JP2020116552A - Reusing method of zeolite absorbent and reclaimed absorbent - Google Patents

Abstract

To provide a reusing method of an absorbent capable of stably exhibiting refining capacity, by reclaiming a used absorbent, for maintaining a composition of a purified synthetic gas purified constant by using a pressure swing absorbing device.SOLUTION: A reusing method of a zeolite absorbent is a method of reclaiming a zeolite absorbent used for a pressure swing absorbing device for absorbing and reducing a carbon dioxide gas in a synthetic gas after the synthetic gas containing a hydrogen gas, a nitrogen gas, a carbon monoxide gas and a carbon dioxide gas as main component exhausted from a gasification furnace, and includes the steps of: recovering the used zeolite absorbent from the pressure swing absorbing device; reclaiming by firing under an oxygen atmosphere; and reusing the reclaimed zeolite absorbent as an absorbent of the pressure swing absorbing device, in which the used zeolite absorbent is fired until a specific surface area according to the BET method using a nitrogen gas to be -15.0 to -1.0% relative to an unused zeolite absorbent.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for reusing a zeolite adsorbent, and more particularly to a method for reusing a zeolite adsorbent used in a pressure swing adsorption device that reduces the concentration of carbon dioxide gas in synthesis gas. The present invention also relates to a regenerated adsorbent comprising a fired product of a used zeolite adsorbent.

In recent years, from the perspective of global environmental problems such as fear of depletion of fossil fuel resources due to large consumption of oils and alcohol produced from petroleum and increase of carbon dioxide in the atmosphere, various organic materials other than petroleum are used. Methods for producing substances have been investigated. For example, a method of producing bioethanol from an edible raw material such as corn by a sugar fermentation method has been attracting attention. However, the sugar fermentation method using such an edible raw material has a problem that the food price rises because the limited agricultural land area is used for production other than food.

In order to solve such a problem, various methods for producing various organic substances conventionally produced from petroleum by using non-edible raw materials which have been conventionally discarded have been studied. For example, conversion of synthesis gas containing carbon dioxide, carbon monoxide, and hydrogen into acetic acid and ethanol by microbial fermentation is performed. In the method for producing ethanol by microbial fermentation from such a synthetic gas, when pollutants and impurities are present in the synthetic gas or its raw material gas, microbial fermentation is inhibited, and an organic substance is efficiently obtained. There was a problem such as not being able to. In order to solve such a problem, a raw material gas has been purified to obtain a synthesis gas.

However, even when using a synthesis gas from which contaminants and impurities have been removed by purification, there is still a problem that the organic substance cannot be efficiently obtained depending on the gas composition in the synthesis gas. Therefore, in Patent Document 1, in a method for purifying a synthesis gas containing hydrogen, carbon monoxide and/or nitrogen as main components and contaminated with carbon dioxide and, in some cases, with one or more other impurities, zeolite is used. It has been proposed to remove carbon dioxide in synthesis gas by the pressure swing adsorption method using sucrose as an adsorbent.

JP, 2003-246606, A

The present inventor carried out purification of synthesis gas for a long period of time by the method described in Patent Document 1, and as a result, the performance of zeolite as an adsorbent was lowered, and a sufficient purification effect could not be obtained. Therefore, the present inventor replaced the zeolite as the adsorbent with a new (unused) zeolite, but the refining capacity was not stable for a certain period from the start of use, and the gas composition in the synthesis gas was kept constant. I found a new problem that it does not exist.

Therefore, it is an object of the present invention to recycle used adsorbents in order to maintain a constant composition of syngas purified using a pressure swing adsorption device, and to reuse adsorbents that can exert their purification ability in a stable manner. Is to provide a method.

The present inventor uses the regenerated zeolite adsorbent after regenerating the used zeolite adsorbent to a specific state without replacing the used zeolite adsorbent with a new (unused) zeolite adsorbent. , It has been found that the refining ability is stably exhibited and the above-mentioned problems can be solved. That is, the gist of the present invention is as follows.

[1] A synthesis gas containing hydrogen gas, nitrogen gas, carbon monoxide gas and carbon dioxide gas as main components discharged from the gasification furnace is supplied to adsorb carbon dioxide gas in the synthesis gas, A method of regenerating a zeolite adsorbent used in a pressure swing adsorption device for reducing the carbon dioxide gas concentration in
A step of collecting the used zeolite adsorbent from the pressure swing adsorption device,
A step of regenerating the zeolite adsorbent by firing the zeolite adsorbent in an oxygen atmosphere, and a step of using the regenerated zeolite adsorbent again as an adsorbent of a pressure swing adsorption device,
Equipped with
Zeolite adsorbent, in which the used zeolite adsorbent is calcined until it reaches -15.0 to -1.0% in terms of specific surface area by BET method using nitrogen gas with respect to unused zeolite adsorbent How to reuse.

[2] In the used zeolite adsorbent, carbon compounds and sulfur compounds are attached to the pores in the zeolite crystal structure, and compared with the unused zeolite by the specific surface area conversion by the BET method using nitrogen gas. -15.0% or more.

[3] The method according to [1] or [2], wherein the syngas discharged from the gasification furnace contains a tar component.

[4] The method according to any one of [1] to [3], wherein the zeolite is an LSX type zeolite.

[5] A regenerated adsorbent comprising a fired product of a used zeolite adsorbent,
Carbon compounds and sulfur compounds are attached to the pores in the zeolite crystal structure,
A regenerated adsorbent having a specific surface area of -15.0 to -1.0% based on the unused zeolite, which is calculated by the BET method using nitrogen gas.

[6] The regenerated adsorbent according to [5], wherein the zeolite is LSX type zeolite.

[7] A method for producing an organic substance from a synthetic gas containing carbon monoxide by microbial fermentation, comprising:
A synthetic gas purification step of reducing the carbon dioxide gas concentration in the synthetic gas using the regenerated adsorbent according to [5] or [6];
Supplying a synthetic gas obtained by the synthesis gas purification step to a microbial fermentation tank, a microbial fermentation step of obtaining an organic substance-containing liquid by the microbial fermentation,
A separation step in which the organic substance-containing liquid is heated to room temperature or higher to 500° C. under a condition of 0.01 to 1000 kPa to separate into a liquid or solid component containing a microorganism and a gas component containing an organic substance;
A liquefaction step of liquefying by condensing the gas component obtained by the separation step,
A purification step of purifying an organic substance from the liquefaction product obtained by the liquefaction step,
A method for producing an organic substance, comprising:

[8] The method according to [7], wherein the heat of condensation generated in the liquefaction step is reused as a heat source when purifying an organic substance from a liquid containing an organic substance.

