CN111847824A - Three-stage type dewatering and drying system and method for sludge in domestic sewage treatment plant - Google Patents

Abstract

The invention discloses a three-stage dehydration and drying system and a three-stage dehydration and drying method for sludge in a domestic sewage treatment plant, wherein the system comprises the following components: the system comprises a short-time concentration tank, dilute sludge conveying equipment, a high-pressure belt type machine conditioning tank, a high-pressure belt type dehydrator, mud cake conveying equipment, a heat recovery type hot air drier subsystem, a heat recovery type dry sludge conveying subsystem, a dry sludge bin, a high-pressure belt type machine flocculant dosing device, a high-pressure belt type machine coagulant aid dosing device, a hot air drying condensate tank and a recycling pump. The system can continuously dehydrate and dry the residual sludge in the domestic sewage plant, and three sections are short-time concentration tank concentration, high-pressure belt type machine dehydration and hot air drying respectively to dehydrate the sludge until the water content is below 40 percent. The system occupies a small area, can be conveniently butted with a domestic sewage treatment plant, can recover heat in the drying process, and effectively reduces energy consumption and cost.

Description

Three-stage type dewatering and drying system and method for sludge in domestic sewage treatment plant

Technical Field

The invention relates to the field of deep dehydration and drying in sludge treatment, in particular to a three-stage dehydration and drying system and method for sludge in a domestic sewage treatment plant.

Background

At present, various water contents of factory sludge of a domestic sewage treatment plant coexist, and according to the requirements of pollutant discharge standard of urban sewage treatment plant GB18918-2002, sludge of the urban sewage treatment plant is dewatered, and the water content of the dewatered sludge is less than 80%; according to the requirements of the pollution control standard GB16889-2008 of the domestic garbage landfill, solid residues obtained after biological treatment such as anaerobic biogas production and the like, solid residues obtained after fecal treatment and sludge of a domestic sewage treatment plant are treated, the water content is less than 60%, and the solid residues can be subjected to landfill treatment in the domestic garbage landfill; in recent years, due to the saturation of landfill sites and the difficulty in exporting, partial areas put higher requirements on the water content of sludge of domestic sewage treatment plants, and the water content needs to be reduced to be lower in the domestic sewage treatment plants.

The existing dehydration drying measures in the domestic sewage treatment plant comprise the dehydration of a centrifuge belt machine, the moisture content of the sludge is reduced to 80%, but because the reduction is low, most projects are upgraded and modified at present, and the moisture content is continuously reduced. The water content of the sludge can be reduced to 60% by devices such as a diaphragm plate-and-frame filter press, a vertical filter press and a high-pressure belt filter press, but the water content is further reduced by the method, but the subsequent disposal end is greatly limited due to the problems that lime needs to be added, the water content is still high, the reduction is not thorough and the like. The moisture content of the sludge is reduced to 30-40% by a heat drying machine and a heat pump drying machine, so that the reduction in a domestic sewage treatment plant can be basically realized to the maximum extent, but the heat drying needs steam or diesel oil and the like as a heat source, so that the requirement on the heat source around the domestic sewage treatment plant or the requirement on the occupied land is high, the heat drying operation cost is high, and the application in the sewage treatment plant has limitation; and the simple heat pump drying process occupies small area, has high power consumption and operation cost and is uneconomical.

At present, Chinese patents CN 106746448B and CN209522749U both provide a sludge drying method by continuous deep dehydration and low-temperature heat pump, which is to reduce the moisture content of wet sludge with the moisture content of 80 percent to 60 to 70 percent through a high-pressure belt filter press, and then reduce the moisture content of the sludge to below 40 percent through a low-temperature heat pump dryer. The scheme adopts a high-pressure belt type filter press form, although the occupied area is small, the system equipment is simple, the comprehensive recovery of energy is not considered, in addition, the water content of the sludge is firstly reduced to about 80 percent by a centrifugal machine and then enters the system, the overall design of the process of a domestic sewage treatment plant is not considered, and the operation cost of the sewage plant cannot be integrally reduced.

Disclosure of Invention

Based on the problems in the prior art, the invention aims to provide a three-stage dehydration and drying system and a three-stage dehydration and drying method for sludge in a domestic sewage treatment plant, which can solve the problems that the existing sludge drying system is not easy to directly butt joint with the domestic sewage treatment plant and has no energy recovery and the like.

The purpose of the invention is realized by the following technical scheme:

the embodiment of the invention provides a three-stage type dewatering and drying system for sludge in a domestic sewage treatment plant, which comprises:

the system comprises a short-time concentration tank, dilute sludge conveying equipment, a high-pressure belt type machine conditioning tank, a high-pressure belt type dehydrator, mud cake conveying equipment, a heat recovery type hot air drier subsystem, a heat recovery type dry sludge conveying subsystem, a dry sludge bin, a high-pressure belt type machine flocculant dosing device, a high-pressure belt type machine coagulant aid dosing device, a hot air drying condensate tank and a recycling pump; wherein the content of the first and second substances,

the short-time concentration tank is provided with a water inlet pipe, and a sludge discharge port of the short-time concentration tank is sequentially connected with the high-pressure belt type machine conditioning tank, the high-pressure belt type dehydrator, the high-pressure belt type machine flocculant dosing device, the high-pressure belt type machine coagulant aid dosing device, the mud cake conveying equipment, the heat recovery type hot air drier subsystem, the heat recovery type dry sludge conveying subsystem and the dry sludge bin through the dilute sludge conveying equipment;

the high-pressure belt type machine flocculant dosing device and the high-pressure belt type machine coagulant aid dosing device are connected with the high-pressure belt type machine conditioning tank;

the front end of the hot air drying condensate tank is connected with the heat recovery type hot air drying machine subsystem, and the rear end of the hot air drying condensate tank is connected with the high-pressure belt type dehydrator through the recycling pump.

The invention relates to a three-stage dehydration and drying method for sludge in a domestic sewage treatment plant, which is characterized in that the three-stage dehydration and drying system for sludge in the domestic sewage treatment plant comprises the following steps:

concentrating residual sludge with the water content of 99.2% of that of a domestic sewage treatment plant by using a short-time concentration tank of the dehydration drying system to obtain primary concentrated sludge with the water content of 97-98%;

the primary concentrated sludge is conveyed to a high-pressure belt type dehydrator of the dehydration drying system by the dilute sludge conveying equipment, and is subjected to high-pressure dehydration under the action of a medicament input from a conditioning tank of the high-pressure belt type machine by a high-pressure belt type machine flocculant dosing device and a high-pressure belt type machine coagulant aid dosing device to obtain a concentrated mud cake with the water content of 60-70%;

the concentrated mud cake is subjected to hot air drying and hot air recycling through a mud cake conveying device and conveyed to a heat recycling type hot air drier subsystem of the dehydration drying system, so that the final concentrated mud with the water content of below 40% is obtained;

and storing the final concentrated sludge into the dry sludge bin to finish the three-stage dehydration and drying treatment of the sludge in the domestic sewage treatment plant.

