Large-scale sludge disposal system based on deep utilization of low-grade heat energy

Abstract

The present application belongs to the technical field of wet sludge disposal and energy recycling, and particularly relates to a large-scale sludge disposal system based on deep utilization of low-grade heat energy, which comprises a treatment system for drying and incinerating sludge, a low-grade heat energy recovery system for recovering sludge incineration heat, a low-grade heat energy deep heat exchange system for deep heat exchange of process heat, and a deep utilization and consumption system for deep utilization of process heat. The present application fully recycles low-grade heat energy from different point sources in the production link of a thermal power plant according to the characteristics and attributes of the low-grade heat energy, saves high-quality steam, realizes energy cascade utilization, and has better economic benefits.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wet sludge disposal and energy recycling, and particularly relates to a large-scale sludge disposal system based on deep utilization of low-grade heat energy. BACKGROUND

[0002] With the acceleration of urbanization and industrialization in China, the annual production rate and discharge amount of municipal sewage treatment plant sludge have increased dramatically. The planning outline points out that the full coverage of urban sewage network should be promoted, the differential precision upgrading of sewage treatment should be carried out, the centralized incineration harmless treatment of sludge should be popularized, the harmless disposal rate of urban sludge reaches 90%, the sewage resource utilization rate of cities at the prefecture level and above exceeds 25%, and the sludge is preferentially disposed by using sludge thermal drying, sludge incineration, anaerobic digestion and other methods. As the sludge drying and incineration disposal technology is the most suitable sludge disposal technology and process route for sludge reduction, harmless, stabilization, resource utilization and standardization, it has a strong processing capacity, a small occupied area and a wide application. Patent CN102153256A proposes a sludge drying and incineration system, but the heat source comes from low-pressure steam 0.8Mpa, 280℃, the steam consumption of the thermal drying system is large, the quality requirement is high, the steam and water heat is not effectively utilized, the carbon emission is high, and the orderly development is hindered. At the same time, the sludge drying and incineration is often coupled with coal-fired power generation for large-scale collaborative consumption, and the flue gas emission adopts ultra-low emission process. For example, patents CN104759192A and CN109621661B propose a low-cost coal-fired flue gas multi-pollutant ultra-low emission system and method, which realizes the advanced flue gas purification technology with flue gas pollutant emission concentration PM less than 5mg / Nm3, SO2 less than 35mg / Nm3 and NOX less than 50mg / Nm3, but the sludge incineration leads to high moisture content of the fuel into the furnace, which further expands the heat loss of flue gas emission, the flue gas heat at the tail of the dust remover and the desulfurization tower is not effectively recovered, the water resource consumption of the wet desulfurization process is huge, and the boiler efficiency continues to decrease. Patent CN111482071B proposes a sintering flue gas multi-pollutant collaborative purification and waste heat utilization system and process, which can further recover the waste heat in the flue gas, but does not fully solve the contradiction between the flue gas waste heat system and the low-temperature heater of the power plant boiler, and the problems of waste heat consumption and water balance. It has certain regional characteristics. In addition, compressed air is widely used in the textile industry in many aspects such as pneumatic pressurization, pneumatic weft insertion, airflow jet twisting, pneumatic humidification, airflow conveying, airflow cleaning, pneumatic doffing and instrument automatic control. For example, CN111778619B invents a jet loom, which has the characteristics of environmental friendliness, precision and high fabric quality, but the gas source is widely obtained by using a screw compressor, which has high energy consumption and is not conducive to the development of low-carbon economy. SUMMARY

[0003] The present application solves the above problems based on a large-scale sludge disposal system for deep utilization of low-grade heat energy.

[0004] The present application adopts the following technical solutions:

[0005] The large-scale sludge disposal system for deep utilization of low-grade heat energy comprises a treatment system for drying and incinerating sludge, a low-grade heat energy recovery system for recovering sludge incineration heat, a low-grade heat energy deep heat exchange system for deep heat exchange of process heat, and a deep utilization and consumption system for deep utilization of process heat.

[0006] In the above scheme, multiple systems are integrated to recover and utilize low-grade heat energy at multiple sites of a thermal power plant, thereby achieving better economic benefits.

