AU2010357341A1

AU2010357341A1 - Associated-water concentration system and associated-water concentration method

Info

Publication number: AU2010357341A1
Application number: AU2010357341A
Authority: AU
Inventors: Koji Harada; Shigeo Hatamiya; Mutsumi Horitsugi; Koji Kageyama; Shunichi Kuba
Original assignee: Hitachi Ltd; Sasakura Engineering Co Ltd
Current assignee: Hitachi Ltd; Sasakura Engineering Co Ltd
Priority date: 2010-07-12
Filing date: 2010-07-12
Publication date: 2013-05-16
Anticipated expiration: 2030-07-12
Also published as: JP5495404B2; JPWO2012008014A1; WO2012008014A1; AU2010357341B2

Abstract

Disclosed is an associated-water concentration system provided with an evaporative concentration device (18) that concentrates associated water discharged from a coal bed along with coal-bed gas. A cooling system that cools said evaporative concentration device (18) comprises: an indirect heat exchanger (28) that cools the evaporative concentration device (18); and a closed loop. Said closed loop comprises either: a cooling-water supply means (38) that draws cooling water (36), used in cooling, from a well (68) or storage pond (34) and supplies said cooling water to the indirect heat exchanger (28); or a waste-hot-water return means (40) that returns post-cooling waste hot water (44) to the well (68) or storage pond (34). This configuration obviates the need for special equipment for treating cooling water (36) after use in the evaporative concentration device (18).

