CN109851121B - Treatment and recovery system and method for high-salt glycerin-containing organic wastewater - Google Patents
Treatment and recovery system and method for high-salt glycerin-containing organic wastewater Download PDFInfo
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Abstract
The invention relates to a treatment and recovery system of high-salt glycerin-containing organic wastewater, which is provided with a wastewater pretreatment unit, a wastewater treatment unit and a wastewater treatment unit, wherein the wastewater pretreatment unit comprises a pH value adjusting device and a wastewater sedimentation device which are connected; the pH value adjusting device consists of 1 or more than 1 acid adjusting tank; the wastewater sedimentation device is formed by connecting 1 or more than 1 wastewater sedimentation tanks with inverted cone-shaped bottoms through a wastewater conveying pipeline; the top of the settling tank is provided with a tail gas collecting device, the side surface of the settling tank is provided with a wastewater conveying channel, and the bottom of the settling tank is provided with a sediment conveying channel. The invention also provides a method for treating and recycling the high-salt glycerol-containing organic wastewater by using the system. The system and the method provided by the invention have strong pertinence to treatment of high-salt glycerin-containing organic wastewater and recovery of glycerin in the wastewater, are simple in process flow, are suitable for large-scale production, extract the glycerin in the wastewater to change waste into valuable, reduce cost and improve efficiency for enterprises, and respond to national environmental protection policies.
Description
Technical Field
The invention relates to the field of wastewater treatment, in particular to a treatment and recovery process of high-salt-content glycerol-containing organic wastewater.
Background
The high-salt glycerin-containing high-concentration organic wastewater widely exists in the soap-making industry, the epichlorohydrin production industry, the biodiesel production industry, the glycerin production industry and the epoxy resin synthesis industry, and belongs to five industrial fields. The organic wastewater with a large amount of high salt and a certain concentration of glycerin is generated in the industries, and the common indexes of the organic wastewater are that the concentration of sodium chloride is 5-25%, the content of glycerin is about 0.5-20%, and the dichromate index (CODCr for short) is 10000-350000 mg/L. The characteristic that the high salt contains glycerin and high-concentration organic matters makes the treatment difficult to adopt a biological process, and the technology of membrane separation, electrodialysis separation, capacitance adsorption separation and the like is difficult to adopt, and if an extraction separation method, an activated carbon adsorption method, a chemical oxidation method and an incineration method are adopted, huge operation cost is generated, the environmental protection requirements of national environmental protection and sustainable development are not met, and meanwhile, the characteristic of high salt concentration causes serious corrosion to treatment equipment. At present, the treatment of the high-salt glycerol-containing wastewater is difficult, high in cost, not in line with the national environmental protection requirement and sustainable development and the like.
The conventional design of a wastewater pretreatment device in the prior art is inaccurate in acid adjustment, and the pH fluctuation is easily caused by uneven mixing in the later process, so that the process stability is influenced and the equipment is corroded. The settling process generally adopts a standing layering tank and an aging resin settling tank, and a tail gas collecting process is not adopted, so that the tail gas emission can not meet the national environmental protection requirement; even if the common water tank is subjected to corrosion prevention and is used in high-salt wastewater for a long period under a high load, serious corrosion can be caused, and overhaul needs to be carried out for 5 years basically; after long-term use, the sediment (which is a mixture of toluene, epoxy resin, waste epoxy resin polymer and salt particles, and has viscosity, toughness and colloid shape) is difficult to clean, and large amount of manpower is needed for cleaning, and meanwhile, the labor loss is caused. The evaporator generally adopts a film rotor evaporator, and a heat exchange process and equipment are required to be added; the thin film rotor evaporator is suitable for pre-evaporation, the final concentration is not suitable for exceeding 15 percent, otherwise, salt is precipitated, and pipelines are easy to block; the heat conducting oil with the temperature of 220 ℃ is adopted for heating, and the glycerol has the risk of self-polymerization and coking; the film rotor evaporator has small heat exchange area and limited processing capacity due to the limitation of the structure. The conventional design generally adopts a high vacuum and rectifying tower rectifying process, but the high-concentration organic waste water does not only contain glycerin high-boiling-point organic substances, but also contains epoxy resins, glycerin polymerization and residual catalyst isomerate and other organic substances in production, the viscosity of heavy components formed by the organic substances after glycerin evaporation is further improved, and if the rectifying tower is adopted to rectify complex organic substances, the organic substances are not well separated and can easily block fillers, so that the process control difficulty is high.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a system and a method for treating and recycling high-salt glycerol-containing wastewater. The scheme provided by the invention has strong pertinence to the wastewater treatment and the glycerol recovery in the wastewater, is suitable for large-scale production, extracts the glycerol in the wastewater to change waste into valuable, reduces the cost and improves the effect for enterprises, and responds to the national environmental protection policy.
