Water treatment system

Abstract

The present invention is a water treatment system comprising a water treatment device that includes a treatment unit which has accommodated therein an adsorbent for adsorbing and removing an organic solvent from water to be treated which contains the organic solvent. The water treatment device repeatedly performs an adsorption treatment in which the water to be treated supplied to the treatment unit is brought into contact with the adsorbent and treated water is discharged, and a desorption treatment in which the organic solvent is desorbed from the adsorbent by water vapor for desorption which is supplied to the treatment unit and desorption gas is discharged. The water treatment system is characterized by comprising: a heat exchanger that includes a heat generation unit through which the desorption gas discharged from the water treatment device passes and a heat absorption unit to which supplementary water is supplied, said heat exchanger indirectly heating the supplementary water in the heat absorption unit by means of the desorption gas passing through the heat generation unit to produce water vapor, and discharging the desorption gas which has passed through the heat generation unit; a cooling unit that cools the desorption gas discharged from the heat exchanger; and a regenerative water vapor line that supplies the water vapor produced by the heat exchanger to the water treatment device as at least part of the water vapor for desorption.

Description

Water Treatment Systems

[0001] The present invention relates to a system for removing and purifying organic substances from water to be treated (raw water) containing organic substances, and more particularly to a system for removing organic substances such as organic substances from wastewater from various factories and research facilities, leachate from final disposal sites, groundwater, etc.

[0002] One known example of a device for purifying water to be treated that contains organic substances is the adsorption-desorption type water treatment device described in Patent Document 1. The water treatment device described in Patent Document 1 continuously purifies the water to be treated by sequentially repeating an adsorption process in which water (water to be treated) is passed through an adsorption element to adsorb organic substances in the water to be treated onto the adsorption element, and a desorption process in which high-temperature heated gas is passed through the adsorption element to desorb the organic substances from the adsorption element.

[0003] Specifically, the water treatment device has two treatment sections, and while an adsorption process is performed by an adsorption element housed in one treatment section, an adsorption element housed in the other treatment section performs a desorption process. Then, at regular time intervals, the treatment section performing the adsorption process and the treatment section performing the desorption process are switched over, and the adsorption process is continuously performed by either treatment section, thereby enabling continuous purification of the water to be treated.

[0004] Japanese Patent Application Laid-Open No. 2006-55712

[0005] Recently, there has been a demand for energy saving and cost reduction in water treatment equipment.

[0006] The present invention is intended to solve the above problems, and has an object to provide a water treatment system that can be operated at low cost and that is energy-efficient.

[0007] The water treatment system of the present invention has the following configuration.

[0008] 1. A water treatment system comprising a treatment section containing an adsorbent that adsorbs and removes organic solvents from water to be treated that contains the organic solvents, and which repeats an adsorption process in which the water to be treated that is supplied to the treatment section is brought into contact with the adsorbent and treated water is discharged, and a desorption process in which the organic solvent is desorbed from the adsorbent using desorption steam supplied to the treatment section and a desorption gas is discharged, the water treatment system comprising: a heat exchanger having a heat generating section through which the desorption gas discharged from the water treatment section passes; and a heat absorption section to which makeup water is supplied, the heat exchanger indirectly heating the makeup water in the heat absorption section with the desorption gas passing through the heat generating section to generate steam, and discharging the desorbed gas after passing through the heat generating section; a cooling section that cools the desorbed gas discharged from the heat exchanger; and a recycled steam line that supplies the steam generated in the heat exchanger to the water treatment system as at least a part of the desorption steam. According to the above configuration, the water vapor generated by utilizing the heat of the desorption gas can be used as at least a part of the water vapor to be desorbed, which contributes to energy saving and cost reduction.

[0009] In addition to the above configuration, the water treatment system of the present invention may also include a treated water supply line that supplies at least a portion of the treated water to the heat exchanger as makeup water. During adsorption treatment, as the amount of organic matter adsorbed by the adsorbent approaches its saturated adsorption capacity, a phenomenon known as breakthrough occurs, in which some of the organic matter passes through the adsorbent without being adsorbed. As the flow of treated water continues, the concentration of the organic matter passing through gradually increases. However, with the above configuration, by supplying treated water as makeup water, the organic matter contained in the treated water discharged by breakthrough can be returned to the system, thereby reducing the total amount of organic matter discharged outside the system.