Description

DESCRIPTION Title of the Invention ASSOCIATED WATER CONCENTRATION SYSTEM AND ASSOCIATED WATER CONCENTRATION METHOD Technical Field [0001] The present invention relates to an associated water concentration system and an associated water concentration method. The invention particularly relates to an associated water concentration system and an associated water concentration method having a feature in a cooling water circulation system which is required when associated water formed upon coal mining is treated by an evaporation method. Background Art [0002] In recent years, a coal bed methane gas present in coal. beds has attracted attention as a new natural gas. Since the coal bed methane gas is dissolved in an associated water contained in coal beds, it is obtained by pumping up the associated water by a screw pump provided in a well. and then separating a methane gas from the associated water (refer to Non-Patent Literature 1). [0003] Since the associated water after separation from the methane gas contains salts, it cannot be used for irrigation or 1 revegetation or cannot be released to rivers as it is in a not treated state. Such associated water was treated by temporarily storing the same in a separately provided pond and reducing the volume by spontaneous evaporation, or by concentration in a reverse osmosis membrane device and then reducing the volume by spontaneous evaporation, followed by storing in a storage pond. [0004] However, the method of temporarily storing the associated water in the storage pond results in a problem of requiring an extensive storage pond when mining of the coal bed methane is continued, making it difficult to continue the mining operation of the coal bed methane gas. Further, also in a case of volume reduction by the concentration treatment using the reverse osmosis membrane device, since the power necessary for reverse osmosis device increases along with increase in the salt concentration, it is difficult to obtain a high concentration ratio in terms of the processing cost, which results in the same problem. [0005] On the other hand, in sea water desalting, a desalting device has been known that supplies a concentrated water after a reverse osmosis membrane treatment to an evaporative concentration device using a multiple effect evaporation process or multi-stage flashing process, thereby decreasing the entire amount of concentrated water (for example, refer to Patent Literature 1) . Further, there is an evaporative concentration device capable of efficiently performing 2 evaporative concentration of an aqueous solution (for example, refer to Patent Literature 2) . Since the necessary power or energy for the evaporative concentration device less suffers from the effect of the salt concentration, a high concentration ratio can be obtained by using the desalting apparatus described above. Prior Art Literature Patent Literature [0006] Patent Literature 1: JP-2008-100219-A Patent Literature 2: JP-2010-46571-A Non-Patent Literature 1: "Petroleum - Natural Gas Review", by Shigeki Sakamoto, Yasunobu Ohno, Independent Administration Corporation, Petroleum and Natural Gas - Metal Mineral Resource Mechanism, November 2008, Vol. 42, No. 6, pp. 31 to 49 Summary of the Invention Problem to be Solved by the Invention [0007] By using the techniques of the Patent Literatures 1 and 2 described above, the volume of the associated water afLer separation of the methane gas can be decreased. However, to operate the condensation device of an evaporative condensation device, it is necessary, for example, that the cooling water be taken from rivers, seas, etc. and supplied, and a waste warm water be returned after heat exchange to rivers, seas, etc. When the cooling water used for 3 the evaporative concentration device is returned after use to rivers or seas, since the temperature of water is higher than that of water when it is supplied or chemicals are added as ingredients, undesired effects may possibly be provided on ecological systems or environments of rivers or seas. [0008] To suppress such undesired effects, when sea water or river water after utilized as the cooling water is returned to the seas or rivers, environmental regulation to the difference of water temperature or incorporated substances are in force in many districts. In order to comply with the environmental regulations, it is necessary to provide equipment of cooling water or equipment of removing chemicals after use, which results in a problem of increasing the installation cost or running cost. [0009] The present invention has been accomplished in view of the foregoings and it intends to provide an associated water concentration system and an associated water concentration method requiring no special equipment for treating cooling water after use in the evaporative concentration device in an associated water concentration system using an evaporative concentration device capable of reducing the volume of the associated water formed upon obtaining a coal bed methane gas and decreasing the amount of concentrated water stored in a storage pond. Means for Solving the Problem 4 [0010] To attain the purpose described above, a first invention provides an associated water concentration system provided with an evaporative concentration device for concentrating n associated water discharged together with a coal bed gas from a coal bed in which a cooling system for cooling the evaporative concentration device includes an indirect heat exchanger for cooling the evaporative concentration device, and a closed circuit comprising one of a closed circuit having cooling water supply means for taking cooling water used for cooling from a well or a storage pond and supplying the same to the indirect heat exchanger, and the indirect heat exchanger, and another closed circuit having waste warm water return means for returning waste warm water after cooling to the well or the storage pond, and the indirect heat exchanger. [0011] To attain the purpose described above, a second invention provides an associated water concentration system