CN111153469A - Recycling method and recycling system of quenching water in methanol-to-olefin process - Google Patents
Recycling method and recycling system of quenching water in methanol-to-olefin process Download PDFInfo
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
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- C—CHEMISTRY; METALLURGY
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
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- C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
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Abstract
The invention relates to a method for recycling quenching water in a methanol-to-olefin process, wherein the quenching water in the methanol-to-olefin process enters a first-stage membrane filter, the first-stage membrane filter separates the quenching water into filtrate and concentrated solution, the filtrate can be directly recycled to a quenching water tower, the water recycling rate after the treatment of the first-stage membrane filter is more than 90%, a membrane component of the first-stage membrane filter adopts a metal membrane, the concentrated solution enters a second-stage membrane filter for separation, the concentrated solution is separated into produced water and second-stage concentrated solution by the second-stage membrane filter, the produced water can be directly recycled to the quenching water tower, and the second-stage concentrated solution is discharged into a sludge treatment system. Compared with the prior art, the invention has high water recovery rate, can run at high temperature, backwashes on line and greatly improves the running stability of the system.
Description
Technical Field
The invention relates to a water treatment technology of a methanol-to-olefin process, in particular to a recycling method and a recycling system of quenching water in the methanol-to-olefin process.
Background
Mto (methanol to olefins) is a short term for a process of preparing olefins from methanol, and refers to a process of preparing low-carbon olefins (ethylene and propylene) from methanol by catalytic reaction. The reaction generally adopts a fluidized bed reactor, the produced product gas contains various impurities, the product gas (ethylene and propylene) is cleaned and primarily cooled by a quench tower and a water scrubber, and because the product gas contains residual catalyst and byproducts such as mixed alkane, aromatic hydrocarbon, coke and the like, the cleaned water needs to be filtered and cooled to remove suspended matters in the water and then returns to the production system for recycling.
The quenching water mainly washes the reaction gas, so that the main components of the impurities are similar to the components in the reaction gas. Meanwhile, because the fluidized bed reactor is adopted, the catalyst is easy to wear, the particle size of the normal catalyst is 70um, the worn catalyst is recovered through three-stage cyclone in the operation process, and fine powder with the particle size of 0-10um of the catalyst is difficult to separate and recover through cyclone and enters the quenching water. The reaction gas is subjected to heat removal in a quenching tower, and catalyst fine powder and generated acid gas are washed away. The solid content of a water system is increased due to the large loss of the catalyst, and the normal operation of a pump, a quench tower and a heat exchanger is directly influenced after the catalyst is mixed with byproducts such as mixed alkane, aromatic hydrocarbon, coke and the like, so that equipment needs to be cleaned regularly, and the production stability is influenced.
In order to ensure the stability of the water system, patent US6166282 discloses an MTO fluidized bed reactor, in which a set of cyclones is installed at the top of the reactor to reduce the loss of catalyst. US0234281 discloses a set of multiple solid-liquid cyclones or hydrocyclones operating in combination for recovering the catalyst. Patents CN101352621A and CN102093153A disclose a counter current washing and micro cyclone separator coupling device for recovering catalyst. Patent CN205031975U discloses an apparatus for purifying quench water and wash water using a metal sintered filter element. The invention has the defects of low filtration precision, incomplete separation of the catalyst and the organic by-products, low backwater quality, low water recovery rate and the like. Patent CN103951098A discloses an apparatus for treating quench water and wash water using a ceramic membrane in combination with a three-phase separator. The invention completely separates oil, water and catalyst, but the recovery rates of the oil, the water and the catalyst are all not high, and simultaneously, due to the characteristics of the ceramic membrane, the defects of high investment and operation cost, poor stability and the like exist in the practical application.
At present, the most important problem of quenching water treatment is to solve the problem of water recycling, and no proper technical scheme for solving the water recycling exists in the prior art.
Disclosure of Invention
The invention aims to provide a method and a system for recycling quenching water in a methanol-to-olefin process, so as to solve the problem of recycling water in the prior quenching water treatment.
The invention adopts a metal membrane system, can process the quenching water at high temperature on line, intensively solve the recycling problem of the quenching water, realizes more than 95 percent of water recovery rate through a secondary system, realizes high flux treatment under the high temperature condition, greatly reduces the investment cost, and simultaneously can ensure the stability of the system through on-line high-temperature backwashing and stable membrane surface flow velocity due to the special structure and material characteristics of the metal membrane.
