阅读说明：本技术 一种用亚临界氧化技术深度处理废水的方法 (Method for advanced treatment of wastewater by subcritical oxidation technology ) 是由 陈静波 孙伟杰 于 2019-11-11 设计创作，主要内容包括：本发明涉及一种用亚临界氧化技术深度处理废水的方法,取催化剂装入反应器,将工业废水加压并预热,与氧气混合进入反应器发生亚临界水氧化反应,所述催化剂为以分子筛为载体的新型固定床催化剂,负载有Ce、Pt、Zn。本发明能够确保在较低的温度和压力下进行,降低能耗,减轻设备的压力。(The invention relates to a method for advanced treatment of wastewater by a subcritical oxidation technology, which comprises the steps of loading a catalyst into a reactor, pressurizing and preheating industrial wastewater, mixing the industrial wastewater with oxygen, and introducing the mixture into the reactor to perform subcritical water oxidation reaction, wherein the catalyst is a novel fixed bed catalyst taking a molecular sieve as a carrier and loaded with Ce, Pt and Zn. The invention can be carried out at lower temperature and pressure, reduces energy consumption and lightens the pressure of equipment.)

1. A method for treating wastewater using subcritical oxidation technology, said method comprising the steps of: a certain amount of catalyst is loaded into a reactor, industrial wastewater is pressurized and preheated, and is mixed with oxygen to enter the reactor to generate a subcritical water oxidation reaction, the pressure in the reactor is strictly controlled to be 2-10 MPa, the temperature is controlled to be 120-180 ℃, and the catalyst is a fixed bed catalyst taking a molecular sieve as a carrier.

2. A method of treating wastewater according to claim 1, wherein: the reaction temperature is preferably 140 ℃ to 160 ℃, and the reaction pressure is preferably 2-5 MPa.

3. A method of treating wastewater according to claim 1, wherein: the catalyst takes a molecular sieve as a carrier, and Ce, Pt and Zn are loaded on the molecular sieve.

4. A method of treating wastewater according to claim 1, wherein: the preparation of the catalyst comprises the following steps: (1) preparation of a catalyst precursor: dissolving cerium nitrate, chloroplatinic acid and zinc chloride in deionized water to prepare a solution, adding a molecular sieve into the solution, soaking, filtering and drying to obtain a catalyst precursor;

(2) preparation of the catalyst: and roasting the catalyst precursor in a muffle furnace, cooling to room temperature, and taking out to obtain the catalyst.

5. A method of treating wastewater according to claim 4 and characterized in that: the roasting temperature of the catalyst precursor in a muffle furnace is 400-600 ℃, and the time is 2-10 hours.

6. A method of treating wastewater according to claim 4 and characterized in that: the preparation method also comprises a pretreatment step of the molecular sieve before the preparation of the catalyst precursor.

7. A method of treating wastewater according to claim 6 and further comprising: the pretreatment steps are as follows: uniformly mixing the molecular sieve with a hydrofluoric acid solution, treating for 10-24 hours at the temperature of 100-150 ℃, filtering, adding polyethylene glycol for modification treatment, filtering and drying to obtain the treated molecular sieve.

8. A method of treating wastewater according to claim 7 and further comprising: the molecular weight of the polyethylene glycol is 5000-.

9. A method of treating wastewater, comprising: a method of treating wastewater by a subcritical oxidation technique according to any one of claims 1 to 8, wherein the wastewater is subjected to a first stage treatment and then to a second stage treatment, wherein the second stage treatment is a supercritical water oxidation reaction in a second reactor.

10. A method of treating wastewater according to claim 9 and further comprising: the industrial wastewater treated in the first stage is pressurized by a high-pressure pump, is input into a heat exchanger for preheating, is mixed with oxygen and then enters a second reactor for supercritical water oxidation reaction, the reaction temperature is controlled to be 400-450 ℃, the reaction pressure is controlled to be 25-30 MPa, the wastewater after the reaction is cooled by a cooler, is reduced to 0MPa by a pressure reducing valve and then enters a gas-liquid separator, and liquid-phase water and gas-phase products are discharged from the bottom and the top of the separator respectively.

