JP5600250B2 - Fuel gas purification method and fuel gas purification system - Google Patents

Description

  The present invention relates to a method for purifying a fuel gas obtained by anaerobic fermentation or thermal decomposition of an organic substance, and also relates to a fuel gas purification system capable of performing the purification method.

When biogas obtained by anaerobic methane fermentation of sewage and industrial wastewater is used in gas consuming equipment such as fuel cells, RX gas generation facilities, gas engine generators, etc., it is necessary to highly remove biogas impurities There is. Examples of impurities to be removed include carbon dioxide and siloxane. Carbon dioxide is desirably 0.5% or less in order to use a fuel cell, an RX gas generation facility, and the like without any trouble. In addition, siloxane is desirably 0.5 mg / m ³ N or less as an example for using a gas engine or the like without any trouble.

  As a method of removing these simultaneously, there is a technique of absorbing with high-pressure water as in Patent Document 1 below. In addition, there are the following Non-Patent Document 1 and Non-Patent Document 2 as experimental examples in which biogas is purified using a technique of absorbing with high-pressure water.

JP 2008-63393 A

The Japan Sewerage Association, 44th Sewerage Research Presentation Lectures (2007), p. 853 P. 868

However, in Non-Patent Document 1, as shown in Table 3, FIG. 3, and FIG. 4, the methane concentration is not as high as 88.4% to 97.1%, and particularly the water temperature is 29. When the temperature is higher than or equal to ℃, the temperature is greatly reduced (92.0% at 29 ° C, 88.4% at 29.5 ° C, 85.6% at 34 ° C). The reason for this is that “the increase in water temperature has caused the solubility of the gas to decrease, and more carbon dioxide (CO ₂ ) is not absorbed”. That is, it is appropriate to consider the carbon dioxide (CO ₂ ) concentration of the purified gas at a level of several percent to several tens percent.

Moreover, in the said nonpatent literature 2, as shown in FIG. 2, it becomes 0.8 mg / m < ³ > N at the maximum in the siloxane concentration range in actual digestion gas (biogas), for example, is used as a fuel of a gas engine In this case, it is not maintained at a level of 0.5 mg / m ³ N or less that can be used as safely as natural gas. Therefore, since there is a risk of damage to the gas engine, a siloxane removal device is separately required to avoid this.
That is, in the technology using high-pressure water disclosed in Patent Document 1, Non-Patent Documents 1 and 2, there is a limit to the methane concentration that can be reached, and there is room for improvement regarding siloxane removal.
The purpose of the present application is to obtain a purification method capable of highly efficiently purifying a fuel gas obtained by anaerobic fermentation or pyrolysis of an organic substance with a relatively simple equipment configuration. To obtain a purification system to be implemented.

The characteristic configuration of the fuel gas purification method according to the present invention for achieving the above object is as follows:
A method for purifying a fuel gas obtained by anaerobic fermentation or pyrolysis of organic matter,
In a state where the liquefied natural gas flows in the fin tube of the finned tube heat exchanger, the fuel gas before purification is led out of the finned tube of the finned tube heat exchanger, and the fuel gas flows outside the finned tube, Along with the impurity concentration control of the fuel gas by temperature control of the fuel gas located near the outlet of the finned tube heat exchanger, the impurities in the fuel gas before purification are condensed using the cold heat of the liquefied natural gas. , Performing an impurity treatment step of removing the impurities from the pre-purification fuel gas as a solid or liquid, and separating and recovering the gas from which the impurities have been removed as a purified fuel gas in the impurity treatment step And recovering natural gas vaporized by heat exchange with the pre-refining fuel gas ,
After performing the impurity treatment step, the supply of the pre-refining fuel gas and the liquefied natural gas to the finned pipe heat exchanger is stopped, and the impurities are placed outside the finned pipe of the finned pipe heat exchanger. The method includes a regeneration step of introducing a regeneration gas having a vaporizing temperature, bringing the regeneration gas into contact with impurities on the fin surface, vaporizing, and releasing or collecting the regeneration gas separately from the purified fuel gas and removing it from the fin surface. It is in.

According to said characteristic structure, although liquefied natural gas (LNG) is a very low temperature of -140 degreeC--160 degreeC depending on a pressure, anaerobic fermentation or thermal decomposition of organic substance is utilized by using the cold heat. By doing so, it is possible to condense impurities in the fuel gas obtained and remove them as solid or liquid.
In other words, carbon dioxide, siloxane, moisture, oil, and hydrocarbons other than methane, which are impurities in fuel gas obtained by anaerobic fermentation of organic matter, can be sufficiently removed, and the purity of methane can be increased. is there.
In addition, carbon dioxide, moisture, oil, hydrocarbons other than methane, which are impurities in the fuel gas obtained by thermally decomposing organic matter, can be removed, and hydrogen, carbon monoxide, The purity of methane can be increased.
Furthermore, when liquefied natural gas exchanges heat with fuel gas, the sensible heat of the fuel gas and the latent heat generated during the condensation of impurities can be used as a heating source for vaporizing the liquefied natural gas. It can be used effectively. Therefore, when carrying out this method for purifying fuel gas, for example, in a vaporized natural gas manufacturing plant where a conventional liquefied natural gas vaporization facility is installed, fuel is used instead of seawater that has been used for conventional vaporization. If gas is used, vaporization of liquefied natural gas and purification of biogas derived from biological treatment can be realized in the same process.

  According to the above characteristic configuration, the fin tube heat exchanger is used, LNG is flowed into the fin tube, and fuel gas is flowed outside the fin tube, so that the impurities are condensed and adhered to the fin surface. it can. That is, impurities can be attached to the fin surface and removed from the pre-purification fuel gas, and the remaining gas can be recovered as a purified fuel gas. Here, the finned tube heat exchanger can take a large surface area for heat exchange between impurities and liquefied natural gas, and the thickness of the solid or liquid material attached to the fins as the heat transfer surface can be reduced. Since the size can be reduced, it is possible to prevent the heat transfer characteristics from being deteriorated due to the deposits. As a result, impurities can be efficiently removed for a long time. Further, since the heat exchange between the fuel gas and the LNG can be indirectly performed, a problem such as accumulation of impurities in the LNG that occurs in the case of the direct heat exchange in which the fuel gas flows through the LNG does not occur.

According to the above characteristic configuration, a regeneration gas at a temperature (relatively high temperature) that vaporizes impurities in a solid or liquid state after performing an impurity treatment step for condensing and adhering impurities to the fin surface. To prevent the heat transfer characteristics from deteriorating due to excessive thickness of impurities attached to the fin surface by performing a step of vaporizing and removing the solid or liquid material on the fin surface by flowing It is possible to maintain a high impurity removal rate.
In addition, it is preferable to use a plurality of fin tube type mature exchangers. As a result, the impurities in the fuel gas are condensed using the cold heat of liquefied natural gas (LNG) and removed as a solid or liquid substance, and a high temperature regeneration gas is allowed to flow for a predetermined time to obtain a solid on the fin surface. The step of vaporizing and removing the solid or liquid can be performed simultaneously.

  A further characteristic configuration of the fuel gas purification method according to the present invention is that the temperature of the purified fuel gas processed in the impurity processing step is measured, and the impurity processing is performed so that the measured temperature is below a certain level. The point is that at least one of the flow rate of the pre-purification fuel gas and the flow rate of the liquefied natural gas to be processed in the process is adjusted.