The purpose of the invention can be realized by the following technical scheme:
the invention firstly discloses a method for recycling quenching water in a methanol-to-olefin process, which comprises the following steps:
quenching water in the methanol-to-olefin process enters a primary membrane filter, the primary membrane filter separates the quenching water into filtrate and concentrated solution, the filtrate can be directly recycled to a quenching water tower, the water recycling rate after the treatment of the primary membrane filter is more than 90%, a membrane component of the primary membrane filter adopts a metal membrane, the concentrated solution enters a secondary membrane filter for separation, the secondary membrane filter separates the concentrated solution into produced water and secondary concentrated solution, the produced water can be directly recycled to the quenching water tower, and the secondary concentrated solution is discharged into a sludge treatment system; under the process condition, the concentration of the primary membrane filter is more than 10 times, the water reuse rate is more than 90%, 10% of concentrated solution enters the secondary membrane filter, the water yield of the secondary membrane filter is more than 5% of the total water inflow of the quenching water, so that under the process, the total water reuse rate of the system is more than 95%, and the solid content in return water is less than 30 mg/L.
In one embodiment of the invention, the membrane component of the primary membrane filter is coated with TiO2The metal film of the layer, the filtration precision of the metal film is 20-100nm, and the diameter of the filtration channel is 11-19 mm.
In one embodiment of the present invention, the operating conditions of the primary membrane filter are:
the filtration temperature is preferably from 80 to 130 c, more preferably from 85 to 110 c,
the filtration mode adopts cross-flow filtration, the cross-flow rate is preferably 0.2-6m/s, more preferably 0.5-1.5m/s,
the transmembrane pressure difference is preferably from 0.1 to 1MPa, more preferably from 0.2 to 0.4 MPa.
In one embodiment of the invention, the method for recycling the quenching water in the methanol-to-olefin process also comprises a cleaning mode of a first-stage membrane filter in the operation process,
the cleaning operation conditions of the primary membrane filter are as follows:
selecting one or a combination of a plurality of cleaning modes of conventional chemical cleaning, filtrate backwashing, steam backwashing or steam flushing;
the conventional chemical cleaning can be carried out under the conditions of heating or normal temperature;
the backwashing pressure of the filtrate is preferably 0.1-1MPa, more preferably 0.2-0.4MPa, the backwashing period is preferably 20-120min, more preferably 30-60min, and the backwashing time is preferably 5-60s, more preferably 10-30 s;
the steam backwashing operation conditions are as follows: and (3) backwashing by adopting low-pressure steam, wherein the backwashing pressure is 1-6bar, the backwashing time is 1-10min, and the backwashing period is 20-120 min.
The steam flushing conditions were: introducing 1-10bar steam into the concentrated solution side of the filter, and washing for 1-60min for 1-24 hr.
In one embodiment of the invention, the water temperature of the quenching water in the methanol-to-olefin process is greater than 80 ℃, and the solid content is 150-700mg/L, and further 150-500 mg/L. The quenching water in the methanol-to-olefin process mainly contains a catalyst and a small amount of organic by-products. Wherein the catalyst powder is mainly present in the form of solid particles. The catalyst powder can be separated by a first-stage membrane filter, and the filtrate can be directly recycled.
In one embodiment of the invention, the operating conditions of the secondary membrane filter are:
the filtration temperature is preferably from 80 to 130 c, more preferably from 85 to 110 c,
the filtration mode adopts cross-flow filtration, the cross-flow rate is preferably 0.2-6m/s, more preferably 1.5-3m/s,
the transmembrane pressure difference is preferably from 0.1 to 1MPa, more preferably from 0.2 to 0.4 MPa.
In one embodiment of the invention, during the operation of the method for recycling the quenching water in the methanol-to-olefin process, the method further comprises the step of cleaning a secondary membrane filter, wherein the cleaning operation conditions of the secondary membrane filter are as follows:
selecting one or a combination of a plurality of cleaning modes of conventional chemical cleaning, filtrate backwashing, steam backwashing or steam flushing;
the conventional chemical cleaning can be carried out under the conditions of heating or normal temperature;
the backwashing pressure of the filtrate is preferably 0.1-1MPa, more preferably 0.2-0.4MPa, the backwashing period is preferably 20-120min, more preferably 30-60min, and the backwashing time is preferably 5-60s, more preferably 10-30 s;
the steam backwashing operation conditions are as follows: backwashing by using low-pressure steam, wherein the backwashing pressure is 1-6bar, the backwashing time is 1-10min, and the backwashing period is 20-120 min;
the steam flushing conditions were: introducing 1-10bar steam into the concentrated solution side of the filter, and washing for 1-60min for 1-24 hr.