Technical Field

The invention belongs to the technical field of industrial wastewater treatment, and particularly relates to a method for treating high-concentration degradation-resistant industrial organic wastewater by using a specific catalyst to perform a subcritical water oxidation method.

Background

In recent years, with the gradual attention of governments on environmental management, the national increase of infrastructure and environmental investment, the development of various supporting policies, the increase of social requirements, and the rapid development of industrial wastewater treatment industry in China. The industrial wastewater discharge is large, the pollution range is wide, and the pollutants have the characteristics of multiple types, strong toxicity and the like, so the treatment process is complex. The biodegradability of the industrial wastewater difficult to degrade is low, the BOD5/COD value is generally below 0.3 or even lower, and high salt, high ammonia nitrogen and high organic matters are often remarkable characteristics and are a difficult problem in the wastewater treatment world at home and abroad at present. Some pollutants contained in the wastewater belong to artificially synthesized substances, such as polycyclic aromatic hydrocarbons, heterocycles and long-chain alkanes or heterocyclic compounds containing nitrogen, oxygen, sulfur and phosphorus at the same time, and the like, and have the advantages of higher stability, even high toxicity, large difficulty in treatment and high investment cost.

Supercritical water oxidation technology (SCWO) is an emerging organic wastewater treatment technology. Supercritical water is dense fluid with temperature and pressure higher than its critical point (working pressure greater than 22.1Mpa, working temperature higher than 374.3 ℃), and has some special properties compared with standard state water, and hydrogen bonds in water hardly exist. Therefore, supercritical water has a very low dielectric constant and good diffusion and transfer properties, thereby having good solvation characteristics. Supercritical water oxidation technology treats organic compounds and toxic wastes, and completely oxidizes organic matters into clean water, carbon dioxide, nitrogen, inorganic salt and other substances.

CN104211234B discloses a method for treating industrial wastewater by the cooperation of supercritical water oxidation and membrane separation, which comprises the steps of directly feeding wastewater into a supercritical water oxidation device through a grid for treatment, and then removing organic matters, various ions, molecules and other substances in the wastewater by a technology combined with membrane separation, thereby finally achieving the standard of drinking water. CN106495385A discloses a supercritical oxidation method for treating wastewater, which comprises the steps of firstly heating the wastewater into saturated steam through a start heat exchanger and a working heat exchanger, enabling the saturated steam to enter an overpressure near-critical reactor for flash evaporation to form superheated steam, and discharging salt separated from the wastewater from the bottom of the overpressure near-critical reactor; then the superheated steam reacts with an oxidant in a supercritical oxidation reactor, the reaction pressure is 25MPa to 30MPa, and the temperature is 400 ℃ to 600 ℃; the method solves the problem of pipeline blockage through overpressure near-critical desalination.

Supercritical water oxidation, while having many advantages, is high in temperature, pressure, equipment requirements, and operating costs because of the large amount of energy required to change the wastewater from ambient conditions to a supercritical state, which is necessary to ensure complete destruction of organic pollutants. Moreover, nitrogen-containing organic matters such as protein and the like are polymerized in the high-concentration organic wastewater, an intermediate product NH3-N generated by the nitrogen-containing organic matters in the supercritical water oxidation treatment process is difficult to degrade, and when a catalyst is not used, the removal rate of ammonia nitrogen is only about 10% when the temperature is over 600 ℃ and the pressure is over 20MPa in a tubular reactor. In addition, if industrial waste water contains more chloride, a large amount of acidic substances are generated in the high-temperature high-pressure oxidation reaction process of supercritical water oxidation, so that the corrosion rate is high, equipment devices made of metal materials are seriously corroded, equipment is damaged, and even explosion is caused. During research, the research shows that the research on the catalyst is very little for supercritical water oxidation.