[9] The method according to [7] or [8], wherein the synthesis gas is obtained by gasifying a carbon source.

[10] The method according to [9], wherein the carbon source is waste.

[11] The method according to any one of [7] to [10], wherein the organic substance contains an alcohol having 1 to 6 carbon atoms.

[12] An organic substance obtained by the method according to any one of [7] to [11].

According to the present invention, it is possible to provide a method for reusing an adsorbent capable of stably exhibiting the refining ability in order to keep the composition of the synthesis gas purified by using the pressure swing adsorption device constant. By using the regenerated adsorbent obtained by the method of the present invention, the synthesis gas can be stably purified.

Further, according to the present invention, by reducing the carbon dioxide gas concentration in the syngas by using the regenerated adsorbent, the microbial fermentation of the syngas is efficiently performed, and as a result, the organic gas is efficiently and economically produced. The substance can be obtained.

It is a process flow figure showing an example of the reuse method of the zeolite adsorption material by the present invention. It is a process flow figure showing an example of the manufacturing method of the organic substance by the present invention.

Hereinafter, an example of a preferable mode for carrying out the present invention will be described. However, the following embodiments are examples for explaining the present invention, and the present invention is not limited to the following embodiments. In the present specification, the abundance ratio of each component in the gas is a ratio based on the volume, not the mass, unless otherwise specified. Therefore, unless otherwise specified, percentages represent volume% and ppm represent volume ppm.

<Reuse method of zeolite adsorbent>
The present invention is a method for reusing a zeolite adsorbent used in a pressure swing adsorption apparatus, which includes a recovery step, a regeneration step, and a reuse step (see FIG. 1). The pressure swing adsorption device is used in the synthesis gas purification step in the method for producing an organic substance of the present invention described in detail below, and adsorbs carbon dioxide gas in the supplied synthesis gas, This is for reducing the carbon dioxide gas concentration. Hereinafter, each step in the recycling method according to the present invention will be described in detail.

(Collection process)
The recovery step in the recycling method according to the present invention is a step of recovering used zeolite adsorbent from the pressure swing adsorption device (see FIG. 1). First, the zeolite adsorbent used in the pressure swing adsorption device will be described.

The zeolite adsorbent may be any as long as it can adsorb carbon dioxide gas contained in the synthesis gas, and examples thereof include X-type zeolite and Y-type zeolite which are faujasite type zeolites, and X-type zeolite is preferable. The content of the X-type zeolite in the zeolite adsorbent is 50% by mass or more, preferably 75% by mass or more, and more preferably 95% by mass or more. Examples of components other than zeolite include a binder used for binding zeolite. As the binder, porous and amorphous ones such as alumina, silica-alumina, titania-alumina, zirconia-alumina, and boria-alumina can be preferably used. Among them, alumina, silica-alumina and boria-alumina are preferable because they have a strong binding force for zeolite and have a high specific surface area. These have the role of improving the strength of the catalyst.

The Si/Al (mol) ratio of the X-type or Y-type zeolite is preferably 0.6 to 4.0, more preferably 1.2 to 3.0. The cation contained in the zeolite is preferably lithium, sodium or a proton, more preferably lithium. In the present invention, in consideration of the adsorption/desorption performance of carbon dioxide, LSX type zeolite having Si/Al in the range of 0.9 to 1.1, preferably in the range of 1 to 1.05 is used as the main component. Preferably.

The shape of the zeolite adsorbent containing LSX-type zeolite as a main component is not particularly limited, but may be, for example, in the form of particles or in the state of an aggregate. For example, the LSX zeolite may be mixed with an agglomerated binder, and the mixture may then be used as an aggregate by extrusion or bead formation. Binders used for agglomerating zeolites include clay, silica, alumina, metal oxides, and mixtures thereof.

In addition, zeolites include materials such as silica/alumina, silica/magnesia, silica/zirconia, silica/thorium, silica/beryllium oxide, and silica/titanium dioxide, as well as three materials such as silica/alumina/tria, silica/alumina/zirconia. It may be agglomerated with the original composition as well as the clay present as a binder.

The zeolite adsorbent in the pressure swing adsorption device adsorbs carbon dioxide gas in the synthesis gas and keeps the carbon dioxide gas concentration in the synthesis gas at a certain value or less. The synthesis gas supplied to the pressure swing adsorption device is, as described later, various pollutants, dust particles, impurities, undesired amounts of specific substances such as undesired amounts of specific substances removed or reduced from the source gas. A small amount of tar components, especially carbon compounds and sulfur compounds are contained, and these tar components are also adsorbed on the zeolite adsorbent. In the present invention, even a used zeolite adsorbent in which a carbon compound or a sulfur compound as described above is adsorbed is used zeolite adsorbent so as to have a constant surface area ratio with respect to an unused zeolite adsorbent. It has been found that the calcination can obtain an adsorption performance equivalent to that of an unused zeolite adsorbent.