According to the technical scheme provided by the invention, the three-stage type dewatering and drying system and the three-stage type dewatering and drying method for the sludge in the domestic sewage treatment plant provided by the embodiment of the invention have the beneficial effects that:

the sludge drying system capable of treating the sludge in the domestic sewage treatment plant in a short-time concentration, high-pressure belt type dehydration and hot air drying three-section manner is formed by arranging an organically-connected short-time concentration tank, a dilute sludge conveying device, a high-pressure belt type machine conditioning tank, a high-pressure belt type dehydration machine, a sludge cake conveying device, a heat recovery type hot air drying machine subsystem, a heat recovery type dry sludge conveying subsystem, a dry sludge bin, a high-pressure belt type machine flocculant dosing device, a high-pressure belt type machine coagulant aid dosing device, a hot air drying condensate tank and a recycling pump; due to the adoption of the heat recovery type hot air drier subsystem and the heat recovery type dry sludge conveying subsystem, the heat of hot air can be recovered and recycled while the sludge is dried and conveyed by the hot air. The system has strong adaptability, does not need heat source conditions which are difficult to be possessed by common domestic sewage treatment plants such as steam, fuel gas and the like compared with other heat drying forms, occupies small area, and is suitable for new construction and modification projects of most domestic sewage treatment plants.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a schematic overall view of a three-stage dewatering and drying system for sludge in a domestic sewage treatment plant according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a short-term concentration tank of a three-stage dehydration and drying process for sludge in a domestic sewage treatment plant according to an embodiment of the present invention;

FIG. 3 is a schematic view of a high-pressure belt type dehydration matching system of a three-stage dehydration and drying process for sludge in a domestic sewage treatment plant according to an embodiment of the present invention;

FIG. 4 is a hot air drying section material and hot air orientation diagram of a three-section dehydration drying process for sludge in a domestic sewage treatment plant according to an embodiment of the present invention;

FIG. 5 is a schematic view of a wet sludge cake transport apparatus provided by an embodiment of the present invention;

FIG. 6 is an overall flow chart of a three-stage dehydration and drying method for sludge in a domestic sewage treatment plant according to an embodiment of the present invention;

in the figure: 10-short time concentration tank; 101-a water inlet pipe; 102-central cylinder with reflective plate; 103-short-time concentration tank body; 104-central cartridge support; 105-sludge pipe backwash pipe; 106-sludge pipe valve, 107-concentrated sludge storage tank body; 108-concentrated sludge reservoir mixer; 109-sludge pipe branch pipe; 1010-overflow weir; c, a supernatant liquid reflux port of the short-time concentration tank; 1011-a sludge suction pipe at the bottom of the sludge pipe and 1012-a sludge discharge port; 20-high pressure belt dewaterer; a-a water outlet of the high-pressure belt type dehydrator; 30-a heat recovery type hot air dryer subsystem; 301-a housing; 302-a belt conveyor; 303-feed inlet and crushing device; 304-a guiding fan; 305-dry mud discharge port; 306-a condensate drain; 307-dry hot air duct; 308-a wet and warm air duct; 309-wet and warm air duct dust removing device; 3010-ion deodorizing device for wet and warm air duct; 3011-a heat recovery device; 3012-refrigerant evaporator; 3013-refrigerant condenser; 3014-a compressor; 3015-refrigerant water condenser; 3016-a cooling tower; 3017-refrigerant expansion valve; 3018-wet cooling air duct; 3019-dry cold air duct; 3020-moisture removing blower; 40-dry sludge bin; 50-dilute sludge conveying equipment; 60-high pressure belt machine conditioning tank; 70-high pressure belt machine flocculant dosing device; 80-high pressure belt type mechanical coagulant aid dosing device; 90-mud cake conveying equipment; 901-drive and coupling means; 902-a feed inlet; 903-discharge hole; 904-helical blades; 905-inlet of recovered hot air; 906-a recycled hot air outlet; 907-a machine shell; 100-a heat recovery type dry sludge conveying subsystem; 1001-dry mud shaftless screw conveyor; 1002-lifting a scraper conveyor; 1003-dry sludge discharging hot air recycling pipeline; 1004-dry sludge discharging hot air recovery pipeline dust removing device; 1005-dry mud discharging hot air recycling micro negative pressure fan; 110-hot air drying condensate water tank; b, a water outlet of the hot air drying condensate tank; 120-recycling pump.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the specific contents of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention. Details which are not described in detail in the embodiments of the invention belong to the prior art which is known to the person skilled in the art.

As shown in fig. 1, an embodiment of the present invention provides a three-stage dewatering and drying system for sludge in a domestic sewage treatment plant, including:

the system comprises a short-time concentration tank 10, dilute sludge conveying equipment 50, a high-pressure belt type machine conditioning tank 60, a high-pressure belt type dehydrator 20, mud cake conveying equipment 90, a heat recovery type hot air drier subsystem 30, a heat recovery type dry sludge conveying subsystem 100, a dry sludge bin 40, a high-pressure belt type machine flocculant dosing device 70, a high-pressure belt type machine coagulant aid dosing device 80, a hot air drying condensate water tank 110 and a recycling pump 120; wherein the content of the first and second substances,

the short-time concentration tank 10 is provided with a water inlet pipe, and a sludge discharge port of the short-time concentration tank 10 is sequentially connected with the high-pressure belt type machine conditioning tank 60, the high-pressure belt type dewatering machine 20, the high-pressure belt type machine flocculant dosing device 70, the high-pressure belt type machine coagulant aid dosing device 80, the mud cake conveying equipment 90, the heat recovery type hot air drying machine subsystem 30, the heat recovery type dry sludge conveying subsystem 100 and the dry sludge bin 40 through the dilute sludge conveying equipment 50;

the high-pressure belt machine flocculating agent dosing device 70 and the high-pressure belt machine coagulant aid dosing device are connected with the high-pressure belt machine conditioning tank;

the front end of the hot air drying condensate water tank 110 is connected with the heat recovery type hot air drying machine subsystem 30, and the rear end of the hot air drying condensate water tank 110 is connected with the high-pressure belt type dehydrator 20 through the recycling pump 120.