[0007] As a preferred, the low-grade heat energy recovery system comprises a flue gas low-grade heat energy recovery system for treating sludge incineration flue gas, which comprises a wet electric dust collector, a coal economizer in communication with the wet electric dust collector, a desulfurization tower in communication with the coal economizer, a flue gas condenser in communication with the desulfurization tower, an oxygen remover in communication with the coal economizer, and a desalted water tank.

[0008] As a preferred, the low-grade heat energy recovery system further comprises a low-grade heat energy recovery system for exhaust steam, which mainly recovers exhaust steam heat from boiler fixed exhaust, combined exhaust, driving machine shaft seal leakage, gate rod leakage, etc.

[0009] As a preferred, the low-grade heat energy recovery system for exhaust steam comprises an exhaust steam recovery device for receiving exhaust steam, and a surface heat exchanger and a drain tank in communication with the exhaust steam recovery device, respectively, the surface heat exchanger is in communication with the desalted water tank, a first water conveying pipeline and a second water conveying pipeline are arranged between the exhaust steam recovery device and the surface heat exchanger, high-temperature desalted water in the exhaust steam recovery device is conveyed to the surface heat exchanger for heat exchange through the first water conveying pipeline, and the desalted water is returned to the exhaust steam recovery device through the second water conveying pipeline after heat exchange and cooling for reuse as secondary steam absorption water, a third water conveying pipeline for conveying low-temperature desalted water is arranged between the surface heat exchanger and the desalted water tank, and a fourth water conveying pipeline is connected between the surface heat exchanger and the oxygen remover, and the low-temperature desalted water is discharged through the fourth water conveying pipeline after heat exchange and temperature rise.

[0010] As preferred, the steam exhaust recovery device is communicated with the drain tank through a drain pipeline, the drain pipeline comprises a communicated detection section, a direct drain section and a recovery section, the detection section is communicated with the steam exhaust recovery device, the detection section is provided with a first control valve for controlling on-off, a first high-temperature water pump and a detection device for monitoring whether the water quality meets the boiler feed water requirement, the recovery section is connected with the third water conveying pipeline, the recovery section is provided with a second control valve for controlling on-off, the direct drain section is provided with a third control valve for controlling on-off, the first control valve, the second control valve, the third control valve and the detection device are connected with a controller, when the detection device detects that the water quality is qualified, the second control valve is opened, the water path of the recovery section is conducted, the high-temperature desalted water in the steam exhaust recovery device is conveyed to the third water conveying pipeline for mixing and use, otherwise the direct drain section is conducted to directly drain out, the steam exhaust recovery device is connected with the desalted water tank through a water supplement pipeline for supplementing low-temperature desalted water.

[0011] As preferred, the deep utilization and accommodation system comprises a high-temperature heater communicated with a deaerator, and the deaerator is further communicated with a drying machine for drying sludge.

[0012] By implementing the above technical scheme, the present application has the following beneficial effects:

[0013] The present application fully recycles and utilizes low-grade heat energy according to the characteristics and properties of low-grade heat energy from different point sources in the production process of a thermal power plant, saves high-quality steam, realizes energy cascade utilization, and has better economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 A flow chart of recycling and utilizing heat by using the system of the present application;

[0015] Figure 2 A structural schematic view of the system of the present application. DETAILED DESCRIPTION

[0016] The system of the present application will be described in more detail below in combination with the drawings and specific embodiments.

[0017] EMBODIMENT

[0018] The large-scale sludge disposal system based on deep utilization of low-grade heat energy provided in the embodiment comprises a low-grade heat energy recovery system s1 for recovering sludge incineration heat, a low-grade heat energy deep heat exchange system s2 for deeply exchanging process heat, and a deep utilization and accommodation system s3 for deeply utilizing process heat, and the low-grade heat energy recovery system of the present application is divided into a flue gas low-grade heat energy recovery system s11 and a steam exhaust low-grade heat energy recovery system s12 according to the characteristics and properties of different point sources of low-grade heat energy.

