CN110950512B - System and method for treating excess biochemical sludge - Google Patents

Abstract

The present disclosure relates to a system and method for treating excess biochemical sludge, the system comprising a raw material inlet, a mixing reaction device, a flash evaporation device, a solid-liquid separation device, a sewage outlet and a sludge outlet; the mixing reaction equipment comprises a shell with a feed inlet and a discharge outlet, and a stirring device is arranged in the shell; the flash evaporation equipment comprises an inlet, a liquid outlet and a gas outlet, wherein the raw material inlet is communicated with a feed inlet of the mixed reaction equipment, a discharge outlet of the mixed reaction equipment is communicated with an inlet of the flash evaporation equipment, a liquid outlet of the flash evaporation equipment is communicated with an inlet of the solid-liquid separation equipment, and a liquid outlet and a solid outlet of the solid-liquid separation equipment are respectively communicated with a sewage outlet and a sludge outlet. The system is provided with the stirring device in the mixing reaction equipment, so that the efficient mixing of a sludge liquid-solid heterogeneous system is realized, and the sludge reduction reaction process is enhanced; meanwhile, flash evaporation equipment is arranged in the system to further strengthen the sludge reduction reaction, so that the efficiency of the reduction reaction is improved.

Description

System and method for treating excess biochemical sludge

Technical Field

The present disclosure relates to the field of solid waste reduction and recycling applications, and in particular, to a system and method for treating excess biochemical sludge.

Background

In recent years, the environment-friendly industry in China is rapidly developed, the sewage treatment capacity and the treatment rate are rapidly improved, and by the end of 9 months in 2016, the 3976 base of a sewage treatment plant is built nationally, and the daily sewage treatment capacity reaches 1.7 hundred million cubic meters, which definitely plays a significant role in protecting the water environment. At the same time, however, the sewage treatment process generates a large amount of surplus activated sludge, 130 kilocubic meters of the surplus activated sludge with 98w% of water is generated every day, and the annual output of the surplus activated sludge reaches 4.75 hundred million cubic meters, based on the amount of the surplus activated sludge generated by the current sewage treatment. According to the city population base of China, even if only 1 hundred million people of sewage is treated, 25000 tons of sludge cakes with the solid content of 20% are produced every day, and if the sludge cakes are piled up according to the maximum of 2 meters, 600 international standard football stadiums are needed each year.

The reason for increasingly highlighting the problem of sludge is that after long-term groping and testing of a batch of sewage treatment plants built in early stage, a good disposal scheme is not found yet, and the resources for stacking, discarding and landfill are less and less, the supervision of various environmental protection departments is enhanced, while the sewage treatment in China is developing and expanding at an unprecedented speed, and the disposal of sludge becomes a troublesome problem.

For the sludge treatment mode, the most effective reduction mode is heat drying, and the water content can be reduced from 70% to below 10%. In fact, the final solid content of the sludge can vary between 60% and 95% depending on the final disposal requirements, in which case the reduction of the sludge is more than 60% and is more reasonable in terms of cost and safety. The cheapest reduction mode is composting, and the water content can be reduced from more than 70% to less than 30% by evaporating heat generated by fermenting organic matters of sludge. However, the efficiency is obviously lower than that of the former, and the method is difficult to apply to large cities due to the large occupied area and the odor treatment difficulty. The most thorough reduction mode is incineration, and the reduction is carried out to less than 15 percent of the original wet mud volume. But this is also the most expensive treatment scheme and generally must be considered in parallel with heat drying. The technology has a certain effect on the reduction of the residual activated sludge, but has obvious defects, such as the desiccation landfill technology occupies a large amount of land, has pollution risks on underground water, causes heavy metal pollution and biological pollution on the soil in the using process, and the incineration technology has high equipment requirements and high treatment cost and can generate harmful gas polluting the atmosphere.

Patent CN 105859088 discloses a supercritical sludge treatment system and method, in which sludge slurry is subjected to combustion reaction in a reactor by adding an oxidizing agent and carbon-containing organic matter powder, so that the reaction conditions are very severe.

