Treatment system and method for acetic acid phosphorus-containing wastewater

Abstract

The invention relates to the technical field of wastewater treatment, in particular to an acetic acid phosphorus-containing wastewater treatment system and method. In the system provided by the invention, all the equipment can be well matched, so that the wastewater treatment difficulty is greatly reduced, the operation efficiency is improved, and the requirements of acetic acid recovery and phosphorus removal are met. The triple-effect separator has a larger gas-liquid separation space, the gas-liquid separation effect is good, the flow speed of secondary steam is reduced, entrainment is reduced, meanwhile, a demisting device is arranged in the triple-effect separator, the purification effect of the secondary steam is enhanced, and the effluent quality is improved. According to the treatment system and method for the acetic acid phosphorus-containing wastewater, the recovery rate of acetic acid is high, and the removal rate of phosphorus and the removal rate of ammonia nitrogen are high.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a system and method for treating acetic acid phosphorus-containing wastewater. Background Art

[0002] Acetic acid is an important organic chemical raw material, mainly used to prepare cellulose acetate, which is a common raw material for rayon and movie film. Acetic acid can also be used to synthesize diethyl malonate, ethyl acetoacetate, etc., to manufacture medicines, and to produce acetates. Acetic acid is widely used in medicine, dyes, textile dyeing and rubber industries. In the industrial production process of acetate esters, there are many by-products of acetic acid, and the mass fraction of these acetic acids is very low, so they need to go through a concentration and purification process to increase the added value of the product.

[0003] The preparation process of acetic acid and other production processes involving acetic acid will produce a large amount of acetic acid-containing wastewater. The existing methods for recovering acetic acid from wastewater include: ordinary distillation method, azeotropic distillation method, etc.

[0004] In the ordinary distillation method, acetic acid and water cannot form an azeotrope, so the distillation recovery of acetic acid adopts the ordinary distillation method to obtain the heavy component acetic acid at the bottom of the tower. Although acetic acid-water does not form an azeotrope, the two have similar volatility and belong to a highly non-ideal system. In order to obtain acetic acid with higher purity, the ordinary distillation method requires the distillation tower to meet many plate number requirements and a large reflux ratio. It is mainly used for the purification of crude acetic acid with a small water content. In addition, this method will consume a lot of fuel and has low economic effect, so it is generally not recommended.

[0005] The main operation process of azeotropic distillation is: the low-boiling entrainer and the raw material liquid enter the azeotropic distillation tower together, so that the relative volatility of acetic acid and water increases, the water and entrainer are evaporated from the top of the tower, and after cooling and separation, the entrainer is returned to the tower again, the water is discharged, and the acetic acid product is generated in the bottom of the tower. However, the azeotropic distillation method requires a high acetic acid content in the system and the entrainer has stable chemical properties. At the same time, it will introduce new impurities, which is not conducive to subsequent recycling. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a system and method for treating acetic acid phosphorus-containing wastewater, with a high acetic acid recovery rate, and high phosphorus removal rates and ammonia nitrogen removal rates.

[0007] The present invention provides a treatment system for acetic acid phosphorus-containing wastewater, comprising:

[0008] Preheater;

[0009] A first-effect heater, the liquid inlet of the first-effect heater is connected to the liquid outlet of the preheater; a first-effect falling film circulation pump, the first-effect falling film circulation pump is used to transport the liquid evaporated and separated by the first-effect heater to the first-effect heater, forming a first circulation loop;

[0010] A first-effect separator; the secondary steam inlet of the first-effect separator is connected to the secondary steam outlet of the first-effect heater; the liquid outlet of the first-effect separator is connected to the first circulation loop;

[0011] A second-effect heater, wherein the secondary steam inlet of the second-effect heater is connected to the secondary steam outlet of the first-effect separator; a second-effect falling film circulation pump, wherein the second-effect falling film circulation pump is used to transport the feed liquid after evaporation and separation in the second-effect heater to the second-effect heater to form a second circulation loop;

[0012] On the first circulation loop, a branch of the first circulation loop is arranged at the outlet of the first-effect falling film circulation pump, and the outlet of the branch is connected to the second circulation loop, so as to transport part of the liquid in the first-effect heater to the second circulation loop;

[0013] A second-effect separator; the secondary steam inlet of the second-effect separator is connected to the secondary steam outlet of the second-effect heater; the feed liquid outlet of the second-effect separator is connected to the second circulation loop;

[0014] A secondary steam outlet is provided at the top of the second-effect separator, and the secondary steam outlet pipeline is provided with two outgoing paths, the first outgoing path is connected to the secondary steam inlet of the No. 1 triple-effect heater, and the second outgoing path is connected to the secondary steam inlet of the No. 2 triple-effect heater;

[0015] A three-effect forced circulation pump, which is used to transport the liquid in the three-effect separator to the No. 1 three-effect heater and the No. 2 three-effect heater in sequence, and then enter the three-effect separator to form a third circulation loop;

[0016] On the second circulation loop, a branch of the second circulation loop is arranged at the outlet of the second-effect falling film circulation pump, and the outlet of the branch is connected to the third circulation loop, so as to transport part of the feed liquid in the second-effect heater to the third circulation loop;

[0017] a condenser connected to the secondary steam outlet of the triple-effect separator;

[0018] a gas-liquid separator connected to the outlet of the condenser;

[0019] On the third circulation loop, a branch of the third circulation loop is arranged at the outlet of the triple-effect forced circulation pump, and the outlet of the branch is connected to the evaporator processing unit.

[0020] Preferably, the triple-effect separator comprises:

[0021] Through-hole barrel;

[0022] An upper end cap fixedly connected to the top of the cylinder; the upper end cap is cone-shaped; a demisting device is arranged inside the upper end cap; a secondary steam outlet is arranged at the top of the upper end cap;

[0023] A lower head fixedly connected to the bottom of the cylinder; the lower head is in the shape of an inverted cone; a circulating discharge port is arranged on the side wall of the lower head;

[0024] A circulating feed port is arranged at the lower end of the side wall of the cylinder.