The wastewater treated by the treatment and recovery system and method provided by the invention is a large amount of high-salt organic wastewater containing glycerol with a certain concentration, which is widely existed in industrial fields such as soap making industry, epichlorohydrin production, biodiesel production, glycerol production, epoxy resin synthesis industry and the like. Generally, the wastewater contains 5-25% by mass of sodium chloride and 0.5-20% by mass of a glycerin-like substance. The glycerol-like material is primarily glycerol and may also include polymers of glycerol, such as glycerol dimerization products (e.g., 1, 4-dioxane-2, 6-dimethanol), glycerol trimerization products, glycerol tetramerization products, and the like.
The system and method provided by the invention are preferably directed to wastewater generated in the process of synthesizing epoxy resin. In addition to the large amounts of salts and glyceroids described above, the wastewater may also contain resinous materials, organic solvents, and catalysts used in the synthesis of epoxy resins. In a preferable embodiment of the present invention, the wastewater contains 15 to 25% sodium chloride, 0.5 to 5% glycerin-like substances, 0.02 to 0.2% resin-like substances, 0.1 to 0.5% organic solvent, and 0.01 to 0.05% catalyst for synthesizing epoxy resin; the system and the method provided by the invention have excellent treatment effect on the wastewater with the composition.
Specifically, the treatment and recovery system provided by the invention is provided with a wastewater pretreatment unit, wherein the wastewater pretreatment unit comprises a pH value adjusting device and a wastewater sedimentation device which are connected.
Wherein:
the pH value adjusting device consists of 1 or more than 1 acid adjusting tank, and an inlet of the pH value adjusting device is directly connected with a wastewater storage pool to be treated. Because the common high-salt glycerin-containing organic wastewater contains sodium hydroxide, the wastewater can be neutralized to be neutral (preferably the pH value is 7-8) by hydrochloric acid. In order to realize accurate adjustment, the invention preferably adopts a metering device to meter the amount of wastewater inlet and the amount of hydrochloric acid inlet, and a cascade control system consisting of regulating valves is used for adjustment. As a preferable scheme of the invention, the pH value adjusting device is sequentially performed by a coarse adjusting stage, a middle adjusting stage and a fine adjusting stage, and in the actual production, the pH value adjusting device can be formed by connecting 3 acid adjusting tanks in series, namely a coarse adjusting acid adjusting tank, a middle adjusting acid adjusting tank and a fine adjusting acid adjusting tank. Through the step-by-step adjustment of coarse adjustment, intermediate adjustment and fine adjustment, the pH value of the wastewater can stably reach a target value step by step, and obvious fluctuation is avoided. In order to avoid inaccurate adjustment caused by rapid change of the pH value, the acid adjusting tank can be provided with a stirrer, the stirring speed is preferably 30-60 r/min, and the retention time of the wastewater in each acid adjusting tank is not less than 5 min. The invention can adopt a full-automatic designed pH value adjusting device to further realize accurate adjustment. The pH value adjusting device is arranged in the wastewater pretreatment unit, so that the influence on the process stability and the corrosion on equipment caused by pH fluctuation caused by uneven mixing in the later process can be avoided.