Disclosure of Invention

The system and the method are simple in structure, convenient to operate, high in treatment efficiency and good in effect on the residual biochemical sludge.

In order to achieve the above object, a first aspect of the present disclosure provides a system for treating surplus biochemical sludge, the system comprising a raw material inlet, a mixing reaction device, a flash evaporation device, a solid-liquid separation device, a sewage outlet, and a sludge outlet; the mixing reaction equipment comprises a shell with a feed inlet and a discharge outlet, and a stirring device is arranged in the shell; the flash evaporation equipment comprises an inlet, a liquid outlet and a gas outlet, the raw material inlet is communicated with a feed inlet of the mixing reaction equipment, a discharge outlet of the mixing reaction equipment is communicated with the inlet of the flash evaporation equipment, the liquid outlet of the flash evaporation equipment is communicated with the inlet of the solid-liquid separation equipment, and the liquid outlet and the solid outlet of the solid-liquid separation equipment are respectively communicated with the sewage outlet and the sludge outlet.

Optionally, the flash evaporation device comprises a pressure reducer and a flash evaporation tank which are sequentially connected, the flash evaporation tank comprises a liquid outlet and a gas outlet, a discharge port of the mixing reaction device is communicated with an inlet of the pressure reducer, and a liquid outlet of the flash evaporation tank is communicated with an inlet of the solid-liquid separation device.

Optionally, the system further comprises a raw material buffer tank, wherein a liquid inlet of the raw material buffer tank is communicated with the raw material inlet, and an outlet of the raw material buffer tank is communicated with the feeding port.

Optionally, the inlet and the outlet of the raw material buffer tank are respectively positioned at the top and the bottom of the tank body, a gas distributor is arranged at the bottom of the raw material buffer tank, and the gas outlet of the flash evaporation device is communicated with the inlet of the gas distributor.

Optionally, the stirring device is selected from one or more of an axial flow paddle, a radial flow paddle, a circumferential flow paddle and a combined paddle.

Optionally, the stirring device is selected from a turbine stirrer, a paddle stirrer, a propeller stirrer, a hinged turbine stirrer, a cloth Lu Majin stirrer, an anchor stirrer, a screw stirrer or a ribbon stirrer, or a combination of two or three or four thereof.

Optionally, the solid-liquid separation device comprises a cyclone separator and a settling tank, wherein an inlet of the cyclone separator is communicated with a discharge port of the mixing reaction device, a liquid outlet of the cyclone separator is communicated with the sewage outlet, a solid outlet of the cyclone separator is communicated with an inlet of the settling tank, and a liquid outlet and a solid outlet of the settling tank are respectively communicated with the sewage outlet and the sludge outlet.

Optionally, the solid-liquid separation equipment comprises a settling tank, a cyclone separator is arranged at the upper part of the tank body of the settling tank, an inlet of the cyclone separator passes through the settling tank and is communicated with a discharge port of the mixing reaction equipment, a solid outlet of the cyclone separator is communicated with the inside of the tank body of the settling tank, a liquid outlet of the cyclone separator and a liquid outlet of the settling tank are respectively communicated with the sewage outlet, and a solid outlet of the settling tank is communicated with the sludge outlet.

Optionally, the system further comprises an auxiliary inlet in communication with the feed inlet of the mixing reaction apparatus.

Optionally, the system comprises a feed pump disposed between the feedstock inlet and the mixing reaction apparatus.

Optionally, the system comprises a heat exchanger disposed between the feedstock inlet and the mixing reaction apparatus.

A second aspect of the present disclosure provides a method of treating excess biochemical sludge using the system of the first aspect of the present disclosure.

A third aspect of the present disclosure provides a method of treating excess biochemical sludge, the method comprising the steps of: s1, under the condition of the reduction reaction, under the stirring state, carrying out the reduction reaction of the residual biochemical sludge and the auxiliary agent in the mixed reaction equipment to obtain a reduction reaction product; s2, flashing the subtracted reaction product to obtain flash steam and a reaction product after flashing; s3, carrying out solid-liquid separation on the reaction product after flash evaporation to obtain sewage and sludge respectively.