[0025] Preferably, the diameter of the cylinder is 1000-2000 mm and the height is 3000-6000 mm;

[0026] The secondary steam outlet diameter of the upper head is 200-600 mm; the height of the upper head is 800-2000 mm;

[0027] The height of the lower head is 800-2000 mm;

[0028] The demisting device is a wire mesh demisting device.

[0029] Preferably, the preheater is a tubular heat exchanger, and the diameter of the heat exchange tube is 23 to 27 mm.

[0030] Preferably, the first-effect heater includes a membrane cloth device, and the membrane cloth device adopts a large-diameter membrane cloth with a diameter of 11 to 13 mm;

[0031] In a single-effect heater, the inner diameter of the heat exchange tube is 30 to 34 mm.

[0032] Preferably, the two-effect heater includes a membrane cloth device, and the membrane cloth device adopts a large-diameter membrane cloth with a diameter of 11 to 13 mm;

[0033] In the two-effect heater, the inner diameter of the heat exchange tube is 30 to 34 mm.

[0034] Preferably, the inner diameter of the heat exchange tube of the No. 1 triple-effect heater 10-1 is 30-34 mm;

[0035] The inner diameter of the heat exchange tube of the No. 2 triple-effect heater 10-2 is 30-34 mm.

[0036] The present invention also provides a method for treating acetic acid phosphorus-containing wastewater using the treatment system described above, comprising the following steps:

[0037] A) Preheating the acetic acid phosphorus wastewater to 40-60°C;

[0038] B) circulating the preheated wastewater in a first-effect heater for heating and evaporation to obtain feed liquid and secondary steam; the feed liquid flows back to the first-effect heater via a first circulation loop, and the secondary steam enters a first-effect separator for gas-liquid separation; the feed liquid after gas-liquid separation flows back to the first circulation loop;

[0039] C) transporting the secondary steam after gas-liquid separation in the first-effect separator to the second-effect heater;

[0040] Part of the feed liquid in the first circulation loop is transported to the second circulation loop, and circulated and heated with the secondary steam in the second-effect heater to evaporate, so as to obtain feed liquid and secondary steam; the feed liquid is refluxed to the second-effect heater via the second circulation loop, and the secondary steam enters the second-effect separator for gas-liquid separation; the feed liquid after gas-liquid separation in the second-effect separator is refluxed to the second circulation loop;

[0041] D) transporting the secondary steam after gas-liquid separation in the second-effect separator to triple-effect heater No. 1 and triple-effect heater No. 2 respectively;

[0042] Part of the feed liquid in the second circulation loop is transported to the third circulation loop, and circulated and heated to evaporate with the secondary steam after gas-liquid separation in the second-effect separator to obtain feed liquid and secondary steam; the feed liquid is transported to the evaporator treatment unit for evaporation and concentration; the secondary steam enters the three-effect separator for gas-liquid separation; the secondary steam after gas-liquid separation enters the condenser for condensation, and the gas and liquid are separated to obtain condensate, which is the treated water body.

[0043] Preferably, the temperature of the liquid in the heat exchange tube of the first-effect heater is 100-120°C;

[0044] The temperature of the liquid in the heat exchange tube of the second-effect heater is 80-100°C;

[0045] The temperature of the liquid in the heat exchange tubes of the No. 1 triple-effect heater and the No. 2 triple-effect heater is 60-80°C;

[0046] The concentrated liquid is further evaporated and concentrated in the evaporator treatment unit at an evaporation temperature of 48-52°C.

[0047] Preferably, the rate at which the secondary steam after gas-liquid separation in the first-effect separator is transported to the second-effect heater is 20 to 30 m / s;

[0048] The secondary steam after gas-liquid separation in the second-effect separator is transported to the No. 1 triple-effect heater and the No. 2 triple-effect heater at a rate of 20 to 30 m / s;

[0049] The secondary steam separated from the gas and liquid by the triple-effect separator is transported to the condenser at a flow rate of 1 to 2 m / s.

[0050] The present invention provides a treatment system for acetic acid phosphorus-containing wastewater, in which various devices can cooperate well with each other, greatly reducing the difficulty of wastewater treatment, improving operation efficiency, and achieving the requirements of acetic acid recovery and phosphorus removal. The triple-effect separator in the present invention has a larger volume of gas-liquid separation space, good gas-liquid separation effect, reduces the secondary steam flow rate, reduces mist entrainment, and at the same time, a demisting device is provided in the triple-effect separator to enhance the purification effect of the secondary steam and improve the effluent water quality. The treatment system and method for acetic acid phosphorus-containing wastewater provided by the present invention have a high recovery rate of acetic acid, and a high removal rate of phosphorus and ammonia nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A diagram of a treatment system for acetic acid phosphorus-containing wastewater provided by one embodiment of the present invention;

[0052] Figure 2 A structural diagram of a triple-effect separator provided for one embodiment of the present invention. DETAILED DESCRIPTION

[0053] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] The present invention provides a treatment system for acetic acid phosphorus-containing wastewater, comprising:

[0055] Preheater;

[0056] A first-effect heater, the liquid inlet of the first-effect heater is connected to the liquid outlet of the preheater; a first-effect falling film circulation pump, the first-effect falling film circulation pump is used to transport the liquid evaporated and separated by the first-effect heater to the first-effect heater, forming a first circulation loop;

[0057] A first-effect separator; the secondary steam inlet of the first-effect separator is connected to the secondary steam outlet of the first-effect heater; the liquid outlet of the first-effect separator is connected to the first circulation loop;

[0058] A second-effect heater, wherein the secondary steam inlet of the second-effect heater is connected to the secondary steam outlet of the first-effect separator; a second-effect falling film circulation pump, wherein the second-effect falling film circulation pump is used to transport the feed liquid after evaporation and separation in the second-effect heater to the second-effect heater to form a second circulation loop;

[0059] On the first circulation loop, a branch of the first circulation loop is arranged at the outlet of the first-effect falling film circulation pump, and the outlet of the branch is connected to the second circulation loop, so as to transport part of the liquid in the first-effect heater to the second circulation loop;

[0060] A second-effect separator; the secondary steam inlet of the second-effect separator is connected to the secondary steam outlet of the second-effect heater; the feed liquid outlet of the second-effect separator is connected to the second circulation loop;

