Organic substance manufacturing method and organic substance manufacturing device

Abstract

To provide a method and apparatus for producing organic substances that can efficiently cool synthesis gas and convert the synthesis gas into organic substances with high conversion efficiency using a microbial catalyst.SOLUTION: A method for producing organic substances includes the steps of: cooling a synthesis gas G1 discharged from a gasification apparatus 2 by passing it through a heat exchanger 20; passing the synthesis gas G1 cooled in the heat exchanger 20 through a gas cooling tower 21 and cooling it with water sprayed inside the gas cooling tower 21; and contacting the synthesis gas G2 that has passed through at least the heat exchanger 20 and the gas cooling tower 21 with a microbial catalyst to produce organic substances.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing an organic substance using a synthesis gas as a raw material, and an organic substance production apparatus for producing an organic substance using a synthesis gas as a raw material. [Background technology]

[0002] A widely known technology involves pyrolyzing various types of waste, such as industrial waste and municipal waste, in a gasification furnace to generate gas, which is then reformed in a reformer to obtain synthesis gas. The synthesis gas obtained can be burned as is and used for power generation, or, if necessary, heat can be recovered in a boiler or the like and then used for power generation. Furthermore, in recent years, attempts have been made to utilize synthesis gas as a raw material for chemical synthesis, for example, by converting it into organic substances such as ethanol using a microbial catalyst (see, for example, Patent Document 1).

[0003] The synthesis gas obtained in the gasifier and reformer contains a large amount of impurities such as tar, making it difficult to use it directly for power generation or chemical synthesis. Therefore, gas purification is generally performed. It is known that synthesis gas is appropriately cooled during gas purification. A commonly used method for cooling synthesis gas is to spray water into the gas flow and use the heat of evaporation of the water to cool the synthesis gas. However, the temperature of the synthesis gas obtained in the gasifier and reformer is high, and cooling the synthesis gas by spraying water requires a large amount of water, resulting in the generation of a large amount of wastewater. Therefore, methods that include means other than spraying water have been proposed as methods for cooling synthesis gas (see, for example, Patent Documents 2 to 4). Patent Document 2 discloses that biomass is gasified at high temperature and atmospheric pressure, the gasified synthesis gas is introduced from a gas furnace through a water-cooled pipe into a quenching tower, and the crude synthesis gas is cooled in the quenching tower with spray water. Patent Document 3 discloses a method for cooling synthesis gas produced by gasification using an indirect heat exchanger, a tar removal process, a cooling process using a tar removal device, and a cooling process using water spray atomization in a spray tower. Patent Document 4 discloses a method including a cooling step of cooling a synthesis gas in a first heat exchanger and spraying cooling water onto the synthesis gas cooled in the first heat exchanger in a spray tower. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 037710 [Patent Document 2] Special Publication No. 2015-510522 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-298825 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-227450 Summary of the Invention [Problem to be solved by the invention]

[0005] When using synthesis gas as a raw material for organic synthesis, for example, the temperature must be strictly controlled. For example, when converting synthesis gas into organic substances such as ethanol using a microbial catalyst, the synthesis gas must be cooled to a temperature of 40°C or less to prevent the microbial catalyst from dying.

[0006] However, when using synthesis gas for power generation, etc., strict temperature control is not required. Therefore, even if the conventional synthesis gas purification methods described in Patent Documents 2 to 4 are directly applied to the case where a microbial catalyst is used, it is difficult to synthesize organic substances with high conversion efficiency. Furthermore, conventional methods for cooling synthesis gas generally involve blowing in nitrogen or air, but when using a microbial catalyst, the inclusion of nitrogen or air in the synthesis gas reduces the conversion efficiency of organic substances.

[0007] Therefore, an object of the present invention is to provide a method and apparatus for producing organic substances that can efficiently cool synthesis gas and convert the synthesis gas into organic substances with high conversion efficiency using a microbial catalyst. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by cooling synthesis gas using a heat exchanger, cooling the synthesis gas cooled by the heat exchanger with water sprayed inside a gas cooling tower, and bringing the cooled synthesis gas into contact with a microbial catalyst to produce organic substances, and have completed the present invention as described below. That is, the present invention provides the following [1] to

[18] . [1] A method for producing organic substances, comprising the steps of: cooling synthesis gas discharged from a gasification system by passing it through a heat exchanger; passing the synthesis gas cooled by the heat exchanger through a gas cooling tower and cooling it with water sprayed inside the gas cooling tower; and contacting the synthesis gas that has passed through at least the heat exchanger and the gas cooling tower with a microbial catalyst to produce organic substances. [2] The method for producing an organic substance according to [1], wherein the temperature of the synthesis gas discharged from the gasification apparatus is 900°C or higher. [3] The method for producing an organic substance according to [1] or [2], wherein the synthesis gas is cooled to a temperature of 200°C or higher and 300°C or lower in the heat exchanger. [4] The method for producing an organic substance according to any one of [1] to [3], further comprising a step of passing the synthesis gas cooled in the gas cooling tower through a filter-type dust collector, in which the synthesis gas that has passed through at least the heat exchanger, the gas cooling tower, and the filter-type dust collector is brought into contact with a microbial catalyst to produce an organic substance. [5] The method for producing an organic substance according to any one of [1] to [4], further comprising a step of passing the synthesis gas cooled in the gas cooling tower through a water scrubber, in which the synthesis gas that has passed through at least the heat exchanger, the gas cooling tower, and the water scrubber is brought into contact with a microbial catalyst to produce an organic substance. [6] The method for producing an organic substance according to [5], wherein the synthesis gas that has passed through the heat exchanger, the gas cooling tower, the filter-type dust collector, and the water scrubber in this order is brought into contact with a microbial catalyst to produce an organic substance. [7] The method for producing an organic substance according to [5] or [6], wherein the synthesis gas is cooled to 40°C or less in the water scrubber. [8] The method for producing an organic substance according to any one of [1] to [7], further comprising a step of distilling the organic substance, in which thermal energy obtained from the synthesis gas by the heat exchanger is used for the distillation. [9] The method for producing an organic substance according to any one of [1] to [8], wherein the organic substance contains ethanol.