Optionally, the method comprises: and enabling the residual biochemical sludge and the flash steam to enter the mixing reaction equipment with the auxiliary agent for carrying out the reduction reaction after heat exchange.

Optionally, the subtractive reaction conditions comprise: the reaction temperature is 80-300 ℃; the reaction pressure is 0.05MPa to 10.0MPa; the addition amount of the auxiliary agent is that the pH value of the mixed material in the mixed reaction equipment is 8-14; the residence time of the residual biochemical sludge in the mixed reaction equipment is 0.1 h-6.0 h.

Optionally, the solid content of the residual biochemical sludge is 1-10 w%.

Optionally, the auxiliary agent is an alkaline auxiliary agent, and the alkaline auxiliary agent is at least one selected from sodium hydroxide, potassium hydroxide, sodium oxide, sodium peroxide, potassium oxide, potassium peroxide, sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate.

Optionally, the stirring speed in the mixing reaction equipment is 20 rpm-500 rpm.

Optionally, the flash evaporation is operated at a pressure of 0MPa to 1.0MPa and at a temperature of 100 ℃ to 200 ℃.

Optionally, the solid-liquid separation comprises cyclone separation and gravity sedimentation in sequence.

The system and the method for treating the residual biochemical sludge have the beneficial effects that:

(1) According to the system and the method for treating the excess biochemical sludge, provided by the invention, the stirring device is purposefully arranged, so that the efficient mixing of a sludge liquid-solid heterogeneous system is realized, the sludge reduction reaction process is further strengthened, and the digestion efficiency is ensured.

(2) The system and the method for treating the excess biochemical sludge strengthen the sludge reduction reaction by flash vaporization and promote the sludge reduction reaction.

(3) The system for treating the residual biochemical sludge has the advantages of simple structure, convenient operation, mild conditions, cheap and easily obtained reagents and the like, and is convenient to popularize and apply.

Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.

Drawings

The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate the disclosure and together with the description serve to explain, but do not limit the disclosure. In the drawings:

FIG. 1 is a process flow diagram of one embodiment of the system and method of treating excess biochemical sludge of the present disclosure.

Description of the reference numerals

1-raw material inlet, 2-auxiliary agent inlet, 3-raw material buffer tank, 4-mixed feeding, 5-feeding pump, 6-heat exchanger, 7-stirring device, 8-mixed reaction equipment, 9-reactor discharging, 10-pressure reducer, 11-flash tank, 12-reaction sludge, 13-circulating steam, 14-cyclone separator, 15-cyclone sludge, 16-cyclone clear liquid, 17-settling tank, 18-sludge outlet, 19-settling clear liquid and 20-sewage outlet.

Detailed Description

Specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.

In this disclosure, unless otherwise indicated, terms of orientation such as "upper and lower" are used to refer generally to the upper and lower directions of the device in normal use, and refer specifically to the orientation of the drawing of fig. 1. "inner and outer" are with respect to the contour of the device itself.

As shown in fig. 1, a first aspect of the present disclosure provides a system for treating surplus biochemical sludge, the system comprising a raw material inlet 1, a mixing reaction apparatus, a flash evaporation apparatus, a solid-liquid separation apparatus, a sewage outlet 20, and a sludge outlet 18; the mixing reaction equipment comprises a shell with a feed inlet and a discharge outlet, and a stirring device 7 is arranged in the shell; the flash evaporation equipment comprises an inlet, a liquid outlet and a gas outlet, the raw material inlet 1 is communicated with a feed inlet of the mixed reaction equipment, a discharge outlet of the mixed reaction equipment is communicated with an inlet of the flash evaporation equipment, a liquid outlet of the flash evaporation equipment is communicated with an inlet of the solid-liquid separation equipment, and a liquid outlet and a solid outlet of the solid-liquid separation equipment are respectively communicated with a sewage outlet 20 and a sludge outlet 18.

