Method for recovering organic substances from epichlorohydrin wastewater

Abstract

The present application relates to the field of epichlorohydrin wastewater treatment, and discloses a method for recovering organic matter from epichlorohydrin wastewater. The method comprises the following steps: introducing the epichlorohydrin wastewater into a pretreater for neutralization treatment to obtain neutralized wastewater, wherein the pH of the neutralized wastewater is 5-10; introducing the neutralized wastewater into a dehydration concentration tower, and using the overhead pressurized gas phase as a heat source of the dehydration concentration tower to perform dehydration evaporation treatment on the neutralized wastewater to obtain concentrated wastewater; introducing the concentrated wastewater into a deheavy evaporator for deheavy evaporation treatment to obtain salt-containing waste liquid and deheavy evaporator gas phase; introducing the deheavy evaporator gas phase into a dehydration tower for dehydration treatment to obtain organic matter containing glycerol monomethyl ether and glycerol and effluent wastewater; and introducing the organic matter containing glycerol monomethyl ether and glycerol into a product tower for separation treatment to obtain glycerol monomethyl ether and glycerol. The method can realize the recovery of organic matter in epichlorohydrin wastewater, and obtain glycerol monomethyl ether and glycerol.

Description

Technical Field

[0001] This invention relates to the technical field of epichlorohydrin wastewater treatment, and specifically to a method for recovering organic matter from epichlorohydrin wastewater. Background Technology

[0002] Epichlorohydrin (ECH) is an important organic chemical raw material and intermediate, mainly used in the production of epoxy resins and chlorohydrin rubbers. It can also be used as a solvent, plasticizer, flame retardant, and surfactant. In recent years, the rapid growth in demand for epoxy resins has promoted the development of ECH.

[0003] The hydrogen peroxide-based epichlorohydrin (HPECH) technology, which involves a one-step reaction of allyl chloride and hydrogen peroxide, is characterized by mild reaction conditions, high selectivity, and low emissions of waste gas, wastewater, and solid waste. It is listed in the "Petrochemical Green and Low-Carbon Process Directory" and is a green and low-carbon technology encouraged by the state. However, due to water introduced into the hydrogen peroxide, water generated during the reaction, and the need for water in the process flow, the HPECH unit produces large volumes of wastewater with high COD, high salinity, and poor biodegradability. The proper treatment of this wastewater will constrain the development of HPECH technology.

[0004] The HPECH apparatus exhibits the following side reactions:

[0005] (1) ECH reacts with methanol to produce 3-chloro-1-methoxy-2-propanol.

[0006] (2) ECH reacts with water to produce 3-chloro-1,2-propanediol.

[0007] (3) 3-Chloro-1-methoxy-2-propanol reacts with water to produce glycerol monomethyl ether and HCl.

[0008] (4) 3-Chloro-1,2-propanediol reacts with water to produce glycerol and HCl.

[0009] Patent application 201911065046.0 discloses a method for treating epichlorohydrin wastewater, including processes such as stripping, reactive extraction, distillation, and hydrolysis distillation, which can effectively recover monochloropropanediol from the wastewater. This invention uses reactive extraction to reduce energy consumption, and the extractant and reactant can be recycled during the extraction reaction, achieving resource utilization and enhancing economic efficiency.

[0010] Patent application 202011151835.9 discloses an apparatus for separating and purifying byproducts from epichlorohydrin wastewater. The apparatus includes an extraction unit, a dehydration unit, a solvent recovery unit, and a distillation unit connected in sequence. The apparatus also includes an azeotropic unit, a membrane concentration unit, and an evaporation unit connected in sequence to the extraction unit. By combining extraction, distillation, membrane concentration, and evaporation, a series of processes can be combined to effectively separate, purify, and recycle byproducts from epichlorohydrin wastewater. The method using this apparatus can effectively separate water and organic matter, and achieve the recovery, separation, and purification of chloroethanol ethers and monochloropropanediol in the wastewater, resulting in effluent that meets discharge standards and has broad application prospects.

