TREATMENT SYSTEM FOR PMIDA HIGH-SALINITY WASTEWATER AND TREATMENT METHOD THEREOF

Abstract

The invention provides a treatment system and a treatment method for PMIDA high-salinity wastewater. The treatment system includes a booster pump, a water inlet-outlet heat exchanger, a water inlet heater and an oxidation reactor, and the water inlet-outlet heat exchanger is provided with a wastewater inlet, a wastewater outlet, an oxidized water inlet, and an oxidized water outlet. An oxidized water from the oxidation reactor enters the water inlet-outlet heat exchanger through the oxidized water inlet, the oxidized water outlet is connected to an intermediate tank, the wastewater inlet is connected to the booster pump, and the wastewater outlet is connected to a wastewater heater. A micro-interface unit is disposed at the lower part in the oxidation reactor, for dispersing crushed gas into bubbles. A gas inlet is formed at a side wall of the oxidation reactor and is connected to the micro-interface unit through a pipeline.

Claims

1. A treatment system for N-(phosphonomethyl) iminodiacetic acid (PMIDA) high-salinity wastewater, comprising: a booster pump, an water inlet-outlet heat exchanger, an water inlet heater, and an oxidation reactor which are connected in sequence, the water inlet-outlet heat exchanger being provided with a wastewater inlet, a wastewater outlet, an oxidized water inlet, and an oxidized water outlet; wherein an oxidized water from the oxidation reactor enters the water inlet-outlet heat exchanger through the oxidized water inlet, the oxidized water outlet is connected to an intermediate tank, the wastewater inlet is connected to the booster pump, and the wastewater outlet is connected to the wastewater heater; and wherein a micro-interface unit is disposed at a lower portion inside the oxidation reactor, the micro-interface unit is configured to disperse broken gas into gas bubbles, a gas inlet is disposed at a side wall of the oxidation reactor, and the gas inlet is connected to the micro-interface unit through a pipeline; wherein the micro-interface unit comprises a first micro-interface generator arranged in an upper position and a second micro-interface generator arranged in a lower position, the first micro-interface generator introduces a wastewater recycled from the oxidation reactor, the first micro-interface generator is connected to a gas guide pipe, a top end of the gas guide pipe extends out of a liquid surface of the oxidation reactor for recovering air or oxygen, and an end of the gas inlet extends into the second micro-interface generator.

2. (canceled)

3. The treatment system for PMIDA high-salinity wastewater according to claim 1, wherein a connecting rod for mutually fixing the first micro-interface generator and the second micro-interface generator to each other is disposed between the first micro-interface generator and the second micro-interface generator.

4. The treatment system for PMIDA high-salinity wastewater according to claim 1, wherein the first micro-interface generator is a hydraulic micro-interface generator.

5. The treatment system for PMIDA high-salinity wastewater according to claim 1, wherein the second micro-interface generator is a pneumatic micro-interface generator.

6. The treatment system for PMIDA high-salinity wastewater according to any one of claim 1, wherein an oxidation outlet is disposed at a top portion of the oxidation reactor, and the oxidation outlet is connected to the oxidized water inlet through a second pipeline.

7. The treatment system for PMIDA high-salinity wastewater according to any one of claim 1, wherein the oxidized water from the oxidation water outlet enters a vapor-liquid separation tank for vapor-liquid separation.

8. The treatment system for PMIDA high-salinity wastewater according to claim 7, wherein the treatment system further comprises the intermediate tank, and the intermediate tank is connected to the vapor-liquid separation tank and is configured to collect the wastewater after oxidation treatment for performing a sequent salt removal treatment.