As shown in fig. 2, in the above system, the short-time concentration tank 10 includes:

the system comprises a concentration tank body 103, a sludge storage tank body 107, a central cylinder with a reflecting plate 102, a central cylinder support frame 104, a water inlet pipe 101, a sludge pipe branch pipe 109, a bottom sludge suction pipe 1011, a sludge pipe valve 106, a storage tank stirrer 108 and a sludge discharge port 1012; wherein the content of the first and second substances,

the concentration tank body 103 and the sludge storage tank body 107 are arranged in parallel;

the central cylinder with reflecting plate 102 is arranged in the concentration tank body 103 through the central cylinder supporting frame 104, and a water inlet is arranged at the bottom of the central cylinder with reflecting plate 102;

the water inlet pipe 101 is connected with the upper part of the central cylinder with the reflecting plate 102;

the sludge pipe branch pipe 109 is arranged at the upper part in the concentration tank body 103, and the outlet of the sludge pipe branch pipe 109 is arranged in the sludge storage tank body 107;

the bottom sludge suction pipe 1011 is arranged in the concentration tank body 103, the inlet of the bottom sludge suction pipe 1011 is positioned at the bottom of the concentration tank body 103, and the outlet of the bottom sludge suction pipe 1011 is connected with the inlet of the sludge pipe branch pipe 109;

the sludge pipe valve 106 is arranged on the outlet of the sludge pipe branch pipe 109;

the reservoir mixer 108 is arranged in the sludge reservoir body 107, and the bottom of the sludge reservoir body 107 is provided with the sludge discharge port.

Preferably, in the short-time concentration tank 10, two concentration tank bodies 103 are arranged in parallel on two sides of the sludge storage tank body 107, and the arrangement modes of the central cylinder belt reflecting plate 102, the central cylinder supporting frame 104, the water inlet pipe 101, the sludge pipe branch pipe 109 and the bottom sludge suction pipe 1011 in the two short-time concentration tanks 10 and the connection mode with the sludge storage tank body 107 are the same. The arrangement of two concentration tank bodies 103 can improve the treatment capacity of short-time concentration.

Referring to fig. 2, the short-time concentration tank 10 further includes: a sludge pipe backwash pipe 105 and an overflow weir 1010;

wherein the sludge pipe backwash pipe 105 is arranged in the concentration tank body 103, the bottom outlet of the sludge pipe backwash pipe 105 is connected with the inlet of the sludge pipe branch pipe 109, and the inlet of the sludge pipe backwash pipe 105 is positioned outside the concentration tank body 103;

the overflow weir 1010 is arranged around the upper part of the inner wall of the concentration tank body 103. The upper clear liquid return opening is arranged on the overflow weir 1010, the upper clear liquid return opening can be connected with a primary sedimentation tank of a domestic sewage treatment plant, and by arranging the overflow weir, the upper clear liquid flows back to the primary sedimentation tank of the domestic sewage treatment plant after passing through the overflow weir, so that the carbon source in the returned clear liquid can be utilized.

The concentration tank body 103 and the sludge storage tank body 107 both adopt a similar vertical flow sedimentation tank structure. This short-time concentration tank through with class vertical flow sedimentation tank structure, replaces traditional mud reservoir, realizes the concentration of domestic sewage excess sludge, and this short-time concentration tank's design dwell time is 2 ~ 4 hours, and the design dwell time of concentrated mud reservoir is 0.5 ~ 1 hour.

The thin sludge conveying equipment in the system adopts a positive displacement pump such as a screw pump.

Referring to fig. 3, the bottom of the high-pressure belt dehydrator 20 in the above system is provided with a water discharge port.

As shown in fig. 4, the heat recovery type hot air dryer subsystem 30 of the above system includes:

a machine shell 301, a belt conveyor 302, a feeding hole, a crushing device 303, a dry sludge discharging hole 305, a diversion fan 304, a condensed water drain pipe 306 and hot air supply recovery equipment; wherein the content of the first and second substances,

the belt conveyor 302 is arranged in the machine shell 301, the top of the front end of the machine shell 301 is provided with the feed inlet, and the feed inlet is positioned above the front end of the belt conveyor 302;

the crushing device 303 is arranged in the feeding hole;

the dry sludge discharge port 305 is arranged at the bottom of the rear end of the machine shell 301, and the dry sludge discharge port 305 is positioned below the rear end of the belt conveyor 302;

the bottom in the shell 301 is provided with the guide fan 304;

the bottom of the casing 301 is provided with the condensed water drain pipe 306, and the condensed water drain pipe 306 is connected with the front end of the hot air drying condensed water tank 110;

the hot air supply and recovery device is respectively provided with a dry hot air duct 307 and a wet warm air duct 308, the dry hot air duct 307 is communicated with the inside of the machine shell 301 from the bottom of the machine shell 301, and the wet warm air duct 308 is communicated with the inside of the machine shell 301 from the top of the machine shell 301.

The drying temperature of the heat recovery type hot air dryer subsystem is 65-75 ℃.

Referring to fig. 4, the hot wind supply and recovery apparatus includes:

a heat recovery device 3011, a moisture exhaust fan 3020, a wet cold air duct 3018, a refrigerant evaporator 3012, a dry cold air duct 3019, the wet warm air duct 308, a wet warm air duct dust removal device 309, a wet warm air duct ion deodorization device 3010, the dry hot air duct 307, a refrigerant condenser 3013, a compressor 3014, a cooling tower 3016, a refrigerant water condenser 3015, and a refrigerant expansion valve 3017; wherein the content of the first and second substances,

the heat recovery device 3011 is respectively provided with a recovery port, a hot air outlet, a moisture exhaust port and a return air port, and the circulating air outlet is connected with the return air port through the moisture exhaust fan 3020, the wet cold air duct 3018, the refrigerant evaporator 3012 and the dry cold air duct 3019 which are sequentially connected; by adopting the structure, condensed water generated when water in the wet and cold air duct passes through the refrigerant evaporator can be collected by the hot air drying condensed water tank, and then can be pumped to the high-pressure belt type dehydrator and the high-pressure belt type machine flocculant dosing device through the recycling pump, and is used for cleaning filter cloth of the high-pressure belt type dehydrator and preparing a medicament for the high-pressure belt type machine flocculant dosing device; preferably, the hot air drying condensate water tank is provided with a water outlet in a collecting way;

the wet and warm air duct 308 is connected with a recovery port of the heat recovery device 3011 through the wet and warm air duct dust collector device 309 and the wet and warm air duct ion deodorization device 3010 in sequence; the internal deodorization of the hot air drying subsystem can be realized;

a hot air outlet of the heat recovery device 3011 is connected to the dry hot air duct 307 through the refrigerant condenser 3013;

an outlet of the compressor 3014 is sequentially connected to the refrigerant water condenser 3015, the refrigerant condenser 3013, the refrigerant expansion valve 3017 and the refrigerant evaporator 3012 through a pipeline and then connected to an inlet of the compressor 3014;

the cooling tower 3016 is connected to the coolant condenser 3015.

As shown in fig. 5, in the above system, the mud cake conveying device 90 includes:

a shell 907, a feeding port 902, a discharging port 903, a recycled hot air outlet 906, a recycled hot air inlet 905, a spiral blade 904 and a driving device 901; wherein the content of the first and second substances,

the top of the front end of the outer shell 907 is provided with the feed inlet 902, and the bottom of the rear end of the outer shell 907 is provided with the discharge outlet 903;

the front end and the rear end of the top of the shell 907 are respectively provided with a recycled hot air outlet 906 and a recycled hot air inlet 905;

the spiral blade 904 is arranged in the shell 907, the driving device 901 is arranged outside the rear end of the shell 907, and the driving device 901 is connected with the spiral blade 904 and can drive the spiral blade 904 to rotate in the shell 907 to convey mud cakes.

