A treatment process and system for salt-containing mixed-acid wastewater

Abstract

The present application relates to a kind of salt-containing, mixed acid wastewater treatment process and system.The process includes the following steps: primary evaporation;Extraction;Secondary evaporation;Centrifugal.The system includes: wastewater storage tank;Evaporation tower, which is communicated with wastewater storage tank and carries out primary evaporation, secondary evaporation to wastewater;Cooling tower, which is communicated with evaporation tower upper outlet and carries out low-temperature condensation to evaporation tower upper outlet steam;Extraction separator, which is communicated with evaporation tower lower outlet and carries out extraction to the primary concentrated liquid obtained by primary evaporation of evaporation tower lower outlet;Centrifugal unit;And storage unit.Compared with prior art, the present application can realize wastewater, waste liquid resource utilization, reduce reagent neutralization cost, reduce wastewater treatment energy consumption, and reduce crystallization of miscellaneous salt.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wastewater recovery and treatment, and particularly relates to a treatment process and system for salt-containing and mixed-acid wastewater. BACKGROUND

[0002] Most of the chemical waste liquid has the characteristics of high acid concentration, high organic matter content, high colority, high salt content, complex water quality composition, and poor biodegradability. When the conventional physical and chemical and biochemical processes cannot meet the treatment requirements, various physical and chemical, advanced oxidation (AOPs) and other means are needed to pretreat the chemical process waste liquid, and then the evaporation crystallization process is used for desalination. The existing evaporation crystallization technology for treating high-concentration and high-organic wastewater generally uses multi-effect evaporator and mechanical vapor recompression evaporator.

[0003] The existing technology principle mostly uses vacuum negative pressure to realize low-temperature boiling of the solution, such as mechanical vapor recompression technology (MVR) and multi-effect evaporation technology (MEE). The high negative pressure evaporation condition requires that the equipment material has sufficient structural strength and thickness, and the material under mixed acid conditions requires excellent corrosion resistance. It is necessary to select the precious metal materials on the market, such as hastelloy and titanium metal. Or use a relatively complex anticorrosion material process, which has great difficulty in process, and the anticorrosion effect and service life need to be verified.

[0004] MVR and MEE both need a large-power vacuum pump, and the vacuum system is easily affected by low-boiling substances, volatile substances, and salt. Hydrochloric acid volatilization acid mist, and partial thermal decomposition of salt such as ammonium chloride and triethylamine acetate will cause acid mist corrosion to the vacuum system, which has a fatal impact on the material and service life of the vacuum pump, and the cost of key components of the equipment increases. If a rectifying column is used for rectification and separation of the waste liquid, the corrosion resistance of the rectifying column is extremely high, and the existing precious metal material is difficult to meet the corrosion of high-concentration hydrochloric acid. If a material or process with strong corrosion resistance is used, the overall tower uses a large amount of material, and the cost is too high, which the enterprise cannot bear.

[0005] At present, the evaporation technology is prone to produce foam and tar (foam produced by saponification of organic matter, tar produced by polycondensation of organic matter at high temperature) when the solution boils, especially in a system containing a large amount of organic matter. The foam enters the condensation phase, resulting in poor water quality and great influence on the quality of separated components, which has a negative impact on recycling. Tar has an impact on heat exchange in the evaporation process and is not easy to peel off.

[0006] Concentration evaporation is mostly treated by acid-base neutralization, and then concentrated and evaporated in a neutral system, which increases the neutralization cost of reagents, the energy consumption of wastewater treatment (salt content increases), and brings the problem of treatment of crystallization of mixed salt. The cost of waste liquid treatment is high, which increases the burden of enterprises. SUMMARY

[0007] The present application aims to provide a salt-containing and mixed-acid wastewater treatment process and system to overcome the defects of the prior art.

[0008] The object of the present application can be achieved by the following technical solutions.

[0009] The present application provides a salt-containing and mixed-acid wastewater treatment system in the first aspect, which comprises:

[0010] a wastewater storage tank;

[0011] an evaporation tower in communication with the wastewater storage tank and configured to evaporate the wastewater;

[0012] a cooling tower in communication with an upper outlet of the evaporation tower and configured to condense the vapor from the upper outlet of the evaporation tower at a low temperature;

[0013] an extraction separator in communication with a lower outlet of the evaporation tower and configured to extract the concentrated liquid obtained by evaporation from the lower outlet of the evaporation tower;

[0014] a centrifugal unit in communication with the extraction separator and configured to separate the solid-liquid mixture after extraction in the extraction separator; and

[0015] a storage unit having a plurality of storage tanks and in communication with the evaporation tower, the cooling tower, the extraction separator, and the centrifugal unit, respectively.