[0019] The s11 flue gas low-grade heat energy recovery system is:

[0020] It has a corrosive atmosphere and has strong viscosity, which is easy to cause corrosion and dust accumulation of heat exchanger. The flue gas from the shaft flue is removed by s111 wet electric precipitator, and the dust in the flue gas is removed by low temperature coal economizer s112, and then s113 wet desulfurization, and then s114 flue gas condenser, and then through s115 chimney to the atmosphere, at this time the waste heat in the flue gas is fully recovered, and the pollutants are effectively removed.

[0021] The above process river water is stored in desalted water tank 29 after deep desalination, and is pressurized by desalted water pump 30, and the desalted water at room temperature and 0.9Mpa is heated to 55℃ in the flue gas cross flow heat exchange parameter of wet desulfurization flue gas condenser 19 and 20, and absorbs heat Q1. The water dew point calculation formula is:

[0022]

[0023] Q1=q m,w c p Δt COD

[0024]

[0025]

[0026] Where p s is the saturation vapor pressure corresponding to the water dew point of flue gas; Q1 is the heat exchange capacity of condenser; Δ tCOD is the temperature rise of cooling water in condenser; Δ tm,COD is the logarithmic mean temperature difference of condenser; A COD is the heat exchange area of condenser; k COD is the heat transfer coefficient of condenser.

[0027] At this time, the water dew point of flue gas is lower than the temperature of desalted water in condenser, and condensation heat exchange always occurs below the water dew point, and the wet desulfurization condensate is recovered while the waste heat of flue gas is recovered, Q1=Q 烟气显热 +Q 烟气潜热 , the flue gas temperature is low but has undergone phase change, and the share of waste heat recovery also accounts for more than 40% of the system recovered heat. After the above heat exchange, the desalted water is heated again by low temperature coal economizer 21 before the absorption tower and the flue gas 22 after wet dust removal, and the temperature of desalted water is raised to 106℃, and the heat Q2 is absorbed. Recovered to 14 rotary membrane deaerator, at this time, the flue gas can be condensed gas is less, mainly in the form of sensible heat exchange.

[0028]

[0029] Q2=q m,w cp Δt LE

[0030]

[0031]

[0032] t da For the flue gas acid dew point; t d For the flue gas water dew point; S ar,red And A ar,red The equivalent sulfur content and ash content of the fuel, respectively, α fa The fly ash coefficient; Q2 is the heat exchange of the low-temperature economizer; q m,w The cooling water flow rate; c p The specific heat capacity of water; Δ tLE The temperature rise of the cooling water in the low-temperature economizer; Δ tm,LE The logarithmic mean temperature difference of the low-temperature economizer; T fg,in And T fg,out The flue gas inlet and outlet temperatures, respectively; T w,in And T w,in The cooling water inlet and outlet temperatures, respectively; k LE The low-temperature economizer heat transfer coefficient; A LE The heat exchange area of the low-temperature economizer.

[0033] After the above two-stage heat exchange, the remaining heat in the flue gas has been mostly recovered. The desalted water pressure has been reduced to 0.6 Mpa and enters the deaerator 14, and then further deaerates and exchanges heat in the mixed heat exchanger deaerator to become 0.55 Mpa, 160℃ superheated steam with a certain degree of superheat. The above process desalted water first flows through the flue gas condenser 19 arranged at the rear of the wet electrostatic precipitator to be warmed up, and then transported to the low-temperature economizer 21 for secondary warming. The warmed desalted water finally enters the deaerator 14 through the main pipe. The heat in the flue gas is recovered and utilized, saving the energy required to heat the desalted water. A water baffle is provided at the bottom of the low-temperature economizer near the electrostatic precipitator side to prevent condensate from flowing into the induced draft fan. At the same time, a drain is provided at this side to drain to the trench recovery system; while an expansion joint is used for drainage near the absorption tower side, and the return flow to the absorption tower. These moisture mainly comes from the moisture in the coal m1, the water generated by the combustion of hydrogen in the coal m2, the moisture brought into the boiler with the air m3, and the part of the process water evaporated in the wet desulfurization process m4. Part of the oxidation air in the wet desulfurization process also enters the flue gas, but this part accounts for less than 1% compared with the boiler combustion air, which is negligible. Among them,

[0034]

[0035]

[0036] m3=1.61d k ∝V 0 ,

[0037] Moisture content:

[0038]

[0039] Theoretical dry air quantity

[0040]

[0041] The water vapor evaporation quantity of the wet desulfurization process can be obtained by subtracting the water content m1 in the coal, the water m2 generated by the combustion of hydrogen in the coal, and the water m3 brought into the boiler with the air from the saturated steam of the flue gas at the outlet of the desulfurization tower.