In one embodiment of the invention, the concentrated solution enters the secondary membrane filter under the driving of a circulating pump of the secondary membrane filter.
In one embodiment of the invention, the membrane component of the two-stage membrane filter is coated with TiO2The metal film of the layer, the filtration precision of the metal film is 20-100nm, and the diameter of the filtration channel is 11-19 mm.
The invention also provides a recycling system of the quenching water in the methanol-to-olefin process, which comprises a primary membrane filter and a secondary membrane filter, wherein the primary membrane filter is used for receiving the quenching water in the methanol-to-olefin process and separating the quenching water into filtrate and concentrated solution, the filtrate can be directly recycled, the secondary membrane filter is connected with the primary membrane filter and is used for receiving the concentrated solution of the primary membrane filter and separating the concentrated solution into produced water and secondary concentrated solution, the produced water can be directly recycled, and the secondary concentrated solution is discharged into a sludge treatment system.
Further, still be provided with first order membrane filter charge pump before the first order membrane filter, first order membrane filter charge pump is connected with first order membrane filter for in with methyl alcohol system alkene technology quench water pump into first order membrane filter, still be connected with first order membrane filter circulating pump between first order membrane filter charge pump and the first order membrane filter, still be provided with second order membrane filter circulating pump between second order membrane filter and the first order membrane filter.
In one embodiment of the invention, the primary membrane filter is a metal membrane filter. The supporting layer of the membrane tube is made of metal, the metal comprises stainless steel, hastelloy and the like, and the surface coating is made of TiO2And (5) film layer. The filtering precision of the metal film is 20-100nm, and the diameter of the filtering channel is 11-19 mm.
In the metal membrane filter, membrane tubes are arranged in a cavity in a manner similar to a tube type heat exchanger, and each metal tube is independently welded to the flower plates at two ends to form a sealing manner different from other membrane components. The membrane tube wall thickness is <2 mm. The membrane assembly with the structure has the advantages that the flow of the filtrate from the membrane surface to the filtrate end is shorter, the deep pollution is reduced, and the backwashing effect is better. The membrane component made of all metal materials has a better temperature tolerance range and stronger temperature impact and mechanical impact resistance. Steam cleaning can be achieved. The material and the structure are the key for realizing steam cleaning and backwashing.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) the water recovery rate is high (> 95%), and the total discharge amount of pollutants and sewage is greatly reduced;
(2) the membrane module can run at high temperature and carry out online backwashing, and each membrane module is provided with an independent circulating pump, so that the flow velocity of the membrane surface is ensured, and the running stability of the system is greatly improved.
(3) The service life of the equipment is long, the flux is high, the system investment is low, and the economy is high;
(4) high filtering precision and high quality of reuse water.
Drawings
FIG. 1 is a schematic diagram showing the structure of a system for recycling quench water in a methanol-to-olefin process according to an embodiment;
FIG. 2 is a schematic cross-sectional view of a primary membrane filter;
FIG. 3 is a schematic view of a primary membrane filter configuration.
Detailed Description
Referring to fig. 1, a recycling system of quench water in a methanol-to-olefin process includes a first-stage membrane filter 3 and a second-stage membrane filter 4, wherein the first-stage membrane filter 3 is used for receiving quench water in the methanol-to-olefin process and separating the quench water into a filtrate and a concentrated solution, the filtrate can be directly recycled, the second-stage membrane filter 4 is connected with the first-stage membrane filter 3 and is used for receiving the concentrated solution of the first-stage membrane filter 3 and separating the concentrated solution into a product water and a second-stage concentrated solution, the product water can be directly recycled, and the second-stage concentrated solution is discharged into a sludge treatment system.