[0011] The organic matter content in epichlorohydrin wastewater is typically below 5%, meaning that over 95% of the water needs to be evaporated, resulting in high energy consumption for the equipment. Direct biochemical treatment would result in a COD of 50,000-100,000 mg / L and a biodegradability (B / C) ratio of <0.1, classifying it as difficult to treat biochemically. Recovering high-value organic matter before biochemical treatment improves the economics of the equipment and reduces the difficulty of subsequent wastewater treatment. The aforementioned patent applications employ different methods to recover chlorohydrin ethers and monochloropropanediol, but these processes are lengthy and energy-intensive. Glycerol monomethyl ether and glycerol have high boiling points and are thermosensitive, easily decomposing under heat and leading to decreased recovery rates. During the continuous concentration process, salt precipitation can cause equipment and pipeline blockages, requiring shutdowns for maintenance and preventing long-term continuous operation of the equipment. Summary of the Invention

[0012] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for recovering organic matter from epichlorohydrin wastewater. This method can recover organic matter from epichlorohydrin wastewater to obtain the target products glycerol monomethyl ether and glycerol.

[0013] To achieve the above objectives, the present invention provides a method for recovering organic matter from epichlorohydrin wastewater, wherein the method includes the following steps:

[0014] (1) Epichlorohydrin wastewater is introduced into a pre-processor for neutralization treatment to obtain neutralized wastewater with a pH of 5-10.

[0015] (2) The neutralized wastewater is introduced into a dehydration and concentration tower, and the pressurized gas phase at the top of the dehydration and concentration tower is used as the heat source of the dehydration and concentration tower to dehydrate and evaporate the neutralized wastewater to obtain concentrated wastewater.

[0016] (3) The concentrated wastewater is introduced into a de-weighting evaporator for de-weighting evaporation treatment to obtain a salt-containing waste liquid and a de-weighting evaporator gas phase;

[0017] (4) The gas phase of the de-oiling evaporator is introduced into the dehydration tower for dehydration treatment to obtain organic matter containing glycerol monomethyl ether and glycerol, as well as wastewater discharged externally.

[0018] (5) The organic compound containing glycerol monomethyl ether and glycerol is introduced into the product tower for separation treatment to obtain glycerol monomethyl ether and glycerol.

[0019] The method provided by this invention has the following advantages:

[0020] (1) Neutralizing epichlorohydrin wastewater can significantly delay or prevent equipment corrosion.

[0021] (2) Pressurized gas phase is adopted, preferably steam mechanical recompression, to reuse the latent heat of steam at the top of the dehydration concentration tower, which greatly reduces the energy consumption of the dehydration concentration tower.

[0022] (3) The concentrated wastewater enters the de-weighting evaporator, and the salt is controlled to precipitate in the de-weighting evaporator instead of in the reboiler. In the preferred case, the de-weighting evaporator is equipped with a backup unit to ensure long-term continuous operation of the device.

[0023] (4) In the preferred case, the conditions of dehydration and separation are controlled so that glycerol monomethyl ether and glycerol do not decompose, thereby improving their recovery rate.

[0024] (5) It has a more significant low-carbon and green effect, saves more than 85% energy compared to direct steam heating, and has a simple start-up process. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the present invention.

[0026] Explanation of reference numerals in the attached figures

[0027] Figure 1 middle:

[0028] A - Static mixer; B - Buffer tank;

[0029] C - Dehydration and concentration tower; D - Compressor;

[0030] E - Reboiler of the concentration tower; F - Reflux tank of the concentration tower;

[0031] G - Concentrator reflux pump; H - Concentrator bottom pump;

[0032] I - De-weighting evaporator; J - Dehydration tower;

[0033] K-Product tower; 101-Epoxychloropropane wastewater;

[0034] 102-Alkaline compounds; 103-Neutralize wastewater;

[0035] 104 - Top gas phase of the concentration column; 105 - Pressurized gas phase at the top of the column;

[0036] 106 - Condensate from the overhead gas of the concentration tower; 107 - Liquid phase in the reflux tank of the concentration tower;

[0037] 108 - Reflux liquid from the concentration tower; 109 - Discharged wastewater;

[0038] 110 - Concentrated wastewater; 111 - Material inlet to the reboiler of the concentration tower;

[0039] 112 - Material outlet from the reboiler of the concentration tower; 113 - Concentrated wastewater to be treated;

[0040] 114 - Vapor phase from the de-weighing evaporator; 115 - Salt-containing waste liquid;

[0041] 116 - Wastewater discharged externally; 117 - Organic matter containing glycerol monomethyl ether and glycerol; 118-Propanetriol monomethyl ether; 119-Propanetriol. Detailed Implementation

[0042] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0044] Unless otherwise specified, all pressures in this invention are absolute pressures.

