Catalytic ozonation treatment process for high-concentration-salt degradation-resistant sewage in coal chemical industry

Abstract

The invention discloses a catalytic ozonation treatment process for high-concentration-salt degradation-resistant sewage in the coal chemical industry. The method comprises the following steps: a) generating ozone-containing gas from oxygen through an ozone generator, entering the bottom of a reactor, dispersing microbubbles through a gas distributor at the bottom of the reactor, contacting with sewage and a catalyst to generate catalytic oxidation reaction, discharging from the top of the reactor, and entering a gas-liquid separator; b) feeding sewage sequentially enters from the top of the reactor and is discharged from the bottom of the reactor through a raw material pump, and forms countercurrent contact with ozone-containing gas in the reactor to complete a catalytic oxidation reaction; a water inlet at the top of each reactor is provided with a liquid distributor, and sewage between the reactors is conveyed by a raw material pump; filter elements are arranged at bottom water outlets of the second reactor and the third reactor; and c) feeding the fresh catalyst from the tops of the second reactor and the third reactor to supplement the fresh catalyst. The device has the characteristics of high ozone utilization rate, high sewage organic matter degradation capability, easiness in replacement of the catalyst, small dosage and good economic performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of sewage treatment and catalysis, and particularly relates to an ozone catalytic oxidation treatment process for coal chemical high-concentration salt refractory sewage. BACKGROUND

[0002] The catalytic oxidation technology is one of commonly used technical means, free radicals generated by the use of oxidants are used to mineralize or decompose toxic substances and refractory organic matter pollutants, reduce the toxicity of sewage, and realize the decomposition of macromolecular substances, and the catalytic oxidation technology has a series of advantages such as strong oxidation capacity, fast reaction speed, convenient use, and no secondary pollution, and thus is paid attention to by people.

[0003] In the prior art, CN 105645559B discloses a device and a treatment process for treating industrial wastewater by using an ozone catalytic oxidation method. A first gas-liquid premixing section, an oxidation reaction section, a second gas-liquid premixing section, and a catalytic oxidation reaction section are sequentially arranged from the water inlet end to the water outlet end of the pipeline reactor; the oxidation reaction section is provided with a subsection filled inert material, and the catalytic oxidation reaction section is provided with a subsection filled ozone catalytic oxidation catalyst; ozone aeration devices are arranged at the inert material, the ozone catalytic oxidation catalyst, and the water inlet end of the first gas-liquid premixing section; and the ozone aeration devices are connected to an ozone generator. The patent uses a pipeline reactor, uses a static mixer and an ultrasonic microwave combined mixing device to fully mix ozone and wastewater, enhances the gas-liquid two-phase mass transfer effect, and improves the catalytic reaction rate.

[0004] CN110563118 A discloses a high-efficiency and stable ozone catalytic oxidation reaction device and a sewage treatment method thereof, which comprises an ozone generator, a reactor, a circulating water pump, and a tail gas destroyer. The inside of the reactor is sequentially provided, from top to bottom, with a fixed bed catalyst layer, a first aeration disc, a first water distribution device, a fluidized bed catalyst layer, a second aeration disc, and a second water distribution device. The top of the reactor is connected to the tail gas destroyer through a tail gas discharge pipe, and the upper part of the reactor is provided with a drainage pipe and a circulating water pipe. The second water distribution device is connected to a water inlet pipe. The circulating water pipe is also connected to the water inlet pipe and is provided with a circulating water pump. The ozone generator is connected to the first aeration disc through a first ozone exhaust pipe and is connected to the second aeration disc through a second ozone exhaust pipe.

