CN213950944U

CN213950944U - Sludge drying system

Info

Publication number: CN213950944U
Application number: CN202021814637.1U
Authority: CN
Inventors: 陈菲琳; 章华熔; 张天兴; 彭存
Original assignee: Fujian Longking Co Ltd.
Current assignee: Fujian Longking Co Ltd.
Priority date: 2020-08-26
Filing date: 2020-08-26
Publication date: 2021-08-13
Anticipated expiration: 2030-08-26

Abstract

The utility model discloses a sludge drying system, which comprises a dryer, a sludge pump for pumping sludge to the dryer, and a dust remover positioned at the downstream side of a waste steam discharge port of the dryer; the system also comprises a jacket sludge preheating pipe, an inner sludge cavity and an outer heat exchange jacket which are nested; the sludge cavity is provided with a wet sludge feeding hole and a wet sludge discharging hole, the wet sludge feeding hole is communicated with an output port of the sludge pump, and the wet sludge discharging hole is communicated with a wet sludge inlet of the dryer; the heat exchange jacket is provided with a steam condensed water inlet and a steam condensed water outlet, and the steam condensed water inlet is communicated with the condensed water outlet of the dryer. By applying the scheme, the treatment efficiency of the dryer can be effectively improved, meanwhile, the heat consumption in the heat exchange and dehydration process after entering the dryer can be effectively reduced, and on the basis of reducing the heat loss, the using amount of a high-temperature steam source can be reduced, so that the process operation cost is reduced.

Description

Sludge drying system

Technical Field

The invention relates to the technical field of sludge treatment, in particular to a sludge drying system.

Background

Referring to fig. 4, a flow diagram of a typical prior art sludge drying system is shown. The sludge drying device comprises a wet sludge bin 1 ', a sludge pump 2', a dryer 3 ', a cyclone dust collector 4', a spray tower 5 ', a condensing heat exchanger 6', an induced draft fan 7 ', a spiral conveyor 8', a dry sludge conveying device 9 'and a dry sludge bin 10', and other auxiliary equipment and instruments.

In the drying process, wet sludge with higher water content is pumped into a dryer 3 ' through a sludge pump 2 ' to exchange heat with high-temperature steam for dehumidification, formed sludge with lower water content meeting the drying requirement falls into a sludge conveying system 9 ' through a screw conveyor 8 ', and finally stored into a dry sludge bin 10 ' for later use; introducing high-temperature steam into a central shaft and a shell of the drier 3', respectively exchanging heat with sludge with high water content, and discharging condensed water of the high-temperature steam out of the system after draining the condensed water; after the high-temperature steam and the sludge with high water content exchange heat sufficiently in the dryer 3 ', waste steam generated by the sludge enters the cyclone dust collector 4' along with a pipeline, dust in the waste steam is removed through a separation process in the cyclone dust collector 4 ', clean waste steam enters the spray tower 5' to reach a saturated state, then enters the condensation heat exchanger 6 'to exchange heat with cooling water, is cooled, condensed and dehumidified, then is sent to a subsequent treatment deodorization system, and finally is discharged to the atmosphere through the induced draft fan 7'; cooling water enters a condensing heat exchanger 6', and waste steam is discharged out of the system after being cooled and condensed; the waste water generated by the spray tower 5 'and the condensing heat exchanger 6' is pumped out of the system for treatment.

The temperature of high-temperature steam condensate generated by the operation of the existing drying system is about 100 ℃ and is directly discharged out of the system to cause heat source waste due to the limitation of the system principle.

In addition, the system needs to be provided with independent spray tower equipment, and the whole cost is high. Meanwhile, the dust removal efficiency of the cyclone dust collector in the system is unstable, only dust with larger particles (larger than 5 microns) which are lower than 70% in the flue gas can be removed, the temperature of waste steam generated by drying and evaporating the sludge is high (105 ℃) and high in moisture content (close to saturation), the dust removal efficiency is greatly reduced due to special properties, and the single use of the cyclone dust collector can influence the subsequent process and cannot meet the emission requirement of dust-containing gas.

In view of the above, a new approach is needed to provide an innovative solution for the conventional sludge drying system to overcome the above technical drawbacks.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problem, the utility model provides a sludge drying system to optimize make full use of high temperature steam condensate through the flow, effectively avoid the heat source extravagant. Additionally, the utility model provides a sludge drying system can also further overcome the unstable defect of dust collection efficiency.