[0045] This invention provides a method for recovering organic matter from epichlorohydrin wastewater, wherein the method includes the following steps:

[0046] (1) Epichlorohydrin wastewater 101 is introduced into a preprocessor for neutralization treatment to obtain neutralized wastewater 103, wherein the pH of neutralized wastewater 103 is 5-10;

[0047] (2) The neutralized wastewater 103 is introduced into the dehydration and concentration tower C. The pressurized gas phase 105 at the top of the dehydration and concentration tower C is used as the heat source of the dehydration and concentration tower C to dehydrate and evaporate the neutralized wastewater 103 to obtain concentrated wastewater 110.

[0048] (3) The concentrated wastewater 110 is introduced into the de-weighting evaporator I for de-weighting evaporation treatment to obtain salt-containing waste liquid 115 and de-weighting evaporator gas phase 114.

[0049] (4) The gas phase 114 of the de-weighting evaporator is introduced into the dehydration tower J for dehydration treatment to obtain organic matter 117 containing glycerol monomethyl ether and glycerol and wastewater 116.

[0050] (5) The organic compound 117 containing glycerol monomethyl ether and glycerol is introduced into product tower K for separation treatment to obtain glycerol monomethyl ether 118 and glycerol 119.

[0051] The method provided by this invention neutralizes epichlorohydrin wastewater, which can significantly delay or prevent equipment corrosion. By using a pressurized gas phase, preferably steam mechanical recompression, the latent heat of the steam at the top of the dehydration concentration tower is reused, which greatly reduces the energy consumption of the dehydration concentration tower. The concentrated wastewater enters the de-weighting evaporator, which controls the precipitation of salt in the de-weighting evaporator instead of in the reboiler.

[0052] In this invention, the source of epichlorohydrin wastewater is not particularly limited. For example, it can come from a propylene high-temperature chlorination plant, a glycerol plant, a chloropropylene hydrogen peroxide plant, or a chlorohydrin plant.

[0053] In this invention, preferably, the epichlorohydrin wastewater 101 contains 3-chloro-1-methoxy-2-propanol and 3-chloro-1,2-propanediol.

[0054] In this invention, preferably, based on the total weight of the epichlorohydrin wastewater 101, the content of 3-chloro-1-methoxy-2-propanol is 0.01%-10%, and the content of 3-chloro-1,2-propanediol is 0.01%-10%. This invention treats epichlorohydrin wastewater with specific components and contents, exhibiting more significant low-carbon and green effects, saving over 85% energy compared to direct steam heating, and offering advantages such as a simple start-up process.

[0055] In this invention, preferably, the epichlorohydrin wastewater also optionally contains light impurities and heavy impurities. In this invention, there are no particular limitations on the types and amounts of light and heavy impurities.

[0056] In this invention, preferably, in step (1), the neutralization treatment is carried out in the presence of an alkaline compound 102, and preferably the alkaline compound 102 is selected from at least one of sodium hydroxide, sodium oxide, potassium hydroxide, potassium oxide, calcium hydroxide, calcium oxide, barium hydroxide, barium oxide, and ammonia.

[0057] In this invention, the conditions for neutralization are not particularly limited, as long as the required pH is met. Preferably, in step (1), the conditions for neutralization include: an operating pressure of 100-4000 kPa, an operating temperature of 100-250°C, and a residence time of 1 min-10 h. Through neutralization, the conversion of 3-chloro-1-methoxy-2-propanol and 3-chloro-1,2-propanediol in epichlorohydrin wastewater is achieved, yielding glycerol monomethyl ether and its corresponding salt, as well as glycerol and its corresponding salt.

