JP2016120472A - Mixed gas purifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a mixed gas purifier which effectively utilizes heat generated by gas compression for lowering the relative humidity of a mixed gas to achieve high energy utilization efficiency.SOLUTION: A mixed gas purifier 1 includes: a gas compressor 2 which adiabatically compresses a mixed gas to be subject to purification; a heat exchanger 3 which recovers heat of the mixed gas adiabatically compressed by the gas compressor 2; a cooler 4 which cools the mixed gas from which heat is recovered by the heat exchanger 3; a condenser 5 which removes a moisture content of the mixed gas cooled by the cooler 4 as drain; and a separation unit 6 which separates the mixed gas flowing thereinto via the condenser 5 into a refined gas. The mixed gas flowing via the condenser 5 is heated with the heat recovered by the heat exchanger 3 to be supplied to the separation unit 6.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a mixed gas purification apparatus for purifying a mixed gas containing carbon dioxide such as biogas.

  Biogas is one of the renewable energies, and has attracted attention as a resource that may be part of energy demand. Biogas generated by methane fermentation of waste is generated when organic substances in the waste are decomposed by anaerobic microorganisms. Contains water. The component ratio of biogas varies depending on the type of waste and the fermentation conditions. For example, the ratio of methane is about 60% (volume%), and the remaining 40% is carbon dioxide. For this reason, in order to use biogas as a fuel gas, it is necessary to remove carbon dioxide from the biogas and refine it to a gas mainly composed of methane.

  Conventionally, a separation apparatus using a separation membrane or adsorption by a PSA method is used for purifying a mixed gas such as biogas. It is generally known that such a separation apparatus has a reduced separation performance when condensation occurs in the apparatus. In particular, when a separation membrane is used, if dew condensation occurs on the membrane surface, water droplets cover the separation membrane surface, resulting in a significant reduction in separation performance.

  For this reason, in the conventional mixed gas purification method, a process of lowering the relative humidity of the mixed gas is added before supplying the mixed gas to be purified to the separation device (see, for example, Patent Document 1 below). FIG. 1 shows an example of such a conventional mixed gas purification method. In this conventional example, the mixed gas is compressed by a gas compressor J1, then cooled by a cooler J2, drained of moisture (water vapor) by a condenser J3, and then heated by a heater J4, whereby a separation device J5 is obtained. The relative humidity of the supplied gas mixture is lowered.

JP-A-2005-23211

  The above-described conventional example can be expected to have a good separation performance for separating a methane-rich purified gas and a carbon dioxide-rich off-gas by supplying a mixed gas having a low relative humidity to the separation device. However, since a lot of energy is used for heating and cooling in the process before supplying to the separation device, energy is consumed for refining biogas that bears a part of energy demand, which is an improvement when considering the efficiency of energy use. There is room for. In particular, the mixed gas becomes considerably hot due to adiabatic compression by a gas compressor, but the heat is dissipated outside the system, and then heat is applied from outside the system by a heater, so efficient heat utilization is possible. There is a problem that has not been done.

  When a separation membrane is used as the separation device, the separation membrane made of a polymer material is vulnerable to heat, and the use temperature of the separation device is limited. On the other hand, in the prior art, the mixed gas is heated by the heater immediately upstream of the separation device. Therefore, if priority is given to the relative humidity of the mixed gas supplied to the separation device, the mixed gas is overheated and the separation device is heated. There is a possibility that the operating temperature limit will be exceeded, and if the heating temperature is lowered with priority given to the operating temperature limit of the separation device, the relative humidity of the mixed gas will be increased, and the separation performance will be adversely affected. For this reason, the above-described conventional example has a problem that the temperature management of the mixed gas is not performed in consideration of both the operating temperature of the separator and the relative humidity of the mixed gas.

  This invention makes it an example of a subject to cope with such a problem. In other words, by effectively using the heat generated by gas compression to lower the relative humidity of the mixed gas, it is possible to realize a mixed gas purification device with high energy use efficiency, and also the relative humidity of the mixed gas supplied to the separation device It is an object of the present invention to ensure good separation performance by using the separation device in an appropriate temperature range while lowering the temperature.