[10] An organic substance production apparatus comprising: a gasification apparatus for producing synthesis gas; a heat exchanger through which synthesis gas discharged from the gasification apparatus is passed to cool it; a gas cooling tower through which synthesis gas cooled in the heat exchanger is passed to cool it by spraying water; and an organic substance production unit that produces organic substances by bringing synthesis gas that has passed through at least the heat exchanger and the gas cooling tower into contact with a microbial catalyst.

[11] The organic substance production apparatus according to

[10] , wherein the temperature of the synthesis gas discharged from the gasification apparatus is 900°C or higher.

[12] The organic substance production apparatus according to

[10] or

[11] , wherein the synthesis gas is cooled to a temperature of 200°C or higher and 300°C or lower in the heat exchanger.

[13] An organic substance production apparatus according to any one of

[10] to

[12] , further comprising a filter-type dust collector arranged downstream of the gas cooling tower and through which the synthesis gas cooled by the gas cooling tower passes, wherein the organic substance production unit produces organic substances by bringing the synthesis gas that has passed through at least the heat exchanger, the gas cooling tower, and the filter-type dust collector into contact with the microbial catalyst.

[14] An organic substance production apparatus according to any one of

[10] to

[13] , further comprising a water scrubber disposed downstream of the gas cooling tower and through which the synthesis gas cooled by the gas cooling tower passes, wherein the organic substance production unit produces organic substances by bringing the synthesis gas that has passed through at least the heat exchanger, the gas cooling tower, and the water scrubber into contact with the microbial catalyst.

[15] The organic substance production apparatus described in

[14] , wherein the organic substance production unit produces organic substances by contacting the synthesis gas, which has passed through the heat exchanger, the gas cooling tower, the filtration type dust collector, and the water scrubber in this order, with the microbial catalyst.

[16] The organic substance production apparatus according to

[14] or

[15] , wherein the synthesis gas is cooled to 40°C or less in the water scrubber.

[17] The organic substance manufacturing apparatus according to any one of

[10] to

[16] , further comprising a distillation apparatus for distilling the organic substance, wherein the distillation apparatus utilizes thermal energy obtained from the synthesis gas by the heat exchanger for distillation.

[18] The organic substance manufacturing apparatus according to any one of

[10] to

[17] , wherein the organic substance contains ethanol. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method and an apparatus for producing an organic substance that can efficiently cool synthesis gas and convert the synthesis gas into an organic substance with high conversion efficiency using a microbial catalyst. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing the overall configuration of an organic substance manufacturing apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described using embodiments with reference to the drawings. 1 shows an organic substance manufacturing apparatus according to an embodiment of the present invention. Hereinafter, the organic substance manufacturing apparatus and the organic substance manufacturing method according to the embodiment of the present invention will be described in detail with reference to the embodiment.

[0012] The organic substance production apparatus 1 comprises a gasification apparatus 2 that gasifies waste to produce a synthesis gas G1, a processing unit 3 that performs processing including at least a purification process on the synthesis gas G1 discharged from the gasification apparatus 2, and an organic substance production section 30 that brings the synthesis gas obtained by processing in the processing unit 3 (hereinafter also referred to as "purified synthesis gas G2") into contact with a microbial catalyst to produce organic substances.

[0013] (Gasification equipment) The waste to be gasified in the gasification system 2 may be industrial waste such as industrial solid waste, or may be general waste such as municipal solid waste (MSW), including combustible materials such as plastic waste, food waste, discarded tires, biomass waste, food waste, building materials, wood, wood chips, fiber, paper, etc. Among these, municipal solid waste (MSW) is preferred.

[0014] The gasification system 2 includes a gasification furnace 10 and a reformer 11. The gasification furnace 10 is not particularly limited, but examples include a kiln gasification furnace, a fixed-bed gasification furnace, and a fluidized-bed gasification furnace. In addition to the waste, oxygen or air, and, if necessary, steam, are fed into the gasification furnace 10. The gasification furnace 10 heats the waste to, for example, 500 to 700°C, thereby pyrolyzing it and gasifying it by appropriately partial oxidation. The pyrolysis gas contains not only carbon monoxide and hydrogen, but also gaseous tar, powdered char, and the like. The pyrolysis gas is supplied to the reformer 11. Note that solid matter and the like generated as incombustible matter in the gasification furnace 10 are appropriately recovered.

[0015] In the reformer 11, the pyrolysis gas obtained in the gasification apparatus 2 is reformed to obtain a synthesis gas G1. In the reformer 11, the content of at least one of hydrogen and carbon monoxide in the pyrolysis gas increases, and the pyrolysis gas is discharged as a synthesis gas G1. In the reformer 11, for example, tar, char, etc. contained in the pyrolysis gas are reformed into hydrogen, carbon monoxide, etc. The temperature of the synthesis gas G1 in the reformer 11 is not particularly limited, but is, for example, 900° C. or higher, preferably 900° C. or higher and 1,300° C. or lower, and more preferably 1,000° C. or higher and 1,200° C. By keeping the temperature in the reformer 11 within the above range, synthesis gas G1 with high carbon monoxide and hydrogen contents is more likely to be obtained.