And the wastewater enters a wastewater sedimentation device for standing sedimentation after the pH value of the wastewater is adjusted. The wastewater sedimentation device is formed by connecting 1 or more than 1 wastewater sedimentation tanks with inverted cones at the bottoms through a wastewater conveying pipeline. The waste water settling tank adopts an inverted cone bottom design, and can conveniently output settled bottom materials so as to prevent the problem that the settled bottom materials are difficult to clean after long-term use, and a large amount of time and manpower are consumed if cleaning. The top of each settling tank is provided with an exhaust gas collecting device which adopts a range-dividing nitrogen seal design (the pressure is controlled in a range of 101Kpa to 102 Kpa), and the device is preferably a breather valve (the expiratory pressure is more than 103Kpa, and the inspiratory pressure is less than 101 Kpa). The tail gas collecting device is connected with the tail gas treatment device through the condensing device to form a tail gas treatment system. The tail gas treatment device can treat tail gas by adopting a chemical method, a physical method, a biological method and other methods, so that the tail gas VOC meets the environmental protection requirement while the safety of the wastewater settling tank is ensured. The height of the side channel of the wastewater settling tank is preferably within the range of 1-2 m from the tank bottom, and wastewater is conveyed to a subsequent treatment device through the wastewater channel on the side of the tank body. The bottom of the wastewater settling tank is provided with a sediment conveying channel, preferably, the nitrogen back blowing device is arranged, sediment at the bottom of the tank can be conveniently discharged, and discharged materials can be returned to the device to be extracted and treated to recover substances such as epoxy resin and the like. Because certain organic solvent and chloride ion content inevitably exist in the working environment, the corrosion to the tank body is serious in the environment for a long time, the stainless steel resistant to chloride ion corrosion (the molybdenum content is not less than 2 percent) is preferably adopted in the invention, and the stainless steel has good corrosion resistance in the high-chloride-ion corrosion environment.
The treatment system provided by the invention consists of the wastewater pretreatment unit and a subsequent treatment recovery device. The subsequent treatment and recovery device comprises a glycerin evaporation kettle for glycerin purification, and can also comprise other treatment devices arranged between the pretreatment device and the glycerin purification device.
As a preferable scheme of the invention, the wastewater pretreatment unit is sequentially connected with an evaporation concentration device, a salt precipitation tank, a glycerol concentration evaporator and a glycerol evaporation kettle provided with a vacuum pump.
The wastewater treated by the wastewater pretreatment unit can be further desalted by a filter before entering the evaporation concentration device. The filter is preferably a one-use one-standby design, and when the filtering pressure exceeds 0.2Mpa, the filter automatically blows and removes filter cakes, and the filter is switched. The filter used in the present invention may be a cardboard filter or a candle filter, but the filter aid added must be of the hydrophobic type and have a structure which is relatively rigid and does not change with increasing operating pressure.
The evaporation concentration device can adopt a forced circulation evaporator or a three-effect evaporator which is conventional in the field. The evaporation pressure and the temperature are controlled to be 20-40 Kpa and 40-80 ℃, and because low-temperature evaporation is adopted, decomposition and polymerization of glycerin and other organic matters can be avoided.
And inputting the concentrated solution obtained after evaporation and concentration into a salt precipitation pool for precipitation. During the salt precipitation process, the upper layer liquid and the lower layer salt slurry are automatically separated. And collecting the upper-layer liquid serving as a salt washing mother liquid to enter a mother liquid collecting tank, wherein the materials in the mother liquid collecting tank can be further conveyed to a glycerol concentration evaporator for mother liquid concentration. The salt slurry on the lower layer is crystallized and salified and can be used as a byproduct for export sales after reaching the standard; preferably, the salt at the lower layer is firstly centrifuged by a centrifuge, the supernatant and the materials in the mother liquor collecting tank are combined for concentration, and the sediment at the lower layer is crystallized and salified.
The glycerol concentration evaporator can adopt an external circulation type forced circulation evaporator, has good evaporation concentration efficiency on concentrated wastewater mother liquor, has large treatment capacity, is suitable for materials with certain viscosity, is anti-clogging, has high heat exchange efficiency, and is simple and easy to use. The invention can connect the filter behind the glycerin concentration evaporator, further separate the glycerin-like substance from the salt, and then carry out subsequent evaporation and purification.
The glycerol temporary storage tank is preferably connected before the glycerol evaporation kettle. And (4) conveying the concentrated solution or the concentrated solution subjected to centrifugal desalting into a temporary storage tank for storage, and then conveying into a glycerin evaporation kettle for purification. The glycerin temporary storage tank can adopt steam condensate of the evaporator to carry out heat tracing, adopts a conical bottom design, ensures that the storage tank can be pumped out, and does not accumulate sediments at the bottom of the tank due to long-term use.
According to the invention, the glycerin evaporation kettle provided with a vacuum pump is adopted to evaporate and purify glycerin, and preferably, materials are preheated by the preheater and then conveyed to the glycerin evaporation kettle to be evaporated and purified. Because the invention adopts the ultimate vacuum method to purify the glycerol (the ultimate vacuum can be extracted by adopting a positive displacement vacuum pump), the requirement for controlling the heating area of the evaporation kettle is small, the volume of the evaporation kettle can be effectively reduced, and simultaneously, because the boiling point of the glycerol at 290 ℃ originally is controlled to 120-130 ℃ by extracting the ultimate vacuum, heat conduction oil or high-pressure steam is not needed, only 0.6Mpa steam (the most common steam pressure of a chemical device) is needed to be used as energy, and the low-temperature evaporation is also adopted to avoid the self-polymerization of the glycerol (the glycerol is self-polymerized at 220 ℃), so that the invention is safer and more environment-friendly. The device is connected with a glycerol storage device, and the glycerol purity of the obtained product can reach more than 95%.
