JP2017200682A - Fuel gas treatment method and fuel gas treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel gas treatment method and a fuel gas treatment device that prevent exhaust gas discharged from a regenerative oxidation tower from dispersing into the atmosphere as an atmospheric pollution countermeasure, and save the power required for an electric motor by reducing air used in the regenerative oxidation tower so as to contribute to energy saving.SOLUTION: A fuel gas treatment method includes: (1) a step in which fuel gas containing impurities is caused to come in contact with an absorbent, and the absorbent is caused to absorb the impurities so as to absorb and remove the impurities from the fuel gas; (2) a step that the absorbent that has absorbed the impurities is mixed with air to form a gas-liquid two-phase flow; (3) a step in which the impurities are removed from the absorbent by subjecting the impurities in the absorbent contained in the gas-liquid two-phase flow to oxidation reaction by the bubbling of air bubbles containing oxygen under the presence of an oxidation-reduction catalyst, and the absorbent is regenerated; and (4) a step in which the fuel gas from which the impurities are removed is mixed with surplus exhaust gas of the air used for the oxidation reaction.SELECTED DRAWING: None

Description

  The present invention relates to a fuel gas processing method and a fuel gas processing apparatus.

  Conventionally, fuel gas such as coke oven gas contains harmful impurities such as hydrogen sulfide and hydrogen cyanide. When untreated fuel gas is used, sulfur compounds are produced during combustion, which causes problems such as corrosion of equipment and air pollution. Therefore, before using the fuel gas, it is necessary to remove impurities such as hydrogen sulfide and hydrogen cyanide, that is, desulfurize and decyanide.

  As a desulfurization and decyanide method for a fuel gas containing hydrogen sulfide and hydrogen cyanide, for example, wet desulfurization methods such as the Fumax method and the Rodax method are known.

The desulfurization / decyanization facilities of the Fumax method and the Rodax method consist of an absorption tower, a regenerative oxidation tower and its auxiliary facilities. The absorption tower is a device that removes hydrogen sulfide, hydrogen cyanide, and the like in the fuel gas by absorbing them in the absorption liquid. On the other hand, the regenerative oxidation tower makes an absorbing solution that does not contain hydrogen sulfide and hydrogen cyanide by bringing the absorbing solution that has absorbed hydrogen sulfide and hydrogen cyanide into contact with an oxygen-containing gas such as air (hereinafter also referred to as air) by bubbling. This is an apparatus that recovers hydrogen sulfide and hydrogen cyanide by generating free sulfur or fixing them as sulfur compounds.

  In the regenerative oxidation tower, an oxidation method is known in which air is introduced from the bottom of the tower and air bubbles are introduced into the absorbing solution using an air diffuser. In the oxidation method, the air in the diffuser pipe is sent separately to the regeneration oxidation tower separately from the liquid, but the contact efficiency between the liquid and the air is poor and it is necessary to supply a large volume of air (for example, Patent Document 1).

  As described above, the conventionally known regeneration oxidation tower requires a large volume of air, and as a result, there is a problem that the amount of exhaust gas discharged from the regeneration oxidation tower by the oxidation reaction is large.

  In addition, when the oxidation reaction becomes insufficient due to fluctuations in the load such as coke oven gas flow rate or hydrogen sulfide concentration, or fluctuations in the operating conditions of the regenerative oxidation tower, exhaust gas containing a large amount of hydrogen sulfide, hydrogen cyanide, etc. It was dissipated in and was not environmentally favorable.

  In order to solve such problems, the emission of exhaust gas discharged from the regenerative oxidation tower is prevented from being released into the atmosphere, and the amount of air is reduced to reduce the motor power required to send in air. Development of desulfurization method and desulfurization equipment that contributes to this is required.

JP-A-8-196863

  The present invention prevents atmospheric emission of exhaust gas discharged from the regenerative oxidation tower as a measure against air pollution, and contributes to energy saving. Therefore, the required motor power is reduced by reducing the air used in the regenerative oxidation tower, It is an object of the present invention to provide a fuel gas processing method and a fuel gas processing apparatus.