[0016] The temperature of the synthesis gas G1 discharged from the reformer 11 (i.e., the gasification apparatus 2) is similar to the temperature of the synthesis gas G1, for example, 900°C or higher, preferably 900°C or higher and 1,300°C or lower, and more preferably 1,000°C or higher and 1,200°C or lower. The synthesis gas G1 discharged from the reformer 11 (i.e., the gasifier 2) contains carbon monoxide and hydrogen. The synthesis gas G1 contains, for example, 0.1% to 80% by volume of carbon monoxide and 0.1% to 80% by volume of hydrogen. The carbon monoxide concentration in the synthesis gas G1 is preferably 10% by volume or more and 70% by volume or less, more preferably 20% by volume or more and 55% by volume or less. The hydrogen concentration in the synthesis gas G1 is preferably 10% by volume or more and 70% by volume or less, more preferably 20% by volume or more and 55% by volume or less.

[0017] The synthesis gas G1 may contain carbon dioxide, nitrogen, oxygen, and the like in addition to hydrogen and carbon monoxide. The carbon dioxide concentration in the synthesis gas G1 is not particularly limited, but is preferably 0.1% by volume or more and 40% by volume or less, and more preferably 0.3% by volume or more and 30% by volume or less. It is particularly preferable to lower the carbon dioxide concentration when ethanol is produced using a microbial catalyst, and from this perspective, the carbon dioxide concentration is more preferably 0.5% by volume or more and 25% by volume or less. The nitrogen concentration in the synthesis gas G1 is usually 40% by volume or less, and preferably 1% by volume or more and 20% by volume or less. The oxygen concentration in the synthesis gas G1 is usually 5% by volume or less, and preferably 1% by volume or less. The lower the oxygen concentration, the better, and it is sufficient if it is 0% by volume or more. However, oxygen is generally inevitably contained in many cases, and the oxygen concentration is practically 0.01% by volume or more.

[0018] The concentrations of carbon monoxide, carbon dioxide, hydrogen, nitrogen, and oxygen in the synthesis gas G1 can be kept within a predetermined range by appropriately changing combustion conditions such as the type of waste, the temperatures of the gasifier 10 and the reformer 11, and the oxygen concentration of the feed gas supplied to the gasifier 11. For example, if you want to change the carbon monoxide or hydrogen concentration, you can change the waste to one with a high ratio of hydrocarbons (carbon and hydrogen), such as waste plastic, or if you want to lower the nitrogen concentration, you can supply gas with a high oxygen concentration to the gasifier 10. Furthermore, the synthesis gas G1 may be adjusted in concentration as appropriate for each of the components carbon monoxide, carbon dioxide, hydrogen, and nitrogen by adding at least one of these components to the synthesis gas G1. The volume percentage of each substance in the synthesis gas G1 mentioned above refers to the volume percentage of each substance in the synthesis gas G1 discharged from the gasification apparatus 2.

[0019] In the above explanation, the gasification apparatus 2 has been described as having a gasification furnace 10 and a reformer furnace 11, but the configuration of the gasification apparatus 2 is not limited to this and may be an apparatus in which the gasification furnace and the reformer furnace are integrated, or may be any type of gasification apparatus as long as it is capable of producing synthesis gas G1.

[0020] (Processing Unit) 1, the treatment unit 3 in this embodiment includes at least a heat exchanger 20 and a gas cooling tower 21. The treatment unit 3 further includes a filter-type dust collector 22 downstream of the gas cooling tower 21. The treatment unit 3 further includes a water scrubber 23 downstream of the gas cooling tower 21. In this specification, the term "rear stage" refers to the rear stage along the supply flow of the synthesis gas G1. The term "early stage" refers to the early stage along the supply flow of the synthesis gas G1. The supply flow of the synthesis gas G1 refers to the flow of the synthesis gas G1 from the time the synthesis gas G1 is discharged from the gasification apparatus 2 until it is introduced into the organic matter generation section 30.

[0021] <Heat exchanger> The synthesis gas G1 discharged from the gasification apparatus 2 passes through the heat exchanger 20. The heat exchanger 20 is a device that cools the synthesis gas G1 using a heat medium. The heat exchanger 20 cools the synthesis gas G1 by transferring the thermal energy of the synthesis gas G1 to the heat medium. A boiler is preferably used as the heat exchanger 20. A boiler is a device that circulates water as a heat medium inside and heats the circulating water with the thermal energy of the synthesis gas G1 to produce steam. When a boiler is used as the heat exchanger 20, it becomes possible to easily heat other devices using the steam generated in the boiler, and the thermal energy of the synthesis gas G1 can be easily reused.

[0022] However, the heat exchanger 20 can be configured in any manner other than a boiler as long as it transfers thermal energy from the synthesis gas G1 to the heat transfer medium. However, a partition type in which the synthesis gas G1 and the heat transfer medium do not come into direct contact is preferred. The heat transfer medium may be either a gas or a liquid, or may be one that undergoes a phase change between gas and liquid. Furthermore, the heat transfer medium may transfer thermal energy from the synthesis gas G1 while passing through a flow path of any shape, such as a tubular or plate-shaped flow path.

