JP7463364B2 - Purified gas production method and purified gas production apparatus - Google Patents

Description

The present invention relates to a method and an apparatus for producing purified gas obtained by refining crude gas derived from waste.

There is a known technology for gasifying various types of waste, such as industrial waste and general waste, through pyrolysis (see Patent Document 1, etc.). According to this method, waste is pyrolyzed to obtain synthesis gas containing large amounts of carbon monoxide and hydrogen. Gases derived from waste, such as synthesis gas, can be used for various purposes. For example, attempts have been made to convert them into valuable products, such as ethanol, using microbial catalysts or metal catalysts.

Waste contains various components, and the synthetic gas obtained from waste also contains many impurities. Therefore, synthetic gas derived from waste needs to be purified by removing the impurities. The widely known method for removing impurities is to use a scrubber.
As a method for removing impurities using a scrubber, for example, a synthesis gas obtained from waste can be washed with a scrubber to perform a desulfurization process, recovering hydrogen sulfide contained in the raw gas as sulfur, and using the resulting purified gas as fuel gas by burning it in a gas utilization facility (for example, see Patent Document 2). Patent Document 2 discloses a purification method for acid washing in which a raw gas containing heavy metal components is washed with acidic washing water in a scrubber, thereby dissolving heavy metal components such as lead (Pb) and chlorine contained in the raw gas into the washing water.

JP 2007-45857 A JP 2006-110515 A

Acid washing is an effective method for purifying crude gas containing heavy metal components, but if the wash water contains acid-soluble heavy metal components, the acidity of the wash water decreases (pH increases), making it impossible to maintain the heavy metal removal capacity. In order to maintain the heavy metal removal capacity, it is necessary to maintain the acidity, and a pH adjuster must be added to maintain the acidity, which is costly.

The present invention has been made in consideration of the above-mentioned problems in the conventional art, and aims to provide a method and apparatus for producing purified gas that can maintain the acidity of the cleaning water and maintain its heavy metal removal capacity by dissolving carbon dioxide in the cleaning water during acid washing to remove heavy metal components from raw gas containing acid-soluble heavy metal components.

As a result of extensive research, the present inventors have found that the above problems can be solved by setting the concentration of dissolved carbon dioxide in cleaning water to a predetermined value or higher, and have completed the present invention as described below. That is, the present invention provides the following items [1] to [8].
[1] A method for producing a purified gas, comprising using a scrubber to remove at least a portion of heavy metal components from a raw gas derived from waste material, the heavy metal components being acid-soluble, to obtain a purified gas, wherein in the scrubber, wash water having at least carbon dioxide dissolved therein is brought into contact with the raw gas to remove at least a portion of the heavy metal components from the raw gas, and a concentration _D1 of dissolved carbon dioxide in the wash water is 0.72 L/kg or more.
[2] The method for producing a purified gas according to [1], wherein the relationship between the concentration _D1 of the dissolved carbon dioxide and the concentration _D2 of the heavy metal components contained in the crude gas satisfies the following formula (1):
7.5≦ _D1 / _D2 ≦21 (1)
[3] The method for producing a purified gas according to [1] or [2], wherein the temperature of the cleaning water is adjusted to be 0°C or higher and 10°C or lower.
[4] The method for producing a purified gas according to any one of [1] to [3], wherein the pH of the wash water is adjusted to 2 or more and 4 or less.
[5] The method for producing a purified gas according to any one of [1] to [4], wherein the wash water is used to dissolve carbon dioxide contained in the crude gas.
[6] The method for producing a purified gas according to any one of [1] to [5], wherein the crude gas is a synthesis gas.
[7] The gas treatment method according to any one of [1] to [6], wherein the heavy metal component contains lead.
[8] A refined gas production apparatus for obtaining a refined gas by removing at least a part of the heavy metal components from a raw gas derived from a waste material, the heavy metal components being soluble in acid, using a scrubber, wherein in the scrubber, wash water having at least carbon dioxide dissolved therein is brought into contact with the raw gas to remove at least a part of the heavy metal components from the raw gas, and a concentration _D1 of dissolved carbon dioxide in the wash water is 0.72 L/kg or more.