provided with an evaporative concentration device for concentrating associated water discharged together with a coal bed gas from a coal bed in which a cooling system for cooling the evaporative concentration device includes a closed circuit comprising an indirect heat exchanger for cooling the evaporative concentration device, cooling water supply means taking a cooling water used for cooling from a well or a storage pond and supplying the same to the indirect heat exchanger and waste warm water return means for returning waste warm water after cooling to the well or the storage pond. 5 [0012] A third invention according to the first or second invention includes electric power generation equipment capable of utilizing a waste heat as a heat source for the evaporative concentration device, and a waste heat recovery boiler. [00131 Further, a fourth invention according to any one of the first to third invention includes a reverse osmosis membrane concentration device in a stage before the evaporative concentration device, and concentrated water from the reverse osmosis membrane concentration device is supplied as a raw water for the evaporative concentration device. [0014] Further, a fifth invention according to any one of the first to fourth inventions includes water temperature measuring means for measuring the water temperature of a waste warm water discharged after cooling in the indirect heat exchanger, and a control device for controlling the flow rate of the cooling water supply means and/or the flow rate of the waste warm water return means such that the temperature of the waste warm water measured by the water temperature measuring means is at a previously set predetermined value or lower. [0015] Further, a sixth invention according to the fifth invention uses inverters for outputting powers to the cooling water supply means and/or waste warm water return means in accordance with the output of the control device to control the flow rate of the cooling water supply means and/or the flow 6 rate of the waste warm water return means. [0016] Further, a seventh invention according to any of the first to sixth inventions provides cooling means for cooling the cooling water in the stage in a stage before the cooling water is supplied to the evaporative concentration device. [0017] Further, in an eighth invention according to any one of first to seventh inventions, the storage pond has a predetermined range of depth set and a water intake port for the cooling water below the range of the water depth. [0018] Further, a ninth invention according to any one of first to eighth inventions uses an electric immersion pump as a device for taking the cooling water from the well. [0019] Further, a tenth invention according to the ninth invention includes a submersible fine particle detector for detecting the amount of fine solid particles in the associated water, and an electric immersion pump control device for stopping the operation or decreasing the intake flow rate of the electric immersion pump based on a fine solid particle signal corresponding to an output of the submersible fine particle detector. [0020] Further, an eleventh invention according to the ninth invention includes a submersible bubble detector for detecting the amount of bubbles in the associated water, and an electric 7 immersion pump control device for stopping the operation or decreasing the intake flow rate of the electric immersion pump based on a bubble signal corresponding to an output of the submersible bubble detector. [0021] Further, a twelfth invention provides an associated water concentration method using an evaporative concentration device for concentrating associated water discharged together with a coal bed gas from a coal bed in which a cooling step for cooling the evaporative concentration device includes a cooling water supplying step of taking a cooling water for cooling from a well or a storage pond and supplying the same to an indirect heat exchanger for cooling the evaporative concentration device, and a waste warm water return step of returning waste warm water after cooling to the well or the storage pond. Effects of the Invention [0022] According to the present invention, since the volume of the associated water can be reduced by the evaporation method, discarding of the associated water is facilitated. Further, cooling or treatment with chemicals is not necessary when the cooling water for the evaporative concentration device taken from the well or the storage pond is returned to the water intake site, installation cost and running cost can be decreased compared with a case in which the cooling water is returned to river or sea water. 8 Brief Description of the Drawings (0023] Fig. 1 is a configurational view of a system showing a first embodiment of an associated water concentration system according to the present invention. Fig. 2 is a schematic cross sectional view showing a water intake portion of a storage pond in the first embodiment of the associated water concentration system of the present invention. Fig. 3 is a configurational view of a system showing a second embodiment of an associated water concentration system according to the present invention. Fig. 4 is a configurational view of a system showing a third embodiment of an associated water concentration system according to -he present invention. Fig. 5 is a configurational view of a system showing a fourth embodiment of an associated water concentration system according to rhe present invention. Fig. 6 is a configurational view of a system showing a fifth embodiment of an associated water concentration system according to the present invention. Mode for Carrying out the Invention [0024] < First Embodiment > The first embodiment of an associated water concentration system of the present invention will be described with reference to the drawings. Fig. 1 is a configurational view 9 for a system showing the first embodiment of the associated water concentration system of the invention. Fig. 2 is a schematic cross sectional view showing a water intake portion of a