Method and device for near zero emission of methanol to olefins washing water

Abstract

The application discloses a methanol-to-olefin washing water near-zero emission process and device, relates to the field of difficult-to-degrade sewage treatment and reuse, and adopts a device composed of a sewage stripping tower, a micro-channel adsorber, an electrocoagulation cyclone reactor and a buffer sedimentation tank; the process comprises the following steps: first, washing water from the bottom of a washing tower enters the sewage stripping tower, most of the organic matters in the washing water are stripped, and the oil content is reduced; then, the stripped water enters the micro-channel adsorber, the organic matters in the water are further removed through built-in adsorbents, and the suspended matter content is reduced; then, the adsorbed water enters the electrocoagulation cyclone reactor, and the deep removal of the organic matters in the water is realized through electrochemical action; finally, the clear liquid generated by electrocoagulation can be near-zero emission. The application effectively combines the sewage stripping technology, the micro-channel adsorption technology and the electrocoagulation cyclone technology, has the technical effects of improving the purification degree of the washing water, prolonging the operation cycle of the washing tower and ensuring the stable operation of the water system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of refractory wastewater treatment and reuse, in particular to a process and device for near-zero discharge of methanol-to-olefins water washing water. BACKGROUND

[0002] In recent years, the Methanol To Olefins (MTO) technology has been booming in China, among which the DMTO process is the most widely used in the actual industrialization process. MTO process is a process for producing low-carbon olefins from coal-based or natural gas-based synthesized methanol, which realizes the process route of producing basic organic chemical raw materials from coal, making China partly free from the situation of being subject to oil resources, and has a significant impact on China's coal chemical industry. The MTO device water system blockage is a problem in the industry. The water washing water system, as an important part of the MTO device water system, due to the loss of fine catalyst powder in the reaction system, the characteristics of the reaction mechanism, and other reasons, causes the micro-fine catalyst particles and wax-like substances to adhere and deposit in the water system equipment and pipelines, resulting in a series of problems such as decreased heat exchange efficiency of heat exchange equipment, increased water washing tower pressure drop, and frequent tower flushing, which affects the long-term stable operation of the device. At the same time, the high concentration of organic matter in the water washing water causes high load on the end sewage treatment plant, which is not conducive to the daily stable operation of the sewage treatment unit.

[0003] Therefore, in order to ensure the normal operation of the water system and achieve near-zero discharge of water washing water, it is necessary to effectively remove the high-concentration organic oxygen-containing compounds, part of the catalyst powder, and oil wax-like substances such as aromatic hydrocarbons and alkanes in the water washing water.

[0004] The current common methods for realizing deep separation of oxygen-containing compounds, suspended solids, and oil substances in water washing water mainly include chemical flocculation, air floatation precipitation, precision filtration, membrane filtration, advanced oxidation, and adsorption method. However, the chemical flocculation has poor treatment precision, high reagent cost, and easy secondary pollution; the air floatation precipitation has good treatment effect, but high operation cost, complex operation, and easy mud accumulation affecting the treatment effect; the precision filtration has high precision, but is easily blocked by micro-fine catalyst particles and wax-like substances in the water washing water for long-term use; the membrane filtration has good operation effect, but has the disadvantages of easy blockage, high maintenance cost, and high cost due to high content of suspended solids and oil substances in the water washing water; the advanced oxidation can efficiently degrade various organic matters without secondary pollution, but has high energy consumption and harsh reaction conditions; and the adsorption method can efficiently remove organic components in the water washing water, but is restricted by the high-efficiency regeneration of the adsorbent.

[0005] Chinese patent application CN114180732A discloses a coal-to-olefins wastewater treatment device, which can efficiently adsorb oil stains in wastewater through an embedded filter core, but does not mention the removal effect of oxygen-containing compounds and suspended solids.

[0006] Chinese patent application CN113045376A discloses a methanol-to-olefins water purification boiling bed purification method and device, which adopts a sewage stripping tower in series with a boiling bed process to effectively remove most of the oxygenates in the water washing water, while reducing the solid particles and oil substances in the water washing water to a low level, but cannot achieve the near-zero emission standard, and the effluent COD is relatively high.

[0007] Chinese patent application CN107720872A discloses a methanol-to-olefins device water washing water purification device and purification method, which uses a particle bed to intercept particles in the water, and uses the adsorption and coalescence of the medium particles in the particle bed to the oil substances to make the fine oil droplets in the water grow and separate by gravity settling after gathering. When the particles are saturated, gas and water are introduced in reverse to promote the desorption and regeneration of the saturated medium particles. The implementation method has good separation effect on catalyst particles and oil substances in the water washing water, but does not mention the removal of oxygenates, and the effluent cannot achieve the near-zero emission standard.

[0008] Chinese patent application CN108328761B discloses a method and device for prolonging the continuous operation cycle of the MTO water washing water process, which performs micro-cyclone treatment on the MTO water washing water to remove free oil in the water, further sends the water washing water after micro-cyclone oil removal into a boiling bed separator for treatment to remove emulsified oil, dispersed oil and catalyst fines, and the effluent is further treated in a sewage stripping tower. The implementation method can efficiently remove solid particles and oil substances in the water washing water, while reducing most of the organic matter, but the COD of the stripped water does not meet the near-zero emission requirement, resulting in high daily load of the sewage treatment unit.