[0058] In this invention, preferably, in step (1), the pH of the neutralized wastewater 103 is 7-9. The advantage of this preferred embodiment is reduced equipment corrosion and lower material requirements.

[0059] In this invention, preferably, the preprocessor includes a static mixer A and a buffer tank B, wherein the static mixer A and the buffer tank B are connected in series.

[0060] In this invention, the conditions for dehydration evaporation are not particularly limited. Preferably, in step (2), the conditions for dehydration evaporation include: a reflux ratio of 0.01-20, a column top pressure of 5-4000 kPa, and a column top temperature of 30-250°C.

[0061] In this invention, the type of dehydration concentration tower is not particularly limited, as long as it can achieve the purpose of neutralizing and concentrating wastewater. Preferably, in step (2), the dehydration concentration tower C is a flash evaporator and / or a distillation tower.

[0062] In this invention, preferably, step (2) further includes: using compressor D to pressurize the gas phase at the top of the dehydration and concentration tower C to obtain the pressurized gas phase 105 at the top of the tower. By installing a compressor at the top of the dehydration and concentration tower C, the gas phase at the top of the tower is compressed by steam mechanical pressurization, resulting in the pressurized gas phase 105 at the top of the tower.

[0063] In this invention, preferably, the ratio of the inlet pressure to the outlet pressure of the compressor D is 1.05-10:1, more preferably 1.2-7:1.

[0064] In this invention, preferably, the temperature of the pressurized gas phase 105 at the top of the tower is at least 5°C higher than the temperature of the bottom of the dehydration and concentration tower C, and more preferably 8-50°C higher. The pressurized gas phase serves as the heat source for the reboiler of the dehydration and concentration tower C, providing the necessary heat for the concentration of neutralized wastewater, thus achieving the concentration of neutralized wastewater and possessing significant engineering value.

[0065] In this invention, preferably, the bottom section of the dehydration and concentration tower C is provided with a concentration tower reboiler E connected to the bottom section.

[0066] In this invention, the type of reboiler for the concentration tower is not particularly limited. Preferably, the reboiler for the concentration tower is at least one of a falling film reboiler, a rising film reboiler, a forced circulation reboiler, and a thermosiphon reboiler.

[0067] In this invention, preferably, step (2) further includes: after the pressurized gas phase 105 is condensed, a dehydration and concentration tower reflux liquid 108 and a discharged wastewater 109 are obtained.

[0068] In this invention, by performing de-weighting evaporation treatment in a de-weighting evaporator, most of the water, glycerol monomethyl ether, and glycerol are vaporized and enter the dehydration tower. The remaining non-vaporizable saline waste liquid includes a small amount of water, glycerol monomethyl ether, glycerol, salt, and heavy impurities. This invention does not particularly limit the conditions for the de-weighting evaporation treatment. Preferably, in step (3), the conditions for the de-weighting evaporation treatment include: an operating pressure of 1-200 kPa and an operating temperature of 20-300 °C; preferably, in step (3), the conditions for the de-weighting evaporation treatment include: an operating pressure of 5-100 kPa and an operating temperature of 50-160 °C.

[0069] In this invention, preferably, one or more de-oiling evaporators are provided; further, the de-oiling evaporators are configured with one in operation and one in standby. By setting up one in operation and one in standby de-oiling evaporator, when the salt continuously increases and affects the normal operation of the de-oiling evaporator, it can be switched to another evaporator for continued use, and the de-oiling evaporator that is replaced can be cleaned and reused.

[0070] In this invention, water in the gas phase to be treated is separated by dehydration treatment in a dehydration tower. Wastewater is obtained at the top of the tower, and organic matter containing glycerol monomethyl ether and glycerol is obtained at the bottom of the tower.

[0071] In this invention, the conditions for dehydration treatment are not particularly limited. Preferably, in step (4), the conditions for dehydration treatment include: a reflux ratio of 0.01-20 for dehydration tower J, a top pressure of 1-300 kPa, and a top temperature of 7-135°C. More preferably, the conditions for dehydration treatment include: a reflux ratio of 0.1-5 for dehydration tower J, a top pressure of 12-90 kPa, and a top temperature of 50-95°C. By adopting negative pressure operating conditions, the decomposition of glycerol monomethyl ether and glycerol can be reduced.