  When the impurities are condensed and removed by heat exchange as in the present method, the temperature of the refined fuel gas rises as the amount of heat transferred by the heat exchanger increases. Here, in view of the fact that the composition of the fuel gas and the composition of the liquefied natural gas are stable, such an increase in temperature is considered to be a pre-planned purification amount of the fuel gas and the liquefied natural gas as a cold heat source. This means that the balance with the amount is lost, and the degree of purification (composition) of the recovered refined fuel gas is changed. Therefore, the temperature of the fuel gas processed in the impurity processing step is measured, and at least one of the flow rate of the fuel gas processed in the impurity processing step and the flow rate of LNG is adjusted so that the temperature becomes a certain level or less. Thus, the concentration of the specific impurity in the fuel gas can be managed so as not to rise above a predetermined level. For this purpose, it is preferable to grasp in advance the relationship between the temperature of the fuel gas and the concentration of a specific impurity in the fuel gas. As a preferable temperature condition, for example, when processing a fuel gas at an atmospheric pressure level, and taking the concentration of carbon dioxide as an example, in order to make the concentration of carbon dioxide 1% or less, it is maintained at −125 ° C. or less, To make it 0.5% or less, keep it at -130 ° C or less.

  In addition, the product gas production method according to the present invention has a characteristic configuration in which the fuel gas purification method is executed, and heat exchange between the purified fuel gas separated and recovered after the impurities are removed and the pre-purification fuel gas is performed. The product is obtained by mixing the natural gas which is vaporized and recovered by the above process.

According to the above characteristic configuration, the fuel gas derived from bio, which is obtained from the purified fuel gas from which the impurity component is removed and the natural gas that has been vaporized is obtained in the same process, and these gases are further mixed. By adjusting the amount of heat, a product gas having a desired property can be easily obtained.
Furthermore, since the calorific value of the refined fuel gas can be brought close to the calorific value of natural gas, it is possible to use the natural gas consuming equipment as it is or to add it to the calorific value adjustment so that it can be used as it is. The amount of fuel used (for example, propane and butane) can be reduced.
Further, since the concentration of impurities in the natural gas is low, there is an effect that the impurity concentration of the product gas is smaller than that of the refined fuel gas.

Further, the characteristic configuration of the fuel gas purification system according to the present invention for achieving the above object is as follows:
A fuel gas purification system for purifying fuel gas obtained by anaerobic fermentation or pyrolysis of organic matter,
A heat exchanger having a fuel gas flow path through which fuel gas flows in one flow path of the heat transfer surface, and a natural gas flow path through which natural gas flows in the other flow path of the heat transfer surface;
The fuel gas channel includes a fuel gas introduction unit that introduces a pre-purification fuel gas, and a fuel gas deriving unit that derives a refined fuel gas purified in the fuel gas channel,
The natural gas flow path comprises a natural gas introduction part for introducing liquefied natural gas, and a natural gas lead-out part for deriving natural gas vaporized in the natural gas flow path,
The fuel gas flowing through the fuel gas flow path, with the impurity concentration control of the fuel gas by temperature control of the fuel gas located near the outlet of the heat exchanger,
Impurities in the pre-purification fuel gas are condensed by heat exchange by cold heat of the liquefied natural gas, and are attached to the surface of the heat transfer surface of the heat transfer surface as a solid or liquid material, thereby exchanging the heat. In a configuration that works as an impurity treatment unit,
An impurity separation / recovery mechanism for separating and collecting the solid or liquid matter attached to one of the heat transfer surfaces separately from the refined fuel gas ;
The heat exchanger is constituted by a finned tube heat exchanger, the inside of the finned tube of the finned tube type heat exchanger is the natural gas flow path, and the outside of the finned tube of the finned tube type heat exchanger is the fuel gas. Configured as a flow path,
In addition to the fuel gas introduction unit, the fin tube heat exchanger vaporizes the regeneration gas introduction unit for introducing the regeneration gas at a temperature for vaporizing the impurities to the outside of the fin tube. An impurity deriving unit that releases or collects gas containing impurities is provided separately from the fuel gas deriving unit, and the impurity separation and recovery mechanism is configured .

According to said characteristic structure, fuel gas refinement | purification which concerns on this application is carried out by carrying out heat exchange between both gas by flowing the liquefied natural gas to the other through the fuel gas before refinement | purification on the other side on both sides of a heat-transfer surface. The method can be implemented to perform fuel gas purification and natural gas vaporization.
Moreover, according to said characteristic structure, the isolation | separation collection | recovery of the impurity adhering to the said heat-transfer surface can also be performed in refinement | purification of fuel gas.

  According to the above characteristic configuration, a general-purpose finned pipe heat exchanger is employed, and purification of the fuel gas and vaporization of the natural gas can be executed by using the inside and outside of the fin pipe as a natural gas flow path and a fuel gas flow path, respectively. .

  According to the above characteristic configuration, by flowing the regeneration gas through the regeneration gas flow path, impurities can be vaporized from the heat transfer surface, and the purification function of the heat exchanger can be recovered.

  A further characteristic configuration of the fuel gas purification system according to the present invention includes a fuel gas temperature measurement unit that measures the temperature of the purified fuel gas, and the purified fuel gas measured by the fuel gas temperature measurement unit A flow rate of the liquefied natural gas, or a flow rate of the liquefied natural gas that adjusts a flow rate of the pre-purification fuel gas that performs impurity treatment in the impurity treatment portion so that a temperature of It is in the point provided with at least any one of the liquefied natural gas flow volume adjustment part which adjusts.

  According to the above characteristic configuration, the apparatus obtains the operations and effects obtained by controlling the temperature of the fuel gas to be equal to or lower than a predetermined temperature described in the fuel gas purification method. Can do. That is, it can be managed so that the concentration of the specific impurity in the fuel gas does not rise above a predetermined level.

  Further, the product gas production system according to the present invention is characterized in that the refined fuel gas obtained from any one of the fuel gas purification systems and separated and recovered after the impurities are removed, and the pre-purification fuel gas, A gas mixing and adjusting system is provided on the downstream side of the fuel gas purification system to obtain a product gas by mixing the natural gas which is vaporized and recovered by heat exchange.

According to the above-described characteristic configuration, the purified fuel gas from which the impurity component is removed and the vaporized natural gas, which are bio-derived fuel gas described in the method for producing the product gas, are used in the same process. Thus, by further mixing these gases and adjusting the amount of heat, it is possible to obtain an effect and effect that a product gas having a desired property can be easily obtained in the apparatus.
In addition, the amount of heat of the refined fuel gas can be brought close to the amount of heat of natural gas, so that it is possible to use the natural gas consumer device as it is, or to add to the heat amount adjustment so that it can be used as it is. The effect that the amount of fuel used (for example, propane and butane) can be reduced, and the concentration of impurities in natural gas is low, the effect that the impurity concentration of the product gas is smaller than that of purified fuel gas, Can be obtained in the apparatus.

1 is a configuration diagram showing an embodiment of a fuel gas purification system according to the present invention. It is detail drawing which shows the structure of the fin pipe with which the heat exchanger employ | adopted as a fuel gas refinement | purification system is equipped. It is a block diagram which shows embodiment of the gas mixing adjustment system with which the fuel gas purification system which concerns on FIG. 1 is provided in the downstream. It is a figure which shows the flow of each gas in an impurity treatment process in a fuel gas purification system. It is a figure which shows the flow of each gas in a regeneration process in a fuel gas purification system. It is a block diagram which shows embodiment which gave the structure which reverses the flow direction of the fuel gas in an impurity treatment process in a fuel gas refinement | purification system.

The equipment introduced in the present application includes a gas mixing adjustment system 2 for gas heat quantity shown in FIG. 3 on the downstream side of the fuel gas purification system 1 shown in FIG.
The fuel gas purification system 1 is a system that purifies organic fuel gas using the cold heat of liquefied natural gas. By operating the fuel gas purification system 1, the purified fuel from which impurities have been removed Gas BG2 can be obtained, and vaporized natural gas NG2 that has been warmed and vaporized by donating cold for removing impurities can be obtained.
In the gas mixing adjustment system 2, the refined fuel gas BG2 and the vaporized natural gas NG2 are received from the fuel gas purification system 1, the both gases are mixed, and the amount of LPG added is controlled by the LPG calorific value adjustment device. As a result, the product gas GS having a heat quantity within a predetermined heat quantity range can be obtained.