[0061] A secondary steam outlet is provided at the top of the second-effect separator, and the secondary steam outlet pipeline is provided with two outgoing paths, the first outgoing path is connected to the secondary steam inlet of the No. 1 triple-effect heater, and the second outgoing path is connected to the secondary steam inlet of the No. 2 triple-effect heater;

[0062] A three-effect forced circulation pump, which is used to transport the liquid in the three-effect separator to the No. 1 three-effect heater and the No. 2 three-effect heater in sequence, and then enter the three-effect separator to form a third circulation loop;

[0063] On the second circulation loop, a branch of the second circulation loop is arranged at the outlet of the second-effect falling film circulation pump, and the outlet of the branch is connected to the third circulation loop, so as to transport part of the feed liquid in the second-effect heater to the third circulation loop;

[0064] a condenser connected to the secondary steam outlet of the triple-effect separator;

[0065] a gas-liquid separator connected to the outlet of the condenser;

[0066] On the third circulation loop, a branch of the third circulation loop is arranged at the outlet of the triple-effect forced circulation pump, and the outlet of the branch is connected to the evaporator processing unit.

[0067] Figure 1 A treatment system diagram of acetic acid phosphorus-containing wastewater provided for an embodiment of the present invention. 1 is a raw liquid tank, 2 is a feed pump, 3 is a preheater, 4 is a first-effect heater, 5 is a first-effect separator, 6 is a first-effect falling film circulation pump, 7 is a second-effect heater, 8 is a second-effect separator, 9 is a second-effect falling film circulation pump, 10-1 is a No. 1 triple-effect heater, 10-2 is a No. 2 triple-effect heater, 11 is a triple-effect separator, 12 is a triple-effect forced circulation pump, 13 is a discharge pump, 14-1 is a first evaporation kettle, 14-2 is a second evaporation kettle, 15 is a condenser, 16 is a gas-liquid separator, and 17 is a fresh water tank. ① is the first circulation loop, ② is the second circulation loop, ③ is a branch of the first circulation loop, ④ is the third circulation loop, ⑤ is a branch of the second circulation loop, and ⑥ is a branch of the third circulation loop.

[0068] In some embodiments of the present invention, the treatment system further comprises a stock liquid tank 1. The stock liquid tank 1 is used to store the stock liquid, i.e., acetic acid phosphorus-containing wastewater. The present invention has no particular restrictions on the structure and type of the stock liquid tank, and it can be used to store the stock liquid.

[0069] In some embodiments of the present invention, the processing system further comprises a feed pump 2. The feed pump is used to transport the raw liquid in the raw liquid tank 1 to the preheater 3. The present invention has no special restrictions on the connection mode of the feed pump 2, and the raw liquid in the raw liquid tank 1 can be transported to the preheater 3. The feed pump 2 can be a centrifugal pump.

[0070] The preheater 3 is used to preheat the stock solution, and the temperature of the preheated stock solution is 40-60° C. In some embodiments, the preheater is a tubular heat exchanger, and the diameter of the heat exchange tube is 23-27 mm, such as 25 mm.

[0071] In the present invention, the liquid feed inlet of the first-effect heater 4 is connected to the liquid feed outlet of the preheater 3. The liquid feed is heated and evaporated in the first-effect heater 4.

[0072] In some embodiments of the present invention, the treatment system further includes a first-effect falling film circulation pump 6. The first-effect falling film circulation pump 6 is used for the circulation of the first-effect liquid. The liquid in the first-effect heater 4 falls in the form of a film under the influence of gravity, and is then pumped into the top inlet of the first-effect heater 4 by the first-effect falling film circulation pump 6 for circulation heating and evaporation. The first-effect falling film circulation pump 6 is used to transport the liquid evaporated and separated in the first-effect heater 4 to the first-effect heater 4, forming a first circulation loop ①. The present invention has no special restrictions on the connection method of the first-effect falling film circulation pump 6, and the liquid evaporated and separated in the first-effect heater 4 can be transported to the top of the first-effect heater 4 again. The first-effect falling film circulation pump 6 can be a centrifugal pump.

[0073] The first-effect heater 4 includes a membrane cloth device, which uses a large-diameter membrane cloth with a diameter of 11 to 13 mm, such as 12 mm, to enhance the permeability and prevent impurities from clogging the water holes. In the first-effect heater 4, the inner diameter of the heat exchange tube is 30 to 34 mm, such as 32 mm. The feed liquid flows from top to bottom in a film-like state, and the thickness of the feed liquid film can be adjusted according to the feed liquid concentration, at 0.5 to 2 mm, to prevent the feed liquid in the tube from drying up and enhance the anti-scaling ability of the heat exchange tube. The temperature of the feed liquid in the heat exchange tube is 100 to 120°C, and secondary steam of about 100°C is generated, which goes to the first-effect separator 5. The first-effect heater 4 can be a tubular heat exchanger.

[0074] The bottom of the first-effect separator 5 is provided with a liquid outlet, and the liquid outlet of the first-effect separator 5 is connected to the first circulation loop. Specifically, the liquid discharge pipe outlet of the first-effect separator 5 is arranged at the liquid outlet of the first-effect heater on the first circulation loop.

[0075] The first-effect separator 5 may be a gas-liquid separator.

[0076] The secondary steam separated from the first-effect separator 5 is transported to the second-effect heater 7. The transport rate is 20-30 m / s. The steam flow rate is controlled by designing the diameter of the transport pipeline. The secondary steam flow rate is low, which can reduce the phosphorus and ammonia nitrogen content in the evaporated condensed water. After that, the concentrated liquid continues to participate in the circulation. When the feed liquid concentration reaches the set value, the concentrated liquid automatically enters the next effect.

[0077] In some embodiments of the present invention, the treatment system further includes a second-effect falling film circulation pump 9. The second-effect falling film circulation pump 9 is used for the circulation of the second-effect liquid. The liquid in the second-effect heater 7 falls in the form of a film under the influence of gravity, and is then pumped into the top inlet of the second-effect heater 7 by the second-effect falling film circulation pump 9 for circulation heating and evaporation. The second-effect falling film circulation pump 9 is used to transport the liquid evaporated and separated by the second-effect heater 7 to the second-effect heater 7, forming a second circulation loop ②. The present invention has no special restrictions on the connection method of the second-effect falling film circulation pump 9, and the liquid evaporated and separated by the second-effect heater 7 can be transported to the top of the second-effect heater 7 again. The second-effect falling film circulation pump 9 can be a centrifugal pump.