According to the present invention, in an acid washing process for removing heavy metal components from a crude gas containing acid-soluble heavy metal components, it is possible to provide a method and apparatus for producing purified gas that can maintain the acidity of the washing water by dissolving carbon dioxide in the washing water and thereby maintain the heavy metal removal capacity.

1 is a schematic diagram showing the overall configuration of a refined gas production apparatus according to the present invention. 1 is a schematic diagram showing details of a refined gas production apparatus according to a first embodiment of the present invention; FIG. 5 is a schematic diagram showing details of a refined gas production apparatus according to a second embodiment of the present invention. FIG. 11 is a schematic diagram showing details of a refined gas production apparatus according to a third embodiment of the present invention. FIG. 4 is a schematic diagram showing details of a refined gas production apparatus according to another embodiment of the present invention.

First Embodiment
Next, the present invention will be described using an embodiment.
1 shows a purified gas production apparatus according to a first embodiment of the present invention. The purified gas production apparatus 10 includes a crude gas production facility 11 and a scrubber 12. The crude gas production facility 11 is a facility for producing a crude gas G1 which is a waste-derived gas. The crude gas G1 produced in the crude gas production facility 11 is introduced into the scrubber 12. The scrubber 12 purifies the introduced crude gas G1 to obtain a purified gas G2.

The raw gas generation facility 11 is equipped with a device for burning and pyrolyzing waste, and is equipped with, for example, one or more of a combustion furnace, a pyrolysis furnace, a reforming furnace, a heating furnace, a melting furnace, a plasma gasification furnace, etc. The waste may be industrial waste or general waste such as household garbage, and is not particularly limited as long as it is a combustible material, such as tires, biomass, wood chips, plastic, paper, food waste, etc. The raw gas G1 is a waste-derived gas obtained by burning and pyrolyzing the waste in the raw gas generation facility 11.

As described above, the crude gas G1 is a gas derived from waste and thus contains carbon dioxide, and is preferably a synthetic gas. The synthetic gas constituting the crude gas G1 contains impurities such as acid-soluble heavy metal components as described below, and is therefore referred to as a "crude synthetic gas" here. The crude synthetic gas may be obtained by pyrolyzing waste in a pyrolysis furnace, for example, or may be obtained by pyrolyzing waste in a pyrolysis furnace and then further reducing carbon in a reforming furnace. In addition, degassing treatment may be performed in a heating furnace or the like before pyrolysis in the pyrolysis furnace.
The crude synthesis gas contains carbon monoxide and hydrogen, and usually also contains carbon dioxide. The synthesis gas may contain, for example, 10 to 45 vol% carbon monoxide, 10 to 50 vol% hydrogen, 2 to 40 vol% carbon dioxide, and may further contain about 5 to 67 vol% nitrogen, 0.5 to 20 vol% oxygen, and 5 to 40 vol% water.

In addition to the above gases, the crude gas G1 also contains acid-soluble heavy metal components. The heavy metal components contained in the crude gas G1 are substances that are soluble in acidic cleaning water and can form carbonates when they come into contact with cleaning water containing dissolved carbon dioxide. Specific examples of the heavy metal components include oxides of heavy metals such as lead, copper, chromium, zinc, manganese, iron, nickel, and cadmium.
The scrubber 12 can suitably perform acid washing of the raw gas G1 containing heavy metal components such as lead, copper, chromium, zinc, manganese, iron, nickel, and cadmium, and can particularly suitably perform acid washing of the raw gas G1 containing lead.

In the scrubber 12, the wash water is brought into contact with the crude gas G1, and at least a portion of the acid-soluble heavy metal components are removed from the crude gas G1. Here, the wash water used is wash water having at least carbon dioxide dissolved therein. By dissolving at least carbon dioxide in the wash water, the acid-soluble heavy metal components contained in the crude gas G1 can be removed, and the acid-soluble heavy metal components are efficiently removed from the crude gas G1.