Hereinafter, the fuel gas purification system 1 and the gas mixing adjustment system 2 will be described in this order.
[Configuration of fuel gas purification system]
FIG. 1 is a configuration diagram of a fuel gas purification system 1 according to the present invention.
In the fuel gas purification system 1 according to the present application, since the fuel gas is purified by the cold heat held by the liquefied natural gas, the heat exchanger 12 that performs heat exchange between the two gases is used as a core and the high temperature of the heat exchanger 12 is increased. The fuel gas system and the natural gas system are connected to the side channel and the low temperature side channel, respectively. Here, the heat exchanger 12 condenses the impurities in the pre-purification fuel gas BG1 by heat exchange by the cold heat of the liquefied natural gas NG1, and the fuel gas flow path side surface of the heat transfer surface as a solid or liquid material It has the structure which can be made to adhere and remove. That is, the heat exchanger 12 serves as the impurity treatment unit 11 in the fuel gas purification system.
Furthermore, the heat exchanger 12 according to the present application is provided with an impurity separation / recovery mechanism 30 that separates and collects solid matter or liquid matter adhering to the heat transfer surface separately from the vaporized natural gas NG2.

  In the present application, the fuel gas purification unit 10, the impurity treatment unit 11, and the heat exchanger 12 substantially refer to the heat exchanger 12, but the expression “fuel gas purification unit 10” is used to purify the fuel gas. The expression “impurity treatment unit 11” refers to the heat exchanger 12 in terms of the functional unit that processes the impurities in the fuel gas. The expression “vessel 12” means that “a heat exchanger is practically used as an apparatus for purifying fuel gas” or that “refining fuel gas” is performed by “heat exchange”. The heat exchanger 12 is captured.

[Functional structure related to impurity treatment]
As can be seen from FIG. 1, the heat exchanger 12 has a configuration in which a fuel gas system and a natural gas system are connected to each other.
In the fuel gas system, on the upstream side of the heat exchanger 12, a carry-in portion that receives fuel gas from the most upstream side, a flow meter FM110 that measures the flow rate of the carried fuel gas, and the amount of fuel gas that flows through the flow path are adjusted. A flow rate adjustment valve V110 and a dehumidifying device 105 for removing moisture in the fuel gas are provided. A heater 160 is provided on the downstream side of the heat exchanger 12. The pre-purification fuel gas BG1 referred to in the present application flows upstream from the heat exchanger 12, and the purified fuel gas BG2 flows downstream.

  The natural gas system includes a liquefied natural gas tank 201 on the upstream side of the heat exchanger 12, and is configured so that liquefied natural gas can be introduced into the heat exchanger 12 from the tank 201. On the downstream side of the heat exchanger 12, a hot water vaporizer 260, a flow meter FM260, and a flow rate adjustment valve V270 that opens and closes the flow path and adjusts the flow rate according to the flow rate measured by the flow meter FM260 are provided. As shown in FIG. 1, part of the liquefied natural gas discharged from the liquefied natural gas tank 201 is vaporized by the heat exchanger 12 to become a natural gas in a gaseous state, and is completely vaporized by the hot water vaporizer 260. .

[Configuration related to impurity separation and recovery]
As can be seen from FIG. 1, the heat exchanger 12 has a configuration in which a nitrogen gas system that performs separation and recovery of impurities, which is a regeneration process of the heat exchanger, is further connected.
In the nitrogen gas system, a PSA type nitrogen gas generator 301 that generates nitrogen gas from the most upstream side is provided upstream of the heat exchanger 12. On the downstream side of the heat exchanger 12, an impurity derivation unit 350 that discharges a mixed gas of vaporized impurities and nitrogen gas is provided.

  As shown in FIG. 1, the fuel gas purification system 1 according to the present application includes a hot water boiler 303 that works using the refined fuel gas BG2 as a fuel. Using the hot water generated by the hot water boiler 303, A heat exchanger 304 for heating the outside air for heating the air supplied to the heat exchanger 12 is provided, and is used for vaporization in the hot water vaporizer 260 provided on the downstream side of the heat exchanger 12 of the natural gas system. , And the heater 160 provided on the downstream side of the heat exchanger 12 of the fuel gas system can be used for heating. In FIG. 1, reference numeral 302 denotes a blower for sending air to the heat exchanger 304 for heating the outside air.

Hereinafter, individual devices (particularly heat exchangers) will be described in more detail.
In the fuel gas purification system 1 according to the present application, as shown in FIG. 1 and FIG. 2, the heat exchanger 12 is constituted by a finned tube heat exchanger, and the finned tube 12a of the finned tube heat exchanger is made natural. A natural gas passage 230 forming a part of the gas system is formed, and the fin pipe heat exchanger outside the fin pipe is configured as a fuel gas passage 130 of the fuel gas system.

  That is, the heat exchanger 12 according to the present application includes a fuel gas flow path 130 through which fuel gas flows in one flow path of the heat transfer surface, and a natural gas flow path 230 through which natural gas flows in the other flow path of the heat transfer surface. The fuel gas introduction part 110 for introducing the pre-purification fuel gas BG1 into the fuel gas flow path 130, and the fuel gas lead-out part 150 for deriving the refined fuel gas BG2 purified in the fuel gas flow path 130. A natural gas introduction part 210 for introducing liquefied natural gas NG1 into the natural gas flow path 230, and a natural gas deriving part 250 for deriving vaporized natural gas vaporized in the natural gas flow path 230. It is prepared and configured. Therefore, the fuel gas and the liquefied natural gas exchange heat in an indirect form.

  In addition, the heat exchanger 12 is a part of a nitrogen gas system in which the regeneration gas RG having a temperature for vaporizing the impurities 12z in a solid or liquid state is allowed to flow to the heat transfer surface in a heat transferable state. A regeneration gas flow path 330 is provided.

  Therefore, the heat exchanger 12 is provided with a regeneration gas introduction part 310 connected to the fuel gas flow path 130 separately from the fuel gas introduction part 110, and a regeneration gas lead-out part connected to the fuel gas flow path 130. (Impurity deriving unit) 350 is provided separately from the fuel gas deriving unit 150, and in this heat exchanger 12, the supply of the pre-purification fuel gas BG 1 from the fuel gas introducing unit 110 is stopped from the regeneration gas introducing unit 310. While the regeneration gas RG is introduced into the fuel gas channel 130 and the regeneration gas RG in the fuel gas channel 130 is derived from the regeneration gas deriving unit 350, the fuel gas channel 130 becomes the regeneration gas channel 330. It is configured as follows.

  By adopting the above configuration, an impurity removal operation state in which the fuel gas is caused to flow through the fuel gas passage 130 to remove the impurities 12z from the pre-purification fuel gas BG1, and the regeneration gas RG is caused to flow through the fuel gas passage 130 to form a solid. A regeneration operation state in which impurities 12z in a state of being attached to the surface of the heat transfer surface of the heat transfer surface as a solid or liquid material are vaporized and derived from a regeneration gas deriving unit (impurity deriving unit) 350, The flow direction of the fuel gas with respect to the heat transfer surface and the flow direction of the regeneration gas are the same direction.

  Further, as can be seen from FIG. 1, the fuel gas temperature measuring unit T150 for measuring the temperature of the refined fuel gas BG2 is provided, and the temperature of the fuel gas measured by the fuel gas temperature measuring unit T150 is set in advance. A flow rate adjusting valve V110, which is a fuel gas flow rate adjusting unit that adjusts the flow rate of the fuel gas that performs impurity processing in the heat exchanger 12 that is the impurity processing unit 11, so that the temperature is equal to or lower than a certain temperature, includes a flow meter FM110 and a dehumidifying device. 105 is provided. The flow control valve V110 is controlled by the flow controller CTR110.

The above is the description of the schematic configuration of the fuel gas purification system 1 according to the present application. Hereinafter, the configuration and operation mode will be described in more detail.
The fuel gas BG1 to be purified is stored, for example, in a fuel gas cylinder (not shown) that is not included in the fuel gas purification system 1 according to the present invention. The pre-purification fuel gas BG1 introduced from the fuel gas cylinder passes through the pre-purification fuel gas flow rate control valve V110 and the dehumidifier 105, and then through a valve V120 that can be controlled to open and close, and then the fuel gas flow path in the heat exchanger 12 130.