  As a result of intensive studies to achieve the above object, the present inventors have installed a premixing nozzle in the regenerative oxidation tower that mixes an absorbing liquid that has absorbed impurities and air to form a gas-liquid two-phase flow. By doing so, it has been found that the above-mentioned problems can be achieved. The present invention has been further researched and completed.

  That is, the present invention includes the following fuel gas processing method and fuel gas processing apparatus.

Item 1. A method for treating fuel gas, comprising:
(1) A step of absorbing and removing the impurities from the fuel gas by bringing a fuel gas containing impurities into contact with an absorbing liquid and absorbing the impurities into the absorbing liquid;
(2) A step of mixing the absorbing liquid that has absorbed the impurities and air to form a gas-liquid two-phase flow;
(3) The impurities in the absorption liquid contained in the gas-liquid two-phase flow are oxidized from the absorption liquid by bubbling air bubbles containing oxygen in the presence of a redox catalyst. And (4) mixing the fuel gas from which the impurities have been absorbed and the excess exhaust gas out of the air subjected to the oxidation reaction,
A method comprising:

  Item 2. Item 2. The fuel gas processing method according to Item 1, wherein the impurity contains at least one selected from the group consisting of hydrogen sulfide and hydrogen cyanide.

  Item 3. Item 3. The fuel gas treatment method according to Item 1 or 2, wherein the absorbing liquid is an alkaline aqueous solution.

  Item 4. Item 4. The fuel gas treatment method according to any one of Items 1 to 3, wherein the redox catalyst contains a quinone or an iron chelate complex.

  Item 5. Item 5. The method for treating fuel gas according to any one of Items 1 to 4, wherein, in the step (3), the regenerated absorbent is circulated and used in the step (1).

  Item 6. Item 6. The fuel gas processing method according to any one of Items 1 to 5, wherein, in the step (4), an oxygen concentration in a gas obtained by mixing the fuel gas and the exhaust gas is controlled to 1 Vol% or less.

Item 7. A fuel gas processing apparatus comprising an absorption tower, a premixing nozzle, a regenerative oxidation tower, a fuel gas line, an exhaust gas discharge pipe and a mixing section,
The absorption tower has means for absorbing and removing the impurities from the fuel gas by bringing a fuel gas containing impurities into contact with an absorbing liquid and absorbing the impurities into the absorbing liquid.
The premixing nozzle has means for mixing the absorption liquid and air to form a gas-liquid two-phase flow;
The regenerative oxidation tower causes the impurities in the absorption liquid blown into the regenerative oxidation tower as the gas-liquid two-phase flow to oxidize by bubbling air bubbles containing oxygen in the presence of a redox catalyst. Means for regenerating the absorbent,
The fuel gas line has means for introducing the fuel gas from which the impurities have been removed into the mixing section;
The exhaust gas exhaust pipe has a means for exhausting excess exhaust gas from the air subjected to the oxidation reaction,
The said mixing part is an apparatus which has a means to mix the said fuel gas and the said waste gas.

  Item 8. Item 8. The fuel gas processing apparatus according to Item 7, wherein the impurity contains at least one selected from the group consisting of hydrogen sulfide and hydrogen cyanide.

  Item 9. Item 9. The fuel gas processing apparatus according to Item 7 or 8, wherein the absorbing liquid is an alkaline aqueous solution.

  Item 10. Item 10. The fuel gas processing device according to any one of Items 7 to 9, wherein the redox catalyst contains a quinone or an iron chelate complex.

  Item 11. Item 11. The fuel gas processing apparatus according to any one of Items 7 to 10, further comprising means for circulating and using the regenerated absorbent in the regenerative oxidation tower.