[0078] In some embodiments of the present invention, on the first circulation loop formed by the first-effect falling film circulation pump 6, a branch ③ (i.e., a branch of the first circulation loop) is arranged at the outlet of the first-effect falling film circulation pump 6, and the outlet of the branch is connected to the second circulation loop, so as to transport part of the slurry in the first-effect heater 4 to the second circulation loop, specifically to the second-effect heater 7.

[0079] The second-effect heater 7 includes a membrane cloth device, which uses a large-diameter membrane cloth with a diameter of 11 to 13 mm, such as 12 mm, to enhance the permeability and prevent impurities from clogging the water holes. In the second-effect heater 7, the inner diameter of the heat exchange tube is 30 to 34 mm, such as 32 mm. The feed liquid flows from top to bottom in a film-like state, and the thickness of the feed liquid film can be adjusted according to the feed liquid concentration, at 0.5 to 2 mm, to prevent the feed liquid in the tube from drying up and enhance the anti-scaling ability of the heat exchange tube. The temperature of the feed liquid in the heat exchange tube is 80 to 100°C, and secondary steam of about 80°C is generated, which goes to the second-effect separator 8. The second-effect heater 7 can be a tubular heat exchanger.

[0080] The bottom of the second-effect separator 8 is provided with a liquid outlet, and the liquid outlet of the second-effect separator 8 is connected to the second circulation loop. Specifically, the liquid discharge pipe outlet of the second-effect separator 8 is arranged at the liquid outlet of the second-effect heater on the second circulation loop.

[0081] A secondary steam outlet is provided at the top of the second-effect separator 8, and the secondary steam outlet pipe is provided with two outgoing paths, the first outgoing path is connected to the secondary steam inlet of the No. 1 triple effect heater 10-1, and the second outgoing path is connected to the secondary steam inlet of the No. 2 triple effect heater 10-2. The secondary steam inlet of the No. 1 triple effect heater 10-1 is provided at the upper part of the side wall of the No. 1 triple effect heater 10-1, and the secondary steam inlet of the No. 2 triple effect heater 10-2 is provided at the upper part of the side wall of the No. 2 triple effect heater 10-2.

[0082] The secondary steam separated from the secondary effect separator 8 is transported to the No. 1 triple effect heater 10-1 and the No. 2 triple effect heater 10-2. The transport rate is 20-30m / s. The steam flow rate is controlled by designing the diameter of the transport pipeline. The secondary steam flow rate is low, which can reduce the phosphorus and ammonia nitrogen content in the evaporated condensed water. After that, the concentrated liquid continues to participate in the circulation. When the feed liquid concentration reaches the set value, the concentrated liquid automatically enters the next effect.

[0083] The secondary effect separator 8 may be a gas-liquid separator.

[0084] In some embodiments of the present invention, the treatment system also includes a triple-effect forced circulation pump 12. The triple-effect forced circulation pump 12 is used to pump the liquid in the triple-effect separator 11 into the No. 1 triple-effect heater 10-1, and then enter the No. 2 triple-effect heater 10-2 through the triple-effect forced circulation pump 12, and then enter the triple-effect separator 11 again for evaporation and separation. The separated liquid enters the No. 1 triple-effect heater 10-1 again and circulates in sequence. The triple-effect forced circulation pump 12 is used to transport the liquid in the triple-effect separator 11 to the No. 1 triple-effect heater 10-1 and the No. 2 triple-effect heater 10-2 in sequence, and then enter the triple-effect separator 11 to form a third circulation loop ④ for cyclic heating and evaporation. The present invention has no special restrictions on the connection method of the triple-effect forced circulation pump 12, and can realize that the liquid in the triple-effect separator 11 is transported to the No. 1 triple-effect heater 10-1 and the No. 2 triple-effect heater 10-2 in sequence, and then enters the triple-effect separator 11. The triple-effect forced circulation pump 12 can be an axial flow pump.

[0085] In some embodiments of the present invention, on the second circulation loop formed by the second-effect falling film circulation pump 9, a branch ⑤ (i.e., a branch of the second circulation loop) is provided at the outlet of the second-effect falling film circulation pump 9, and the outlet of the branch is connected to the third circulation loop, and is used to transport part of the liquid in the second-effect heater 7 to the third circulation loop. Specifically, the outlet of the branch ⑤ is connected to the third circulation loop, and is used to transport part of the liquid in the second-effect heater 7 to the No. 2 triple-effect heater 10-2.

[0086] In the No. 1 triple effect heater 10-1 and the No. 2 triple effect heater 10-2, the inner diameter of the heat exchange tube is 30-34 mm, for example, 32 mm. The feed liquid is circulated and heated in the No. 1 triple effect heater 10-1 and the No. 2 triple effect heater 10-2, and forced violent turbulence is made to increase the heat transfer coefficient, and at the same time, the heat exchange surface is flushed to enhance the anti-scaling ability of the heat exchange tube; the feed liquid temperature in the tube is 60-80°C, and secondary steam of about 60°C is generated. The secondary steam rises and goes to the triple effect separator 11. The No. 1 triple effect heater 10-1 and the No. 2 triple effect heater 10-2 can be tubular heat exchangers.

[0087] In some embodiments of the present invention, the triple-effect separator 11 comprises:

[0088] A through-barrel 11-2;

[0089] An upper end cap 11-1 fixedly connected to the top of the cylinder 11-2; the upper end cap 11-1 is cone-shaped; a demisting device is arranged inside the upper end cap 11-1; a secondary steam outlet is arranged at the top of the upper end cap;

[0090] A lower end cap 11-3 fixedly connected to the bottom of the cylinder 11-2; the lower end cap 11-3 is an inverted cone; a circulating discharge port is arranged on the side wall of the lower end cap 11-3;

[0091] A circulating feed port is arranged at the lower end of the side wall of the cylinder 11-2.