According to the system for treating the surplus biochemical sludge, the stirring device 7 is arranged in the mixing reaction equipment, so that efficient mixing of a sludge liquid-solid heterogeneous system is realized, the sludge reduction reaction process is further reinforced, and the digestion efficiency is ensured; meanwhile, flash evaporation equipment is arranged in the system, so that sludge reduction reaction can be enhanced. The system has simple structure, convenient operation and convenient popularization and application.

According to the present disclosure, the mixing reaction apparatus provided with the stirring device 7 may be of a conventional kind in the art, such as a stirred tank, the stirring device 7 may also be of a kind well known to those skilled in the art, and the stirring device 7 may be selected from one or more of an axial flow paddle, a radial flow paddle, a circumferential flow paddle and a combination paddle.

In order to further enhance the stirring mixing effect, the stirring device 7 may be selected from a turbine stirrer, a paddle stirrer, a propeller stirrer, a hinge-opening turbine stirrer, a cloth Lu Majin stirrer, an anchor stirrer, a screw stirrer or a ribbon stirrer, or a combination of two or three or four thereof.

The arrangement of the stirring device 7 in the mixing reaction device may be conventional in the art, which is not described herein, and further, in order to improve the popularity of the materials in the mixing reaction device and improve the mixing efficiency, a plurality of baffles may be disposed in the mixing reaction device, and the baffles may be conventional in the art, for example, vertical baffles, further, the baffles may be disposed near the inner wall of the housing, and further, it is preferable that the baffles satisfy the condition of full baffles.

In order to achieve better flash enhanced reaction, in one embodiment of the present disclosure, as shown in fig. 1, the flash evaporation apparatus may include a pressure reducer 10 and a flash tank 11 connected in sequence, the flash tank 11 may include a liquid outlet and a gas outlet, the discharge port of the mixing reaction apparatus 8 may be in communication with the inlet of the pressure reducer 10, and the liquid outlet of the flash tank 11 may be in communication with the inlet of the solid-liquid separation apparatus.

To facilitate adjustment of the feed rate, in one embodiment of the present disclosure, as shown in fig. 1, the system may further include a feed buffer tank 3, the liquid inlet of the feed buffer tank 3 may be in communication with the feed inlet, and the outlet may be in communication with the feed inlet of the mixing reaction apparatus 8.

Further, to improve the heat utilization efficiency of the system and reduce the fouling of the heat exchanger, in one embodiment of the present disclosure, the liquid inlet and outlet of the feedstock buffer tank 3 may be located at the top and bottom of the tank body, respectively, so that the feedstock enters and exits from the top and from the bottom, and the gas outlet of the flash apparatus may be in communication with the feedstock buffer tank 3 so that the flash gas exchanges heat with the feedstock; further, in order to make the heat exchange sufficiently effective, the bottom of the raw material buffer tank 3 may be provided with a gas distributor, and the gas outlet of the flash evaporation device may be communicated with the inlet of the gas distributor, so that the circulating steam enters the raw material buffer tank from the bottom and contacts the raw material in countercurrent to strengthen the heat exchange.

The solid-liquid separation apparatus may be of a kind conventional in the art in light of the present disclosure. To further enhance the effect of solid-liquid separation of the abatement reaction products, in one embodiment of the disclosure, as shown in fig. 1, the solid-liquid separation apparatus may include a cyclone 14 and a settling tank 17, the inlet of the cyclone 14 may be in communication with the discharge port of the mixing reaction apparatus, the liquid outlet of the cyclone 14 may be in communication with the effluent outlet 20, the solid outlet of the cyclone 14 may be in communication with the inlet of the settling tank 17, and the liquid outlet and the solid outlet of the settling tank 17 may be in communication with the effluent outlet 20 and the sludge outlet 18, respectively. In this embodiment, the material is separated by cyclone 14, and the separated solid phase is further dewatered and concentrated by settling tank 17 to obtain sludge with greatly reduced water content.