The concentration _D1 of dissolved carbon dioxide in the cleaning water is characterized by being 0.72 L/kg or more. If the concentration _D1 is less than 0.72 L/kg, the heavy metal removal capacity is low and heavy metal components cannot be removed efficiently from the raw gas G1. From the viewpoint of improving the heavy metal removal capacity, the concentration _D1 of dissolved carbon dioxide in the cleaning water is preferably 1.0 L/kg or more, more preferably 1.1 L/kg or more, and even more preferably 1.2 L/kg or more, and the closer to saturated dissolved carbon dioxide, the better.
On the other hand, if the concentration _D1 of dissolved carbon dioxide in the wash water exceeds 2.0 L/kg, it corrodes the metal parts of the scrubber 12, making it difficult to stably operate the process of obtaining the purified gas G2. From this viewpoint, the concentration _D1 of dissolved carbon dioxide in the wash water is preferably 1.8 L/kg or less, more preferably 1.7 L/kg or less, and even more preferably 1.6 L/kg or less.
In this specification, the volume (L) of the concentration _D1 of dissolved carbon dioxide indicates the volume of carbon dioxide gas when the temperature is 20° C. and the pressure is 1 atm.

From the viewpoint of efficiently removing heavy metal components from the raw gas G1 and from the viewpoint of suppressing corrosion of the scrubber 12 and improving stable operability, it is preferable that the relationship between the concentration D ₁ (L/kg) of dissolved carbon dioxide and the concentration D ₂ (g/L) of heavy metal components contained in the raw gas G1 of the wash water satisfies the following formula (1).
7.5≦ _D1 / _D2 ≦21 (1)
From the viewpoint of efficiently removing heavy metal components from the raw gas, the wash water preferably has a D1/D2 ratio of 10.5 ≦ _D1 / _D2 , more preferably has a _D1 /D2 ratio of 11.4 ≦ D1/ _D2 , and further preferably has a _D1 /D2 ratio of 12.6 ≦ D1/ _D2 . From the viewpoint of suppressing corrosion of the scrubber 12 and improving stable operability, the wash water preferably has a _D1 / _D2 ratio of 19, more preferably has a _D1 / _D2 ratio of 18, and further preferably has a _D1 / _D2 ratio of 17.

The concentration _D2 of the heavy metal components contained in the crude gas G1 is preferably 0.01 g/L or more and 100 g/L or less, more preferably 0.02 g/L or more and 50 g/L or less, and even more preferably 0.05 g/L or more and 20 g/L or less. When the concentration _D2 of the heavy metal components contained in the crude gas G1 is within the above range, the heavy metal components contained in the crude gas G1 can be efficiently removed by the refined gas production apparatus of the present invention.
The concentration _D2 of the heavy metal components contained in the crude gas G1 is a concentration measured by an inductively coupled plasma mass spectrometer (ICP-MS) and ion chromatography (IC), etc.

From the viewpoint of efficiently removing heavy metal components from the crude gas G1, it is preferable to adjust the pH of the cleaning water to 2 or more and 4 or less, more preferably 2 or more and 3.5 or less, and even more preferably 2 or more and 3 or less.

In the present invention, the concentration _D1 of dissolved carbon dioxide and pH in the wash water refer to the concentration _D1 of dissolved carbon dioxide in the wash water when it comes into contact with the raw gas G1. Therefore, in this embodiment, the concentration of dissolved carbon dioxide refers to the concentration _D1 of dissolved carbon dioxide in the wash water immediately before coming into contact with the exhaust gas G1, that is, the wash water sprayed from a nozzle 15 described later. In addition, in an embodiment in which the wash water is brought into contact with the exhaust gas G1 in a stored state as in a third embodiment described later, the concentration D1 refers to the concentration of dissolved carbon dioxide in the stored wash water.
The concentration _D1 of dissolved carbon dioxide may be measured using a known dissolved carbon dioxide measuring device, and the pH may be measured using a pH meter.