[0092] Figure 2 A structural diagram of a triple-effect separator provided for one embodiment of the present invention.

[0093] The large separation space in the triple-effect separator makes the secondary steam have an extremely low flow rate, making it difficult for liquids with a diameter exceeding 15μm to enter the secondary steam pipeline, thus avoiding a large amount of mist carryover and material leakage from the source.

[0094] The diameter of the cylinder 11 - 2 is 1000 to 2000 mm, and the height is 3000 to 6000 mm.

[0095] The secondary steam outlet diameter of the upper head 11-1 is 200-600 mm. The height of the upper head 11-1 is 800-2000 mm.

[0096] The height of the lower head 11-3 is 800-2000 mm.

[0097] The demisting device is a wire mesh demisting device.

[0098] In some embodiments of the present invention, on the third circulation loop formed by the triple-effect forced circulation pump 12, a branch ⑥ (i.e., a branch of the third circulation loop) is provided at the outlet of the triple-effect forced circulation pump 12, and the outlet of the branch is connected to the evaporator processing unit. Specifically, the outlet of the branch is connected to the evaporator processing unit through a discharge pump 13.

[0099] When the concentration of the feed liquid in the third circulation loop reaches the designed value, the concentrated liquid automatically enters the evaporator processing unit. In some embodiments of the present invention, the evaporator processing unit includes a first evaporator 14-1 and a second evaporator 14-2 arranged in parallel. The evaporator processing unit is used for further evaporation and concentration. The first evaporator 14-1 and the second evaporator 14-2 can be reactors.

[0100] The discharge pump 13 is a centrifugal pump and is used to provide power for conveying the concentrated liquid.

[0101] The concentrated liquid is further evaporated and concentrated in the evaporator 14, and the evaporation temperature is 48-52°C, for example, 50°C, and the final concentrated liquid output is reduced by about 40 times.

[0102] The secondary steam separated from the three-effect separator 11 is transported to the condenser 15 at a flow rate of 1-2 m / s. The secondary steam flow rate is relatively low, which can reduce the phosphorus and ammonia nitrogen content in the evaporated condensed water.

[0103] The condenser 15 is a plate heat exchanger, which is used to condense the secondary steam.

[0104] The gas-liquid separator 16 can be a commercially available one, and is used for gas-liquid separation of the condensed feed liquid.

[0105] In some embodiments of the present invention, the treatment system further comprises a fresh water tank 17 connected to the liquid outlet of the gas-liquid separator 16 for effectively storing condensate. The present invention has no particular limitation on the type and structure of the fresh water tank 17, which can be used to store condensate.

[0106] The present invention also provides a method for treating acetic acid phosphorus-containing wastewater using the above-mentioned treatment system, comprising the following steps:

[0107] A) Preheating the acetic acid phosphorus wastewater to 40-60°C;

[0108] B) circulating the preheated wastewater in a first-effect heater for heating and evaporation to obtain feed liquid and secondary steam; the feed liquid flows back to the first-effect heater via a first circulation loop, and the secondary steam enters a first-effect separator for gas-liquid separation; the feed liquid after gas-liquid separation flows back to the first circulation loop;

[0109] C) transporting the secondary steam after gas-liquid separation in the first-effect separator to the second-effect heater;

[0110] Part of the feed liquid in the first circulation loop is transported to the second circulation loop, and circulated and heated with the secondary steam in the second-effect heater to evaporate, so as to obtain feed liquid and secondary steam; the feed liquid is refluxed to the second-effect heater via the second circulation loop, and the secondary steam enters the second-effect separator for gas-liquid separation; the feed liquid after gas-liquid separation in the second-effect separator is refluxed to the second circulation loop;

[0111] D) transporting the secondary steam after gas-liquid separation in the second-effect separator to triple-effect heater No. 1 and triple-effect heater No. 2 respectively;

[0112] Part of the feed liquid in the second circulation loop is transported to the third circulation loop, and circulated and heated to evaporate with the secondary steam after gas-liquid separation in the second-effect separator to obtain feed liquid and secondary steam; the feed liquid is transported to the evaporator treatment unit for evaporation and concentration; the secondary steam enters the three-effect separator for gas-liquid separation; the secondary steam after gas-liquid separation enters the condenser for condensation, and the gas and liquid are separated to obtain condensate, which is the treated water body.

[0113] In some embodiments of the present invention, the mass concentration of acetic acid in the acetic acid phosphorus-containing wastewater is 30% to 50%, the mass concentration of total phosphorus is 0.02% to 0.1%, and the mass concentration of ammonia nitrogen is 0.05% to 0.2%. Specifically, the mass concentration of acetic acid in the acetic acid phosphorus-containing wastewater is 4%, the mass concentration of total phosphorus is 0.1%, and the mass concentration of ammonia nitrogen is 0.2%.

[0114] In some embodiments of the present invention, the temperature of the liquid in the heat exchange tube of the first-effect heater is 100-120°C.

[0115] In some embodiments of the present invention, the temperature of the liquid in the heat exchange tube of the second-effect heater is 80-100°C.

[0116] In some embodiments of the present invention, the rate at which the secondary steam after gas-liquid separation in the first-effect separator is transported to the second-effect heater is 20 to 30 m / s.

[0117] In some embodiments of the present invention, 60% (calculated by mass content) of the feed solution in the first circulation loop is transported to the second circulation loop.

[0118] In some embodiments of the present invention, the secondary steam after gas-liquid separation in the second-effect separator is respectively transported to the No. 1 triple-effect heater and the No. 2 triple-effect heater at a rate of 20 to 30 m / s.

[0119] In some embodiments of the present invention, the temperature of the liquid in the heat exchange tubes of the No. 1 triple-effect heater and the No. 2 triple-effect heater is 60-80°C.

[0120] In some embodiments of the present invention, 50% (calculated by mass content) of the feed solution in the second circulation loop is transported to the third circulation loop.

[0121] In some embodiments of the present invention, the concentrated liquid is further evaporated and concentrated in an evaporator treatment unit, and the evaporation temperature is 48-52°C.