[0009] Chinese patent application CN114477321B discloses a device and use method for purifying MTO device water washing water, which sends the MTO water washing water to the purification device to filter and intercept the fine powder and oil substances in the water by the filter bed layers of each pipe. This method solves the problem that the existing MTO water washing water is rich in ultra-fine catalyst powder with an average particle size of 1-20 pm, which is difficult to remove and continuously accumulates in the water system to affect subsequent unit operations, but does not involve a removal unit for high-concentration COD in the water washing water, and the effluent far fails to meet the near-zero emission standard.

[0010] In summary, the current treatment methods for methanol-to-olefins water washing water mainly focus on the removal of catalyst particles and oil substances, and the removal of high-concentration COD only uses a sewage stripping unit or directly sends it to the back end, which makes the water washing water treatment incomplete, affects the stable operation of the water system, and intensifies the operation load of the sewage treatment plant, impacting the daily operation of the sewage treatment unit. SUMMARY

[0011] The present application aims at solving the problems existing in the prior art and provides a methanol-to-olefin water washing water near-zero discharge process and device.

[0012] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0013] A methanol-to-olefin water washing water near-zero discharge process, the process comprising the following steps:

[0014] S1: the water washing water from the bottom of the methanol-to-olefin water washing tower enters the sewage stripping system, and most of the organic matters in the water are stripped under the action of reboiling steam to reduce the oil content;

[0015] S2: the stripped water enters the micro-channel adsorber, and the organic matters in the water are further removed through the built-in combined adsorption particles to reduce the suspended matter content;

[0016] S3: the adsorbed water enters the electrocoagulation hydrocyclone reactor, and the electrochemical effect generated by the built-in iron-carbon micro-electrolysis filler is used to realize the deep removal of the organic matters in the water, the clear liquid generated by the electrocoagulation hydrocyclone reactor can be near-zero discharged, the dregs generated in the electrocoagulation hydrocyclone reactor are returned to the micro-channel adsorber for treatment, and the bottom sludge is sent to the buffer settling tank.

[0017] Further, when the adsorption particles in the micro-channel adsorber run to the saturated state, the adsorption particles are backwashed and regenerated, the regenerated thick liquid enters the buffer settling tank after adjustment, and then the bottom sludge is sent to the subsequent concentration unit.

[0018] A methanol-to-olefin water washing water near-zero discharge device, the device comprising a sewage stripping system, a micro-channel adsorber, an electrocoagulation hydrocyclone reactor and a buffer settling tank, the outlet of the sewage stripping system being communicated with the inlet of the micro-channel adsorber, the outlet of the micro-channel adsorber being communicated with the inlet of the electrocoagulation hydrocyclone reactor, the electrocoagulation hydrocyclone reactor being further provided with a clear liquid outlet, a dregs outlet and a bottom sludge outlet, the dregs outlet being communicated with the inlet of the micro-channel adsorber, and the bottom sludge outlet being communicated with the inlet of the buffer settling tank, wherein:

[0019] The sewage stripping tower is used for heat exchange through the reverse contact of the reboiling steam from the bottom and the water washing water from the top, most of the organic matters in the water washing water are stripped to reduce the oil content, the micro-channel adsorber is built-in with a particle bed to further remove the organic matters in the water to reduce the suspended matter content, and the electrocoagulation hydrocyclone reactor is built-in with an iron-carbon micro-electrolysis filler to generate an electrochemical effect to realize the deep removal of the organic matters in the water.

[0020] Further, the sewage stripping tower is of sieve plate type structure, and the sewage stripping tower is further connected with at least one vertical thermosyphon reboiler, the outlet of the sewage stripping tower is communicated with the inlet of the vertical thermosyphon reboiler and the inlet of the micro-channel adsorber respectively, and the outlet of the vertical thermosyphon reboiler is communicated with the sewage stripping tower.

[0021] Further, the particle bed layer is formed by combination of carbon-based materials and polymer materials with particle sizes of 0.5-1 mm, and includes: anthracite, activated carbon, walnut shell and macroporous adsorption resin.

[0022] Further, the water distributor is arranged below the particle bed layer in the micro-channel adsorber, the backwashing water enters the particle bed layer through the uniformly arranged water distributor, and the backwashing gas inlet pipe in the annular shape is further arranged on one side of the micro-channel, a plurality of gas inlets are uniformly arranged on the inlet pipe, and the backwashing gas is high-speed injected into the particle bed layer through the uniformly arranged gas inlets, so that the backwashing water and the backwashing gas are backwashed in the particle bed layer.

[0023] The flow ratio of the backwashing water to the backwashing gas is 1:6, and the backwashing time is 50-60 minutes.

[0024] Further, the pressurized backwashing gas on the steam inlet pipe of the micro-channel adsorber further strengthens the increase of the adsorption particle surface energy in the bed layer.

[0025] Further, the three-phase separator is arranged on the top of the micro-channel adsorber, and the guide vane is arranged in the three-phase separator; the three-phase separator is used for strengthening the desorption of the pollutants on the particle surface and in the pore channel by using the periodic oscillation centrifugal force generated by the self-rotation coupling motion of the medium particles in the cyclone field in the regeneration process.

[0026] The self-rotation speed of the medium particles is 2200-5400 revolutions / second, and the revolution speed is 10-15 m / s.