[0023] As described above, the synthesis gas G1 discharged from the gasification apparatus 2 reaches a high temperature of, for example, 900°C or higher. Therefore, by being cooled by the heat exchanger 20, the synthesis gas G1 is supplied to the gas cooling tower 21 at a relatively low temperature, and excessive cooling in the gas cooling tower 21 can be prevented. This makes it possible to reduce the amount of water sprayed onto the synthesis gas G1 in the gas cooling tower 21, and furthermore, it becomes unnecessary to supply the synthesis gas G1, which has a high water content, to the filter-type dust collector 22 and the water scrubber 23. This makes it possible to suppress the amount of water moving from the gas cooling tower 21 to the water scrubber 23, and also makes it possible to prevent excessive coagulation of water in the filter-type dust collector 22.

[0024] As described above, the heat exchanger 20 cools the synthesis gas supplied at a high temperature, for example, 900°C or higher, to a temperature of, for example, 200°C to 300°C, preferably 240°C to 280°C, and supplies the cooled synthesis gas to the gas cooling tower 21. By cooling the synthesis gas G1 to 200°C or higher, it is possible to prevent impurities from being precipitated, and by setting the temperature to 240°C or higher, it is possible to effectively prevent tar from being precipitated. When waste is gasified, the synthesis gas G1 contains a large amount of tar, but by preventing tar from being precipitated, it is possible to prevent clogging of the heat exchanger 20 by tar. Furthermore, by setting the temperature to 300°C or lower, it is not necessary to excessively cool the synthesis gas G1 in the gas cooling tower 21.

[0025] <Gas Cooling Tower> The gas cooling tower 21 is a facility that cools the gas (synthesis gas G1) passing through it by spraying water. The gas cooling tower 21 has one or more water spray ports 24 on its inner circumferential surface for spraying water onto the synthesis gas G1. Preferably, two or more water spray ports 24 are provided, and more preferably, the two or more water spray ports 24 are provided at different height positions in the cooling tower 21. By providing multiple water spray ports 24 and positioning them at different height positions, the synthesis gas G1 can be cooled sufficiently and efficiently by water spray.

[0026] The synthesis gas G1 is introduced into the gas cooling tower 21 preferably from its upper side, and the synthesis gas G1 is passed through the interior of the gas cooling tower 21 so as to form a downward current, and is cooled by water sprayed from the water spray nozzles 24 while passing through the interior of the gas cooling tower 21. In this case, the synthesis gas G1 is preferably discharged from the lower side of the gas cooling tower 21.

[0027] The synthesis gas G1 introduced into the gas cooling tower 21 has a temperature sufficiently higher than 100°C, while the water sprayed from the water spray nozzle 24 is lower than 100°C. Therefore, the synthesis gas G1 is cooled by this temperature difference and also by the heat of vaporization when the water sprayed from the water spray nozzle 24 vaporizes. It is preferable that some of the vaporized water is mixed into the synthesis gas G1 as water vapor. Note that the water sprayed from the water spray nozzle 24 may be partially or completely vaporized when sprayed.

[0028] In the gas cooling tower 21, the synthesis gas G1 is preferably cooled to a temperature of 100°C or higher and 200°C or lower, and is discharged to the outside of the gas cooling tower 21 in the above temperature range. By cooling the synthesis gas G1 to 200°C or lower, the synthesis gas G1 can be purified in the filter-type dust collector 22, which will be described later, without damaging the filter-type dust collector 22 or reducing the dust collection performance. Furthermore, by setting the temperature to 100°C or higher, most of the sprayed water is vaporized and mixed into the synthesis gas G1. Therefore, in the gas cooling tower 21, a large amount of sprayed water is not discharged, and therefore there is no need to install large-scale drainage equipment in the gas cooling tower 21.

[0029] However, a portion of the water sprayed into the gas cooling tower 21 may fall as a liquid below the gas cooling tower 21 and be collected. Furthermore, impurities in the synthesis gas G1, such as char and tar, may also fall below upon colliding with the sprayed water and be collected.

[0030] In the gas cooling tower 21, the synthesis gas G1 is preferably cooled to a temperature of 120°C or higher and 180°C or lower, and even more preferably 130°C or higher and 170°C or lower, and is then cooled to these temperatures and discharged to the outside. Cooling the synthesis gas G1 to 120°C or higher can prevent a large amount of water mixed into the synthesis gas G1 from liquefying in the gas cooling tower 21 and further in the filter dust collector 22 described below. Furthermore, setting the temperature to 180°C or lower makes it even easier to avoid damage to and deterioration of the filter dust collector 22.

[0031] <Filter-type dust collector> The synthesis gas G1 cooled in the gas cooling tower 21 passes through a filter-type dust collector 22. A so-called bag filter can be used as the filter-type dust collector 22, and the filter-type dust collector 22 includes a casing and a filter medium housed inside the casing. The filter medium is not particularly limited, but examples of the filter medium include woven fabric or felt made of glass fiber or PTFE fiber. The synthesis gas G1 contains a large amount of solid impurities such as tar and char, but the solid impurities are removed by passing through the filter-type dust collector 22. Removing the solid impurities can prevent the solid impurities from clogging the devices downstream of the filter-type dust collector 22. For example, in the organic substance production unit 30, gas is generally blown into the reactor through a sparger, but clogging of the sparger with solid impurities can be prevented. Furthermore, removing the solid impurities makes it easier to increase the activity of the microbial catalyst in the organic substance production unit 30 and also prevents the microbial catalyst from dying due to the influence of impurities, allowing organic substances to be synthesized with high conversion efficiency. In this specification, "removal" means reducing the concentration of the target substance in the gas by removing at least a portion of the target substance from the synthesis gas, and is not limited to completely removing the target substance.

