JP2001262165A - Apparatus for desulfuring anaerobic biogas and method for regenerating used desulfuring agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely and efficiently regenerate a used desulfuring agent in a desulfuring apparatus without accompanying the fear of heat generation and ignition. SOLUTION: This apparatuses 2A and 2B for desulfuring anaerobic biogas, packed with iron oxide pellets as the desulfuring agent have temperature sensors 3A and 3B for detecting temperatures in the desulfuring apparatuses 2A and 2B, means for introducing an oxygen-containing gas for oxidizing and regenerating the used desulfuring agent in the desulfuring apparatuses 2A and 2B, and means for controlling the flowing quantities of the oxygen-containing gas so that the temperatures in the desulfuring apparatuses 2A and 2B may not exceed a prescribed value. When carrying out the regeneration by using the desuifuring apparatuses, the regeneration treatment is finished when the difference of the temperatures in the desulfuring apparatuses, and an outside air temperature, the temperature of the fed oxygen-containing gas or the temperature in the desulfuring apparatus under desulfuring treatment becomes a prescribed value or less, or the regeneration treatment is finished when the increase of the oxygen concentration in the waste gas discharged from the desulfuring apparatus under the regeneration treatment is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desulfurization apparatus for removing hydrogen sulfide from an anaerobic biogas mainly composed of methane and carbon dioxide generated from an anaerobic wastewater treatment apparatus, an anaerobic sludge digestion apparatus and the like. And a method for regenerating a used desulfurizing agent.

[0002]

2. Description of the Related Art An anaerobic biological treatment apparatus such as an anaerobic wastewater treatment apparatus and an anaerobic sludge digestion apparatus generates anaerobic biogas containing methane and carbon dioxide as main components. This anaerobic biogas can be used effectively as fuel for boilers and the like, but anaerobic biogas contains hydrogen sulfide. It is necessary to desulfurize the anaerobic biogas to remove the contained hydrogen sulfide because there is a risk of corroding the piping and equipment.

Conventionally, as a method for desulfurizing anaerobic biogas, iron oxide pellets are treated with a hydrogen sulfide absorbent (hereinafter referred to as "desulfurizing agent").
Called. ), A dry method of desulfurization by the following reaction, a wet method of a scrubber method using an alkaline cleaning liquid,
A biological desulfurization method using a sludge solution in which a sulfur-oxidizing bacterium has been propagated as a detergent has been used. Among them, the dry method has a low cost for equipment and does not require waste liquid treatment, so the UA
It is widely used as an SB (Upflow Anaerobic Sludge Blanket: upflow anaerobic sludge bed) type wastewater treatment system and ancillary equipment for anaerobic sludge digestion equipment.

[0004] _{Fe 2 O 3 + 3H 2 S} → Fe 2 S 3 + 3H 2 O However, in the dry method, taken out the used desulfurizing agent from the desulfurizer, must be filled with new desulfurizing agent and thus However, there is a problem that the cost for purchasing the desulfurizing agent, the cost for replacing the desulfurizing agent, and the cost for disposing of the used desulfurizing agent are high. In particular, as a recent trend,
Efforts are being made to reduce waste as much as possible at many business sites, and technology is needed to reduce or eliminate the amount of used desulfurizing agents. They have been taken out, regenerated and reused.

[0005] Since the used desulfurizing agent is a pellet mainly composed of iron sulfide, it can be oxidized by the following reaction in the presence of oxygen, converted into iron oxide, and regenerated and reused. .

[0006] Fe₂S₃+9/2 O₂→ Fe₂O₃+ 3SO₂  This method is a conventionally known method.
Japanese Patent No. 3681 describes that the regeneration temperature is 7
Above 00 ° C, iron oxide is reduced and sintering occurs
(Sintered body), and iron sulfate is generated at 400 ° C or lower.
Therefore, in order to prevent these, the regeneration temperature is set to 40
It is described that the temperature is controlled to 0 to 700 ° C.

[0007]

However, the above-mentioned regeneration of the used desulfurizing agent is an exothermic reaction accompanied by extremely large heat of reaction, and may be ignited and burned in extreme cases. Absent. In addition, because of the danger of ignition and combustion as described above, generally, the used desulfurizing agent is not regenerated at the site where the desulfurizing agent is used. Therefore, it is desired to develop a technology that can be regenerated on site without carrying out such a desulfurizing agent.