[0072] In this invention, glycerol monomethyl ether is obtained at the top of the product tower and glycerol is obtained at the bottom of the tower through separation treatment.

[0073] In this invention, the conditions for separation are not particularly limited. Preferably, in step (5), the conditions for separation include: a reflux ratio of 0.01-20 for product column K, a top pressure of 1-100 kPa, and a top temperature of 105-220°C. More preferably, the conditions for separation include: a reflux ratio of 0.1-5 for product column K, a top pressure of 3-60 kPa, and a top temperature of 125-200°C. By using negative pressure operating conditions, the decomposition of glycerol monomethyl ether and glycerol can be reduced, and the recovery rates of glycerol monomethyl ether and glycerol can be improved.

[0074] The present invention will be described in detail below through embodiments.

[0075] Energy consumption calculations are performed in accordance with GB / T 50441-2016 Petrochemical Design Energy Consumption Calculation Standard.

[0076] Energy saving ratio = 1 - compressor energy consumption / reboiler energy consumption when steam is used as a heat source.

[0077] Glycerol monomethyl ether recovery rate (%) = Glycerol monomethyl ether mass flow rate / (Glycerol monomethyl ether content in wastewater * wastewater mass flow rate) * 100%.

[0078] Glycerol recovery rate (%) = Glycerol mass flow rate / (Glycerol content in wastewater * wastewater mass flow rate) * 100%.

[0079] The following embodiments are as follows Figure 1 The schematic diagram illustrates a method for recovering organic matter from epichlorohydrin wastewater, wherein the method includes the following steps:

[0080] (1) Epichlorohydrin wastewater 101 and alkaline compound 102 are sequentially introduced into static mixer A and buffer tank B for neutralization treatment to obtain neutralized wastewater 103.

[0081] (2) The neutralized wastewater 103 is introduced into the dehydration and concentration tower C. The top of the dehydration and concentration tower C is equipped with a compressor D, and the bottom part of the tower is equipped with a concentration tower reboiler E connected to the bottom of the tower. The compressor D is used to pressurize the top gas phase 104 of the dehydration and concentration tower to obtain the top pressurized gas phase 105. The top pressurized gas phase 105 serves as the heat source for the concentration tower reboiler E of the dehydration and concentration tower C to dehydrate and evaporate the neutralized wastewater 103 to obtain concentrated wastewater 110.

[0082] The outlet of the reboiler E of the thickener is connected to the thickener reflux tank F, and the outlet of the thickener reflux tank F is connected to the thickener reflux pump G. The pressurized gas phase 105 at the top of the thickener is condensed by the thickener reboiler E to obtain the thickener overhead gas condensate 106. The thickener overhead gas condensate 106 enters the thickener reflux tank F for reflux to obtain the thickener reflux tank liquid phase 107. The thickener reflux tank liquid phase 107 is transported by the thickener reflux pump G. Part of the thickener reflux liquid 108 is refluxed, and the other part is discharged as wastewater 109.

[0083] (3) A concentrator pump H is connected between the dehydration and concentration tower C and the de-weight evaporator I. The concentrated wastewater 110 is transported by the concentrator pump H. A portion of the concentrated wastewater 110 is used as the inlet material 111 of the concentrator reboiler and is vaporized by the pressurized gas phase 105 at the top of the concentrator reboiler E. The outlet material 112 of the concentrator reboiler returns to the dehydration and concentration tower C.

[0084] Another portion of the concentrated wastewater 110 to be treated, concentrated wastewater 113, is introduced into the de-weighting evaporator I for de-weighting evaporation treatment to obtain salt-containing waste liquid 115 and de-weighting evaporator gas phase 114.

[0085] (4) The gas phase 114 of the de-weighting evaporator is introduced into the dehydration tower J for dehydration treatment to obtain organic matter 117 containing glycerol monomethyl ether and glycerol and wastewater 116.

[0086] (5) The organic compound 117 containing glycerol monomethyl ether and glycerol is introduced into product tower K for separation treatment to obtain glycerol monomethyl ether 118 and glycerol 119.