As described above, along with the operation of the pressure swing adsorption device, not only carbon dioxide but also carbon compounds and sulfur compounds adhere to the pores in the zeolite crystal structure, so that the carbon dioxide adsorption performance gradually decreases. When the carbon dioxide adsorption performance is lowered, the used zeolite adsorbent is recovered from the pressure swing adsorption device. The time for collecting the used zeolite adsorbent from the pressure swing adsorption device is not particularly limited, but the period of use and the surface area measurement result by the BET method using nitrogen gas of the zeolite adsorbent can be used as an index. Specifically, when the specific surface area of the used zeolite adsorbent is -15% or less in terms of specific surface area with respect to the unused zeolite adsorbent, the adsorption performance of the carbon dioxide of the zeolite decreases, and the synthetic gas There is a possibility that the carbon dioxide concentration in the inside cannot be reduced sufficiently. Therefore, in the present invention, in order to prevent the deterioration of the adsorption performance of the zeolite adsorbent, the specific surface area of the used zeolite adsorbent is converted to that of the unused zeolite adsorbent by the BET method using nitrogen gas. It is preferable to recover the zeolite adsorbent by using -15% or more as an index. In the present invention, the specific surface area was measured by nitrogen gas adsorption-BET multipoint method. Specifically, a BET plot was created from the nitrogen gas adsorption isotherm at the liquid nitrogen temperature (77 K), and the BET method specific surface area was calculated from the linear approximation of the BET plot. The pretreatment condition was degassing under reduced pressure at 300°C. In addition, the unused zeolite adsorbent means the zeolite adsorbent before being installed in the pressure swing adsorption device, the zeolite adsorbent that has never been used as an adsorbent, and the used after the method described below. It is intended to include a state before the zeolite adsorbent is regenerated and used again in the pressure swing adsorption device.

(Regeneration process)
The regeneration step in the recycling method according to the present invention is to regenerate the zeolite adsorbent by firing the used zeolite adsorbent recovered from the pressure swing adsorption device in an oxygen atmosphere (see FIG. 1). As described above, the zeolite adsorbent used in the pressure swing adsorption device has carbon compounds and sulfur compounds attached to pores in its crystal structure, in addition to carbon dioxide, and has a pore volume of the zeolite adsorbent. However, it is less than the unused zeolite adsorbent. In the present invention, the used zeolite adsorbent recovered from the pressure swing adsorber is used to convert the unused zeolite adsorbent into a specific surface area of -15.0 to -1.0 by the BET method using nitrogen gas. %, preferably -10.0 to -2.0%, more preferably -5.0 to -2.0%.

The used zeolite adsorbent is preferably calcined at a temperature of 300°C to 600°C. In particular, when the zeolite adsorbent contains LSX-type zeolite as the main component, the firing temperature is preferably 350°C to 550°C, more preferably 400 to 500°C. When the calcination temperature is 300° C. or higher, the carbon compounds and sulfur compounds attached to the zeolite adsorbent can be reduced by calcination. Further, when the firing temperature is 600° C. or lower, the sulfur compound attached to the zeolite adsorbent can be appropriately left. In the regenerating step, the temperature of the zeolite adsorbent during firing can be controlled by appropriately adjusting the temperature of the air stream, the flow rate of the air stream, the oxygen concentration, and the like.

In the regeneration step, the carbon compound in the used zeolite adsorbent is brought into contact with oxygen and fired. For this reason, it is preferable that the oxygen-containing gas gradually introduce oxygen (or air) to gradually increase the oxygen concentration in order to avoid an excessive temperature rise due to firing of carbon. Although the final oxygen concentration in the regeneration step may be high, it is 30% or less, preferably 0.1 to 21% from the viewpoint of economy. Up to 21% is more economical because air can be used. As a component other than oxygen, an inert gas such as nitrogen, helium or argon is preferable. When air is used as the oxygen-containing gas, it is preferable to use dry air or dehydrated air.

The calcination time is not particularly limited as long as the amount of the carbon compound attached to the zeolite adsorbent can be sufficiently reduced and regenerated. For example, the used zeolite adsorbent is preferably calcined to -15.0% or more in terms of specific surface area, more preferably -10.0% or more to the unused zeolite adsorbent, It is more preferable to bake to 5.0% or more. The lower the firing temperature is and the shorter the firing temperature is, the more the thermal history can be suppressed and the repeated cycle life can be extended, which is more economical. The degree of regeneration of the zeolite adsorbent can be judged by confirming that the temperature of the adsorbent does not rise during firing or that carbon dioxide is not detected in the exhaust gas stream.

(Reuse process)
The reuse step in the reuse method according to the present invention is a step in which the zeolite adsorbent calcined in the regeneration step is reused as the adsorbent of the pressure swing adsorption device (see FIG. 1). By using the calcined zeolite adsorbent again as the adsorbent of the pressure swing adsorption device, it is possible to stably exhibit the same adsorption performance as that before the replacement of the zeolite adsorbent. Therefore, the synthesis gas purified in the following synthesis gas purification step, the gas composition is appropriately adjusted, microbial fermentation of the synthesis gas is efficiently performed in the subsequent microbial fermentation step, as a result, efficient and An organic substance can be obtained economically.

<Regenerated adsorbent>
The regenerated adsorbent according to the present invention is composed of a calcined product of a used zeolite adsorbent and has carbon compounds and sulfur compounds attached to the pores in the zeolite crystal structure. The recycled adsorbent has a specific surface area of -15.0 to -1.0%, preferably -10.0 to -2.0%, and more preferably -relative to the unused zeolite adsorbent. It is 5.0 to -2.0%. If the specific surface area of the regenerated adsorbent is within the above range, the adsorption performance that has deteriorated due to use can be recovered, and more stable adsorption performance can be exhibited compared to a new (unused) adsorbent. It can be suitably used for a pressure swing adsorption device that adsorbs carbon dioxide gas in gas and reduces the concentration of carbon dioxide gas in synthesis gas.

The regenerated adsorbent according to the present invention can be produced by the method described in the regenerating step in the above-mentioned method for reusing the zeolite adsorbent.

<Method for producing organic substance>
The method for producing an organic substance according to the present invention is to produce an organic substance by microbial fermentation from a synthetic gas purified using the above regenerated adsorbent, and a synthetic gas purification step, a microbial fermentation step, a separation step, It includes a liquefaction process and an organic substance refining process. Hereinafter, an example of the method for producing an organic substance according to the present invention will be described in detail.

First, an example of the method for producing an organic substance according to the present invention will be described with reference to the drawings. FIG. 2 is a process flow chart showing an example of the method for producing an organic substance according to the present invention. The method for producing an organic substance according to the present invention comprises a microbial fermentation step of supplying a synthetic gas containing carbon monoxide to a microbial fermentation tank to obtain an organic substance-containing liquid by microbial fermentation; A separation step for separating a solid component and a gas component containing an organic substance, a liquefaction process for condensing the gas component to liquefy, and a purification process for purifying an organic substance from the liquid substance obtained in the liquefaction process are essential. However, if necessary, a raw material gas generation step, a synthesis gas preparation step, a wastewater treatment step, etc. may be included. Hereinafter, each step will be described.

