System and method for drying dewatered sludge of power plant by utilizing waste heat of dead steam

Abstract

The invention discloses a system and a method for drying dewatered sludge of a power plant by using waste steam waste heat. The system comprises a periodic discharge flash tank, a sludge drying device, a mud cake crusher, a condensate water tank and a steam heat storage unit, the mud cake crusher is connected with the sludge drying device, the sludge drying device is connected with the condensate water tank, and the condensate water tank is connected with the steam heat storage unit; the steam heat storage unit is filled with a heat storage material; the periodic blowdown flash tank is connected with the steam heat storage unit, and the steam heat storage unit is connected with the sludge drying device; the sludge drying device comprises a shell, a sludge drying device cylinder is arranged in the shell, and a plurality of rotary drying cylinders are uniformly arranged in the sludge drying device cylinder. According to the invention, boiler regularly-discharged dead steam recovery treatment and a power plant sludge treatment technology are combined, so that on one hand, the problems of waste of power plant boiler regularly-discharged dead steam and white feather and equipment corrosion caused by dead steam discharge are solved, and discontinuous dead steam of a power plant is converted into a stable heat source for utilization; in addition, the problems of high outward transportation treatment cost and limited treatment capacity of the power plant sludge are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of power plant sludge treatment and disposal, and specifically relates to a system and method for drying dehydrated sludge from a power plant by utilizing waste steam heat. Background Art

[0002] In the production process of thermal power plants, high-temperature and high-pressure steam releases a certain amount of energy and becomes waste steam or low-parameter steam discharged from the system, or hot water with a certain pressure and temperature, as well as continuous sewage discharge, regular sewage discharge, drainage, etc. of boilers, pressure vessels and pipelines. After depressurization, part of the water will evaporate again due to the pressure reduction, forming flash steam. We call these waste steam, exhaust steam or flash steam "exhaust steam". During the operation of the unit, a large amount of steam (about 1~3t / h) is discharged into the atmosphere from the exhaust pipe of the boiler fixed-discharge expansion tank. These steams contain the latent heat of vaporization of the working fluid from liquid water to steam, and contain low-grade waste heat resources. Due to its low pressure, exhaust steam cannot meet the requirements of steam-using equipment, so power plants usually discharge it directly, which not only causes serious waste of heat and steam resources, but also brings huge economic losses to enterprises and pollutes the environment. In addition, the exhaust steam discharged from power plants is discontinuous, so how to efficiently and stably recycle and utilize the exhaust steam discharged is also one of the issues that need to be focused on.

[0003] Due to the influence of national environmental policies, the transportation and treatment of power plant sludge is limited. On the one hand, the municipal government is not willing to accept it, and the cost of transporting sludge is extremely high. The method of coupling sludge incineration power generation with coal-fired units provides a new idea for the treatment and disposal of power plant sludge, and some power plants have successfully implemented it. The sludge produced by the raw water pretreatment system and biochemical system of the power plant has a water content of about 60% after sludge dehydration. The sludge blending needs to further reduce the sludge water content. Studies have shown that the water content requirement for sludge blending is not higher than 50%, and the dehydration requirement is relatively low. Therefore, it is necessary to further study and develop an economical and simple drying device to dry the dehydrated sludge, so that coal-fired power plants can achieve the goal of saving resources and protecting the environment. Summary of the invention

[0004] In order to solve the technical problems of high cost and limited processing capacity of power plant sludge drying in the prior art, the purpose of the present invention is to provide a system and method for drying dehydrated sludge in power plants by utilizing exhaust steam waste heat, and the exhaust steam generated by the power plant boiler is used for drying power plant sludge, thereby avoiding the waste of exhaust steam from the power plant and the resulting white plume and equipment corrosion, while achieving efficient, stable, low-energy consumption and low-cost processing of power plant sludge drying, and being able to achieve a sludge moisture content of 30%, meet the requirements of co-combustion, and help coal-fired power plants save resources and protect the environment.