The utility model provides a sludge drying system, which comprises a dryer, a sludge pump for pumping sludge to the dryer, and a dust remover positioned at the downstream side of a waste steam discharge port of the dryer; the system also comprises a jacket sludge preheating pipe, an inner sludge cavity and an outer heat exchange jacket which are nested; the sludge cavity is provided with a wet sludge feeding hole and a wet sludge discharging hole, the wet sludge feeding hole is communicated with an output port of the sludge pump, and the wet sludge discharging hole is communicated with a wet sludge inlet of the dryer; the heat exchange jacket is provided with a steam condensed water inlet and a steam condensed water outlet, and the steam condensed water inlet is communicated with the condensed water outlet of the dryer.

Preferably, the sludge cavity is internally provided with a spiral rotor so as to push wet sludge to be preheated in the cavity to move from the wet sludge feeding hole to the wet sludge discharging hole; and the spiral rotor is arranged along one side wall surface of the sludge cavity, a preheating evaporation tail gas accommodating space is formed between the spiral rotor and the other side wall surface of the sludge cavity, and the preheating evaporation tail gas accommodating space is output through a preheating waste gas outlet pipe.

Preferably, relative to the displacement direction of wet sludge to be preheated, the wet sludge feeding port and the steam condensed water outlet are positioned on the same side, and the wet sludge discharging port and the steam condensed water inlet are positioned on the same side.

Preferably, the system also comprises a low-temperature heat exchanger, and the dust remover is a wet electric dust remover; an inlet and an outlet of a gas passage of the low-temperature heat exchanger are respectively communicated with a waste steam outlet of the dryer and a gas inlet of the wet electric dust collector; and the inlet of the heat exchange passage of the low-temperature heat exchanger is communicated with the gas outlet of the wet electric dust collector.

Preferably, the outlet of the heat exchange passage of the low-temperature heat exchanger is communicated with a chimney and/or an inlet of a boiler blower.

Preferably, the inlet of the gas passage of the low temperature heat exchanger is also communicated with the preheated exhaust gas outlet pipe.

Preferably, the wet-type electric dust collector further comprises an odor treatment device, and a gas outlet of the wet-type electric dust collector can be selectively communicated to an inlet of the heat exchange passage of the low-temperature heat exchanger through the odor treatment device.

Preferably, the system also comprises a wastewater sedimentation tank, a water treatment device and a sludge concentration device, wherein a washing water outlet of the low-temperature heat exchanger and a spraying water outlet of the wet electric dust remover are communicated to the wastewater sedimentation tank, and a clarified water outlet of the wastewater sedimentation tank is communicated to the low-temperature heat exchanger and a water supplementing passage of the wet electric dust remover through the water treatment device; and a sludge outlet of the wastewater sedimentation tank is communicated to the wet sludge bin through the sludge concentration device.

Preferably, the low-temperature heat exchanger further comprises an induced draft fan, and the induced draft fan is arranged on a passage on the upstream side of an inlet of a heat exchange passage of the low-temperature heat exchanger.

Preferably, the system further comprises a screw conveyor, a dry sludge conveying device and a dry sludge bin which are sequentially arranged on the downstream side of a dry sludge discharge port of the dryer; the sludge pump is a screw pump or a plunger pump, and the dry sludge conveying device is a scraper, a bucket elevator or a belt conveyor.

To traditional sludge drying system, the utility model discloses the energy-saving sludge drying system that can effectively utilize the waste steam waste heat has creatively been provided. In the scheme, a jacket sludge preheating pipe is arranged on the upstream side of a wet sludge inlet of a dryer, and a steam condensed water inlet of a heat exchange jacket of the jacket sludge preheating pipe is communicated with a condensed water outlet of the dryer; when the system operates, wet sludge with high water content is conveyed to pass through the sludge cavity, indirectly exchanges heat with high-temperature steam condensate discharged through a condensate outlet of the dryer, and preheated wet sludge enters the dryer and indirectly exchanges heat with the high-temperature steam to reach low water content and then is discharged out of the dryer for storage and standby. So set up, the temperature of the high temperature steam condensate of desiccator exhaust is up to about 100 ℃, and this scheme make full use of the heat of high temperature steam condensate to preheat wet mud with this, construct first order waste heat recovery and utilize. Therefore, on one hand, the treatment efficiency of the dryer can be effectively improved, meanwhile, the heat consumption in the heat exchange and dehydration process after entering the dryer can be effectively reduced, and on the basis of reducing the heat loss, the use amount of a high-temperature steam source can be reduced, so that the process operation cost is reduced.