<Raw material gas generation process>
The raw material gas production step is a step of producing a raw material gas by gasifying a carbon source in the gasification section (see FIG. 2 ). A gasification furnace may be used in the raw material gas generation step. The gasification furnace is a furnace for burning a carbon source (incomplete combustion), and examples thereof include a shaft furnace, a kiln furnace, a fluidized bed furnace, and a gasification reforming furnace. The gasification furnace is preferably a fluidized bed furnace type because a high hearth load and excellent operability can be achieved by partially burning the waste. The waste is gasified in a fluidized-bed furnace at low temperature (about 450-600°C) and low oxygen atmosphere to decompose it into char (carbon monoxide, carbon dioxide, hydrogen, methane, etc.) and carbon-rich char. To do. Furthermore, since the incombustibles contained in the waste are separated from the furnace bottom in a sanitary and low-oxidation state, it is possible to selectively recover valuable substances such as iron and aluminum in the incombustibles. Therefore, gasification of such waste enables efficient resource recycling.

The gasification temperature in the raw material gas generation step is usually 100°C or higher and 1500°C or lower, preferably 200°C or higher and 1200°C or lower.

The reaction time for gasification in the raw material gas generation step is usually 2 seconds or longer, preferably 5 seconds or longer.

The carbon source used in the raw material gas generation process is not particularly limited, and examples thereof include a coke oven in a steel mill, a blast furnace (blast furnace gas), coal used in a converter or a coal-fired power plant, an incinerator (especially a gasification furnace). Various carbon-containing materials can be suitably used for the purpose of recycling, such as general waste and industrial waste introduced into, and carbon dioxide by-produced by various industries.

More specifically, carbon sources include plastic waste, raw garbage, municipal solid waste (MSW), industrial solid waste, waste tires, biomass waste, household waste such as futon and paper, and waste such as building materials. And coal, petroleum, petroleum-derived compounds, natural gas, shale gas, and the like. Among them, various wastes are preferable, and unsorted municipal solid waste is more preferable from the viewpoint of separation cost.

The raw material gas obtained by gasifying the carbon source contains carbon monoxide and hydrogen as essential components, but may further contain carbon dioxide, oxygen, and nitrogen. As other components, the raw material gas may further contain components such as soot, tar, nitrogen compounds, sulfur compounds, phosphorus compounds and aromatic compounds.

In the raw material gas generation step, the raw material gas is subjected to a heat treatment (commonly called gasification) for burning (incompletely burning) the carbon source, that is, by partially oxidizing the carbon source, so that carbon monoxide is Although not limited, it may be produced as a gas containing 0.1 vol% or more, preferably 10 vol% or more, more preferably 20 vol% or more.

<Syngas purification process>
The synthesis gas purification step is a step of removing or reducing specific substances such as various pollutants, dust particles, impurities, and undesired amounts of compounds from the raw material gas (see FIG. 2). When the source gas is derived from waste, the source gas is usually 0.1 vol% or more and 80 vol% or less of carbon monoxide, 0.1 vol% or more and 40 vol% or less of carbon dioxide, and 0% or less of hydrogen. 1% by volume or more and 80% by volume or less, nitrogen compounds by 1 ppm or more, sulfur compounds by 1 ppm or more, phosphorus compounds by 0.1 ppm or more, and/or aromatic compounds by 10 ppm or more. In addition, other environmental pollutants, dust particles, impurities, and other substances may be included. Therefore, in supplying the synthetic gas to the microbial fermenter, from the raw material gas, substances that are not preferable for stable culture of microorganisms, undesired amounts of compounds, etc. are reduced or removed, and the content of each component contained in the raw material gas is reduced. Is preferably in a range suitable for stable culture of microorganisms.

In particular, in the synthesis gas purification step, the pressure swing adsorption device filled with the above-mentioned regenerated adsorbent is used to adsorb carbon dioxide gas in the syngas to the regenerated adsorbent (zeolite), and the carbon dioxide gas concentration in the syngas is increased. To reduce. Furthermore, the synthesis gas may be subjected to other conventionally known processing steps to remove impurities and adjust the gas composition. Other processing steps include, for example, a gas chiller (water separator), a low temperature separator (deep cooling separator), a cyclone, a particle (soot) separator such as a bag filter, and a scrubber (water-soluble impurity separator). , Desulfurization equipment (sulfide separation equipment), Membrane separation type separation equipment, Deoxygenation equipment, Pressure swing adsorption type separation apparatus (PSA), Temperature swing adsorption type separation apparatus (TSA), Pressure temperature swing adsorption type separation The treatment can be carried out using one or more of a device (PTSA), a separation device using activated carbon, a separation device using a copper catalyst or a palladium catalyst, and the like.

The synthesis gas used in the method for producing an organic substance of the present invention contains at least carbon monoxide as an essential component, and may further contain hydrogen, carbon dioxide, and nitrogen.

The synthesis gas used in the present invention produces a raw material gas by gasifying a carbon source (raw material gas producing step), and then adjusts the concentration of each component of carbon monoxide, carbon dioxide, hydrogen and nitrogen from the raw material gas. At the same time, the gas obtained through the steps of reducing or removing the substances and compounds as described above may be used as the synthesis gas.

The carbon monoxide concentration in the synthesis gas is usually 20% by volume or more and 80% by volume or less, preferably 25% by volume or more and 50% by volume, based on the total concentration of carbon monoxide, carbon dioxide, hydrogen and nitrogen in the synthesis gas. It is not more than 35% by volume, more preferably not less than 35% by volume and not more than 45% by volume.

The hydrogen concentration in the synthesis gas is usually 10% by volume or more and 80% by volume or less, preferably 30% by volume or more and 55% by volume, with respect to the total concentration of carbon monoxide, carbon dioxide, hydrogen and nitrogen in the synthesis gas. It is below, and more preferably from 40% by volume to 50% by volume.