The solid-liquid separation apparatus may be of a kind conventional in the art in light of the present disclosure. To further enhance the effect of solid-liquid separation of the abatement reaction products, in one embodiment of the disclosure, as shown in fig. 1, the solid-liquid separation apparatus may include a cyclone 14 and a settling tank 17, the inlet of the cyclone 14 may be in communication with the discharge port of the mixing reaction apparatus, the liquid outlet of the cyclone 14 may be in communication with the effluent outlet 20, the solid outlet of the cyclone 14 may be in communication with the inlet of the settling tank 17, and the liquid outlet and the solid outlet of the settling tank 17 may be in communication with the effluent outlet 20 and the sludge outlet 18, respectively. In this embodiment, the material is separated by the cyclone 14, and the separated cyclone sludge 15 is further settled, dehydrated and concentrated by the settling tank 17, so as to obtain sludge with greatly reduced water content.

According to the present disclosure, the adjuvant for performing the sludge reduction reaction may be introduced into the mixing reaction apparatus 8 together with the surplus biochemical sludge, and in one embodiment of the present disclosure, the system may further include an adjuvant inlet 2, and the adjuvant inlet 2 may be communicated with a feed inlet of the mixing reaction apparatus, so that the adjuvant and the biochemical sludge are introduced into the mixing reaction apparatus from the adjuvant inlet 2 and the raw material inlet 1, respectively, so as to separately control the feed amounts of both. In embodiments of the system of the present disclosure that include a feedstock buffer tank, the feedstock inlet 1 and the adjuvant inlet 2 may be in communication with the inlets of the feedstock buffer tank, respectively.

In one embodiment of the present disclosure, to facilitate feeding, the system may include a feed pump 5, and the feed pump 5 may be disposed between the raw material inlet 1 and the mixing reaction apparatus 8. In embodiments of the system of the present disclosure that include a feedstock buffer tank, the feed pump 5 may be positioned between the feedstock buffer tank and the mixing reaction apparatus 8.

In order to facilitate improved sludge abatement reaction efficiency within the mixing reaction apparatus, in one embodiment of the disclosure, the system may include a heat exchanger 6 for exchanging heat with feedstock entering the system, the heat exchanger 6 may be disposed between the feedstock inlet 1 and the mixing reaction apparatus 8. In embodiments where the system of the present disclosure includes a feedstock buffer tank, the heat exchanger 6 may be disposed between the feedstock buffer tank and the mixing reaction device 8.

A second aspect of the present disclosure provides a method of treating excess biochemical sludge using the system of the first aspect of the present disclosure.

As shown in fig. 1, in one embodiment of the present disclosure, a method of performing a treatment reaction of a residual biochemical sludge material in a system of the present disclosure may include: the method comprises the steps that residual biochemical sludge raw materials and auxiliary agents respectively enter a system from a raw material inlet 1 and an auxiliary agent inlet 2, mixed raw materials 4 are obtained after heat exchange with circulating steam 13 from flash evaporation equipment in a raw material buffer tank 3, the mixed raw materials 4 enter a feed inlet of a mixing reaction equipment 8 after pressure boosting of a feed pump 5 and heat exchange of a heat exchanger 6, the mixed raw materials enter a pressure reducer 10 and a flash evaporation tank 11 in sequence for flash evaporation after full stirring and mixing reaction at the inner diameter of the mixing reaction equipment 8, the flash evaporation steam returns to the raw material buffer tank 3 as the circulating steam 13 to exchange heat with the raw material sludge, the reaction sludge 12 obtained after flash evaporation enters a cyclone separator 14 to remove most of water, the separated cyclone sludge 15 is subjected to further sedimentation, dehydration and concentration through a sedimentation tank 17, finally sludge with greatly reduced water content is obtained from a sludge outlet 18, further dehydration and concentration treatment is carried out, and a cyclone clear liquid 16 separated by the cyclone separator 14 and a sedimentation clear liquid 19 separated by the sedimentation tank 17 are subjected to decontamination water treatment through a sewage outlet 20.

As shown in fig. 1, a third aspect of the present disclosure provides a method of treating surplus biochemical sludge, the method comprising the steps of: s1, under the condition of the reduction reaction, under the stirring state, carrying out the reduction reaction of the residual biochemical sludge and the auxiliary agent in the mixed reaction equipment to obtain a reduction reaction product; s2, flashing the subtracted reaction product to obtain flash steam and a reaction product after flashing; s3, carrying out solid-liquid separation on the reaction product after flash evaporation to obtain sewage and sludge respectively.