The purified gas G2 purified by the scrubber 12 contains, for example, carbon dioxide and further carbon monoxide, and is converted into organic compounds such as ethanol in a reactor (not shown) etc. The purified gas G2 is preferably a synthetic gas, and is more preferably converted into organic compounds such as ethanol by either a gas-utilizing microorganism or a metal catalyst.
The purified gas G2 may be further purified by a dust removal device such as a bag filter, various adsorption filters such as an activated carbon filter, a denitration reaction tower, a desulfurization reaction tower, a PSA, a TSA, or other cleaning devices before being sent to the reactor (not shown). In addition, a moisture removal device for removing moisture contained in the gas after passing through the scrubber 12 may be provided.

The details of the scrubber 12 of this embodiment will be described in more detail below with reference to Figure 2. The scrubber 12 is a washing tower for washing the raw gas G1, and has a storage section 14 at its bottom and a nozzle 15 at its top. Wash water WS is stored in the storage section 14. The nozzle 15 sprays the wash water WS into the inside of the scrubber 12.

The scrubber 12 is connected to an inlet 13, a circulation path 16, a discharge path 20, etc. The inlet 13 is a path for introducing the raw gas G1 into the scrubber 12, and an inlet 13A of the inlet 13 is provided above the liquid level of the wash water WS stored inside the scrubber 12. The discharge path 20 is provided at the top of the scrubber 12, and the purified gas G2 obtained by purification in the scrubber 12 is discharged.

The scrubber 12 is further provided with a temperature control device 32, which can control the temperature of the wash water WS. The temperature control device 32 has a temperature measurement unit (not shown) and can measure the temperature of the wash water WS. The temperature measurement unit is not particularly limited as long as it can measure the temperature of the wash water WS, and for example, a thermocouple or the like can be used. The temperature control device 32 adjusts the temperature of the wash water WS based on the temperature of the wash water WS measured by the temperature measurement unit.
The temperature control device 32 is, for example, a device for adjusting the cleaning water WS stored in the storage section 14, and may be a jacket or the like that is provided around the storage section 14 and through which a medium flows. In this embodiment, the provision of the temperature control device 32 allows the temperature of the cleaning water WS to be maintained within a predetermined range, which will be described later.

The storage section 14 is provided with a stirring means such as a stirring blade, and the cleaning water WS stored in the storage section 14 may or may not be stirred by the stirring means.

The cleaning water WS stored in the storage section 14 is sent to the nozzle 15 provided at the top of the scrubber 12 via the circulation path 16. The circulation path 16 is provided with, for example, a pump 19, and the cleaning water WS is pressurized to the nozzle 15 by the pump 19. The cleaning water WS is then sprayed downward from the nozzle 15 inside the scrubber 12.

The crude gas G1 introduced into the scrubber 12 from the inlet 13A rises inside the scrubber 12 while coming into contact with the cleaning water WS sprayed from the nozzle 15, and is discharged as the refined gas G2 from the exhaust line 20. By coming into contact with the cleaning water WS, at least a part of the acid-soluble heavy metal components contained in the crude gas G1 is removed, and the crude gas G1 is discharged from the exhaust line 20 as the refined gas G2.
In this embodiment, as described above, the cleaning water WS that comes into contact with the crude gas G1 has a dissolved carbon dioxide concentration _D1 within a predetermined range, so that acid-soluble heavy metal components contained in the crude gas G1 are efficiently removed.
Inside the scrubber 12, a contact area is formed between the cleaning water stored in the storage section 14 and the nozzle 15, where the cleaning water WS sprayed from the nozzle 15 comes into contact with the crude gas G1. A porous body (not shown) or the like may be disposed in the contact area to increase the contact area between the cleaning water WS and the crude gas G1.

The cleaning water WS sprayed from the nozzle 15 falls to the storage section 14 while coming into contact with the crude gas G1, is stored in the storage section 14, and is used again as cleaning water WS. In addition, the acid-soluble heavy metal components contained in the crude gas G1 become heavy metal carbonates when they come into contact with carbon dioxide dissolved in the cleaning water WS, and are mixed into the cleaning water WS, thereby being removed from the crude gas G1. Heavy metal carbonates are generally insoluble in water, and are mixed into the cleaning water WS as solids.

