Drain elimination device, and gas concentration measurement system including the same

Abstract

To provide a drain elimination device that can prevent blockage by a drain and the like deriving from water vapor included in sample gas taken out from processed gas of a wet scrubber.SOLUTION: A drain elimination device has: a sample gas circulation pipe 21 that is formed into a U-shaped so as to fold up at the lowermost part 21a; a cooler that consists of a cooling box 24 performing cooling by causing sample gas to flow via two straight pipe sections 21b of the sample gas circulation pipe 21, and cool air generation means 25 supplying cool air inside of the cooling box 24; a drain recovery pipe 22 that branches from the lowermost part 21a of the sample gas circulation pipe 21; and a seal pot 23 that water-seals a lower end opening part 22a of the drain recovery pipe 22. Inside of the cooling box 24, a cool air distribution pipe 26 is provided that has a plurality of ejection ports ejecting the supplied cool air in a side surface, and an opening area of the ejection port per a unit length in an axial direction of the cool air distribution pipe 26 tapers toward a tip end part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a drain removal device and a gas concentration measurement system equipped with the drain removal device, and in particular to a drain removal device that removes moisture contained in sample gas extracted from treated gas discharged from a wet detoxification facility before the sample gas is introduced into a gas concentration measurement device, and a gas concentration measurement system composed of the drain removal device and the gas concentration measurement device. [Background technology]

[0002] In various factories such as non-ferrous metal smelting plants and petrochemical plants, products are manufactured by carrying out various chemical processes on raw materials and intermediate raw materials, and the equipment used for this chemical processing often emits high-temperature factory exhaust gases containing chemical substances that are subject to emission regulations (hereinafter also referred to as regulated substances), such as nitrogen oxides, sulfur oxides, and hydrogen chloride. Therefore, before being released into the atmosphere, this factory exhaust gas is introduced into wet abatement equipment such as a scrubber, where it is subjected to abatement treatment to remove the regulated substances to below a specified standard.

[0003] In the above-mentioned wet detoxification equipment, in order to constantly monitor whether the concentration of regulated substances contained in the gas discharged from the top of the tower after detoxification (hereinafter also referred to as treated gas) meets a predetermined standard, a sample gas is extracted from a duct connected to the top of the tower of the wet detoxification equipment and introduced into a gas concentration measuring device, where the concentration of the regulated substances in the sample gas is measured. If it is detected that the concentration of the regulated substances in the measured sample gas exceeds a voluntary control value set to, for example, one-tenth or less of the emission standard value, an alarm is issued in an instrument room or the like.

[0004] When high-temperature industrial exhaust gas is treated with a wet-type detoxification system as described above, the treated gas is saturated with water vapor and is accompanied by mist (droplets). Therefore, if a sample gas extracted from the treated gas that has been treated with the wet method is introduced directly into the gas concentration measuring device, the water vapor and mist can adversely affect the measurement results and cause clogging and corrosion inside the device. Therefore, a moisture removal device such as a cooler that condenses water vapor and a drain pot that removes mist is generally provided in front of the gas concentration measuring device.

[0005] For example, Patent Document 1 discloses a gas sampling device in which a three-way valve is provided on each of the upstream and downstream sides of a pretreatment section that pretreats sample gas to be supplied to a gas analyzer, and these three-way valves are connected to bypass the pretreatment section. Patent Document 2 discloses a gas analysis pretreatment device in which a filter for removing solids, a drain separator, and an electronic cooler are arranged in this order from upstream to downstream in a sample gas flow path of the pretreatment device for gas analysis, and in which a bubbling tank that stores a certain amount of dilute acid liquid downstream of the drain separator and bubbles the sample gas in the dilute acid liquid to dissolve and remove most of the corrosive gas in the sample gas and to solidify or dissolve and remove high-temperature vaporized substances, and a scrubber that separates and removes residual corrosive gas are provided. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-055246 A [Patent Document 2] JP 2006-010555 A Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, the treated gas discharged from the wet-type abatement equipment, which wet-type abatement treatment is performed on high-temperature factory exhaust gas containing regulated substances, is saturated with water vapor and is accompanied by the cleaning liquid used in the abatement treatment in the form of mist. Therefore, in order to measure the concentration of the regulated substances contained in the treated gas with a gas concentration measuring device, the temperature of the sample gas extracted from the treated gas flowing in the duct connected to the gas outlet of the wet-type abatement equipment using a sampling tube is immediately lowered by the outside air, etc., and the water vapor contained in the sample gas is condensed, and the condensed water generated by this becomes drain water and may clog the sampling tube.