In the preferred scheme of the utility model, the spiral rotor is arranged in the sludge cavity to push the wet sludge to be preheated in the cavity to be displaced from the wet sludge feeding hole to the wet sludge discharging hole; for the displacement direction of wet sludge to be preheated, the wet sludge feeding hole and the steam condensate outlet are positioned on the same side, and the wet sludge discharging hole and the steam condensate inlet are positioned on the same side. In addition, a preheating evaporation tail gas accommodating space is formed between the spiral rotor and the wall surface of the sludge cavity, so that tail gas evaporated from wet sludge in the preheating process can be output through the accommodating space and the preheating waste gas outlet pipe, and then is subjected to subsequent treatment through the dust remover. Simple and reliable structure and better adaptability.

In another preferred scheme of the utility model, the dust remover is a wet-type electric dust remover, and the waste steam discharged by the dryer enters the wet-type electric dust remover after being subjected to heat exchange cooling through the low-temperature heat exchanger, is fully condensed in the dust remover, is cooled and dedusted, and can be demisted at the outlet of the dust remover through a mechanical synergistic electric demisting device; wherein, the entry of this low temperature heat exchanger's heat transfer route communicates with wet-type electrostatic precipitator's gas outlet, like this, through the exhaust dry noncondensable tail gas of wet-type electrostatic precipitator, is sent into low temperature heat exchanger's heat transfer route, constitutes second grade waste heat recovery and utilizes to discharge system behind the waste steam heat transfer with the front end desiccator production. Therefore, the heat utilization rate of the system can be further improved on the whole.

In another preferred scheme of the utility model, a wastewater sedimentation tank, a water treatment device and a sludge concentration device are additionally arranged, and in the running process of the system, the condensing, washing and spraying wastewater discharged by the low-temperature heat exchanger and the wet-type electric precipitator is pumped to the wastewater sedimentation tank; in the sedimentation tank, the lower floor deposits mud and gets back to wet sludge storehouse and wet sludge mixing treatment after the enrichment facility handles, wherein, the upper clear water after the sediment is as the circulating water behind water processing apparatus for the washing water and the shower water of low temperature heat exchanger and wet-type electrostatic precipitator are used, have realized the cyclic utilization of system water consumption from this to reduce the system water consumption, can further reduce technology running cost.

Drawings

FIG. 1 is a flow diagram of a sludge drying system in an embodiment;

FIG. 2 is a schematic diagram of the configuration of the jacketed sludge preheater tube shown in FIG. 1;

FIG. 3 is a cross-sectional view A-A of FIG. 2;

fig. 4 is a flow diagram of a typical sludge drying system of the prior art.

In fig. 1-3:

the system comprises a wet sludge bin 1, a sludge pump 2, a jacket sludge preheating pipe 3, a sludge cavity 31, a wet sludge feeding hole 311, a wet sludge discharging hole 312, a preheating evaporation tail gas accommodating space 313, a heat exchange jacket 32, a steam condensed water inlet 321, a steam condensed water outlet 322, a screw rotor 33, a preheating waste gas outlet pipe 34, a dryer 4, a low-temperature heat exchanger 5, a wet electric dust collector 6, an odor treatment device 7, an induced draft fan 8, a wastewater sedimentation tank 9, a water treatment device 10, a screw conveyor 11, a dry sludge conveying device 12, a dry sludge bin 13, a sludge concentration device 14, a chimney 15 and a boiler blower inlet 16.

Detailed Description

In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

Referring to fig. 1, a flow diagram of a sludge drying system according to the present embodiment is shown.

The sludge drying system comprises a wet sludge bin 1, a sludge pump 2 and a dryer 4, wherein the sludge pump 2 can pump wet sludge in the wet sludge bin 1 to the dryer 4, and the sludge pump 2 preferably adopts a screw pump or a plunger pump; for example, but not limited to, the dry sludge dehydrated by heat exchange via the dryer 4 may be sequentially transferred to a dry sludge bin 13 via a screw conveyor 11 and a dry sludge transfer device 12 disposed at the downstream side of the dry sludge discharge port of the dryer 4, and stored for later use, where the sludge transfer device 12 may be a scraper, a bucket elevator or a belt conveyor. Wherein, a wet-type electric dust collector 6 is arranged at the downstream side of the exhaust steam outlet of the dryer 4 to fully condense, cool and remove dust for the exhaust steam.