The mud cake conveying equipment is a shaftless screw conveyor, and the material of the screw blade is SUS304 or more. The mud cake conveying equipment can recycle heat brought by mud discharged from the hot air drier system by arranging the recycling hot air inlet and the recycling hot air outlet.

Referring to fig. 4, in the above system, the heat recovery type dry sludge conveying subsystem 100 includes: a dry mud shaftless screw conveyor 1001, a lifting scraper conveyor 1002, a dry mud discharging hot air recovery pipeline 1003, a dry mud discharging hot air recovery pipeline dust removal device 1004 and a dry mud discharging hot air recovery micro negative pressure fan 1005; wherein the content of the first and second substances,

the discharge port of the dry sludge shaftless screw conveyor 1001 is connected with the lifting scraper conveyor 1002, and the discharge port of the lifting scraper conveyor 1002 is connected with the dry sludge bin 40;

the dry sludge discharging hot air recovery pipeline 1003 is respectively connected with an air suction opening on a shell of the dry sludge shaftless screw conveyor 1001 and an air suction opening on a shell of the lifting scraper conveyor 1002, a dry sludge discharging hot air recovery pipeline dust removal device 1004 and a dry sludge discharging hot air recovery micro negative pressure fan 1005 are sequentially arranged on the dry sludge discharging hot air recovery pipeline 1003, and the outlet end of the dry sludge discharging hot air recovery pipeline 1003 is connected with the mud cake conveying equipment 90.

The heat recovery type dry sludge conveying subsystem with the structure can recover the heat of the dry sludge in the dry sludge shaftless screw conveyor and the lifting scraper conveyor. The method specifically comprises the following steps: at first, the dry sludge shaftless screw conveyor and the lifting scraper conveyor are internally heated to remove dust carried by dry sludge through a dry sludge discharging hot air recovery pipeline dust removal device, and then the hot air is supplied to a sludge cake conveying device through a dry sludge discharging hot air recovery micro negative pressure fan and a dry sludge discharging hot air recovery pipeline to preheat the discharged sludge of the high-pressure belt type dehydrator, so that the heat loss is reduced. The shaftless screw conveyor and the lifting scraper conveyor are both provided with air suction openings which respectively conduct heat carried by dry sludge materials to the outside.

Preferably, the shaftless screw conveyor blade of the heat recovery type dry sludge conveying subsystem is made of stainless steel SUS304 or more, and is coated with a wear-resistant carbide coating, so that the wear resistance can be improved, and the service life can be prolonged.

As shown in fig. 6, an embodiment of the present invention further provides a three-stage dehydration drying method for sludge in a domestic sewage treatment plant, which employs the three-stage dehydration drying system for sludge in a domestic sewage treatment plant of the claims, and includes the following steps:

concentrating residual sludge with the water content of 99.2% of a domestic sewage treatment plant by using a short-time concentration tank 10 of the dehydration drying system to obtain primary concentrated sludge with the water content of 97-98%;

the primary concentrated sludge is conveyed to a high-pressure belt type dehydrator 20 of the dehydration drying system through the dilute sludge conveying equipment 50, and is subjected to high-pressure dehydration under the action of a medicament input from the high-pressure belt type machine conditioning tank 60 through a high-pressure belt type machine flocculant dosing device 70 and a high-pressure belt type machine coagulant aid dosing device 80 to obtain a concentrated mud cake with the water content of 60-70%;

the concentrated mud cake is subjected to hot air drying and hot air recycling through a mud cake conveying device 90 and a heat recycling type hot air drier subsystem 30 of the dehydration drying system to obtain final concentrated mud with the water content of below 40%;

and storing the final concentrated sludge into the dry sludge bin 40, thus finishing the three-stage dehydration and drying treatment of the sludge in the domestic sewage treatment plant.

In the method, the retention time of the short-time concentration tank 10 is 2-4 hours;

the pressure of the high-pressure belt type dehydrator 10 is 0.3Mpa to 0.6 Mpa; the water content of the inlet sludge of the high-pressure belt type dehydrator is required to be 97-98%, and the water content of the outlet sludge is 60-70%;

the dosing amount of the high-pressure belt machine flocculant dosing device 70 is 0.2-0.4% of the dry solid amount of the sludge, and the flocculant added by the high-pressure belt machine flocculant dosing device 70 adopts anionic polyacrylamide;

the dosing amount of the high-pressure belt type mechanical coagulant aid dosing device 80 is 8% -20% of the dry solid amount of the sludge, and the coagulant aid added by the high-pressure belt type mechanical coagulant aid dosing device 80 adopts ferric trichloride solution with the mass concentration of 38%.

The invention relates to a three-stage dehydration and drying system and a three-stage dehydration and drying method for sludge in a domestic sewage treatment plant, which are characterized in that the three-stage dehydration and drying system and the method begin from the collection and concentration of residual sludge in the domestic sewage treatment plant to the filter pressing and dehydration of a high-pressure belt type dehydrator and then to the drying of hot air, so that the three-stage gradual dehydration and drying process is realized, the combined advantages of short-time concentration tank concentration, the high-pressure belt type dehydrator and the hot air dryer are fully utilized in the treatment process, the integral operation cost of the sludge in the domestic sewage treatment plant is fully reduced, the heat of the hot air drying is fully utilized, and the. Has the characteristics of small occupied area, low requirement on energy conditions, strong adaptability, full recovery of materials and energy and cost reduction.

The three-stage type dewatering and drying system and the three-stage type dewatering and drying method for the sludge in the domestic sewage treatment plant have the advantages that:

(1) the method has clear treatment flow, realizes the gradual reduction of the water content by three sections of concentration, belt filter pressing and hot air drying from the residual sludge of the domestic sewage treatment plant, has simple system configuration, saves equipment facilities such as a sludge storage tank, a centrifugal dehydrator and the like of the domestic sewage treatment plant, and ensures that the design of the domestic sewage treatment plant is more systematic under the drying condition;

(2) the system and the method greatly reduce the overall operation cost;

(21) the short-time concentration tank is adopted in the concentration section, the failure rate and the energy consumption are low, the sludge concentration is realized, and simultaneously, the supernatant liquid of the short-time fermentation is returned to the primary sedimentation tank, so that a small amount of carbon source is provided for a domestic sewage biochemical system, and the running cost of a domestic sewage treatment plant is systematically saved;

(22) the high-pressure belt type filter pressing section does not add high-solid-content increment agents such as lime and the like, reduces the water content of the sludge through mechanical filter pressing, reduces the model selection of subsequent hot air drying equipment, and reduces the operation cost;

(23) the hot air drying section condenses moisture in the sludge through a heat pump unit, the water quality is high, and the condensed water is used as cleaning water and soaking water of the high-pressure belt type filter pressing section, so that the using amount of tap water is reduced. The energy loss of the heat pump unit is reduced and the operation cost is reduced by recycling the sludge heat in the dry sludge conveying equipment;

(3) compared with other heat drying forms, the invention has strong adaptability, does not need heat source conditions which are difficult to be possessed by common domestic sewage treatment plants such as steam, fuel gas and the like, occupies small area, and is suitable for new construction and modification projects of most domestic sewage treatment plants;

(4) the invention is relatively friendly to the environment, and when the heat of the dry sludge is recovered, the ion deodorization facility is additionally arranged in the air duct of the heat removal pump to deodorize the circulating air in the system, and the operation environment of the hot air drying is greatly improved by matching with the workshop space deodorization;

(5) the sludge reduction amount of the invention is higher, the sludge water content is reduced to below 40% from 99.2%, the reduction amount reaches more than 99%, and if the reduction amount is converted by 80% of water content, the reduction amount is 70-80%.