[0008] As a countermeasure, as described above, a moisture removal device such as a drain pot or a cooler is generally provided in front of the gas concentration measurement device, and the sample gas is cooled in this cooler to actively condense the water vapor, and the condensed water thus generated can be separated and removed by gravity together with the mist in the drain pot. This allows the sample gas with a reduced moisture content to be introduced into the gas concentration measurement device, making it possible to measure the gas concentration stably with high accuracy. However, when the cooling capacity of the cooler of the moisture removal device is reduced for some reason, the condensation of the water vapor in the sample gas becomes insufficient, and the water vapor remaining in the sample gas may condense in the sampling tube before it leaves the cooler and is introduced into the gas concentration measurement device.

[0009] One way to prevent this problem of insufficient cooling is to increase the cooling capacity of the cooler. However, for example, if the cooling capacity of the cooler is increased by supplying more cooling air or cooling air at a lower temperature, the moisture content in the sample gas can be sufficiently reduced, but the amount of heat exchange between the cooling air and the sample gas will increase locally at the point where the cooling air is introduced into the cooler, and condensation water generated from the water vapor in the sample gas may freeze and block the flow path in the cooler or the sampling tube downstream.

[0010] As described above, even if the flow passage in the cooler and the sampling tubes at various locations, including the upstream side thereof, are blocked by drain water or ice made from frozen drain water (hereinafter collectively referred to as drain water, etc.), the pump in the gas concentration measuring device continues to operate, so the pressure in the flow passage downstream of the blocked location gradually decreases, and if a seal pot, etc. is provided downstream of the blocked location, the drain water stored in the seal pot, etc. may be sucked up and enter the gas concentration measuring device. In this case, the drain water may cause problems such as a decrease in the measurement accuracy of the gas concentration measuring device or a breakdown of the gas concentration measuring device, which is made up of expensive precision equipment. In particular, when the gas concentration measuring device breaks down, it is necessary to carry out an internal inspection to determine the cause of the breakdown, and to clean and replace the equipment and parts. During that time, it is not possible to know whether the wet decontamination equipment is performing decontamination properly, so it becomes necessary to stop operation of the wet decontamination equipment. However, this means that the production equipment that is the source of the factory exhaust gas that is being treated by the wet decontamination equipment will have to be temporarily shut down, which will have a serious adverse effect on the factory's operating rate.

[0011] In addition, if the sampling tube is clogged with drain water or the like as described above, the sample gas cannot be collected properly, and naturally the concentration of the sample gas cannot be measured correctly. In particular, in a gas concentration measuring device, in a structure in which the sample gas inlet pipe is branched into two, and the sample gas distributed to one of them is introduced into the measurement cell, and the sample gas distributed to the other is discharged from the gas concentration measuring device as a surplus through a discharge pipe, if the inlet pipe upstream of this branch point is clogged with drain water or the like, even if the problem of the drain water in the seal pot being sucked up and entering the gas concentration measuring device does not occur, a backflow occurs in the discharge pipe, and the sample gas is diluted with the outside air sucked in from the discharge pipe, or the outside air is introduced into the gas concentration measuring device, making it impossible to accurately measure the concentration of the sample gas.

[0012] The present invention has been made in consideration of the above circumstances, and has an object to provide a drain removal device and a gas concentration measurement system equipped with the drain removal device that can prevent problems such as blockages in the sampling tube, the drain removal device, and the gas concentration measurement device caused by drain water produced by condensation of water vapor contained in the sample gas and ice produced by freezing of the drain water, when the concentration of regulated substances contained in the sample gas extracted using a sampling tube from treated gas treated in a wet abatement equipment is measured with the gas concentration measurement device. [Means for solving the problem]

[0013] In order to achieve the above-mentioned object, the inventors have conducted extensive research into the configuration of a gas concentration measurement system, and as a result, have discovered that the above-mentioned object can be achieved by characterizing the cooling method and structure of a U-shaped tube that serves as a flow path for the sample gas in a drain removal device installed in the middle of a sampling tube that introduces sample gas extracted from treated gas treated in a wet detoxification equipment into a gas concentration measurement device, and have thus completed the present invention.