The raw gas G1 is a gas derived from waste and contains a large amount of carbon dioxide, and therefore, when the cleaning water WS sprayed from the nozzle 15 comes into contact with the raw gas G1, carbon dioxide is dissolved in the cleaning water WS. Therefore, the concentration _D1 of dissolved carbon dioxide in the cleaning water WS can be increased or maintained. Therefore, even if the cleaning water WS comes into contact with an acid-soluble substance contained in the raw gas G1, the concentration _D1 of dissolved carbon dioxide can be prevented from decreasing.
Generally, the solubility of carbon dioxide in water increases with decreasing temperature. Therefore, in this embodiment, by lowering the temperature of the cleaning water WS, the solubility of carbon dioxide in water can be increased, and the concentration of dissolved carbon dioxide can be adjusted to the above-mentioned predetermined concentration _D1 . Specifically, the temperature of the cleaning water WS is preferably adjusted to 0° C. or higher and 10° C. or lower, more preferably adjusted to 2° C. or higher and 10° C. or lower, and even more preferably adjusted to 5° C. or higher and 10° C. or lower.
The carbon dioxide dissolved in the cleaning water WS may be composed only of carbon dioxide derived from the crude gas G1. However, at the start of operation, etc., the carbon dioxide derived from the crude gas G1 alone cannot sufficiently increase the concentration _D1 . Therefore, carbon dioxide may be dissolved in the water in advance.

In order to increase the concentration _D1 of dissolved carbon dioxide as described above and maintain it high, it is necessary to lower the temperature of the wash water WS not only when it contacts the raw gas G1 but also after the contact. This is to prevent carbon dioxide once dissolved from escaping from the wash water WS. Therefore, when the wash water WS is circulated and contacted with the exhaust gas G1 as in this embodiment, it is preferable to maintain the temperature of the wash water WS within the above temperature range before and after contact with the raw gas G1. Specifically, it is preferable to adjust both the temperature of the wash water WS sprayed from the nozzle 15 and the temperature of the wash water WS in the storage section 14 within the above temperature range. However, the temperature of the wash water WS is usually uniform in the system of the scrubber 12, and if the temperature in the storage section 14 is set within the above range, the temperature in the nozzle 15 will also be within the above range.

The temperature of the crude gas G1 introduced into the scrubber 12 is not particularly limited, but is preferably set to a certain temperature or below so that the temperature of the cleaning water WS is hardly increased by the crude gas G1. Specifically, the temperature of the crude gas G1 is preferably 80°C or below, more preferably 0 to 50°C, and even more preferably 0 to 30°C. The temperature of the crude gas G1 means the temperature of the crude gas G1 immediately before it comes into contact with the cleaning water WS, and may be measured at the inlet 13A of the introduction path 13.

It is preferable that the pressure inside the scrubber 12 is close to normal pressure. By keeping the pressure inside the scrubber 12 close to normal pressure, it is not necessary to use pressure-resistant equipment, and the equipment can be simplified. Note that pressure close to normal pressure is, for example, about 0.08 to 0.12 MPa in absolute pressure.

The cleaning water WS contaminated with acid-soluble heavy metal components is returned to the scrubber 12 after the contaminated acid-soluble heavy metal components are removed by a heavy metal removal device 50 provided in the scrubber 12. There are no particular limitations on the heavy metal removal device 50 as long as it can remove the acid-soluble heavy metal components contaminated in the cleaning water WS, and for example, a filtration device or the like can be used.

According to the purified gas production method and purified gas production apparatus of the first embodiment of the present invention, in acid washing to remove heavy metal components from raw gas containing acid-soluble heavy metal components, the acidity of the wash water is maintained by dissolving carbon dioxide in the wash water, and the heavy metal removal ability is maintained, so that highly accurate purified gas can be supplied.