The system provided by the invention can solve the problem that no tail gas treatment device is arranged in the high-salt glycerin-containing organic wastewater in the prior art; the sediment is difficult to clean, and a large amount of manpower and material resources are consumed; potential safety hazards of explosion exist; the thin film rotor evaporator channel is easy to block and has small processing capacity; the packing is blocked by the rectification solution in the rectification tower, and the process control difficulty is large.
The invention also provides a method for treating and recycling the high-salt glycerol-containing organic wastewater by using the system, which comprises the following steps of: adjusting the pH value of the wastewater to be neutral, standing and settling, and collecting the upper-layer liquid for later use.
Since the wastewater generally contains a certain amount of alkaline substances (such as sodium hydroxide), the pH value of the wastewater is firstly adjusted to be neutral in the pretreatment step, for example, the pH value of the wastewater is adjusted by adding hydrochloric acid, and is preferably adjusted to be 7-8. By the mode, acid-base neutralization reaction in the wastewater can be well controlled, and the problem that the general wastewater neutralization process causes acidity of the wastewater in a subsequent working section due to insufficient acid-base neutralization so as to influence the recovery of a target product is avoided. The invention preferably adopts a step-by-step adjustment mode to adjust the pH value so as to ensure that the pH value of the wastewater is uniformly changed. And (3) fully standing the wastewater after the pH value is adjusted for 4-8 hours, and then precipitating some particulate matters and organic sediments generated by pH value change to separate the particulate matters from the upper liquid.
The method provided by the invention carries out treatment and recovery after the wastewater pretreatment step, thereby realizing the purposes of wastewater treatment and glycerol recovery. Specifically, the treatment recovery may be performed in the following manner: firstly concentrating, precipitating salt, then concentrating and then purifying, or firstly concentrating and precipitating salt and then purifying, or firstly concentrating and then purifying, or directly purifying the pretreated wastewater.
Wherein the concentration adopts an evaporation concentration mode, and preferably, the evaporation concentration is carried out under the conditions of 20-40 Kpa and the temperature of 40-80 ℃ to form a concentrated solution. The evaporative concentration herein preferably employs an MVR unit or a triple effect evaporator as is common in the art. The invention controls the temperature to be 40-80 ℃ for evaporation, can avoid the decomposition and polymerization of the glycerol and other organic matters, and ensures that the recovered product has higher content of the glycerol. By adopting the evaporation concentration mode, a large amount of condensed wastewater can be generated and can be discharged after reaching the standard after biochemical treatment.
The salt precipitation is carried out in a salt precipitation tank. After sufficient sedimentation, collecting the upper layer liquid as mother liquid, wherein the content of the glycerol can be improved by about 5 to 15 percent compared with the content of the glycerol in the original wastewater. And precipitating the obtained lower-layer salt slurry to obtain a fertile crystal and a salt, and taking the fertile crystal as a byproduct to be sold out after the standard is met.
If the mother liquor after salt precipitation needs to be re-concentrated, still adopting an evaporation concentration mode. This step can be carried out by concentrating the mother liquor using a forced circulation evaporator. The conditions of the evaporation concentration in the step can be the same as the parameters of the concentration, such as the evaporation concentration is carried out under the conditions of 20-40 Kpa and the temperature of 40-80 ℃. According to the invention, the content of the glycerol in the concentrated solution obtained in the step is preferably more than 60%, so that the high-purity glycerol can be recovered and obtained in the subsequent steps under the conditions of energy conservation and environmental protection.