[0014] That is, the drain removal device of the present invention is a drain removal device that condenses water vapor contained in a sample gas extracted from treated gas of a wet-type detoxification equipment and removes it as drain water, and is characterized in that it has a sample gas circulation pipe formed in a U-shape so as to be folded back at the lowest part, a cooling box that performs cooling by passing the sample gas circulation pipe through two straight pipe sections excluding the lowest part, a cooler consisting of a cold air generating means that supplies cold air into the cooling box, a drain recovery pipe that branches off from the lowest part of the sample gas circulation pipe and extends downward, and a seal pot that seals the lower end opening of the drain recovery pipe with water, and a cold air dispersion pipe having a plurality of nozzles for spraying the cold air supplied from the cold air generating means and a closed tip is provided between the two straight pipe sections and parallel to these straight pipe sections within the cooling box, and the plurality of nozzles are opened on the side of the cold air dispersion pipe, and the opening area of ​​the nozzles per unit length in the axial direction of the cold air dispersion pipe gradually decreases toward the tip. Effect of the Invention

[0015] According to the present invention, when the concentration of regulated substances contained in a sample gas extracted using a sampling tube from treated gas in a wet detoxification system is measured using a gas concentration measuring device, it is possible to prevent problems such as blockages in the sampling tube, drain removal device, and gas concentration measuring device caused by drain water derived from water vapor contained in the sample gas and ice produced by freezing of the drain water. [Brief description of the drawings]

[0016] [Figure 1] 1 is a side view showing a gas concentration measurement system including a drain removal device according to an embodiment of the present invention together with a wet abatement facility. [Diagram 2] 2 is a front view showing a schematic internal structure of a gas concentration measurement device included in the gas concentration measurement system of FIG. 1. [Diagram 3] 1 is a perspective view of a drain removal device according to an embodiment of the present invention. [Figure 4] 1A to 1C are perspective views showing various specific examples of cold air dispersion pipes provided in a drain removal device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A gas concentration measurement system equipped with a drain removal device according to an embodiment of the present invention will be described below with reference to the drawings. The sample gas to be measured by the gas concentration measurement system according to the embodiment of the present invention is treated gas that has been treated by a wet detoxification facility. The wet detoxification facility is a device that removes (detoxifies) harmful chemical substances contained in factory exhaust gas discharged from production facilities of various factories so that the concentration of the harmful chemical substances contained in the factory exhaust gas is equal to or lower than the emission standard, and for example, a packed tower 1 as shown in FIG. 1 is preferably used.

[0018] 1, washing water such as a caustic soda solution is poured from the top of the tower against the industrial exhaust gas introduced from the bottom of the tower, and gas-liquid contact is performed by countercurrent flow in the packed bed 2, thereby removing regulated substances contained in the industrial exhaust gas by absorption into the washing water. The industrial exhaust gas that has been treated for harm in this way is discharged as treated gas from the top of the packed tower 1, passes through duct D, and is released into the atmosphere from a chimney (not shown).

[0019] A gas concentration measuring device 10 is provided near the duct D for measuring the concentration of regulated substances remaining in the sample gas extracted from the treated gas. The gas concentration measuring device 10 has an internal structure shown in Fig. 2, for example. That is, the gas concentration measuring device 10 shown in Fig. 2 is composed of a suction pump 11 consisting of a diaphragm pump or the like for sucking in the sample gas introduced from a sample gas inlet nozzle 10a, a flowmeter 12 for measuring the flow rate of the sample gas sucked by the suction pump 11, a gas trap 13 for removing drain water contained in the sample gas that has left the flowmeter 12 and for adjusting the flow rate of the sample gas to be supplied to a gas sampler 14 at the downstream, and the gas sampler 14 for measuring the concentration of regulated substances contained in the sample gas.

[0020] The surplus gas separated by the gas trap 13 is discharged from the surplus outlet nozzle 10b, while the sample gas measured by the gas sampler 14 is discharged from the exhaust gas outlet nozzle 10c. In this way, by introducing an excess amount of sample gas into the gas concentration measuring device 10 compared to the flow rate required for gas concentration measurement by the gas sampler 14, the concentration of the regulated substance in the sample gas can be stably measured. If the concentration of the regulated substance in the sample gas measured by this gas concentration measuring device 10 exceeds a predetermined control value, an alarm is issued, for example, by displaying "gas concentration abnormality" together with an alarm sound on a display in the instrument room.

[0021] As described above, in wet detoxification equipment, industrial exhaust gas is generally detoxified by directly contacting the industrial exhaust gas with cleaning water, so the treated gas discharged from the top of the wet detoxification equipment contains water vapor in a saturated state. Also, a liquid droplet removal means 3 such as a demister is generally provided at the top of the packed tower 1 from which the treated gas is discharged, but even in this case, the treated gas discharged from the top of the packed tower 1 is accompanied by mist that could not be collected by the liquid droplet removal means 3.