[0027] Further, the anode conductive rod is arranged in the shell of the electrocoagulation cyclone reactor, a plurality of iron-carbon micro-electrolysis fillers are uniformly connected to the anode conductive rod through the supporting tray, the cathode conductive sleeve is arranged outside the anode conductive rod in the interval, and the inlet of the electrocoagulation cyclone reactor is located outside the cathode conductive sleeve.

[0028] The particle size of the iron-carbon micro-electrolysis filler is 4-8 mm.

[0029] Further, the liquid-solid separators are arranged in parallel in multiple groups in the shell of the electrocoagulation cyclone reactor close to the top of the shell, and the liquid-solid separators realize efficient separation of the clear liquid and the dregs produced by electrocoagulation by using the different centrifugal forces caused by the density difference of components in the cyclone field.

[0030] Compared with the prior art, the beneficial effects of the present application are:

[0031] 1. The application provides a methanol-to-olefin washing water near-zero discharge process and device, which effectively combines sewage stripping technology, micro-channel adsorption technology and electric flocculation cyclone technology, so that the purification degree of washing water is higher, and the operation cycle of the washing tower is effectively improved, the stability of the water system operation is ensured, the problems of incomplete methanol-to-olefin washing water treatment and too high COD concentration of external discharge are effectively solved, and near-zero discharge of washing water is realized.

[0032] 2. The whole operation process of the application is carried out in a physical field, and no other pollutants are generated. At the same time, no additional chemical agents and biological reagents are added in the treatment process, so as to ensure that the whole process is green, environmentally friendly and pollution-free. The overall process and equipment investment is low, the separation medium is easy to regenerate, the consumption rate of iron-carbon micro-electrolysis filler is low, the overall energy consumption of the process is low, and the maintenance cost is low. And the device can be popularized to various industrial wastewater treatment occasions of high COD, suspended solids and oil substances. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a schematic diagram of a methanol-to-olefin washing water near-zero discharge device in the application;

[0034] Figure 2 It is a PID schematic diagram of the sewage stripping system of the application;

[0035] Figure 3 It is a schematic diagram of the internal structure of the micro-channel adsorber of the application;

[0036] Figure 4 It is a schematic diagram of the structure of the backwash water and backwash gas channel at the bottom of the micro-channel adsorber of the application;

[0037] Figure 5 It is a schematic diagram of the structure of the water distributor in the micro-channel adsorber of the application;

[0038] Figure 6 It is a schematic diagram of the structure of the gas inlet pipe in the micro-channel adsorber of the application;

[0039] Figure 7 It is a schematic diagram of the structure of the electric flocculation cyclone reactor of the application;

[0040] Figure 8 It is a working principle diagram of the electric flocculation cyclone reactor of the application.

[0041] In the figure: 1, sewage stripping system; 1-1, sewage stripping tower; 1-2, first vertical thermosyphon reboiler; 1-3, second vertical thermosyphon reboiler; 1-4, sewage stripping water pump; 1-5, washing water inlet; 1-6, stripping tower outlet;

[0042] 2, centrifugal pump;

[0043] 3, micro-channel adsorber; 3-1, equipment shell; 3-2, particle bed; 3-3, vortex preventer; 3-4, water distributor; 3-4-1, partition plate; 3-4-2, support structure; 3-4-3, water distribution cap insertion hole; 3-5, water cap; 3-6, gas inlet pipe; 3-6-1, flow guide pipe; 3-6-2, annular channel; 3-6-3, gas outlet hole; 3-7, water inlet distributor; 3-8, three-phase separator; 3-9, flow guide blade; 3-10, micro-channel adsorber inlet; 3-11, micro-channel adsorber outlet; 3-12, backwash gas inlet; 3-13, regenerated thick liquid outlet; 3-14, blowdown port; 3-15, exhaust port;

[0044] 4, electrocoagulation cyclone reactor; 4-1, electrocoagulation cyclone reactor inlet; 4-2, outer cavity; 4-3, cathode conductive sleeve; 4-4, inner cavity; 4-5, iron-carbon micro-electrolysis filler; 4-6, supporting tray; 4-7, anode conductive rod; 4-8, bottom sludge outlet; 4-9, liquid-solid separator; 4-10, clear liquid outlet; 4-11, dregs outlet; 4-12, reactor shell;

[0045] 5, buffer settling tank. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Embodiment 1

[0047] Affected by factors such as catalyst fine powder loss of the reaction system and reaction mechanism characteristics, fine catalyst particles and wax-like dirt and other dirt substances are attached and deposited in water system equipment and pipelines, resulting in a series of problems such as heat exchange equipment heat exchange efficiency decline, water washing tower pressure drop increase, and frequent tower flushing, which affect the long-period stable operation of the device. At the same time, the high concentration of organic matter existing in the water washing water causes high load of the end sewage treatment plant, which is not conducive to the daily stable operation of the sewage treatment unit. Therefore, the present application adopts the process combination of the sewage stripping system 1, the micro-channel adsorber 3, the electrocoagulation cyclone reactor 4 and the buffer settling tank 5, to realize near-zero discharge of the methanol-to-olefin water washing water.