[0032] As described above, the synthesis gas G1 is cooled in the gas cooling tower 21, and therefore the temperature of the synthesis gas G1 when passing through the filter-type dust collector 22 is preferably 100°C or higher and 200°C or lower, more preferably 120°C or higher and 180°C or lower, and even more preferably 130°C or higher and 170°C or lower. This prevents the filter-type dust collector 22 from being damaged by the high-temperature synthesis gas G1 or from having its filtering performance reduced. Furthermore, it is also possible to prevent a large amount of the synthesis gas G1 contained in the synthesis gas G1 from being liquefied in the filter-type dust collector 22.

[0033] <Water Scrubber> The synthesis gas G1 cooled in the gas cooling tower 21 passes through the water scrubber 23. In this embodiment, the synthesis gas G1 cooled in the gas cooling tower 21 and discharged from the filter-type dust collector 22 passes through the water scrubber 23, which is arranged downstream of the filter-type dust collector 22. The synthesis gas G1 contains various impurities in addition to the solid impurities described above, including water-soluble impurities. Examples of water-soluble impurities include acid gases such as hydrogen sulfide, hydrogen chloride, and hydrocyanic acid, basic gases such as ammonia, and oxides such as NOx and SOx. These water-soluble impurities are removed by passing through the water scrubber 23. The synthesis gas G1 also contains oily impurities such as BTEX (benzene, toluene, ethylbenzene, xylene), naphthalene, 1-naphthol, and 2-naphthol, but these may also be removed appropriately in the water scrubber 23, and solid impurities that could not be collected in the filter dust collector 22 may also be removed appropriately.

[0034] The water scrubber 23 is not particularly limited as long as it has a configuration that brings the synthesis gas G1 into contact with water, but it is preferable that it has a configuration that brings water (for convenience, also referred to as "wash water") sprayed from a nozzle 25 provided at the top into contact with the synthesis gas G1, as shown in Fig. 1. In this case, the water scrubber 23 may be provided with an inlet passage 27, a supply passage 28, a discharge passage 29, etc. Furthermore, a reservoir 26 in which wash water is stored is provided below the water scrubber 23. The wash water stored in the reservoir 26 may be appropriately stirred by a stirring device (not shown).

[0035] The inlet passage 27 is a path for introducing the synthesis gas G1 into the water scrubber 23, and the inlet 27A of the inlet passage 27 is provided, for example, above the liquid level of the cleaning water stored in the storage section 26 inside the scrubber 12. The supply path 28 circulates water in the water scrubber 23 and supplies wash water to bring it into contact with the synthesis gas G1. Specifically, the supply path 28 sprays wash water stored in the storage section 26 downward from the nozzles 25 inside the water scrubber 23 and brings it into contact with the synthesis gas G1. Here, the supply path 28 is provided with, for example, a pump (not shown), and the wash water is pressure-fed to the nozzles 25 by the pump. The wash water is then sprayed downward from the nozzles 25 inside the scrubber 12. The discharge path 29 is provided at the top of the scrubber 12 and discharges the synthesis gas G1 to the outside after coming into contact with the wash water sprayed from the nozzles 25. The cleaning water used in the scrubber 23 may be water alone, or may contain chemicals as appropriate.

[0036] Furthermore, the water scrubber 23 may be provided with a removal device 19. The removal device 19 is, for example, a device for removing impurities (oil-based impurities, solid impurities, water-soluble impurities, etc.) contained in the wash water. For example, the removal device 19 may be provided midway through a circulation path that circulates the water in the reservoir 26. The removal device 19 may remove, for example, oil-based impurities contained in the wash water, solid impurities that are not dissolved in the wash water, water-soluble impurities that are dissolved in the wash water, etc. Therefore, the removal device 19 may be an oil-water separator, a filter that removes solid impurities, a combination of two or more of these, or any other configuration that can remove impurities contained in the wash water. By providing the removal device 19, the water scrubber 23 prevents impurities from accumulating in the wash water.

[0037] The synthesis gas G1 is preferably cooled by contacting with water in the water scrubber 23. As described above, the synthesis gas G1 is cooled in the gas cooling tower 21 and introduced into the water scrubber 23 in a state cooled to a predetermined temperature (preferably 100°C or higher and 200°C or lower, more preferably 120°C or higher and 180°C or lower, and even more preferably 130°C or higher and 170°C or lower). On the other hand, the temperature of the water that contacts the synthesis gas G1 in the water scrubber 23 is less than 100°C, preferably 0°C or higher and 40°C or lower, and more preferably 5°C or higher and 30°C or lower. In this specification, the "temperature of water in contact with the synthesis gas G1" refers to, when wash water is circulated and brought into contact with the synthesis gas G1 as described above, measuring the temperature of the water immediately before it comes into contact with the synthesis gas G1, that is, the temperature of the water (wash water) sprayed from the nozzle 15. In addition, when the synthesis gas G1 is introduced into stored water (wash water) as will be described later, measuring the temperature of the wash water stored in the storage section 26.