[0016] Further, the system further comprises a gas supply unit;

[0017] The gas supply unit comprises:

[0018] a blower in communication with the evaporation tower;

[0019] wherein the blower supplies air or nitrogen to the evaporation tower to increase the reaction rate of evaporation and provide the power for evaporation;

[0020] a nitrogen source in communication with the evaporation tower and configured to provide the power for evaporation; and

[0021] a nitrogen circulation pipeline having two ends in communication with the evaporation tower and the cooling tower, respectively, so as to circulate the nitrogen in the evaporation tower and the cooling tower.

[0022] wherein the blower is suitable for use in the case of non-explosive limit of toxic and harmful substances, and the nitrogen source is suitable for use in the case of explosive limit of toxic and harmful substances.

[0023] Further, the system further comprises a heat exchange unit;

[0024] The heat exchange unit comprises:

[0025] a first heat exchanger in communication with the evaporation tower and configured to provide the heat required for evaporation in the evaporation tower; and

[0026] a second heat exchanger in communication with the remaining cooling tower and configured to provide refrigerated water required by the cooling tower for low-temperature condensation.

[0027] Further, the storage unit comprises:

[0028] a first storage tank connected to the centrifugal unit and configured to store the product after centrifugation by the centrifugal unit;

[0029] a second storage tank in communication with the cooling tower and the extraction separator respectively, and configured to provide the extraction agent to the extraction separator;

[0030] a third storage tank connected to the evaporation tower and configured to receive the product after evaporation by the evaporation tower;

[0031] a fourth storage tank connected to the cooling tower and configured to receive the product after low-temperature condensation by the cooling tower; and

[0032] a fifth storage tank in communication with the extraction separator at one end and in communication with the evaporation tower at the other end, and configured to input the supernatant after extraction by the extraction separator into the evaporation tower.

[0033] Further, the centrifugal unit comprises:

[0034] a cyclone in communication with the extraction separator and configured to separate solid and liquid; and

[0035] a centrifuge in communication with the cyclone and configured to centrifugally separate.

[0036] The present application also provides a treatment process for salt-containing and mixed-acid wastewater, which is executed by using the above-mentioned treatment system for salt-containing and mixed-acid wastewater containing phosphoric acid, hydrochloric acid and DMF, and the treatment process comprises the following steps:

[0037] S1: primary evaporation: the wastewater is introduced into the evaporation tower for primary evaporation, and the steam obtained after primary evaporation is introduced into the cooling tower for low-temperature condensation to obtain hydrochloric acid, which is introduced into the fourth storage tank for storage, and the remaining in the evaporation tower is a primary concentrated solution;

[0038] S2: extraction: the primary concentrated solution in S1 is introduced into the extraction separator for extraction separation, to obtain a primary extraction supernatant introduced into the fifth storage tank, and an extraction solid-phase mixture;

[0039] S3: secondary evaporation: the primary extraction supernatant in the fifth storage tank in S2 is introduced into the evaporation tower for secondary evaporation, wherein the steam obtained after secondary evaporation is introduced into the cooling tower for low-temperature condensation to obtain a first product, and the remaining in the evaporation tower is DMF, which is introduced into the third storage tank for storage;

[0040] S4: centrifugation: centrifuging the extraction solid phase mixture in S2 to obtain phosphoric acid, and then the phosphoric acid is introduced into the first storage tank for storage.

[0041] Further, in S1, the temperature of the first evaporation is 20-95°C.

[0042] Further, in S2, carbon disulfide is added to the extraction separator from the second storage tank during extraction.

[0043] In S3, the first product is carbon disulfide, which is introduced into the second storage tank.

[0044] Further, in S3, the temperature of the second evaporation is 10-40°C.

[0045] Further, in S1 and S3, the temperature of the low-temperature condensation is -15-0°C.

[0046] Preferably, in S1, the temperature of the first evaporation is 65-95°C.

[0047] More preferably, in S1, the temperature of the first evaporation is 85°C.