[0005] To achieve the above object, the present invention adopts the following technical solution: A system for drying dehydrated sludge in a power plant using waste steam waste heat, comprising a fixed discharge expansion container, a sludge drying device, a mud cake crusher, a condensate tank and a steam heat storage unit; The mud cake crusher is connected to the sludge drying device, the lower part of the sludge drying device is connected to the condensate water tank, and the condensate water tank is connected to the steam heat storage unit; the interior of the steam heat storage unit is filled with expandable graphite-Ca(OH)2 composite heat storage material; The fixed-discharge expansion tank is connected to the steam heat storage unit, and the steam heat storage unit is connected to the sludge drying device; The sludge drying device comprises a sludge drying device cylinder body, a plurality of rotary drying cylinders are evenly arranged in the sludge drying device cylinder body, and a circumferential steam distribution device is arranged at the bottom of the sludge drying device cylinder body.

[0006] Furthermore, a gas outlet is provided at the upper portion of the shell, a steam inlet is provided at the lower portion of the shell, and the gas outlet is connected to the steam heat storage unit; The circumferential steam distribution device comprises a steam distribution branch pipe, which is an annular steam distribution pipe or a straight steam distribution pipe. A plurality of steam distribution holes are opened on the steam distribution branch pipe, and the diameter of the steam distribution holes is 80% of the diameter of the steam distribution branch pipe.

[0007] Furthermore, a steam circulation pipe is provided between the gas outlet and the steam heat storage unit, and a steam circulation check valve is provided on the steam circulation pipe.

[0008] Furthermore, a secondary steam recovery pipe and a safety valve are provided on the fixed-discharge expansion vessel, and a steam recovery valve and a steam delivery check valve are provided on the secondary steam recovery pipe.

[0009] Furthermore, the steam heat storage unit includes a steam inlet, a steam outlet, a cold water inlet and a condensed water outlet. The fixed-discharge expansion tank is connected to the steam inlet, the condensed water tank is connected to the cold water inlet through a condensed water delivery pipe, the steam outlet is connected to the sludge drying device through a steam delivery pipe, and the condensed water outlet is connected to the condensed water tank through a pipeline.

[0010] Furthermore, a feed hopper is provided on the top of the rotary drying drum; A rotating scraper is provided inside the rotary drying drum; The bottom of the rotary drying drum is connected to the head section of the sludge drying device; The sludge drying device also includes a sludge drying device head section connected to the sludge drying device cylinder, and an isolation plate is provided between the sludge drying device cylinder and the sludge drying device head section; An electric fan-shaped gate valve for controlling the discharge of dried sludge is arranged at the bottom of the head section of the sludge drying device.

[0011] Furthermore, a bracket is welded on the cylinder of the sludge drying device.

[0012] Furthermore, the mud cake crusher adopts a double-roller structure, the mud cake crusher inlet is connected to a screw conveyor, and the mud cake crusher outlet is connected to the sludge drying device through a sludge distributor; The mud cake crusher comprises a round roller, a scraper and a rotating mud scraper. The round roller is provided with a scraper and a rotating mud scraper.

[0013] Furthermore, the sludge distributor is provided with a corrugated feed hole plate, a push-type scraper and a discharge hole plate in the middle in sequence from top to bottom.

[0014] Furthermore, the peak spacing of the corrugations on the corrugated feed hole plate is 5 to 10 cm, and the rotation speed of the push-type scraper is 50 to 120 rpm.

[0015] A method for drying dewatered sludge in a power plant using waste steam heat comprises the following steps: The dewatered sludge from the power plant passes through the mud cake crusher and enters the rotary drying drum inside the sludge drying device. The rotating scraper inside the rotary drying drum stirs and breaks the sludge. The exhaust steam from the boiler passes through the exhaust expansion tank and enters the steam heat storage unit, where the latent heat of the steam is converted into chemical energy for storage. The expandable graphite-Ca(OH)2 composite heat storage material inside the steam heat storage unit undergoes an endothermic reaction to generate calcium oxide and water, completing the exhaust steam heat storage process. The condensed water in the condensed water tank enters the steam heat storage unit and reacts with the expandable graphite-Ca(OH)2 composite heat storage material to release a large amount of heat. The heat enters the sludge drying device in the form of high-temperature steam to achieve sludge drying.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention combines boiler exhaust steam recovery and treatment with power plant sludge treatment and disposal technology by setting a fixed-discharge expansion tank and a sludge drying device, and proposes a technical route for using fixed-discharge exhaust steam for power plant sludge drying. On the one hand, it solves the waste of boiler exhaust steam in power plants and the white plume and equipment corrosion caused by exhaust steam discharge, and on the other hand, it solves the problem of high cost of sludge transportation and limited processing capacity in power plants. In the present invention, the steam heat storage unit is filled with expandable graphite-Ca(OH)2 composite heat storage material, which can absorb the calorific value of steam and store it in the form of chemical energy. When the heat source is needed, it releases heat by absorbing water and releasing heat, and finally realizes the collection, storage and output of unstable fixed-discharge exhaust steam as a stable heat source, solving the problem of difficulty in utilization caused by the discontinuity of fixed-discharge exhaust steam. In the present invention, a plurality of rotary drying drums are arranged in the sludge drying device. Compared with the conventional rotary sludge drying device, the heat exchange area per unit volume of sludge is larger and the mass transfer rate is higher. The present invention can achieve a sludge moisture content of 30%, meeting the requirements of blending.

