from combustion furnace 3.

Therefore, S from the combustion furnace 3 is free from unnecessary products.
O ₂ converted to SO ₃ gas 9 by the gas 6 is guided to the converter 8 is oxidized and absorbed in the dilute sulfuric acid 12 at the absorption tower 11 to SO ₃ gas 9 from the converter 8 of concentrated sulfuric acid 1
When the exhaust gas 3 is generated, the exhaust gas 18 composed of the SO ₂ gas 6 slightly remaining unreacted with the excess oxygen is discharged from the absorption tower 11, and the exhaust gas 18 is discharged through the circulation line 27 to the combustion furnace 3. The excess oxygen in the exhaust gas 18 is consumed by combustion with the molten sulfur 2 and the SO ₂ gas 6 is sent to the converter 8 together with the newly generated SO ₂ gas 6 for consumption. become.

In this embodiment, in particular, the combustion furnace 3
The gas turbine generator 32 is driven using the high-pressure SO ₂ gas 6 generated in the above as a power source, and the gas turbine generator 3
2, power is efficiently generated, so that the energy of the SO ₂ gas 6 discharged from the combustion furnace 3 is effectively recovered as electric power.

Therefore, according to the above embodiment, high-purity SO ₂ gas 6 can be generated in the combustion furnace 3 without generating unnecessary products such as NOx, and the exhaust gas 18 from the absorption tower 11 can be produced. Can be returned to the combustion furnace 3 by the circulation line 27 and consumed, so that the production process of the concentrated sulfuric acid 13 can be performed as a closed circuit without generating substances to be disposed of outside the system, and the absorption tower 11 can be operated. The concentrated sulfuric acid 13 can be produced inexpensively by eliminating the cost associated with the processing of the used exhaust gas 18 discharged from the fuel cell.

Further, by using pure oxygen 25 as a combustion supporting gas necessary for combustion in the combustion furnace 3, the SO ₂ gas 6 can be reduced in comparison with the case where the combustion air 5 is used as in the prior art. Air components other than oxygen unnecessary for generation (mainly nitrogen)
It is not necessary to consider the flow volume of, and the volume of various devices and piping constituting the sulfuric acid production facility can be reduced without reducing productivity.

Further, if a gas turbine generator 32 driven by the SO ₂ gas 6 as a power source is provided between the combustion furnace 3 and the converter 8 as in this embodiment, the SO ₂ discharged from the combustion furnace 3 is _Since the energy of the _two gases 6 can be effectively recovered as electric power, the production cost can be reduced by using the electric power in the facility, and the concentrated sulfuric acid 13 can be produced at a lower cost.

Incidentally, the sulfuric acid production equipment of the present invention is not limited to the above-described embodiment, but has been described in the case where molten sulfur is introduced into a combustion furnace for combustion. It may be made to burn as it is, and it is not always necessary to be pure oxygen if it is high concentration oxygen, and it is needless to say that various changes can be made without departing from the gist of the present invention. is there.

[0025]

According to the above-mentioned sulfuric acid production equipment of the present invention, the following various excellent effects can be obtained.

(I) According to the first aspect of the present invention, high-purity SO ₂ gas can be produced in a combustion furnace with almost no generation of unnecessary products such as NOx, Since the exhaust gas from the tower can be returned to the combustion furnace through the circulation line and consumed, it is possible to operate the concentrated sulfuric acid production process as a closed circuit with almost no substances to be discarded outside the system, The cost associated with the treatment of the used exhaust gas discharged from the absorption tower can be significantly reduced, and concentrated sulfuric acid can be produced at low cost.

(II) According to the first aspect of the present invention, by using high-concentration oxygen as a supporting gas required for combustion in a combustion furnace, combustion air is used as in the prior art. It is no longer necessary to consider the flow volume of air components (mainly nitrogen) other than oxygen unnecessary for the generation of SO ₂ gas compared to the case where The volume can be reduced without reducing productivity.

(III) According to the second aspect of the present invention, since the energy of SO ₂ gas discharged from the combustion furnace can be effectively recovered as electric power, this electric power is used in the equipment. By doing so, the production cost can be reduced, and concentrated sulfuric acid can be produced even more cheaply.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of an embodiment for implementing the present invention.

FIG. 2 is a system diagram showing a conventional example.

[Explanation of symbols]

2 Molten sulfur (single sulfur) 3 Combustion furnace 6 SO ₂ gas 8 Converter 9 SO ₃ gas 11 Absorption tower 12 Dilute sulfuric acid 13 Concentrated sulfuric acid 18 Exhaust gas 25 Pure oxygen (high concentration oxygen) 26 Oxygen supply means 27 Circulation line 32 Gas turbine Generator

Claims (2)

[Claims] 1. A combustion furnace for producing SO ₂ gas by burning elemental sulfur, a converter for oxidizing SO ₂ gas generated in the combustion furnace to SO ₃ gas, and a SO ₃ gas from the converter Is connected to an oxygen supply means for supplying high-concentration oxygen as a supporting gas required for combustion to a combustion furnace. A sulfuric acid production facility having a circulation line for returning exhaust gas from a tower to a combustion furnace. 2. The sulfuric acid production facility according to claim 1, wherein a gas turbine generator driven by using SO ₂ gas as a power source is provided between the combustion furnace and the converter.