storage oond in the first embodiment of the associated water concentration system of the invention. [0025] In Fig. 1, associated water, which is no longer necessary after it is taken from a coal bed and coal bed gas is separated therefrom, forms raw water 10 for the associated water concentration system. The raw water 10 flows into a reverse osmosis membrane concentration device 12 and separated into fresh water 14 and concentrated water 16. While the use of the fresh water 14 is not defined, since the salt concentration therein is low, the fresh water can be released to rivers or used as irrigation water. [0026] The concentrated water 16 from the reverse-osmosis membrane concentration apparatus 12 is supplied to an evaporative concentration device 18. To the evaporative concentration device 18, steam 24 is supplied from a waste heat recovery boiler 26 that converts an exhaust gas 22 from electric power generation equipment into steam 24. By utilizing the heat energy of the steam 24, the concentrated water 16 in the reverse-osmosis membrane device 12 is separated into fresh water 30 and highly concentrated water 32 by an indirect heat exchanger 28 provided in the evaporative concentration device 18 for cooling the evaporative concentration device 18 without changing the water quality of 10 cooling water 36 so as not to give undesired effects on the underground water layer. [0027] Since highly concentrated water 32 of high salt concentration cannot be released as it is to rivers or cannot be used as irrigation water, it is discarded into a storage pond 34 or supplied to a not illustrated crystallization device for the recovery of variables. In this embodiment, since the amount of the highly concentrated water 32 discharged from the associated water concentration system is small, the capacity of the storage pond 34 can be reduced or the size of the not illustrated crystallization device can be decreased. [0028] The cooling water 36 required for the indirect heat exchanger 28 is taken from the storage pond 34 by cooling water supply means 38. The cooling water supply means 38 may comprise specifically, for example, an electric pump. [0029] Since water in the storage pond 34 is always evaporated from its water surface, heat of evaporation lowers the water temperature of the storage pond 34. However, no sufficient cooling cannot sometimes be attained by the effect of the solar radiation or atmospheric temperature. Therefore, cooling means 42 for lowering the temperature of the cooling water 36 is provided downstream the cooling water supply means 38 and the cooling water lowered for the water temperature is supplied to the indirect heat exchanger 28. The cooling means 42 includes, for example, a method of using a heat pump, an electronic 11 cooling method by a Peltier device, a method of evaporating a portion of the cooling water 36 by a spray device or the like and further cooling the remaining cooling water 36 by the evaporation heat, a method of using an absorption type refrigerator, and a method of using cold heat stored previously in ice by utilizing surplus power, and any of the methods may be used. When the water temperature of the cooling water 36 can be lowered by the storage pond 34, etc., the cooling means 42 may not be installed. [0030] The cooling water 36 receives the heat energy in the indirect heat exchanger 28 and is formed into waste warm water 44. The waste warm water 44 is circulated by waste warm water return means 40 to the storage pond 34 to constitute a closed circuit. Unlike rivers or seas, since the storage pond 34 has no restriction on the difference between the water intake temperature and the discarding temperature, provision of cooling equipment is not particularly necessary. [0031] When taking the cooling water 36 from the storage pond, the water temperature fluctuates with time due to the effect of the amount of solar radiation or atmospheric temperature. Also when the cooling water 36 is taken from a well, fluctuation of the water temperature with time occurs while the time constant is larger than that of the storage pond. While the concentration performance of the indirect heat exchanger 28 undergoes the effect of the temperature of the cooling water 36, it can be evaluated by the temperature of the waste warm water 12 44. The tempErature of the waste warm water 44 is measured by a water temperature sensor 46 and sent to a control device 50 as a water temperature signal 48. The control device 50 controls the flow rate of the cooling water supply means 38 or the flow rate of the waste warm water return means 40 and controls the cooling performance of the cooling means 42 based on a predetermined waste warm water temperature aimed value 52 and the water temperature signal 48. In this case, the control device 50 calculates the operation conditions to minimize the total of the operation cost for the cooling water supply means 38 or the waste warm water return means 40 and the operation cost for the cooling means 42 and then performs control on the cooling water supply means 38, the waster warm water return means 40, and the cooling means 42 so as to realize the conditions. [0032] The flow rate control described above is performed by outputting operation signals 60, 64 to an inverter 54 for the cooling water supply means and an inverter 56 for the waste warm water return means respectively from the control device 50, thereby controlling the cooling water supply means power 62 and the waste warm water return means power 66 as the power for the pump electric motor of the cooling water supply means 38 and the waste warm water return means 40. This can decrease the loss of pressure that would otherwise be consumed wastefully as compared with a case in which a valve for the flow rate control is used, resulting in further decrease in running cost. [0033] 13 When the cooling means 42 is not provided, the target to be controlled by the control device 50 is only the cooling water supply means 38 or the waste warm water return means 40. Also in this case, the running cost can be decreased by