[0048] Preferably, in S3, the temperature of the second evaporation is 40°C.

[0049] Preferably, in S1 and S3, the temperature of the low-temperature condensation is -10°C.

[0050] It should be noted that the temperature set for the evaporation tower varies according to the actual situation. Under standard atmospheric pressure, the evaporation temperature can be set according to the boiling point of the low-boiling-point solvent, such as methanol 64.7°C, acetone 56.48°C, and carbon disulfide 46.2°C. Water and acid gases are transferred from the liquid phase to the gas phase system, constantly taking away the temperature, while the first heat exchanger provides the heat required for gasification by saturated steam.

[0051] Because the evaporation temperature is low, under normal pressure or slightly positive pressure conditions, water vapor comes out first during the evaporation process of the system, followed by hydrochloric acid mist, which can be collected in stages according to the concentration of the produced acid. After the dilute acid and concentrated acid are distinguished, their specific uses for resource utilization can be determined. This process avoids the influence of boiling and foam accumulation on the quality of the produced water.

[0052] It should be noted that the application of the gas supply unit is only to provide evaporation power and to provide wind power to speed up the evaporation process. In the low temperature state, the water content in the air is continuously increased by the way of air blowing, and then the water in the waste liquid is continuously removed by low temperature condensation. This process takes advantage of the high volatility of hydrochloric acid. After the temperature is raised, hydrochloric acid can be easily separated from the material system and collected by condensation. Under the conditions of temperature and pressure, DMF, phosphoric acid and salt will not be easily carried away by nitrogen from the evaporation tower.

[0053] It should be noted that the following processes mainly occur in the cooling tower: the condensed air carrying water and acid gas after evaporation is subjected to deep cooling (temperature control -15℃-0℃) condensation, and nitrogen can be recycled. The wet air containing water or acid gas is countercurrently contacted with the washing liquid, the temperature is lowered, the water and acid gas in the air are released and condensed into liquid, and the heat is taken away by the chilled water through the heat exchange unit.

[0054] It should be noted that the material of the evaporation tower and the cooling tower is not limited. In the present application, the evaporation tower and the cooling tower adopt the form of a regular packed tower with low cost, and the material is plastic-based, which avoids the corrosion of strong acid medium and halogen salt on the equipment. The investment cost and the reagent addition cost of the evaporation equipment are reduced, and the evaporation tower can be used not only for separating hydrochloric acid, but also for separating phosphoric acid, extractant and salt-containing wastewater by using the difference in boiling point. The evaporation tower and the cooling tower are both provided with a wire mesh demister at the top, which is used to remove the liquid droplets carried by the secondary steam after separation, so as to prevent the product from being contaminated, wasted or the chilled water from being contaminated.

[0055] Compared with the prior art, the present application has the following advantages:

[0056] (1) The present application realizes the resource utilization of wastewater and waste liquid. Taking the wastewater containing hydrochloric acid, phosphoric acid and DMF as an example, hydrochloric acid is separated from the mixed system under the stripping action of air and is recovered in the condensation phase; phosphoric acid and DMF remain in the system due to their positive pressure and low evaporation temperature, and are used as the mixed product after concentration to enter the next process for continuous evaporation and collection. After the different products are distinguished, their specific uses for resource utilization can be determined, which has strong economic efficiency.

[0057] (2) The present application has simple equipment material, low cost and strong corrosion resistance. The evaporation tower and the cooling tower can adopt the form of a plastic packed tower with low cost, which avoids the corrosion of strong acid medium and halogen salt on the equipment, reduces the investment cost and the reagent addition cost of the evaporation equipment, and can be used not only for separating hydrochloric acid, but also for separating phosphoric acid, extractant and salt-containing wastewater by using the difference in boiling point.

[0058] (3) The application realizes the recycling of raw materials. Taking wastewater containing hydrochloric acid, phosphoric acid and DMF as an example, DMF and CS2 system, after evaporation to recover the solvent, the extractant can be recycled and the consumption rate is low; the remaining high-boiling-point DMF is discharged into the storage tank as a crude product for purification.

[0059] (4) The application reduces the influence of boiling and foam accumulation on water quality. Taking wastewater containing hydrochloric acid, phosphoric acid and DMF as an example, because the evaporation temperature is low, during the evaporation process of the system, under normal pressure or slightly positive pressure, water vapor is evaporated first, then hydrochloric acid mist, which can be collected in stages according to the concentration of the produced acid after condensation. Therefore, the generation and accumulation of boiling and foam are effectively avoided.