[0017] Furthermore, the sludge distributor in the present invention adopts a corrugated feed orifice plate-propelling scraper-discharge orifice plate structure, which can achieve uniform distribution of sludge feed.

[0018] Furthermore, the internal feeding mode of the drying drum is a rotary scraper, which can prevent the sludge from clumping in the drum, increase the residence time of the sludge in the drum, and achieve a better sludge drying effect. The device is suitable for systems with small sludge volumes in power plants, with low energy consumption and simple system operation and maintenance. The moisture content of the dried sludge is less than 50%, which can be used for sludge blending in coal-fired power plants.

[0019] Furthermore, by providing a steam circulation check valve, it is possible to prevent discontinuously discharged exhaust steam from directly entering the cylinder of the sludge drying device to form a downstream flow, thereby reducing the sludge drying efficiency.

[0020] Furthermore, the circumferential steam distribution device is arranged at the lower part of the sludge drying device, and the steam forms a countercurrent from bottom to top in the sludge drying device and from top to bottom in the rotary drying drum, which can completely dry the sludge that initially enters and ensure the drying effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The process flow chart of the method for drying dehydrated sludge in a power plant by utilizing waste steam heat of the present invention; Figure 2 This is a schematic diagram of the structure of the sludge drying device; Figure 3 Schematic diagram of a circumferential steam distribution device; wherein (a) is the number of rotary drying drums n=4, (b) is the number of rotary drying drums n=7; Figure 4 Schematic diagram of the sludge distributor structure; among them, (a) is a schematic diagram of the sludge distributor, (b) is a schematic diagram of the corrugated feed orifice plate, (c) is a schematic diagram of the propulsion scraper, and (d) is a schematic diagram of the discharge orifice plate.

[0022] In the figure: 1- fixed-discharge expansion vessel, 11- steam recovery valve; 12- exhaust steam delivery pipe; 13- -Secondary steam discharge pipe; 14-safety valve; 2-sludge drying device; 21-feeding hopper; 22-sludge drying device cylinder; 23-rotary drying cylinder; 231-rotating scraper; 24-circumferential steam distribution device; 241-steam distribution branch pipe; 242-steam distribution hole; 243-bracket; 25-electric fan-shaped gate valve; 26-steam circulation pipe; 27-steam circulation check valve; 28-sludge drying device head section; 3-screw conveyor; 4-mud cake crusher; 41-round roller; 42-scraper; 43-rotating scraper; 5-sludge distributor; 51-corrugated feed orifice plate; 52-propelling scraper; 53-discharging orifice plate; 6-condensate tank; 61-condensate automatic valve; 62-condensate delivery pipe; 7-steam heat storage unit; 71-steam delivery automatic valve; 72-steam delivery pipe. DETAILED DESCRIPTION

[0023] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0025] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0026] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0028] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] The present invention recovers boiler exhaust steam for power plant sludge drying, which can reduce the sludge moisture content while achieving exhaust steam recovery, thereby achieving the sludge co-combustion requirement, and is a technology that complies with the concept of green and sustainable development.

[0030] See also Figure 1 The present invention discloses a system for drying dehydrated sludge in a power plant by utilizing waste heat from exhaust steam, which mainly comprises a fixed-discharge expansion container 1, a sludge drying device 2, a screw conveyor 3, a mud cake crusher 4, a sludge distributor 5, a condensed water tank 6 and a steam heat storage unit 7.