controlling thle flow rates of the respective means by way of the inverter 54 for the cooling water supply means or the inverter 56 for the waste warm water return means based on the waste warm war:er temperature signal 48 and a waster warm water aimed value 52. [0034] Fig. 2 is a schematic view showing a water intake portion of a storage pond in the first embodiment of the associated water concentration system of the invention. In Fig. 2, since those carrying same references as in Fig. 1 show identical portions, detailed description therefor is to be omitted. [0035] When the cooling water 36 is taken from the storage pond 34, the temperature of water near the water level of the storage pond 34 is high under the effect of solar radiation or atmospheric temperature. On the other hand, since heat is deprived as evaporation heat upon evaporation of water from the surface of the storage pond 34, a physical phenomenon of lowering the water temperature occurs simultaneously. Further, when the atmospheric temperature at the periphery of the storage pond is lower than the water temperature, since heat escapes from the water surface into the atmosphere, the water temperature is lowered. The density of water is changed depending on the water temperature and at the maximum at about 14 4*C. Since there is no stirring device in the storage pond 34, water at low temperature generally moves toward the bottom of the storage pond 34. [0036] In this embodiment, difference of the water temperature depending on the depth of the storage pond is taken into consideration and a water intake port 70 for the cooling water 36 is disposed at a deeper position than a predetermined depth and the cooling water 36 is taken therefrom. Thus, cooling water 36 of lower water temperature can be obtained. [0037] According to the first embodiment of the associated water concentration system of the invention described above, since the volume of the associated water can be reduced by the evaporation method, the associated water is discarded easily. Further, since cooling or treatment with chemicals is not necessary when the cooling water of the evaporative concentration device taken from the storage pond is returned to the site from which water was taken, the installation cost and the running cost can be decreased as compared with a case in which the cooling water is returned to river or sea water. [00381 Further, according to the first embodiment of the associated water concentration system of the invention described above, cost for laying pipelines or operation cost can be decreased by taking the cooling water 36 from the storage pond 34 in a well 68 to collect a coal bed gas therein, which is generally situated at a place remote from rivers or 15 seas. [0039] Further, according to the first embodiment of the associated water concentration system of the invention described above, since the water intake port 70 of the storage pond is provided at a deeper position than the predetermined depth D, a cooling water 36 at a low water temperature can be obtained and the amount of the cooling water necessary for obtaining cold heat required in the indirect heat exchanger 28 can be decreased. As a result, the cooling water supply means 38 or the wa:3te warm water return means 40 can be decreased in capacity and power cost. [0040] < Second Embodiment > A second embodiment of the associated water concentration system of the invention will be described with reference to the drawings. Fig. 3 is a configurational view for a system showing the second embodiment of the associated water concentration system of the invention. In Fig. 3, since those carrying the same references as in Fig. 1 and Fig. 2 show identical portions, detailed description therefor is to be omitted. [0041] In Fig. 3, the cooling water supply means 38 in the first embodiment is omitted. When there is no free surface in the midway of a pipeline for cooling water 36, water can be taken by the waste warm water return means 40 and the cooling water supply means 38 can be saved. When the cooling water 36 is 16 taken by the waste warm water return means 40 from the storage pond 34, since the water temperature in the waste warm water return means 40 is elevated, the viscous resistance of water i s lowered and the running cost can be decreased. The waster warm water return means 40 may specifically comprise, for example, an electric pump. [0042] < Third Embodiment > A third embodiment of the associated water concentration system of the invention will be described with reference to the drawings. Fig. 4 is a configurational view of a system showing the third embodiment of the associated water concentration system of the invention. In Fig. 4, since those carrying the same reference numerals as in Fig. 1 to Fig. 3 show identical portions, detailed description therefor is to be omitted. [0043] In Fig. 4, the waste warm water return means 40 in the first embodiment is omitted. When there is no free water surface in the midway of the pipeline of the cooling water 36, water can be taken/returned only by the cooling water supply means 38 and the waste warm water return means 40 can be saved. [0044] < Fourth Embodiment > A fourth embodiment of the associated water concentration system of the invention will be described with reference to the drawings. Fig. 5 is a configurational view of a system showing the fourth embodiment of the associated water concentration system of the invention. In Fig. 5, since those carrying the 17 same references as in Fig. 1 to Fig. 4 show identical portions, detailed description therefor is to be omitted. [0045] In Fig. 5, associated water, which is no longer necessary after it is taken from a coal bed and coal bed gas is separated therefrom, forms raw water 10 for the associated water concentration system. The raw water 10 flows into a reverse osmosis membrane concentration device 12 and separated into fresh water 14 and concentrated water 16. While the use of the fresh water 14 is not defined, since the salt concentration therein is low, the fresh water can be released to rivers or used