[0022] Furthermore, the temperatures of factory exhaust gas and cleaning water are usually higher than the outside air temperature, and therefore the temperature of the treated gas is also higher than the outside air temperature. Therefore, if a portion of the treated gas is extracted using the sampling tube 4 by the suction pump 11 of the gas concentration measuring device 10 and transferred directly to the gas concentration measuring device 10 as a sample gas, the water vapor contained in the sample gas will condense along the way, and the resulting condensed water will enter the gas concentration measuring device 10 together with the sample gas, which may reduce the measurement accuracy or cause the device to malfunction.

[0023] Therefore, the gas concentration measurement system of an embodiment of the present invention has a drain removal device 20 that actively condenses the water vapor contained in the sample gas by blowing cold air that is lower in temperature than the outside air temperature onto the sample gas extracted by the sampling tube 4 from outside the tube before the sample gas is introduced into the gas concentration measurement device 10, and removes the condensed water thus produced as drain water.

[0024] That is, as shown in Fig. 3, this drain removal device 20 has a sample gas flow pipe 21 formed in a U-shape so as to be folded back at the lowest part 21a, a cooling box 24 made of, for example, a circular pipe closed at both upper and lower ends with caps, which performs cooling by passing the sample gas through two parallel straight pipe parts 21b of the sample gas flow pipe 21 excluding the lowest part 21a, and a cooler consisting of a cold air generating means 25 for supplying cold air into the cooling box 24, a drain recovery pipe 22 branching off from the lowest part 21a of the sample gas flow pipe 21 and extending downward, and a seal pot 23 for sealing the lower end opening 22a of the drain recovery pipe 22 with water. Note that the "U-shape" defined in the present invention is not strictly limited to a U-shape, and includes any form in which the lower ends of two straight pipes extending in an approximately vertical direction are connected to each other. For example, the lowermost portion 21a of the sample gas flow pipe 21 shown in FIG. 3 has a "U-shape rotated 90° to the right" in which the lower ends of two straight pipes extending vertically are connected to each other by a connecting pipe extending horizontally, and this is also included in the "U-shape" defined in the present invention.

[0025] To explain each component in detail, a sample gas flow pipe 21 is connected to the middle of a sampling tube 4 that is installed along a predetermined path from a sampling point of a duct D that is connected to the top of a packed tower 1, which is a wet-type detoxification equipment, to a sample gas inlet 10a of a gas concentration measuring device 10. Of this sample gas flow pipe 21, two parallel straight pipe sections 21b pass through a cooling box 24 to which cold air is constantly supplied from a cold air generating means 25. As a result, the sample gas extracted from the treated gas of the packed tower 1 is cooled by the cold air while flowing inside these two straight pipe sections 21b, and water vapor contained in the sample gas is condensed.

[0026] The condensed water generated by the condensation is separated into gas and liquid from the sample gas by gravity, mainly running down the inner wall of the sample gas flow pipe 21, and can be removed. The removed condensed water is collected as drain water in the seal pot 23 via the drain recovery pipe 22 that branches off from the lowest part 21a of the sample gas flow pipe 21 and extends downward. The drain removal device 20 reduces the amount of water vapor in the sample gas to the amount of saturated water vapor at the temperature after cooling by the cold air, so that the gas concentration measurement device 10 can measure the concentration of the regulated substance in the sample gas with extremely high accuracy and stability. Therefore, malfunction is unlikely to occur, and an alarm can be correctly issued when the concentration of the regulated substance in the sample gas exceeds a predetermined upper limit (threshold value).

[0027] The seal pot 23 is provided with an overflow outlet 23a at the top of its side wall, and the collected drain water is discharged from the overflow outlet 23a to the outside of the system. This allows the liquid level of the stored water derived from the collected drain water to be maintained constant in the seal pot 23. The drain recovery pipe 22 is arranged so that its lower end opening 22a is located below the liquid level of the seal pot 23. This allows the lower end opening 22a of the drain recovery pipe 22 to be constantly water-sealed by the stored water in the seal pot 23, preventing the air, which is an external atmospheric gas, from entering the gas concentration measurement system.

[0028] By using the drain removal device 20, the amount of water vapor contained in the sample gas can be reduced, but when a vortex cooler in which compressed air rotates at high speed in a circular tube, compresses and expands to separate and generate cold air and hot air is used as the cold air generating means 25, it is possible to generate cold air having a temperature about 15 to 75°C lower than the temperature of the compressed air supplied, depending on the ratio of cold air and hot air exhausted from the vortex cooler and the temperature and pressure of the compressed air supplied to the vortex cooler. Therefore, if the flow of cold air supplied from the cold air generating means 25 is concentrated at one place or flows unevenly in the cooling box 24, condensed water generated from water vapor inside the sample gas flow pipe 21 may freeze and block the flow path of the sample gas.