[0038] In the scrubber 23, the synthesis gas G1 comes into contact with water at the above temperature, and is thereby cooled in the water scrubber 23 to a temperature below 100°C, preferably 40°C or lower, and more preferably 38°C or lower. When the synthesis gas G1 is cooled in the water scrubber 23 to a predetermined temperature below the boiling point of water in this manner, at least a portion of the water (water vapor) mixed into the synthesis gas G1 is condensed and removed in the gas cooling tower 22. This makes it possible to appropriately remove water mixed in by the gas cooling tower 22 without providing a separate, large-scale device for removing the mixed water. Furthermore, by cooling to 40°C or lower, the synthesis gas G1 at an appropriate temperature can be supplied to the organic substance generation unit without providing a separate cooling device. Furthermore, even if a cooling device is included in the treatment device provided downstream of the water scrubber 23, the load on the cooling device can be reduced. By contacting the synthesis gas G1 with water, it is preferable that the synthesis gas G1 be cooled to a temperature of, for example, 0°C or higher, and preferably to a temperature of 5°C or higher.

[0039] The water scrubber 23 is preferably provided with a temperature control device (not shown), which controls the temperature of the wash water. The temperature control device may be attached to the supply path 28, for example, to adjust the temperature of the wash water passing through the supply path 28, or may be attached to the outer periphery of the water scrubber to adjust the temperature of the wash water stored in the reservoir 26 of the water scrubber. The temperature control device may cool the wash water passing through the supply path 28 or the wash water stored in the reservoir 26 to keep the temperature within the above-mentioned range. The water stored in the reservoir 26 may also be replaced as needed to maintain the temperature of the water coming into contact with the synthesis gas G1 within a certain temperature range.

[0040] In the above description, the water scrubber 23 has been described as a mode in which the synthesis gas G1 comes into contact with the cleaning water sprayed from the nozzle 25, but the synthesis gas G1 may also be introduced into the cleaning water stored in the storage section 26. In this case, the supply path 28 and the nozzle 25 are omitted, and the cleaning water is not sprayed from the nozzle. Also, the inlet 27A of the introduction path 27 is disposed below the liquid level of the cleaning water stored in the storage section 26. The synthesis gas G1 comes into contact with the cleaning water stored in the storage section 26, and thereby the synthesis gas G1 is preferably cleaned and cooled. Even when synthesis gas G1 is introduced into the cleaning water stored in the storage section 26, the temperature of the water in contact with the synthesis gas G1 and the temperature of the synthesis gas G1 (i.e., the temperature of the synthesis gas G1 introduced into the water scrubber 23, and the temperature of the synthesis gas G1 after cooling) are as described above.

[0041] (Other processing equipment) The treatment unit 3 may have treatment devices other than the above-described heat exchanger 20, gas cooling tower 21, filter-type dust collector 22, and water scrubber 23. As such a treatment device, a treatment device (also referred to as a "post-treatment device") may be provided downstream of the water scrubber 23, and the purified synthesis gas G2 that has passed through the water scrubber 23 may be supplied to the organic substance generation section 30 after being appropriately treated in the post-treatment device. Examples of downstream treatment devices include a moisture separator comprising a gas chiller or the like, a low-temperature separation (cryogenic) separator, a particulate separator comprising various filters, a desulfurizer (sulfide separator), a membrane separation separator, a deoxygenator, a pressure swing adsorption separator (PSA), a temperature swing adsorption separator (TSA), a pressure temperature swing adsorption separator (PTSA), a separator using activated carbon, and a separator using a deoxygenation catalyst, specifically, a copper catalyst or a palladium catalyst. These may be used alone or in combination of two or more. The purified synthesis gas G2 discharged from the water scrubber 23 may be further purified in these downstream treatment devices.

[0042] (Organic substance generation department) As described above, the synthesis gas G1 that has passed through at least the heat exchanger 20 and the gas cooling tower 21 is supplied as purified synthesis gas G2 to the organic substance production section 30. The purified synthesis gas G2 that is supplied to the organic substance production section 30 is preferably purified synthesis gas G2 that has passed through the heat exchanger 20, the gas cooling tower 21, the filter-type dust collector 22, and the water scrubber 23 in this order. The organic substance production section 30 produces organic substances by bringing the purified synthesis gas G2 into contact with a microbial catalyst. A gas-assimilating microorganism is preferably used as the microbial catalyst. The organic substance production unit 30 includes a fermenter (reactor) filled with a culture medium containing water and a microbial catalyst. The purified syngas G2 is supplied to the fermenter, and the purified syngas G2 is converted into organic substances within the fermenter. The organic substances preferably contain ethanol.

[0043] The fermenter is preferably a continuous fermentation apparatus, and may be any of agitation type, airlift type, bubble column type, loop type, open bond type, and photobio type. The purified synthesis gas G2 and the culture solution may be continuously supplied to the fermenter, but it is not necessary to supply the purified synthesis gas G2 and the culture solution simultaneously, and the purified synthesis gas G2 may be supplied to a fermenter to which the culture solution has been previously supplied. The purified synthesis gas G2 is generally blown into the fermenter via a sparger or the like. The medium used to cultivate a microbial catalyst is not particularly limited as long as it has an appropriate composition depending on the bacterium, but is a liquid containing water as the main component and nutrients (e.g., vitamins, phosphoric acid, etc.) dissolved or dispersed in this water. In the organic substance producing section 30, organic substances are produced by microbial fermentation using a microbial catalyst, and an organic substance-containing liquid is obtained.