The invention adopts the condition of low-temperature limit vacuum evaporation to evaporate and purify the glycerol. In order to improve the efficiency of glycerin evaporation and purification and reduce energy consumption, the method preferably preheats the concentrated solution to 120-130 ℃ and then carries out evaporation and purification. The invention specifically limits the evaporation to be carried out under the conditions that the pressure is less than 0.5KPa (preferably less than 130Pa) and the temperature is 120-130 ℃. According to a great deal of practice, the unit consumption of 1 ton of evaporated glycerol steam is about 0.4-0.6 ton/ton of product, while the unit consumption of the steam is 1-1.5 ton/ton of product by adopting common negative pressure evaporation (the pressure is controlled at 2-3 Kpa, and the temperature is controlled at 180-200 ℃), so that the method provided by the invention has obvious consumption advantages, and meanwhile, only low-pressure steam is used as a heat source, the risk of adopting high-temperature steam or heat conduction oil is avoided, and the risk of glycerol self-polymerization under the high-temperature condition is also avoided. After the evaporation and purification in the step, the glycerol content in the recovered product is more than 95 percent. And (4) evaporating the residual small amount of organic mixture as hazardous waste, and delivering the hazardous waste to a professional environment-friendly company for treatment.
As a preferred aspect of the present invention, the method comprises the steps of:
s1: evaporating and concentrating the pretreated wastewater at the temperature of 40-80 ℃ under the condition of 20-40 Kpa, and collecting a concentrated solution;
s2: standing and settling the concentrated solution, collecting the upper layer liquid for later use, and taking the lower layer salt slurry as a byproduct for outward sales after crystal cultivation and salt formation;
s3: evaporating and concentrating the upper layer liquid obtained in the step S2 at the temperature of 40-80 ℃ under the condition of 20-40 Kpa to obtain concentrated solution with the glycerol content of more than 60%;
s4: evaporating the concentrated solution under the conditions that the pressure is less than 0.5KPa and the temperature is 120-130 ℃, condensing and recovering the obtained steam, wherein the recovered product contains high-content glycerin.
In order to ensure that the wastewater sent to the subsequent evaporation concentration link does not contain solid particle impurities, the invention preferably filters and desalts the pretreated wastewater, takes the filtrate and then carries out the subsequent operation, and a proper filter aid can be added during the filtration so as to further ensure the removal of solid substances. The invention also preferably carries out filtration and desalination on the concentrated solution, and takes the filtrate for subsequent operation. The filtration desalination can be achieved by centrifugation in a centrifuge to further separate the glyceroids from the salt.
The system and the method provided by the invention meet the national requirements on environmental protection and safety, can effectively treat and recover the high-salt glycerin-containing organic wastewater in large-scale production, and solve the problems of difficult treatment and high treatment cost of the high-salt glycerin-containing organic wastewater. Meanwhile, the difficult problem that the laboratory technology is difficult to be applied to industrial production in a large range is solved through a feasible process thought. The scheme provided by the invention meets 7500 h/year full load production, the COD of the discharged wastewater is less than 40mg/L by the treatment of the system and the method provided by the invention, the national wastewater discharge standard is met, the useful substance glycerol in the wastewater is recycled, the economic income is obtained (the economic income can offset more than 80% of the total cost of wastewater treatment), and meanwhile, the organic matter content in the treated sodium chloride is ensured to meet the national standard.
Drawings
FIG. 1 is a schematic structural view of a system according to embodiment 1; wherein, 1, a pH value adjusting device; 2. a wastewater sedimentation device; 3. a wastewater filter; 4. an evaporation concentration device; 5. a salt precipitation pool; 6. a centrifuge; 7. a glycerin concentration evaporator; 8. a temporary glycerol storage tank; 9. the glycerin evaporates the kettle.