[0029] Therefore, the drain removal device 20 has a cold air dispersion pipe 26 in the cooling box 24 so that the cold air generated by the vortex cooler can be dispersed almost uniformly in the cooling box 24. Specifically, the cold air dispersion pipe 26 is a cylindrical pipe, preferably made of urethane resin or fluororesin, with a plurality of nozzles and a closed tip, and is installed between two straight pipe parts 21b of the sample gas flow pipe 21 extending vertically in the cooling box 24 and parallel to these straight pipe parts 21b. Furthermore, the cold air dispersion pipe 26 has a plurality of nozzles on its side surface, and is arranged so that the opening area of ​​the nozzles per unit length in the axial direction gradually decreases toward the tip. As a result, the cold air can be applied almost evenly to the two straight pipe parts 21b in the cooling box 24 of the sample gas flow pipe 21, so that freezing due to excessive cooling of water vapor contained in the sample gas can be prevented. In addition, the opening area of ​​the nozzle per unit axial length is arranged to gradually decrease toward the tip, thereby making it possible to selectively cool the inlet and outlet of the sample gas flow pipe 21, which are the areas most in need of cooling the sample gas, while preventing freezing due to localized excessive cooling.

[0030] There is no particular limitation on the form of the jet openings of the cold air dispersion pipe 26 for gradually reducing the opening area of the jet openings per unit length. For example, as shown in Fig. 4(a), among a plurality of jet openings having the same pore diameter, the separation distance (pitch) between those adjacent in the vertical direction gradually increases toward the tip of the cold air dispersion pipe 26 (i.e., L1 < L2 < L3 < L4 < L5 < L6), or they may be arranged. Alternatively, as shown in Fig. 4(b), the pitch L in the vertical direction may be all the same, and instead, the pore diameter of the jet openings may gradually decrease toward the tip of the cold air dispersion pipe 26. As shown in Figs. 4(a) and (b), the plurality of jet openings are preferably arranged at the above-mentioned predetermined pitch in each of two rows along the axial direction at angular positions facing the two straight pipe portions 21b of the gas flow pipe 21 so that cold air can be directly blown toward the two straight pipe portions 21b.

[0031] Alternatively, as shown in Fig. 4(c), in addition to the two rows at the angular positions facing the two straight pipe portions 21b, a plurality of jet openings may be alternately provided in two rows at angular positions orthogonal to these angular positions by 90°. In this case, the cold air discharged from the jet openings at the angular positions orthogonal to the facing direction of the two straight pipe portions 21b hits the inner wall surface of the cylindrical cooling box 24 and then flows along the inner wall surface in the circumferential direction of the cooling box 24, and thus blows onto the surfaces of the two straight pipe portions 21b other than the side surfaces facing the cold air dispersion pipe 26. Therefore, it can be expected that the sample gas flowing inside the two straight pipe portions 21b is cooled more evenly and efficiently. By making the pore diameter of the insertion holes for the two straight pipe portions 21b through which the caps at the upper and lower ends constituting the cooling box 24 are inserted larger than the outer diameter of each straight pipe portion 21b, the cold air supplied into the cooling box 24 can be exhausted from the gap between the inside of this insertion hole and the outside of the straight pipe portion 21b. As a modification of Fig. 4(b), as shown in Fig. 4(d), in order to gradually reduce the opening area of the jet openings per unit length, the number of jet openings with the same pore diameter provided over the entire circumference in the circumferential direction of the cold air dispersion pipe 26 gradually decreases toward the tip while keeping the pitch L in the vertical direction all the same, for example, arranged to be 8, 7, 6,... from the top.

[0032] By using the gas concentration measurement system having the above configuration, it is possible to prevent blockages caused by drain water derived from condensation and mist of saturated water vapor contained in the sample gas, and ice generated by freezing of the drain water, in the drain removal device 20, the sampling tube 4 from the drain removal device 20 to the gas concentration measurement device 10, and in the gas concentration measurement device 10. However, due to various influences such as the operation state of the packed tower 1, such as the degree of clogging of the packed layer 2 in the packed tower 1 and the demister as the droplet removal means 3, the distance and path of the sampling tube 4 from the sampling point of the duct D connected to the top of the packed tower 1 to the drain removal device 20, the positional relationship between the sampling point and the drain removal device 20, and the outside air temperature, the inside of the sampling tube 4 from the sampling point of the duct D to the drain removal device 20 may become filled with the drain water, resulting in a smooth flow of the sample gas being hindered. Furthermore, due to the formation of crystals on the inner wall surface of the sampling tube 4 due to substances contained in the sample gas, and the adhesion of solid matter contained in the treated gas flowing through duct D to the inner wall surface of the sampling tube 4, the inside of the sampling tube 4 from the sampling point of duct D to the drain removal device 20 becomes filled with the above-mentioned drain water, which results in the smooth flow of the sample gas being hindered.