[0010] In addition to the above configuration, the water treatment system of the present invention may further include a heat exchanger condensate line through which condensate of the desorption gas discharged from the heat exchanger, condensed by passing through the heat generating section, bypasses the cooling section. With the above configuration, the condensate bypasses the cooling section, thereby reducing the energy used in the cooling section, thereby contributing to further energy conservation.

[0011] In addition to the above configuration, the water treatment system of the present invention may include a purge gas line that supplies a purge gas to the treatment section, and the water treatment device may perform a purge process that removes water adhering to the adsorbent using the purge gas before the desorption process. According to the above configuration, the adhering water can be removed by the purge process, thereby enabling the subsequent desorption process to be performed effectively. In other words, if adhering water remains on the adsorbent, heat is lost, lowering the temperature of the desorbed water vapor, which may prevent sufficient desorption. This can be prevented.

[0012] The water treatment system of the present invention may further include an adhering water discharge line for returning the adhering water discharged in the purging process to the inlet of the water treatment device. With this configuration, the adhering water discharged in the purging process can be treated again in the water treatment device together with the water to be treated.

[0013] The adsorbent may include at least one of activated carbon, zeolite, ion exchange resin, and activated alumina. The adsorbent may include activated carbon fiber.

[0014] According to the above-described configuration of the present invention, the water vapor generated by utilizing the heat of the desorption gas can be used as at least a part of the water vapor for desorption, and therefore, the present invention can provide a water treatment system that can be operated at low cost and is energy-efficient.

[0015] 1 is a conceptual diagram showing the configuration of a water treatment device according to a first embodiment;

[0016] Water treatment devices according to embodiments of the present invention will be described below with reference to the drawings. In the embodiments described below, when reference is made to numbers, quantities, etc., the scope of the present invention is not necessarily limited to those numbers, quantities, etc., unless otherwise specified. The same reference numerals will be used for the same or equivalent parts, and overlapping descriptions may not be repeated. It is intended from the outset that the configurations in the embodiments may be used in appropriate combinations.

[0017] Organic substances include methylene chloride, chloroform, carbon tetrachloride, ethylene chloride, trichloroethylene, tetrachloroethylene, o-dichlorobenzene, m-dichlorobenzene, Freon-112, Freon-113, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), propyl bromide, butyl iodide, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, vinyl acetate, methyl propionate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, diethyl carbonate, ethyl formate, diethyl ether, dipropyl ether, tetrahydrofuran, dibutyl ether, anisole, methanol, ethanol, isopropanol, n-butanol, 2-butanol, isobutanol, t-butanol, allyl alcohol, pentanol, heptanol, ethylene glycol, diethylene glycol, phenol, o-cresol, m-cresol, p-cresol, xylenol, acetone, This refers to methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, phorone, acrylonitrile, n-hexane, isohexane, cyclohexane, methylcyclohexane, n-heptane, n-octane, n-nonane, isononane, decane, dodecane, undecane, tetradecane, decalin, benzene, toluene, m-xylene, p-xylene, o-xylene, ethylbenzene, 1,3,5-trimethylbenzene, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide, as well as chemical substances classified as perfluoroalkyl compounds and polyfluoroalkyl compounds (PFAS) (perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorobutanesulfonic acid (PFBS), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS), perfluorocarboxylic acids (PFCAs), fluorotelomer alcohols (FTOHs), etc.).

[0018] [First Embodiment] A water treatment system 100A according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the water treatment system 100A according to the first embodiment. The water treatment system 100A includes a water treatment device 1 and a heat exchanger 112.

[0019] The water treatment device 1 includes a first treatment section 102A and a second treatment section 102B. The first treatment section 102A contains a first adsorbent 103A, and the second treatment section 102B contains a second adsorbent 103B. The first adsorbent 103A and the second adsorbent 103B adsorb and remove organic solvents from the water to be treated. The first treatment section 102A and the second treatment section 102B repeatedly perform an adsorption process (adsorption treatment) in which the water to be treated is brought into contact with the adsorbent and the treated water is discharged, and a desorption process (desorption treatment) in which the organic solvent is desorbed from the adsorbent using desorption steam and the desorbed gas is discharged. The first adsorbent 103A and the second adsorbent 103B are, for example, activated carbon fiber. However, the first adsorbent 103A and the second adsorbent 103B may also be made of at least one of activated carbon, zeolite, ion exchange resin, and activated alumina.

[0020] The first treatment unit 102A and the second treatment unit 102B are connected to a water line 101 to be treated and a treated water line 104. Opening and closing valves V1 and V2 are provided to control supply / receive from the water line 101 to the first treatment unit 102A and the second treatment unit 102B, and the treated water line 104 is provided with opening and closing valves V3 and V4 to control discharge / non-discharge of the treated water.