The carbon dioxide concentration in the synthesis gas is usually 0.1% by volume or more and 40% by volume or less, preferably 0.3% by volume or more with respect to the total concentration of carbon monoxide, carbon dioxide, hydrogen and nitrogen in the synthesis gas. It is 30 volume% or less, more preferably 0.5 volume% or more and 10 volume% or less, and particularly preferably 1 volume% or more and 6 volume% or less.

The nitrogen concentration in the synthesis gas is usually 40% by volume or less, preferably 1% by volume or more and 20% by volume or less, with respect to the total concentration of carbon monoxide, carbon dioxide, hydrogen and nitrogen in the synthesis gas. It is more preferably 5% by volume or more and 15% by volume or less.

Regarding the concentrations of carbon monoxide, carbon dioxide, hydrogen and nitrogen, the C-H-N elemental composition of the carbon source is changed in the raw material gas generation process, and the combustion conditions such as the combustion temperature and the oxygen concentration of the supply gas during combustion are set. It can be set within a predetermined range by appropriately changing it. For example, if you want to change the concentration of carbon monoxide or hydrogen, change to a carbon source with a high C-H ratio such as waste plastic, and if you want to reduce the nitrogen concentration, supply a gas with a high oxygen concentration in the raw material gas generation process. There are ways to do it.

The synthesis gas used in the present invention may contain a sulfur compound, a phosphorus compound, a nitrogen compound, etc., in addition to the above-mentioned components, but is not particularly limited. The content of each of these compounds is preferably 0.05 ppm or more, more preferably 0.1 ppm or more, still more preferably 0.5 ppm or more, and preferably 2000 ppm or less, more preferably 1000 ppm or less, further preferably Is 80 ppm or less, even more preferably 60 ppm or less, and particularly preferably 40 ppm or less. By setting the content of sulfur compounds, phosphorus compounds, nitrogen compounds and the like to the lower limit or more, there is an advantage that the microorganisms can be suitably cultured, and by setting the content to the upper limit or less, the microorganisms were not consumed. There is an advantage that the medium is not contaminated by various nutrient sources.

Examples of the sulfur compound generally include sulfur dioxide, CS ₂ , COS, and H ₂ S. Among them, H ₂ S and sulfur dioxide are preferable because they are easily consumed as nutrient sources for microorganisms. Therefore, it is more preferable that the synthesis gas contains the sum of H ₂ S and sulfur dioxide in the above range.
As the phosphorus compound, phosphoric acid is preferable because it can be easily consumed as a nutrient source for microorganisms. Therefore, it is more preferable that the synthesis gas contains phosphoric acid in the above range.
Examples of the nitrogen compound include nitric oxide, nitrogen dioxide, acrylonitrile, acetonitrile, HCN and the like, and HCN is preferable because it can be easily consumed as a nutrient source for microorganisms. Therefore, it is more preferable that the syngas contains HCN in the above range.

Further, the synthesis gas may contain 0.01 ppm or more and 90 ppm or less of an aromatic compound, preferably 0.03 ppm or more, more preferably 0.05 ppm or more, further preferably 0.1 ppm or more, and preferably 70 ppm. Or less, more preferably 50 ppm or less, still more preferably 30 ppm or less. By setting the content above the lower limit, the microorganisms tend to be preferably cultured, and by setting the content below the upper limit, the medium tends to be less likely to be contaminated by various nutrient sources that the microorganism did not consume. It is in.

<Microbial fermentation process>
The microbial fermentation step is a step of microbially fermenting the above-mentioned synthetic gas in a microbial fermentation tank to produce an organic substance (see FIG. 2). The microbial fermentation tank is preferably a continuous fermentation device. In general, the microbial fermenter can be used in any shape, and examples thereof include a stirring type, an airlift type, a bubble column type, a loop type, an open bond type, and a photobio type. However, a known loop reactor having a main tank section and a reflux section can be preferably used. In this case, it is preferable to further include a circulation step of circulating the liquid medium between the main tank section and the reflux section.

The synthesis gas supplied to the microbial fermenter may be the gas obtained through the raw material gas production step as it is as long as the above-mentioned conditions for the components of the synthetic gas are satisfied, or impurities etc. can be reduced from the raw material gas. Alternatively, the synthesis gas may be used after adding another predetermined gas to the removed gas. As another predetermined gas, for example, at least one compound selected from the group consisting of sulfur compounds such as sulfur dioxide, phosphorus compounds, and nitrogen compounds may be added to form a synthesis gas.

The microbial fermenter may be continuously supplied with the synthetic gas and the microbial culture solution, but it is not necessary to supply the synthetic gas and the microbial culture solution at the same time. Syngas may be supplied. It is known that certain anaerobic microorganisms produce organic substances, which are valuable substances such as ethanol, from a substrate gas such as synthesis gas by a fermentation action. It is cultured in the medium. For example, a liquid medium and a gas-assimilating bacterium may be supplied and housed, and in this state, the synthetic gas may be supplied into the microbial fermentation tank while stirring the liquid medium. As a result, the gas-utilizing bacterium can be cultured in the liquid medium, and the organic substance can be produced from the synthetic gas by its fermentation action.

In the microbial fermenter, the temperature of the medium or the like (culture temperature) may be any temperature, but is preferably about 30 to 45°C, more preferably about 33 to 42°C, further preferably 36.5 to 37. It can be about 5°C. The culture time is preferably 12 hours or longer in continuous culture, more preferably 7 days or longer, particularly preferably 30 days or longer, and most preferably 60 days or longer. From the viewpoint, it is preferably 720 days or less, more preferably 365 days or less. The culture time means the time from the addition of the inoculum to the culture tank until the discharge of the entire culture solution from the culture tank.

The microorganism (seed) contained in the microorganism culture liquid is not particularly limited as long as it can produce a desired organic substance by microbial fermentation of synthetic gas using carbon monoxide as a main raw material (see FIG. 2). For example, it is preferable that the microorganism (seed) is one that produces an organic substance from the synthetic gas by the fermentation action of the gas-utilizing bacterium, particularly a microorganism having a metabolic pathway of acetyl COA. Among the gas-utilizing bacteria, the genus Clostridium is more preferable, and Clostridium autoethanogenum is particularly preferable, but the bacterium is not limited thereto. Further examples will be given below.