[0005] However, the above technology has many deficiencies in industrial applications: first, due to the strong selectivity of ozone and ammonia nitrogen, nitrous acid and organic matter, the difference in reaction rate, and the slow mass transfer rate of ozone, sewage and catalyst in the "three-phase" system, the ozone content in the tail gas is high, the ozone utilization rate is low, and the COD removal efficiency is low, thereby greatly increasing the ozone dosage and operation cost; second, the homogeneous catalysis has the problems of catalyst recovery difficulty and secondary pollution of water body, and the micron-sized solid catalyst of heterogeneous catalyst can easily cause system fluctuation and blockage; third, although the spherical particle catalyst or strip-shaped columnar catalyst is the most commonly used packed catalyst, due to the problems of normal temperature and pressure reaction conditions, uneven catalyst accumulation, low catalyst utilization rate, high energy consumption and low cost; fourth, in the process of catalytic oxidation treatment of high-concentration salt wastewater, the high-concentration salt reaction environment causes catalyst agglomeration, blockage and deactivation, and the catalyst cannot be replaced in time, which causes rapid decay of COD removal efficiency of wastewater and increase of cost. SUMMARY

[0006] In order to overcome the defects of the above prior art, the purpose of the present application is to provide a coal chemical high-concentration salt refractory wastewater ozone catalytic oxidation treatment process, which realizes the coupling innovation of process intensification, reaction process intensification and catalyst surface catalytic intensification, has the characteristics of high ozone utilization rate, strong wastewater organic matter degradation ability, easy catalyst replacement and less catalyst dosage, and good economic performance, especially in the process of treating high-concentration salt wastewater, which is beneficial to long-period and large-scale operation of the device.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0008] A coal chemical high-concentration salt refractory wastewater ozone catalytic oxidation treatment process, comprising the following steps:

[0009] a) oxygen 103 passes through an ozone generator 205 to generate ozone-containing gas, which is divided into three paths and enters the bottom of the first reactor 202, the second reactor 302 and the third reactor 402, and is dispersed into 60-100um micro-bubbles through the gas distributor at the bottom of the reactor, then contacts with the wastewater 102 and the catalyst to generate catalytic oxidation reaction, and is discharged from the top of the reactor and enters the gas-liquid separator 501, the separated gas enters the ozone destroyer 502 and is discharged as tail gas 105, and the separated liquid is mixed with the effluent 106 from the bottom of the third reactor 402 and discharged from the device;

[0010] b) the feed wastewater 102 passes through the raw material pump 201 and enters the top of the three reactors in turn and is discharged from the bottom, and forms countercurrent contact with the ozone-containing gas in the reactor to complete the catalytic oxidation reaction as described in step a); a liquid distributor is arranged at the water inlet of the top of each reactor, and the wastewater 102 flows between the reactors by the raw material pump 102; a filter core is arranged at the water outlet at the bottom of the second reactor 302 and the third reactor 402;

[0011] c) fresh catalyst 101 is supplemented by the top of the second reactor 302, third reactor 402, and the spent catalyst is discharged from the bottom of the reactor.

[0012] Further, the volume ratio of the oxygen 103 and the feed sewage 102 is (3-12):1, the reaction temperature is 10-45℃, the liquid space velocity of the sewage 102 is 0.25-1.5h -1 .

[0013] Further, the volume ratio of the ozone gas in the bottom of the first reactor 202, the second reactor 302, and the third reactor 402 in step a) is (1-3):(0.5-2.5):(1.5-4.0);

[0014] Further, the sewage level in the first reactor 202, the second reactor 302, and the third reactor 402 in step a) is 85-90% of the reactor height, and the gas holdup of the sewage 102 is 5-23%.

[0015] Further, the catalyst in step a) is activated carbon loaded with active metal oxides, and the particle size is 0.5-2.0mm.

[0016] Further, the catalyst in step a) is a core-shell structure catalyst, the inner core is one of silicon carbide, stainless steel slag, zirconia, or silica, the shell layer is a mixture of alumina and active metal oxides, the particle size of the core-shell structure catalyst is 150-800um, the density is 1.75-4.63g / cm 3 , the ratio of the inner core radius to the shell thickness is 2-4:1, and the mass of the active metal oxides accounts for 3-17% of the mass of the shell layer.

[0017] Further, the active metal oxides are one or a combination of iron oxide, copper oxide, zinc oxide, and nickel oxide.

[0018] Further, the volume of the catalyst in the second reactor 302 and the third reactor 402 accounts for 10-35% of the volume of the sewage 102.