[0122] In some embodiments of the present invention, the secondary steam separated from the gas and liquid by the triple-effect separator is transported to the condenser at a flow rate of 1 to 2 m / s.

[0123] In the treated water obtained by the whole system (i.e., the condensate in the fresh water tank 17), the acetic acid recovery rate is ≥90%, the phosphorus removal rate is ≥95%, and the ammonia nitrogen removal rate is up to 70%, thereby achieving the removal of impurities and the recovery of acetic acid.

[0124] Compared with the traditional treatment process, the present invention greatly reduces the difficulty of wastewater treatment, improves the operation efficiency, and achieves the requirements of acetic acid recovery and phosphorus removal.

[0125] The triple-effect separator 11 of the present invention has a larger volume of gas-liquid separation space, good gas-liquid separation effect, reduced secondary steam flow rate, and reduced mist entrainment. A demisting device is provided in the separator to enhance the purification effect of secondary steam and improve the effluent water quality.

[0126] The treatment system provided by the present invention has greater adaptability, strong resistance to water quality fluctuations, strong anti-scaling ability, high tolerance to organic matter in wastewater, and can ensure long-term safe, stable and effective operation.

[0127] The low concentration section adopts falling film heat exchanger, which has the advantages of small footprint, low investment, low energy consumption, high heat transfer efficiency, etc. The high concentration section adopts forced circulation process to force the liquid to flow, avoiding the deposition or scaling of impurities in the system, reducing the risk of system blockage, and is very suitable for evaporation systems with solid precipitation.

[0128] The technical solution provided by the present invention can achieve a high degree of automation by setting up an automatic control system, and can realize one-button start and stop, automatic liquid level control, automatic feeding and discharging, etc. It greatly reduces the requirements and work intensity of operators, and also ensures stable and safe operation of the system.

[0129] The steam heat energy in the present invention is utilized multiple times, thereby reducing costs, improving efficiency and saving energy.

[0130] In order to further illustrate the present invention, a system and method for treating acetic acid phosphorus-containing wastewater provided by the present invention are described in detail below in combination with embodiments, but it should not be understood as limiting the scope of protection of the present invention.

[0131] Example 1

[0132] Use Figure 1 The treatment system of acetic acid phosphorus wastewater shown includes:

[0133] The raw liquid tank 1 is used to store the raw liquid, i.e. acetic acid phosphorus-containing wastewater.

[0134] A feed pump 2 (centrifugal pump) is used to transport the raw liquid in the raw liquid tank 1 to the preheater 3.

[0135] Preheater 3; the preheater 3 is a tubular heat exchanger with a heat exchange tube diameter of 25 mm.

[0136] A first-effect heater 4, the liquid inlet of the first-effect heater 4 is connected to the liquid outlet of the preheater 3; a first-effect falling film circulation pump 6 (centrifugal pump), the first-effect falling film circulation pump 6 is used to transport the liquid evaporated and separated by the first-effect heater 4 to the first-effect heater 4, forming a first circulation loop ①;

[0137] The first-effect heater 4 includes a membrane cloth device, which uses a large-diameter membrane cloth with a diameter of 12 mm. In the first-effect heater 4, the inner diameter of the heat exchange tube is 32 mm. The feed liquid flows from top to bottom in a film-like state, and the thickness of the feed liquid film can be adjusted according to the concentration of the feed liquid, and is between 0.5 and 2 mm. The first-effect heater 4 is a tubular heat exchanger.

[0138] A first-effect separator 5; the secondary steam inlet of the first-effect separator 5 is connected to the secondary steam outlet of the first-effect heater 4; the liquid outlet at the bottom of the first-effect separator 5 is connected to the first circulation loop ①; the liquid discharge pipe outlet of the first-effect separator 5 is arranged at the liquid outlet of the first-effect heater 4 on the first circulation loop ①; the first-effect separator 5 is a gas-liquid separator.

[0139] A second-effect heater 7, wherein the secondary steam inlet of the second-effect heater 7 is connected to the secondary steam outlet of the first-effect separator 5; a second-effect falling film circulation pump 9 (centrifugal pump), wherein the second-effect falling film circulation pump 9 is used to transport the liquid after evaporation and separation in the second-effect heater 7 to the second-effect heater 7, so as to form a second circulation loop ②; the second-effect heater 7 is a tubular heat exchanger.

[0140] The second-effect heater 7 includes a film cloth device, which uses a large-diameter film cloth with a diameter of 12 mm. In the second-effect heater 7, the inner diameter of the heat exchange tube is 32 mm. The feed liquid flows from top to bottom in a film-like shape, and the thickness of the feed liquid film can be adjusted according to the feed liquid concentration, ranging from 0.5 to 2 mm. The second-effect heater 7 is a tubular heat exchanger.

[0141] On the first circulation loop ①, a branch ③ of the first circulation loop is arranged at the outlet of the first-effect falling film circulation pump 6, and the outlet of the branch is connected to the second circulation loop ②, so as to transport part of the slurry in the first-effect heater 4 to the second-effect heater 7 of the second circulation loop ②.

[0142] A second-effect separator 8; the secondary steam inlet of the second-effect separator 8 is connected to the secondary steam outlet of the second-effect heater 7; the liquid outlet at the bottom of the second-effect separator 8 is connected to the second circulation loop ②; the liquid discharge pipe outlet of the second-effect separator 8 is arranged at the liquid outlet of the second-effect heater 7 on the second circulation loop ②; the second-effect separator 8 is a gas-liquid separator.

[0143] A secondary steam outlet is arranged at the top of the second-effect separator 8, and two outlets are arranged in the secondary steam outlet pipe, the first outlet is connected to the secondary steam inlet of the No. 1 triple-effect heater 10-1, and the second outlet is connected to the secondary steam inlet of the No. 2 triple-effect heater 10-2; the secondary steam inlet of the No. 1 triple-effect heater 10-1 is arranged at the upper part of the side wall of the No. 1 triple-effect heater 10-1, and the secondary steam inlet of the No. 2 triple-effect heater 10-2 is arranged at the upper part of the side wall of the No. 2 triple-effect heater 10-2.