[0044] The temperature of the fermenter is preferably controlled to 40° C. or below. By controlling the temperature to 40° C. or below, the microbial catalyst in the fermenter does not die, and organic substances such as ethanol are efficiently produced by contacting the purified synthesis gas G2 with the microbial catalyst. The temperature of the fermenter is more preferably 38°C or lower, and in order to enhance catalytic activity, it is preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher.

[0045] (separation device) The organic substance producing apparatus 1 includes a separation device 31 that separates at least water from the organic substance-containing liquid. The separation device 31 preferably includes a distillation device 33, and more preferably includes a solid-liquid separation device 32 in the upstream stage of the distillation device 33. The separation device 31 is preferably used in combination with the solid-liquid separation device 32 and the distillation device 33. The separation step performed using the solid-liquid separation device 32 and the distillation device 33 in combination will be specifically described below.

[0046] <Solid-liquid separator> The organic substance-containing liquid obtained in the organic substance production unit 30 may be separated in a solid-liquid separator 32 into a solid component mainly composed of microorganisms and a liquid component containing organic substances. The organic substance-containing liquid obtained in the organic substance production unit 30 contains, in addition to the target organic substance, microorganisms and their carcasses contained in the fermenter as solid components, so solid-liquid separation is performed to remove these. Examples of the solid-liquid separator 32 include a filter, a centrifuge, and a device using a solution precipitation method. The solid-liquid separator 32 may also be a device (e.g., a heat drying device) that evaporates the liquid component containing the organic substance from the organic substance-containing liquid and separates it from the solid component. In this case, the liquid component containing the target organic substance may be entirely evaporated, or the liquid component may be partially evaporated so that the target organic substance is preferentially evaporated.

[0047] <Distillation apparatus> The distillation apparatus 33 performs distillation to separate the target organic substances. The distillation apparatus 33 can purify large amounts of organic substances to high purity with a simple operation through separation by distillation. In the separation process performed by the distillation apparatus 33 in combination with the solid-liquid separation apparatus 32, the distillation apparatus 33 further performs distillation to separate the target organic substances from the liquid components separated by the solid-liquid separation apparatus 32, thereby purifying large amounts of organic substances to higher purity. A known distillation column or the like can be used as the distillation apparatus 33. The distillation may be performed, for example, such that the distillate contains the target organic substance (e.g., ethanol) at a high purity, while the bottoms (i.e., distillation residue) contains water as the main component (e.g., 70% by mass or more, preferably 90% by mass or more). By performing the distillation in this manner, the target organic substance and water can be largely separated.

[0048] The temperature inside the distillation apparatus 33 during distillation of an organic substance (e.g., ethanol) is not particularly limited, but is preferably 100° C. or less, and more preferably about 70 to 95° C. By setting the temperature inside the distillation apparatus 33 within the above range, it is possible to reliably separate the necessary organic substance from other components such as water. The pressure inside the distillation apparatus 33 during distillation of the organic substances may be normal pressure, but is preferably less than atmospheric pressure, more preferably about 60 to 150 kPa (gauge pressure). By setting the pressure inside the distillation apparatus 33 within the above range, the separation efficiency of the organic substances can be improved, and the yield of the organic substances can be increased.

[0049] The distillation apparatus 33 preferably utilizes thermal energy obtained from the synthesis gas G1 by the heat exchanger 20 described above for distillation. The distillation apparatus 33 can increase the temperature inside the distillation apparatus 33 during the distillation of the organic substance by reusing the thermal energy obtained from the synthesis gas G1 in the heat exchanger 20. In this way, by the distillation apparatus 33 reusing the thermal energy obtained from the synthesis gas G1 in the heat exchanger 20, the amount of energy used in the entire organic substance production process can be reduced. The thermal energy obtained from the synthesis gas G1 in the heat exchanger 20 can be transferred via a thermal energy path 33a connected to the heat exchanger 20 and the distillation apparatus 33. The thermal energy path 33a is not particularly limited and may have any configuration that transfers the thermal energy of the synthesis gas G1 from the heat exchanger 20 to the distillation apparatus 33 using a heat medium. The heat medium may be either a gas or a liquid, and may also be one that undergoes a phase change between gas and liquid. Furthermore, as described above, the heat exchanger 20 is preferably a boiler, and therefore, steam is preferred as the heat medium. By using steam as the heat medium, it is easy to reuse the thermal energy of the synthesis gas G1. When steam is used as the heat medium, part of the steam may be liquefied.

[0050] The water separated in the separator 31 is preferably reused, and more preferably supplied to the gas cooling tower 21 and used for water spray in the gas cooling tower 21. Reusing the water in this way prevents the water no longer needed in the organic substance production section 30 from being discharged as wastewater, which is preferable from the standpoints of environmental protection and economy. The organic substance production apparatus 1 may also have a supply path 31a connected to the separator 31 and the gas cooling tower 21, for supplying the water obtained in the separator 31 to the gas cooling tower 21. The supply path 31a is not particularly limited, but may be composed of piping or the like. The water separated in the separator 31 may also be further purified to increase its purity before being supplied to the gas cooling tower 21.