In order to achieve such an object, the mixed gas purifier according to the present invention has the following configuration.
A gas compressor that adiabatically compresses a mixed gas containing carbon dioxide gas to be purified, a heat exchanger that recovers heat of the mixed gas that is adiabatically compressed by the gas compressor, and a mixed gas that is heat-recovered by the heat exchanger A condenser for cooling the mixed gas cooled by the cooler, and a separation device for separating the mixed gas that has passed through the condenser into purified gas, and mixing via the condenser. A mixed gas purification apparatus, wherein a gas is heated by heat recovered by the heat exchanger and supplied to the separation apparatus.

The mixed gas purification apparatus having such a feature can realize a mixed gas purification apparatus with high energy use efficiency by effectively using heat generated by gas compression, and can also supply a mixed gas to the separation apparatus. Good separation performance can be secured by using the separation device in an appropriate temperature range while lowering the relative humidity.
In addition, the mixed gas which this invention makes object the mixed gas containing carbon dioxide gas, such as a natural gas well origin and landfill gas, in addition to biogas.

It is explanatory drawing of a prior art. It is explanatory drawing which showed the mixed gas purification apparatus which concerns on embodiment of this invention. It is explanatory drawing which showed the mixed gas purification apparatus which concerns on embodiment of this invention. It is explanatory drawing which showed the mixed gas purification apparatus which concerns on embodiment of this invention. It is explanatory drawing which showed the Example of the mixed gas refinement | purification apparatus of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. As shown in FIG. 2, the mixed gas purification apparatus 1 according to the embodiment of the present invention includes a gas compressor 2, a heat exchanger (first heat exchanger) 3, a cooler (second heat exchanger) 4, a condenser. 5, The separation device 6 is provided.

  The gas compressor 2 adiabatically compresses a mixed gas such as biogas (hereinafter referred to as a gas to be purified) to be purified, and the temperature of the gas to be purified increases with an increase in pressure due to this compression. The heat exchanger 3 recovers the heat of the gas to be purified which is adiabatically compressed by the gas compressor 2, cools the gas to be purified in one stage by heat exchange, and supplies the recovered gas to the separation device 6 with the recovered heat. Heat the gas to be purified.

  The cooler 4 and the condenser 5 are for further cooling the gas to be refined that has been cooled in one stage by the heat exchanger 3 to remove moisture, and the condenser 5 condenses the saturated water vapor of the cooled gas to be refined. This is a gas-liquid separator that removes drainage.

  The gas to be purified that has passed through the condenser 5 is guided to the heat exchanger 3 described above via the heat exchange flow path 10, and is adiabatically compressed by the gas compressor 2 in the heat exchanger 3, and from the gas to be purified whose temperature has risen. Heated by heat, and the gas to be purified whose relative humidity is reduced by being heated is supplied to the separation device 6.

  The separation device 6 obtains a methane-rich purified gas from the gas to be purified. For example, a separation membrane that selectively permeates carbon dioxide gas from biogas can be employed. An example of the separation membrane is a hollow tube-like membrane, and polyimide, polysulfone, cellulose acetate, polyamide, or the like is used as a constituent material thereof. The separation membrane here has a high carbon dioxide gas permeation rate and a low methane membrane permeation rate. By utilizing the difference in permeation rate, methane-rich purified gas and carbon dioxide-rich off-gas can be used. Separate effectively. The separation device 6 is not limited to a separation membrane, and may be a device that adsorbs and removes carbon dioxide gas.

  Such a mixed gas purification apparatus 1 recycles the heat generated when the gas to be purified rises in temperature when it is adiabatically compressed by the gas compressor 2 for the subsequent heating of the gas to be purified. The energy consumed by the operation of the mixed gas purification apparatus 1 is reduced by increasing the utilization efficiency of the gas. Thereby, the mixed gas refinement | purification apparatus 1 which improved the utilization efficiency of energy is realizable.