9. A treatment method using a treatment system for PMIDA high-salinity wastewater, the treatment system comprising a booster pump, an water inlet-outlet heat exchanger, an water inlet heater, and an oxidation reactor which are connected in sequence, the water inlet-outlet heat exchanger being provided with a wastewater inlet, a wastewater outlet, an oxidized water inlet, and an oxidized water outlet wherein an oxidized water from the oxidation reactor enters the water inlet-outlet heat exchanger through the oxidized water inlet, the oxidized water outlet is connected to an intermediate tank, the wastewater inlet is connected to the booster pump, and the wastewater outlet is connected to the wastewater heater; and wherein a micro-interface unit is disposed at a lower portion inside the oxidation reactor, the micro-interface unit is configured to disperse broken gas into gas bubbles, a gas inlet is disposed at a side wall of the oxidation reactor, and the gas inlet is connected to the micro-interface unit through a pipeline; wherein the micro-interface unit comprises a first micro-interface generator arranged in an upper position and a second micro-interface generator arranged in a lower position, the first micro-interface generator introduces a wastewater recycled from the oxidation reactor, the first micro-interface generator is connected to a gas guide pipe, a top end of the gas guide pipe extends out of a liquid surface of the oxidation reactor for recovering air or oxygen, and an end of the gas inlet extends into the second micro-interface generator, the method comprising the following steps: the PMIDA high-salinity wastewater entering an oxidation reactor after being heated, and introducing a compressed air or a compressed oxygen into the oxidation reactor to perform an oxidation reaction; and dispersing and breaking the compressed air or the compressed oxygen which enters the oxidation reactor by the micro-interface unit.

10. The treatment method using the treatment system for PMIDA high-salinity wastewater according to claim 9, wherein a temperature of the oxidation reaction is 180-185° C., and a reaction pressure of the oxidation reaction is 4-4.5 MPa.

11. The treatment method using the treatment system for PMIDA high-salinity wastewater according to claim 10, wherein the temperature is 182° C., and the reaction pressure is 4.2 MPa.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0052] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only used for the purpose of illustrating the preferred embodiments, and are not considered as a limitation to the invention. Also, throughout the drawings, the same reference numerals are used to denote the same components. In the drawings:

[0053] FIG. 1 is a structural diagram of a treatment system for PMIDA high-salinity wastewater according to an embodiment of the present invention.

DETAIL DESCRIPTION

[0054] In order to make the purpose and advantages of the invention clearer, the invention will be further described below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the invention, and are not used to limit the invention.

[0055] It should be understood that in the description of the invention, orientations or position relationships indicated by terms upper, lower, front, back, left, right, inside, outside and the like are orientations or position relationships are based on the direction or position relationship shown in the drawings, which is only for ease of description, rather than indicating or implying that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the invention.

[0056] Further, it should also be noted that in the description of the invention, terms “mounting”, “connected” and “connection” should be understood broadly, for example, may be fixed connection and also may be detachable connection or integral connection; may be mechanical connection and also may be electrical connection; and may be direct connection, also may be indirection connection through an intermediary, and also may be communication of interiors of two components. Those skilled in the art may understand the specific meaning of terms in the invention according to specific circumstance.

[0057] In order to explain the technical solutions of the present invention more clearly, specific embodiments are used for description below.

Embodiments

[0058] Referring to FIG. 1, a treatment system for PMIDA high-salinity wastewater according to an embodiment of the present invention, including a booster pump 10, a water inlet-outlet heat exchanger 20, a water inlet heater 30, and an oxidation reactor 70 which are connected in sequence.

[0059] A wastewater inlet 21, a wastewater outlet 22, an oxidation water inlet 23 and an oxidation water outlet 24 are disposed on the inlet-outlet heat exchanger 20. The oxidized water from the oxidation reactor enters the water inlet-outlet heat exchanger 20 by means of the oxidation water inlet 23. The oxidation water outlet 24 is connected to an intermediate tank 100, the wastewater inlet 21 is connected to the booster pump 10, and the wastewater outlet 22 is connected to a water inlet heater 30. In the water inlet-outlet heat exchanger 20, the oxidized water after the reaction of the oxidation reactor 70 exchanges heat with the PMIDA high-salinity wastewater to be treated, achieving the effect of fully utilizing the energy resource.

[0060] An oxidation outlet 71 is disposed at an upper portion of the oxidation reactor 70. The oxidized water from the oxidation outlet 71 enters the inlet-outlet heat exchanger 20 by means of the oxidation water inlet 23. A micro-interface unit 80 for dispersing broken gas into gas bubbles is disposed at the lower portion of the oxidation reactor 70. A gas inlet 72 is disposed on the side wall of the oxidation reactor 70, and the air inlet 72 is connected to the micro-interface unit 80 through a pipeline. An air compressor 40 is in communication with the air inlet 72, the air compressor 40 may be a centrifugal air compressor, and this type of compressors are inexpensive and convenient to use. Air or oxygen compressed by the air compressor 40 is first heated by the air heater 50, then enters the oxidation reactor 70, and enters the micro-interface unit 80 through the air inlet 72.