[0042]

[0043] wherein the water vapor fraction at the outlet of the desulfurization tower,

[0044]

[0045] wherein C ar , H ar , O ar , S ar , and M ar are the received basis mass percentages of carbon, hydrogen, oxygen, sulfur, and total moisture in the coal, respectively, is the excess air coefficient, p s is the water vapor saturation pressure corresponding to the ambient temperature, Pa; p t is the atmospheric pressure, Pa; Q y is the flue gas quantity, Nm 3 ; m is the fuel quantity, Kg; tsld is the saturated wet flue gas temperature, ℃; and P y is the flue gas pressure at the outlet of the desulfurization tower, Pa.

[0046] After the above calculation, affected by the degree of sludge drying, the water content in the wet flue gas is the largest, followed by the water content generated by the combustion of hydrogen in the coal and the water evaporation part of the wet desulfurization process, and the water content brought in by the air is the smallest. The above-mentioned links solve the problem of industrial water consumption caused by the use of the wet desulfurization process of the patent CN104759192A and CN109621661B.

[0047] In addition, the temperature in the above-mentioned flue gas low-grade heat energy recovery process is lower than the acid dew point, low-temperature corrosion will occur, the patent adopts fluoroplastic melting coating technology to prevent the corrosion of sulfuric acid condensate on the heat exchange tube. Sulfuric acid condensate and ammonium bisulfate caused by ammonia escape have strong viscosity, which is easy to bridge and cause cohesive dust deposition on the surface of the heat exchange tube. In order to avoid this, the patent regularly cleans the dust deposition on the surface of the heat exchange tube by using acetylene acoustic wave impact soot blowing method, so as to alleviate the heat transfer deterioration phenomenon and the increase of flow resistance caused by dust deposition. The temperature of flue gas is further reduced in the condenser, at this time the temperature of the tube wall is lower than the water dew point, a large amount of water in the flue gas is condensed, and the water content of the flue gas is reduced. The condensed water produced by condensing flue gas in the condenser enters the condensate tank through the drain pump and is transported to the cooling tower, realizing the recycling of water.

[0048] For the s12 steam low-grade heat energy recovery system:

[0049] s12 does not have a corrosive atmosphere and no dust compared to s11, exists in gaseous, liquid, has strong expansibility, but the parameter span is large. It is mainly related to boiler fixed emission, combined emission, drive shaft seal leakage, door rod leakage. Based on the above characteristics, an efficient fixed emission expansion vessel steam recovery equipment based on energy multi-level utilization is proposed, the steam 15 is expanded, decompressed, heat exchanged, and then discharged. The system comprises a steam recovery device 16, a surface heat exchanger 18 and a drain tank 39, the heat source of the steam recovery device enters the steam recovery device 16 through the gas guide pipe, a first water conveying pipeline 17 and a second water conveying pipeline 37 are arranged between the steam recovery device and the surface heat exchanger, high-temperature desalted water in the steam recovery device is conveyed to the surface heat exchanger for heat exchange on the first water conveying pipeline, and the desalted water is returned to the steam recovery device again through the second water conveying pipeline after heat exchange and cooling to be used repeatedly as secondary steam absorption water, a third water conveying pipeline 38 for conveying low-temperature desalted water is arranged between the surface heat exchanger and the desalted water tank, a fourth water conveying pipeline is connected between the surface heat exchanger and the deaerator 14, low-temperature desalted water is discharged through the fourth water conveying pipeline after heat exchange and temperature rise, the steam recovery device is further connected with a drain pipeline 28, the drain pipeline comprises a detection section, a direct discharge section and a recovery section which are communicated, the detection section is communicated with the steam recovery device, a first control valve for controlling on-off, a first high-temperature water pump and a detection device for monitoring whether the water quality meets the requirements of boiler feed water are arranged on the detection section, the recovery section is connected with the third water conveying pipeline, a second control valve for controlling on-off is arranged on the recovery section, a third control valve for controlling on-off is arranged on the direct discharge section, the first control valve, the second control valve, the third control valve and the detection device are connected with a controller, the detection device detects qualified, the second control valve is opened, the water path of the recovery section is conducted, the high-temperature desalted water in the steam recovery device is conveyed to the third water conveying pipeline for mixing and use, otherwise the direct discharge section is conducted to discharge directly, the steam recovery device and the desalted water tank are connected with a water supplement pipeline 27 for supplementing low-temperature desalted water.