  Item 12. Item 12. The fuel gas processing apparatus according to any one of Items 7 to 11, further comprising means for controlling an oxygen concentration in a gas obtained by mixing the fuel gas and the exhaust gas to 1 Vol% or less.

  The fuel gas processing method of the present invention has the advantage that it contributes to environmental measures and energy saving by preventing the emission of exhaust gas to the atmosphere and reducing the amount of air to reduce the motor power required for air supply. .

It is a block diagram which shows typically suitable one Embodiment of the processing apparatus for enforcing the processing method of the fuel gas of this invention. It is a longitudinal cross-sectional view of the premixing nozzle in the processing apparatus of the fuel gas of this invention. It is the figure which installed the premixing nozzle in the processing apparatus of the fuel gas of this invention beside the bottom part of the regeneration oxidation tower. It is the figure which installed the bubble separator in the tower | column of the reproduction | regeneration oxidation tower | column in the processing apparatus of the fuel gas of this invention. It is a longitudinal cross-sectional view of the air diffusing device used in Comparative Example 1.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications.

  FIG. 1 is a block diagram schematically showing a preferred embodiment of a processing apparatus for carrying out the fuel gas processing method of the present invention.

  As shown in FIG. 1, the fuel gas processing apparatus 1 of the present invention includes an absorption tower 3, a premixing nozzle 8, a regeneration oxidation tower 9, a fuel gas line 5, an exhaust gas discharge pipe 11, and a mixing section 13.

  A fuel gas such as coke oven gas containing impurities such as hydrogen sulfide and hydrogen cyanide (hereinafter also referred to as “impurities”) is introduced into the absorption tower 3 through the fuel gas introduction pipe 2.

  Examples of the filler in the absorption tower include irregular packings such as lashing, terrarette, and Hilex, or regular wooden lattices.

  The introduced fuel gas flows toward the upper part of the absorption tower 3 while passing through the gap between the fillers for improving the gas-liquid contact efficiency, and sulfidized by making countercurrent contact with the absorbent supplied from the upper spray nozzle 4. Impurities such as hydrogen and hydrogen cyanide can be absorbed and removed by the absorbing solution.

  The fuel gas from which impurities have been absorbed and removed can be taken out from a fuel gas line 5 installed at the top of the absorption tower 3. The extracted fuel gas is mixed with the exhaust gas described below and can be used as a fuel for a coke oven, a heating furnace, or an annealing furnace.

  As the absorbent used in the absorption tower 3, an alkaline aqueous solution is preferable. Specifically, in order to maintain alkali, in many cases, it is supplied by consuming ammonia in the fuel gas. When ammonia does not exist or is insufficient in the fuel gas, an aqueous sodium carbonate solution or an aqueous sodium hydroxide solution is added to the absorbent.

  The absorption liquid from which impurities have been absorbed and removed is supplied to the premixing nozzle 8 installed on the end plate at the bottom of the regenerative oxidation tower 9 through the liquid inlet pipe 7 by the pump 6. The premixing nozzle 8 can be installed on the end plate of the regeneration oxidation tower 9.

  One or a plurality of premixing nozzles 8 can be installed, and the number of the premixing nozzles 8 is appropriately changed depending on the amount of fuel gas and the impurity concentration in the fuel gas.

  As shown in FIG. 2, the premixing nozzle 8 has a cylindrical straight tubular shape into which air is fed from a lateral portion of a cylindrical liquid feeding tube into which an absorbing liquid that has absorbed impurities in the fuel gas is fed. A gas inlet pipe 15 is connected in communication.

  The absorption liquid that has absorbed the supplied impurities and air are mixed in the premixing nozzle 8 to form a gas-liquid two-phase flow.

  It is considered appropriate to express the gas-liquid contact efficiency by the premixing nozzle 8 by the overall capacity coefficient (KLa), but since it takes a long time to measure KLa, a gas hold having a rough correspondence with KLa. The gas-liquid contact efficiency is expressed by up (HG).