[0021] Furthermore, the first processing unit 102A and the second processing unit 102B are connected to a desorption water vapor line 105 and a desorption outlet gas line 108. Open / close valves V5 and V6 are provided for controlling supply / non-supply from the desorption water vapor line 105 to the first processing unit 102A and the second processing unit 102B, and open / close valves V7 and V8 are provided for controlling discharge / non-discharge from the desorption outlet gas line 108 to the first processing unit 102A and the second processing unit 102B.

[0022] The desorption outlet gas line 108 branches into an attached water discharge line 107 and a heat exchanger inlet line 116. The attached water discharge line 107 is a line for returning the discharged attached water to the water to be treated, that is, returning it to the inlet of the water treatment device 1.

[0023] A heat exchanger 112 is connected to the heat exchanger inlet line 116. The heat exchanger 112 has a desorption outlet gas inlet chamber C1. The heat exchanger 112 also has a desorption outlet gas outlet chamber C2, which is connected to the heat exchanger outlet line 109. Furthermore, makeup water is supplied to the heat absorption part of the heat exchanger 112 from a makeup water supply line. The makeup water is supplied to the heat absorption part of the heat exchanger 112 by, for example, a liquid feed pump.

[0024] The heat exchanger 112 indirectly heats the makeup water with the desorption outlet gas supplied through the heat exchanger inlet line 116, thereby evaporating the makeup water and generating steam.

[0025] The heat absorption section of the heat exchanger 112 is decompressed so that the boiling point is, for example, between 60°C and 97°C, preferably between 75°C and 95°C. The generated steam is supplied as regenerated steam to the steam compressor 111 through a regenerated steam line 113 connected to the heat exchanger 112. The steam compressor 111 is a mechanism that uses high-pressure steam as a driving source (hereinafter referred to as driving steam) to draw in low-pressure steam (hereinafter referred to as suction steam) in a reduced pressure state and then pressurize it to medium-pressure steam (hereinafter referred to as discharge steam). In the present invention, high-pressure steam is supplied to the steam compressor 111 through the compressor steam line 117 as driving steam, and the regenerated steam is drawn in through the regenerated steam line 113 as suction steam, and a mixture of the steam and regenerated steam is discharged as discharge steam through the desorption steam line 105. The desorption steam discharged from the steam compressor 111 is supplied to the first treatment unit 102A or the second treatment unit 102B, where the desorption step is being performed, through the desorption steam line 105. Note that the steam compressor 111 may be replaced by a compressor having a similar effect, such as a roots blower or a turbo blower.

[0026] The heat exchanger 112 is preferably a multi-tube heat exchanger. A multi-tube heat exchanger is a heat exchanger in which multiple tubes 118 are arranged inside a cylinder called a shell 119. The surfaces of the tubes act as heat transfer surfaces, and heat is exchanged between the fluid flowing inside the tubes 118 (hereinafter referred to as the tube side) and the fluid flowing between the outside of the tubes 118 and the inside of the shell 119 (hereinafter referred to as the shell side). The tubes 118 connect the desorption outlet gas inlet chamber C1 and the desorption outlet gas outlet chamber C2. Furthermore, in the heat exchanger 112 of the present invention, the tubes 118 are arranged horizontally, and the tube side acts as a heat-generating part (condensation side) through which the desorbed gas passes, while the shell side acts as a heat-absorbing part (evaporation side) that generates water vapor. Other types of equipment that have similar effects as a heat exchanger may be used instead, such as plate-type or spiral-type structures.

[0027] Make-up water always remains in the shell 119 in an amount that allows it to come into contact with a portion of the tubes 118. When the make-up water comes into contact with the tubes 118, the make-up water receives heat from the desorbed gas and evaporates. In addition, the tubes 118 also serve to heat the make-up water to its evaporation temperature, so there is no need to provide a separate make-up water heating facility.

[0028] Possible means for adjusting the water level of makeup water in the heat exchanger 112 include control methods using, for example, a float type, a disspacer type, a differential pressure type, or a capacitance type level gauge.

[0029] The desorption outlet gas outlet chamber C2 of the heat exchanger 112 is connected to the heat exchanger outlet line 109 and to the condenser 110, which is a cooling unit. Inside the condenser 110, heat exchange occurs between the desorbed gas that has completed heat exchange in the heat exchanger 112 and cooling water, and the desorbed gas is cooled and condensed.