Gas-utilizing bacteria include both eubacteria and archaebacteria. Examples of the eubacterium include, for example, Clostridium genus bacteria, Moorella genus bacteria, Acetobacterium genus bacteria, Carboxydocella genus bacteria, Rhodopseudomonas genus bacteria, and Eubacterium. (Eubacterium) bacterium, Butyribacterium (Butyribacterium) genus bacterium, Oligotropha (Oligotropha) genus bacterium, Bradyrhizobium (Bradyrhizobium) genus bacterium, and aerobic hydrogen-oxidizing bacterium Ralsotonia genus bacterium and the like.

On the other hand, examples of archaea include Methanobacterium, Methanobrevibacter, Methanocalculus, Methanococcus, Methanosarcina, Methanosphaera, Methanothermobacter, Methanothrix, Methanoculleus, Methanofollis, Methanogenium. Bacteria, Methanospirillium genus bacterium, Methanosaeta genus bacterium, Thermococcus genus bacterium, Thermofilum genus bacterium, Arcaheoglobus genus bacterium and the like can be mentioned. Among these, as archaea, Methanosarcina genus bacterium, Methanococcus genus bacterium, Methanothermobacter genus bacterium, Methanothrix genus bacterium, Thermococcus genus bacterium, Thermofilum genus bacterium, Archaeoglobus genus bacterium are preferable.

Further, since the archaea are excellent in assimilating carbon monoxide and carbon dioxide, Methanosarcina genus bacteria, Methanothermobactor genus bacteria or Methanococcus genus bacteria are preferable, and Methanosarcina genus bacteria or Methanococcus genus bacteria are particularly preferable. Specific examples of the bacterium of the genus Methanosarcina include Methanosarcina barkeri, Methanosarcina mazei, Methanosarcina acetivorans and the like.

From the above gas-utilizing bacteria, a bacterium having a high ability to produce a target organic substance is selected and used. For example, the gas-utilizing bacteria with high ethanol-producing ability include Clostridium autoethanogenum, Clostridium ljungdahlii, Clostridium aceticum, and Clostridium carboxidivorans. , Moorella thermoacetica, Acetobacterium woodii, and the like. Among these, Clostridium autoethanogenum is particularly preferable.

The medium used when culturing the above-mentioned microorganism (seed) is not particularly limited as long as it has a suitable composition according to the bacterium, and water as the main component and nutrients dissolved or dispersed in this water (for example, vitamins, And a phosphoric acid). The composition of such a medium is adjusted so that the gas-utilizing bacteria can grow well. For example, when the Clostridium genus is used as the microorganism, reference can be made to, for example, “0097” to “0099” in US Patent Application Publication No. 2017/260552.

The organic substance-containing liquid obtained by the microbial fermentation step can be obtained as a suspension containing a microorganism, a carcass thereof, a protein derived from the microorganism, and the like. The protein concentration in the suspension varies depending on the type of microorganism, but is usually 30 to 1000 mg/L. The protein concentration in the organic substance-containing liquid can be measured by the Kjeldahl method.

<Separation process>
The organic substance-containing liquid obtained by the microbial fermentation process is then subjected to a separation process. In the present invention, the organic substance-containing liquid is heated to room temperature to 500° C. under the condition of 0.01 to 1000 kPa (absolute pressure) to obtain a liquid or solid component containing microorganisms and a gas component containing organic substances. Separate (see Figure 2). In the conventional method, the organic substance-containing liquid obtained by the microbial fermentation step was distilled and the desired organic substance was separated and purified, but since the organic substance-containing liquid contains microorganisms and proteins derived from microorganisms, etc. However, if the organic substance-containing liquid is distilled as it is, foaming may occur in the distillation apparatus and continuous operation may be hindered. Further, it is known to use a membrane evaporator as a method for purifying an effervescent liquid, but the membrane evaporator has a low concentration efficiency and is not suitable for purifying a liquid containing a solid component. In the present invention, before separating and purifying a desired organic substance from the organic substance-containing liquid obtained by the microbial fermentation step by a distillation operation or the like, the organic substance-containing liquid is heated, and a liquid or solid component containing microorganisms and organic The organic substance is separated into a gas component containing a substance, and a desired organic substance is separated and purified only from the separated gas component containing an organic substance. By performing the separation step, foaming does not occur in the distillation apparatus during the distillation operation at the time of separating and purifying the organic substance, so that the distillation operation can be continuously performed. Further, since the concentration of the organic substance contained in the gas component containing the organic substance becomes higher than the concentration of the organic substance in the liquid containing the organic substance, the organic substance is efficiently separated and purified in the purification step described later. be able to.

In the present invention, from the viewpoint of efficiently separating a liquid or solid component containing a microorganism, a carcass thereof, a protein derived from the microorganism, and the like, and a gas component containing an organic substance, preferably from 10 to 200 kPa, The organic substance-containing liquid is preferably under the conditions of 50 to 150 kPa, more preferably under normal pressure, preferably at a temperature of 50 to 200° C., more preferably at a temperature of 80° C. to 180° C., further preferably at a temperature of 100 to 150° C. Heating.

The heating time in the separation step is not particularly limited as long as a gas component can be obtained, but from the viewpoint of efficiency or economy, it is usually 5 seconds to 2 hours, preferably 5 seconds to 1 hour, and more preferably It is preferably 5 seconds to 30 minutes.

The above-mentioned separation step is particularly preferable as long as it is an apparatus capable of efficiently separating the organic substance-containing liquid into a liquid or solid component (microorganisms or carcasses, proteins derived from microorganisms, etc.) and a gas component (organic substance) by heat energy. It can be used without limitation, for example, it is possible to use a drying device such as a rotary dryer, a fluidized bed dryer, a vacuum dryer, a conduction heating dryer, etc., but particularly an organic substance-containing liquid having a low solid component concentration. From the viewpoint of efficiency in separating the liquid or solid component from the liquid component into the gas component, it is preferable to use the conduction heating type dryer. Examples of the conduction heating type dryer include a drum type dryer and a disk type dryer.