The present invention has been made in view of the above-mentioned conventional circumstances, and can safely and efficiently regenerate a used desulfurizing agent in a desulfurization apparatus without causing danger of heat generation and ignition. An object of the present invention is to provide an anaerobic biogas desulfurization apparatus and a method for regenerating a used desulfurization agent.

[0009]

An anaerobic biogas desulfurization apparatus according to the present invention is a temperature sensor for detecting a temperature in a desulfurization apparatus in an anaerobic biogas desulfurization apparatus filled with iron oxide pellets as a desulfurization agent. Means for introducing an oxygen-containing gas for oxidizing and regenerating a used desulfurizing agent in the desulfurization apparatus, and controlling a flow rate of the oxygen-containing gas so that the temperature in the desulfurization apparatus does not exceed a predetermined value. And means for performing the following.

[0010] With this anaerobic biogas desulfurization device, an oxygen-containing gas can be introduced into the desulfurization device and the used desulfurization agent can be regenerated in the desulfurization device. The trouble of transportation and refilling can be saved. In addition, during this regeneration, the temperature inside the desulfurization unit is detected by the temperature sensor, and the flow rate of the oxygen-containing gas is controlled so that this temperature does not exceed a predetermined value, so that accidents due to heat generation and ignition can be prevented. In addition, the reproducing process can be performed safely and efficiently.

A method for regenerating a used desulfurizing agent according to claim 2 is as follows.
A method for regenerating a used desulfurizing agent using the anaerobic biogas desulfurization apparatus according to claim 1, wherein the temperature in the desulfurization apparatus during the regeneration processing, the outside air temperature, the temperature of the oxygen-containing gas introduced, or the desulfurization processing The regeneration process is terminated when the temperature difference from the internal temperature of the desulfurization device becomes equal to or less than a predetermined value.

According to this method, when the used desulfurizing agent is regenerated in the desulfurizer, the regenerating process can be automatically terminated when the temperature of the desulfurizing agent no longer rises.

[0013] The method for regenerating the used desulfurizing agent according to claim 3 comprises:
A method for regenerating a used desulfurizing agent using the anaerobic biogas desulfurization apparatus according to claim 1, wherein the regeneration processing is terminated by detecting an increase in the oxygen concentration of exhaust gas discharged from the desulfurization apparatus during the regeneration processing. It is characterized by doing.

In this method, when the used desulfurizing agent is regenerated in the desulfurization unit, the regeneration process is automatically terminated by an increase in the oxygen concentration of the exhaust gas discharged from the desulfurization unit (hereinafter referred to as "regenerated exhaust gas"). can do.

[0015] The method for regenerating the used desulfurizing agent according to claim 4 is as follows.
The anaerobic biogas desulfurization device of claim 1 is installed in two or more lines in parallel, and at least one of the lines performs the anaerobic biogas desulfurization treatment, and the remaining line is at least one of the lines. The method is characterized in that the used desulfurizing agent is regenerated in accordance with the method of 3.

According to this method, while the desulfurization treatment is performed in one series, the regeneration treatment is performed in the other series, and the desulfurization and the regeneration are alternately repeated, whereby the desulfurization treatment of the anaerobic biogas is interrupted. It is possible to regenerate the used desulfurization agent without continuation.

The inventor of the present invention has conducted studies to solve the above-mentioned problems. As a result, the oxygen-containing gas such as air is introduced into the desulfurization apparatus while controlling so as not to generate significant heat.
It has been found that it is effective to perform oxidative regeneration gently. As the oxygen-containing gas, a gas other than air containing oxygen may be used instead of air. Oxygen or air may be introduced at a controlled flow rate at the same time as anaerobic biogas is passed.

As a specific means for preventing this remarkable heat generation, in the apparatus of the present invention, a temperature sensor is installed at at least one place in the desulfurization apparatus, and the temperature of the oxygen-containing gas is reduced so that the temperature does not exceed a predetermined value. Control the inflow. The flow rate of the oxygen-containing gas may be fluctuated so that the indicated value of the temperature sensor is constant, and a constant flow of the oxygen-containing gas is intermittently supplied so that the indicated value of the temperature sensor is within a certain range. You may let it. The upper limit of the temperature can be determined arbitrarily,
Assuming that the heat insulating material is not wound around the desulfurization device, the temperature is desirably 50 ° C. or less from the viewpoint of preventing the burn of the operator. On the other hand, when the reaction temperature is relatively low (for example, 250
° C or lower), a part of iron sulfide is S
Until O ₂ without being oxidized, and elemental sulfur.