Second Embodiment
Next, a second embodiment of the present invention will be described. In the following, a description of the second embodiment that overlaps with the first embodiment will be omitted, and only differences from the first embodiment will be described.
The purified gas production apparatus in the second embodiment further includes a concentration measuring device 31 that detects the concentration _D1 of dissolved carbon dioxide in the cleaning water WS, and a control unit 40 that controls the temperature control device 32 based on data of the detected concentration _D1 . The concentration measuring device 31 is not particularly limited as long as it can measure the concentration _D1 of dissolved carbon dioxide in the cleaning water WS, and for example, a dissolved carbon dioxide measuring device or the like can be adopted.

The control unit 40 receives data on the concentration _D1 of dissolved carbon dioxide in the cleaning water WS measured by the concentration measuring device 31, and judges whether the concentration _D1 of dissolved carbon dioxide is within the above-mentioned predetermined range. If the judgement result is within the predetermined range, data to maintain the current state is transmitted to the temperature control device 32. On the other hand, if the judgement result is outside the predetermined range, data on adjusting the temperature of the cleaning water WS is transmitted to the temperature control device 32. The temperature control device 32 controls the temperature of the cleaning water WS based on the transmitted data.
Specifically, when the concentration _D1 of dissolved carbon dioxide in the cleaning water WS falls below the lower limit of the above range, the temperature of the cleaning water WS is adjusted to be lowered, and when the concentration _D1 of dissolved carbon dioxide in the cleaning water WS exceeds the upper limit of the above range, the temperature of the cleaning water WS is adjusted to be higher.

From the viewpoint of efficiently removing heavy metal components, it is necessary to adjust the carbon dioxide concentration _D1 in the cleaning water WS when it contacts the raw gas G1 within the above range, but the concentration measuring device 31 does not necessarily need to measure the carbon dioxide concentration _D1 in the cleaning water WS when it contacts the raw gas G1, and it is preferable to measure the carbon dioxide concentration at a position which can be evaluated to be the same as the concentration _D1 . Therefore, for example, as shown in Figure 3, the concentration measuring device 31 may be disposed in the circulation path 16 to measure the concentration of dissolved carbon dioxide in the cleaning water WS circulating through the circulation path 16.

As described above, in this embodiment, the control unit 40 controls the temperature of the cleaning water WS, thereby controlling the concentration _D1 of dissolved carbon dioxide in the cleaning water WS measured by the concentration measuring device 31 to be within the above-mentioned predetermined range. Specifically, even if the concentration _D1 of dissolved carbon dioxide in the cleaning water WS measured by the concentration measuring device 31 fluctuates and falls outside the above-mentioned predetermined range, the control unit 40 can control the temperature of the cleaning water WS to control the concentration _D1 of dissolved carbon dioxide to be within the above-mentioned predetermined range.
Furthermore, in this embodiment, a heavy metal component concentration measuring device (not shown) may be provided to measure the concentration _D2 of heavy metal components contained in the raw gas G1. By providing the heavy metal component concentration measuring device, it becomes easy to adjust the concentration _D1 of dissolved carbon dioxide in the cleaning water WS so that _D1 / _D2 falls within the above range. The concentration _D2 of heavy metal components may be measured, for example, by an inductively coupled plasma mass spectrometer (ICP-MS) and ion chromatography (IC).

Third Embodiment
Next, a third embodiment of the present invention will be described. In the following, a description of the third embodiment that overlaps with the first embodiment will be omitted, and only differences from the first embodiment will be described.
In the scrubber 12 of the first embodiment described above, the wash water WS stored in the storage section 12 is circulated and sprayed from the nozzles 15 at the top of the scrubber 12, but in the scrubber 62 of the present embodiment, the nozzles are omitted, and the wash water WS stored in the storage section 64 is not circulated but remains stored in the storage section 64. And, the inlet 63A of the introduction path 63 is arranged below the liquid level of the wash water WS stored in the storage section 64.
Therefore, the crude gas G1 introduced from the introduction path 63 is introduced into the cleaning water WS stored in the storage section 64. As a result, the crude gas G1 passes through the cleaning water WS stored in the storage section 64, and thereby the crude gas G1 is brought into contact with the cleaning water WS.
As in the first embodiment, in the third embodiment, the cleaning water WS stored in the storage section 64 may be agitated by an agitator or the like.