[0019] Further, the backwash line is provided at the bottom of the second reactor 302 and the third reactor 402 in step b) to periodically flush the filter core.

[0020] The beneficial effects of the present application are:

[0021] The method of the present application adopts the sewage feeding from the top of the reactor and discharging from the bottom, the ozone-containing gas entering from the bottom of the reactor and discharging from the top, the gas-liquid countercurrent mode, to strengthen the mass transfer efficiency of the gas-liquid two-phase and the gas-liquid-solid three-phase in the reactor, accelerate the dissolution efficiency of ozone and enhance the surface tangential switching frequency of the catalyst;

[0022] The countercurrent reactor adopted by the present application has the sewage COD concentration from high to low and the ozone concentration from low to high from the top to the bottom, so that the ammonia nitrogen inorganic matter and the easily-reacted organic matter are contacted and reacted with the low-concentration ozone, the tail gas ozone concentration is reduced and the ozone utilization rate is improved, the refractory organic matter is reacted with the high-concentration ozone, the treatment efficiency of the refractory organic matter is effectively improved, and the reaction process of ozone and the organic matter is strengthened.

[0023] The present application disperses the ozone-containing gas in the form of micro-bubbles into the sewage in the reactor through the gas distributor, which not only enhances the gas-liquid two-phase interface area and improves the dispersibility of the catalyst in the reaction period, but also controls the water gas holdup rate in the appropriate range based on the sewage properties, prevents the escape of ozone or the excessive residence of the non-ozone bubbles after the reaction, and avoids the problems of insufficient ozone reaction time and reduced sewage residence time.

[0024] The present application adopts the catalyst with appropriate particle size and density, combines the countercurrent reactor and the gas distributor, ensures the high dispersion of the catalyst in the reactor, avoids the problems of catalyst deposition and gas entrainment, and further effectively reduces the active metal oxide by more than 60% compared with the conventional catalyst based on the surface catalytic characteristics of the sewage catalytic oxidation, reduces the catalyst consumption and preparation cost, sets the feeding port and the discharging port of the catalyst, maintains the addition and discharge of the catalyst in the reactor, avoids the problems of hardening, deactivation and replacement of the traditional fixed-bed catalyst in the high-salt refractory sewage, improves the operation flexibility of the device, reduces the operation harshness of the device, and realizes the long-period stable operation of the device. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the structural flow schematic diagram of the present application.

[0027] 101 - fresh catalyst; 102 - sewage; 103 - oxygen; 104 - backwash water; 105 - tail gas; 106 - effluent; 107 - waste catalyst outlet; 201 - raw material pump; 202 - first reactor; 203 - liquid distributor tank one, 303 - liquid distributor tank two, 403 - liquid distributor tank three; 204 - gas distributor one, 306 - gas distributor two, 406 - gas distributor three; 205 - ozone generator; 205 - sewage pump one, 305 - sewage pump two, 405 - sewage pump three; 302 - second reactor; 304 - filter element one, 404 - filter element two; 402 - third reactor; 501 - gas-liquid separator; 502 - ozone destroyer. DETAILED DESCRIPTION

[0028] The application will be further described in detail below with reference to the accompanying drawings.

[0029] As Figure 1 shown, a coal chemical high-concentration salt difficult-to-degrade wastewater ozone catalytic oxidation treatment process comprises the following steps:

[0030] a) Oxygen 103 passes through an ozone generator 205 to generate ozone-containing gas, which is divided into three paths and enters the bottom of a first reactor 202, a second reactor 302, and a third reactor 402, and is dispersed into 60-100 um micro-bubbles through a gas distributor, and then contacts with wastewater 102 and a catalyst to generate a catalytic oxidation reaction, and is discharged from the top of the reactor and enters a gas-liquid separator 501, the separated gas enters an ozone destroyer 502 and is discharged as tail gas 105, and the separated liquid is mixed with the effluent 106 from the bottom of the third reactor 402 and is discharged from the device;

[0031] b) The feed wastewater 102 enters the top of the three reactors in turn and is discharged from the bottom through a raw material pump 201, and forms countercurrent contact with the ozone-containing gas in the reactor as described in step a) and completes the catalytic oxidation reaction; a liquid distributor is arranged at the water inlet of the top of each reactor, and the flow of the wastewater 102 between the reactors is transported by a wastewater 102 pump; a filter core is arranged at the effluent outlet of the bottom of the second reactor 302 and the third reactor 402;

[0032] c) Fresh catalyst 101 is supplemented from the top of the second reactor 302 and the third reactor 402, and the spent catalyst is discharged from the bottom of the reactor.