<Liquefaction process>
The liquefaction step is a step of liquefying the gas component containing the organic substance obtained in the above separation step by condensation (see FIG. 2). The apparatus used in the liquefaction process is not particularly limited, but it is preferable to use a heat exchanger, particularly a condenser (condenser). Examples of the condenser include a water-cooled type, an air-cooled type, an evaporation type, and the like, and among them, the water-cooled type is preferable. The condenser may have a single stage or a plurality of stages.

It can be said that it is preferable that the liquefaction obtained by the liquefaction step does not contain the components contained in the organic substance-containing liquid such as a microorganism or a carcass thereof and a protein derived from the microorganism. It does not exclude that the thing contains protein. Even when a protein is contained in the liquefaction product, its concentration is preferably 40 mg/L or less, more preferably 20 mg/L or less, further preferably 15 mg/L or less.

The heat of condensation of the gas component obtained by the condenser may be reused as a heat source in the purification step described later. By recycling the heat of condensation, organic substances can be efficiently and economically produced.

<Refining process>
Next, an organic substance is purified from the liquefaction product obtained in the liquefaction process (see FIG. 2). The organic substance-containing liquid obtained in the microbial fermentation step can be supplied to the purification step without the above-described separation step when components such as microorganisms have already been removed. The purification step is a step of separating the organic substance-containing liquid obtained in the liquefaction process into a distillate liquid having a higher concentration of the target organic substance and a bottom liquid having a lower concentration of the target organic substance. (See Figure 2). The apparatus used in the purification step is, for example, a distillation apparatus, a processing apparatus including a pervaporation membrane, a processing apparatus including a zeolite dehydration membrane, a processing apparatus for removing a low boiling point substance having a lower boiling point than an organic substance, and a boiling point higher than an organic substance. Examples thereof include a processing device that removes high-boiling substances and a processing device that includes an ion exchange membrane. These devices may be used alone or in combination of two or more. As the unit operation, heat distillation or membrane separation may be suitably used.

In the heating distillation, a desired organic substance can be obtained as a distillate with a high purity by using a distillation apparatus. The temperature inside the distiller during the distillation of the organic substance (particularly ethanol) is not particularly limited, but is preferably 100° C. or lower, more preferably about 70 to 95° C. By setting the temperature in the still in the above range, the required organic substance and other components can be separated, that is, the organic substance can be distilled more reliably.

The pressure in the distillation apparatus during the distillation of the organic substance may be atmospheric pressure, but is preferably less than atmospheric pressure, more preferably about 60 to 95 kPa (absolute pressure). By setting the pressure in the distillation apparatus within the above range, it is possible to improve the separation efficiency of the organic substance, and thus improve the yield of the organic substance. Depending on the kind of the desired organic substance, the yield (concentration of ethanol contained in the distillate after distillation) when the obtained organic substance is ethanol is preferably 90% by mass or more, It is preferably 95% by mass or more.

In the membrane separation, a known separation membrane can be appropriately used, and for example, a zeolite membrane can be preferably used.

The concentration of the organic substance contained in the distillate separated in the purification step is preferably 20% by mass to 99.99% by mass, more preferably 60% by mass to 99.9% by mass.
On the other hand, the concentration of the organic substance contained in the bottom liquid is preferably 0.001% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass.

The bottoms separated in the refining step are substantially free of nitrogen compounds. In the present invention, "substantially free" does not mean that the concentration of the nitrogen compound is 0 ppm, and the bottom liquid obtained in the refining process does not require a wastewater treatment process. Means a compound concentration. In the separation step, rather than purifying the desired organic substance from the organic substance-containing liquid obtained in the microbial fermentation step, the organic substance-containing liquid is a liquid or solid component containing a microorganism and an organic substance as described above. Separated into the gas components contained. At that time, since the nitrogen compound remains on the liquid or solid component side containing the microorganism, the gas component containing the organic substance contains almost no nitrogen compound. Therefore, it is considered that the bottom product obtained when purifying an organic substance from a liquefied product obtained by liquefying a gas component does not substantially contain a nitrogen compound. Even when the bottom liquid contains a nitrogen compound, the concentration of the nitrogen compound is 0.1 to 200 ppm, preferably 0.1 to 100 ppm, and more preferably 0.1 to 50 ppm.

Further, for the same reason as above, the bottom liquid separated in the purification step does not substantially contain a phosphorus compound. In addition, "substantially free" does not mean that the concentration of the phosphorus compound is 0 ppm, and the concentration of the phosphorus compound is such that the bottom liquid obtained in the purification step does not require the wastewater treatment step. Means there is. Even when the bottom liquid contains a phosphorus compound, the concentration of the phosphorus compound is 0.1 to 100 ppm, preferably 0.1 to 50 ppm, more preferably 0.1 to 25 ppm. Thus, according to the method of the present invention, the bottoms discharged in the purification step of the organic substance are substantially free of nitrogen compounds and phosphorus compounds, and almost free of other organic substances. Since it is considered that there is no such wastewater, the conventionally required wastewater treatment process can be simplified.

<Wastewater treatment process>
The bottoms separated in the refining process may be supplied to the wastewater treatment process (see FIG. 2). In the wastewater treatment process, organic substances such as nitrogen compounds and phosphorus compounds can be further removed from the bottom liquid. In this step, the organic matter may be removed by anaerobically or aerobically treating the bottoms. The removed organic matter may be used as a fuel (heat source) in the refining process.

The treatment temperature in the wastewater treatment step is usually 0 to 90°C, preferably 20 to 40°C, more preferably 30 to 40°C.

Since the bottom liquor obtained through the separation step has the liquid or solid components containing microorganisms removed, the waste liquor treatment etc. is more effective than the bottom liquor obtained by being directly supplied from the microbial fermentation step to the purification step. The load is reduced.

In the wastewater treatment step, the concentration of the nitrogen compound in the treated liquid obtained by treating the bottom liquid is preferably 0.1 to 30 ppm, more preferably 0.1 to 20 ppm, and further preferably 0.1 to 10 ppm. It is particularly preferable that no nitrogen compound is contained. The concentration of the phosphorus compound in the treatment liquid is preferably 0.1 to 10 ppm, more preferably 0.1 to 5 ppm, still more preferably 0.1 to 1 ppm, and the bottom liquid contains no phosphorus compound. Is particularly preferable.