The crude gas G1 passes through the cleaning water WS in the storage section 64, whereby at least a part of the acid-soluble heavy metal components contained in the crude gas G1 is removed, and the crude gas G1 from which the acid-soluble heavy metal components have been removed is discharged as a purified gas G2 from the outlet 20. As described above, the crude gas G1 contains a large amount of carbon dioxide, and the cleaning water WS dissolves carbon dioxide when it comes into contact with the crude gas G1, increasing the concentration _D1 of dissolved carbon dioxide in the cleaning water WS. Furthermore, even if the cleaning water WS comes into contact with an acid-soluble substance contained in the crude gas G1, the concentration _D1 of dissolved carbon dioxide can be prevented from decreasing. Here, in this embodiment as well, by lowering the temperature of the cleaning water WS in the storage section 64, the solubility of carbon dioxide in water can be increased, and the concentration _D1 of dissolved carbon dioxide in the cleaning water can be adjusted to the above-mentioned predetermined range. The temperature of the cleaning water WS in the storage section 64 may be set to the temperature range as described above, and is preferably adjusted to be between 0°C and 10°C, more preferably between 2°C and 10°C, and even more preferably between 5°C and 10°C.
The temperature of the cleaning water WS in the storage section 64 can be controlled by a temperature control device 72. The temperature control device 72 can be, for example, a jacket provided around the storage section 64 and through which a medium flows.

The scrubber 62 is provided with a temperature control device 72, which can control the temperature of the cleaning water WS stored in the storage section 64. The temperature control device 72 has a temperature measurement section (not shown) and can measure the temperature of the cleaning water WS. The temperature control device 72 adjusts the temperature of the cleaning water WS stored in the storage section 64 based on the temperature of the cleaning water WS measured by the temperature measurement section. Details of the temperature measurement section and the temperature control device are similar to those of the first and second embodiments described above, so their description will be omitted.

According to the method for producing a purified gas and the apparatus for producing a purified gas according to the third embodiment of the present invention, it is possible to obtain effects equivalent to those of the method for producing a purified gas and the apparatus for producing a purified gas according to the first embodiment.
In the third embodiment, as in the second embodiment described above, a control unit and a concentration measuring device may be provided, and the concentration _D1 of dissolved carbon dioxide in the cleaning water WS may be adjusted to within the above-mentioned predetermined range by control of the control unit.

Other Embodiments
For example, in the first and second embodiments, the temperature control device 32 is shown as a jacket provided around the storage section 14, but as shown in Fig. 5, it may be provided in the circulation path 16. By providing the temperature control device 32 in the circulation path 16, the temperature of the cleaning water WS immediately before contacting the raw gas G1 can be adjusted more accurately. Note that the temperature control device 32 may be provided both around the storage section 14 and in the circulation path 16, and by using them in combination, the temperature of the cleaning water WS can be adjusted more accurately.

In the first and second embodiments, the temperature of the wash water WS is controlled to control the concentration _D1 of dissolved carbon dioxide in the wash water WS to be within the above-mentioned predetermined range. However, since the concentration _D1 of dissolved carbon dioxide in the wash water WS depends not only on the temperature of the wash water but also on the pressure in the scrubber 12, the concentration D1 can be controlled by controlling the pressure in the scrubber 12 instead of controlling the temperature of the wash water WS. The pressure in the scrubber 12 can be controlled by a known pressure applying means, for example, a means of providing a compressor (not shown) in the introduction path 13. The compressor is operated by a power source such as a motor, and can increase the pressure in the scrubber 12 by compressing the raw gas G1 introduced into the scrubber 12 from the introduction port 13A.
As a specific adjustment when the concentration _D1 of dissolved carbon dioxide in the wash water WS falls outside the above range, when the concentration _D1 of dissolved carbon dioxide in the wash water WS falls below the lower limit of the above range, the pressure in the scrubber 12 is adjusted to be increased, and when the concentration _D1 of dissolved carbon dioxide in the wash water WS exceeds the upper limit of the above range, the pressure in the scrubber 12 is adjusted to be decreased.
From the viewpoint of maintaining the concentration _D1 of dissolved carbon dioxide in the cleaning water WS, the pressure inside the scrubber 12 is preferably adjusted to 0.01 to 1 MPa, more preferably adjusted to 0.02 to 0.5 MPa, and even more preferably adjusted to 0.05 to 0.3 MPa.