[0033] The volume ratio of the oxygen 103 to the feed wastewater 102 is (3-12):1, the reaction temperature is 10-45℃, the liquid space velocity of the wastewater 102 is 0.25-1.5h -1 , and the pH of the wastewater 102 is 7-8;

[0034] The volume ratio of the ozone-containing gas at the bottom of the first reactor 202, the second reactor 302, and the third reactor 402 in step a) is (1-3):(0.5-2.5):(1.5-4.0), the maximum utilization of ozone is realized and the COD reduction rate of the wastewater 102 is improved by combining the mechanism of each group of competitive reactions and the mechanism of step-by-step degradation of organic matter in the wastewater 102 with the operating parameters;

[0035] The water level in the first reactor 202, the second reactor 302 and the third reactor 402 in step a) is 85-90% of the internal height of the reactor, and the gas content of the sewage 102 is 5-23%, so that the micro-bubble size of the device is controlled in a suitable range, avoiding insufficient ozone utilization and loss, and preventing the actual residence time of the sewage 102 from being reduced and the degradation depth of the sewage 102 from being insufficient due to the long residence time of the invalid gas after ozone consumption.

[0036] The catalyst in step a) is activated carbon loaded with active metal oxides, and the particle size is 0.5-2.0 mm, which ensures that the catalyst is in a fluidized floating state in the reaction system, enhances the phase switching frequency of the gas-liquid-solid three phases, and thus enhances the reaction efficiency of the catalyst.

[0037] The catalyst in step a) is a core-shell structure catalyst, the inner core is one of silicon carbide, stainless steel slag, zirconia or silica, the shell layer is a mixture of alumina and active metal oxides, the particle size of the core-shell structure catalyst is 150-800 um, and the density is 1.75-4.63 g / cm 3 .

[0038] The active metal oxide in step a) is one or a combination of several of iron oxide, copper oxide, zinc oxide and nickel oxide.

[0039] The volume of the catalyst in the second reactor 302 and the third reactor 402 accounts for 10-35% of the volume of the sewage 102.

[0040] The backwashing pipeline is arranged at the bottom water outlet of the second reactor 302 and the third reactor 402 in step b) to periodically flush the filter core.

[0041] In order to more clearly show the present application, specific operation examples are given as follows:

[0042] Example 1:

[0043] The volume ratio of oxygen 103 to feed sewage 102 is 7.4:1, the reaction temperature is 25℃, the liquid space velocity of the sewage 102 is 0.5h -1 , the pH of the sewage 102 is 7; the volume ratio of the ozone-containing gas at the bottom of the first reactor 202, the second reactor 302 and the third reactor 402 is 2:1:2.5; the water level in the first reactor 202, the second reactor 302 and the third reactor 402 is 85% of the internal height of the reactor, and the gas content of the sewage 102 is 7.2%; the catalyst is activated carbon loaded with active metal oxides, the particle size is 1.5 mm, the active metal oxide is iron oxide, and the volume of the catalyst in the second reactor 302 and the third reactor 402 accounts for 25% of the volume of the sewage 102.

[0044] Example 2

[0045] The volume ratio of oxygen 103 to feed wastewater 102 was 8:1, the reaction temperature was 25°C, the liquid hourly space velocity of wastewater 102 was 0.3h -1 , the pH of wastewater 102 was 7; the volume ratio of ozone gas at the bottom of first reactor 202, second reactor 302 and third reactor 402 was 1:1:2; the wastewater level in first reactor 202, second reactor 302 and third reactor 402 was 90% of the internal height of the reactor, and the gas holdup of wastewater 102 was 9.6%; the catalyst was a core-shell catalyst, the core was silicon carbide, the shell was a mixture of alumina and active metal oxide, the particle size of the core-shell catalyst was 200um, the density was 1.86g / cm 3 , and the active metal oxide was copper oxide; the volume of catalyst in second reactor 302 and third reactor 402 accounted for 15% of the volume of wastewater 102.