[0061] The micro-interface unit 80 includes a first micro-interface generator 81 arranged in a lower position and a second micro-interface generator 82 arranged in a lower position. The first micro-interface generator 81 introduces wastewater recycled from the oxidation reactor 70. The wastewater is preferably recycled by a circulation pump 90. The first micro-interface generator 81 is connected to a gas guide pipe 84. A top end of the gas guide pipe 84 extends out of a liquid surface of the oxidation reactor 70 for recovering air or oxygen, and the first micro-interface generator 81 is a liquid micro-interface generator, thereby realizing the entrainment of air or oxygen above the liquid surface in the oxidation reactor 70. The second micro-interface generator 82 is a pneumatic micro-interface generator, the end of the gas inlet disposed at the side wall of the oxidation reactor 70 extends into the second micro-interface generator 82. Air introduced from the air inlet 72 contacts wastewater in the second micro-interface generator 82 to increase the contact area of the gas-liquid phase, and breaks gas bubbles into micro gas bubbles to improve the mass transfer effect.

[0062] A connecting rod 83 for mutually fixing the first micro-interface generator 81 and the second micro-interface generator 82 to each other is disposed between the first micro-interface generator 81 and the second micro-interface generator 82. There are three connecting rods 83 provided symmetrically between the first micro-interface generator 81 and the second micro-interface generator 82.

[0063] In addition, the oxidized water from the oxidation water outlet 24 contains a part of oxygen. Therefore, gas-liquid separation is first performed in a gas-liquid separation tank 60, the tail gas is recovered from the top of the gas-liquid separation tank 60, the oxidized water is removed from the bottom of the gas-liquid separation tank 60, and is temporarily stored in the intermediate tank 100, and the water from the intermediate tank 100 continues to be subjected subsequent salt removal treatment.

[0064] In the above embodiment, the number of the micro-interface generators is not limited. In order to improve the effects of dispersion and mass transfer, additional micro-interface generators may also be provided. In particular, the installation position of the micro-interface generators is not limited, and the micro-interface generators may be externally provided or internally provided. When the micro-interface generators are internally provided, the micro-interface generators may also be installed on the side wall of a kettle in an opposite manner, so that micro gas bubbles from the outlet of the micro-interface generators are flushed.

[0065] In the above embodiment, the number of the pump bodies is not specifically required, and the pump bodies can be provided at corresponding positions based on actual needs.

[0066] In the following, the operation process and principle of the treatment system for PMIDA high-salinity wastewater of the present invention are briefly described.

[0067] The wastewater is pressurized by the booster pump 10, then passes through the water inlet-outlet heat exchanger 20 and the water inlet heater 30 in sequence for heat exchange, and enters the bottom of the oxidation reactor 70 after being subjected to heat exchange to the required reaction temperature. After being compressed and pressurized by the air compressor 40, air enters an air heater 50 for heating, and then enters the micro-interface unit 80 in the oxidation reactor 70 in two ways. The energy conversion is performed in the micro-interface unit 80 together with the wastewater recycled by the circulation pump 90, and the kinetic energy and pressure energy of the gas and liquid is converted into a bubble surface energy, such that a large number of tens to hundreds of microns of gas bubbles are generated and enter the bottom of the oxidation reactor 70, thereby producing a phase interfacial area in the reactor of greater than 8000 m2/m3 or more, greatly increasing the reaction rate.

[0068] The tail water and tail gas produced by the reaction exchange heat with wastewater by means of the inlet-outlet water heat exchanger 20 for recovering heat, and enter the gas-liquid separation tank 60 to perform gas-liquid separation after cooling. The tail water enters the subsequent treatment section, and the tail gas is discharged after treatment is completed and the standard is reached.

[0069] During the abovementioned process, the reaction temperature in the oxidation reactor 70 is 180-185° C., and the reaction pressure is 4-4.5 MPa. Preferably, the reaction temperature is 182° C., and the reaction pressure is 4.2 MPa.