In this embodiment, a first-stage membrane filter feed pump 1 is further arranged in front of the first-stage membrane filter 3, the first-stage membrane filter feed pump 1 is connected with the first-stage membrane filter 3 and used for pumping chilled water into the first-stage membrane filter 3 in the process of preparing olefins from methanol, a first-stage membrane filter circulating pump 2 is further connected between the first-stage membrane filter feed pump 1 and the first-stage membrane filter 3, and a second-stage membrane filter circulating pump 5 is further arranged between the second-stage membrane filter 4 and the first-stage membrane filter 3.
Referring to fig. 1, a method for recycling quenching water in a methanol-to-olefin process includes the following steps:
quenching water in the methanol-to-olefin process enters a first-stage membrane filter 3, the first-stage membrane filter 3 separates the quenching water into filtrate and concentrated solution, the filtrate can be directly reused in a quenching water tower,
the concentrated solution enters a secondary membrane filter 4 for separation, the secondary membrane filter 4 separates the concentrated solution into produced water and secondary concentrated solution, the produced water can be directly recycled in a quenching water tower, and the secondary concentrated solution is discharged into a sludge treatment system; under the process condition, the concentration of the primary membrane filter 3 is more than 10 times, the water reuse rate is more than 90%, 10% of concentrated solution enters the secondary membrane filter 4, and the water yield of the secondary membrane filter 4 is more than 5% of the total water inflow of the quenching water, so that under the process, the total water reuse rate of the system is more than 95%, and the solid content in return water is less than 30 mg/L.
In this embodiment, the operating conditions of the primary membrane filter 3 are: the filtration temperature is preferably 80-130 ℃, more preferably 85-110 ℃, the filtration mode adopts cross-flow filtration, the cross-flow rate is preferably 0.2-6m/s, more preferably 0.5-1.5m/s, and the transmembrane pressure difference is preferably 0.1-1MPa, more preferably 0.2-0.4 MPa.
In this embodiment, the operating conditions of the secondary membrane filter 4 are: the filtration temperature is preferably 80-130 ℃, more preferably 85-110 ℃, the filtration mode adopts cross-flow filtration, the cross-flow rate is preferably 0.2-6m/s, more preferably 1.5-3m/s, and the transmembrane pressure difference is preferably 0.1-1MPa, more preferably 0.2-0.4 MPa.
In the embodiment, the operation process of the method for recycling the quenching water in the process of preparing the olefin from the methanol further comprises the cleaning of the first-stage membrane filter 3 and the second-stage membrane filter 4,
the cleaning operation conditions for the primary membrane filter 3 are as follows: conventional chemical cleaning, or filtrate backwashing, or steam cleaning, or steam backwashing, or a combination of cleaning means therein. The normal temperature or heating condition can be selected for the conventional chemical cleaning; the backwashing pressure of the filtrate is preferably 0.1-1MPa, more preferably 0.2-0.4MPa, the backwashing period is preferably 20-120min, more preferably 30-60min, and the backwashing time is preferably 5-60s, more preferably 10-30 s; the steam backwashing operation conditions are as follows: backwashing with low pressure steam at 1-6bar for 1-10min for 20-120 min; the steam flushing conditions were: introducing 1-10bar steam into the concentrated solution side of the filter, and washing for 1-60min for 1-24 hr.
The cleaning operation conditions for the secondary membrane filter 4 are as follows:
conventional chemical cleaning, or filtrate backwashing, or steam flushing, or steam backwashing, or a combination of cleaning means therein.
The conventional chemical cleaning can be carried out under the conditions of heating or normal temperature;
the backwashing pressure of the filtrate is preferably 0.1-1MPa, more preferably 0.2-0.4MPa, the backwashing period is preferably 20-120min, more preferably 30-60min, and the backwashing time is preferably 5-60s, more preferably 10-30 s;
the steam backwashing operation conditions are as follows: and (3) backwashing by adopting low-pressure steam, wherein the backwashing pressure is 1-6bar, the backwashing time is 1-10min, and the backwashing period is 20-120 min.
The steam flushing conditions were: introducing 1-10bar steam into the concentrated solution side of the filter, and washing for 1-60min for 1-24 hr.
In this embodiment, the concentrated solution enters the secondary membrane filter 4 under the driving of the circulating pump 5 of the secondary membrane filter under the process of separation in the secondary membrane filter 4.
In this embodiment, the membrane component of the secondary membrane filter 4 is coated with TiO2The metal film of the layer, the filtration precision of the metal film is 20-100nm, and the diameter of the filtration channel is 11-19 mm.