[0033] This problem of the smooth flow of the sample gas being hindered is particularly likely to occur when the treated gas flowing through duct D is hotter and more humid. The cooling of the sample gas is strengthened by the drain removal device equipped with the cooler described above, so that a larger amount of drain is generated in the sample gas flow pipe 21 when the treated gas flowing through duct D is hotter and more humid. The generated drain then falls by gravity through the drain recovery pipe 22 and is discharged into the seal pot 23, but the large amount of drain easily clogs the bottom part 21a of the U-shaped sample gas flow pipe 21.

[0034] If the above-mentioned obstruction or blockage of the smooth flow of the sample gas continues in the sampling tube 4 from the sampling point of the duct D to the drain removal device 20, the straight pipe section 21b of the sample gas flow pipe 21, and the lowest part 21a of the sample gas flow pipe 21, the pressure in the flow path of the gas concentration measurement system after the obstruction or blockage of the flow (hereinafter also referred to as the obstruction or blockage) will gradually decrease due to the suction of the sample gas by the suction pump 11 built into the gas concentration measurement device 10 described above, and if there is a seal pot 23 after the obstruction or blockage, the water stored for water sealing inside it will be sucked up and enter the gas concentration measurement device 10 through the sampling tube 4, which may reduce the measurement accuracy or cause the components of the device to break down. As described above, the gas concentration measurement device 10 is designed to issue an alarm when the measured concentration of the regulated substance exceeds a predetermined threshold value, but since it is generally not equipped with a function to detect a pressure drop due to obstruction or blockage of the flow in the sampling tube 4 and issue an alarm, it has been difficult to prevent problems caused by the obstruction or blockage of the flow.

[0035] 3, in the drain removal device 20 according to the embodiment of the present invention, it is preferable to provide a bypass pipe 27, which bypasses the branched portion of the drain recovery pipe 22, at the lowest portion 21a of the sample gas flow pipe 21 located outside the cooling box 24. As a result, even if the flow of the drain recovery pipe 22 and its branched portion is temporarily hindered or blocked by drain water, solid matter, ice, or the like, the sample gas can be made to flow through this bypass pipe 27, so that the measurement by the gas concentration measuring device 10 can be continued.

[0036] In the gas concentration measurement system according to the embodiment of the present invention, as shown in Fig. 3, it is preferable that the liquid level in the seal pot 23 is constantly monitored and that an abnormality signal is output when the liquid level reaches a predetermined level or lower. Furthermore, it is preferable that the suction pump 11 built into the gas concentration measurement device 10 is controlled to stop when the abnormality signal is output. This makes it possible to prevent the pressure in the flow path of the gas concentration measurement system from decreasing due to blockage caused by drain water or the like or the smooth flow of the sample gas in the sampling tube 4 being hindered upstream of the branching portion of the drain recovery pipe 22, causing the stored water in the seal pot 23 to be sucked up and the stored water from entering the gas concentration measurement device 10.

[0037] More specifically, when a specified amount of stored water, which is less than the amount of hold-up from the branched portion of the drain recovery pipe 22 to the sample gas inlet nozzle 10a of the gas concentration measurement device 10 among the total hold-up in the flow path of the gas concentration measurement system, is sucked up from the seal pot 23, whose liquid level is maintained at the overflow level during normal operation, a level switch is installed in the seal pot 23 so as to output an abnormality signal to the control means 29, such as a CPU. As a result, even if the stored water in the seal pot 23 is sucked up due to a problem such as the above-mentioned blockage, the suction pump 11 built in the gas concentration measurement device 10 can be stopped by an output signal from the control means 29 before the sucked up stored water reaches the sample gas inlet nozzle 10a of the gas concentration measurement device 10, so that the stored water can be prevented from entering the gas concentration measurement device 10.

[0038] There is no particular limitation on the materials for the sampling tube 4, sample gas flow pipe 21, drain recovery pipe 22, bypass pipe 27, and cold air dispersion pipe 26, and various resins such as polyvinyl chloride, fluororesins such as PTFE (Poly Tetra Fluoro Ethylene), urethane resins, heat-resistant glass, and metals such as stainless steel can be used. Of these, it is preferable to use resin tubes. However, it is preferable not to use resins that have the property of adsorbing regulated substances to be measured in the parts that come into contact with the sample gas.