as irrigation water. [00461 The concentrated water 16 from the reverse osmosis membrane concentration device 12 is supplied to an evaporative concentration device 18. To the evaporative concentration device 18, steam 24 is given from a waste heat recovery boiler 26 that converts waste heat of an exhaust gas 22 from electric power generation equipment 20 into steam 24. By utilizing the heat energy of the steam 24, the concentrated water 16 from the reverse osmosis membrane concentration device 12 is separated into fresh water 30 and highly concentrated water 52 by an indirect heat exchanger 28 provided in the evaporative concentration device 18. [0047] Since a highly concentrated water 32 of high salt concentration cannot be released or used for irrigation, it is discarded to a storage pond 34 or supplied to a not illustrated 18 crystallization device for the recovery of variables. In this embodiment, since the amount of the high concentrated water 32 discharged from the associated water concentration system is small, the capacity of the storage pond 34 can be reduced or the size of the not illustrated crystallization device can be decreased. [0048] A cooling water 36 required for the indirect heat exchanger 28 is taken from a well 68 by cooling water supply means 38 or waste warm water return means 40. Since a well to collect a coal bed gas therein is generally located at a place remote from rivers or seas, the cost for laying a pipeline or the operation cost can be decreased by taking the cooling water 36 from the well 68. [0049] Since the water temperature of well water taken from the well 68 is generally stable and suffers from no undesired effect of atmospheric temperature or solar radiation, this is suitable as the cooling water 36. However, when sufficient cooling cannot be attained, cooling means 42 is provided downstream the cooling water supply means 38 and the cooling water 36 lowered for the water temperature is supplied to the indirect heat exchanger 28. The cooling means 42 includes, for example, a method of using a heat pump, an electronic cooling method by a Peltier device, a method of evaporating a portion of the cooling water 36 by a spray device or the like and further cooling the remaining cooling water 36 by the evaporation heat, a method of using an absorption type 19 refrigerator, and a method of using cold heat stored previously in ice by utilizing surplus power, and any of the methods may be used. When the water temperature of the cooling water 36 can be lowered by the storage pond 34, etc., the cooling means 42 may not be installed. [0050] The cooling water 36 receives the heat energy in the indirect heat exchanger 28 and is formed into waste warm water 44. The waste warm water 44 is circulated by waste warm water return means 40 to the well 68 to constitute a closed circuit. Unlike rivers or seas, since the well 68 has no restriction on the difference between the water intake temperature and the discarding temperature, provision of cooling equipment is not particularly necessary. Further, since the cooling water 36 undergoes only the temperature change but no change for the chemical nature by the indirect heat exchanger 28, circulating the waste warm water 44 to the well 68 arises no problem. [0051] Fig. 5 illustrates a flow of returning the waste warm water 44 to the well 68 after water is taken from the well 68 and used for cooling, and the waste warm water 44 may be returned to the storage pond 34. [0052] While the concentration performance of the indirect heat exchanger 28 undergoes the effect of the temperature of the cooling water 36, the performance can be evaluated by the water temperature cf the waste warm water 44. The temperature of the waste warm water 44 is measured by a water temperature sensor 20 46 and given as a water temperature signal 48 to a control device 50. The control device 50 controls the flow rate of the cooling water supply means 38 and the flow rate of the waste warm water return means 40 and controls the cooling performance of the cooling means 42 based on the predetermined aimed value 52 for the waste warm water temperature and the water temperature signal 48. In this case, the control device 50 calculates the operation conditions to minimize the total of the operation cost for the cooling water supply means 38 or the waste warm water return means 40 and the operation cost for the cooling means 42 and then controls the cooling water supply means 38, the waste warm water return means 40, and the cooling means 42 so as to realize the conditions. [0053] The flow rate control described above is performed by outputting operation signals 60, 64 to an inverter 54 for the cooling water supply means and an inverter 56 for the waste warm water return means respectively from the control device 50, thereby controlling the cooling water supply means power 62 and the waste warm water return means power 66 as the power for the pump electric motor of the cooling water supply means 38 and the waste warn water return means 40. [0054] When the cooling means 42 is not provided, the target to be controlled by the control device 50 is only the cooling water supply means 38 or the waste warm water return means 40. Also in this case, the running cost can be decreased by controlling tIe flow rate of the respective means by way of the 21 inverter 54 for the cooling water supply means or the inverter 56 for the waste warm water return means based on the waste warm water temperature signal 48 and a waste warm water aimed value 52. [0055] According to the fourth embodiment of the associated water concentration system of the invention described above, since the volume of the associated water can be reduced by the evaporation method, the associated water is discarded easily. Further, since cooling or treatment with chemicals is not necessary when the cooling water of the evaporative concentration: device taken from the storage pond is returned to the site at which water was taken, the installation cost and the running cost can be decreased as compared with a case in which the cooling