[0070] The oxidized water after subjected oxidation reaction in the oxidation reactor 70 is returned from the top of the oxidation reactor 70 to the inlet-outlet heat exchanger 20 for heat exchange cooling treatment, and then is transported to the intermediate tank 100 for storage. The water from the intermediate tank 100 continues to be subjected to subsequent salt removal treatment so as to recover reusable products.

[0071] Each of the described process steps is repeated to allow smooth operation of the whole treatment system.

APPLICATION EXAMPLE

[0072] In Sichuan, an enterprise, specializing in the research and development and production of chemicals and pesticides, produce 600 tons of PMIDA mother liquor wastewater produced per day in the pesticide production process, the COD of inlet water is 31340 mg/L, the total salt is 22.7%, and the formaldehyde is 5936 mg/L. Wet air oxidation treatment is used for removing most of COD and formaldehyde, and the product enters a subsequent resource recycling process section.

[0073] According to the treatment effects of the conventional wet air oxidation technology, the relevant design requirements are proposed by the company, as shown in Table 1.

TABLE-US-00001 TABLE 1 Wet air oxidation design requirements of PMIDA mother liquor wastewater 1200 ton/day Name Inlet Water Outlet water Temperature (° C.) 210 220 Pressure (MPa) 8.0 7.9 PH 10 7 Amount of Air (Nm.sup.3/d) 108000 Amount of wastewater (m.sup.3/d) 637 637 COD (mg/L) 31340 6268 Ammonia nitrogen (mg/L) 220 1103 Total phosphorus (mg/L) 7246 7246 Sodium chloride (mg/L) 205273 205273 Formaldehyde (mg/L) 5936 297 Phosphate (mg/L) 21792 35463 Formic acid (mg/L) 11.5 11.5

[0074] By adopting the wastewater treatment system of the embodiment of the present invention, and calibration is performed after the device is stably operated for 72 hours, and the specific treatment results are shown in the following Table 2. It is found by means of tests that the temperature and pressure can be greatly reduced after the micro-interface reaction strengthening technology is used under the condition of reaching the design criteria.

TABLE-US-00002 TABLE 2 Effect comparison for the treatment system of the present invention and conventional wet air oxidization system Process type Technology comparison for the treatment system of the present invention and Conventional wet air Treatment system of the conventional wet air Technical index oxidization system present invention oxidization system Treatment amount (t/d)   637 885 Increase by 39% Reaction temperature (° C.)   210 182 Reduce by 28 Reactant residence time (h)    1 0.72 Reduce by 28% Reaction pressure (MPa)    8 4.2 Reduce by 3.8 Inteifacial area of unit   ~75 3000 Increase by about 39 times reactor Consumption amount of air 0.217 0.140 Reduce by 35% (t/t) Reactor Treatment    1 1.39 Increase by 39% Strength (t/m.sup.3.h) COD removal (%)   80 91 Increase by 13.8% Oxygen utilization rate   55 85 Increase by 30% in air, % Total energy   46 39 Reduce by 15% consumption of ton of product, kWh/t

[0075] By adopting the wastewater treatment system of the present invention, the following technical objects can be achieved:

[0076] (a) on the premise of reaching the designed water outlet indexes, the reaction pressure is reduced to not more than 4 MPa, the reaction temperature is 182° C., and the operation cost is reduced;

[0077] (b) the micro-interface strengthening technology is adopted, improving the oxygen utilization rate, and reducing the energy consumption of the air compressor by more than 10%; and

[0078] (c) the temperature and pressure is reduced, reducing the severity of the device, and improving the intrinsic safety of the device, and providing guidance for reducing design temperature and pressure for later micro-interface strengthening wet air oxidation devices.

[0079] So far, the technical solution of the invention has been described in conjunction with the preferred embodiments shown in the drawings. However, it is easily understood by those skilled in the art that the protection scope of the invention is obviously not limited to these specific embodiments. Without departing from the principle of the invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, which will fall into the protection scope of the invention.

[0080] The above are only preferred embodiments of the invention rather than limits to the invention. Those skilled in the art may make various modifications and changes to the invention. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the invention all should be included in the protection scope of the invention.