(6) The system and the method expand the tail end disposal way after the sludge is dehydrated and dried.

The embodiments of the present invention are described in further detail below.

As shown in fig. 1, the present embodiment provides a three-stage dewatering and drying system for sludge in a domestic sewage treatment plant, including: the system comprises a short-time concentration tank, a high-pressure belt type dehydrator, a heat recovery type hot air drier subsystem, a dry sludge bin, dilute sludge conveying equipment, a high-pressure belt type machine conditioning tank, a high-pressure belt type machine flocculant dosing device, a high-pressure belt type machine coagulant aid dosing device, mud cake conveying equipment, a heat recovery type dry sludge conveying subsystem, a hot air drying condensate tank and a recycling pump; the short-time concentration tank, the dilute sludge conveying equipment, the high-pressure belt type machine conditioning tank, the high-pressure belt type dehydrator, the mud cake conveying equipment, the heat recovery type hot air drier subsystem, the heat recovery type dry sludge conveying subsystem and the dry sludge bin are sequentially connected; the high-pressure belt type machine flocculant dosing device and the high-pressure belt type machine coagulant aid dosing device are connected with the high-pressure belt type machine conditioning tank; the upper stream of the hot air drying condensate water tank is connected with a condensate water drain pipe in the heat recovery type hot air drying machine subsystem, and the lower stream of the hot air drying condensate water tank is connected with the high-pressure belt type dehydrator through a recycling pump.

Referring to fig. 1 and fig. 6, the method for sludge drying by the sludge dewatering and drying system is divided into three sections: the method comprises the steps of firstly concentrating residual sludge with the water content of 99.2% in a domestic sewage treatment plant through a short-time concentration tank to reduce the water content to 97% -98%, then further reducing the water content to 60% -70% through a high-pressure belt type dehydrator, and finally further reducing the water content to below 40% through a hot air drier system.

As shown in fig. 2, the short-time concentration tank includes: the system comprises a water inlet pipe, a central cylinder with a reflecting plate, a short-time concentration tank body, a central cylinder support frame, a sludge pipe backwashing pipe, a sludge pipe valve, a concentrated sludge storage tank body, a concentrated sludge storage tank stirrer, a sludge pipe branch pipe, an overflow weir, a sludge suction pipe at the bottom of a sludge pipe and a sludge discharge port;

as shown in fig. 2, the short-time concentration tank replaces the traditional sludge storage tank with a similar vertical flow sedimentation tank structure to realize the concentration of the domestic sewage excess sludge, the designed retention time is 2-4 hours, and the designed retention time of the concentrated sludge storage tank is 0.5-1 hour; the short-time concentration tank concentrates the water content of the sludge from 99.2% to 97% -98%; the short-time concentration tank returns supernatant to a primary sedimentation tank of a domestic sewage treatment plant after passing through an overflow weir, and a carbon source in the returned supernatant is utilized; in the short-time concentration tank, a sludge discharge port is connected with thin sludge conveying equipment, and the thin sludge conveying equipment adopts a positive displacement pump such as a screw pump;

as shown in fig. 3, the high-pressure belt type dewatering machine is provided with a high-pressure belt type machine conditioning tank, a high-pressure belt type machine flocculant dosing device and a high-pressure belt type machine coagulant aid dosing device in a matching way;

as shown in FIG. 3, the water content of the fed mud of the high-pressure belt type dehydrator is required to be 97-98%, the water content of the discharged mud is 60-70%, and the pressure grade is about 0.3-0.6 MPa;

as shown in fig. 3, the dosage of the high-pressure belt machine flocculant adding device is 0.2-0.4% of the dry solid content of the sludge; the dosage of the high-pressure belt type mechanical coagulant aid dosing device is 8-20% of the dry solid content of the sludge; the flocculant adopts anionic PAM, and the coagulant aid adopts 38% ferric trichloride solution;

as shown in fig. 4, the hot air dryer system includes: the device comprises a machine shell, a belt conveyor, a feed inlet, a crushing device, a flow guide fan, a dry mud discharge port, a condensate water drain pipe, a dry hot air duct, a wet warm air duct dust removal device, a wet warm air duct ion deodorization device, a heat recovery device, a refrigerant evaporator, a refrigerant condenser, a compressor, a refrigerant water condenser, a cooling tower, a refrigerant expansion valve, a wet cold air duct, a dry cold air duct and a moisture exhaust fan;

as shown in fig. 4, in the heat recovery type hot-air drier subsystem, after passing through the wet-warm air duct dust collector, wet-warm air duct ion deodorization device is disposed to realize the interior deodorization of the hot-air drier system;

as shown in fig. 4, in the hot air dryer system, condensed water generated when moisture in a wet and cold air duct passes through a refrigerant evaporator is collected by a hot air drying condensed water tank, is pumped to a high-pressure belt type dehydrator and a high-pressure belt type machine flocculant dosing device through a recycling pump, and is used for cleaning filter cloth of the high-pressure belt type dehydrator and dosing agent configuration of the high-pressure belt type machine flocculant dosing device; the drying temperature of the hot air dryer is 65-75 ℃.

As shown in fig. 4, the heat recovery type dry sludge conveying subsystem comprises a dry sludge shaftless screw conveyor, a lifting scraper conveyor, a dry sludge discharging hot air recovery pipeline dust removal device and a dry sludge discharging hot air recovery micro negative pressure fan.

As shown in fig. 4, the heat recovery type dry sludge conveying subsystem adopts a dry sludge shaftless screw conveyor and a lifting scraper conveyor to realize conveying and lifting of dry sludge.

As shown in fig. 4, in the heat recovery type dry sludge conveying subsystem, the heat of the dry sludge in the dry sludge shaftless screw conveyor and the lifting scraper conveyor is recovered. The method comprises the following steps: at first, the dry sludge shaftless screw conveyor and the lifting scraper conveyor are internally heated to remove dust carried by dry sludge through a dry sludge discharging hot air recovery pipeline dust removal device, and then the hot air is supplied to a sludge cake conveying device through a dry sludge discharging hot air recovery micro negative pressure fan and a dry sludge discharging hot air recovery pipeline to preheat the discharged sludge of the high-pressure belt type dehydrator, so that the heat loss is reduced.