[0019] Fe₂S₃+ 3/2 O₂→ Fe₂O₃+ 3S⁰  In this case, the reproduced Fe₂O₃Hydrogen sulfide absorption capacity
Has no problem, but S⁰Tower pressure drop caused by
Therefore, the number of times that it can be used
It is inferior in comparison.

[0020] or more views that can be used perform processing at a high temperature by performing the appropriate measures against heat generation, or of selecting any performs processing by a simple device with no heat insulating material on which allowed the occurrence of S ⁰ It is. In the high-temperature treatment, when the reaction temperature is 400 ° C. or lower, the method disclosed in
As described in Japanese Patent No. 73681, the production of iron sulfate occurs.

In order to smoothly carry out the oxidation reaction at the time of regeneration, a heater may be provided in the desulfurization apparatus to heat the desulfurizing agent at the start of regeneration or during regeneration to accelerate the reaction.

When all the desulfurizing agents are oxidized and regenerated, and the oxidation reaction no longer occurs, the temperature rise in the desulfurization unit is stopped. Use this phenomenon to know when playback has ended,
Stopping the injection of the oxygen-containing gas and subjecting it to the desulfurization treatment again is also an effective operation method.

The termination of the oxidative regeneration can also be performed by detecting the oxygen concentration of the regenerated exhaust gas discharged from the desulfurizer during the regeneration. The aim is to terminate the regeneration when the oxygen concentration of the regenerated exhaust gas reaches about 1%. However, if the temperature in the desulfurization unit is within the allowable range, the inflow of air and oxygen can be reduced by the reaction with iron sulfide. Since the regeneration time can be shortened by setting the equivalent amount or more, the upper limit of the oxygen concentration of the regeneration exhaust gas in this case is not limited to the above value.

In practicing the present invention, claim 4
According to the method described above, two or more desulfurization devices are installed, desulfurization treatment is performed using at least one line, and regeneration treatment is performed in at least one other line, without interrupting the desulfurization treatment of anaerobic gas. Reproduction processing can be advantageously performed.

Since the regenerated exhaust gas discharged from the desulfurization unit during the regenerating process contains sulfurous acid gas, an appropriate exhaust gas treatment may be required. Examples of the exhaust gas treatment method in this case include a dilution treatment, a water washing treatment, and an absorption treatment with an alkali agent.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the anaerobic biogas desulfurization apparatus and the method for regenerating a used desulfurization agent according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a system diagram of a UASB type wastewater treatment system provided with a desulfurization device according to an embodiment of the present invention.

In this UASB type wastewater treatment system, UASB
The anaerobic biogas discharged from the apparatus 1 is converted into a desulfurization column 2A of two towers filled with iron oxide pellets as a desulfurizing agent.
2B is introduced into one of them to perform a desulfurization treatment, and air as an oxygen-containing gas is introduced into the other to regenerate a used desulfurization agent, and the desulfurization treatment and the regeneration treatment are alternately performed in the following procedure. In this way, desulfurization of anaerobic biogas is continuously performed. Incidentally, a thermometer respectively 3A, 3B are provided on the desulfurization column 2A, 2B in FIG. 1, 4 flowmeter anaerobic _biogas, V 1 ~V ₈ is off valves. First, the valves V ₂ and V ₇ are opened, and the other valves are closed.
The anaerobic biogas is fed to the desulfurization column 2B, and the anaerobic biogas is desulfurized. When the desulfurization column 2B reaches breakthrough, i.e., for example, when the hydrogen sulfide concentration in the treated gas becomes the detected value or more, the valve V _2, V ₇ closed, the valve V _4, V ₈ are opened, desulfurization A regeneration process is performed by introducing air into the column 2B. At the same time, the valves V ₁ and V ₅ are opened, the anaerobic biogas is introduced into the desulfurization column 2A, and the desulfurization process is performed in the desulfurization column 2A. When regenerating the desulfurization column 2B, use a thermometer 3B
The air flow rate is controlled so that the detected temperature is equal to or lower than a predetermined value. This flow rate control may be performed by increasing or decreasing the amount of air introduced into the desulfurization column 2B, or by switching between introducing and stopping air. By controlling the flow rate of the air in this way, the temperature of the desulfurization column 2B becomes 50 ° C.
Hereinafter, it is preferable to adjust the temperature to preferably 45 to 50 ° C. If this temperature exceeds 50 ° C.,
There is a danger that the oxidation reaction may occur, and if it is too low, the oxidation reaction does not proceed smoothly. As described above, the desulfurization column may be provided with a heater to prevent delay of the oxidation reaction due to supercooling. If the temperature of the desulfurization column 2B does not rise, and the temperature difference between the outside air temperature, the temperature of the introduced air, and the temperature of the desulfurization column during the desulfurization treatment falls below a predetermined value, for example, 3 ° C. or less, heat is generated. , The regeneration is considered to have been completed, and the valves V ₄ and V ₈ are closed to terminate the regeneration of the desulfurization column 2B. When the regeneration is completed, the oxygen concentration of the regenerated exhaust gas increases, that is, the oxidation reaction does not proceed, and the desulfurization column 2B
The determination may be made by detecting that oxygen is no longer consumed in the inside. After the regeneration of the desulfurization column 2B is completed, the desulfurization column 2B
When A reaches breakthrough, the valves V ₁ , V ₄ , V ₅ , V
_After closing the valves ₈ and opening the valves V ₂ , V ₃ , V ₆ and V ₇ , the regeneration of the desulfurization column 2A and the desulfurization treatment in the desulfurization column 2B are performed in the same manner as above. Thereafter, the regeneration and the desulfurization are alternately repeated.