One solution is to use a subcritical water oxidation method to treat industrial wastewater. CN109071287A discloses a method and system for subcritical oxidation of organic contaminants in water, which states that it is economically achieved using a peroxide oxidizing agent (such as hydrogen peroxide), an integrated combination of thermal and mechanical energy, and subcritical conditions that allow the use of less expensive materials of manufacture than required by SCWO methods. Passing a waste stream having an initial temperature and an initial pressure through a pressure exchanger and a heat exchanger to obtain a heated pressurized stream, and thereafter feeding the heated pressurized stream to a reaction vessel while feeding at least one oxidant, without the heated pressurized stream yet containing an oxidant, and oxidizing said at least one organic contaminant; then withdrawing a first treated stream from the reaction kettle, wherein the treated stream has a lower concentration of at least one organic contaminant than the waste stream; and passing the first treated stream having a post-oxidation temperature and a post-oxidation pressure through the heat exchanger and pressure exchanger to obtain a second treated stream having a temperature lower than the post-oxidation temperature of the first treated stream due to heat exchange between the waste stream and the first treated stream, and a pressure lower than the post-oxidation pressure of the first treated stream due to pressure exchange between the waste stream and the first treated stream. Many details of the above process are unclear, are not easily accomplished, and no critical catalyst is mentioned. CN103723895A discloses a method for treating industrial wastewater by combining a subcritical water oxidation method with a biochemical method, which can greatly reduce the degree of acid corrosion, efficiently remove toxic organic matters in wastewater, eliminate toxicity, retain certain biochemical activity and realize that the wastewater completely reaches the standard by combining with subsequent biochemical treatment by reducing the reaction temperature and pressure to a specific range.

Disclosure of Invention

The invention aims to provide a method for advanced treatment of industrial wastewater by Sub-critical Air Oxidation (Sub-critical oxygen Oxidation). The method can be carried out at lower temperature and pressure, so that the energy consumption is reduced, and the pressure of equipment is reduced. And based on the developed brand new catalyst, on one hand, the catalyst can better remove ammonia nitrogen, carboxylic acid, chloride and the like, and on the other hand, the catalyst has good adaptability to various industrial wastewater and is stable.

The industrial wastewater treatment method comprises the following steps: a certain amount of catalyst is loaded into a reactor, industrial wastewater is pressurized and preheated, and is mixed with oxygen to enter the reactor to generate subcritical water oxidation reaction, the pressure and the temperature in the reactor are strictly controlled, and the catalyst is a fixed bed catalyst taking a molecular sieve as a carrier.

Furthermore, the catalyst takes a molecular sieve as a carrier, and Ce, Pt and Zn are loaded on the molecular sieve. The preparation of the catalyst comprises the following steps: (1) preparation of a catalyst precursor: dissolving cerium nitrate, chloroplatinic acid and zinc chloride in deionized water to prepare a solution, adding a molecular sieve into the solution, soaking, filtering and drying to obtain a catalyst precursor; (2) preparation of the catalyst: and roasting the catalyst precursor in a muffle furnace, cooling to room temperature, and taking out to obtain the catalyst.

Preferably, a pretreatment step for the molecular sieve is also included before the preparation of the catalyst precursor. The pretreatment steps are as follows: uniformly mixing the molecular sieve with a hydrofluoric acid solution, treating for 10-24 hours at the temperature of 100-150 ℃, filtering, adding polyethylene glycol for modification treatment, filtering and drying to obtain the treated molecular sieve.

The more detailed procedure is as follows: 100-300g of the catalyst was taken and charged into a reactor (fixed bed reactor). Pressurizing and preheating industrial wastewater, mixing the industrial wastewater with oxygen, introducing the mixture into a reactor to perform a subcritical water oxidation reaction, and strictly controlling the pressure of the reactor to be 2-10 MPa and the temperature to be 120-180 ℃. The volume ratio of the oxygen to the industrial wastewater is 100-400, and the mass space velocity of the industrial wastewater is 0.5h^-1～1h^-1。

Among them, the reaction temperature is more preferably 140-. The reaction pressure is preferably 2 to 5 MPa.