[0048] As Figure 1As shown, a methanol to olefins washing water near zero discharge device includes a waste stripping system 1, a centrifugal pump 2, a micro-channel adsorber 3, an electrocoagulation cyclone reactor 4 and a buffer sedimentation tank 5. The waste stripping system 1 is provided with a washing water inlet 1-5 and a stripping tower outlet 1-6. The stripping tower outlet 1-6 is connected to the micro-channel adsorber inlet 3-10 through the centrifugal pump 2. The bottom of the micro-channel adsorber 3 is provided with a micro-channel adsorber outlet 3-11. The micro-channel adsorber outlet 3-11 is connected to the electrocoagulation cyclone reactor inlet 4-1. The electrocoagulation cyclone reactor 4 is further provided with a clear liquid outlet 4-10, a scum outlet 4-11 and a bottom mud outlet 4-8. The clear liquid outlet 4-10 is used to discharge the clear liquid obtained after treatment. The scum outlet 4-11 is connected to the micro-channel adsorber inlet 3-10. The bottom mud outlet 4-8 is connected to the buffer sedimentation tank 5 inlet. Wherein:

[0049] The washing water enters the waste stripping system 1 from top to bottom through the washing water inlet 1-5. The washing water entering from top to bottom in the waste stripping system 1 is in counter-heat contact with the reboiled steam entering from bottom to top. Most of the organic matter in the washing water is stripped out, reducing the oil content. Then the washing water enters the micro-channel adsorber 3 through the micro-channel adsorber inlet 3-10 from the stripping tower outlet 1-6, which is pumped by the centrifugal pump 2. The washing water entering from the micro-channel adsorber inlet 3-10 is further removed of organic matter in the water by the built-in combined adsorption particles in the micro-channel adsorber 3, reducing the suspended solids content. Then the washing water enters the electrocoagulation cyclone reactor 4 through the electrocoagulation cyclone reactor inlet 4-1 from the micro-channel adsorber outlet 3-11. The washing water entering from the electrocoagulation cyclone reactor inlet 4-1 is further removed of organic matter in the water by the built-in iron-carbon micro-electrolysis filler 4-5 in the electrocoagulation cyclone reactor 4 to achieve deep removal of organic matter in the water. The clear liquid produced in the electrocoagulation cyclone reactor 4 is discharged through the clear liquid outlet 4-10. The scum is discharged through the scum outlet 4-11. The bottom mud is discharged through the bottom mud outlet 4-8 into the buffer sedimentation tank 5.

[0050] In addition, see Figure 1 The micro-channel adsorber 3 is further provided with a backwash gas inlet 3-12. The micro-channel adsorber outlet 3-11 is also used as a backwash water inlet. The micro-channel adsorber 3 is further provided with a regeneration concentrated liquid outlet 3-13. The micro-channel adsorber 3 is connected to the buffer sedimentation tank 5 through the regeneration concentrated liquid outlet 3-13. The backwash gas and the backwash water enter the micro-channel adsorber 3 through the backwash gas inlet 3-12 and the backwash water inlet, respectively, to backwash and regenerate the micro-channel adsorber 3. The regeneration concentrated liquid formed during the backwashing and regeneration process enters the buffer sedimentation tank 5 through the regeneration concentrated liquid outlet 3-13.

[0051] The bottom mud received in the buffer sedimentation tank 5 and the regeneration concentrated liquid are separated by sedimentation, and the tank bottom mud is sent to a subsequent concentration unit.

[0052] Further, as shown in Figure 2As shown, the wastewater stripping system 1 includes a wastewater stripping tower 1-1, which has a sieve plate structure. The wastewater stripping tower 1-1 is also connected to two vertical thermosiphon reboilers, namely a first vertical thermosiphon reboiler 1-2 and a second vertical thermosiphon reboiler 1-3. The stripping tower outlet 1-6 is connected to the inlets of the two vertical thermosiphon reboilers and the microchannel adsorber inlet 3-10 (not shown in the figure), respectively. The outlets of the two vertical thermosiphon reboilers are connected back to the wastewater stripping tower 1-1.

[0053] Specifically, the wastewater stripping tower 1-1 has a wash water inlet 1-5 on one side of its upper part and two steam inlets (not shown in the figure) on one side of its lower part. The bottom of the stripping tower also has a stripping tower outlet 1-6. The stripping tower outlet 1-6 is connected to two vertical thermosiphon reboilers via one of its branches. The outlets of the vertical thermosiphon reboilers are connected to the steam inlets on both sides. The stripping tower outlet 1-6 is connected to a wastewater stripping water pump 1-4 via another branch. The wastewater stripping water pump 1-4 is then connected to the microchannel adsorber inlet 3-10.

[0054] The wastewater stripping tower 1-1 has a built-in multi-layer sieve tray. Preferably, the sieve tray is arranged in 40 layers evenly and alternately along the vertical direction of the wastewater stripping tower 1-1.

[0055] The operation process of the wastewater stripping system 1 is as follows: the wash water from the washing tower enters from top to bottom through the wash water inlet 1-5 at the top of the wastewater stripping tower 1-1. The stripping steam heated by the first vertical thermosiphon reboiler 1-2 and the second vertical thermosiphon reboiler 1-3 enters from bottom to top through the steam inlet in the wastewater stripping tower 1-1. The wash water from top to bottom and the reboiler steam from bottom to top undergo convective heat exchange on the 40-layer sieve trays in the wastewater stripping tower 1-1. After stripping treatment, the wash water exits from the stripping tower outlet 1-6 at the bottom of the wastewater stripping tower 1-1. Part of it is sent by the branch pipe to the first vertical thermosiphon reboiler 1-2 and the second vertical thermosiphon reboiler 1-3 and heated by heating steam at 1.0 MPaG and 184℃ to serve as the carrier gas for stripping and continue to circulate. The other part is sent by the wastewater stripping water pump 1-4 to the microchannel adsorber 3 for further treatment. The wastewater stripping system removes most of the organic matter from the water, reducing the oil content.