[0030] A heat exchanger condensate line 120 is connected to the desorption outlet gas outlet chamber C2 of the heat exchanger 112. After passing through the tubes 118 of the heat exchanger 112 and completing the heat exchange, the desorbed gas is separated into uncondensed desorption outlet gas and condensed condensate, which are supplied to the desorption outlet gas outlet chamber C2. The condensate of the desorption outlet gas supplied to the desorption outlet gas outlet chamber C2 passes through the heat exchanger condensate line 120, allowing the condensate to bypass the condenser 110, thereby reducing the amount of cooling water used in the condenser 110.

[0031] The purge gas line 106 is connected to the desorption steam line. The purge gas line is provided with an on-off valve V10 for controlling the supply / non-supply of purge gas. It is preferable to remove water adhering to the adsorbent by supplying a purge gas. The purge gas may be steam or air, but steam is preferred.

[0032] In the water treatment apparatus having the above configuration, the operation and opening / closing of the on-off valves V1 to V10, the heat exchanger 112, the steam compressor 111, and the condenser 110 are appropriately controlled by a control device (not shown) so as to realize the gas treatment method described below.

[0033] (Gas Treatment Method) A water treatment method using the water treatment device having the above configuration will be described. In Fig. 1, a first treatment section 102A of the water treatment device performs a desorption process, and a second treatment section 102B performs an adsorption process.

[0034] (Adsorption step in second treatment unit 102B) The water to be treated containing organic substances is sent to second treatment unit 102B, which is in an adsorption step, via water to be treated line 101. Opening and closing valves V2 and V4 are controlled to be open, and V6 and V8 are controlled to be closed.

[0035] The organic substances are adsorbed by the second adsorbent 103B of the second treatment section 102B, and the treated water is discharged to the outside of the system through the treated water line. The opening / closing valve V6 of the desorption water vapor line 105 is controlled to be in a closed state.

[0036] (Desorption step of first treatment unit 102A) No water to be treated is sent to the first treatment unit 102A, the water to be treated line 101 is closed by the on-off valve V1, and the on-off valve V7 of the desorption outlet gas line 108 is controlled to be open. Desorbed water vapor is supplied to the first adsorbent 103A through the desorption water vapor line 105. The on-off valves V1 and V9 of the desorption water vapor line 105 are controlled to be open.

[0037] The steam for desorption is generated by mixing steam supplied from a compressor steam line 117 and regenerated steam supplied from a regenerated steam line 113 in a steam compressor 111. The steam compressor 111 is driven by steam supplied through the compressor steam line 117, sucks regenerated steam in a reduced pressure state through the regenerated steam line 113, and discharges desorption steam, which is a mixture of steam and regenerated steam, through a desorption steam line 105.

[0038] In the first processing unit 102A, desorption water vapor is ejected, and the organic substances adsorbed to the first adsorbent 103A are desorbed from the first adsorbent 103A.

[0039] The desorption outlet gas is supplied to the tube side of the heat exchanger 112 and exchanges heat with makeup water remaining on the shell side of the heat exchanger 112. Specifically, the makeup water is indirectly heated through the heat transfer surface.

[0040] (When the purging step is performed) When the purging step (purging treatment) is performed, it is performed immediately after the adsorption step is completed and before the desorption step is started. In the purging step, the on-off valves V6, V8, and V10 are controlled to be open to supply purge gas. The purge outlet gas containing adhering water passes through the adhering water discharge line 107 and merges with the line for treated water.

[0041] At the beginning of the desorption process, the supplied water vapor loses heat to the adhering water on the adsorbent, the treatment unit body, the piping, the switching valve, etc., resulting in a low temperature of the desorption outlet gas discharged from the treatment unit. As a result, the temperature of the desorption outlet gas flowing into the tube side of the heat exchanger 112 drops, and it is possible that a sufficient amount of makeup water cannot be evaporated. However, if purging with water vapor is performed in the purge gas process, not only will the adhering water be removed, but the treatment unit body, the piping, the switching valve, etc. will also be heated. Therefore, at the beginning of the next desorption process, the desorption outlet gas flows into the heat exchanger 112 at a high temperature, ensuring a sufficient amount of makeup water to evaporate, and the desorption process will be carried out efficiently.

[0042] After a certain period of time has passed, the adsorption process and desorption process are switched over, with first treatment unit 102A performing the adsorption process and second treatment unit 102B performing the desorption process. In this way, the water treatment device can continuously treat organic substances by alternately performing the adsorption and desorption processes.