  That is, the pre-purification fuel gas flow control valve V110 controls the flow rate of the pre-purification fuel gas BG1 to the fuel gas purification unit 10. The pre-purification fuel gas flow rate control valve V110 is controlled by a pre-purification fuel gas flow rate controller CTR110, and the pre-purification fuel gas flow rate controller CTR110 maintains the impurity removal performance of the fuel gas purification unit 10. The temperature of the fuel gas in the vicinity of the outlet (fuel gas deriving unit 150) of the fuel gas purification unit 10 is measured, and before purification using the pre-purification fuel gas flow rate control valve V110 so that the temperature becomes −135 ° C. or less. The flow rate of the fuel gas BG1 is controlled. For this reason, a thermometer T150 for measuring the fuel gas is installed in the vicinity of the fuel gas deriving unit 150 of the fuel gas purification unit 10.

The dehumidifier 105 removes moisture in the pre-purification fuel gas BG1. By removing moisture in the pre-purification fuel gas BG1 before introduction into the impurity treatment unit 11, the amount of water adhering to the fins of the heat exchanger 12 can be reduced. Thereby, (i) the risk of blockage of the fuel gas upstream of the flow of the fuel gas can be reduced, (ii) the deterioration of the heat transfer characteristics of the fin is suppressed, and (iii) It is possible to reduce the accumulation amount when the moisture becomes liquid in the regeneration process and accumulates at the bottom of the heat exchanger 12.

Then, the structure of the heat exchanger 12 which is the fuel gas refinement | purification part 10 is demonstrated.
The fuel gas purification unit 10 includes a fuel gas introduction unit 110 that is an introduction unit to the fuel gas purification unit 10 and a flow of the fuel gas introduced from the fuel gas introduction unit 110 in the fuel gas purification unit 10 in order from the upstream. A fuel gas flow path 130 that is also a part of the heat exchanger 12, and a fuel gas deriving unit 150 that deducts the purified fuel gas BG2 purified in the fuel gas flow path 130 out of the fuel gas purification unit 10. They are configured and connected in this order.

  Further, from the viewpoint of the equipment configuration, the fuel gas purification unit 10 includes a heat exchanger 12 that constitutes the impurity processing unit 11, and includes four fin tubes 12a and a storage container 12b for the fin tubes 12a. It is composed of The heat exchanger 12 is configured so that impurities can be removed by performing heat exchange between the medium in the fin tube and the medium outside the fin tube by the fin tube 12a.

  FIG. 2 specifically shows the fin tube 12a in this embodiment. As shown in FIG. 2, the fin tube 12a includes an inlet collecting tube 12i and an outlet collecting tube 12o, and four fin tubes 12a joined to the inlet collecting tube 12i and the outlet collecting tube 12o. As shown in FIG. 2, each fin tube 12a is composed of one heat transfer tube 12c and eight fins 12d fixed to the heat transfer tube 12c at an equal angle. In the present embodiment, the heat exchanger 12 is made of an aluminum alloy, and the medium inside the fin tube and the medium outside the fin tube exchange heat due to the thermal conductivity of the aluminum alloy.

  In this embodiment, as shown in FIG. 2, the liquefied natural gas NG1 that is a cooling medium flows in the fin tube (heat transfer tube), and the fuel gas to be purified flows outside the fin tube. The liquefied natural gas NG1, which is a cooling medium, flows in the fin tube, but since the fin tube 12a is made of an aluminum alloy having high thermal conductivity, the cold heat of the liquefied natural gas NG1 is a fin fixed to the heat transfer tube. Impurities 12z in the pre-purification fuel gas BG1 flowing to the outside of the fin tube are condensed by the cold heat of the liquefied natural gas NG1 flowing through the heat transfer tube, and are liquefied and solidified to form the fin tube 12a, that is, the heat transfer tube. It adheres to 12c and fin 12d. As a result, the impurities 12z in the fuel gas BG1 flowing outside the fin pipe are removed, and the fuel gas BG1 is purified.

  That is, in the present embodiment, the fuel gas flow path 130 in the fuel gas purification unit 10 corresponds to a portion outside the fin tube 12 a of the heat exchanger 12 in the storage container 12 b of the heat exchanger 12. That is, the pre-refining fuel gas BG1 introduced into the storage container 12b from the fuel gas introduction unit 110 is brought into contact with the heat exchanger 12 in the storage container 12b, which is the fuel gas flow path 130, thereby passing through the fin tube 12a. Heat exchange with the passing natural gas NG1 is performed and purified as described above.

Returning to FIG. 1, the downstream configuration of the fuel gas purification unit 10 will be described.
The fuel gas outlet 150 is connected downstream to the heater 160 through a valve that can be opened and closed. Further, the downstream of the heater 160 is configured to be connectable to a device for measuring the impurity concentration and a detection tube.

The warmer 160 brings the purified fuel gas BG2 having a low temperature by heat exchange for removing impurities in the fuel gas refining unit 10 closer to room temperature prior to supply to the demand point.
In addition, the device for measuring the concentration of impurities connected to the downstream of the heater 160 and the detector tube enable confirmation of the quality of the refined fuel gas BG2 supplied to the demand point and control based on the quality. Therefore, quality is measured and detected.

  That is, in the present embodiment, the refined fuel gas BG2 derived from the fuel gas deriving unit 150 is brought close to normal temperature by the heater 160, and then the quality is confirmed before being provided to the consumer. It has a possible configuration.

Next, the configuration of the fuel gas purification system 1 according to the present invention will be described along the flow of natural gas that is a cooling medium.
The cryogenic liquefied natural gas NG1 used as a cooling medium is received from the liquefied natural gas tank 201. The liquefied natural gas NG1 is introduced into the natural gas flow path 230 in the fuel gas purification unit 10 by the natural gas introduction unit 210. The fuel gas purification unit 10 can be led to the outside through the natural gas deriving unit 250, and the hot water vaporizer 260 connected downstream of the natural gas deriving unit 250 and the downstream of the hot water vaporizer 260. Is connected to the outside of the fuel gas purification system 1 according to the present invention via a vaporized natural gas flow meter FM260 and a vaporized natural gas flow rate control valve V270 connected to.

  In the present embodiment, the natural gas flow path 230 in the fuel gas purification unit 10 corresponds to the heat transfer tube 12c of the fin tube 12a. Further, the heat exchange performed in the heat exchanger 12 of the impurity processing unit 11 is as described above based on FIG. That is, when the liquefied natural gas NG1 introduced from the natural gas introduction section 210 into the heat exchanger 12, that is, the finned pipe heat exchanger, flows through the heat transfer pipe 12c, which is the natural gas flow path 230, the fin tube material is used. Due to the thermal conductivity of the aluminum alloy, heat exchange is performed with the pre-purification fuel gas BG1 outside the fin tube. Then, it passes through the natural gas flow path 230 and is led out of the heat exchanger 12 from the natural gas lead-out part 250.

  That is, in the fuel gas refining system 1 according to the present invention, the fuel gas to be purified and the natural gas as the cooling medium are respectively in the heat exchanger storage container 12b and the fin tube 12a of the heat exchanger 12 in the heat exchange process. It is configured to pass through physically separated flow paths. Since the heat exchange is indirectly performed in such a separated configuration, there is no problem such as mixing of impurities into the natural gas, which occurs in the case of direct heat exchange in which the fuel gas flows into the natural gas. .