[0039] Furthermore, when the sample gas contains saturated water vapor at high temperature and also contains a corrosive liquid such as a caustic soda solution in the form of mist, it is preferable to use a fluororesin such as Teflon (registered trademark) that has excellent heat resistance and corrosion resistance. When the regulated substance to be measured is chlorine gas, a tube made of PTFE (Poly Tetra Fluoro Ethylene), which is not adsorbed to resin, can be preferably used. Although the embodiment of the drain removal device and the gas concentration measurement system equipped with the same according to the present invention have been described above, the present invention is not limited to the above embodiment and can include various modifications and alterations within the scope of the present invention. Next, the gas concentration measurement system of the present invention will be described more specifically by giving an example. EXAMPLES

[0040] In order to monitor the operating condition of a wet detoxification facility that detoxifies chlorine-containing factory exhaust gas discharged from a nickel hydrometallurgy plant, a portion of the treated gas discharged from the wet detoxification facility was sampled using a sampling tube 4 and introduced into a gas concentration measurement system configured as shown in Figure 1 to measure the chlorine concentration in the sample gas. The above-mentioned factory has a process that generates chlorine, so the exhaust gas generated in this process contains a very small amount of chlorine. This exhaust gas may also contain solids such as sulfur.

[0041] The detoxification equipment for detoxifying the above-mentioned chlorine-containing industrial exhaust gas introduces the above-mentioned industrial exhaust gas from the bottom of the tower and drops a caustic soda solution from the top of the packed tower to bring them into gas-liquid contact in a countercurrent flow, so that the chlorine contained in the industrial exhaust gas is absorbed by the caustic soda solution. By detoxifying the industrial exhaust gas using this packed tower, the chlorine gas concentration in the sample gas, which was about 5 to 10 ppm at the inlet of the packed tower, can be detoxified to almost zero at the outlet of the top of the packed tower.

[0042] The treated gas discharged from the top of this packed tower was saturated with water vapor, and its temperature fluctuated within a range of about 60°C to 100°C. Therefore, there was a risk of a large amount of drain water being generated by cooling with outside air, and since the exhaust gas may contain trace amounts of solids as described above, a PTFE tube with an inner diameter of 12 mm was used for the sampling tube 4 to prevent clogging of the sampling tube 4 by the drain water or solids. A gas concentration measuring device 10 having the structure shown in Fig. 2 was connected to the end of this sampling tube 4, and a drain removal device 20 having the structure shown in Fig. 3 was connected to the middle of the sampling tube 4 via a tube joint.

[0043] Specifically, a chlorine detector of the model SH-2713 manufactured by Bionix was used as the gas concentration measuring device 10. This chlorine detector is of the suction type as shown in FIG. 2, and the sample gas continuously sucked from the sample gas inlet nozzle 10a by the built-in suction pump 11 is introduced into the gas sampler 14 via the flowmeter 12 and the gas trap 13, where the concentration of the chlorine gas, which is the detection target substance in the sample gas, is measured by a diaphragm electrode type sensor. The measured value output from the gas sampler 14 is amplified by a signal converter and output as a gas concentration. The gas concentration measuring range of this chlorine detector is from 0 ppm to 3 ppm, and it is set to sound the first alarm at 0.3 ppm and the second alarm at 1.0 ppm.

[0044] On the other hand, in the drain removal device 20, a flow path was formed from a sample gas flow pipe 21 formed in a U-shape, a drain recovery pipe 22 branched off from the lowest part 21a of the sample gas flow pipe 21 by a tube joint and extending directly downward, and a bypass pipe 27 connected to the sample gas flow pipe 21 by a tube joint so as to bypass the branched part of the drain recovery pipe 22. Of these flow paths, the sample gas flow pipe 21 and the bypass pipe 27 were made of PTFE tubes with an inner diameter of 10 mm, and the drain recovery pipe 22 was made of PTFE tubes with an inner diameter of 12 mm and a length of 5000 mm.

[0045] Of the sample gas flow pipe 21, the two straight pipe sections 21b, excluding the lowest section 21a where the drain recovery pipe 22 and the bypass pipe 27 branch off, were passed through a cooling box 24 made of a polyvinyl chloride synthetic resin pipe with a nominal diameter of 100 mm, both ends of which were sealed with two caps. At that time, the two straight pipe sections 21b were inserted into insertion holes provided in each of the two caps. The diameter of these insertion holes was made several mm larger than the outer diameter of the straight pipe sections 21b, so that cold air supplied from a cold air generating means described later was exhausted from the gap between the insertion holes and the straight pipe sections 21b.