[0051] As described above, according to this embodiment, the synthesis gas G1 is cooled by the heat exchanger 20 and by spraying water from the gas cooling tower 21, so that the synthesis gas G1 can be cooled without blowing in nitrogen gas or air. Therefore, the temperature of the synthesis gas G1 can be lowered without changing the composition of the synthesis gas G1, and organic substances can be synthesized without killing the microbial catalyst. Furthermore, according to this embodiment, the synthesis gas G1 is cooled by the heat exchanger 20, and then the synthesis gas G1 is cooled by water spray from the gas cooling tower 21, so that the heat exchanger 20 plays a part of the role of cooling the synthesis gas G1, and the role of cooling in the gas cooling tower 21 is reduced. This makes it possible to reduce the amount of water sprayed to cool the synthesis gas in the gas cooling tower 21, and also makes it possible to reduce the amount of wastewater discharged from the gas cooling tower 21.

[0052] Furthermore, according to this embodiment, the thermal energy obtained from the synthesis gas G1 by the heat exchanger 20 can be used to increase the temperature inside the distillation apparatus 33 during the distillation of the organic substance. This makes it possible to reduce the amount of energy procured from outside for the distillation in the distillation apparatus 33, thereby enabling a reduction in the amount of energy used in the entire production process of the organic substance.

[0053] Although the above embodiment shows a configuration in which the water scrubber 23 is provided, the water scrubber 23 may be omitted. When the water scrubber 23 is omitted, the synthesis gas G1 that has passed through at least the gas cooling tower 21 and the filter-type dust collector 22 is brought into contact with a microbial catalyst in the organic substance generation section 30 and converted into organic substances. In this embodiment, the synthesis gas G1 discharged from the filter-type dust collector 22 is typically at a relatively high temperature (for example, 100°C or higher). However, when the water scrubber 23 is omitted, it is preferable that a cooling device other than the water scrubber 23 be provided downstream of the filter-type dust collector 22, and the synthesis gas G1 discharged from the filter-type dust collector 22 be cooled by a cooling device other than the water scrubber 23. Furthermore, when the water scrubber 23 is omitted, in addition to the cooling device, one or more treatment devices selected from the above-mentioned downstream treatment devices are provided downstream of the filter dust collector 22, and the synthesis gas G1 discharged from the filter dust collector 22 may be appropriately treated in the downstream treatment device. Furthermore, in cases where there is no need to purify the organic substance produced in the organic substance production section 30 or where there is no need to separate water from the organic substance-containing liquid, the separation device 31 may be omitted.

[0054] Furthermore, in the above embodiment, a configuration in which the filter-type dust collector 22 is provided is shown, but the filter-type dust collector 22 may be omitted. If the filter-type dust collector 22 is omitted, the synthesis gas G1 cooled in the gas cooling tower 21 will be supplied to the water scrubber 23 without passing through the filter-type dust collector 22. For example, the filter-type dust collector 22 may be omitted when the waste contains few solid impurities or when synthesis gas is produced using a raw material other than the waste, as will be described later. Of course, both the water scrubber 23 and the filter-type dust collector 22 may be omitted.

[0055] As described above, the processing unit 3 in the purified synthesis gas production system includes at least the heat exchanger 20 and the gas cooling tower 21, and preferably further includes a filter-type dust collector 22 and a water scrubber 23. In addition to these, the processing unit 3 may also include downstream processing devices as appropriate. Details of these devices are as described above, and therefore will not be described here.

[0056] Furthermore, in the above embodiment, the synthesis gas G1 is obtained from waste in the gasification apparatus 2. However, the synthesis gas G1 may also be produced from sources other than waste in the gasification apparatus 2. For example, the synthesis gas G1 may be produced from fossil resources such as natural gas, coal, heavy oil, petroleum exhaust gas, and oil shale, or from biomass other than waste. Furthermore, the synthesis gas may be a by-product gas in various manufacturing processes such as a steel manufacturing process. For example, the gasification apparatus 2 may be part of a steel manufacturing facility. [Explanation of symbols]

[0057] 1 Organic substance production equipment 2. Gasifier 3 Processing Unit 10 Gasifier 11 Reformer 20 Heat exchanger 21 Gas Cooling Tower 22 Filter dust collector 23 Water Scrubber 24 Water spray nozzle 25 nozzles 26 Storage section 27 Introductory path 28 Supply route 29 Exhaust channel 30 Organic substance generation section 31 Separation device 31a Supply Channel 32 Solid-liquid separator 33 Distillation apparatus 33a Thermal Energy Pathway G1 Syngas G2 Purified Syngas

Claims

1. a gasification step in which the waste is pyrolyzed and partially oxidized to gasify it to produce pyrolysis gas; a reforming step of reforming impurities contained in the pyrolysis gas into hydrogen and carbon monoxide to generate a synthesis gas; a first gas cooling step of cooling the synthesis gas produced in the reforming step by passing the synthesis gas through a heat exchanger; a second gas cooling step of further cooling the synthesis gas cooled in the heat exchanger by spraying water; an organic matter production step in which the synthesis gas that has passed through at least the heat exchanger and the gas cooling by water spray is brought into contact with a microbial catalyst to produce organic matter; In at least one of the gasification step and the reforming step, the concentrations of the components constituting the synthesis gas are adjusted to an oxygen concentration of 0.01% by volume or more and 5% by volume or less.

2. 2. The method for producing an organic substance according to claim 1, wherein the concentration of nitrogen in the synthesis gas is adjusted to 1% by volume or more and 40% by volume or less by adjusting the concentrations of components constituting the synthesis gas.

3. 3. The method for producing an organic substance according to claim 1, further comprising a separation step of separating at least water from the organic substance-containing liquid obtained by producing the organic substance through microbial fermentation of the microbial catalyst after the organic substance production step, and the water separated in the separation step is used in the second gas cooling step by water spray.

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