  FIG. 3 shows another embodiment of the present invention. The same parts as those described above are denoted by the same reference numerals, and redundant description is omitted. This mixed gas purification apparatus 1A includes a supply flow path 11 that supplies a gas to be purified via a condenser 5 to a separation apparatus 6, and a pressure adjustment valve 7 is provided in the supply flow path 11. The heat exchange channel 10 branches upstream of the pressure regulation valve 7 in the supply channel 11, and the heat exchange channel 10 is downstream from the pressure regulation valve 7 in the supply channel 11 via the heat exchanger 3. Meet on the side.

  According to such a mixed gas purification apparatus 1A, when the pressure adjustment valve 7 is throttled, the flow rate of the gas to be purified supplied from the condenser 5 to the separation apparatus 6 via the heat exchange flow path 10 increases, and the pressure adjustment valve 7 On the contrary, the flow rate of the purified gas supplied from the condenser 5 to the separation device 6 via the supply flow path 11 increases. Thereby, the temperature of the to-be-purified gas supplied to the separation device 6 can be adjusted by adjusting the pressure regulating valve 7.

  According to this mixed gas purification apparatus 1A, as in the above-described embodiment, the energy utilization efficiency can be improved, and the separation apparatus 6 can be appropriately operated while lowering the relative humidity of the gas to be purified supplied to the separation apparatus 6. Therefore, good separation performance can be ensured.

  FIG. 4 shows another embodiment of the present invention. The same parts as those described above are denoted by the same reference numerals, and redundant description is omitted. In this mixed gas purification apparatus 1B, a temperature detector 8 that detects the gas temperature of the gas to be purified is provided in the supply flow path 11 downstream from the junction of the heat exchange flow path 10, and the gas that the temperature detector 8 detects. The pressure regulating valve 7 is adjusted according to the temperature. In addition, a return flow path 12 is provided for joining the off-gas separated by the separation device 6 to the gas to be purified, which is adiabatically compressed again by the gas compressor 2.

  According to this mixed gas purification device 1B, the temperature of the gas to be purified supplied to the separation device 6 is detected by the temperature detector 8 and the pressure regulating valve 7 is adjusted, so that the optimum temperature for the separation device 6 is always obtained. The gas to be purified can be supplied to the separation device 6 in a state of relative humidity. Thereby, the separation performance of the separation device 6 can be maintained satisfactorily. In addition, since the off-gas separated by the separation device 6 is returned and re-purified by the return flow path 12, the methane recovery rate of the purified gas can be further improved.

  FIG. 5 shows a specific embodiment of the present invention. The same parts as those described above are denoted by the same reference numerals, and redundant description is omitted. In the mixed gas purification apparatus 1 </ b> C according to this embodiment, a raw material mixed gas is introduced into an inlet channel 21 including an inlet valve 20, and the gas to be purified adiabatically compressed by the gas compressor 2 passes through the cooled channel 22. Into the condenser (gas-liquid separator) 5. The channel 22 to be cooled is provided with a heat exchanger (first heat exchanger) 3 and a cooler (second heat exchanger) 4, in which the first stage cooling (heat recovery) and the second stage cooling are performed. Cooling takes place.

  The gas to be purified that has passed through the condenser 5 is supplied to the separation device 6 via a supply passage 11 provided with a pressure regulating valve 7, a mixer 13, and a filter 9. In this example, a dust filter 9 </ b> A and a mist (oil) filter 9 </ b> B are connected as the filter 9. The separation device 6 is connected to an outlet channel 23 for taking out purified gas, and an outlet valve 25 is provided in the outlet channel 23. In this example, the separation device 6 includes a primary separation membrane and a secondary separation membrane, and carbon dioxide gas separated by the primary separation membrane is diffused into the atmosphere via the diffusion flow path 24 and separated by the secondary separation membrane. The off gas joins the inlet channel 21 via the return channel 12.

  As described above, the heat exchanger (first heat exchanger) 3 performs heat exchange through the heat exchange flow path 10 whose flow rate is controlled by the degree of opening and closing of the pressure regulating valve 7. The temperature of the gas to be purified supplied to the separation device 6 is adjusted with the heat recovered in step (b). The cooler (second heat exchanger) 4 performs heat exchange via a refrigerant flow path 41 that sends the refrigerant from the cooling tower 40, for example.