[0060] (5) The application has strong popularization and replicability. For wastewater containing pollutants with different boiling points, raw materials can be recovered according to the evaporation temperature. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 The figure is a schematic diagram of the device process of the application in Example 1.

[0062] Markings in the figure:

[0063] 1-wastewater tank, 2-evaporation tower, 3-cooling tower, 4-extraction separator, 5-centrifugal unit, 501-cyclone, 502-centrifuge, 6-storage unit, 601-first storage tank, 602-second storage tank, 603-third storage tank, 604-fourth storage tank, 605-fifth storage tank, 7-heat exchange unit, 701-first heat exchanger, 702-second heat exchanger, 8-gas supply unit, 801-blower, 802-nitrogen source, 803-nitrogen circulation pipeline. DETAILED DESCRIPTION

[0064] The application will be described in detail below in combination with the drawings and specific examples. The present embodiment is implemented on the basis of the technical solution of the application, and gives a detailed implementation and specific operation process, but the protection scope of the application is not limited to the following examples.

[0065] In the technical solution, if the part model, material name, connection structure, control method and other features are not explicitly stated, they are considered as common technical features disclosed in the prior art.

[0066] In the description of the application, it should be understood that the terms "upper", "lower", "vertical", "horizontal", "top", "bottom" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0067] In the description of the present application, the meaning of "a plurality of" is two or more than two, unless otherwise explicitly specified. In addition, the terms "mounting", "connecting", "connecting" should be broadly understood, for example, it can be fixed connection, or detachable connection or integrated connection; it can be bolted connection, or welded connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0068] In order to utilize wastewater, waste liquid resources, reduce neutralization cost of reagents, reduce energy consumption of wastewater treatment, and reduce the treatment problem of crystallization of impure salt, the present application provides a treatment system for salt-containing and mixed acid wastewater, the structure of which is shown in Figure 1 The system comprises:

[0069] a wastewater storage tank 1;

[0070] an evaporation tower 2, which is in communication with the wastewater storage tank 1 and evaporates wastewater;

[0071] a cooling tower 3, which is in communication with the upper outlet of the evaporation tower 2 and low-temperature condenses the steam from the upper outlet of the evaporation tower 2;

[0072] an extraction separator 4, which is in communication with the lower outlet of the evaporation tower 2 and extracts the concentrated liquid obtained by evaporation from the lower outlet of the evaporation tower 2;

[0073] a centrifugal unit 5, which is in communication with the extraction separator 4 and separates the solid-liquid mixture after extraction in the extraction separator 4; and

[0074] a storage unit 6, which has a plurality of storage tanks and is in communication with the evaporation tower 2, the cooling tower 3, the extraction separator 4, and the centrifugal unit 5, respectively.

[0075] In some specific embodiments, referring to Figure 1 The system further comprises a gas supply unit 8;

[0076] The gas supply unit 8 comprises:

[0077] a blower 801, which is in communication with the evaporation tower 2;

[0078] a nitrogen source 802, which is in communication with the evaporation tower 2 and is used to provide evaporation power; and

[0079] a nitrogen circulation pipeline 803, which is in communication with the evaporation tower 2 and the cooling tower 3 at both ends to circulate nitrogen in the evaporation tower 2 and the cooling tower 3.

[0080] In some embodiments, referring again to Figure 1 as shown, the heat exchange unit 7 further comprises:

[0081] The heat exchange unit 7 comprises:

[0082] a first heat exchanger 701, which is in communication with the evaporation tower 2 and is used to provide the heat required for the evaporation of the evaporation tower 2; and

[0083] a second heat exchanger 702, which is in communication with the cooling tower 3 and is used to provide the chilled water required for the low-temperature condensation of the cooling tower 3.