In the above embodiment, the primary membrane filter 3 is structured as shown in fig. 2 and 3, the membrane tubes are arranged in the cavity like a tubular heat exchanger, and each metal tube is individually welded to the flower plates at both ends. The membrane component adopts a structure that the surface is coated with TiO2The metal film of the layer, the filtration precision of the metal film is 20-100nm, and the diameter of the filtration channel is 11-19 mm. In the primary membrane filter 3, the membrane tubes are arranged in the cavity in a similar tube type heat exchanger way,each metal tube is individually welded to the face plates at both ends to form a seal different from the other membrane modules. Wall thickness of membrane tube<2mm, the supporting layer of the membrane tube is made of metal, the metal comprises stainless steel, hastelloy and the like, and the surface coating is made of TiO2And (5) film layer. The membrane assembly with the structure has the advantages that the flow of the filtrate from the membrane surface to the filtrate end is shorter, the deep pollution is reduced, and the backwashing effect is better. The temperature resistance range is better, and the temperature impact resistance and the mechanical impact resistance are stronger. Steam cleaning can be achieved.
In the above embodiment, the water temperature of the quenching water in the methanol-to-olefin process is greater than 80 ℃, and the solid content is 150-700 mg/L. The quenching water in the methanol-to-olefin process mainly contains a catalyst and a small amount of organic by-products. Wherein the catalyst powder is mainly present in the form of solid particles. The catalyst powder can be separated by a first-stage membrane filter, and the filtrate can be directly recycled.
The invention is described in detail below with reference to the figures and specific embodiments.
Example 1
As shown in the process flow of figure 1, quenching water with the water temperature of 80 ℃ and the solid content of 700 mg/L. Under the push of a feeding pump 1 of the primary membrane filter, the mixture enters a circulating pump 2 of the primary membrane filter and then is sent to the primary membrane filter 3, the aperture of a metal membrane in the primary membrane filter 3 is 100nm, and the mixture works under the conditions of transmembrane pressure difference of 1MPa, membrane surface flow rate of 0.2m/s and osmotic side back pressure of 0.2 MPa; the filtrate is directly returned to the quenching water tower for reuse. And periodically carrying out steam backwashing on the membrane, wherein the backwashing pressure is 6bar, the backwashing period is 60min, and the backwashing time is 5 min. The primary membrane filter 3 is concentrated by 10 times, the concentrated solution passes through a secondary membrane filter circulating pump 5 and then is sent into a secondary membrane filter 4, the aperture of a metal membrane of the secondary membrane filter 4 is 100nm, and the secondary membrane filter works under the conditions that transmembrane pressure difference is 1MPa, membrane surface flow rate is 2m/s, and back pressure on a permeation side is 0.2 MPa; the filtrate is directly returned to the quenching water tower for reuse. Periodically carrying out steam backwashing on the membrane, wherein the backwashing pressure is 5bar, the backwashing period is 60min, and the backwashing time is 5 min; the filtrate is backwashed at 2bar, the backwashing period is 120min, and the backwashing time is 30 s. The secondary membrane filter 4 is concentrated by 2 times, and the concentrated solution is sent to a sludge dewatering tower for treatment.
The quality of the filtrate, the recovery rate of each stage of water and the total recovery rate are as follows:
| ss content of filtrate | mg/L | 28 |
| Water recovery rate of first-stage membrane filter | ％ | 90 |
| Water recovery rate of secondary membrane filter | ％ | 50 |
| Total water recovery | ％ | 95 |
Example 2
As shown in the process flow of FIG. 1, the quenching water has a water temperature of 130 ℃ and a solid content of 210 mg/L. Under the push of a feeding pump 1 of the primary membrane filter, the mixture enters a circulating pump 2 of the primary membrane filter and then is sent to the primary membrane filter 3, the aperture of a metal membrane in the primary membrane filter 3 is 20nm, and the mixture works under the conditions that transmembrane pressure difference is 0.1MPa, membrane surface flow rate is 0.5m/s and permeation side backpressure is 0.1 MPa; the filtrate is directly returned to the quenching water tower for reuse. Periodically carrying out steam washing on the membrane, wherein the steam pressure is 0.6MPa, the washing period is 60min, and the washing time is 60 s; the filtrate backwashing pressure is 2bar, the backwashing period is 120min, and the backwashing time is 60 s. The primary membrane filter 3 is concentrated by 10 times, the concentrated solution passes through a secondary membrane filter circulating pump 5 and then is sent into a secondary membrane filter 4, the aperture of a metal membrane of the secondary membrane filter 4 is 20nm, and the secondary membrane filter works under the conditions that transmembrane pressure difference is 0.1MPa, membrane surface flow rate is 1.5m/s and permeation side backpressure is 0.1 MPa; the filtrate is directly returned to the quenching water tower for reuse. And (3) periodically carrying out steam washing on the membrane, wherein the steam pressure is 1MPa, the washing period is 60min, and the washing time is 60 s. The secondary membrane filter 4 is concentrated by 2.5 times, and the concentrated solution is sent to a sludge dewatering tower for treatment.