[0056] Furthermore, such as Figure 3 As shown, the microchannel adsorber 3 includes a housing 3-1, an inlet 3-10 located at the top of the housing 3-1, a water distributor 3-7 located near the inlet inside the housing 3-1, a particle bed 3-2 located inside the housing 3-1, a water distributor 3-4 located below the particle bed 3-2, a number of water caps 3-5 evenly arranged on the water distributor 3-4, an outlet 3-11 located at the bottom of the housing 3-1, and an anti-vortex device 3-3 located near the outlet inside the housing 3-1.

[0057] The adsorbent in granular bed 3-2 is a combination of carbon-based materials and polymer materials with a particle size of 0.5-1 mm, mainly including: anthracite, activated carbon, walnut shells, macroporous adsorption resin, etc. The adsorbent in granular bed 3-2 is adjusted according to the actual operating conditions to ensure that the adsorber achieves stable operation over a long period of time.

[0058] In addition, to meet the backwashing operation requirements of the microchannel adsorber 3, such as Figure 4 As shown, the microchannel adsorber outlet 3-11 at the bottom serves as the backwash water inlet. An air inlet pipe 3-6 is provided on one side of the equipment housing 3-1. This air inlet pipe 3-6 is located above the water distributor 3-4 and inside the particle bed 3-2, serving as the backwash air inlet 3-12.

[0059] At the same time, return Figure 3 and combined Figure 4 A three-phase separator 3-8 is also installed near its inlet inside the microchannel adsorber 3. The three-phase separator 3-8 also has guide vanes 3-9. The bottom of the three-phase separator 3-8 is the backwash fluid inlet (not shown in the figure), and the two sides of the three-phase separator 3-8 have drain ports 3-14 (i.e., regeneration concentrate outlets 3-13), and the top has an exhaust port 3-15. During the regeneration process, the three-phase separator 3-8 utilizes the periodic oscillating centrifugal force generated by the self-revolution coupling motion of the medium particles in the swirling flow field to enhance the desorption of pollutants from the particle surface and pores. The rotational speed of the medium particles is 2200-5400 rpm, and the revolution speed is 10-15 m / s.

[0060] More specifically, such as Figure 5 As shown, the water distributor 3-4 includes a partition plate 3-4-1, a support structure 3-4-2, and water distribution cap insertion holes 3-4-3. Several water distribution cap insertion holes 3-4-3 are fixed on the partition plate 3-4-1 by the support structure 3-4-2, and water caps 3-5 are fixed in the water distribution cap insertion holes 3-4-3. Backwash water enters the granular bed 3-2 through the water distribution caps 3-5 evenly arranged on the water distributor 3-4.

[0061] like Figure 6 As shown, the air inlet pipe 3-6 includes a guide pipe 3-6-1, an annular channel 3-6-2, and an air outlet 3-6-3. Preferably, the guide pipe 3-6-1 is a straight pipe, and the annular channel 3-6-2 is a circular pipe. The guide pipe 3-6-1 is connected to the annular channel 3-6-2. Several air outlets 3-6-3 are evenly provided at the top of the annular channel 3-6-2. The backwash gas enters the annular channel 3-6-2 through the guide pipe 3-6-1, and then is ejected at high speed from the air outlets 3-6-3 into the particle bed 3-2.

[0062] The backwash gas and the backwash water are mixed to flush the particle bed. Preferably, the flow ratio of the backwash water to the backwash gas is 1:6, and the backwash time is 50-60 minutes.

[0063] In the backwash structure, the backwash gas and the backwash liquid are introduced into the micro-channel adsorber 3 respectively, effectively avoiding the mutual extrusion of the gas-liquid two-phase when entering the particle bed, and the pressure drop fluctuation is obvious, which avoids affecting the flow of the two.

[0064] The working principle of the micro-channel adsorber 3 is as follows: when the micro-channel adsorber 3 is normally running, the water washing water is introduced into the equipment shell 3-1 from the top micro-channel adsorber inlet 3-10, is sent to the particle bed 3-2 through the water inlet distributor 3-7, and after being separated by the particle bed 3-2, the waste water is sent to the subsequent equipment through the water distributor 3-4, the vortex preventer 3-3 and the bottom micro-channel adsorber outlet 3-11; when the micro-channel adsorber 3 is switched to backwash operation, the backwash water is introduced into the equipment from the bottom backwash water inlet (i.e. the micro-channel adsorber outlet 3-11), the backwash gas is introduced into the side wall from the gas inlet pipe 3-6, the gas-liquid two-phase is mixed in the particle bed 3-2, the bed is in a boiling state, the pollutants between the separation media are released, and the media are regenerated and cleaned; the waste water containing the separation media and the pollutants is introduced into the top three-phase separator 3-8 by the backwash fluid, and under the action of the guide vane 3-9, the media particles are washed in the cyclone field, the media regeneration is strengthened, the media particles are recovered, the pollutants are discharged from the side discharge port 3-14 of the equipment, and the backwash gas is discharged from the top gas outlet 3-15.