FIG. 2 is a schematic flow chart of the method described in example 6.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Example 1
The embodiment provides a treatment and recovery system for high-salt glycerol-containing organic wastewater, which has a structure shown in fig. 1 and comprises a wastewater pretreatment unit (formed by connecting a pH value adjusting device 1 and a wastewater sedimentation device 2), a wastewater filter 3, an evaporation and concentration device 4, a salt settling tank 5, a glycerol concentration evaporator 7, a desalting centrifuge, a glycerol temporary storage tank 8 and a glycerol evaporation kettle 9, which are connected in sequence; wherein:
the pH value adjusting device 1 consists of 3 acid adjusting tanks connected in series, namely a coarse acid adjusting tank, a middle acid adjusting tank and a fine acid adjusting tank, waste water is neutralized to be neutral through hydrochloric acid after coarse adjustment, middle adjustment and fine adjustment in sequence, each acid adjusting tank is internally provided with a stirrer, the stirring speed is 45 revolutions per minute, and the retention time of the waste water in each acid adjusting tank is 10 minutes; wherein, the inlet of the coarse acid adjusting tank is directly connected with the reservoir of the wastewater to be treated; the pH value adjusting device is internally provided with a flowmeter for metering the flow of wastewater and a pH value regulator, and a cascade control system is formed by adjusting valves to adjust the pH value;
the wastewater sedimentation device 2 is formed by connecting 3 wastewater sedimentation tanks with conical bottoms in series through a wastewater conveying pipeline, and each sedimentation tank is sequentially connected through the wastewater conveying pipeline; the top of each settling tank is provided with a breather valve for collecting tail gas, the tail gas passes through a condenser and then is connected into an independent activated carbon adsorption device, the side surface of each settling tank is provided with a wastewater conveying channel, and the bottom of each settling tank is provided with a sediment conveying channel and a nitrogen back blowing device, so that sediment at the bottom of the tank can be discharged conveniently; the wastewater settling tank is made of stainless steel resistant to chloride ion corrosion;
the waste water outlet of the waste water settling tank is connected with the inlet end of the waste water filter 3, the waste water filter is a one-use one-standby filter, when the filtering pressure exceeds 0.2Mpa, the filter automatically sweeps and removes filter cakes, and the filter is switched;
the liquid outlet of the waste water filter is connected with the inlet of the evaporation concentration device 4, and the evaporation concentration device is a triple-effect evaporator;
the upper part of the salt precipitation tank 5 is connected with a mother liquor collecting tank; the bottom of the salt precipitation tank is connected with a crystal growing and salifying device and the mother liquor collecting tank respectively after passing through a centrifugal machine 6;
the glycerol concentration evaporator 7 is an external circulation type forced circulation evaporator, the inlet end of the glycerol concentration evaporator is connected with the outlet of the mother liquor collecting tank, and the outlet end of the glycerol concentration evaporator is connected with a centrifugal machine; the liquid outlet end of the centrifugal machine is connected with the temporary glycerol storage tank;
a positive displacement vacuum pump is arranged in the glycerin evaporation kettle 9, and the product outlet end of the glycerin evaporation kettle is connected with a glycerin storage device.
Example 2
Compared with example 1, the only difference is that: the device is formed by sequentially connecting a wastewater pretreatment unit (formed by connecting a pH value adjusting device 1 and a wastewater sedimentation device 2), an evaporation concentration device 4, a salt precipitation pool 5, a glycerol concentration evaporator 7 and a glycerol evaporation kettle 9.
Example 3
Compared with example 1, the difference is only that: the device is formed by connecting a wastewater pretreatment unit (formed by connecting a pH value adjusting device 1 and a wastewater sedimentation device 2), an evaporation concentration device 4, a salt sedimentation tank 5 and a glycerol evaporation kettle 9 in sequence.
Example 4
Compared with example 1, the difference is only that: the device is formed by sequentially connecting a wastewater pretreatment unit (formed by connecting a pH value adjusting device 1 and a wastewater sedimentation device 2), an evaporation concentration device 4 and a glycerol evaporation kettle 9.
Example 5
Compared with example 1, the difference is only that: is formed by connecting a wastewater pretreatment unit (formed by connecting a pH value adjusting device 1 and a wastewater sedimentation device 2) and a glycerol evaporation kettle 9.
Example 6
The embodiment provides a method for treating and recycling high-salt glycerol-containing wastewater by using the system provided in embodiment 1, and the flow diagram of the method is shown in FIG. 2; the wastewater is generated in the process of synthesizing epoxy resin, and the water quality (main material composition) before the wastewater is treated is shown in table 1:
table 1: waste water index meter
| Serial number | Index name | Specification of |
| 1 | Appearance of the product | Colorless transparent liquid |
| 2 | NaCl content | 23.61％ |
| 3 | NaOH content | 1.00％ |
| 4 | Glycerol | 0.70％ |
| 5 | Aged resinous suspended matter | 0.10％ |
| 6 | Organic resin | 0.02％ |
| 7 | Toluene | 0.20％ |
| 8 | Catalyst and process for preparing same | 0.02％ |
The method comprises the following steps of firstly utilizing a pretreatment unit to carry out pretreatment on the wastewater: adjusting the pH value of the wastewater to 7.5 by adding hydrochloric acid step by step, standing and settling for 6 hours, collecting tail gas while standing and settling, discharging after meeting the national environmental protection requirement, and collecting upper-layer liquid for later use;
the pretreated wastewater is firstly filtered to remove salt, and the filtrate is collected to be treated as follows:
s1: evaporating and concentrating the pretreated and filtered wastewater at 30Kpa and 60 ℃, and collecting a concentrated solution;
s2: settling the concentrated solution, collecting the upper layer liquid, and detecting that the content of glycerol is 12%; centrifuging the lower layer salt slurry by a centrifuge, mixing clear liquid with the upper layer liquid, and carrying out crystal growth and salt formation on the precipitate to obtain a byproduct for outward sale;
s3: evaporating and concentrating the upper layer liquid at 30Kpa and 60 ℃ to obtain concentrated solution;
and (3) detecting the concentrated solution, wherein the content of main substances is shown in the table 2:
table 2: concentrated solution index meter
S4: filtering the concentrated solution to remove salt, evaporating under the conditions of 130Pa of pressure and 125 ℃, and condensing and recovering the obtained steam;
the detection shows that the content of the glycerol in the recovered product is more than 95 percent, and the organic mixture left after evaporation is used as hazardous waste and is delivered to a professional environment-friendly company for treatment.