<Organic substances and their uses>
Examples of the organic substance obtained by the production method according to the present invention include methanol, ethanol, 2,3-butanediol, acetic acid, lactic acid, isoprene, butadiene and the like, and preferably an alcohol or diol having 1 to 6 carbon atoms. More preferably, it contains an alcohol or diol having 1 to 4 carbon atoms, and even more preferably ethanol. The use of the organic substance obtained by the production method of the present invention is not particularly limited. The produced organic substance can be used, for example, as a raw material for plastics, resins, etc., or can be used as various solvents, bactericides, or fuels. High-concentration ethanol can be used as a fuel ethanol mixed with gasoline and the like, and can also be used as an additive for cosmetics, beverages, chemical substances, raw materials such as fuel (jet fuel), and foods. Extremely high

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

[Example 1]
A pressure swing adsorption device was filled with a new (unused) zeolite adsorbent containing LSX-type zeolite as a main component. The specific surface area of this zeolite adsorbent was 877 m ² /g as a result of measurement by the BET method using nitrogen gas.

Next, a synthesis gas containing hydrogen gas, nitrogen gas, carbon monoxide gas, and carbon dioxide gas as main components, which is discharged from the gasification furnace, is prepared, and the synthesis gas is supplied to the pressure swing adsorption device, The carbon dioxide gas was adsorbed on the zeolite adsorbent to purify the synthetic gas. After purifying the synthesis gas over a long period of time, the zeolite adsorbent in the pressure swing adsorption apparatus has a specific surface area of 685 m ² /g by the BET method using nitrogen gas (converted to the unused zeolite adsorbent in terms of specific surface area). (−21.9%), the supply of synthesis gas was stopped and the used zeolite adsorbent was recovered from the pressure swing adsorption device.

Subsequently, the recovered zeolite adsorbent was fired at a temperature of 400° C. in an oxygen atmosphere. After no carbon dioxide was detected in the exhaust gas stream, the calcination was stopped to obtain a regenerated zeolite adsorbent. The specific surface area of the regenerated zeolite adsorbent was 837 m ² /g (measured by BET method using nitrogen gas) (specific surface area conversion to unused zeolite adsorbent was -4.6%).

When the regenerated zeolite adsorbent obtained as described above was filled in a pressure swing adsorption device and reused as an adsorbent, the adsorption performance was stably exhibited, and the composition of the purified synthesis gas was stable. Was.

Then, the purified synthetic gas was supplied to the microbial fermentation tank, and through the microbial fermentation process, the separation process, the liquefaction process, and the purification process, the organic substance could be finally obtained efficiently.

[Comparative Example 1]
After collecting the used zeolite adsorbent from the pressure swing adsorber, a new (unused) zeolite adsorbent was used in the pressure swing adsorber instead of the regenerated zeolite adsorbent. Was not stable, and the composition of the purified synthesis gas was not stable. Therefore, after that, the purified synthetic gas was supplied to the microbial fermentation tank, but the efficiency of microbial fermentation was reduced, and the yield of the final organic substance was also reduced.

Claims (12)

A synthesis gas containing hydrogen gas, nitrogen gas, carbon monoxide gas and carbon dioxide gas as main components, which is discharged from the gasification furnace, is supplied to adsorb carbon dioxide gas in the synthesis gas, and A method for regenerating a zeolite adsorbent used in a pressure swing adsorption device for reducing a carbon gas concentration,
A step of collecting the used zeolite adsorbent from the pressure swing adsorption device,
A step of regenerating the zeolite adsorbent by firing the zeolite adsorbent in an oxygen atmosphere, and a step of using the regenerated zeolite adsorbent again as an adsorbent of a pressure swing adsorption device,
Equipped with
Zeolite adsorbent, in which the used zeolite adsorbent is calcined until it reaches -15.0 to -1.0% in terms of specific surface area by BET method using nitrogen gas with respect to unused zeolite adsorbent How to reuse. The used zeolite adsorbent has a carbon compound and a sulfur compound attached to the pores in the zeolite crystal structure, and has a surface area of −15 relative to that of the unused zeolite calculated by BET method using nitrogen gas. The method according to claim 1, which is 0.0% or more. The method according to claim 1, wherein the syngas discharged from the gasification furnace contains a tar component. The method according to any one of claims 1 to 3, wherein the zeolite is an LSX type zeolite. A regenerated adsorbent comprising a burned material of a used zeolite adsorbent,
Carbon compounds and sulfur compounds are attached to the pores in the zeolite crystal structure,
A regenerated adsorbent having a specific surface area of -15.0 to -1.0% based on the unused zeolite, which is calculated by the BET method using nitrogen gas. The regenerated adsorbent according to claim 5, wherein the zeolite is LSX type zeolite. A method for producing an organic substance by microbial fermentation from a synthesis gas containing carbon monoxide,
A synthetic gas purification step of reducing the carbon dioxide gas concentration in the synthetic gas by using the regenerated adsorbent according to claim 5 or 6;
Supplying a synthetic gas obtained by the synthesis gas purification step to a microbial fermentation tank, a microbial fermentation step of obtaining an organic substance-containing liquid by the microbial fermentation,
A separation step in which the organic substance-containing liquid is heated to room temperature or higher to 500° C. under a condition of 0.01 to 1000 kPa to separate into a liquid or solid component containing a microorganism and a gas component containing an organic substance;
A liquefaction step of liquefying by condensing the gas component obtained by the separation step,
A purification step of purifying an organic substance from the liquefaction product obtained by the liquefaction step,
A method for producing an organic substance, comprising: The method according to claim 7, wherein the heat of condensation generated in the liquefaction process is reused as a heat source when purifying an organic substance from the organic substance-containing liquid. 9. The method according to claim 7 or 8, wherein the synthesis gas is obtained by gasifying a carbon source. The method according to claim 9, wherein the carbon source is waste. The method according to any one of claims 7 to 10, wherein the organic substance contains an alcohol having 1 to 6 carbon atoms. An organic substance obtained by the method according to claim 7.

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