In the anaerobic biogas desulfurization apparatus of the present invention, the following means can be further provided, and the desulfurization treatment and the regeneration treatment can be switched by automatic operation. (1) Providing a detecting means for detecting the concentration of hydrogen sulfide in the processing gas, detecting an increase in the concentration of hydrogen sulfide in the processing gas, detecting breakthrough of the desulfurization column during the desulfurization treatment, and controlling opening and closing of the valve. Means for automatically switching the desulfurization column from a desulfurization process to a regeneration process. (2) A means for controlling the opening and closing of the valve and automatically switching the introduction or stop of the introduction of the oxygen-containing gas into the desulfurization column so that the detected value of the temperature of the desulfurization column during the regeneration treatment falls within a predetermined range. (3) The detected value of the temperature of the desulfurization column during the regeneration treatment is compared with the outside air temperature, the temperature of the inflowing oxygen-containing gas, or the temperature inside the desulfurization device during the desulfurization treatment, and the temperature difference becomes equal to or less than a predetermined value. Means for controlling the opening and closing of the valve to stop the introduction of the oxygen-containing gas into the desulfurization column and automatically terminating the regeneration process. Further, a means for controlling the opening and closing of the valve and automatically restarting the introduction of the anaerobic biogas into the desulfurization column whose regeneration has been completed after the completion of the regeneration process. (4) The oxygen concentration in the regenerated exhaust gas discharged from the desulfurization column during the regeneration treatment is detected, and when the increase in the oxygen concentration is detected, the opening and closing of the valve is controlled to supply the oxygen-containing gas to the desulfurization column. Means to stop the introduction and automatically end the playback process. Further, a means for controlling the opening and closing of the valve and automatically restarting the introduction of the anaerobic biogas into the desulfurization column whose regeneration has been completed after the completion of the regeneration process.

When two or more such anaerobic biogas desulfurization devices are arranged in parallel, a means for automatically switching between a system for performing desulfurization and a system for performing regeneration is provided. In addition, the desulfurization treatment of anaerobic biogas can be continuously performed by automatic operation.

[0031]

The present invention will be described more specifically with reference to the following examples.

Example 1 A anaerobic biogas discharged from a UASB anaerobic wastewater treatment apparatus having a tank capacity of 200 L was subjected to a desulfurization treatment. The amount of the generated anaerobic biogas is 1,800 L / day on average, and the component composition is as shown in Table 1.

[0033]

[Table 1]

The anaerobic biogas was supplied to a desulfurization column (stainless steel, capacity 500 mL, diameter 4 cm, height 45 cm, commercially available desulfurizing agent having a particle size of 5 to 5 cm) using the apparatus shown in FIG.
20A iron oxide pellets) 2A or 2
B to remove hydrogen sulfide.

First, only the valves V ₂ and V ₇ were opened, and desulfurization was performed in the desulfurization column 2B. The hydrogen sulfide temperature of the processing gas was measured once a day using a detector tube. The concentration of hydrogen sulfide in the treated gas was initially below the detection limit, but after 50 days of treatment,
Since reached ppm see this as breakthrough desulfurization column 2B, the valve V _2, V ₇ is closed and subjected to continued desulfurization process by switching the processing in the desulfurization column 2A the valves V _1, V ₅ is opened .