The quality of the filtrate, the recovery rate of each stage of water and the total recovery rate are as follows:
| ss content of filtrate | mg/L | 12 |
| Water recovery rate of first-stage membrane filter | ％ | 90 |
| Water recovery rate of secondary membrane filter | ％ | 60 |
| Total water recovery | ％ | 96 |
Example 3
As shown in the process flow of figure 1, quenching water with the water temperature of 85 ℃ and the solid content of 150 mg/L. Under the push of a feeding pump 1 of the primary membrane filter, the mixture enters a circulating pump 2 of the primary membrane filter and then is sent to the primary membrane filter 3, the aperture of a metal membrane in the primary membrane filter 3 is 20nm, and the mixture works under the conditions that transmembrane pressure difference is 0.4MPa, membrane surface flow rate is 0.5m/s and permeation side backpressure is 0.2 MPa; the filtrate is directly returned to the quenching water tower for reuse. Periodically backwashing the membrane with filtrate, wherein the backwashing pressure is 0.4MPa, the backwashing period is 30min, and the backwashing time is 10 s; steam backwash pressure 1bar, backwash time 10min, backwash period 120 min. The primary membrane filter 3 is concentrated by 10 times, the concentrated solution passes through a secondary membrane filter circulating pump 5 and then is sent into a secondary membrane filter 4, the aperture of a metal membrane of the secondary membrane filter 4 is 100nm, and the secondary membrane filter works under the conditions that transmembrane pressure difference is 0.5MPa, membrane surface flow rate is 6m/s and permeation side backpressure is 0.1 MPa; the filtrate is directly returned to the quenching water tower for reuse. Periodically backwashing the membrane with filtrate, wherein the backwashing pressure is 1MPa, the backwashing period is 30min, and the backwashing time is 10 s; steam washing pressure 6bar, washing period 24 hours, washing time 30 min. The secondary membrane filter 4 is concentrated by 2 times, and the concentrated solution is sent to a sludge dewatering tower for treatment. And chemically cleaning the primary and secondary membrane filters by using a chemical cleaning agent every 6-8 hours of operation.
The quality of the filtrate, the recovery rate of each stage of water and the total recovery rate are as follows:
| ss content of filtrate | mg/L | 13 |
| Water recovery rate of first-stage membrane filter | ％ | 90 |
| Water recovery rate of secondary membrane filter | ％ | 50 |
| Total water recovery | ％ | 95 |
Example 4
As shown in the process flow of FIG. 1, the quenching water has the water temperature of 110 ℃ and the solid content of 500 mg/L. Under the push of a feeding pump 1 of the primary membrane filter, the mixture enters a circulating pump 2 of the primary membrane filter and then is sent to the primary membrane filter 3, the aperture of a metal membrane in the primary membrane filter 3 is 100nm, and the mixture works under the conditions that transmembrane pressure difference is 0.2MPa, the flow rate of the membrane surface is 1.5m/s, and the back pressure of a permeation side is 0.3 MPa; the filtrate is directly returned to the quenching water tower for reuse. Periodically backwashing the membrane with filtrate, wherein the backwashing pressure is 0.3MPa, the backwashing period is 60min, and the backwashing time is 30 s; steam backwashing pressure is 3bar, backwashing time is 1min, and backwashing period is 20 min; steam washing pressure is 1bar, washing time is 10min, and backwashing period is 120 min. The primary membrane filter 3 is concentrated by 10 times, the concentrated solution passes through a secondary membrane filter circulating pump 5 and then is sent into a secondary membrane filter 4, the aperture of a metal membrane of the secondary membrane filter 4 is 100nm, and the secondary membrane filter works under the conditions that transmembrane pressure difference is 0.4MPa, membrane surface flow rate is 3m/s and permeation side backpressure is 0.3 MPa; the filtrate is directly returned to the quenching water tower for reuse. Periodically backwashing the membrane with filtrate, wherein the backwashing pressure is 0.1MPa, the backwashing period is 60min, and the backwashing time is 60 s; the steam back-flushing pressure is 6bar, the flushing period is 20min, and the flushing time is 1 min. The secondary membrane filter 4 is concentrated by 2 times, and the concentrated solution is sent to a sludge dewatering tower for treatment. The quality of the filtrate, the recovery rate of each stage of water and the total recovery rate are as follows:
| ss content of filtrate | mg/L | 25 |
| Water recovery rate of first-stage membrane filter | ％ | 90 |
| Water recovery rate of secondary membrane filter | ％ | 50 |
| Total water recovery | ％ | 95 |
Example 5
As shown in the process flow of figure 1, quenching water with the water temperature of 90 ℃ and the solid content of 300 mg/L. Under the push of a feeding pump 1 of the primary membrane filter, the mixture enters a circulating pump 2 of the primary membrane filter and then is sent to the primary membrane filter 3, the aperture of a metal membrane in the primary membrane filter 3 is 100nm, and the mixture works under the conditions that transmembrane pressure difference is 0.3MPa, membrane surface flow rate is 6m/s and permeation side backpressure is 0.1 MPa; the filtrate is directly returned to the quenching water tower for reuse. Filtrate backwashing is periodically carried out on the membrane, the backwashing pressure is 0.6MPa, the backwashing period is 20min, and the backwashing time is 20 s; steam flushing pressure 10bar, flushing time 60min, flushing period 24 hours. The primary membrane filter 3 is concentrated by 10 times, the concentrated solution passes through a secondary membrane filter circulating pump 5 and then is sent into a secondary membrane filter 4, the aperture of a metal membrane of the secondary membrane filter 4 is 20nm, and the secondary membrane filter works under the conditions that transmembrane pressure difference is 0.3MPa, membrane surface flow rate is 2.5m/s and permeation side backpressure is 0.2 MPa; the filtrate is directly returned to the quenching water tower for reuse. Periodically backwashing the membrane with filtrate, wherein the backwashing pressure is 0.4MPa, the backwashing period is 50min, and the backwashing time is 20 s; steam backwashing pressure is 1bar, backwashing time is 10min, and backwashing period is 120 min; steam flushing pressure 1bar, flushing period 12 hours, flushing time 60 min. The secondary membrane filter 4 is concentrated by 2 times, and the concentrated solution is sent to a sludge dewatering tower for treatment.
The quality of the filtrate, the recovery rate of each stage of water and the total recovery rate are as follows:
| ss content of filtrate | mg/L | 15 |
| Water recovery rate of first-stage membrane filter | ％ | 90 |
| Water recovery rate of secondary membrane filter | ％ | 50 |
| Total water recovery | ％ | 95 |
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (9)
1. A method for recycling quenching water in a process for preparing olefin from methanol, which is characterized in that,
quenching water in the methanol-to-olefin process enters a first-stage membrane filter (3), the first-stage membrane filter (3) separates the quenching water into filtrate and concentrated solution, the filtrate can be directly reused in a quenching water tower, the water reuse rate after being treated by the first-stage membrane filter (3) is more than 90%, a membrane component of the first-stage membrane filter (3) adopts a metal membrane,
the concentrated solution enters a secondary membrane filter (4) for separation, the concentrated solution is separated into produced water and secondary concentrated solution by the secondary membrane filter (4), the produced water can be directly recycled in a quenching water tower, and the secondary concentrated solution is discharged into a sludge treatment system; the secondary membrane filter (4) further recovers water with a volume of the concentrated solution of more than 50%.
2. The recycling method of quenching water in methanol to olefin process according to claim 1, wherein the membrane module of the primary membrane filter (3) is coated with TiO2The metal film of the layer, the filtration precision of the metal film is 20-100nm, and the diameter of the filtration channel is 11-19 mm.
3. The method for recycling quenching water in the methanol-to-olefin process according to claim 1, wherein the operating conditions of the primary membrane filter (3) are as follows:
the filtration temperature is preferably from 80 to 130 c, more preferably from 85 to 110 c,
the filtration mode adopts cross-flow filtration, the cross-flow rate is preferably 0.2-6m/s, more preferably 0.5-1.5m/s,
the transmembrane pressure difference is preferably from 0.1 to 1MPa, more preferably from 0.2 to 0.4 MPa.