[0065] Preferably, the backwash process of the micro-channel adsorber 3 adopts the adsorber outlet water mixed steam for backwashing, and the pressurized steam is used to strengthen the increase of the surface energy of the adsorption particles in the bed.

[0066] Further, as shown in Figure 7 The electrocoagulation cyclone reactor 4 includes an electrocoagulation cyclone reactor inlet 4-1, an outer cavity 4-2, a cathode conductive sleeve 4-3, an inner cavity 4-4, iron-carbon micro-electrolysis filler 4-5, a supporting tray 4-6, an anode conductive rod 4-7, a bottom mud outlet 4-8, a liquid-solid separator 4-9, a clear liquid outlet 4-10, a scum outlet 4-11 and a reactor shell 4-12. The electrocoagulation cyclone reactor inlet 4-1 is a water inlet pipe, and the bottom mud outlet 4-8, the clear liquid outlet 4-10 and the scum outlet 4-11 are respectively a bottom mud outlet pipe, a clear liquid outlet pipe and a scum outlet pipe.

[0067] The electric flocculation cyclone reactor inlet 4-1 is arranged at the lower part of the reactor shell 4-12, the reactor shell 4-12 is provided with a cathode conductive sleeve 4-3 with the same central axis, an outer cavity 4-2 is formed between the cathode conductive sleeve 4-3 and the reactor shell 4-12, an inner cavity 4-4 is formed in the cathode conductive sleeve 4-3, the outer cavity 4-2 is communicated with the electric flocculation cyclone reactor inlet 4-1, the inner cavity 4-4 is provided with an anode conductive rod 4-7, the anode conductive rod 4-7 is arranged with the same central axis as the reactor shell 4-12, a plurality of iron-carbon micro-electrolysis fillers 4-5 are uniformly connected on the anode conductive rod 4-7 through the supporting tray 4-6, and the plurality of iron-carbon micro-electrolysis fillers 4-5 are vertically and uniformly arranged along the anode conductive rod 4-7, the bottom mud outlet 4-8 is arranged at the bottom of the reactor shell 4-12, the liquid-solid separator 4-9 is arranged in the reactor shell 4-12 close to the top thereof, the clear liquid outlet 4-10 is arranged at the side of the reactor shell 4-12, the floating sludge outlet 4-11 is arranged at the top of the reactor shell 4-12, and the clear liquid outlet 4-10, the floating sludge outlet 4-11 and the liquid-solid separator 4-9 are communicated.

[0068] Preferably, the reactor shell 4-12 is internally filled with iron-carbon micro-electrolysis fillers 4-5 with a particle size of 4-8 mm in order, under the action of an external current, a large number of electrochemical reaction sites are generated, and the organic matter in the water is removed in depth.

[0069] Preferably, a plurality of groups of liquid-solid separators 4-9 are arranged in parallel in the reactor shell 4-12 close to the top, and the clear liquid and the floating sludge generated by electric flocculation are efficiently separated through the different centrifugal forces caused by the density difference of components in the cyclone field.

[0070] In combination with Figure 8 As shown in the figure, the working principle of the electric flocculation cyclone reactor 4 is as follows: the wastewater enters the outer cavity 4-2 from the bottom electric flocculation cyclone reactor inlet 4-1, then passes through the honeycomb-shaped cathode conductive sleeve 4-3 into the inner cavity 4-4, thereby reducing the flow rate of the wastewater, allowing the water in the inner cavity 4-4 to be fully electrically flocculated. Under the action of the cathode conductive sleeve 4-3 and the anode conductive rod 4-7, the iron-carbon micro-electrolysis fillers 4-5 in the supporting tray 4-6 undergo intense electrochemical reactions, and ferrous ions are released into the water. When the wastewater flows upwards through the iron-carbon micro-electrolysis fillers 4-5, the hydroxyl complexes formed by the ferrous ions adsorb the impurities in the wastewater. In addition, the anode conductive rod 4-7 has a certain speed, which is conducive to the further adsorption of impurities in the wastewater by the hydroxyl complexes gathered around the iron-carbon micro-electrolysis fillers 4-5. As the electric flocculation process continues, the generated bottom mud gradually sinks, and when the bottom mud accumulates to a certain weight, it is discharged from the bottom mud outlet 4-8 at the lower end. The floating sludge and the clear liquid gradually move upwards to the liquid-solid separator 4-9, and under the action of the cyclone field, according to the density difference, the clear liquid moves downwards to the clear liquid outlet 4-10 and is discharged, and the floating sludge moves upwards to the floating sludge outlet 4-11 and is discharged.