Further, the hot water carburetor 260 connected to the downstream of the natural gas deriving unit 250 through the valve V260 capable of opening and closing control is used for the liquefied natural gas NG1 and the vaporized natural gas NG2 derived from the fuel gas purification unit 10. Of these, all the liquefied natural gas NG1 that has not been vaporized is vaporized.
That is, a part of the liquefied natural gas NG1 introduced into the natural gas flow path 230 is vaporized by heat exchange with the fuel gas in the natural gas flow path 230 to become a vaporized natural gas NG2. Without being vaporized, the liquefied natural gas NG1 is led out of the fuel gas purification unit 10 from the natural gas deriving unit 250. Therefore, by connecting a hot water vaporizer 260 downstream of the fuel gas purification unit 10, all the natural gas derived from the fuel gas purification unit 10 is vaporized, and all is made into vaporized natural gas.

  Then, the natural gas NG2 that has been completely vaporized via the hot water vaporizer 260 is controlled in flow rate via the vaporized natural gas flow meter FM260 and the vaporized natural gas flow control valve V270, and the fuel gas purification system 1 according to the present invention. It is configured to be provided externally.

  In the fuel gas purification system 1 according to the present invention, if the amount of carbon dioxide, which is an impurity in the fuel gas attached to the fin tube 12a, increases, the heat conduction performance of carbon dioxide is significantly worse than that of the fin 12d. The heat transfer characteristics of the vessel 12 are lowered, and the ability to remove impurities as a solid is gradually lowered. In this case, the system of the present application separates and collects the solid or liquid impurities attached to the fin tube 12a separately from the vaporized natural gas NG2 by the impurity separation and recovery mechanism 30, thereby Regenerate impurity removal performance.

The impurity separation / recovery mechanism 30 includes (i) a function of purging the inside of the fuel gas purification unit 10 with nitrogen gas, and (ii) heating in order to separate and recover solid or liquid impurities attached to the fin tube 12a. The introduced air is introduced into the fuel gas purification unit 10 to raise the temperature of the heat exchanger 12 and vaporize impurities adhering to the fin tube 12a.

Therefore, the impurity separation and recovery mechanism 30 introduces (i) nitrogen gas for purging the inside of the fuel gas purification unit 10 and (ii) heated air for vaporizing impurities into the fuel gas purification unit 10. A regenerative gas introduction unit 310 is provided. In addition, the impurity separation and recovery mechanism 30 includes a regeneration gas flow path 330 that flows the regeneration gas in a state where heat can be transferred to the impurities in the fuel gas purification unit 10, and the impurities separated by the regeneration gas in the fuel gas purification unit 10. An impurity lead-out part 350 leading out is provided.

Further, the impurity separation / recovery mechanism 30 includes (i) nitrogen gas for purging the inside of the fuel gas purification unit 10 and (ii) heated air for vaporizing impurities, upstream of the regeneration gas introduction unit 310. Are introduced into the fuel gas purification unit 10 as follows: (i) a PSA-type nitrogen gas generator 301 that generates nitrogen gas used as a regeneration gas; and (ii) heating to vaporize impurities. A blower 302 that takes in the outside air, a heat exchanger 304 for heating the outside air for heating the taken-in outside air, and a hot water boiler 303 for providing heat to the heat exchanger 304 for heating the outside air. ing.
Further, (i) the PSA type nitrogen gas generator 301, (ii) the blower 302, the heat exchanger 304 for heating the outside air, and the hot water boiler 303 can each be controlled to open and close upstream of the regeneration gas introduction unit 310. They are connected in parallel through various valves. Further, with respect to the equipment constituting (ii), the blower 302 and the hot water boiler 303 are connected in parallel upstream of the outdoor air heating heat exchanger 304.

  The impurity deriving unit 350 is configured to be able to release or collect impurities through a valve V360 that can be controlled to open and close.

[Fuel gas purification operation]
Next, the fuel gas refining operation in this embodiment will be described with reference to FIG.
In FIG. 4 which is a conceptual diagram showing the state of the gas flow path as a premise, the introduction of the fuel gas to be purified and the natural gas to be the cooling medium into the fuel gas purification unit 10 is shown. And valves V110, V120, V160, V210, V260, and V270 related to the fuel gas introducing unit 110, the natural gas introducing unit 210, the fuel gas deriving unit 150, and the natural gas deriving unit 250, which are the deriving units, are opened. On the other hand, the valves V310, V320, and V360 related to the regeneration gas introduction unit 310 and the impurity extraction unit 350, which are the introduction unit and the extraction unit of the impurity separation / recovery mechanism 30, are closed (black symbols). ).

The fuel gas BG1 to be purified in this example is a gas produced by simulating digestion gas obtained by anaerobic fermentation of sewage sludge. For example, methane 60%, carbon dioxide 40%, decamethylcyclopentasiloxane. It is composed of 80 mg / m ³ N, oxygen 0.06%, and nitrogen 1.4%, and is supplied from a fuel gas cylinder (not shown) connected to the fuel gas purification system 1 according to the present invention.

In the present embodiment, the flow rate of the pre-purification fuel gas BG1 is controlled by the pre-purification fuel gas flow rate control valve V110 upstream of the fuel gas purification unit 10. Specifically, the flow rate of the pre-refining fuel gas BG1 is controlled to be an average of 0.21 m ³ N / h.
This is to control the flow rate of the pre-purification fuel gas BG1 to be purified upstream of the fuel gas purification unit 10 so that the concentration of specific impurities in the refined fuel gas does not rise above a predetermined value. Is. As a preferable temperature condition, for example, when processing a fuel gas at an atmospheric pressure level, and taking the concentration of carbon dioxide as an example, in order to reduce the concentration of carbon dioxide to 1% or less, it is maintained at −125 ° C. or lower. In order to make it 0.5% or less, it is necessary to keep it at −130 ° C. or less. In this embodiment, the flow rate of the pre-purification fuel gas BG1 is controlled so that the temperature of the purified fuel gas BG2 measured by the fuel gas purification unit thermometer T150 is −135 ° C. or lower.

In the present embodiment, the moisture of the pre-purification fuel gas BG1 is removed by the dehumidifier 105 before being introduced into the fuel gas purification unit 10. Specifically, the temperature of the fuel gas at the inlet of the dehumidifying device 105 is 25 ° C., which is the same as the room temperature, and the humidity is about 67%, but the fuel gas is cooled by the dehumidifying device 105 and the moisture in the fuel gas is reduced to 8 ° C. Dehumidified to saturation. As a result, the amount of water in the fuel gas is reduced to about half.
In the purification of the fuel gas, the pre-purification fuel gas BG1 is introduced into the fuel gas purification unit 10 from the fuel gas introduction unit 110 through the moisture removal.

On the other hand, the liquefied natural gas NG1 used as a cooling medium in this embodiment is a gas having a temperature of about −145 ° C., and is supplied from a natural gas cylinder as the liquefied natural gas tank 201. The natural gas cylinder 201 uses a commonly used LNG portable container having a volume of 175 L.
The delivery of the liquefied natural gas NG1 is performed by increasing the internal pressure of the LNG portable container to about 0.2 MPa by a method normally used and pushing out the liquefied natural gas NG1. The flow rate is 1.5 m ³ N / h in terms of natural gas after vaporization.
In the purification of the fuel gas, the delivered liquefied natural gas NG1 is introduced into the fuel gas purification unit 10 from the natural gas introduction unit 210.

  The mechanism of fuel gas purification by heat exchange between the fuel gas and the natural gas in the impurity treatment unit 11 and the heat exchanger 12 after introduction into the fuel gas purification unit 10 is as described above with reference to FIG. is there.

  The refined fuel gas BG2 purified by the fuel gas purification unit 10 is led out of the fuel gas purification unit 10 from the fuel gas deriving unit 150, and is heated to room temperature by a heater 160 installed downstream of the fuel gas deriving unit 150. The temperature is increased to about 25 ° C. In the present embodiment, the warmer 160 uses hot water as a heat source.