[0087] Example 1

[0088] Epichlorohydrin wastewater 101 from the epichlorohydrin unit mainly contains light impurities, water, 3-chloro-1-methoxy-2-propanol (2% by mass), 3-chloro-1,2-propanediol (1% by mass), heavy impurities, epichlorohydrin, etc. It is mixed with alkaline compound 102 (NaOH) in static mixer A, and then held in buffer tank B. 3-chloro-1-methoxy-2-propanol reacts with the alkali to convert into glycerol monomethyl ether and its salt, and 3-chloro-1,2-propanediol reacts with the alkali to convert into glycerol and its salt, resulting in neutralized wastewater 103 containing the aforementioned organic matter and salt. Neutralized wastewater 103 enters dehydration and concentration tower C, specifically:

[0089] The operating pressure of buffer tank B is 200 kPa, the operating temperature is 120℃, the residence time is 35 min, and the pH of the neutralized wastewater 103 is 7.

[0090] The reflux ratio of the dehydration and concentration tower C is 0.1, the pressure at the top of the tower is 150 kPa, and the temperature at the top of the tower is 111℃.

[0091] The compressor D has an inlet-outlet pressure ratio of 2.5 and an outlet temperature of 127℃, which is 21℃ higher than the bottom temperature of the tower.

[0092] The de-weighted evaporator I operates in a one-on-one standby mode, with an operating pressure of 25 kPa and an operating temperature of 134℃.

[0093] The reflux ratio of dehydration tower J is 1, the pressure at the top of the tower is 15 kPa, and the temperature at the top of the tower is 54℃.

[0094] The product column K has a reflux ratio of 2, a top pressure of 7 kPa, and a top temperature of 147℃.

[0095] Experiments were conducted using the above process conditions. In Example 1 compared to Comparative Example 3, steam heating resulted in an energy saving of 88.9%, a glycerol monomethyl ether purity of 99.9%, a glycerol monomethyl ether recovery rate of 85.3%, a glycerol purity of 99.5%, and a glycerol recovery rate of 18.1%.

[0096] Example 2

[0097] use Figure 1 The flowchart shown uses epichlorohydrin wastewater 101 from Example 1. The difference is that the operating pressure of buffer tank B is 300 kPa, the operating temperature is 134°C, the residence time is 28 min, and the pH of neutralized wastewater 103 is 8.

[0098] The reflux ratio of the dehydration and concentration tower C is 0.08, the pressure at the top of the tower is 130 kPa, and the temperature at the top of the tower is 107℃.

[0099] The compressor D has an inlet-outlet pressure ratio of 1.8 and an outlet temperature of 116℃, which is 10℃ higher than the bottom temperature of the tower.

[0100] The de-weighted evaporator I operates in a one-on-one standby mode, with an operating pressure of 15 kPa and an operating temperature of 129℃.

[0101] The reflux ratio of dehydration tower J is 1.2, the pressure at the top of the tower is 13 kPa, and the temperature at the top of the tower is 51℃.

[0102] The reflux ratio of product column K is 2.2, the pressure at the top of the column is 5 kPa, and the temperature at the top of the column is 140℃.

[0103] Experiments were conducted using the above process conditions. In Example 2 compared to Comparative Example 3, direct steam heating resulted in 93.5% energy savings, 99.9% purity of glycerol monomethyl ether, 90.0% recovery rate of glycerol monomethyl ether, 99.8% purity of glycerol, and 25.8% recovery rate of glycerol.

[0104] Example 3

[0105] use Figure 1The flowchart shown uses epichlorohydrin wastewater 101 from Example 1. The difference is that the buffer tank B has an operating pressure of 150 kPa, an operating temperature of 111°C, a residence time of 40 min, and a pH of 6 for the neutralized wastewater 103.

[0106] The reflux ratio of the dehydration and concentration tower C is 0.15, the pressure at the top of the tower is 110 kPa, and the temperature at the top of the tower is 102℃.

[0107] The compressor D has an inlet-outlet pressure ratio of 3 and an outlet temperature of 134℃, which is 28℃ higher than the bottom temperature of the tower.