[0071] Based on the above device, the embodiment also gives a methanol to olefins water washing water near zero emission process, comprising the following steps:

[0072] S1: the washing water from the bottom of the methanol to olefins water washing tower enters the sewage stripping system 1, and most of the organic matters in the water are stripped under the action of reboiling steam to reduce the oil content; when the COD concentration in the methanol to olefins washing water is not higher than 30000 mg / L, and the oil content is not higher than 500 mg / L, after the step S1, the COD concentration in the stripped water is reduced to below 2000 mg / L, and the oil content is reduced to below 20 mg / L;

[0073] S2: the stripped water enters the microchannel adsorber 3, and the built-in combined adsorption particles further remove the organic matters in the water to reduce the suspended matter content; when the organic matter content in the stripped water is relatively high, and the suspended matter concentration is not higher than 100 mg / L, after the step S2, the COD concentration in the adsorbed water is reduced to below 400 mg / L, and the oil content and the suspended matter concentration are reduced to below 5 mg / L;

[0074] S3: the adsorbed water enters the electrocoagulation hydrocyclone reactor 4, and the electrochemical effect generated by the built-in iron-carbon microelectrolysis filler 4-5 realizes the deep removal of the organic matters in the water; the clear liquid generated by the electrocoagulation hydrocyclone reactor 4 can be near zero emission, the scum generated in the electrocoagulation hydrocyclone reactor 4 is returned to the microchannel adsorber 3 for treatment, and the bottom sludge is introduced into the buffer sedimentation tank 5; when the organic matter content in the adsorbed water is relatively high, after the step S2, the COD concentration in the electrocoagulation effluent is reduced to below 60 mg / L, and the oil content and the suspended matter concentration are reduced to below 1 mg / L to meet the near zero emission requirement.

[0075] Through the above steps, the sewage stripping system 1, the microchannel adsorber 3 and the electrocoagulation hydrocyclone reactor 4 are combined in series to realize the gradient removal of the washing water from the methanol to olefins system, so that the near zero emission requirement of the washing water is met.

[0076] In addition, in the above steps, when the adsorption particles in the microchannel adsorber 3 run to the saturated state, the adsorption particles are backwashed and regenerated, the regenerated concentrated liquid enters the buffer sedimentation tank 5, and the tank bottom sludge is sent to the subsequent concentration unit after adjustment.

[0077] Application example

[0078] Based on the device and process flow of the device embodiment 1, an engineering example is given:

[0079] In a 1.8 million tons / year methanol to olefins process, the water from the bottom of the methanol to olefins water scrubber is first sent to the sewage stripping system 1 according to the near zero emission process of the methanol to olefins water scrubber in Example 1, and the most of the organic matters in the water are stripped by the reverse heat exchange between the bottom-up reboiling steam and the top-down water, so as to reduce the oil content; then, the stripped water is sent into the micro-channel adsorber 3 under the action of the centrifugal pump, and the organic matters in the water are further removed by the built-in combined adsorption particles, so as to reduce the suspended matter content; then, the adsorbed water is sent into the electrocoagulation hydrocyclone reactor 4, and the organic matters in the water are deeply removed by the electrochemical effect of the built-in iron-carbon microspheres; finally, the clear liquid produced by the electrocoagulation hydrocyclone reactor 4 can be near zero emission, the scum is returned to the micro-channel adsorber 3 for treatment, and the sludge is sent into the buffer sedimentation tank 5. When the adsorption particles in the micro-channel adsorber 3 run to the saturated state, the adsorption particles are backwashed and regenerated, the regenerated concentrated liquid is sent into the buffer sedimentation tank 5, and the sludge at the bottom of the tank is sent into the subsequent concentration unit after adjustment. The specific operation process and effect are described as follows:

[0080] 1. The water quality conditions are shown in Table 1:

[0081] Table 1

[0082]

[0083] 2. Implementation process and effect

[0084] The methanol to olefins water is 200 m 3 / h for deep treatment, and the water is first sent into the sewage stripping system 1 for preliminary treatment. After the stripping action of the reboiling steam, the effluent COD is lower than 820 mg / L, the suspended matter content is lower than 36 mg / L, the oil content is lower than 12 mg / L, and the turbidity is lower than 40 NTU. Then, the stripped water is sent into the micro-channel adsorber 3 under the action of the centrifugal pump 2, and after the adsorption treatment of the mixed adsorbent, the COD is reduced to 245 mg / L, the suspended matter and oil content are lower than 5 mg / L, and the turbidity is reduced to 6 NTU. Then, the adsorbed water is sent into the electrocoagulation hydrocyclone reactor 4, and after the electrochemical action of the built-in iron-carbon microspheres, the COD concentration of the electrocoagulation clear liquid is reduced to 49 mg / L, the oil content and the suspended matter are not obviously detected, and the turbidity is lower than 1 NTU, which reaches the near zero emission standard. The electrocoagulation scum is returned to the micro-channel adsorber 3, the electrocoagulation sludge and the concentrated water produced after the regeneration of the micro-channel adsorber 3 in the process are sent into the buffer sedimentation tank 5 for sedimentation and separation, and the sludge at the bottom of the tank is sent into the subsequent concentration unit. The effective treatment amount of the water in the whole process is greater than 98%, and no secondary pollution is generated.

[0085] The device and process of Example 1 are used to remove high-concentration COD, suspended solids and oil substances in the water washing water stably, and near-zero discharge can be achieved. Not only the problem of frequent blockage of production devices and pipelines is effectively solved, but also near-zero discharge of wastewater is achieved, the operation load of the end sewage treatment plant is reduced, and a set of 200m 3 / h water washing water advanced treatment device can reduce wastewater treatment by about 1.75 million tons / year and reduce carbon emissions by about 1.53 million tons / year.