[0043] The above describes a process in which the water treatment device 1 alternately performs an adsorption process and a desorption process using the first treatment device 102A and the second treatment device 102B, but the water treatment device 1 is not limited to having two treatment devices, and may have three or more treatment devices.

[0044] Second Embodiment A water treatment system 100B according to a second embodiment will be described with reference to Fig. 2. Fig. 2 is a diagram showing the configuration of a water treatment system 100B according to a second embodiment.

[0045] The basic configuration of water treatment system 100B is similar to that of water treatment system 100A described above. The difference is that water treatment system 100B is provided with treated water supply line 115 that supplies treated water to heat exchanger 112 as make-up water, in addition to the water treatment system 100A.

[0046] By supplying treated water as make-up water, organic substances contained in the treated water discharged by breakthrough can be returned to the system, thereby reducing the total amount of organic substances discharged outside the system. Organic substances remaining on the shell side of the heat exchanger 112 can be evaporated together with the water and supplied to the adsorption section as desorbed gas, or, if they are concentrated in the shell of the heat exchanger 112, makeup water can be blown out. Additionally, if it is desired to further reduce the amount of organic substances discharged outside the system, a configuration may be adopted in which treated water with a high concentration in the latter half of breakthrough is actively returned to the system using a tank or the like. Through these processes, the water treatment system 100B can reduce the amount of organic substances discharged from the treated water by several to 20% compared to the water treatment system 100A without compromising economic rationality.

[0047] The embodiments disclosed above should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0048] The present invention makes it possible to provide a water treatment system that can be operated at low cost and that is energy-efficient, thereby making a great contribution to the industrial world.

[0049] 1: water treatment device, 100A, 100B: water treatment system, 101: line for water to be treated, 102A: first treatment unit, 102B: second treatment unit, 103A: first adsorbent, 103B: second adsorbent, 104: treated water line, 105: water vapor line for desorption, 106: purge gas line, 107: attached water discharge line, 108: desorption outlet gas line, 109: heat exchanger outlet line, 110: condenser, 11 1: steam compressor, 112: heat exchanger, 113: regenerated steam line, 114: makeup water supply line, 115: treated water supply line, 116: heat exchanger inlet line, 117: compressor steam line, 118: tube, 119: shell, 120: heat exchanger condensate line, C1: desorption outlet gas inlet chamber, C2: desorption outlet gas outlet chamber, V1 to V10: on / off valves.

Claims

1. A water treatment system comprising a treatment section containing an adsorbent that adsorbs and removes organic solvents from water to be treated that contains organic solvents, and which repeats an adsorption process in which the water to be treated that is supplied to the treatment section is brought into contact with the adsorbent and treated water is discharged, and a desorption process in which the organic solvent is desorbed from the adsorbent using desorption steam supplied to the treatment section and a desorption gas is discharged, the water treatment system comprising: a heat exchanger having a heat generating section through which the desorption gas discharged from the water treatment section passes; and a heat absorption section to which makeup water is supplied, the heat exchanger indirectly heating the makeup water in the heat absorption section with the desorption gas passing through the heat generating section to generate steam, and discharging the desorbed gas after passing through the heat generating section; a cooling section that cools the desorption gas discharged from the heat exchanger; and a recycled steam line that supplies the steam generated in the heat exchanger to the water treatment system as at least a part of the desorption steam.

2. The water treatment system according to claim 1, further comprising a treated water supply line for supplying at least a portion of the treated water to the heat exchanger as the make-up water.

3. A water treatment system as described in claim 1 or 2, characterized in that it is provided with a heat exchanger condensate line through which the condensate of the desorption gas discharged from the heat exchanger, condensed by passing through the heat generating section, bypasses the cooling section.

4. A water treatment system as described in claim 1 or 2, characterized in that it is provided with a purge gas line that supplies purge gas to the processing unit, and the water treatment device performs a purge process to remove water adhering to the adsorbent using the purge gas before the desorption process.

5. The water treatment system according to claim 4, further comprising an adhesion water discharge line for returning adhesion water discharged in the purging process to the inlet of the water treatment device.

6. The water treatment system according to claim 1 or 2, wherein the adsorbent material includes at least one of activated carbon, zeolite, ion exchange resin, and activated alumina.

7. The water treatment system according to claim 1 or 2, wherein the adsorbent material includes activated carbon fiber.

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