[0108] The de-weighted evaporator I operates in a one-on-one standby mode, with an operating pressure of 35 kPa and an operating temperature of 137℃.

[0109] The reflux ratio of dehydration tower J is 1.2, the pressure at the top of the tower is 20 kPa, and the temperature at the top of the tower is 60℃.

[0110] The reflux ratio of product column K is 2.2, the pressure at the top of the column is 10 kPa, and the temperature at the top of the column is 155℃.

[0111] Experiments were conducted using the above process conditions. In Example 3 compared to Comparative Example 3, direct steam heating resulted in an energy saving of 86.7%, a glycerol monomethyl ether purity of 99.8%, a glycerol monomethyl ether recovery rate of 81.3%, a glycerol purity of 96%, and a glycerol recovery rate of 14.2%.

[0112] Example 4

[0113] The method is the same as in Example 1, except that the reflux ratio of product column K is 0.03, the pressure at the top of the column is 70 kPa, and the temperature at the top of the column is 207°C.

[0114] Experiments were conducted using the above process conditions. In Example 4, compared to Comparative Example 3, direct steam heating resulted in an energy saving of 88.9%, a glycerol monomethyl ether purity of 99.2%, a glycerol monomethyl ether recovery rate of 85.3%, a glycerol purity of 95.7%, and a glycerol recovery rate of 18.1%.

[0115] Example 5

[0116] The method is the same as in Example 1, except that the inlet and outlet pressure ratio of compressor D is 9, and the outlet temperature is 165°C, which is 58°C higher than the temperature of the bottom of the tower.

[0117] Experiments were conducted using the above process conditions. In Example 1 compared to Comparative Example 3, direct steam heating resulted in 69.5% energy savings, 99.9% purity of glycerol monomethyl ether, 85.3% recovery rate of glycerol monomethyl ether, 99.5% purity of glycerol, and 18.1% recovery rate of glycerol.

[0118] Comparative Example 1

[0119] The method is the same as in Example 1, except that neutralization is not performed. Wastewater 101 from the epichlorohydrin unit is directly fed into the dehydration and concentration tower C for dehydration and evaporation treatment, and other conditions are the same as in Example 1. Because the chlorine in 3-chloro-1-methoxy-2-propanol and 3-chloro-1,2-propanediol continuously reacts with water to produce hydrochloric acid, it causes severe corrosion of equipment, pipelines, valves, and instruments, ultimately leading to the unit's inability to operate normally.

[0120] Comparative Example 2

[0121] The method is the same as in Example 1, except that the de-weighing evaporator I is not installed, while other conditions are the same as in Example 1. Because salt has limited solubility in water, as water is continuously evaporated, salt precipitates from the reboiler at the bottom of the dehydration tower, causing increasingly severe scaling in the reboiler, eventually clogging it completely. This forces the unit to be shut down for cleaning, making long-term continuous operation impossible.

[0122] Comparative Example 3

[0123] The method is the same as in Example 2, except that the dehydration and concentration tower uses 0.35 MPaG steam as a heat source, operates at a pressure of 120 kPa, has a top temperature of 105°C, and a reflux ratio of 0.1.

[0124] The conditions for the buffer tank, the de-weight evaporator, the dehydration tower, and the product tower are the same as in Example 2.

[0125] Experiments were conducted using the above process conditions. Comparative Example 3 is equivalent to direct heating with 0.35 MPa steam, which has high energy consumption and no energy-saving effect. The energy consumption is 60 kg standard oil / ton of wastewater. The purity of glycerol monomethyl ether is 99.9%, the recovery rate of glycerol monomethyl ether is 90%, the purity of glycerol is 99.8%, and the recovery rate of glycerol is 25.8%.