In order to regenerate the desulfurization column 2B, the valves V ₄ and V ₈ were opened, and air was injected from the valve V ₄ . The air injection rate was 300 mL / min, and the temperature of the desulfurization column 2B was continuously measured with a thermometer (thermocouple sensor) 3B. When the indicated value reached 45 ° C., the valves V ₄ and V ₈ were automatically turned on. It was closed and the air supply was shut off. The desulfurization column 2B from which the air was shut off was allowed to cool naturally, and the temperature indicated value was 28.
Automatic control was performed so that air supply was resumed when the temperature dropped to ° C. The outside temperature was about 25 ° C. FIG. 2 shows the transition of the temperature of the desulfurization column 2B that is performing the regeneration treatment. The exhaust gas during the regeneration treatment was diluted and released from the draft to the atmosphere.

As shown in FIG. 2, after the introduction of air is started,
The temperature of the desulfurization column 2B rises, and after about 6 hours,
Since the temperature reached 5 ° C, the air was automatically shut off. Approximately 2 hours after the air was shut off, the column temperature reached 28 ° C., so the regeneration treatment was restarted. In the second regeneration process, the column temperature was 4
Before the temperature reached 5 ° C., the ascent was stopped, and the temperature eventually dropped to room temperature.

The anaerobic biogas flow path was switched to the regenerated desulfurization column 2B by opening and closing the valve.
When the anaerobic biogas was desulfurized in B, the concentration of hydrogen sulfide in the treated gas was below the detection limit, indicating that the regeneration treatment was effective. Then, the desulfurization column 2B
When the desulfurization treatment of the anaerobic biogas was continued continuously, the time required for the regenerated desulfurization column 2B to break through again was 46 days. Therefore, it was determined that the regenerated desulfurization column 2B had substantially the same hydrogen sulfide removal capacity as a new one.

During the desulfurization in the desulfurization column 2B, the regeneration of the desulfurization column 2A was performed in the same manner as described above, and the regeneration and the desulfurization were alternately repeated in the desulfurization columns 2A and 2B. The same desulfurization and regeneration treatment efficiency could be obtained.

[0040]

As described above in detail, according to the present invention, a used desulfurizing agent can be regenerated without being discarded and used repeatedly. Since the regeneration treatment is performed in the desulfurization device, it is not necessary to remove, transport, and refill the desulfurization agent for the regeneration treatment. Since the regeneration process is performed while controlling the temperature of the desulfurizing agent,
There is no danger of accident due to overheating or ignition. The end of the regeneration process can be known from the fact that the temperature rise of the desulfurizing agent has stopped, and the regeneration process can be automatically terminated. The end of the regeneration process can be known from the rise in the oxygen temperature of the regeneration exhaust gas, and the regeneration process can be automatically terminated. When two or more lines of desulfurization equipment are installed in parallel, regeneration can be performed in one line while desulfurization is performed in the other line. Can be. Thus, the anaerobic biogas desulfurization and the regeneration of the used desulfurizing agent can be performed industrially advantageously.

[Brief description of the drawings]

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

FIG. 2 is a graph showing transition of the temperature of a desulfurization column during a regeneration process in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 UASB device 2A, 2B Desulfurization column 3A, 3B Thermometer 4 Flow meter

Claims (4)

[Claims] 1. An anaerobic biogas desulfurization device filled with iron oxide pellets as a desulfurization agent, a temperature sensor for detecting the temperature in the desulfurization device, and oxidative regeneration of the desulfurization agent used in the desulfurization device. An anaerobic biogas comprising: means for introducing an oxygen-containing gas for controlling the flow rate of the oxygen-containing gas so that the temperature in the desulfurization apparatus does not exceed a predetermined value. Desulfurization equipment. 2. A method for regenerating a used desulfurization agent using the anaerobic biogas desulfurization apparatus according to claim 1, wherein the temperature in the desulfurization apparatus during the regeneration treatment, the outside air temperature, and the content of oxygen introduced. A method for regenerating a used desulfurizing agent, wherein the regenerating process is terminated when the temperature difference between the gas temperature and the temperature in the desulfurizing apparatus during the desulfurizing process is equal to or less than a predetermined value. 3. A method for regenerating a used desulfurizing agent by using the anaerobic biogas desulfurization apparatus according to claim 1, wherein an increase in the oxygen concentration of exhaust gas discharged from the desulfurization apparatus during the regeneration processing is detected. And regenerating the used desulfurizing agent by terminating the regeneration process. 4. An anaerobic biogas desulfurization apparatus according to claim 1 is installed in two or more lines in parallel, and at least one of them performs the anaerobic biogas desulfurization treatment and at least one of the remaining lines. A method for regenerating a used desulfurizing agent according to claim 2 or 3.