Example 7
Compared with the method provided by the embodiment 6, the method provided by the embodiment omits the filtration of the pretreated wastewater and the filtration of the concentrated solution.
The method can realize the recovery of the glycerol, but the treatment efficiency and the treatment effect on the wastewater are not as good as those of the example 6.
Example 8
The system provided in example 3 is used for treating and recovering high-salt glycerol-containing wastewater, and compared with the method provided in example 6, the method provided in this example omits the filtration of pretreated wastewater, the evaporative concentration in step S3, and the filtration of the concentrated solution.
The method can realize the recovery of the glycerol, but the treatment efficiency and the treatment effect on the wastewater are not as good as those of the example 6.
Example 9
Compared with the method in the embodiment 6, the method provided by the embodiment omits the filtration of the wastewater after pretreatment, the salt precipitation in the step S2, the evaporation and concentration in the step S3 and the filtration of the concentrated solution.
The method can realize the recovery of the glycerol, but the treatment efficiency and treatment effect on the wastewater are inferior to those of the embodiment 6, and the process difficulty is high.
Example 10
Compared with the method provided by the embodiment 6, the method provided by the embodiment directly carries out evaporation purification of the pretreated wastewater S4 without intermediate steps.
The method can realize the recovery of the glycerol, but the treatment efficiency and treatment effect on the wastewater are inferior to those of the embodiment 6, and the process difficulty is high.
Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (5)
1. The system for treating and recovering the high-salt glycerin-containing organic wastewater is characterized by comprising a wastewater pretreatment unit, wherein the wastewater pretreatment unit comprises a pH value adjusting device and a wastewater sedimentation device which are connected;
the pH value adjusting device is formed by connecting 3 acid adjusting tanks, namely a coarse acid adjusting tank, a middle acid adjusting tank and a fine acid adjusting tank in series, and is used for neutralizing the wastewater to be neutral;
the wastewater sedimentation device is formed by connecting 1 or more than 1 wastewater sedimentation tanks with inverted cone-shaped bottoms through a wastewater conveying pipeline; the top of the wastewater settling tank is provided with a tail gas collecting device, the side surface of the wastewater settling tank is provided with a wastewater conveying channel, and the bottom of the wastewater settling tank is provided with a sediment conveying channel; the height of the wastewater conveying channel is within 1-2 m from the tank bottom, and wastewater is conveyed to a subsequent treatment device through the wastewater conveying channel on the side surface of the tank body;
the pH value adjusting device is internally provided with a metering device for metering the flow of wastewater and a pH value regulator, and a cascade control system is formed by regulating valves to adjust the pH value;
the pH value adjusting device is sequentially performed by coarse adjustment, middle adjustment and fine adjustment stages; stirring is arranged in the acid adjusting tank;
the tail gas collecting device adopts a split-range nitrogen seal design and is connected with a tail gas treatment device after being condensed; the tail gas collecting device is a breather valve;
the sediment conveying pipeline at the bottom of the wastewater sedimentation tank is provided with a nitrogen back-blowing device which is convenient for discharging the sediment at the bottom of the tank;
the wastewater pretreatment unit is formed by sequentially connecting an evaporation concentration device, a salt precipitation pool, a glycerol concentration evaporator and a glycerol evaporation kettle provided with a vacuum pump; wherein the upper part of the salt precipitation tank is connected with a glycerol concentration evaporator, and the bottom of the salt precipitation tank is connected with a crystal growth and salt formation device; the evaporation pressure is controlled to be 20-40 Kpa, and the temperature is controlled to be 40-80 ℃;
a filter is arranged between the wastewater pretreatment unit and the evaporation concentration device; a filter is arranged between the glycerol concentration evaporator and the glycerol evaporation kettle; a temporary glycerol storage tank is arranged in front of the glycerol evaporation kettle.