The method of the disclosure realizes the efficient mixing of a sludge liquid-solid heterogeneous system by carrying out strong stirring and mixing on the raw materials of the reduction reaction containing the residual biochemical sludge and the auxiliary agent, and the reinforcement reduction reaction is carried out; meanwhile, the method combines flash vaporization to strengthen the sludge reduction reaction, so that the efficiency of the reduction reaction is improved; the method has the advantages of convenient operation, mild conditions, cheap and easily available reagents, and the like, and is convenient to popularize and apply.

According to the disclosure, in order to improve the heat utilization efficiency, preferably, the method may include performing the abatement reaction with the auxiliary agent after exchanging heat between the residual biochemical sludge and the flash steam, so as to fully utilize the heat of the flash steam and save external energy.

The meaning of the abatement reaction of excess biochemical sludge is well known to those skilled in the art in light of the present disclosure, and the conditions under which the abatement reaction is carried out may vary widely, with preferred abatement reaction conditions including: the reaction temperature may be 80 to 300 ℃, preferably 100 to 250 ℃; the reaction pressure may be 0.05MPa to 10.0MPa, preferably 0.1MPa to 5.0MPa; the addition amount of the auxiliary agent can be such that the pH value of the mixed material in the mixed reaction equipment is 8-14, preferably 10-13; the residence time of the excess biochemical sludge in the mixing reaction apparatus may be 0.1 to 6.0 hours, preferably 0.5 to 4.0 hours.

According to the present disclosure, the conditions under which the product from the abatement reaction is flashed may vary over a wide range, and preferred flashing conditions may include: the operating pressure is 0 MPa-1.0 MPa, and the operating temperature is 100-200 ℃.

According to the present disclosure, the surplus biochemical sludge to be treated may be municipal sludge or may be derived from industrial sludge, wherein the solid content may be 1 to 10% by weight.

According to the present disclosure, the adjuvant may be a conventional adjuvant for performing a sludge reduction reaction, preferably an alkaline adjuvant, further preferably at least one of sodium hydroxide, potassium hydroxide, sodium oxide, sodium peroxide, potassium oxide, potassium peroxide, sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate.

The mixing reaction apparatus for carrying out the abatement reaction according to the present disclosure may be of a kind conventional in the art, such as a stirred tank, in which stirring means may be provided, such as one or more selected from axial paddles, radial paddles, circumferential paddles and composite paddles. In order to further improve the stirring and mixing effects, the stirring device can be one or more selected from a flat blade type stirrer, a turbine type stirrer, a three-blade back-sweep stirrer, a propeller type stirrer, a spiral impeller stirrer, an anchor type stirrer and a frame type stirrer.

According to the present disclosure, the stirring speed in the mixing reaction apparatus may vary within a wide range, and in order to further promote the mixing of the surplus biochemical sludge with the auxiliary agent and enhance the reduction reaction process, the stirring speed in the mixing reaction apparatus may be 20rpm to 500rpm, preferably 50 to 200rpm.

According to the disclosure, the method for performing solid-liquid separation may be conventional in the art, such as sedimentation separation, centrifugal separation, and the like, preferably, in order to improve separation efficiency, the solid-liquid separation in the method of the disclosure may sequentially include cyclone separation and gravity sedimentation, so that most of water is separated from the material through the cyclone separation, and the separated solid phase is further dehydrated and concentrated through gravity sedimentation, so that the water content is greatly reduced. The apparatus and methods of operation for performing cyclonic separation and gravity settling may be conventional in the art and are not described in detail herein. The sludge obtained after gravity sedimentation can also be further dehydrated and concentrated.