[0031] The fixed-discharge expansion vessel 1 is provided with a secondary steam recovery pipe 12 and a safety valve 14. The secondary steam recovery pipe 12 is provided with a steam recovery valve 11 and a steam delivery check valve 13.

[0032] The steam heat storage unit 7 includes a steam inlet, a steam outlet, a cold water inlet and a condensed water outlet, the exhaust steam delivery pipe 12 is connected to the steam inlet, the condensed water tank 6 is connected to the cold water inlet through the condensed water delivery pipe 62, the steam outlet is connected to the sludge drying device 2 through the steam delivery pipe 72, and the condensed water outlet is connected to the condensed water tank 6 through a pipeline. The interior of the steam heat storage unit 7 is filled with expandable graphite-Ca(OH)2 composite heat storage material.

[0033] The sludge drying device 2 includes a feed hopper 21, a sludge drying device cylinder 22, a rotary drying cylinder 23, a circumferential steam distribution device 24, an electric fan-shaped gate valve 25, a steam circulation pipe 26 and a sludge drying device head section 28. An isolation plate is arranged between the sludge drying device cylinder 22 and the sludge drying device head section 28, and steam will not enter the sludge drying device head section 28 from the sludge drying device cylinder 22. Among them, a feed hopper 21 is arranged on the top of the sludge drying device cylinder 22, and a plurality of rotary drying cylinders 23 are evenly arranged in the sludge drying device cylinder 22. The feed hopper 21 is located at the top of the rotary drying cylinder 23, and a circumferential steam distribution device 24 is arranged at the bottom of the sludge drying device cylinder 22. A gas outlet is arranged on the upper part, and a steam inlet is arranged on the lower part. The remaining steam after heat exchange with the sludge in the rotary drying cylinder 23 is connected to the steam inlet of the steam heat storage unit through the gas outlet, the steam circulation pipe 26, the secondary steam recovery pipe 12, and the steam circulation check valve 27 is arranged on the steam circulation pipe 26. The steam circulation check valve 27 can prevent the discontinuously discharged exhaust steam from directly entering the sludge drying device cylinder 22 of the sludge drying device 2 to form a downstream flow, thereby reducing the sludge drying efficiency.

[0034] An electric fan-shaped gate valve 25 is provided at the bottom of the head section 28 of the sludge drying device to control the discharge of the dried sludge.

[0035] The screw conveyor 3 is connected to the inlet of the mud cake crusher 4, the outlet of the mud cake crusher 4 is connected to the inlet of the sludge distributor 5, the outlet of the sludge distributor 5 is connected to the feed hopper 21 of the sludge drying device 2, and the dried sludge discharged from the outlet of the bottom electric fan-shaped gate valve 25 of the sludge drying device 2 can be directly transported to the sludge blending unit. The lower part of the sludge drying device 2 is also connected to the condensed water tank 6.

[0036] See also Figure 2 The rotary drying drum 23 is provided with a rotating scraper 231 inside, and the rotating scraper 231 is used to rotate and drive the sludge downward. By adjusting the rotation speed of the rotating scraper 231, the sludge drying time can be adjusted to ensure that the moisture content of the sludge after drying meets the requirements. The rotation speed of the rotating scraper 231 is generally 30 to 100 rpm.

[0037] See also Figure 3 In (a) and (b), the circumferential steam distribution device 24 has a different structure according to the number of rotary drying drums 23. The circumferential steam distribution device 24 includes a steam distribution branch pipe 241. The steam distribution branch pipe 241 is specifically a circular steam distribution pipe and a straight steam distribution pipe. A plurality of steam distribution holes 242 are provided on the steam distribution branch pipe 241. The diameter of the steam distribution hole 242 is 80% of the diameter of the steam distribution branch pipe 241.

[0038] A bracket 243 is also welded on the cylinder 22 of the sludge drying device to support the circumferential steam distribution device 24 .

[0039] The circumferential steam distribution device 24 is arranged at the lower part of the sludge drying device 2. The steam in the sludge drying device 2 forms a countercurrent from bottom to top with the sludge from top to bottom in the rotary drying drum 23, which can completely dry the sludge that begins to enter and ensure the drying effect.