[0046] Example 3

[0047] The volume ratio of oxygen 103 to feed wastewater 102 was 4:1, the reaction temperature was 45°C, the liquid hourly space velocity of wastewater 102 was 1.0h -1 , the pH of wastewater 102 was 7; the volume ratio of ozone gas at the bottom of first reactor 202, second reactor 302 and third reactor 402 was 1:1:1; the wastewater level in first reactor 202, second reactor 302 and third reactor 402 was 90% of the internal height of the reactor, and the gas holdup of wastewater 102 was 5.5%; the catalyst was a core-shell catalyst, the core was zirconia, the shell was a mixture of alumina and active metal oxide, the particle size of the core-shell catalyst was 150um, the density was 3.43g / cm 3 , and the active metal oxide was copper oxide; the volume of catalyst in second reactor 302 and third reactor 402 accounted for 18% of the volume of wastewater 102.

[0048] Comparative Example 1

[0049] Oxygen 103 passes through the ozone generator 205 to generate ozone-containing gas, which is divided into three paths to enter the bottom of the first reactor 202, the second reactor 302 and the third reactor 402, and contacts with sewage 102 and catalyst to occur catalytic oxidation reaction, and is discharged from the top of the reactor and enters the gas-liquid separator 501, the separated gas enters the ozone destroyer 502 and discharges tail gas 105, and the liquid is mixed with the effluent 106 at the bottom of the third reactor 402 and discharged from the device; the feed sewage 102 enters the bottom of the three reactors in turn and is discharged from the top by the raw material pump 201, and the sewage 102 flows between the reactors by the sewage 102 pump; the middle part of the second reactor 302 and the third reactor 402 is provided with a fixed bed catalyst bed. Among them, the volume ratio of oxygen 103 and feed sewage 102 is 10:1, the reaction temperature is 25℃, the liquid space velocity of sewage 102 is 0.3h-1, and the pH of sewage 102 is 7; the volume ratio of ozone-containing gas at the bottom of the first reactor 202, the second reactor 302 and the third reactor 402 is 1:0.5:4.0; the catalyst is a commercially available 6-10mmde porcelain ball catalytic oxidation catalyst.

[0050] Comparative Example 2:

[0051] Oxygen 103 passes through the ozone generator 205 to generate ozone-containing gas, which is divided into three paths to enter the bottom of the first reactor 202, the second reactor 302 and the third reactor 402, and contacts with sewage 102 and catalyst to occur catalytic oxidation reaction, and is discharged from the top of the reactor and enters the gas-liquid separator 501, the separated gas enters the ozone destroyer 502 and discharges tail gas 105, and the liquid is mixed with the effluent 106 at the bottom of the third reactor 402 and discharged from the device; the feed sewage 102 enters the bottom of the three reactors in turn and is discharged from the top by the raw material pump 201, and the sewage 102 flows between the reactors by the sewage 102 pump. Among them, the volume ratio of oxygen 103 and feed sewage 102 is 8:1, the reaction temperature is 25℃, the liquid space velocity of sewage 102 is 0.3h -1 , and the pH of sewage 102 is 7; the volume ratio of ozone-containing gas at the bottom of the first reactor 202, the second reactor 302 and the third reactor 402 is 1.5:1:3.

[0052] The COD removal capacity of the process for sewage was evaluated by taking RO concentrated salt sewage in a coal chemical industry park as raw material, and the COD of the sewage was 430mg / L. The evaluation results of Examples 1-3 and Comparative Examples 1 and 2 are shown in Table 1.

[0053] Table 1 COD removal rate of coal chemical industry sewage

[0054]

[0055]

[0056] As can be seen from Table 1, the sewage COD removal rate of the application is obviously higher based on the RO concentrated salt sewage of the coal chemical industry park with high COD.