[0086] The above merely describes the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can make equivalent replacements or changes according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for methanol to olefins water wash water near zero emission, characterized in that, The process comprises the following steps: S1: the washing water from the bottom of the methanol to olefin washing column enters the sewage stripping system, and most of the organic matters in the water are stripped under the action of reboiling steam to reduce the oil content; S2: the stripped water enters the micro-channel adsorber, and further removes the organic matters in the water through the built-in combined adsorption particles to reduce the suspended matter content; S3: the adsorbed water enters the electrocoagulation hydrocyclone reactor, and the electrochemical effect generated by the built-in iron-carbon micro-electrolysis filler realizes the deep removal of the organic matters in the water, the clear liquid generated by the electrocoagulation hydrocyclone reactor can be discharged near zero, the sludge generated in the electrocoagulation hydrocyclone reactor is returned to the micro-channel adsorber for treatment, and the bottom mud enters the buffer sedimentation tank.

2. The methanol to olefins water wash water near zero emission method according to claim 1, characterized in that, When the adsorption particles in the micro-channel adsorber run to the saturated state, the adsorption particles are backwashed and regenerated, the regenerated thick liquid enters the buffer sedimentation tank, and the tank bottom sludge is removed to the subsequent concentration unit after adjustment.

3. A device for near zero emission of methanol to olefins washing water, characterized in that, The device comprises a sewage stripping system, a micro-channel adsorber, an electrocoagulation hydrocyclone reactor and a buffer sedimentation tank, the outlet of the sewage stripping system is communicated with the inlet of the micro-channel adsorber, the outlet of the micro-channel adsorber is communicated with the inlet of the electrocoagulation hydrocyclone reactor, the electrocoagulation hydrocyclone reactor is further provided with a clear liquid outlet, a sludge outlet and a bottom mud outlet, the sludge outlet is communicated with the inlet of the micro-channel adsorber, and the bottom mud outlet is communicated with the inlet of the buffer sedimentation tank. The sewage stripping system comprises a sewage stripping tower, the sewage stripping tower is used for realizing the reverse heat exchange between the reboiling steam from bottom to top and the washing water from top to bottom, stripping most of the organic matters in the washing water to reduce the oil content; the micro-channel adsorber is built-in with a particle bed to further remove the organic matters in the water to reduce the suspended matter content; and the electrocoagulation hydrocyclone reactor is built-in with an iron-carbon micro-electrolysis filler to generate an electrochemical effect to realize the deep removal of the organic matters in the water.

4. The methanol to olefins scrubbing water near-zero emission device according to claim 3, characterized in that, The sewage stripping tower is of sieve plate structure, and the sewage stripping tower is further connected with at least one vertical thermosyphon reboiler, the outlet of the sewage stripping tower is respectively communicated with the inlet of the vertical thermosyphon reboiler and the inlet of the micro-channel adsorber, and the outlet of the vertical thermosyphon reboiler is communicated with the sewage stripping tower.

5. The methanol to olefins scrubbing water near-zero emission device according to claim 3, characterized in that, The particle bed is composed of carbon-based materials and high polymer materials with particle sizes of 0.5-1 mm, including anthracite, activated carbon, walnut shell and macroporous adsorption resin.

6. The methanol to olefins scrubbing water near-zero emission device according to claim 3, characterized in that, The micro-channel adsorber is provided with a water distributor below the particle bed, the backwashing water enters the particle bed through the uniformly arranged water distributor, one side of the micro-channel adsorber is further provided with a ring-shaped backwashing gas inlet pipe, a plurality of gas inlets are uniformly arranged on the inlet pipe, the backwashing gas is high-speed injected into the particle bed through the uniformly arranged gas inlets, so that the backwashing water and the backwashing gas are backwashed in the particle bed; The flow ratio of the backwashing water to the backwashing gas is 1:6, and the backwashing time is 50-60 minutes.

7. The methanol to olefins scrubbing water near-zero emission device according to claim 6, characterized in that, The micro-channel adsorber steam inlet pipe is further strengthened by pressurized backwashing gas to improve the surface energy of the adsorption particles in the bed.

8. The methanol to olefins scrubbing water near-zero emission device according to claim 6, characterized in that, The micro-channel adsorber is provided with a three-phase separator at the top, and the three-phase separator is provided with guide vanes; the three-phase separator is used for strengthening the desorption of pollutants on the surface of particles and in the channel by using the periodic oscillation centrifugal force generated by the self-rotation coupling motion of medium particles in the cyclone field during the regeneration process. The self-rotation speed of the medium particles is 2200-5400 revolutions per second, and the revolution speed is 10-15 meters per second.

9. The methanol to olefins scrubbing water near-zero emission device according to claim 3, characterized in that, The shell of the electrocoagulation cyclone reactor is provided with an anode conductive rod, a plurality of iron-carbon micro-electrolysis fillers are uniformly connected on the anode conductive rod through a supporting tray, and a cathode conductive sleeve is arranged outside the anode conductive rod in an interval mode; the inlet of the electrocoagulation cyclone reactor is located outside the cathode conductive sleeve. The particle size of the iron-carbon micro-electrolysis filler is 4-8 mm.

10. The methanol to olefins scrubbing water near-zero emission device according to claim 9, characterized in that, A plurality of groups of liquid-solid separators are arranged in parallel near the top of the shell of the electrocoagulation cyclone reactor, and the liquid and scum generated by electrocoagulation are efficiently separated by the different centrifugal forces caused by the density difference of components in the cyclone field.

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