4. The recycling method of quenching water in the methanol to olefin process according to claim 1, wherein the recycling method of quenching water in the methanol to olefin process further comprises cleaning the first-stage membrane filter (3),
the cleaning operation conditions of the primary membrane filter (3) are as follows:
selecting one or a combination of a plurality of cleaning modes of conventional chemical cleaning, filtrate backwashing, steam backwashing or steam flushing;
the conventional chemical cleaning can be carried out under the conditions of heating or normal temperature;
the backwashing pressure of the filtrate is preferably 0.1-1MPa, more preferably 0.2-0.4MPa, the backwashing period is preferably 20-120min, more preferably 30-60min, and the backwashing time is preferably 5-60s, more preferably 10-30 s;
the steam backwashing operation conditions are as follows: and (3) backwashing by adopting low-pressure steam, wherein the backwashing pressure is 1-6bar, the backwashing time is 1-10min, and the backwashing period is 20-120 min.
The operating conditions of the steam flush were: flushing with low pressure steam at 1-10bar for 1-60min for 1-24 hr.
5. The method for recycling quenching water in the methanol-to-olefin process according to claim 1, wherein the operating conditions of the secondary membrane filter (4) are as follows:
the filtration temperature is preferably from 80 to 130 c, more preferably from 85 to 110 c,
the filtration mode adopts cross-flow filtration, the cross-flow rate is preferably 0.2-6m/s, more preferably 1.5-3m/s,
the transmembrane pressure difference is preferably from 0.1 to 1MPa, more preferably from 0.2 to 0.4 MPa.
6. The method for recycling quenching water in the methanol-to-olefin process according to claim 1, wherein the method for recycling quenching water in the methanol-to-olefin process further comprises cleaning the secondary membrane filter (4), and the cleaning conditions of the secondary membrane filter (4) are as follows:
selecting one or a combination of a plurality of cleaning modes of conventional chemical cleaning, filtrate backwashing, steam backwashing or steam flushing;
the conventional chemical cleaning can be carried out under the conditions of heating or normal temperature;
the backwashing pressure of the filtrate is preferably 0.1-1MPa, more preferably 0.2-0.4MPa, the backwashing period is preferably 20-120min, more preferably 30-60min, and the backwashing time is preferably 5-60s, more preferably 30-60 s;
the steam backwashing operation conditions are as follows: backwashing by using low-pressure steam, wherein the backwashing pressure is 1-6bar, the backwashing time is 1-10min, and the backwashing period is 20-120 min;
the operating conditions of the steam flush were: flushing with low pressure steam at 1-10bar for 1-60min for 1-24 hr.
7. The method of claim 1The method for recycling the quenching water in the process of preparing the olefin from the methanol is characterized in that a membrane component of the secondary membrane filter (4) adopts a membrane component with a surface plated with TiO2The metal film of the layer, the filtration precision of the metal film is 20-100nm, and the diameter of the filtration channel is 11-19 mm.
8. The recycling system of the quenching water in the methanol-to-olefin process is characterized by comprising a primary membrane filter (3) and a secondary membrane filter (4), wherein the primary membrane filter (3) is used for receiving the quenching water in the methanol-to-olefin process and separating the quenching water into filtrate and concentrated solution, the filtrate can be directly recycled, the secondary membrane filter (4) is connected with the primary membrane filter (3) and used for receiving the concentrated solution of the primary membrane filter (3) and separating the concentrated solution into produced water and secondary concentrated solution, the produced water can be directly recycled, and the secondary concentrated solution is discharged into a sludge treatment system.
9. The recycling system of quench water in the methanol-to-olefin process according to claim 8, wherein a primary membrane filter feed pump (1) is further disposed in front of the primary membrane filter (3), the primary membrane filter feed pump (1) is connected to the primary membrane filter (3) and is used for pumping the quench water in the methanol-to-olefin process into the primary membrane filter (3), a primary membrane filter circulating pump (2) is further connected between the primary membrane filter feed pump (1) and the primary membrane filter (3), and a secondary membrane filter circulating pump (5) is further disposed between the secondary membrane filter (4) and the primary membrane filter (3).
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