[0050] The qualified exhaust steam is recovered to the deaerator, and the exhaust steam temperature has a value h". The exhaust steam heat and working medium are all absorbed by the condensed water without heat loss, and the value is h'. The recovered heat is Q1:

[0051] Q3 = h" - h'

[0052] The detection section is based on the water quality conductivity and hardness sensor to realize the exhaust steam direct discharge section or recovery. If the monitoring degree of conductivity and hardness does not meet the furnace water index, it is delivered to the water delivery tank as a domestic water heat source 34.

[0053] For the s3 depth utilization and consumption system:

[0054] Most of the steam at the deaerator outlet enters the high-temperature heater 12, and the excess steam is delivered to the rotating shaft of the disc dryer 23 through the pipeline, mainly through the bidirectional rotating joint, which contains a steam inlet and a condensed water outlet 2 channels, and is installed on the hollow shaft driven side shaft head end surface. The unidirectional rotating joint contains a steam inlet channel and is installed on the hollow shaft (drive side) shaft head end surface. Thus, the disc dryer steam input and condensed water discharge are realized. The low-grade heat value of the large-scale sludge disposal system based on low-grade heat energy deep utilization is collected through the above steps, and is preliminarily converted into 0.5Mpa, 152℃ saturated steam. The latent heat is released by the disc dryer to dry the sludge. The effective heat exchange is carried out by the adjustable static blade throwing knife on the top of the dryer dome in cooperation with the dynamic blade stirring to prevent the air resistance phenomenon caused by the expansion in the disc. The wet sludge is preliminarily dried by the disc dryer, and the wet sludge 24 with a moisture content of 80% is reduced to dry sludge 25 with a moisture content of 40%. The steam is separated into water vapor by the float valve 26 to become atmospheric pressure 90℃ hydrophobic. The hydrophobic further dries the sludge through the heat recovery pipe heating 35 at the bottom of the scraper machine. The sludge with a moisture content of 40% is further separated into water vapor in the scraper machine with a moisture content of 30% by heating and blowing cold water. The hydrophobic temperature is reduced to 65℃, and the hydrophobic further releases the sensible heat, which is delivered 31 to the hydrophobic tank 39 for collection by the condensed water pump. The sludge is recovered by quality. By using the above multi-stage sludge drying technology, the high temperature of the original condensed water cannot be effectively utilized, and the heat recovery and heat treatment process is proposed to further utilize the condensed water waste heat, further reduce the moisture content of the sludge, and prevent the problem of large-scale consumption of sludge hardening and moisture return. At the same time, the sludge drying equipment and key feeding, conveying and mixing equipment of the whole system are selected to improve the sludge combustion heat value, so that the sludge drying process is more continuous, the energy consumption is lower, and the adaptability to sludge types is stronger, and the energy comprehensive utilization efficiency is improved.