The refined fuel gas BG2 heated by the warmer 160 is measured for impurity concentration by an impurity concentration measuring device installed downstream of the warmer 160.
In this example, the impurity concentration is (i) for carbon dioxide, oxygen and nitrogen, gas chromatograph using a TCD detector, and (ii) for decamethylcyclopentasiloxane, the sampling gas is absorbed in hexane, Analysis was performed with a gas chromatograph mass spectrometer, and (iii) water was measured by a commonly used measurement method of measurement with a dew point meter.
As a result, the impurity concentration of the refined fuel gas BG2 after the temperature rise in this example is such that the carbon dioxide concentration is 0.5% or less, decamethylcyclopentasiloxane is 0.5 mg / m ³ N or less, and the dew point of moisture is -30 ° C or lower, oxygen average 0.1%, nitrogen average 2.3%, and the impurity concentration is problematic even when used in major gas consuming equipment such as gas engines, gas turbines, hot water boilers, steam boilers, etc. There was no low enough level.

In the present embodiment, a hot water vaporizer 260 is installed downstream of the fuel gas purification unit 10 for the mixed gas of the liquefied natural gas NG1 and the vaporized natural gas NG2 derived from the fuel gas purification unit 10, and passes through this. Thus, after the vaporized natural gas NG2 is completely vaporized, the flow rate is controlled and provided outside the fuel gas purification system 1 according to the present invention.
In the present embodiment, a hot water boiler 303 is adopted as a heat source of the hot water vaporizer 260, and hot water at 80 ° C. is supplied. The flow rate of the vaporized natural gas NG2 is measured by a vaporized natural gas flow meter FM260 installed downstream of the hot water vaporizer 260, and vaporized so that the flow rate of the vaporized natural gas NG2 is 1.5 m ³ N / h. It is controlled by a natural gas flow rate control valve V270.

  In the present embodiment shown in FIG. 4, in the impurity treatment unit 11, the direction in which the fuel gas flows and the direction in which the natural gas flows are drawn in the same direction with respect to the fin tube. As shown in FIG. 6, a fuel gas purification system having a configuration capable of flowing the fuel gas in the reverse direction is provided, and in the middle of the impurity treatment process, the flow direction of the fuel gas is opposite to the direction in which the gas has been flown so far. A fuel gas purification method may be employed.

  By adopting the above configuration and method, it is avoided that the amount of solid matter adhering to the fins 12d in the impurity treatment step becomes extremely large upstream of the flow of the fuel gas having a high impurity concentration in the fuel gas. Therefore, the problem that the passage of the fuel gas is narrowed or blocked in some cases when the impurity treatment step is completed can be solved.

[Mixed refined fuel gas and natural gas]
FIG. 3 is a configuration diagram showing a gas mixing adjustment system 2 provided on the downstream side of the fuel gas purification system 1.
The gas mixing adjustment system 2 includes a refined fuel gas BG2 obtained by the fuel gas purification system 1, and a natural gas NG2 used for heat exchange with the impurities in the fuel gas purification system 1 and recovered by evaporation. Are mixed in such a ratio that the amount of heat of the obtained product gas becomes the amount of heat within a predetermined heat amount range to obtain the product gas GS.

Hereinafter, based on FIG. 3, the apparatus structure of the gas mixing adjustment system 2 is demonstrated.
The gas mixing and adjusting system 2 is a mechanism for mixing the refined fuel gas BG2 and the natural gas NG2 that have been refined by the fuel gas purification system 1, and the refined fuel gas is added to the flow path 710 of the refined fuel gas BG2. A flow meter FM610 that measures the flow rate of BG2, a flow meter FM620 that measures the flow rate of natural gas NG2 in the flow path 720 of natural gas NG2, and a natural gas flow rate control downstream of the flow meter FM620 of natural gas NG2 Valve V610 is installed. Then, the refined fuel gas BG2 and the natural gas NG2 are mixed downstream of the natural gas flow control valve V610. The mixing ratio of the refined fuel gas BG2 and the natural gas NG2 is adjusted by adjusting the flow rate of the natural gas NG2 by the natural gas flow rate control valve V610.

A first static mixer 630 is installed downstream of the mixed portion of the refined fuel gas BG2 and the natural gas NG2 in order to increase the uniformity of the mixed state, and the pressure fluctuation and the amount of heat fluctuation are suppressed downstream thereof. A first cushion tank 640 is installed.
A flow meter FM 710 for measuring the flow rate of the mixed fuel gas is set downstream of the first cushion tank 640, an LPG calorific value adjustment device 710 is set downstream thereof, and a second static mixer 730 is set downstream thereof. ing. A mixed fuel gas calorie measuring device 720 and a second cushion tank 740 are installed downstream of the second static mixer 730, and an odorizing device 810 is installed downstream of the second cushion tank 740. Odor is given by odorant.
The calorific value adjustment mixed gas GS odorized by the odorizing device 810 is connected to the city gas conduit 910 and the user so as to be supplied to the demand point.

Next, the gas mixing heat amount adjustment in the present embodiment will be described with reference to FIG.
The gas mixing adjustment system 2 measures the flow rates of the refined fuel gas BG2 and the natural gas NG2 with the flow meters FM610 and FM620 based on the above-described device configuration. In this embodiment, the measured value of the flow meter FM610 is measured with the flow meter. The flow rate of the natural gas NG2 is controlled by the natural gas flow rate control valve V610 so that the flow rate of the natural gas NG2 is 12 times the flow rate of the refined fuel gas BG2. For example, in this embodiment, the purified spent fuel gas BG2 about 0.13 m ³ N / h, as natural gas NG2 is to be approximately 1.5 m ³ N / h, and controls the flow rate.

  The gas mixing adjustment system 2 of the present embodiment uses the first static mixer 630 to improve the uniformity of the mixed state of the mixed fuel gas obtained as described above. The static mixer may be a general one. Thereafter, the mixed fuel gas exiting the first static mixer 630 is passed through the first cushion tank 640 to suppress the pressure fluctuation and the calorific value fluctuation range. In the present embodiment, the volume of the first cushion tank 640 is 30L.

  The mixed fuel gas that has exited the first cushion tank 640 passes through the flow meter FM 710, and propane gas is added by the LPG calorific value adjustment device 710 to adjust the calorific value. The amount of heat is adjusted by measuring the flow rate of the mixed fuel gas with the flow meter FM 710 and after adjusting the amount of heat, the second static mixer 730 described later, and the amount of heat of the fuel adjusted mixed gas after increasing the uniformity of the mixed state Based on the measured value by the calorific value measuring device 720 (that is, the calorific value measuring device 720 measures the calorific value of the fuel adjustment mixed gas downstream of the second static mixer 730) so that the calorific value is within a predetermined range. Do. In the present embodiment, the predetermined range is 44.3 J / m 3 N to 45.9 MJ / m 3 N on the assumption of city gas injection. A general LPG heat quantity adjusting device 710 is used.

Further, the heat adjustment mixed gas can be improved in the uniformity of the mixed state by the second static mixer 730 (Note that the fuel adjusted mixed gas after the second static mixer 730 has been improved in the uniformity of the mixed state) As described above, the calorific value is measured with the calorimeter 720. And this-application gas mixing adjustment system 2 suppresses a pressure fluctuation and a calorie | heat amount fluctuation range by letting the mixed fuel gas which came out of the 2nd static mixer 730 pass to the 2nd cushion tank 740.
In addition, in this embodiment, the calorie-adjusted mixed gas obtained as described above is odorized with an odorant for safety. A general-purpose odorant is selected. As the odorant, a general odorizer 810 is used.

  Further, the oxygen and nitrogen concentrations are measured for the calorie-adjusted mixed gas exiting the second cushion tank 740. As a measuring method, a gas chromatograph method using a commonly used TCD detector is used. Concentrations of oxygen and nitrogen in the calorie adjusting mixed gas are 0.008% on average for oxygen and 0.18% on average for nitrogen.

  Since it is known that the concentration of oxygen and nitrogen in natural gas is very small, the concentration of oxygen and nitrogen before and after mixing natural gas with purified fuel gas BG2 is the same as that of natural gas and purified fuel gas BG2. The flow rate magnification is 12 times, and the concentration level is reduced to 1/13. As a result, as described above, the temperatures of oxygen and nitrogen are examples of reference values determined by the gas company when used by being injected into the city gas conduit 910 "Oxygen 0.01% or less, nitrogen 1 % ”Or less, and the heat adjustment mixed gas can be injected into the city gas conduit 910.