The mixing reaction apparatus of the present disclosure is further illustrated by the following examples, but the present disclosure is not so limited. The experimental raw materials in the following examples and comparative examples were surplus biochemical sludge (solid content: 3 w%) obtained from a municipal sewage treatment plant in Tianjin city, and the alkaline auxiliary agent was a 30% sodium hydroxide solution. The change condition of suspended substances SS in the raw materials before and after the reaction and the processed materials is mainly examined, the analysis method of the SS is carried out according to the national standard GB 11901-89, and the analysis result of the raw materials is shown in the table 1.

Example 1

In the embodiment, the device and the method for treating the excess biochemical sludge are adopted to carry out reduction treatment on the sludge raw material, wherein the raw material is the municipal sludge raw material, and the reactor and the system shown in the figure 1 are adopted.

The raw materials enter from bottom to top, the pH=13 of the feed is adjusted by adding alkali liquor, and the feed temperature is 35 ℃ at normal temperature. The inlet temperature of the reactor is 180 ℃, the outlet pressure of the reactor is 1.5MPa, and the apparent residence time of the materials in the reaction is 2h. The stirrer was provided with two layers of stirring paddles (paddle stirrer) at 500rpm. The material at the outlet of the reactor is subjected to flash evaporation treatment through a pressure reducer and a flash tank, the operating pressure of the flash tank is 0.1MPa, the temperature after flash evaporation is 120 ℃, the vaporization rate is 10%, the generated steam is directly contacted with the raw material for mixed heat exchange, and the temperature after heat exchange is 99 ℃. The product obtained from the liquid outlet of the flash tank is subjected to liquid-solid separation through a liquid-solid cyclone, the sludge extracted from the bottom of the cyclone enters a gravity settling tank for further separation, the top supernatant is extracted after being mixed with the supernatant discharged from the settling tank, and the residence time at the bottom of the settling tank is 10min. The reactor outlet materials were taken and analyzed, the results are shown in Table 1, the results of the sludge water content produced at the bottom of the settling tank are shown in Table 2, and the measurement results of the total heat consumption of the preheater are shown in Table 3.

Comparative example 1

The conventional reactor is adopted to treat the municipal sludge raw material, and the reactor is up-in, down-out, and has no stirring equipment and flash evaporation equipment. The feed ph=13 was controlled by adding a certain amount of sodium hydroxide solution to the sludge feed. Heating and controlling the reaction temperature to 180 ℃, and controlling the pressure of the reactor to 1.5MPa, wherein the reaction residence time is 2h. The amount of residual sludge in the reacted material was analyzed, and the results are shown in Table 1. The reactor outlet materials were subjected to gravity settling for 10min, and the sludge water content results obtained from the bottom of the tank are shown in Table 2.

Comparative example 2

The sludge feedstock was subjected to abatement using the method and system of example 1, using the same feedstock and reaction conditions as in example 1, except that the system did not include flash evaporation equipment. The reactor outlet materials were analyzed and the results are shown in Table 1, and the results of the sludge water content produced at the bottom of the settling tank are shown in Table 2.

TABLE 1

Project	Raw materials	Comparative example 1	Comparative example 2	Example 1
					SS，g/L	22.53	10.08	9.95	9.24

TABLE 2

Project	Comparative example 1	Comparative example 2	Example 1
				Tank bottom sludge water content, w%	68	65	62

TABLE 3 Table 3

Project	Comparative example 2	Example 1
			Heating/heat exchange power consumption, kW/t feed	170.3	98.9

The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.

In addition, the specific features described in the above embodiments may be combined in any suitable manner without contradiction. The various possible combinations are not described further in this disclosure in order to avoid unnecessary repetition.

Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.