water is returned to river or sea water. [00561 Further, according to the fourth embodiment of the associated water concentration system of the invention described above, cost for laying pipelines or operation cost can be decreased by taking the cooling water 36 from the well 68 to collect a coal bed gas therein, which generally is situated at a place remote from rivers or seas. [0057] < Fifth Embodiment > A fifth embodiment of the associated water concentration system of the invention will be described with reference to the drawings. Fig. 6 is a configurational view of a system showing the fifth embodiment of the associated water concentration 22 system of the invention. In Fig. 6, since those carrying the same references as in Fig. 1 to Fig. 5 show identical portions, detailed description therefor is to be omitted. [0058] In Fig. 6, an electric immersion pump 72 is used as the cooling water supply means 38 for taking the cooling water 36 from the well 68 of a coal bed in the fourth embodiment described above. When the electric immersion pump 72 is used for pumping up the associated water contained in the coal bed, the ratio of mechanical loss is decreased as compared with a screw pump used so far and the maintenance is also easy. As a result, the running cost can be decreased. [0059] On the other hand, if solid matters that may clog the electric immersion pump 72 are contained in the pumped up associated water, the performance of the electric immersion pump 72 may be lowered, or the pump may fail in the worst case. Should the pump fail, since the electric immersion pump 72 is provided in the lower portion of the well 68, pulling up or maintenance of the pump in question will require considerable time and cost. [0060] Solid matters contained in associated water could conceivably include powdery coals, rock powders or sand grains. If such solid matters are in a finely particulate form, they tend to intrude between pump components, leading to failure. [0061] In view of this, the fifth embodiment includes a 23 submersible fine particle detector 74 for detecting the amount of solid fine particles in the associated water and an electric immersion pump control device 82 for stopping the operation or decreasing the suction flow rate of the electric immersion pump 72 based on a detection signal of the submersible fine particle detector 74. When the amount of the solid fine particles increases in the associated water, the suction flow rate is decreased or the operation is stopped for the electric immersion pump 72 until the solid fine particles are settled down and then the pumping operation is started, by which lowering of the performance, etc. of the electric immersion pump 72 can be suppressed. [0062] Further, when a great amount of a gas, for example, methane is contained in the form of bubbles in the pumped up associated water, the electric immersion pump 72 operates idly to lower the performance and, in the worst case, result in failure. Should the pump fail, since the electric immersion pump 72 is provided in the lower portion of the well 68, pulling up or maintenance of the pump will require considerable time and cost. [0063] Then, this embodiment includes a submersible bubble detector 78 for detecting the amount of bubbles in the associated water and an electric immersion pump control device 82 for stopping the operation or decreasing the suction flow rate of the electric immersion pump 72 based on the detection signal of the submersible bubble detector 78. 24 [0064) According to the fifth embodiment of the associated water concentration system of the invention described above, the same effect as the fourth embodiment described above can be obtained and, in addition, since the electric immersion pump 72 is used instead of the screw pump, the ratio of the mechanical. loss is decreased and the maintenance is easy. As a result, the running cost can be decreased. [0065] Further, according to the fifth embodiment of the associated water concentration system of the invention described above, since the submersible fine particle detector 74, the submersible bubble detector 78, and the electric immersion pump control device are provided, deterioration of the performance or the failure of the electric immersion pump 72 caused by solid fine particles or bubbles in the associated water can be prevented in an early stage. As a result, time and cost that would otherwise be consumed for the pulling up operation or the maintenance of the electric immersion pump 72 can be decreased. [0066) In the embodiment of the invention, while description has been made to the evaporative concentration device 18 to which the concentrated water 16 concentrated by the reverse osmosis membrane concentration device 12 is supplied, the invention is not restricted thereto. For example, an evaporative concentration device 18 to which the associated water is supplied directly as the raw water 10 may be used for example. 25 Description of Reference Numerals [0067] 10 raw water 12 reverse osmosis membrane concentration device 14 fresh water 16 concentrated water 18 evaporative concentration device 20 electric power generation equipment 22 exhaust gas 24 steam 26 waste heat recovery boiler 28 indirect heat exchanger 30 fresh water 32 highly concentrated water 34 storage pond 36 cooling water 38 cooling water supply means 40 waste warm water return means 42 cooling means 44 waste warm water 46 water temperature sensor 48 water temperature signal 50 control device 52 aimed value of waste warm water temperature 54 inverter for cooling water supply means 56 inverter for waste warm water return means 58 cooling means operation signal 60 cooling water supply means operation signal. 26 62 cooling water supply means power 64 waste warm water return means operation signal 66 waste warm water return means power 68 well 70 water intake port 72 electric immersion pump 74 submersible fine particle detector 76 fine particle signal 78 submersible bubble detector 80 bubble signal 82 control device for electric immersion pump 84 electric immersion pump power 27