[0084] In some embodiments, referring again to Figure 1 as shown, the storage unit 6 comprises:

[0085] a first storage tank 601, which is connected to the centrifugal unit 5 and is used to store the product after centrifugation of the centrifugal unit 5;

[0086] a second storage tank 602, which is in communication with the cooling tower 3 and the extraction separator 4, respectively, and is used to provide the extraction agent to the extraction separator 4;

[0087] a third storage tank 603, which is connected to the evaporation tower 2 and is used to receive the product after evaporation of the evaporation tower 2;

[0088] a fourth storage tank 604, which is connected to the cooling tower 3 and is used to receive the product after low-temperature condensation of the cooling tower 3; and

[0089] a fifth storage tank 605, one end of which is in communication with the extraction separator 4, and the other end of which is in communication with the evaporation tower 2, and the supernatant extracted by the extraction separator 4 is input into the evaporation tower 2.

[0090] In some embodiments, referring again to Figure 1 as shown, the centrifugal unit 5 comprises:

[0091] a cyclone 501, which is in communication with the extraction separator 4 and performs solid-liquid separation; and

[0092] a centrifuge 502, which is used for centrifugal separation in conjunction with the cyclone 501.

[0093] The second aspect of the present application provides a treatment process for salt-containing and mixed-acid wastewater, which is executed by using the above-mentioned treatment system for salt-containing and mixed-acid wastewater containing phosphoric acid, hydrochloric acid, and DMF. The treatment process comprises the following steps:

[0094] S1: primary evaporation: the wastewater is introduced into the evaporation tower 2 for primary evaporation, and the steam obtained by the primary evaporation is introduced into the cooling tower 3 for low-temperature condensation to obtain hydrochloric acid, and the hydrochloric acid is introduced into the fourth storage tank 604 for storage, and the remaining in the evaporation tower 2 is a primary concentrated solution;

[0095] S2: extraction: the primary concentrated solution in S1 is introduced into the extraction separator 4 for extraction separation, to obtain a primary extraction supernatant introduced into the fifth storage tank 605, and to obtain an extraction solid-phase mixture;

[0096] S3: secondary evaporation: the primary extraction supernatant in the fifth storage tank 605 in S2 is introduced into the evaporation tower 2 for secondary evaporation, wherein the steam of the secondary evaporation is introduced into the cooling tower 3 for low-temperature condensation to obtain a first product, and the remaining DMF in the evaporation tower 2 is introduced into the third storage tank 603 for storage;

[0097] S4: centrifugation: the extraction solid-phase mixture in S2 is introduced into the cyclone 501 and the centrifuge 502 to obtain phosphoric acid, and the phosphoric acid is introduced into the first storage tank 601 for storage.

[0098] In some specific embodiments, in S1, the temperature of the primary evaporation is 20-95°C.

[0099] In some specific embodiments, in S2, carbon disulfide is added to the extraction separator 4 from the second storage tank 602 during the extraction;

[0100] In S3, the first product is carbon disulfide, and the first product is introduced into the second storage tank 602.

[0101] In some specific embodiments, in S3, the temperature of the secondary evaporation is 10-40°C.

[0102] In some specific embodiments, in S1 and S3, the temperature of the low-temperature condensation is -15-0°C.

[0103] Each of the above embodiments can be implemented alone or in any combination of two or more.

[0104] The above embodiments will be described in more detail below in conjunction with specific examples.

[0105] Example 1

[0106] In order to resource utilization of wastewater and waste liquid, reduce the cost of neutralization, reduce the energy consumption of wastewater treatment, and reduce the treatment problem of crystallization of impurities, the present embodiment provides a treatment system for salt-containing and mixed acid wastewater, the structure of which is shown in Figure 1 The system comprises:

[0107] a wastewater storage tank 1;

[0108] an evaporation tower 2, which is in communication with the wastewater storage tank 1 and evaporates the wastewater;

[0109] a cooling tower 3, which is in communication with the upper outlet of the evaporation tower 2 and low-temperature condenses the steam from the upper outlet of the evaporation tower 2;

[0110] an extraction separator 4, which is in communication with the lower outlet of the evaporation tower 2 and extracts the concentrated liquid obtained by evaporation from the lower outlet of the evaporation tower 2;

[0111] a centrifugal unit 5, which is in communication with the extraction separator 4 and separates the solid-liquid mixture after extraction by the extraction separator 4; and

[0112] a storage unit 6, which has a plurality of storage tanks and is in communication with the evaporation tower 2, the cooling tower 3, the extraction separator 4, and the centrifugal unit 5, respectively.