[0126] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for recovering organic matter from epichlorohydrin wastewater, wherein, The method includes the following steps: (1) Epichlorohydrin wastewater (101) is introduced into a preprocessor for neutralization treatment to obtain neutralized wastewater (103), wherein the pH of the neutralized wastewater (103) is 5-10; (2) The neutralized wastewater (103) is introduced into the dehydration and concentration tower (C), and the pressurized gas phase (105) at the top of the tower is used as the heat source of the dehydration and concentration tower (C) to dehydrate and evaporate the neutralized wastewater (103) to obtain concentrated wastewater (110). (3) The concentrated wastewater (110) is introduced into the de-weight evaporator (I) for de-weight evaporation treatment to obtain salt-containing waste liquid (115) and de-weight evaporator gas phase (114); (4) The gas phase (114) of the de-oiling evaporator is introduced into the dehydration tower (J) for dehydration treatment to obtain organic matter (117) containing glycerol monomethyl ether and glycerol and wastewater (116). (5) The organic compound (117) containing glycerol monomethyl ether and glycerol is introduced into the product tower (K) for separation treatment to obtain glycerol monomethyl ether (118) and glycerol (119).

2. The method of claim 1, wherein, In step (1), the epichlorohydrin wastewater (101) contains 3-chloro-1-methoxy-2-propanol and 3-chloro-1,2-propanediol; Preferably, based on the total weight of the epichlorohydrin wastewater (101), the content of 3-chloro-1-methoxy-2-propanol is 0.01%-10%, and the content of 3-chloro-1,2-propanediol is 0.01%-10%.

3. The method of claim 1 or 2, wherein, In step (1), the neutralization process is carried out in the presence of an alkaline compound (102), preferably the alkaline compound (102) is selected from at least one of sodium hydroxide, sodium oxide, potassium hydroxide, potassium oxide, calcium hydroxide, calcium oxide, barium hydroxide, barium oxide, and ammonia; Preferably, in step (1), the conditions for the neutralization treatment include: an operating pressure of 100-4000 kPa, an operating temperature of 100-250°C, and a residence time of 1 min-10 h; Preferably, in step (1), the pH of the neutralized wastewater (103) is 7-9.

4. The method of claim 1 or 2, wherein, In step (2), the conditions for the dehydration and evaporation treatment include: a reflux ratio of 0.01-20, a column top pressure of 5-4000 kPa, and a column top temperature of 30-250°C.

5. The method of claim 1 or 2, wherein, Step (2) further includes: using a compressor (D) to pressurize the top gas phase (104) of the dehydration and concentration tower to obtain the pressurized top gas phase (105).

6. The method according to claim 5, wherein, The ratio of the inlet pressure to the outlet pressure of the compressor (D) is 1.05-10:1; Preferably, the temperature of the pressurized gas phase (105) at the top of the tower is at least 5°C higher than the temperature of the bottom of the dehydration and concentration tower (C), and more preferably 8-50°C higher.

7. The method according to claim 1 or 2, wherein, The bottom section of the dehydration concentration tower (C) is equipped with a concentration tower reboiler (E) connected to the bottom section; Preferably, step (2) further includes: after the pressurized gas phase (105) is condensed, a dehydration and concentration tower reflux liquid (108) and discharged wastewater (109) are obtained.

8. The method of claim 1 or 2, wherein, In step (3), the conditions for the de-gravity evaporation treatment include: operating pressure of 1-200 kPa and operating temperature of 20-300 °C; Preferably, in step (3), the conditions for the de-gravity evaporation treatment include: an operating pressure of 5-100 kPa and an operating temperature of 50-160 °C.

9. The method of claim 1 or 2, wherein, In step (4), the conditions for the dehydration treatment include: the reflux ratio of the dehydration tower (J) is 0.01-20, the pressure at the top of the tower is 1-300 kPa, and the temperature at the top of the tower is 7-135℃; Preferably, in step (4), the conditions for the dehydration treatment include: the reflux ratio of the dehydration tower (J) is 0.1-5, the pressure at the top of the tower is 12-90 kPa, and the temperature at the top of the tower is 50-95℃.

10. The method of claim 1 or 2, wherein, In step (5), the separation process conditions include: the product tower (K) reflux ratio is 0.01-20, the tower top pressure is 1-100 kPa, and the tower top temperature is 105-220℃; Preferably, in step (5), the separation process conditions include: a product tower (K) reflux ratio of 0.1-5, a tower top pressure of 3-60 kPa, and a tower top temperature of 125-200℃.

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