[0055] The low-grade heat value of the large-scale sludge disposal system based on deep utilization of low-grade heat energy is heated by the deaerator, and after being pressurized by the pneumatic pump 13, it enters the high-temperature heater 12, which is further heated. The pressure and temperature are changed to 190℃ and 14Mpa. The high-temperature heater 12 uses two-stage heating. The heating source of the first stage is the 2-stage extraction steam of the steam turbine 2, and the heating source of the second stage is the 2-stage extraction steam. After heat exchange by the high-efficiency heat exchanger 12, 36 enters the deaerator 14 for heat recovery. After being heated and pressurized, the working medium enters the high-pressure feedwater hot main pipe to enter the circulating fluidized bed to absorb heat and generate high-temperature and high-pressure steam 9.8Mpa, 540℃, which enters the steam main pipe 01, enters the condensing turbine generator set 02, the back pressure turbine generator set 03, the back pressure centralized compressed air supply set 04, the condensing centralized compressed air supply set 05, the back pressure centralized compressed air supply set exhaust 04, the back pressure turbine generator set 03 and the condensing turbine generator set 02. The middle-stage extraction steam of the condensing turbine generator set 02 is used as a heat source for the heat network, providing 0.8Mpa-1.3Mpa, 270-300℃ low-pressure steam, 2.8Mpa-3.5Mpa, 270-300℃ medium-pressure steam, 2.25Mpa-2.55Mpa, 270-300℃ high-pressure steam and 0.8Mpa-0.9Mpa, 40℃ compressed air for the user 06 to select. At the same time, the medium-pressure heat pipe network is highly coupled with the condensing centralized compressed air supply set 05 and the back pressure centralized compressed air supply set exhaust 04, which can supply air in the positive direction or in the reverse direction. The high-quality new steam is saved, the boiler efficiency is improved, and water resources are recovered. 07 and 10 are condensing turbine regenerators, which further absorb the heat of the condensate. 08 and 11 are low-temperature heaters, whose heat sources are mainly shaft seal leakage, gate rod leakage and condensing turbine exhaust steam. The exhaust steam is recovered to the demineralized water tank 29 and the delivery tank 39 through the above-mentioned heat exchange and quality recovery. 09 is a condenser, 091 is a circulating water inlet, and 092 is a circulating water outlet. The existence of the condenser realizes the alternation of the condensing turbine and the back pressure turbine, and provides the possibility for realizing the water balance of the system and decoupling the supply of air and power generation.

[0056] The present example is based on a large-scale sludge disposal system for deep utilization of low-grade heat energy, aiming at deep recovery of low-grade heat energy at multiple production links of a thermal power plant. A first-stage fluoroplastic low-temperature economizer is installed at the rear part of the electrostatic precipitator and the front part of the desulfurization tower. A second-stage fluoroplastic condenser is installed at the rear part of the wet electrostatic precipitator. The desalted water first flows through the condenser arranged at the rear part of the wet electrostatic precipitator to be warmed, and then is transported to the low-temperature economizer for secondary warming. The warmed desalted water is finally transported to the deaerator through a mother pipe, and is in contact with low-grade heat energy boiler combined exhaust, fixed exhaust, condenser condensate, back pressure turbine final stage extraction steam and boiler start-stop furnace exhaust for heat exchange parameter improvement to 0.55 MPa and 160°C. Most of the steam enters the high-temperature heat exchanger for further heat exchange, and the excess steam enters the disc dryer, realizing water balance and deep recovery of low-grade heat energy. The steam entering the dryer is dried through the inter-wall type of the disc dryer, and the steam in the dryer body is further heated after the steam-water separator. The exhaust is further utilized through the regenerator in the scraper, is transported to the desalted water tank, and the heat in the flue gas is deeply recovered through the above process. Compared with the original disc-type sludge drying process, the temperature reducing and pressure reducing device is cancelled, high-quality steam is saved, the exhaust waste heat is further utilized, the loss is reduced, new steam is saved, the temperature is matched, and the energy cascade utilization is realized.