  It is known that HG is improved by the effect of the premixing nozzle 8, but this utilizes the bubble dispersion effect that occurs when air is injected from the side of the liquid flow tube that flows at high speed in the nozzle. .

  Moreover, it is known that HG shows an improvement tendency, so that an average bubble diameter is small. Specifically, when the average bubble diameter is 1 mm or less, the dependency of HG on the bubble diameter increases.

  From the above, the gas-liquid contact efficiency is further improved by the premixing nozzle 8, and the air amount can be greatly reduced and the apparatus can be downsized.

  The formed gas-liquid two-phase flow can be blown into the regeneration oxidation tower 9.

Further, in the present invention, as shown in FIG. 3, the premixing nozzle 8 can be installed beside the bottom of the regenerative oxidation tower 9.
Even when the premix nozzle 8 is installed on the side of the bottom of the regenerative oxidation tower 9, a single or a plurality of premix nozzles 8 can be installed, and the number of installation is appropriately changed according to the amount of fuel gas and the impurity concentration in the fuel gas.

  An oxidation-reduction catalyst is continuously added as an aqueous solution to the absorbing solution blown into the regeneration oxidation tower 9. Examples of the redox catalyst include quinone catalysts and iron chelate complexes. Examples of the quinone catalyst include naphthoquinone sulfonic acid.

  Impurities contained in the absorption liquid contained in the gas-liquid two-phase flow supplied to the regenerative oxidation tower 9 are recovered as free sulfur or sulfur-capable substances by oxidation reaction by bubbling of air bubbles in the presence of a redox catalyst. And the absorbing solution is regenerated.

  Excess regeneration air supplied to the regeneration oxidation tower 9 is discharged as exhaust gas from the top of the tower.

  The regenerated absorption liquid is circulated and used in the absorption tower 3. Specifically, the regenerated absorption liquid can be sent to the absorption tower 3 through the circulating liquid circuit 10 installed on the side surface of the regenerative oxidation tower 9 and reused as the absorption liquid from the spray nozzle 4.

  The exhaust gas discharged from the regenerative oxidation tower 9 desirably has a low oxygen concentration in the air from the viewpoint of reusing the exhaust gas. Specifically, it is required to control the oxygen concentration in the exhaust gas so that the oxygen concentration after mixing the fuel gas and the exhaust gas is 1 Vol% or less.

  Exhaust gas is discharged from an exhaust gas discharge pipe 11 installed at the top of the regeneration oxidation tower 9. The exhaust gas discharge pipe 11 is divided into two branches in the middle.

  The exhaust gas discharge pipe 11 is provided with a valve 12 at an intermediate position and is normally closed. When the oxygen concentration in the mixed gas after the mixing unit 13 is 1 Vol% or more, the valve 12 is opened, and the exhaust gas discharged from the regenerated oxidation tower 9 can be discharged into the atmosphere.

  A mixing unit 13 is installed in the exhaust gas discharge pipe 11, and the fuel gas line 5 is connected to the mixing unit 13. The exhaust gas discharged from the regeneration oxidation tower 9 can be mixed with the fuel gas introduced into the fuel gas line 5.

  As for the mixed gas, the oxygen concentration in the mixed gas is constantly monitored in the oxygen concentration measuring unit 14 installed in the middle of the fuel gas line 5.

  When the oxygen concentration in the fuel gas or the exhaust gas is high and the oxygen concentration in the mixed gas exceeds 1 Vol%, the amount of air sent to the regenerative oxidation tower 9 is adjusted by the air control valve 20, so that the oxygen in the exhaust gas The concentration is controlled, and as a result, the oxygen concentration in the mixed gas is indirectly controlled.

  When adjusting the amount of air, it must be carried out while monitoring HG or the like so that the regeneration capacity of the regeneration oxidation tower does not become insufficient.

  As shown in FIG. 4, it is possible to install a bubble separator 16 in the regeneration oxidation tower 9. First, a part of the absorbing liquid can be extracted from the regeneration oxidation tower 9 by the bubble separator 16.