In addition, as means for controlling the concentration _D1 of dissolved carbon dioxide in the wash water WS to be within the above-mentioned predetermined range, controlling the temperature of the wash water WS and controlling the pressure inside the scrubber have been shown, but these may be adopted alone or both may be adopted together.
In the case where both controlling the temperature of the wash water WS and controlling the pressure inside the scrubber are adopted, when the pressure inside the scrubber is controlled to a high pressure of, for example, about 0.05 to 0.20 MPa in absolute pressure, it is preferable to adjust the temperature of the wash water WS to a range of 0°C to 10°C, more preferably to a range of 2°C to 10°C, and even more preferably to a range of 5°C to 10°C.

In the first to third embodiments, the acidity of the cleaning water WS is maintained and the heavy metal removal capability is maintained by dissolving carbon dioxide, but in addition to dissolving carbon dioxide, other acidic substances such as hydrogen chloride, sulfuric acid, and nitric acid may be dissolved in the cleaning water WS. By dissolving other acidic substances in the cleaning water WS, it becomes even easier to maintain the capability of removing heavy metal components from the raw gas G1.

10: Refined gas production device 11: Raw gas production equipment 12, 62: Scrubber 13, 63: Inlet 13A, 63A: Inlet 14, 64: Storage section 16: Circulation path 19: Pump 20: Discharge path 31: Concentration measuring device 32: Temperature control device 40: Control section 50: Heavy metal removal device

Claims (7)

1. A method for producing a purified gas, comprising the steps of: removing at least a portion of a raw gas derived from a waste material, the raw gas containing acid-soluble heavy metal components, using a scrubber to obtain a purified gas, the method comprising the steps of:
In the scrubber, wash water having at least carbon dioxide dissolved therein is contacted with the crude gas to remove at least a portion of the heavy metal components from the crude gas;
The concentration _D1 of dissolved carbon dioxide in the cleaning water is 0.72 L/kg or more;
A method for producing a purified gas, wherein a relationship between a concentration _D1 of the dissolved carbon dioxide and a concentration _D2 of the heavy metal components contained in the crude gas when the crude gas contacts with the wash water satisfies the following formula (1) :
7.5≦D1 _/ D2 _≦ 21 (1) The method for producing a purified gas according to claim 1 , wherein the temperature of the wash water is adjusted to be 0° C. or higher and 10° C. or lower. The method for producing a purified gas according to claim 1 or 2 , wherein a pH of the wash water is adjusted to 2 or more and 4 or less. 4. The method for producing a refined gas according to claim 1, wherein the wash water dissolves carbon dioxide contained in the crude gas. The method for producing a refined gas according to any one of claims 1 to 4 , wherein the crude gas is a crude synthesis gas derived from a waste material . The method for producing a refined gas according to any one of claims 1 to 5 , wherein the heavy metal components include lead. 1. A refined gas production apparatus for obtaining a refined gas by removing at least a portion of heavy metal components from a raw gas derived from waste, the heavy metal components being soluble in acid, using a scrubber, the refined gas production apparatus comprising:
In the scrubber, wash water having at least carbon dioxide dissolved therein is contacted with the crude gas to remove at least a portion of the heavy metal components from the crude gas;
The concentration _D1 of dissolved carbon dioxide in the cleaning water is 0.72 L/kg or more;
A refined gas production apparatus , wherein the relationship between the concentration D1 of the dissolved carbon dioxide when the crude gas contacts the wash water and the concentration D2 of the heavy metal components contained in the crude gas satisfies the following formula ₍ 1 ₎ :
7.5≦D1 _/ D2 _≦ 21 (1)

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