[0057] Table 1 System operation parameters

[0058] Operating parameters Values Boiler load / (t / h) 220 t / h Flue gas condenser outlet water temperature / °C 134.2 Condenser inlet flow rate(t / h) 50.7 Low-temperature economizer inlet flue gas temperature / °C 129.6 Flue gas condenser inlet flue gas temperature / °C 55.6 Flue gas condenser inlet flue gas moisture content / % 16.6 Low-temperature economizer resistance / Pa 245.6 Low temperature economizer heat surface area / m 2 ]]> 2000 Inlet desalted water temperature / °C 28.2 Low-temperature economizer outlet water temperature / °C 80.0 Absorption tower inlet flue gas temperature / °C 98.4 Flue gas condenser outlet flue gas moisture content / % 13.2 Flue gas condenser outlet flue gas temperature / °C 51.8 Flue gas condenser resistance / Pa 117.5 Condenser heat exchange area / m 2 ]] 1700 Hollow shaft diameter of disc dryer / mm 750 Disc dryer disc diameter / mm 2100 Heat transfer area per dryer / m 2 ]]> 410 3 ]]> ​ 27 Dryer working pressure MPa 0.2～0.6 Dryer disc stage number / stage 58 Dryer daily processing capacity 120 t / d Inlet sludge moisture content / % 80 Outlet sludge moisture content / % 40 Sludge drying system steam consumption(t / a) 1200

[0059] A large-scale sludge disposal system based on deep utilization of low-grade heat energy is implemented for a 220 t / h circulating fluidized bed coal-fired boiler unit of a power plant, and good economic benefits are achieved.​

Claims

1. A large-scale sludge treatment system based on deep utilization of low-grade thermal energy, characterized in that, The system includes a treatment system for drying and incinerating sludge, a low-grade heat recovery system for recovering heat from sludge incineration, a low-grade heat deep heat exchange system for deep heat exchange in the process, and a deep utilization and disposal system for deep utilization of process heat. The low-grade heat recovery system includes a flue gas low-grade heat recovery system for treating sludge incineration flue gas and a waste steam low-grade heat recovery system. The flue gas low-grade heat recovery system includes a wet electrostatic precipitator, an economizer connected to the wet electrostatic precipitator, a desulfurization tower connected to the economizer, a flue gas condenser connected to the desulfurization tower, a deaerator connected to the economizer, and a demineralized water tank. The waste steam low-grade heat energy recovery system includes a waste steam recovery device for receiving waste steam, and a surface heat exchanger and a condensate tank respectively connected to the waste steam recovery device. The surface heat exchanger is connected to a demineralized water tank. A first water supply pipeline and a second water supply pipeline are provided between the waste steam recovery device and the surface heat exchanger. The high-temperature demineralized water in the waste steam recovery device is transported to the surface heat exchanger for heat exchange on the first water supply pipeline. A third water supply pipeline for transporting low-temperature demineralized water is provided between the surface heat exchanger and the demineralized water tank. The deep utilization and disposal system includes a high-temperature heater connected to a deaerator. The deaerator is also connected to a dryer for drying sludge.

2. The large-scale sludge treatment system based on deep utilization of low-grade thermal energy according to claim 1, characterized in that, The exhaust steam originates from one or more of the following: boiler constant exhaust steam, combined exhaust steam, motor shaft seal leakage, and valve rod leakage.

3. The large-scale sludge treatment system based on deep utilization of low-grade thermal energy according to claim 1, characterized in that, A fourth water supply pipeline connects the surface heat exchanger and the deaerator. After the low-temperature demineralized water is heated by heat exchange, it is discharged through the fourth water supply pipeline.

4. The large-scale sludge treatment system based on deep utilization of low-grade thermal energy according to claim 1, characterized in that, The waste steam recovery device is connected to the condensate tank via a drainage pipeline, which includes a detection section, a direct discharge section, and a recovery section.

5. The large-scale sludge treatment system based on deep utilization of low-grade thermal energy according to claim 4, characterized in that, The detection section is connected to the waste steam recovery device. The detection section is equipped with a first control valve for on / off control, a first high-temperature water pump, and a detection device for monitoring whether the water quality meets the boiler feedwater requirements. The recovery section is connected to the third water supply pipeline. The recovery section is equipped with a second control valve for on / off control, and the direct discharge section is equipped with a third control valve for on / off control. The first control valve, the second control valve, the third control valve, and the detection device are all connected to the controller. If the detection device detects that the water quality is qualified, the second control valve opens, and the water circuit of the recovery section is opened, so that the high-temperature demineralized water in the waste steam recovery device is transported to the third water supply pipeline for mixing and use. Otherwise, the direct discharge section is opened and the water is discharged directly. The waste steam recovery device and the demineralized water tank are connected to a makeup water pipeline for replenishing low-temperature demineralized water.

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