[0113] Please refer to Figure 1 again, the gas supply unit 8 is further included;

[0114] The gas supply unit 8 includes:

[0115] a blower 801, which is in communication with the evaporation tower 2;

[0116] a nitrogen source 802, which is in communication with the evaporation tower 2 and is used to provide evaporation power; and

[0117] a nitrogen circulation pipeline 803, which is in communication with the evaporation tower 2 and the cooling tower 3 at both ends, so that the nitrogen circulates in the evaporation tower 2 and the cooling tower 3.

[0118] Please refer to Figure 1 again, the heat exchange unit 7 is further included;

[0119] The heat exchange unit 7 includes:

[0120] a first heat exchanger 701, which is in communication with the evaporation tower 2 and is used to provide the heat required for evaporation by the evaporation tower 2; and

[0121] a second heat exchanger 702, which is in communication with the cooling tower 3 and is used to provide the chilled water required for low-temperature condensation by the cooling tower 3.

[0122] Please refer to Figure 1 again, the storage unit 6 includes:

[0123] a first storage tank 601, which is connected with the centrifugal unit 5 and is used to store the product after centrifugation by the centrifugal unit 5;

[0124] a second storage tank 602, which is in communication with the cooling tower 3 and the extraction separator 4, respectively, and the second storage tank 602 is used to provide the extraction agent to the extraction separator 4;

[0125] a third storage tank 603 connected with the evaporation tower 2 and used to receive the product obtained after evaporation of the evaporation tower 2;

[0126] a fourth storage tank 604 connected with the cooling tower 3 and used to receive the product obtained after low-temperature condensation of the cooling tower 3; and

[0127] a fifth storage tank 605, one end of which is communicated with the extraction separator 4 and the other end of which is communicated with the evaporation tower 2, and the supernatant extracted by the extraction separator 4 is input into the evaporation tower 2.

[0128] Please also refer to Figure 1 As shown in the figure, the centrifugal unit 5 includes:

[0129] a cyclone 501 communicated with the extraction separator 4 and used for solid-liquid separation; and

[0130] a centrifuge 502 used in conjunction with the cyclone 501 for centrifugal separation.

[0131] Example 2

[0132] The embodiment provides a treatment process of salt-containing and mixed-acid wastewater, which is executed by using the treatment system of salt-containing and mixed-acid wastewater in Example 1, the wastewater containing phosphoric acid, hydrochloric acid and DMF, and the treatment process includes the following steps:

[0133] S1: primary evaporation: the wastewater is input into the evaporation tower 2 for primary evaporation, and the steam obtained by the primary evaporation is input into the cooling tower 3 for low-temperature condensation to obtain hydrochloric acid, and the hydrochloric acid is input into the fourth storage tank 604 for storage, and the remaining in the evaporation tower 2 is a primary concentrated solution;

[0134] S2: extraction: the primary concentrated solution in S1 is input into the extraction separator 4 for extraction separation, and a first extraction supernatant is input into the fifth storage tank 605, and an extraction solid-phase mixture is obtained;

[0135] S3: secondary evaporation: the first extraction supernatant in the fifth storage tank 605 in S2 is input into the evaporation tower 2 for secondary evaporation, and the steam obtained by the secondary evaporation is input into the cooling tower 3 for low-temperature condensation to obtain a first product, and the remaining in the evaporation tower 2 is DMF, and the DMF is input into the third storage tank 603 for storage;

[0136] S4: centrifugation: the extraction solid-phase mixture in S2 is input into the cyclone 501 and the centrifuge 502 to obtain phosphoric acid, and the phosphoric acid is input into the first storage tank 601 for storage.

[0137] In S1, the temperature of the primary evaporation is 85°C.

[0138] In S2, carbon disulfide is added into the extraction separator 4 from the second storage tank 602 during the extraction.

[0139] In S3, the first product is carbon disulfide, and the first product is introduced into the second storage tank 602.

[0140] In S3, the temperature of the secondary evaporation is 40°C.

[0141] In S1 and S3, the temperature of the low-temperature condensation is -10°C.

[0142] Example 3

[0143] This example takes a certain chemical enterprise as an example, wherein: the hydrochloric acid content is 9.7%, the phosphoric acid content is 8.68%, the DMF content is 15.82%, and the impurity salt content is 2.5% (mainly sodium chloride).

[0144] The waste liquid amount is 55 t / d per day, and the evaporation equipment is used to separate water and hydrochloric acid mist under positive pressure conditions, with a concentration ratio of 3-4 times, to obtain about 38-40 t / d, about 15% of dilute hydrochloric acid, and the remaining 15 t / d of phosphoric acid, DMF and impurity salt solution.