However, before actually injecting into the city gas conduit 910, it is preferable to measure the gas composition and the odorant concentration of the calorie adjustment mixture downstream of the second cushion tank 740. For example, in the case where the reference value of the user such as gas consuming equipment or the injection into the city gas conduit 910 with respect to the concentration of oxygen and nitrogen is strict, in order to more reliably satisfy the reference value, the measured values of these concentrations The flow rate ratio between the natural gas and the purified fuel gas may be adjusted using the flow meter FM610, the flow meter FM620, and the flow control valve V610.
Furthermore, with respect to other specific impurities, when the reference value of the usage destination such as injection into the gas consuming equipment or the city gas conduit 910 is strict, natural gas and refined fuel are similarly based on the measured concentration values of the impurities. The reference value can be satisfied by adjusting the gas flow rate ratio using the flow meter FM610, the flow meter FM620, and the flow control valve.

[Regeneration of the fuel gas purification section]
FIG. 5 is a conceptual diagram showing how the fuel gas purification unit 10 is regenerated in the fuel gas purification system 1 according to the present invention. Hereinafter, a regeneration method of the fuel gas purification unit 10 will be described with reference to FIG.

  The regeneration of the fuel gas purification unit 10 includes (1) purging the fuel gas purification unit 10 with nitrogen gas, (2) vaporizing impurities adhering to the fin tube with heated air, and (3) refining the fuel gas with nitrogen gas. (1) to (5), purging the inside of the unit 10, (4) purging the fuel gas flow path with fuel gas, and (5) cooling the heat exchanger (natural gas flow path) with a small amount of liquefied natural gas. It is realized by performing in order. Hereinafter, each of (1) to (5) will be described.

(1) Purge in the fuel gas purification unit 10 with nitrogen gas In the steps (1) to (3) in which the fuel gas purification unit 10 is regenerated, in order to avoid mixing fuel gas into the fuel gas purification unit 10, FIG. As shown in FIG. 5, the fuel gas introduction valve V120, the natural gas introduction valve V210, and the fuel gas outlet valve V160, which are the introduction parts of the fuel gas to the fuel gas purification unit 10, are closed.

In the purge process in the fuel gas purification unit 10 using nitrogen gas, after the valve is closed, the nitrogen gas introduction valve V310 and the impurity derivation valve V360 are opened, and the PSA nitrogen gas generator 301 is operated. As a result, the nitrogen gas generated by the PSA nitrogen gas generator 301 is released or collected from the PSA nitrogen gas generator 301 to the fuel gas purification unit 10, from the fuel gas purification unit 10 to the impurity deriving unit 350, and from the impurity deriving unit 350. The fuel gas remaining in the fuel gas purification unit 10 is purged outside the fuel gas purification unit 10.
The purging process is intended to improve the safety of the subsequent vaporization process of the impurities by the heated air, and the fuel gas remaining in the fuel gas purification unit 10 is removed with chemically stable nitrogen gas. Derived outside the fuel gas purification unit 10.

(2) Vaporization of impurities adhering to the fin tube by heated air In the vaporization processing of impurities, after purging the fuel gas purification unit 10 with the nitrogen gas, the fuel gas purification unit uses the heated air as the regeneration gas RG. By introducing into the fin 10, the impurities adhering to the fin tube 12 a are vaporized by the temperature rise of the fin tube 12 a, and are led out of the fuel gas purification unit 10 from the impurity deriving unit 350.

  The flow path of the heated air opens the heated air introduction valve V320, thereby allowing the outside air heated via the outside air heat exchanger 304 to be introduced into the fuel gas purification unit 10. Further, the impurity derivation valve V360 is opened after the purge process so that the impurities vaporized by the heated air introduced into the fuel gas purification unit 10 can be derived. This enables the fuel gas purification system 1 according to the present invention to take in the outside air from the blower 302 and to derive impurities from the impurity deriving unit 350.

  The heated air introduced into the fuel gas purification unit 10 takes outside air into the outside air heat exchanger 304 by the blower 302, and the taken outside air is heated and heated by the hot water boiler 303 in the outside air heating heat exchanger 304. Produced by heating by exchange.

  The impurities 12z adhering to the fin tube 12a are vaporized by introducing the heated air generated as described above into the fuel gas purification unit 10 and raising the temperature of the heat exchanger 12. The vaporized impurities are discharged or collected from the impurity deriving unit 350. In addition, the temperature of heated air has the preferable range of 30 to 70 degreeC.

(3) Purging the fuel gas purification unit 10 again with nitrogen gas After the impurities 12z are vaporized with the heated air, the PSA nitrogen gas generator 301 is operated again, and the fuel gas purification unit 10 with nitrogen gas is operated again. Purge inside. This is because the purged impurities 12z remaining in the fuel gas purification unit 10 without being purged only by the introduction of heated air are purged out of the fuel gas purification unit 10 with chemically stable nitrogen gas. is there.

(4) Purging the fuel gas channel with fuel gas After purging the fuel gas purification unit 10 again with nitrogen gas, the fuel gas channel 130 is purged with the fuel gas NG1. In this purge process, the fuel gas introduction valve V120 and the impurity derivation valve V360 are opened, and the fuel gas derivation valve V160 is closed. If the opening and closing of the valve is controlled in this way, the fuel gas introduced into the fuel gas channel 130 is derived from the impurity deriving unit 350 instead of the fuel gas deriving unit 150. This is to prevent the fuel gas used for the purge from being erroneously derived from the fuel gas purification unit 10 as the refined fuel gas BG2.
In this process, the regeneration of the fuel gas purification unit 10 is completed by completing the subsequent step (5), and the fuel gas purification can be restarted. Therefore, when the fuel gas purification is restarted, This is to prevent the nitrogen gas that has flowed during the regeneration from remaining in the fuel gas channel 130. That is, this process is a process of purging nitrogen gas remaining in the fuel gas flow path 130 with the fuel gas.

(5) Cooling of the heat exchanger (natural gas flow path) with a small amount of liquefied natural gas After purging the fuel gas flow path 130 with the fuel gas, the fuel gas introduction valve V120 is closed and the fuel gas flows into the fuel gas flow. After making it the state which does not flow in the path 130, the liquefied natural gas introduction valve V210 is opened, and the heat exchanger 12 is cooled by flowing a small amount of liquefied natural gas through the heat transfer pipe 12c (in the fin pipe). This is because the heat exchanger 12 whose temperature has been raised during the removal of impurities is cooled to prepare for the resumption of fuel gas purification after the end of regeneration. The reason why the fuel gas introduction valve V120 is closed prior to the cooling process is that the fuel gas does not flow through the fuel gas flow path 130. This is to guarantee that it will not be.

  Through the steps (1) to (5), the regeneration of the fuel gas purification unit 10 is completed. After the regeneration is completed, the pre-purification fuel gas BG1 and the liquefied natural gas NG1 are flowed again to the fuel gas purification unit 10 to purify the fuel gas.

In the regeneration of the fuel gas purification unit 10 described above, the following is more preferable.
(I) As an index for performing the regeneration process of the fuel gas purification unit 10, that is, as an index for detecting that the amount of the impurity 12z adhering to the fin 12d has increased and the performance of removing the impurity 12z has decreased, An increase in the flow rate or the temperature of the refined fuel gas in the vicinity of the fuel gas outlet 150 may be detected.
(Ii) In the latter half of the time for flowing heated air in “(2) Vaporization of impurities adhering to the fin tube by heated air”, the temperature of the heated air is set to a low temperature of about 30 ° C. to 50 ° C., for example. Good. As a result, the temperature of each part in the fuel gas purification unit 10 at the end of heating can be lowered, so that “(5) Cooling of heat exchanger (natural gas flow path) with a small amount of liquefied natural gas” can be When the gas NG1 is flowed, the amount of cold heat required for cooling the fin tube 12a can be reduced.