In this embodiment, a jacket sludge preheating pipe 3 is disposed upstream of the wet sludge inlet of the dryer 4. The jacket sludge preheating pipe 3 is provided with an inner sludge cavity 31 and an outer heat exchange jacket 32 which are nested; referring to fig. 2 and 3 together, fig. 2 shows a schematic structure of a jacketed sludge preheating pipe, and fig. 3 is a sectional view a-a of fig. 2.

Wherein, a wet sludge inlet 311 of the sludge cavity 31 is communicated with an output port of the sludge pump 2, a wet sludge outlet 312 of the sludge cavity 31 is communicated with a wet sludge inlet of the dryer 4, and a wet sludge preheating channel is formed; wherein, the steam condensed water inlet 321 of the heat exchange jacket 32 is communicated with the condensed water outlet of the dryer 4. That is, the inner pipe of the jacketed sludge preheating pipe 3 is filled with sludge, and the outer interlayer is filled with steam condensate. Therefore, the heat of the high-temperature steam condensate is utilized to construct the first-stage waste heat recycling. Here, the steam condensate after heat exchange can be recovered from the system through the steam condensate outlet of the heat exchange jacket 32.

When the system is operated, wet sludge with high water content of 60-80% is conveyed to pass through the sludge cavity 31, indirectly exchanges heat with 100 ℃ high-temperature steam condensate discharged through a condensate outlet of the dryer 4, the wet sludge preheated to 40 ℃ enters the dryer 4, indirectly exchanges heat with 150-180 ℃ high-temperature steam with 0.5-0.8 MPa to low water content of 30-40%, and then is discharged out of the dryer 4 for storage and standby. The system is based on the configuration of the jacket sludge preheating pipe 3, wet sludge is preheated before entering the dryer 4, and the treatment efficiency of the dryer can be effectively improved; meanwhile, on the basis of reducing heat loss, the first-stage waste heat recovery can reduce the using amount of a high-temperature steam source in the dryer, and the heat consumption in the process of heat exchange and dehydration can be effectively reduced, so that the process operation cost is reduced.

It should be noted that the specific values of the water content, the temperature, the pressure, and the like mentioned above, including the specific parameter values mentioned below, are only preferred exemplary illustrations, and it should be understood that the specific values are only used for clearly explaining the corresponding working principle, and do not substantially limit the technical solution claimed in the present application.

In order to improve the utilization rate of the preheating heat, preferably, the sludge cavity 31 is internally provided with a spiral rotor 33 to push wet sludge to be preheated in the cavity to be displaced from a wet sludge inlet 311 to a wet sludge outlet 312; relative to the displacement direction of the wet sludge to be preheated, the wet sludge feed port 311 and the steam condensate outlet 322 are located on the same side, and the wet sludge discharge port 312 and the steam condensate inlet 321 are located on the same side. Thus, the wet sludge is displaced in the sludge cavity 31 by the pushing of the screw rotor 33, and the displacement direction of the wet sludge is opposite to the flowing direction of the steam condensate for preheating, so that the utilization rate of the waste heat can be improved to the maximum extent.

Of course, the length of the heat exchange jacket 32 covers the outside of the sludge cavity 31 between the wet sludge feeding port 311 and the wet sludge discharging port 312, and the heat exchange area between the two ports is best adapted.

Further, the screw rotor 33 is disposed along one side wall surface of the sludge cavity 31, and forms a preheating evaporation tail gas accommodating space 313 with the other side wall surface of the sludge cavity, and the preheating evaporation tail gas accommodating space 313 is output through the preheating waste gas outlet pipe 34. Therefore, the tail gas evaporated from the wet sludge in the preheating process can be output through the accommodating space 313 and the preheating waste gas outlet pipe 34, and further subjected to subsequent treatment through a dust remover.

Preferably, the dust collector in the scheme is a wet-type electric dust collector 6, and a low-temperature heat exchanger 5 is arranged between the dryer 4 and the wet-type electric dust collector 6 so as to ensure the optimal operation condition of the wet-type electric dust collector 6. For example, but not limiting of, the cryogenic heat exchanger 5 may be a finned heat exchanger or a shell and tube heat exchanger.