Claims

1. An associated water concentration system provided with an evaporative concentration device (18) for concentrating associated water discharged together with a coal bed gas from a coal bed, wherein a cooling system for cooling the evaporative concentration device (18) includes: an indirect heat exchanger (28) for cooling the evaporative concentration device (18), and a closed circuit comprising one of a closed circuit having cooling water supply means (38) for taking cooling water (36) used for cooling from a well (68) or a storage pond (34) and supplying the same to the indirect heat exchanger (28), and the indirect heat exchanger (28), and another closed circuit having a waste warm water return means (40) for returning a waste warm water (44) after cooling to the well (68) or the storage pond (34), and the indirect heat exchanger (28).

2. An associated water concentration system provided with an evaporative concentration device (18) for concentrating associated water discharged together with a coal bed gas from a coal bed, wherein a cooling system for cooling the evaporative concentration device (18) includes a closed circuit comprising an indirect heat exchanger (28) for cooling the - evaporative concentration device (18), 28 cooling water supply means (38) taking a cooling water (36) used for cooling from a well (68) or a storage pond (34) and supplying the same to the indirect heat exchanger (28), and waste warm water return means (40) for returning waste warm water (44) after cooling to the well (68) or the storage pond (34).

3. An associated water concentration system according to claim 1 or 2, including electric power generation equipment (20) capable of utilizing waste heat as a heat source of the evaporative concentration device (18), and a waste heat recovery boiler (26).

4. An associated water concentration system according to any one of claims 1 to 3, wherein a reverse osmosis membrane concentration device (12) is provided in a stage before the evaporative concentration device (18), and concentrated water (16) from the reverse osmosis membrane concentration device (12) is supplied as raw water (10) for the evaporative concentration device (18).

5. An associated water concentration system according to any one of claims 1 to 4, including water temperature measuring means (46) for measuring the temperature of waste warm water (44) discharged after cooling in the indirect heat exchanger (28), and a control device (50) for controlling the flow rate of the cooling water supply means (38) and/or the flow rate of the waste warm water return means (40) such that the temperature of the waste warm water (44) measured by the water temperature 29 measuring means (46) is at a predetermined value or less.

6. An associated water concentration system according to claim 5, wherein inverters (54), (56) for outputting powers to the cooling water supply means (38) and/or the waste warm water return means (40) in accordance with the output of the control device (50) to control the flow rate of the cooling water supply means (38) and/or the flow rate of the waste warm water return means (40) are used.

7. An associated water concentration system according to any one of claims 1 to 6, wherein cooling means (42) for cooling the cooling water (36) is provided in a stage before the cooling water is supplied to the evaporative concentration device (18).

8. An associated water concentration system according to any one of claims 1 to 7, wherein the storage pond (34) has a predetermined range of depth set and a water intake port (70) for the cooling water (36) is provided below the range of the depth.

9. An associated water concentration system according to any one of claims 1 to 8, wherein an electric immersion pump (72) is used as a device for taking the cooling water (36) from the well (88).

10. An associated water concentration system according to claim 9, including a submersible fine particle detector for detecting the amount of solid fine particles in the associated water, and an electric immersion pump control device for stopping the 30 operation or decreasing the suction flow rate of the electric immersion pump based on a solid fine particle signal corresponding to an output from the submersible fine particle detector.

11. An associated water concentration system according to claim 9, including a submersible bubble detector for detecting the amount of bubbles in the associated water, and an electric immersion pump control device for stopping the operation or decreasing the suction flow rate of the electric immersion pump based on a bubble signal corresponding to an output from the submersible bubble detector.

12. A method of concentrating associated water by an evaporative concentration device (18) for concentrating the associated water discharged together with a coal. bed gas from a coal bed, wherein a cooling step for cooling the evaporative concentration device (18) includes: a cooling water supplying step of taking cooling water (36) for cooling from a well (68) or a storage pond (34) and supplying the same to an indirect heat exchanger (28) for cooling the evaporative concentration device (18), and a waste warm water return step of returning a waste warm water (44) after cooling to the well (68) or the storage pond (34). 31