[0145] The hourly liquid input is 2.5 tons, the evaporation temperature is 85°C, the air volume is about 5000 m 3 / h, the system pressure is 2.3 KPa, and the evaporation circulation amount is 40 m 3 / h, wherein the heat source is saturated steam 0.4 MPa.

[0146] DMF is extracted using extractant CS2, the extraction amount of CS2 is controlled to be 7 times the equivalent of DMF, the stirring rate is controlled in the extraction separation tower, and after standing and separation, the bottom is a phosphoric acid impurity salt solution, the upper layer is an extractant and DMF mixed solution, the upper layer solution enters the evaporation system, and the solvent is evaporated at low temperature and collected for repeated use. The phosphoric acid impurity salt solution is centrifuged to remove salt and recovered as crude industrial phosphoric acid.

[0147] About 8 t of DMF and about 5 t of crude phosphoric acid are produced, and the low value of hydrochloric acid is offset by the disposal cost of impurity salt.

[0148] Example 4

[0149] A surface treatment enterprise, for a sealing agent, a surface chemical plating enterprise, heavy metal wastewater containing acetic acid is evaporated and crystallized. The acetic acid and water in the evaporation system are evaporated to become dilute acetic acid by evaporation, new acetic acid is added for continuous circulation, and the remaining sodium acetate and nickel acetate salt is removed by freezing crystallization and then disposed.

[0150] The project scale is 20 t / d, the air volume is 1500 m 3 / h, the system pressure is 1.5 KPa, and the evaporation condensation circulation amount is 12 m 3 / h, evaporation temperature 80℃, about 2 tons of sodium acetate hydrate and nickel acetate hydrate are produced per day. The energy consumption of the equipment is 0.4 tons of steam per hour. The project realizes the recycling of acetic acid and zero discharge of heavy metal wastewater.

[0151] Example 5

[0152] A medical chemical enterprise wastewater treatment project, the process wastewater produced in the workshop is organic wastewater and high-salt wastewater, a total of 40 tons per day. The organic matter mainly contains a large amount of methanol, acetone, toluene, hexamethyl disilane, guaiacol, a-chloroglycerol, ethylene glycol dimethyl ether, isooctane, chloroform, etc. The salts mainly include sodium bisulfate, sodium sulfate, sodium chloride, sodium hydroxide, sodium sulfite, potassium chloride, and sodium acetate, etc.

[0153] Because the water contains a large amount of solvent and high-boiling substances, it is planned to recover the solvent, then perform rectification, and avoid the pollution and blockage of the heat exchanger of the rectification tower caused by a large amount of high-boiling substances. The diameter of the bottom of the evaporation tower is increased, low-temperature evaporation is used, the initial evaporation temperature is controlled at 60℃, and the solvents methanol, acetone, and toluene are recovered. Then the temperature is increased to 85℃, and the produced water is recovered; the recovery is performed in stages. The effect is remarkable. The data table during performance test and acceptance is as follows:

[0154]

[0155] In this case, the evaporation tower is used for crude recovery of the solvent, especially for low-boiling solvents, two storage tanks are set, the front-stage solvent recovery is stored in the storage tank, and the rear-stage wastewater containing a small amount of solvent is collected and sent to the biochemical treatment for wastewater treatment, the treatment difficulty is greatly reduced. The remaining high-boiling substances and salts are discharged from the system in the form of viscous concentrated liquid, and disposed as hazardous waste.