As shown in fig. 4, in the heat recovery type dry sludge conveying subsystem, the shaftless screw conveyor and the lifting scraper conveyor are both provided with air suction ports for guiding heat carried by dry sludge materials.

As shown in fig. 4, in the heat recovery type dry sludge conveying subsystem, the shaftless screw conveyor blade is made of stainless steel SUS304 or above and is coated with an abrasion-resistant carbide coating.

As shown in fig. 5, the mud cake conveying equipment comprises a driving and connecting shaft device, a feeding hole, a discharging hole, a spiral blade, a recycling hot air inlet, a recycling hot air outlet and a casing.

As shown in figure 5, the mud cake conveying equipment adopts a shaftless screw conveyor, and the material of the screw blade is SUS304 or above.

As shown in fig. 5, the mud cake conveying equipment is provided with a recycling hot air inlet and a recycling hot air outlet, and the heat brought by the mud discharged from the hot air drier system is recycled.

Examples

Referring to fig. 6, the embodiment of the present invention is a method for performing three-stage dehydration and drying on sludge by using the three-stage dehydration and drying system for sludge in a domestic sewage treatment plant, including:

1) in a certain domestic sewage treatment plant, excess sludge with the water content of 99.2% is pumped into a short-time concentration tank, sludge is fed from a central cylinder of the short-time concentration tank, the excess sludge is downwards guided by a reflecting plate on the central cylinder along the central cylinder, the sludge is deposited on the bottom and the side wall of the short-time concentration tank under the action of gravity, the concentrated sludge at the bottom of the tank is pressed and conveyed into a concentrated sludge storage tank body through a sludge suction pipe at the bottom of a sludge pipe, a sludge pipe branch pipe and a sludge pipe valve under the action of liquid level difference, a concentrated sludge storage tank stirring machine is arranged in the tank body, and the stirring speed of the stirring machine is adjustable within 30-80 r/. The designed retention time of the short-time concentration tank body is 3 hours, the designed retention time of the concentrated sludge storage tank body is 0.5 hour, after the short-time concentration tank body passes through, the water content of the residual sludge is reduced to 97 percent, and the concentrated supernatant flows back to a primary sedimentation tank of a domestic sewage treatment plant;

2) pumping the concentrated sludge to a high-pressure belt type machine conditioning tank through a sludge discharge port and a dilute sludge conveying device, wherein dilute sludge conveying equipment selects a positive displacement pump such as a screw pump, an anion PAM solution is added into the conditioning tank, the adding amount of the anion PAM solution is 0.3 percent of sludge TS (total sulfur) converted into dry powder, a 38 percent concentration ferric trichloride solution is added into the conditioning tank, the adding amount of the 38 percent concentration ferric trichloride solution is 15 percent of TS, and the dilute sludge, the PAM and a ferric trichloride agent are uniformly mixed in the conditioning tank and then fed into a high-pressure belt type dewatering machine;

3) dewatering sludge through the pressure filtration effect of a multi-stage dewatering roller of a high-pressure belt type dewaterer to reduce the water content of the sludge to 70%, wherein the pressure roller of the high-pressure belt type dewaterer is preferably 0.3-0.5 Mpa, the waste water after pressure filtration is discharged outside, a wet mud cake after pressure filtration is fed into a heat recovery type hot air drier subsystem through mud cake conveying equipment, the mud cake conveying equipment adopts a shaftless screw conveyer with a hot air inlet and a hot air outlet, the wet mud cake can exchange heat with recycled hot air in the mud cake conveying equipment to improve the temperature of the sludge entering the heat recovery type hot air drier subsystem and evaporate part of water, the mud cake conveying equipment adopts a shaftless screw conveyer, and the material of a screw blade is selected from SUS304 and above materials;

4) the sludge enters a heat recovery type hot air dryer subsystem after being subjected to preliminary heating evaporation through a mud cake conveying device, granulation is carried out in the hot air dryer through a feed inlet and a crushing device, the granulation particle size DxL is phi 10mm multiplied by 15mm, the sludge is turned back and conveyed on the conveying surface of a three-layer belt conveyor after granulation, the conveying surface of the belt conveyor is made of a Teflon anti-corrosion material, and the retention time of the sludge on the belt conveyor is about 1 hour. The air temperature in a dry hot air duct and a wet hot air duct of the heat recovery type hot air drier subsystem is 70 ℃, the air temperature in the wet hot air duct is 55 ℃, and the refrigerant is R134 a;

the dry hot air in the dry hot air duct blows the dry hot air to the sludge conveying surface of the belt conveyor through the diversion fan, water in the sludge is evaporated, wet and warm air carrying the water in the sludge is mixed with wet and warm air carrying the water by the mud cake conveying equipment, the wet and warm air duct dust removing device is used for filtering dust in the wet and warm air, odor is reduced through the wet and warm air duct ion deodorization device, and then the odor sequentially passes through the heat recovery device, the dehumidifying fan, the refrigerant evaporator, the heat recovery device and the refrigerant condenser. Warm and humid air is subjected to heat exchange with dry and cold air in the heat recovery device, so that the warm and humid air energy is reduced, and the heat of the dry and cold air is improved; carrying out flow guide through a moisture removal fan; moisture in the wet warm air is condensed by evaporating and absorbing heat of a refrigerant in a refrigerant evaporator to form dry cold air; draining water to a hot air drying condensate water tank through a condensate water drainage pipe; the heat is released through the condensation of the refrigerant in the refrigerant condenser, dry cold air is heated to form dry hot air, and the dry hot air is blown back to the sludge conveying surface of the belt conveyor under the action of a diversion fan to form hot air dehydration circulation;

refrigerant R134a is subjected to isentropic compression in the compressor, and the refrigerant is in a low-temperature low-pressure gaseous state to a high-pressure high-temperature superheated gaseous state; cooling the high-pressure high-temperature superheated gaseous refrigerant by a refrigerant water condenser and a cooling tower to remove redundant heat, and then feeding the refrigerant water condenser; condensing and releasing heat in a condenser, wherein the refrigerant is in a high-pressure high-temperature superheated gaseous state to a high-pressure medium-temperature liquid state; the liquid refrigerant of high pressure and medium temperature completes the isenthalpic throttling process through an expansion valve, and the refrigerant is in a low-pressure low-temperature gas-liquid mixed state from the high-pressure medium temperature liquid state; the low-pressure low-temperature gas-liquid mixed refrigerant finally evaporates and absorbs heat in the refrigerant evaporator to finish the isobaric evaporation and heat absorption process, and the refrigerant is in a low-temperature low-pressure gas state from a low-pressure low-temperature gas-liquid mixed state and then enters the compressor to form refrigerant circulation;

in the circulation, the heat absorption and the heat release of the driving refrigerant are obtained through the power consumption of the compressor, so that the circulation heat absorption and the heat release of hot air in the hot air drier are realized, and the drying dehydration is finally realized;