2. The system of claim 1, wherein the stirring speed in the acid adjusting tanks is 30-60 r/min, and the retention time of the wastewater in each acid adjusting tank is not less than 5 min.
3. The system of claim 1, wherein the exhalation pressure of the exhalation valve is greater than 103Kpa, the inhalation pressure is less than 101 Kpa; the nitrogen-sealed pressure is controlled in a range of 101Kpa to 102 Kpa.
4. The system of any one of claims 1-3, wherein the wastewater settling tank is a stainless steel material resistant to chloride ion corrosion and has a molybdenum content of not less than 2%.
5. A method for treating and recovering high-salt glycerin-containing organic wastewater by using the system of any one of claims 1 to 4, characterized in that the wastewater is pretreated as follows: adjusting the pH value of the wastewater to 7-8 in a step-by-step adjusting mode to ensure that the pH value of the wastewater is uniformly changed; standing and settling, and collecting upper-layer liquid for later use; the pretreated wastewater is treated by the following steps:
s1: evaporating and concentrating the pretreated wastewater at the temperature of 40-80 ℃ under the condition of 20-40 Kpa, and collecting a concentrated solution;
s2: standing and settling the concentrated solution, collecting the upper layer liquid for later use, and taking the lower layer salt slurry as a byproduct for outward sales after crystal cultivation and salt formation;
s3: evaporating and concentrating the upper layer liquid obtained in the step S2 at the temperature of 40-80 ℃ under the condition of 20-40 Kpa to obtain concentrated solution with the glycerol content of more than 60%;
s4: evaporating the concentrated solution under the conditions that the pressure is less than 0.5KPa and the temperature is 120-130 ℃, and condensing and recovering the obtained steam;
filtering the pretreated wastewater to remove salt, collecting filtrate, and performing the operation of step S1; filtering the concentrated solution obtained in the step S3 to remove salt, collecting filtrate, and then performing the operation of the step S4;
the wastewater contains 5-25% of sodium chloride and 0.5-20% of glycerin-like substances;
the wastewater is generated by synthesizing epoxy resin, and also contains resin substances, organic solvents and catalysts used for synthesizing the epoxy resin.
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| CN101139255A (en) * | 2007-09-07 | 2008-03-12 | 浙江大学 | Hyperfiltration-distillation integration process for reclaiming glycerin from low-concentration sweet water |
| CN102757153A (en) * | 2012-07-12 | 2012-10-31 | 山东天兴生物科技有限公司 | Method for treating wastewater generated during production of 12-hydroxy stearic acid |
| CN104230659A (en) * | 2014-08-21 | 2014-12-24 | 波鹰(厦门)科技有限公司 | Method for recovering sodium chloride and glycerol from high-salt glycerol-containing high-depth organic wastewater |
| CN106587476A (en) * | 2016-12-21 | 2017-04-26 | 科迈化工股份有限公司 | Method for treatment of mixed wastewater produced during production of rubber accelerator NS\CZ\DZ |
| CN106809999A (en) * | 2017-03-17 | 2017-06-09 | 黄山清源环境工程技术服务有限公司 | Epoxy resin high-concentration waste water processing system |
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| CN105712580A (en) * | 2016-03-07 | 2016-06-29 | 中蓝连海设计研究院 | Reduction treatment device and method for epoxy resin wastewater evaporative desalination mother liquor |
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|---|---|---|---|---|
| CN101139255A (en) * | 2007-09-07 | 2008-03-12 | 浙江大学 | Hyperfiltration-distillation integration process for reclaiming glycerin from low-concentration sweet water |
| CN102757153A (en) * | 2012-07-12 | 2012-10-31 | 山东天兴生物科技有限公司 | Method for treating wastewater generated during production of 12-hydroxy stearic acid |
| CN104230659A (en) * | 2014-08-21 | 2014-12-24 | 波鹰(厦门)科技有限公司 | Method for recovering sodium chloride and glycerol from high-salt glycerol-containing high-depth organic wastewater |
| CN106587476A (en) * | 2016-12-21 | 2017-04-26 | 科迈化工股份有限公司 | Method for treatment of mixed wastewater produced during production of rubber accelerator NS\CZ\DZ |
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