[0156] The above description of the embodiments is for the purpose of facilitating the understanding and use of the invention by those skilled in the art. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without having to go through creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A process for treating a salt-containing, mixed-acid waste water, characterized by, A treatment system for a salt-containing and mixed-acid-containing wastewater containing phosphoric acid, hydrochloric acid and DMF is executed, the system comprising: a wastewater storage tank (1); an evaporation tower (2) in communication with the wastewater storage tank (1) and evaporating the wastewater; a cooling tower (3) in communication with the upper outlet of the evaporation tower (2) and low-temperature condensing the steam from the upper outlet of the evaporation tower (2); an extraction separator (4) in communication with the lower outlet of the evaporation tower (2) and extracting the concentrated liquid obtained by evaporation from the lower outlet of the evaporation tower (2); a centrifugal unit (5) in communication with the extraction separator (4) and separating the solid-liquid mixture after extraction in the extraction separator (4); and a storage unit (6) having a plurality of storage tanks and being in communication with the evaporation tower (2), the cooling tower (3), the extraction separator (4) and the centrifugal unit (5), respectively; the treatment process comprising the following steps: S1: primary evaporation: passing the wastewater into the evaporation tower (2) for primary evaporation, and passing the steam obtained by primary evaporation into the cooling tower (3) for low-temperature condensation to obtain hydrochloric acid, and passing the hydrochloric acid into the fourth storage tank (604) for storage, and the remaining substance in the evaporation tower (2) being a primary concentrated liquid; S2: extraction: passing the primary concentrated liquid in S1 into the extraction separator (4) for extraction and separation to obtain a primary extraction supernatant and an extraction solid-phase mixture, and passing the primary extraction supernatant into the fifth storage tank (605); S3: secondary evaporation: passing the primary extraction supernatant in the fifth storage tank (605) in S2 into the evaporation tower (2) for secondary evaporation, wherein the steam obtained by secondary evaporation is passed into the cooling tower (3) for low-temperature condensation to obtain a first product, and the remaining substance in the evaporation tower (2) being DMF, and passing the DMF into the third storage tank (603) for storage; S4: centrifugation: passing the extraction solid-phase mixture in S2 through a cyclone (501) and a centrifuge (502) in sequence to obtain phosphoric acid, and passing the phosphoric acid into the first storage tank (601) for storage.

2. The process for treating salt-containing mixed acid waste water according to claim 1, characterized by, a gas supply unit (8) is further included; the gas supply unit (8) comprising: a blower (801) in communication with the evaporation tower (2); a nitrogen source (802) in communication with the evaporation tower (2) and used to provide evaporation power; and a nitrogen circulation pipeline (803) having two ends respectively in communication with the evaporation tower (2) and the cooling tower (3) to circulate nitrogen in the evaporation tower (2) and the cooling tower (3).

3. The process for treating salt-containing mixed acid waste water according to claim 1, characterized by, a heat exchange unit (7) is further included; the heat exchange unit (7) comprising: a first heat exchanger (701) in communication with the evaporation tower (2) and used to provide heat required for evaporation in the evaporation tower (2); and a second heat exchanger (702) in communication with the cooling tower (3) and used to provide chilled water required for low-temperature condensation in the cooling tower (3).

4. The process for treating salt and mixed acid waste water as claimed in claim 1 wherein, the storage unit (6) comprising: a first storage tank (601) connected with the centrifugal unit (5) and used to store the product after centrifugation in the centrifugal unit (5); a second storage tank (602) in communication with the cooling tower (3) and the extraction separator (4) respectively, the second storage tank (602) being used to provide the extraction agent to the extraction separator (4); a third storage tank (603) connected with the evaporation tower (2) and used to receive the product obtained after evaporation of the evaporation tower (2); a fourth storage tank (604) connected with the cooling tower (3) and used to receive the product obtained after low-temperature condensation of the cooling tower (3); and a fifth storage tank (605) in communication with the extraction separator (4) at one end and in communication with the evaporation tower (2) at the other end, and used to input the supernatant extracted by the extraction separator (4) into the evaporation tower (2).

5. The process for treating salt and mixed acid waste water as claimed in claim 1 wherein, The centrifugal unit (5) comprises: a cyclone (501) in communication with the extraction separator (4) and used for solid-liquid separation; and a centrifuge (502) in communication with the cyclone (501) and used for centrifugal separation.

6. The process for treating salt and mixed acid waste water as claimed in claim 1 wherein, In S1, the temperature of the primary evaporation is 20-95°C.

7. The process for treating salt and mixed acid waste water as claimed in claim 4 wherein, In S2, carbon disulfide is added to the extraction separator (4) from the second storage tank (602) during extraction; In S3, the first product is carbon disulfide, and the first product is input into the second storage tank (602).

8. The process for treating salt and mixed acid waste water as claimed in claim 1 wherein, In S3, the temperature of the secondary evaporation is 10-40°C.

9. The process for treating salt and mixed acid waste water as claimed in claim 1 wherein, In S1 and S3, the temperature of the low-temperature condensation is -15-0°C.

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