Claims (13)

1. A system for treating excess biochemical sludge, which is characterized by comprising a raw material inlet (1), a mixing reaction device (8), a flash evaporation device, a solid-liquid separation device, a raw material buffer tank (3), a feed pump (5), a sewage outlet (20) and a sludge outlet (18);

the mixing reaction equipment (8) comprises a shell with a feed inlet and a discharge outlet, and a stirring device (7) is arranged in the shell;

the flash evaporation equipment comprises a pressure reducer (10) and a flash evaporation tank (11) which are sequentially connected, the flash evaporation tank (11) comprises a liquid outlet and a gas outlet, a discharge port of the mixed reaction equipment (8) is communicated with an inlet of the pressure reducer (10), and the liquid outlet of the flash evaporation tank (11) is communicated with an inlet of the solid-liquid separation equipment; the liquid outlet and the solid outlet of the solid-liquid separation equipment are respectively communicated with the sewage outlet (20) and the sludge outlet (18);

the liquid inlet of the raw material buffer tank (3) is communicated with the raw material inlet (1), and the outlet is communicated with the feeding port; the inlet and the outlet of the raw material buffer tank (3) are respectively positioned at the top and the bottom of the tank body, a gas distributor is arranged at the bottom of the raw material buffer tank (3), and the gas outlet of the flash evaporation equipment is communicated with the inlet of the gas distributor;

the solid-liquid separation equipment comprises a cyclone separator (14) and a settling tank (17), wherein the inlet of the cyclone separator (14) is communicated with a discharge port of the mixing reaction equipment (8), the liquid outlet of the cyclone separator (14) is communicated with the sewage outlet (20), the solid outlet of the cyclone separator (14) is communicated with the inlet of the settling tank (17), and the liquid outlet and the solid outlet of the settling tank (17) are respectively communicated with the sewage outlet (20) and the sludge outlet (18);

the feed pump (5) is arranged between the raw material inlet (1) and the mixing reaction equipment (8);

the system further comprises an auxiliary inlet (2), the auxiliary inlet (2) being in communication with the feed inlet of the mixing reaction apparatus (8).

2. The system according to claim 1, characterized in that the stirring device (7) is selected from one or several of axial paddles, radial paddles, circumferential paddles and composite paddles.

3. The system according to claim 1, characterized in that the stirring device (7) is selected from turbine-type stirrer, paddle-type stirrer, propeller-type stirrer, flap-open turbine-type stirrer, cloth Lu Majin-type stirrer, anchor-type stirrer, screw-type stirrer or ribbon-type stirrer, or a combination of two or three or four thereof.

4. The system according to claim 1, characterized in that it comprises a heat exchanger (6), said heat exchanger (6) being arranged between the raw material inlet (1) and the mixing reaction device (8).

5. A method of treating excess biochemical sludge using the system according to any one of claims 1 to 4.

6. A method of treating excess biochemical sludge using the system of any one of claims 1 to 4, the method comprising the steps of:

s1, under the condition of the reduction reaction, under the stirring state, carrying out the reduction reaction of the residual biochemical sludge and the auxiliary agent in the mixed reaction equipment to obtain a reduction reaction product;

s2, flashing the subtracted reaction product to obtain flash steam and a reaction product after flashing;

s3, carrying out solid-liquid separation on the reaction product after flash evaporation to obtain sewage and sludge respectively.

7. The method according to claim 6, characterized in that the method comprises: and enabling the residual biochemical sludge and the flash steam to enter the mixing reaction equipment with the auxiliary agent for carrying out the reduction reaction after heat exchange.

8. The method of claim 6, wherein the subtractive reaction conditions comprise: the reaction temperature is 80-300 ℃; the reaction pressure is 0.05-10.0 MPa; the addition amount of the auxiliary agent is that the pH value of the mixed material in the mixed reaction equipment is 8-14; the residence time of the residual biochemical sludge in the mixed reaction equipment is 0.1 h-6.0 h.

9. The method according to claim 6, wherein the solid content of the excess biochemical sludge is 1w%~10w%。

10. The method of claim 6, wherein the auxiliary is an alkaline auxiliary selected from at least one of sodium hydroxide, potassium hydroxide, sodium oxide, sodium peroxide, potassium oxide, potassium peroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate.

11. The method according to claim 6, wherein the stirring speed in the mixing reaction apparatus is 20rpm to 500rpm.

12. The method according to claim 6, wherein the flash evaporation is operated at a pressure of 0MPa to 1.0MPa and at a temperature of 100 ℃ to 200 ℃.

13. The method of claim 6, wherein the solid-liquid separation comprises cyclone separation and gravity settling in sequence.

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