[0040] See also Figure 1 The mud cake crusher 4 adopts a double-roller structure. The mud cake crusher 4 includes a round roller 41, a scraper 42 and a rotating scraper 43. The scraper 42 and the rotating scraper 43 are arranged on the round roller 41. The round roller 41 can remove the sludge attached to its surface through the scraper 42 during the sludge crushing process, and the rotating scraper 43 can send the sludge out of the mud cake crusher 4.

[0041] See also Figure 4 The sludge distributor 5 includes three parts: upper, middle and lower parts. The upper part is a corrugated feed orifice plate 51, the middle part is a push-type scraper 52, and the bottom part is a discharge orifice plate 53. The peak spacing of the corrugations on the corrugated feed orifice plate 51 is 5-10 cm. The rotation speed of the push-type scraper 52 is 50-120 rpm. The opening position and number of the bottom discharge orifice plate 53 are consistent with the rotary drying drum 23 in the sludge drying device 2, and the bottom of the discharge orifice plate 53 is connected to the feed hopper 21 at the top of the sludge drying device 2 through a pipeline to ensure that the sludge directly enters the rotary drying drum 23 without contacting the steam.

[0042] A method for drying dehydrated sludge in a power plant using exhaust steam waste heat based on the above system is as follows: the dehydrated sludge in the power plant (the moisture content is generally about 60%) is transported to the mud cake crusher 4 via the screw conveyor 3, and the mud cake crusher 4 can crush the large mud cake into smaller blocks or particles, and then pass through the sludge distributor 5, firstly, the block or granular sludge is evenly distributed and fed through the corrugated feed orifice plate 51, and then the sludge is pushed to the discharge orifice plate 53 by the push-type scraper 52 in the middle section of the sludge distributor 51, and enters the rotary drying cylinder 23 inside the sludge drying device 2 through the pipeline at the bottom of the discharge orifice plate 53. The rotating scraper 231 inside the rotary drying cylinder 23 can stir and break the sludge to prevent the sludge from agglomerating. The exhaust steam of the boiler enters the steam heat storage unit 7 through the secondary steam recovery pipe 12 of the exhaust expansion tank 1, and the latent heat of the steam is converted into chemical energy for storage. At this time, the expandable graphite-Ca(OH)2 composite heat storage material inside the steam heat storage unit 7 undergoes an endothermic reaction to generate calcium oxide and water, and the condensed water is transported to the condensate tank 6 through a pipeline. After the exhaust steam heat storage process is completed, the sludge can be released and dried. At this time, the condensed water in the condensate tank 6 enters the steam heat storage unit 7 through the condensate delivery pipe 62, and reacts with the expandable graphite-Ca(OH)2 composite heat storage material. The calcium oxide reacts with water to release a large amount of heat, and the heat enters the sludge drying device 2 in the form of high-temperature steam through the steam delivery pipe 72. The steam is evenly distributed around the rotary drying drum 23 through the circumferential steam distribution device 24 at the bottom of the sludge drying device 2. The sludge in the rotary drying drum 23 is indirectly heat exchanged with the steam in the shell of the sludge drying device 2 through the drum wall to achieve sludge drying. During the heat exchange process, the steam condensate is discharged to the condensate tank 6 through the pipeline, and the remaining steam is recovered to the steam heat storage unit 7 through the steam circulation pipe 26. The dried sludge enters the head section 28 of the sludge drying device, and is finally discharged through the electric fan-shaped gate valve 25 at the bottom and enters the subsequent co-combustion unit.

[0043] Furthermore, the steam temperature can be controlled by controlling the amount of cold water entering the steam heat storage unit 7, thereby achieving control over the sludge drying process, and the final moisture content of the dried sludge can be adjusted to a range of 20% to 50% according to the requirements of the blending.

[0044] Example 1 The exhaust steam of a coal-fired power plant is transported to the sludge drying unit through a pipeline, and the heat loss is relatively small. The steam temperature is about 100°C measured on the steam inlet pipeline of the sludge drying unit 2. The exhaust steam temperature of the power plant is 110°C, the pressure is about 0.12 kg (0.012 MPa), and the exhaust time is about 1 hour per day.