  The extracted absorption liquid can be supplied into the tower by the foam extinguishing pump 17 through the foam extinguishing circulation line 18 and from the foam extinguishing spray nozzle 19 at the upper part of the regeneration oxidation tower 9. Thereby, there exists an effect which eliminates a bubble when a bubble generate | occur | produces in the absorption liquid surface in the reproduction | regeneration oxidation tower | column 9. FIG.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited only to these.

Example 1
The present invention was implemented at the time of renewal of the regeneration oxidation tower of the Takahax-type desulfurization facility. Thirty-five premix nozzles (product name: premix nozzle, manufacturer / seller: Osaka Gas Engineering) were installed on the end plate of the regenerated oxidation tower.

  First, coke oven gas containing hydrogen sulfide and hydrogen cyanide was introduced into an absorption tower through a fuel gas introduction pipe, and hydrogen sulfide and hydrogen cyanide were absorbed and removed from the coke oven gas.

  The coke oven gas from which hydrogen sulfide and hydrogen cyanide had been removed was discharged to the fuel gas line.

  The absorbing liquid containing hydrogen sulfide and hydrogen cyanide was fed into the premixing nozzle through the liquid feeding pipe.

  For each premix nozzle, a gas inlet pipe for feeding air and a liquid inlet pipe for feeding the absorbing liquid were attached.

For one premixing nozzle, the amount of air from the gas inlet tube is 94 Nm ³ / h and the amount of liquid absorbed from the liquid inlet tube is 100 m ³ / h. The ratio (gas / liquid mixture ratio) was 0.94.

  The introduced air and the absorbing liquid were mixed in a premixing nozzle to form a gas-liquid two-phase flow.

  Each premixing nozzle was fed with an absorption liquid flow rate of 5 m / s and an air flow rate of about 10 m / s, and a gas-liquid two-phase flow was formed in the premixing nozzle and blown into the regeneration oxidation tower.

The total amount of air blown from the 35 premixing nozzles into the regenerative oxidation tower is 3300 Nm ³ (the air amount per premixing nozzle is 94 Nm ³ / h) as a standard, 3000 to 3600 Nm ³ / (premixing nozzle) The amount of each air was adjusted in the range of 86 to 103 Nm ³ / h). The total amount of absorbing liquid from the liquid inlet tube was 3500 m ³ / h (the amount of air per premixing nozzle was 100 Nm ³ / h). The amount of fuel gas at this time was 105000 Nm ³ / h.

  In the regenerative oxidation tower, hydrogen sulfide contained in the gas-liquid two-phase flow is oxidized and recovered as free sulfur by bubbling air bubbles in the presence of a quinone catalyst, and hydrogen cyanide generates and fixes the free sulfur and sulfur compounds. It was.

  The absorption liquid regenerated by bubbling air in the regenerative oxidation tower was sent to the absorption tower via the circulating liquid circuit and reused in the absorption tower.

  The amount of incoming air was adjusted so that the concentration of oxygen contained in the exhaust gas discharged from the regenerative oxidation tower would be 13 Vol% or less.

  Even when the exhaust gas is mixed with the fuel gas from which impurities have been removed by the absorption tower as a result of the adjustment, the oxygen concentration in the mixed gas is 1 Vol% or less, so that the exhaust gas is not released into the atmosphere, Reinjection was possible.

Comparative Example 1
An example of a Takahax type desulfurization facility that does not use a premixing nozzle is shown.

When the amount of absorbing liquid from the liquid inlet pipe is 3000 m ³ / h, whereas the amount of air from the gas inlet pipe is 5000 to 6000 Nm ³ / h, hydrogen sulfide and hydrogen cyanide are removed, The regenerated absorption liquid could be reused in the absorption tower.

  However, since the oxygen concentration contained in the exhaust gas is high and the oxygen concentration after mixing the fuel gas and the exhaust gas exceeds 1 Vol%, re-injection into the fuel gas line could not be performed and the atmosphere was released.