[0144] The triple-effect forced circulation pump 12 (axial flow pump) is used to transport the liquid in the triple-effect separator 11 to the No. 1 triple-effect heater 10-1 and the No. 2 triple-effect heater 10-2 in sequence, and then enter the triple-effect separator 11 to form a third circulation loop ④.

[0145] On the second circulation loop ②, a branch ⑤ of the second circulation loop is arranged at the outlet of the second-effect falling film circulation pump 9, and the outlet of the branch is connected to the third circulation loop ④, so as to transport part of the slurry in the second-effect heater 7 to the No. 2 triple-effect heater 10-2 of the third circulation loop ④.

[0146] In the No. 1 triple effect heater 10-1 and the No. 2 triple effect heater 10-2, the inner diameter of the heat exchange tube is 32 mm. The No. 1 triple effect heater 10-1 and the No. 2 triple effect heater 10-2 are both tubular heat exchangers.

[0147] The structure of the triple effect separator 11 is as follows Figure 2 As shown, including:

[0148] The through-barrel 11-2 (diameter 1900mm, height 4000mm);

[0149] An upper end cap 11-1 fixedly connected to the top of the cylinder 11-2 (the secondary steam outlet diameter of the upper end cap 11-1 is 426 mm, and the height of the upper end cap 11-1 is 1380 mm); the upper end cap 11-1 is cone-shaped; a demisting device is arranged inside the upper end cap 11-1 (the demisting device is a wire mesh demisting device); a secondary steam outlet is arranged at the top of the upper end cap;

[0150] A lower head 11-3 fixedly connected to the bottom of the cylinder 11-2 (the height of the lower head 11-3 is 1380 mm); the lower head 11-3 is an inverted cone; a circulating discharge port is arranged on the side wall of the lower head 11-3;

[0151] A circulating feed port is arranged at the lower end of the side wall of the cylinder 11-2.

[0152] A condenser 15 (plate heat exchanger) connected to the secondary steam outlet of the triple-effect separator 11 .

[0153] A gas-liquid separator 16 is connected to the outlet of the condenser 15 .

[0154] On the third circulation loop, a branch line ⑥ of the third circulation loop is arranged at the outlet of the triple-effect forced circulation pump 12, and the outlet of the branch line is connected to the evaporator processing unit through a discharge pump 13 (centrifugal pump).

[0155] The evaporation kettle processing unit includes a first evaporation kettle 14 - 1 and a second evaporation kettle 14 - 2 which are arranged in parallel.

[0156] A fresh water tank 17 connected to the liquid outlet of the gas-liquid separator 16 is used to store the treated water.

[0157] The method for treating acetic acid phosphorus-containing wastewater using the above treatment system comprises the following steps:

[0158] In the acetic acid phosphorus-containing wastewater, the mass concentration of acetic acid is 4%, the mass concentration of total phosphorus is 0.1%, and the mass concentration of ammonia nitrogen is 0.2%.

[0159] 1) Preheat the acetic acid phosphorus-containing wastewater to 40-60°C;

[0160] 2) Circulating and heating the preheated wastewater in a first-effect heater to evaporate, to obtain feed liquid and secondary steam; the feed liquid flows back to the first-effect heater via a first circulation loop, and the secondary steam enters a first-effect separator for gas-liquid separation; the feed liquid after gas-liquid separation flows back to the first circulation loop;

[0161] The temperature of the liquid in the heat exchange tube of the first-effect heater is 100-120°C;

[0162] 3) transporting the secondary steam after gas-liquid separation in the first-effect separator (at a rate of 20 to 30 m / s) to the second-effect heater;

[0163] 60% (calculated by mass content) of the feed liquid in the first circulation loop is transported to the second circulation loop, and circulated and heated with the secondary steam in the second-effect heater to evaporate, so as to obtain feed liquid and secondary steam; the feed liquid is refluxed to the second-effect heater via the second circulation loop, and the secondary steam enters the second-effect separator for gas-liquid separation; the feed liquid after gas-liquid separation in the second-effect separator is refluxed to the second circulation loop;

[0164] The temperature of the liquid in the heat exchange tube of the second-effect heater is 80-100°C;

[0165] 4) The secondary steam after gas-liquid separation in the second-effect separator is transported (at a rate of 20-30 m / s) to the No. 1 triple-effect heater and the No. 2 triple-effect heater respectively; the temperature of the feed liquid in the heat exchange tubes of the No. 1 triple-effect heater and the No. 2 triple-effect heater is 60-80° C.;

[0166] 50% (calculated by mass content) of the feed liquid in the second circulation loop is transported to the third circulation loop, and circulated and heated to evaporate with the secondary steam after gas-liquid separation in the second-effect separator to obtain feed liquid and secondary steam; the feed liquid is transported to the evaporator treatment unit for evaporation and concentration (evaporation temperature is 48-52°C); the secondary steam enters the three-effect separator for gas-liquid separation; the secondary steam after gas-liquid separation enters the condenser (flow rate is 1-2m / s) for condensation, and the gas and liquid are separated to obtain condensate, which is the treated water body.

[0167] According to the test, in the treated water (i.e. the condensate in the fresh water tank 17), the acetic acid recovery rate is not less than 90%, the phosphorus removal rate is not less than 95%, and the ammonia nitrogen removal rate can reach 70%.

[0168] Comparative Example 1

[0169] The difference from Example 1 is:

[0170] The triple-effect separator 11 is replaced by a conventional commercially available gas-liquid separator.

[0171] The remaining steps and parameters are the same as those in Example 1 to obtain treated water.

[0172] According to the test, the acetic acid recovery rate in the treated water does not exceed 70%, the phosphorus removal rate does not exceed 90%, and the ammonia nitrogen removal rate does not exceed 50%.