As shown in fig. 1, the inlet of the gas passage of the low-temperature heat exchanger 5 is communicated with the waste vapor discharge port of the dryer 4, and the outlet of the gas passage of the low-temperature heat exchanger 5 is communicated with the gas inlet of the wet electric dust collector 6; the inlet of the heat exchange passage of the low-temperature heat exchanger 5 is communicated with the gas outlet of the wet electric dust collector 6. In this way, the 30 ℃ dry noncondensable tail gas discharged by the wet electric dust collector 6 is sent to a heat exchange passage of the low-temperature heat exchanger 5 to construct a second-stage waste heat recycling system to exchange heat with 100 ℃ waste steam generated by the front-end dryer 4 to 50 ℃ and discharge the heat; and after the waste steam at the temperature of 100 ℃ is cooled to 60 ℃, the waste steam enters the wet electric dust collector 6, SO that the wet electric dust collector 6 can operate under the optimal condition and the effect of removing part of SO3 in the waste gas can be ensured, and meanwhile, the temperature of the 30 ℃ low-temperature dry tail gas is raised to an unsaturated state, SO that the effect of no white smoke in the tail gas emission is achieved. The dust remover is fully condensed, cooled and dedusted, and the demisting can be carried out at the outlet of the dust remover through a mechanical and electric demisting device. Therefore, the heat utilization rate of the system can be further improved on the whole. This scheme adopts 6 dust removal effects of wet-type electrostatic precipitator to reach below 1mg/m3, has improved dust collection efficiency greatly, and spray water in the dust remover simultaneously, direct contact condensation has replaced the indirect contact condensation of shell and tube type of traditional handicraft and has also improved condensation efficiency greatly. Compared with the configuration of the traditional cyclone dust collector, the spray tower and the condensing heat exchanger, the dust collector has the advantages that the number of devices is reduced on the basis of obtaining a good dust removing effect.

In order to further improve the adaptability of the system, an odor treatment device 7 can be further arranged, and a gas outlet of the wet electric dust collector 6 can be selectively communicated to an inlet of a heat exchange passage of the low-temperature heat exchanger 5 through the odor treatment device 7. That is, if the system is applied in a power plant, the dry tail gas at 30 ℃ does not need to be treated by the odor treatment device 7, and is directly sent to the low-temperature heat exchanger 5 through the induced draft fan 8 to exchange heat with the waste steam at 100 ℃ to 50 ℃, and then sent to the inlet 16 of the boiler blower to be treated and discharged as primary air after entering the hearth for incineration. This draught fan 8 disposes on the entry upstream side passageway of low temperature heat exchanger 5's heat transfer route, makes the inside dry tail gas side of low temperature heat exchanger 5 be the malleation, and the exhaust steam side is the negative pressure, and exhaust steam can't reveal to dry tail gas side, guarantees that the tail gas after handling does not receive the pollution. Referring to the path shown by the dotted line in fig. 1, correspondingly, the outlet of the heat exchange passage of the low-temperature heat exchanger 5 is communicated with the chimney 15 and/or the boiler blower inlet 16, and the selective communication can be performed according to the actual system operation condition.

During the specific application, on equipment pipelines such as sludge pump 2, 4 low temperature heat exchanger 5 of desiccator, wet-type electrostatic precipitator 6, draught fan 8, foul smell processing apparatus 7, can all be equipped with manometer, thermometer and flowmeter detecting system operation condition to carry out adjustment control according to the whole operation condition of system.

Of course, the inlet of the gas passage of the low-temperature heat exchanger 5 is also communicated with the preheated waste gas outlet pipe 33 of the jacket sludge preheating pipe 3, that is, waste steam generated by preheating in the jacket sludge preheating pipe 3 and heat exchange in the dryer 4 is collected to the low-temperature heat exchanger 5 and the wet electric dust collector 6 for subsequent dust removal treatment. Compared with the traditional cyclone dust collector, the scheme can obtain stable dust removal efficiency so as to ensure the emission requirement of dust-containing gas of the subsequent treatment process.