DESCRIPTION OF SYMBOLS 1 Fuel gas processing apparatus 2 Fuel gas introduction pipe 3 Absorption tower 4 Spray nozzle 5 Fuel gas line 6 Pump 7 Liquid inlet pipe 8 Premixing nozzle 9 Regeneration oxidation tower 10 Circulating liquid circulation line 11 Exhaust gas discharge pipe 12 Valve 13 Mixing part 14 Oxygen Concentration Measurement Unit 15 Gas Inlet Pipe 16 Bubble Separator 17 Foam Pump 18 Foam Circulation Line 19 Foam Spray Nozzle 20 Air Control Valve

Claims (12)

A method for treating fuel gas, comprising:
(1) A step of absorbing and removing the impurities from the fuel gas by bringing a fuel gas containing impurities into contact with an absorbing liquid and absorbing the impurities into the absorbing liquid;
(2) A step of mixing the absorbing liquid that has absorbed the impurities and air to form a gas-liquid two-phase flow;
(3) The impurities in the absorption liquid contained in the gas-liquid two-phase flow are oxidized from the absorption liquid by bubbling air bubbles containing oxygen in the presence of a redox catalyst. And (4) mixing the fuel gas from which the impurities have been absorbed and the excess exhaust gas out of the air subjected to the oxidation reaction,
A method comprising:   The method for treating a fuel gas according to claim 1, wherein the impurity contains at least one selected from the group consisting of hydrogen sulfide and hydrogen cyanide.   The fuel gas processing method according to claim 1, wherein the absorbing liquid is an alkaline aqueous solution.   The processing method of the fuel gas in any one of Claims 1-3 in which the said oxidation-reduction catalyst contains a quinone or an iron chelate complex.   The method for processing a fuel gas according to any one of claims 1 to 4, wherein, in the step (3), the regenerated absorption liquid is circulated and used in the step (1).   The method of processing a fuel gas according to any one of claims 1 to 5, wherein in the step (4), an oxygen concentration in a gas obtained by mixing the fuel gas and the exhaust gas is controlled to 1 Vol% or less. A fuel gas processing apparatus comprising an absorption tower, a premixing nozzle, a regenerative oxidation tower, a fuel gas line, an exhaust gas discharge pipe and a mixing section,
The absorption tower has means for absorbing and removing the impurities from the fuel gas by bringing a fuel gas containing impurities into contact with an absorbing liquid and absorbing the impurities into the absorbing liquid.
The premixing nozzle has means for mixing the absorption liquid and air to form a gas-liquid two-phase flow;
The regenerative oxidation tower causes the impurities in the absorption liquid blown into the regenerative oxidation tower as the gas-liquid two-phase flow to oxidize by bubbling air bubbles containing oxygen in the presence of a redox catalyst. Means for regenerating the absorbent,
The fuel gas line has means for introducing the fuel gas from which the impurities have been removed into the mixing section;
The exhaust gas exhaust pipe has a means for exhausting excess exhaust gas from the air subjected to the oxidation reaction,
The said mixing part is an apparatus which has a means to mix the said fuel gas and the said waste gas.   The fuel gas processing apparatus according to claim 7, wherein the impurity contains at least one selected from the group consisting of hydrogen sulfide and hydrogen cyanide.   The fuel gas processing apparatus according to claim 7 or 8, wherein the absorption liquid is an alkaline aqueous solution.   The fuel gas processing apparatus according to claim 7, wherein the redox catalyst contains a quinone or an iron chelate complex.   The fuel gas processing apparatus according to any one of claims 7 to 10, further comprising means for circulating and using the regenerated absorbent in the regenerative oxidation tower.   The fuel gas processing apparatus according to any one of claims 7 to 11, further comprising means for controlling an oxygen concentration in a gas obtained by mixing the fuel gas and the exhaust gas to 1 Vol% or less.

Images