[0046] The upper cap of the cooling box 24 further has a nozzle on the central axis, and a cold air dispersion pipe 26 made of polyurethane and a circular pipe with an outer diameter of 10 mm and a closed end is attached to the inner end of the box so as to extend parallel to the straight pipe parts 21b between the two straight pipe parts 21b. As shown in Fig. 4(c), this cold air dispersion pipe 26 has multiple nozzles with a hole diameter of 1 mm, and the distance between adjacent nozzles in the vertical direction gradually increases from top to bottom, and these multiple nozzles are alternately arranged at an angle position facing the two straight pipe parts 21b and an angle position perpendicular to this angle position by 90°. As the cold air generating means 25, an AC-70C air cooler (vortex cooler) manufactured by Nissin Sangyo Co., Ltd. was used.

[0047] A seal pot 23 consisting of a cylindrical polyvinyl chloride container with a capacity of about 4000 mL up to the overflow outlet was provided at the lower end opening 22a of the drain recovery pipe 22 in order to seal the drain with the stored water derived from the drain water. An electrode-type level switch 28 was provided in this seal pot 23, and when the height equivalent to about half of the hold-up amount from the connection point with the drain removal device 20 to the sample gas inlet nozzle 10a of the gas concentration measurement device 10 among the total hold-up in the flow path of the gas concentration measurement system dropped from the liquid level maintained by overflow from the overflow outlet, an abnormality signal was output to the CPU as the control means 29, and when this abnormality signal was input, the control means 29 issued an alarm and stopped the operation of the suction pump 11 of the gas concentration measurement device 10.

[0048] In the gas concentration measurement system according to the embodiment of the present invention having the above-mentioned configuration, sample gas was extracted from the treated gas discharged from the top of the packed tower to the duct D through the sampling tube 4 so that the flow rate measured by the flow meter 12 was 2 L / min, and the sample gas was introduced into the gas concentration measurement device 10 through the drain removal device 20. In the gas concentration measurement device 10, the surplus gas was separated and removed by the gas trap 13, and finally, the sample gas was supplied to the gas sampler 14 at 0.5 L / min. Under these conditions, the chlorine gas concentration contained in the sample gas was monitored for six months. In the conventional system, blockage due to drain water occurred three times a year, and blockage due to ice occurred about three times a year. However, in the gas concentration measurement system described above, no troubles due to drain water generated from the sample gas or frozen ice occurred even once. [Explanation of symbols]

[0049] D Duct 1 packed tower 2 packed bed 3. Droplet removal means (demister) 4 Sampling tubes 10 Gas concentration measuring device 10a Sample gas inlet nozzle 10b Excess outlet nozzle 10c Exhaust gas outlet nozzle 11 Suction pump 12 Flow meter 13 Gas Trap 14 Gas Sampler 20 Drain removal device 21 Sample gas flow pipe 21a Bottom 21b Straight pipe section 22 Drain recovery pipe 22a Bottom opening 23 Seal Pot 23a Overflow outlet 24 Cooling box 25 Cold air generating means (vortex cooler) 26 Cold air distribution pipe 27 Bypass pipe 28 Level Switch 29 Control Means

Claims

1. a cooling box for cooling the sample gas by passing it through two straight pipe sections excluding the lowest part of the sample gas flow pipe; and a seal pot for sealing a lower end opening of the drain recovery pipe with water. The drain removal device condenses water vapor contained in sample gas extracted from treated gas in a wet type abatement facility and removes it as drain water, the drain removal device comprising: a sample gas flow pipe formed in a U-shape so as to be folded back at the lowest part; a cooling box for cooling the sample gas flow pipe by passing it through two straight pipe sections excluding the lowest part;

2. 2. The drain removal device according to claim 1, wherein a bypass pipe for bypassing a branched portion of the drain recovery pipe is provided at a lowermost portion of the sample gas flow pipe located outside the cooling box.

3. 2. The drain removal device according to claim 1, wherein the seal pot has an overflow discharge outlet above the lower end opening of the drain recovery pipe, and the liquid level is monitored so as to output an abnormality signal when the liquid level in the seal pot reaches or falls below a predetermined liquid level between the lower end opening and the overflow discharge outlet.

4. 4. The drain removal device according to claim 1, wherein the cold air generating means is a vortex cooler.

5. 4. A gas concentration measurement system comprising the drain removal device according to claim 3 and a gas concentration measurement device for measuring the concentration of regulated substances contained in the sample gas from which drain water has been removed by the drain removal device, wherein the gas concentration measurement device is controlled to stop a suction pump built therein when the abnormality signal is output.

Images