[0173] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A treatment system for acetic acid phosphorus-containing wastewater, comprising: Preheater; A first-effect heater, the liquid inlet of the first-effect heater is connected to the liquid outlet of the preheater; a first-effect falling film circulation pump, the first-effect falling film circulation pump is used to transport the liquid evaporated and separated by the first-effect heater to the first-effect heater, forming a first circulation loop; A first-effect separator; the secondary steam inlet of the first-effect separator is connected to the secondary steam outlet of the first-effect heater; the liquid outlet of the first-effect separator is connected to the first circulation loop; A second-effect heater, wherein the secondary steam inlet of the second-effect heater is connected to the secondary steam outlet of the first-effect separator; a second-effect falling film circulation pump, wherein the second-effect falling film circulation pump is used to transport the feed liquid after evaporation and separation in the second-effect heater to the second-effect heater to form a second circulation loop; On the first circulation loop, a branch of the first circulation loop is arranged at the outlet of the first-effect falling film circulation pump, and the outlet of the branch is connected to the second circulation loop, so as to transport part of the liquid in the first-effect heater to the second circulation loop; A second-effect separator; the secondary steam inlet of the second-effect separator is connected to the secondary steam outlet of the second-effect heater; the feed liquid outlet of the second-effect separator is connected to the second circulation loop; A secondary steam outlet is provided at the top of the second-effect separator, and the secondary steam outlet pipeline is provided with two outgoing paths, the first outgoing path is connected to the secondary steam inlet of the No. 1 triple-effect heater, and the second outgoing path is connected to the secondary steam inlet of the No. 2 triple-effect heater; A three-effect forced circulation pump, which is used to transport the liquid in the three-effect separator to the No. 1 three-effect heater and the No. 2 three-effect heater in sequence, and then enter the three-effect separator to form a third circulation loop; On the second circulation loop, a branch of the second circulation loop is arranged at the outlet of the second-effect falling film circulation pump, and the outlet of the branch is connected to the third circulation loop, so as to transport part of the feed liquid in the second-effect heater to the third circulation loop; a condenser connected to the secondary steam outlet of the triple-effect separator; a gas-liquid separator connected to the outlet of the condenser; On the third circulation loop, a branch of the third circulation loop is arranged at the outlet of the triple-effect forced circulation pump, and the outlet of the branch is connected to the evaporator processing unit.

2. The processing system according to claim 1, characterized in that The triple-effect separator comprises: Through the barrel; An upper end cap fixedly connected to the top of the cylinder; the upper end cap is cone-shaped; a demisting device is arranged inside the upper end cap; a secondary steam outlet is arranged at the top of the upper end cap; A lower head fixedly connected to the bottom of the cylinder; the lower head is in the shape of an inverted cone; a circulating discharge port is arranged on the side wall of the lower head; A circulating feed port is arranged at the lower end of the side wall of the cylinder.

3. The processing system according to claim 2, characterized in that The diameter of the cylinder is 1000-2000 mm and the height is 3000-6000 mm; The secondary steam outlet diameter of the upper head is 200-600 mm; the height of the upper head is 800-2000 mm; The height of the lower head is 800-2000 mm; The demisting device is a wire mesh demisting device.

4. The processing system according to claim 1, characterized in that The preheater is a tubular heat exchanger, and the diameter of the heat exchange tube is 23-27 mm.

5. The processing system according to claim 1, characterized in that The single-effect heater includes a membrane cloth device, which uses a large-diameter membrane cloth with a diameter of 11 to 13 mm; In a single-effect heater, the inner diameter of the heat exchange tube is 30 to 34 mm.

6. The processing system according to claim 1, characterized in that The two-effect heater includes a membrane cloth device, which uses a large-diameter membrane cloth with a diameter of 11 to 13 mm; In the two-effect heater, the inner diameter of the heat exchange tube is 30 to 34 mm.

7. The processing system according to claim 1, characterized in that The inner diameter of the heat exchange tube of the No. 1 triple-effect heater 10-1 is 30-34 mm; The inner diameter of the heat exchange tube of the No. 2 triple-effect heater 10-2 is 30-34 mm.

8. A method for treating acetic acid phosphorus-containing wastewater using the treatment system according to any one of claims 1 to 7, comprising the following steps: A) Preheating the acetic acid phosphorus wastewater to 40-60°C; B) circulating the preheated wastewater in a first-effect heater for heating and evaporation to obtain feed liquid and secondary steam; the feed liquid flows back to the first-effect heater via a first circulation loop, and the secondary steam enters a first-effect separator for gas-liquid separation; the feed liquid after gas-liquid separation flows back to the first circulation loop; C) transporting the secondary steam after gas-liquid separation in the first-effect separator to the second-effect heater; Part of the feed liquid in the first circulation loop is transported to the second circulation loop, and circulated and heated with the secondary steam in the second-effect heater to evaporate, so as to obtain feed liquid and secondary steam; the feed liquid is refluxed to the second-effect heater via the second circulation loop, and the secondary steam enters the second-effect separator for gas-liquid separation; the feed liquid after gas-liquid separation in the second-effect separator is refluxed to the second circulation loop; D) transporting the secondary steam after gas-liquid separation in the second-effect separator to triple-effect heater No. 1 and triple-effect heater No. 2 respectively; Part of the feed liquid in the second circulation loop is transported to the third circulation loop, and circulated and heated to evaporate with the secondary steam after gas-liquid separation in the second-effect separator to obtain feed liquid and secondary steam; the feed liquid is transported to the evaporator treatment unit for evaporation and concentration; the secondary steam enters the three-effect separator for gas-liquid separation; the secondary steam after gas-liquid separation enters the condenser for condensation, and the gas and liquid are separated to obtain condensate, which is the treated water body.

9. The method according to claim 8, characterized in that The temperature of the liquid in the heat exchange tube of the first-effect heater is 100-120°C; The temperature of the liquid in the heat exchange tube of the second-effect heater is 80-100°C; The temperature of the liquid in the heat exchange tubes of the No. 1 triple-effect heater and the No. 2 triple-effect heater is 60-80°C; The concentrated liquid is further evaporated and concentrated in the evaporator treatment unit at an evaporation temperature of 48-52°C.

10. The method according to claim 8, characterized in that The secondary steam after gas-liquid separation in the first-effect separator is transported to the second-effect heater at a rate of 20 to 30 m / s; The secondary steam after gas-liquid separation in the second-effect separator is transported to the No. 1 triple-effect heater and the No. 2 triple-effect heater at a rate of 20 to 30 m / s; The secondary steam separated from the gas and liquid by the triple-effect separator is transported to the condenser at a flow rate of 1 to 2 m / s.

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