5) the water content of the sludge is reduced to below 40% after being dried by the heat recovery type hot air dryer subsystem, the dried sludge is in a granular state, and the dry sludge is fed into a dry sludge bin by the heat recovery type dry sludge conveying subsystem. The horizontal conveying in the heat recovery type dry sludge conveying subsystem adopts a dry sludge shaftless screw conveyor with an air suction opening, blades of the shaftless screw conveyor adopt stainless steel SUS304 and above materials, and a wear-resistant carbide coating is coated outside. The inclined conveying adopts a lifting scraper conveyor with an air suction opening, the dry sludge in the dry sludge shaftless screw conveyor and the lifting scraper conveyor still has the temperature of about 50 ℃, the heat is recovered by arranging a hot air recovery micro negative pressure fan, the dust in the dry sludge is removed by a hot air recovery pipeline dust removal device, the air is supplied into mud cake conveying equipment, the heat recovery is enhanced, and the operation cost is reduced;

6) condensed water of the heat recovery type hot air drier subsystem is collected in a hot air drying condensed water tank and is recycled to the high-pressure belt type dehydrator through the recycling pump to wash cloth and dispense medicines, and therefore the consumption of cleaning water is reduced.

The above is an embodiment of the invention, and it can be known from the description of the embodiment that the three-stage dehydration and drying process for sludge in a domestic sewage treatment plant provided by the invention has the advantages of energy saving, environmental protection, low cost and the like, and the sludge reduction is gradually realized by adopting the sludge three-stage process. After the treatment by the process, the tail end treatment way of the sludge is effectively expanded: can be used as auxiliary fuel for thermal power plants, household garbage incineration plants and the like, can be used as building material processing raw materials for cement kilns and the like, and can be used as landfill covering soil and the like.

The process fully combines the advantages of short-time concentration, high-pressure belt press filtration and hot air drying, is feasible, economical, efficient and strong in adaptability, can be widely applied to newly-built and sludge upgrading projects of domestic sewage treatment plants, and provides a feasible process reference for drying in the domestic sewage treatment plants.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (10)

1. The utility model provides a mud syllogic dehydration mummification system in domestic sewage treatment plant which characterized in that includes:

the system comprises a short-time concentration tank (10), dilute sludge conveying equipment (50), a high-pressure belt type machine conditioning tank (60), a high-pressure belt type dewatering machine (20), mud cake conveying equipment (90), a heat recovery type hot air drying machine subsystem (30), a heat recovery type dry sludge conveying subsystem (100), a dry sludge bin (40), a high-pressure belt type machine flocculant dosing device (70), a high-pressure belt type machine coagulant aid dosing device (80), a hot air drying condensation water tank (110) and a recycling pump (120); wherein the content of the first and second substances,

the short-time concentration tank (10) is provided with a water inlet pipe, and a sludge discharge port of the short-time concentration tank (10) is sequentially connected with the high-pressure belt type machine conditioning tank (60), the high-pressure belt type dewatering machine (20), the high-pressure belt type machine flocculant dosing device (70), the high-pressure belt type machine coagulant aid dosing device (80), the mud cake conveying equipment (90), the heat recovery type hot air drying machine subsystem (30), the heat recovery type dry sludge conveying subsystem (100) and the dry sludge bin (40) through the thin sludge conveying equipment (50);

the high-pressure belt machine flocculating agent dosing device (70) is connected with the high-pressure belt machine coagulant aid dosing device and the high-pressure belt machine conditioning tank;

the front end of hot-air drying condensate water tank (110) with heat recovery type hot-air drying machine subsystem (30) links to each other, and the rear end of this hot-air drying condensate water tank (110) passes through retrieval and utilization pump (120) with high-pressure belt dewaterer (20) link to each other.

2. The three-stage dewatering and drying system for sludge in a domestic sewage treatment plant according to claim 1, wherein the short-time thickening tank (10) comprises:

the device comprises a concentration tank body (103), a sludge storage tank body (107), a central cylinder with a reflecting plate (102), a central cylinder support frame (104), the water inlet pipe (101), a sludge pipe branch pipe (109), a bottom sludge suction pipe (1011), a sludge pipe valve (106), a storage tank stirrer (108) and the sludge discharge port (1012); wherein the content of the first and second substances,

the concentration tank body (103) and the sludge storage tank body (107) are arranged in parallel;

the central cylinder with the reflecting plate (102) is arranged in the concentration tank body (103) through the central cylinder supporting frame (104), and a water inlet is formed in the bottom of the central cylinder with the reflecting plate (102);

the water inlet pipe (101) is connected with the upper part of the central cylindrical reflecting plate (102);

the sludge pipe branch pipe (109) is arranged at the upper part in the concentration tank body (103), and the outlet of the sludge pipe branch pipe (109) is arranged in the sludge storage tank body (107);

the bottom sludge suction pipe (1011) is arranged in the concentration tank body (103), the inlet of the bottom sludge suction pipe (1011) is positioned at the bottom of the concentration tank body (103), and the outlet of the bottom sludge suction pipe (1011) is connected with the inlet of the sludge pipe branch pipe (109);

the sludge pipe valve (106) is arranged on the outlet of the sludge pipe branch pipe (109);

the storage pool stirrer (108) is arranged in the sludge storage pool body (107), and the bottom of the sludge storage pool body (107) is provided with the sludge discharge port.

3. The three-stage dewatering and drying system for sludge in a domestic sewage treatment plant according to claim 2, wherein the short-time concentration tank (10) further comprises:

a sludge pipe backwash pipe (105) and an overflow weir (1010); wherein the content of the first and second substances,

the sludge pipe backwashing pipe (105) is arranged in the concentration tank body (103), the bottom outlet of the sludge pipe backwashing pipe (105) is connected with the inlet of the sludge pipe branch pipe (109), and the inlet of the sludge pipe backwashing pipe (105) is positioned outside the concentration tank body (103);

the overflow weir (1010) is arranged on the upper part of the inner wall of the concentration tank body (103) in a surrounding way.

4. The three-stage dewatering and drying system for sludge in a domestic sewage treatment plant according to claim 2 or 3, wherein the concentration tank body (103) and the sludge storage tank body (107) both adopt a similar vertical flow sedimentation tank structure.