The specific preparation method of the catalyst comprises the following steps:

(1) pretreatment: uniformly mixing a ZSM-5 molecular sieve with 0.1-0.5% (by weight) hydrofluoric acid solution, treating for 10-24 hours at the temperature of 100-;

(2) preparation of a catalyst precursor: weighing 100-200g of cerium nitrate, 50-100g of chloroplatinic acid and 50-100g of zinc chloride, dissolving in 1L of deionized water to prepare a solution, adding 1Kg of ZSM-5 molecular sieve treated in the step (1) into the solution, soaking for 1-5 hours, filtering and drying to obtain a catalyst precursor;

(3) preparation of the catalyst: and roasting the catalyst precursor in a muffle furnace at 400-600 ℃ for 2-10 hours, and taking out the catalyst precursor after the temperature is reduced to room temperature to obtain the catalyst.

The subcritical oxidation technology of the invention is applicable to industrial wastewater influent COD which can be more than 15000ppm and less than 100000 ppm. The industrial wastewater can be wastewater containing high Chemical Oxygen Demand (COD) in industries such as coking, dye, pesticide, printing and dyeing, petrifaction, leather, medicine and the like or substances which cannot be degraded by biochemical technology (such as ammonia nitrogen, polycyclic aromatic hydrocarbon, carcinogenic substance BAP and the like).

Another aspect of the invention is also: the method can also comprise a second stage except for the subcritical oxidation treatment stage of the first stage, realizes supercritical oxidation by using the experience of the subcritical oxidation technology, exerts the characteristics that the density of the supercritical technology is close to liquid and the diffusion coefficient is close to gas, realizes more efficient chemical reaction, can efficiently degrade organic matters and simultaneously crystallize out salt in water, omits a subsequent evaporation device, and reduces investment and operating cost.

The method comprises the following steps of pressurizing industrial wastewater treated in the first stage by a high-pressure pump, inputting the industrial wastewater into a heat exchanger for preheating, mixing the industrial wastewater with oxygen, then entering a second reactor for supercritical water oxidation reaction, controlling the reaction temperature to be 400-450 ℃ and the reaction pressure to be 25-30 MPa, cooling the wastewater after the reaction by a cooler, reducing the pressure to be 0MPa by a pressure reducing valve, then entering a gas-liquid separator, and discharging liquid-phase water and gas-phase products from the bottom and the top of the separator respectively.

Compared with the prior art, the invention has the beneficial effects that:

1. the subcritical oxidation technology is used for carrying out advanced treatment on the industrial wastewater, and the method can be carried out at lower temperature and pressure, so that the energy consumption is reduced, and the pressure of equipment is relieved. The catalyst loaded with Ce, Pt and Zn can catalyze the reaction at a lower temperature, and the temperature generally used conventionally is basically preferably over 200 ℃, which is quite disadvantageous in terms of energy consumption.

2. In order to achieve the purpose of reducing the reaction temperature, it is desirable to use a catalyst having high stability, and particularly, a catalyst loaded with Ce, Pt, Zn, which abandons the commonly used copper, but although a copper-based catalyst has a good catalytic effect because oxygen on the surface of copper oxide is easily lost, copper ions are easily lost in wastewater, and the stability is not good. When the catalyst is prepared, the molecular sieve is particularly treated by hydrofluoric acid, so that impurities in the pore channel of the molecular sieve can be removed, the molecular sieve is activated, the pore channel structure can be maintained after the subsequent treatment by PEG, and the pore diameter can be further adjusted during the subsequent treatment by a muffle furnace.

3. The Ce, Pt and Zn loaded catalysts can cooperate with each other, the performances reach a certain balance, and the catalyst has good catalytic effects on various industrial wastewater such as coking, dyes, pesticides, printing and dyeing, petrifaction, leather, medicines and the like.

4. In the case of high wastewater treatment requirements or ultra-high COD wastewater, the subcritical oxidation technique of the present invention may be used as a first stage of treatment, and a second stage may be included later, and supercritical oxidation may be achieved by experience of the subcritical oxidation technique.

Detailed Description

The present invention will be described in further detail with reference to specific examples. It is to be understood that these embodiments are provided to illustrate the general principles, major features and advantages of the present invention, and the present invention is not limited in scope by the following embodiments. The implementation conditions used in the examples can be further adjusted according to specific requirements, and the implementation conditions not indicated are generally the conditions in routine experiments.