[0057] The above examples are only used to illustrate the technical solutions of the present application, and are not limited to the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A coal chemical high-concentration salt non-biodegradable wastewater ozone catalytic oxidation treatment process, characterized in that, The method comprises the following steps: a) Oxygen (103) passes through an ozone generator (205) to generate ozone-containing gas, which is divided into three parts and enters the bottom of a first reactor (202), a second reactor (302), and a third reactor (402), is dispersed into 60-100-μm microbubbles through a gas distributor at the bottom of the reactor, and then contacts sewage (102) and a catalyst to generate a catalytic oxidation reaction, is discharged from the top of the reactor and enters a gas-liquid separator (501), the separated gas enters an ozone destroyer (502) and is discharged as tail gas (105), and the separated liquid is mixed with effluent (106) from the bottom of the third reactor (402) and is discharged from the device; b) The feed sewage (102) enters the top of the three reactors in sequence through a raw material pump (201) and is discharged from the bottom, contacts the ozone-containing gas in the reactor to form countercurrent contact and completes the catalytic oxidation reaction, a liquid distributor is arranged at the water inlet at the top of each reactor, and the flow of the sewage (102) between the reactors is transported by the raw material pump (102); a filter core is arranged at the effluent outlet at the bottom of the second reactor (302) and the third reactor (402); c) Fresh catalyst (101) enters the top of the second reactor (302) and the third reactor (402) to supplement fresh catalyst (101), and the spent catalyst is discharged from the bottom of the reactor.

2. The coal chemical high-concentration salt and refractory wastewater ozone catalytic oxidation treatment process according to claim 1, characterized in that, The volume ratio of the oxygen (103) and the feed sewage (102) is (3-12):1, the reaction temperature is 10-45℃, the liquid space velocity of the sewage (102) is 0.25-1.5h -1 .

3. The coal chemical high-concentration salt and refractory wastewater ozone catalytic oxidation treatment process according to claim 1, characterized in that, In step a), the volume ratio of the ozone-containing gas at the bottom of the first reactor (202), the second reactor (302), and the third reactor (402) is (1-3):(0.5-2.5):(1.5-4.0).

4. The coal chemical high-concentration salt and refractory wastewater ozone catalytic oxidation treatment process according to claim 1, characterized in that, In step a), the water level of the sewage in the first reactor (202), the second reactor (302), and the third reactor (402) is 85-90% of the internal height of the reactor, and the gas content of the sewage 102 is 5-23%.

5. The coal chemical high-concentration salt and refractory wastewater ozone catalytic oxidation treatment process according to claim 1, characterized in that, In step a), the catalyst is activated carbon loaded with active metal oxides, and the particle size is 0.5-2.0 mm.

6. The coal chemical high-concentration salt and refractory wastewater ozone catalytic oxidation treatment process according to claim 5, characterized in that, The catalyst of step a) is a core-shell structure catalyst, the inner core is one of silicon carbide, stainless steel slag, zirconia or silica, the shell is a mixture of alumina and active metal oxide, the particle size of the core-shell structure catalyst is 150-800um, the density is 1.75-4.63g / cm 3 , the ratio of the inner core radius to the shell thickness is 2-4:1, and the mass of the active metal oxide accounts for 3-17% of the mass of the shell.

7. The coal chemical high-concentration salt and refractory wastewater ozone catalytic oxidation treatment process according to claim 5, characterized in that, The active metal oxides are one or a combination of iron oxide, copper oxide, zinc oxide, and nickel oxide.

8. The coal chemical high-concentration salt and refractory wastewater ozone catalytic oxidation treatment process according to claim 1, characterized in that, In the second reactor (302) and the third reactor (402), the volume of the catalyst accounts for 10-35% of the volume of the sewage (102).

9. The coal chemical high-concentration salt and refractory wastewater ozone catalytic oxidation treatment process according to claim 1, characterized in that, In step b), a backwashing pipeline is arranged at the effluent outlet at the bottom of the second reactor (302) and the third reactor (402) to periodically flush the filter core.

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