  The mixed gas purification apparatus 1C includes a control unit 14 that controls the operating state thereof. First, the control unit 14 controls the opening and closing of the pressure regulating valve 7 based on the detection value of the temperature detector 8 provided in the supply flow path 11, so that the temperature of the gas to be purified supplied to the separation device 6 as described above. And keep the relative humidity in a proper state.

  Further, the control unit 14 controls the inlet valve 20 based on the measured values of the flow meters F1, F2, F3, and F4 provided in the inlet channel 21, the return channel 12, the diffusion channel 24, and the outlet channel 23, respectively. By controlling the opening degree and the output of the pump 42 provided in the refrigerant flow path 41, the cooling performance is controlled according to the operating load situation. Further, the control unit 14 adjusts the pressure provided in the pressure adjusting flow path 31 serving as a bypass flow path for the gas compressor 2 according to the measurement value of the pressure gauge P1 that detects the output side pressure of the gas compressor 2. The compression state of the gas compressor 2 is appropriately controlled by controlling the opening and closing of the valve 30.

  As described above, the mixed gas purification apparatuses 1, 1A, 1B, and 1C according to the embodiments or examples of the present invention effectively use the heat generated by gas compression, so that the mixed gas purification has high energy use efficiency. An apparatus can be realized. Moreover, it is possible to ensure good separation performance by using the separation device 6 in an appropriate temperature range while lowering the relative humidity of the mixed gas supplied to the separation device 6.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and the design can be changed without departing from the scope of the present invention. Is included in the present invention. In addition, the above-described embodiments can be combined by utilizing each other's technology as long as there is no particular contradiction or problem in the purpose and configuration.

1, 1A, 1B, 1C: mixed gas purifier, 2: gas compressor,
3: Heat exchanger (first heat exchanger),
4: Cooler (second heat exchanger), 40: Cooling tower,
41: refrigerant flow path, 42: pump,
5: capacitor, 6: separation device, 7: pressure regulating valve, 8: temperature detector,
9: filter, 9A: dust filter, 9B: mist (oil) filter,
10: heat exchange channel, 11: supply channel, 12: return channel, 13: mixer,
14: Control unit, 20: Inlet valve, 21: Inlet channel, 22: Cooled channel,
23: outlet channel, 24: diffusion channel, 25: outlet valve, 30: pressure regulating valve,
31: Pressure adjusting flow path, F1, F2, F3, F4: Flow meter, P1: Pressure gauge

Claims (5)

A gas compressor that adiabatically compresses a mixed gas containing carbon dioxide gas to be purified;
A heat exchanger that recovers heat of the mixed gas adiabatically compressed by the gas compressor;
A cooler for cooling the mixed gas recovered by heat in the heat exchanger;
A condenser for removing drainage of the mixed gas cooled by the cooler;
A separation device for separating the mixed gas via the condenser into purified gas,
The mixed gas purification apparatus, wherein the mixed gas passing through the condenser is heated by the heat recovered by the heat exchanger and supplied to the separation apparatus. A supply flow path for supplying mixed gas via the condenser to the separation device;
The supply channel is provided with a pressure regulating valve,
A heat exchange flow path is provided that branches upstream of the pressure regulation valve of the supply flow path and joins downstream of the pressure regulation valve of the supply flow path via the heat exchanger. The mixed gas purification apparatus according to claim 1.   A temperature detector for detecting the gas temperature of the mixed gas is provided in the supply flow channel downstream from the joining point of the heat exchange flow channel, and the pressure regulating valve is adjusted according to the gas temperature detected by the temperature detector. The mixed gas purifier according to claim 2.   The mixed gas purifier according to claim 2 or 3, wherein the supply flow path includes a filter for removing impurities in the mixed gas.   The said separation apparatus is provided with the separation membrane which selectively permeate | transmits a carbon dioxide gas from mixed gas, The mixed gas refinement | purification apparatus described in any one of Claims 1-4 characterized by the above-mentioned.

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