[0045] The exhaust steam discharged by the unit passes through the fixed-discharge expansion tank 1 and enters the steam heat storage unit 7. The expandable graphite-Ca(OH)2 composite heat storage material inside the steam heat storage unit 7 can absorb the heat of the instantaneously discharged exhaust steam and store it as chemical energy. This process is a heat storage process. After the heat storage process is completed, energy and heat can be released to provide a stable heat source for the sludge drying process. During the energy release and heat release process, the cold water in the condensation water tank 6 is transported to the steam heat storage unit 7 through a pipeline. Calcium oxide reacts with water to release a large amount of heat, and the heat is transported to the sludge drying device 2 in the form of steam to complete heat exchange with the sludge.

[0046] The daily sludge discharge of the raw water pretreatment system is 2t / d (calculated based on the amount of absolutely dry sludge). The moisture content of dewatered sludge is generally around 60%, so the dewatered sludge treatment capacity is 0.32m 3 / h, with a daily processing capacity of approximately 8 m 3 .

[0047] The sludge from the raw water pretreatment system is squeezed and drained by the plate and frame dewatering machine to form a mud cake. The mud cake is sent to the mud cake crusher 4 through the screw conveyor 3. The mud cake is squeezed and crushed into smaller blocks or granular sludge by two round rollers 41. At this time, the average particle size of the sludge is about 3 cm. The crushed sludge is output by the rotating scraper 43 at the outlet of the mud cake crusher 4 and enters the upper corrugated feed orifice plate 51 of the sludge distributor 5. The corrugated plate gap on the corrugated feed orifice plate 51 is 5 cm, which can ensure the passage of sludge. At the same time, when there is a lot of sludge entering the upper part of the sludge distributor 5, the corrugated feed orifice plate 51 can achieve uniform distribution of sludge, and then the sludge is pushed to the discharge orifice plate 53 through the middle push-type scraper 52. The speed of the push-type scraper 52 is set to 60 rpm.

[0048] The sludge enters the feed hopper 21 of the sludge drying device 2 through a pipeline connected to the opening of the discharge orifice plate 53, and then the rotating scraper 231 inside the rotary drying drum 23 drives the sludge material into the rotary drying drum 23. The sludge exchanges heat with the steam entering the cylinder 22 of the sludge drying device, thereby evaporating and removing the free water in the sludge.

[0049] For this system, there are 5 rotary drying drums 23, each with a diameter of 0.4m and a height of 2m. The rotation speed of the rotary scraper 231 is set to 80 rpm, and the residence time of the sludge drying device is set to 30min. When the moisture content of the sludge is reduced to less than 50% after drying, the electric fan-shaped gate valve 25 at the bottom of the drying device is opened to discharge the dried sludge from the sludge drying device 2 and transport it to the incineration unit for mixed combustion.

[0050] After the steam inside the cylinder 22 of the sludge drying device performs indirect heat exchange with the sludge, condensate is formed, and the condensate is discharged to the condensate water tank 6 through the condensate discharge pipe at the bottom of the sludge drying device 2 .

[0051] This embodiment uses a sludge drying system to dry the dehydrated sludge from the raw water pretreatment of the power plant using the exhaust steam from the power plant, and finally achieves a sludge moisture content of 30%, meeting the requirements for co-combustion. This technology is of great significance for recycling the exhaust steam from the power plant and realizing the resource treatment of sludge from the power plant.

[0052] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0053] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A system for drying dehydrated sludge in a power plant using waste steam heat, characterized in that: It comprises a fixed-discharge expansion container (1), a sludge drying device (2), a sludge cake crusher (4), a condensate tank (6) and a steam heat storage unit (7); The mud cake crusher (4) is connected to the sludge drying device (2), the lower part of the sludge drying device (2) is connected to the condensate tank (6), and the condensate tank (6) is connected to the steam heat storage unit (7); the interior of the steam heat storage unit (7) is filled with expandable graphite-Ca(OH)2 composite heat storage material; The fixed-discharge expansion container (1) is connected to the steam heat storage unit (7), and the steam heat storage unit (7) is connected to the sludge drying device (2); The sludge drying device (2) comprises a sludge drying device cylinder (22) and a sludge drying device head section (28), a plurality of rotary drying cylinders (23) are evenly arranged in the sludge drying device cylinder (22), and a circumferential steam distribution device (24) is arranged at the bottom of the sludge drying device cylinder (22).