In addition, the corresponding configuration can be performed from the perspective of further energy saving. As shown in fig. 1, the system may further include a wastewater sedimentation tank 9, a water treatment device 10 and a sludge concentration device 14, specifically, a rinsing water outlet of the low-temperature heat exchanger 5 and a spraying water outlet of the wet electric dust collector 6 are communicated to the wastewater sedimentation tank 9, wherein after being treated by the water treatment device 10, an upper layer clarified water outlet of the wastewater sedimentation tank 9 is communicated to a water replenishing passage of the low-temperature heat exchanger 5 and the wet electric dust collector 6; the lower layer sludge outlet of the wastewater sedimentation tank 9 is communicated and conveyed to the wet sludge bin 1 through a sludge concentration device 14, and enters the system treatment process again. So set up, realized the cyclic utilization of system water from this, the concentrated waste water discharge system of few part that the in-process produced carries out a small amount of moisturizing according to the circulating water volume requirement can to effectively reduce system water consumption, reduce technology running cost.

Without loss of generality, the operating parameter values of the preferred embodiment described above are merely illustrative to clearly and briefly illustrate the operating philosophy of the system. It should be understood that the specific structure of the functions of the low-temperature heat exchanger, the wet electric dust collector 6 and the like in the system is not the core invention point of the present application, and can be realized by those skilled in the art based on the prior art, so that the detailed description is omitted here.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that it is obvious to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and these modifications and improvements should also be considered as the protection scope of the present invention.

Claims

1. A sludge drying system includes a dryer, a sludge pump that pumps sludge to the dryer, and a dust remover located on a downstream side of a waste vapor discharge port of the dryer; it is characterized by also comprising:

the jacket sludge preheating pipe is provided with an inner sludge cavity and an outer heat exchange jacket which are nested; the sludge cavity is provided with a wet sludge feeding hole and a wet sludge discharging hole, the wet sludge feeding hole is communicated with an output port of the sludge pump, and the wet sludge discharging hole is communicated with a wet sludge inlet of the dryer; the heat exchange jacket is provided with a steam condensed water inlet and a steam condensed water outlet, and the steam condensed water inlet is communicated with the condensed water outlet of the dryer;

the sludge cavity is internally provided with a spiral rotor so as to push wet sludge to be preheated in the cavity to move from the wet sludge feeding hole to the wet sludge discharging hole; and the spiral rotor is arranged along one side wall surface of the sludge cavity, a preheating evaporation tail gas accommodating space is formed between the spiral rotor and the other side wall surface of the sludge cavity, and the preheating evaporation tail gas accommodating space is output through a preheating waste gas outlet pipe.

2. The sludge drying system of claim 1, wherein the wet sludge feed port and the steam condensate outlet are located on the same side, and the wet sludge discharge port and the steam condensate inlet are located on the same side, with respect to a displacement direction of wet sludge to be preheated.

3. The sludge drying system of claim 1 or 2, further comprising a low temperature heat exchanger, wherein the dust remover is a wet electric dust remover; an inlet and an outlet of a gas passage of the low-temperature heat exchanger are respectively communicated with a waste steam outlet of the dryer and a gas inlet of the wet electric dust collector; and the inlet of the heat exchange passage of the low-temperature heat exchanger is communicated with the gas outlet of the wet electric dust collector.

4. The sludge drying system of claim 3 wherein the outlet of the heat exchange passage of the cryogenic heat exchanger is in communication with a chimney and/or a boiler blower inlet.

5. The sludge drying system of claim 3 wherein the inlet of the gas passage of the cryogenic heat exchanger is further in communication with the preheated exhaust gas outlet pipe.

6. The sludge drying system of claim 3, further comprising an odor treatment device, wherein a gas outlet of the wet electric precipitator is selectively communicated to an inlet of the heat exchange passage of the cryogenic heat exchanger through the odor treatment device.

7. The sludge drying system of claim 6, further comprising a wastewater sedimentation tank, a water treatment device and a sludge concentration device, wherein a washing water outlet of the low-temperature heat exchanger and a spraying water outlet of the wet electric dust remover are communicated to the wastewater sedimentation tank, and a clarified water outlet of the wastewater sedimentation tank is communicated to the low-temperature heat exchanger and a water replenishing passage of the wet electric dust remover through the water treatment device; and a sludge outlet of the wastewater sedimentation tank is communicated to the wet sludge bin through the sludge concentration device.

8. The sludge drying system according to claim 7, further comprising an induced draft fan disposed on an inlet upstream side passage of the heat exchange passage of the low temperature heat exchanger.

9. The sludge drying system according to claim 1, further comprising a screw conveyor, a dry sludge conveying device and a dry sludge bin which are arranged in sequence on the downstream side of the dry sludge discharge port of the dryer; the sludge pump is a screw pump or a plunger pump, and the dry sludge conveying device is a scraper, a bucket elevator or a belt conveyor.