Moreover, the following is also considered as another embodiment.
(Iii) Instead of the PSA-type nitrogen gas generator 301, a nitrogen cylinder can be used.
(Iv) In the above embodiment, regarding the liquefied natural gas used as a cold heat source in removing impurities, an ordinary liquefied natural gas is assumed, and the properties thereof are not particularly described. In other words, any liquefied natural gas was used regardless of its origin and production area.
On the other hand, in the present invention, the purified fuel gas obtained by the fuel gas purification system and the vaporized natural gas used as a cold heat source are mixed, and the product gas is obtained after adjusting the calorific value. If the amount of heat is adjusted in advance in the state of liquefied natural gas, the load for adjusting the amount of heat can be reduced or eliminated.
In this configuration, for liquefied natural gas that is mixed with purified fuel gas after use for impurity removal and is planned to be used for production of product gas, the liquefied natural gas that is the raw material is heated in advance to vaporize the methane. By reducing the concentration or adding liquefied petroleum gas, the amount of heat of the liquefied natural gas is increased.
Thus, the calorific value of the product gas can be increased by increasing the calorific value of the liquefied natural gas. Further, even when the product gas is produced by adjusting the amount of heat, the amount of liquefied petroleum gas (propane, butane, etc.) required for adjusting the amount of heat locally can be greatly reduced.
The fuel gas purification system or product gas production system of the present invention can be adopted in a city gas production plant that imports liquefied natural gas from overseas to produce city gas, etc., and is generally a small-scale inland fuel gas. It can also be adopted in a fuel gas production facility (for example, a gas station) provided with a (biogas) production facility. In the latter case, liquefied natural gas and liquefied petroleum gas are transported to a gas station by a tank lorry and supplied to a gas storage tank of a gas station in an urban area. However, transportation of liquefied gas requires transportation costs, so it would be very expensive to transport both gases to the site.However, if only liquefied natural gas with a high calorific value as described above is transported to the gas station, there is a problem. It becomes possible to compress the transportation cost etc. which become and to reduce the manufacturing cost of product gas.

  The fuel gas purification system and the product gas production system of the present invention have been described based on the embodiments. However, the present invention is not limited to the configurations described in the above embodiments, and does not depart from the spirit thereof. The structure can be changed as appropriate.

  According to the present invention, by utilizing the cold heat of liquefied natural gas, impurities in the fuel gas obtained by anaerobic fermentation or pyrolysis of organic matter are condensed and removed as solid or liquid matter. A fuel gas purification method and system can be provided.

DESCRIPTION OF SYMBOLS 1 Fuel gas refinement | purification system 2 Gas mixing adjustment system 10 Fuel gas refinement | purification part 11 Impurity treatment part 12 Heat exchanger 12a Fin pipe 12z Impurity 110 Fuel gas introduction part 130 Fuel gas flow path 150 Fuel gas extraction part 210 Natural gas introduction part 230 Natural Gas passage 250 Natural gas outlet 30 Impurity separation and recovery mechanism 330 Regeneration gas passage BG1 Pre-purification fuel gas BG2 Refined fuel gas NG1 Liquefied natural gas NG2 Vaporized natural gas RG Regeneration gas V110 Pre-purification fuel gas flow control valve T150 Fuel gas Refiner thermometer CTR110 Fuel gas flow controller before purification

Claims (6)

A method for purifying a fuel gas obtained by anaerobic fermentation or pyrolysis of organic matter,
In a state where the liquefied natural gas flows in the fin tube of the finned tube heat exchanger, the fuel gas before purification is led out of the finned tube of the finned tube heat exchanger, and the fuel gas flows outside the finned tube, Along with the impurity concentration control of the fuel gas by temperature control of the fuel gas located near the outlet of the finned tube heat exchanger, the impurities in the fuel gas before purification are condensed using the cold heat of the liquefied natural gas. , Performing an impurity treatment step of removing the impurities from the pre-purification fuel gas as a solid or liquid, and separating and recovering the gas from which the impurities have been removed as a purified fuel gas in the impurity treatment step And recovering natural gas vaporized by heat exchange with the pre-refining fuel gas ,
After performing the impurity treatment step, the supply of the pre-refining fuel gas and the liquefied natural gas to the finned pipe heat exchanger is stopped, and the impurities are placed outside the finned pipe of the finned pipe heat exchanger. Including a regeneration step of introducing a regeneration gas at a vaporizing temperature, bringing the regeneration gas into contact with impurities on the fin surface, vaporizing, releasing or collecting the regeneration gas separately from the refined fuel gas, and removing it from the fin surface; A fuel gas refining method. The temperature of the refined fuel gas treated in the impurity treatment step is measured, and the flow rate of the pre-purification fuel gas treated in the impurity treatment step and the liquefied natural gas are treated so that the measured temperature is below a certain level. 2. The fuel gas purification method according to claim 1, wherein at least one of the gas flow rates is adjusted. The fuel gas purification method according to claim 1 or 2 is executed,
A method for producing a product gas, wherein a product gas is obtained by mixing the refined fuel gas separated and recovered after the impurities are removed and the natural gas vaporized and recovered by heat exchange with the fuel gas before purification. A fuel gas purification system for purifying fuel gas obtained by anaerobic fermentation or pyrolysis of organic matter,
A heat exchanger having a fuel gas flow path through which fuel gas flows in one flow path of the heat transfer surface, and a natural gas flow path through which natural gas flows in the other flow path of the heat transfer surface;
The fuel gas channel includes a fuel gas introduction unit that introduces a pre-purification fuel gas, and a fuel gas deriving unit that derives a refined fuel gas purified in the fuel gas channel,
The natural gas flow path comprises a natural gas introduction part for introducing liquefied natural gas, and a natural gas lead-out part for deriving natural gas vaporized in the natural gas flow path,
The fuel gas flowing through the fuel gas flow path, with the impurity concentration control of the fuel gas by temperature control of the fuel gas located near the outlet of the heat exchanger,
Impurities in the pre-purification fuel gas are condensed by heat exchange by cold heat of the liquefied natural gas, and are attached to the surface of the heat transfer surface of the heat transfer surface as a solid or liquid material, thereby exchanging the heat. In a configuration that works as an impurity treatment unit,
An impurity separation / recovery mechanism for separating and collecting the solid or liquid matter attached to one of the heat transfer surfaces separately from the refined fuel gas ;
The heat exchanger is constituted by a finned tube heat exchanger, the inside of the finned tube of the finned tube type heat exchanger is the natural gas flow path, and the outside of the finned tube of the finned tube type heat exchanger is the fuel gas. Configured as a flow path,
In addition to the fuel gas introduction unit, the fin tube heat exchanger vaporizes the regeneration gas introduction unit for introducing the regeneration gas at a temperature for vaporizing the impurities to the outside of the fin tube. A fuel gas refining system comprising an impurity deriving unit that releases or collects a gas containing impurities separately from the fuel gas deriving unit, and the impurity separation and recovery mechanism is configured . A fuel gas temperature measuring unit for measuring the temperature of the refined fuel gas, and
The flow rate of the pre-purification fuel gas for performing impurity treatment in the impurity treatment unit is adjusted so that the temperature of the purified fuel gas measured by the fuel gas temperature measurement unit is equal to or lower than a predetermined temperature set in advance. 5. The fuel gas purification system according to claim 4 , further comprising at least one of a fuel gas flow rate adjustment unit configured to adjust or a liquefied natural gas flow rate adjustment unit configured to adjust a flow rate of the liquefied natural gas. The fuel gas purification system obtained by the fuel gas purification system according to claim 4 or 5 is vaporized and recovered by heat exchange between the refined fuel gas from which the impurities are removed and separated and recovered, and the fuel gas before purification. A product gas production system comprising a gas mixing adjustment system for mixing with natural gas to obtain a product gas on the downstream side of the fuel gas purification system.

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