2. The system for drying dehydrated sludge from a power plant using waste steam heat according to claim 1 is characterized in that: A gas outlet is provided at the upper portion of the shell, a steam inlet is provided at the lower portion of the shell, and the gas outlet is connected to the steam heat storage unit (7); The circumferential steam distribution device (24) comprises a steam distribution branch pipe (241), which is an annular steam distribution pipe or a straight steam distribution pipe. The steam distribution branch pipe (241) is provided with a plurality of steam distribution holes (242), and the diameter of the steam distribution holes (242) is 80% of the diameter of the steam distribution branch pipe (241).

3. The system for drying dehydrated sludge from a power plant using waste steam heat according to claim 1 is characterized in that: A steam circulation pipe (26) is provided between the gas outlet and the steam heat storage unit (7), and a steam circulation check valve (27) is provided on the steam circulation pipe (26).

4. The system for drying dehydrated sludge from a power plant using waste steam heat according to claim 1 is characterized in that: A secondary steam recovery pipe (12) and a safety valve (14) are provided on the fixed-discharge expansion vessel (1), and a steam recovery valve (11) and a steam delivery check valve (13) are provided on the secondary steam recovery pipe (12).

5. The system for drying dehydrated sludge from a power plant using waste steam heat according to claim 1 is characterized in that: The steam heat storage unit (7) comprises a steam inlet, a steam outlet, a cold water inlet and a condensed water outlet; the fixed-discharge expansion tank (1) is connected to the steam inlet; the condensed water tank (6) is connected to the cold water inlet via a condensed water delivery pipe (62); the steam outlet is connected to the sludge drying device (2) via a steam delivery pipe (72); and the condensed water outlet is connected to the condensed water tank (6) via a pipeline.

6. The system for drying dehydrated sludge from a power plant using waste steam heat according to claim 1 is characterized in that: A feed hopper (21) is provided on the top of the rotary drying drum (23); A rotating scraper (231) is arranged inside the rotary drying drum (23); The bottom of the rotary drying drum (23) is connected to the end section (28) of the sludge drying device; The sludge drying device (2) further comprises a sludge drying device head section (28) connected to the sludge drying device cylinder (22), and an isolation plate is provided between the sludge drying device cylinder (22) and the sludge drying device head section (28); An electric fan-shaped gate valve (25) for controlling the discharge of dried sludge is arranged at the bottom of the head section (28) of the sludge drying device.

7. The system for drying dehydrated sludge from a power plant using waste steam heat according to claim 1, characterized in that: The mud cake crusher (4) adopts a double-roller structure, the inlet of the mud cake crusher (4) is connected to a screw conveyor (3), and the outlet of the mud cake crusher (4) is connected to the sludge drying device (2) via a sludge distributor (5); The mud cake crusher (4) comprises a round roller (41), a scraper (42) and a rotating mud scraper (43), wherein the round roller (41) is provided with the scraper (42) and the rotating mud scraper (43).

8. The system for drying dehydrated sludge from a power plant using waste steam heat according to claim 1, characterized in that: The sludge distributor (5) comprises a corrugated feed orifice plate (51) arranged in sequence from top to bottom, a push-type scraper (52) in the middle, and a discharge orifice plate (53).

9. The system for drying dehydrated sludge from a power plant using waste steam heat according to claim 8, characterized in that: The peak spacing of the corrugations on the corrugated feed hole plate (51) is 5 to 10 cm, and the rotation speed of the push-type scraper (52) is 50 to 120 rpm.

10. A method for drying dehydrated sludge in a power plant by utilizing waste steam and waste heat based on the system of claim 6, characterized in that: The following steps are involved: The dewatered sludge of the power plant passes through the sludge cake crusher (4) and enters the rotary drying drum (23) inside the sludge drying device (2). The rotating scraper (231) inside the rotary drying drum (23) stirs and breaks the sludge. The exhaust steam of the boiler passes through the exhaust expansion tank (1) and enters the steam heat storage unit (7), where the latent heat of the steam is converted into chemical energy for storage. The expandable graphite-Ca(OH)2 composite heat storage material inside the steam heat storage unit (7) undergoes an endothermic reaction to generate calcium oxide and water, thereby completing the exhaust steam heat storage process. The condensed water in the condensed water tank (6) enters the steam heat storage unit (7), reacts with the expandable graphite-Ca(OH)2 composite heat storage material, and releases a large amount of heat. The heat enters the sludge drying device (2) in the form of high-temperature steam, thereby achieving sludge drying.

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