5. The system for three-stage dewatering and drying of sludge in a domestic sewage treatment plant according to any one of claims 1 to 3, wherein the hot air dryer subsystem (30) comprises:

the device comprises a machine shell (301), a belt conveyor (302), a feeding hole, a crushing device (303), a dry sludge discharging hole (305), a guide fan (304), a condensed water discharging pipe (306) and hot air supply recovery equipment; wherein the content of the first and second substances,

the belt conveyor (302) is arranged in the machine shell (301), the top of the front end of the machine shell (301) is provided with the feed inlet, and the feed inlet is positioned above the front end of the belt conveyor (302);

the crushing device (303) is arranged in the feeding hole;

the dry sludge discharge port (305) is arranged at the bottom of the rear end of the machine shell (301), and the dry sludge discharge port (305) is positioned below the rear end of the belt conveyor (302);

the bottom in the shell (301) is provided with the flow guide fan (304);

the bottom of the casing (301) is provided with the condensed water drain pipe (306), and the condensed water drain pipe (306) is connected with the front end of the hot air drying condensed water tank (110);

the hot air supply and recovery equipment is respectively provided with a dry hot air duct (307) and a wet warm air duct (308), the dry hot air duct (307) is communicated with the interior of the machine shell (301) from the bottom of the machine shell (301), and the wet warm air duct (308) is communicated with the interior of the machine shell (301) from the top of the machine shell (301).

6. The three-stage dewatering and drying system for sludge in a domestic sewage treatment plant according to claim 6, wherein the hot air supply and recovery device comprises:

the system comprises a heat recovery device (3011), a moisture exhaust fan (3020), a wet cold air duct (3018), a refrigerant evaporator (3012), a dry cold air duct (3019), a wet warm air duct (308), a wet warm air duct dedusting device (309), a wet warm air duct ion deodorization device (3010), the dry hot air duct (307), a refrigerant condenser (3013), a compressor (3014), a cooling tower (3016), a refrigerant water condenser (3015) and a refrigerant expansion valve (3017); wherein the content of the first and second substances,

the heat recovery device (3011) is equipped with recovery port, hot air outlet, moisture exhaust port and return air inlet separately, the said circulation air outlet is connected with the said return air inlet through the said moisture exhaust blower (3020), wet cold wind channel (3018), refrigerant evaporator (3012) and dry cold wind channel (3019) connected sequentially;

the wet and warm air duct (308) is connected with a recovery port of the heat recovery device (3011) through the wet and warm air duct dust collector device (309) and the wet and warm air duct ion deodorization device (3010) in sequence;

a hot air outlet of the heat recovery device (3011) is connected with the dry hot air duct (307) through the refrigerant condenser (3013);

the outlet of the compressor (3014) is sequentially connected with the refrigerant water condenser (3015), the refrigerant condenser (3013), the refrigerant expansion valve (3017) and the refrigerant evaporator (3012) through pipelines and then is connected to the inlet of the compressor (3014);

the cooling tower (3016) is connected with the refrigerant water condenser (3015).

7. The system for dewatering and drying sludge in a domestic sewage treatment plant according to any one of claims 1 to 3, wherein the sludge cake conveying device (90) comprises:

the device comprises a shell (907), a feed inlet (902), a discharge outlet (903), a recycled hot air outlet (906), a recycled hot air inlet (905), a spiral blade (904) and a driving device (901); wherein the content of the first and second substances,

the top of the front end of the shell (907) is provided with the feed inlet (902), and the bottom of the rear end of the shell (907) is provided with the discharge outlet (903);

the front end and the rear end of the top of the shell (907) are respectively provided with a recycled hot air outlet (906) and a recycled hot air inlet (905);

the spiral blade (904) is arranged in the shell (907), the driving device (901) is arranged outside the rear end of the shell (907), and the driving device (901) is connected with the spiral blade (904) and can drive the spiral blade (904) to rotate in the shell (907) to convey mud cakes.

8. The system for three-stage dewatering and drying of sludge in a domestic sewage treatment plant according to any one of claims 1 to 3, wherein the heat recovery type dry sludge delivery subsystem (100) comprises: the system comprises a dry mud shaftless screw conveyor (1001), a lifting scraper conveyor (1002), a dry mud discharge hot air recovery pipeline (1003), a dry mud discharge hot air recovery pipeline dust removal device (1004) and a dry mud discharge hot air recovery micro negative pressure fan (1005); wherein the content of the first and second substances,

the discharge port of the dry sludge shaftless screw conveyor (1001) is connected with the lifting scraper conveyor (1002), and the discharge port of the lifting scraper conveyor (1002) is connected with the dry sludge bin (40);

the dry sludge discharging hot air recovery pipeline (1003) is respectively connected with an air suction opening in a dry sludge shaftless screw conveyor (1001) shell and an air suction opening in a lifting scraper conveyor (1002) shell, a dry sludge discharging hot air recovery pipeline dust removal device (1004) and a dry sludge discharging hot air recovery micro negative pressure fan (1005) are sequentially arranged on the dry sludge discharging hot air recovery pipeline (1003), and the outlet end of the dry sludge discharging hot air recovery pipeline (1003) is connected with the mud cake conveying equipment (90).

9. A three-stage dehydration and drying method for sludge in a domestic sewage treatment plant is characterized in that the three-stage dehydration and drying system for sludge in the domestic sewage treatment plant of any one of claims 1 to 8 is adopted, and comprises the following steps:

concentrating residual sludge with the water content of 99.2% of a domestic sewage treatment plant by using a short-time concentration tank (10) of the dehydration drying system to obtain primary concentrated sludge with the water content of 97-98%;

the primary concentrated sludge is conveyed to a high-pressure belt type dehydrator (20) of the dehydration and drying system through the dilute sludge conveying equipment (50), and is subjected to high-pressure dehydration under the action of a medicament input from the high-pressure belt type machine conditioning tank (60) through a high-pressure belt type machine flocculant dosing device (70) and a high-pressure belt type machine coagulant aid dosing device (80) to obtain a concentrated mud cake with the water content of 60-70%;

the concentrated mud cake is subjected to hot air drying and hot air recovery through a mud cake conveying device (90) and a heat recovery type hot air drier subsystem (30) of the dehydration drying system, so as to obtain final concentrated mud with the water content of below 40%;

and storing the final concentrated sludge into the dry sludge bin (40), thus finishing the three-stage dehydration and drying treatment of the sludge in the domestic sewage treatment plant.

10. The method for three-stage dewatering and drying of sludge in a domestic sewage treatment plant according to claim 10, wherein the sludge is dried in the sludge drying chamber,

the retention time of the short-time concentration tank (10) is 2-4 hours;

the pressure of the high-pressure belt type dehydrator (10) is 0.3-0.6 Mpa;

the dosing amount of the high-pressure belt machine flocculant dosing device (70) is 0.2-0.4% of the dry solid amount of the sludge, and the flocculant added by the high-pressure belt machine flocculant dosing device (70) adopts anionic polyacrylamide;

the dosing amount of the high-pressure belt type mechanical coagulant aid dosing device (80) is 8% -20% of the dry solid amount of the sludge, and the coagulant aid added by the high-pressure belt type mechanical coagulant aid dosing device (80) adopts ferric trichloride solution with the mass concentration of 38%.

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