Sludge drying system and method for recycling conversion waste heat

Abstract

The invention relates to the technical field of sludge treatment, and particularly discloses a conversion waste heat recycling sludge drying system, which comprises a heat exchange unit, a sludge drying unit and a condensation unit, the sludge drying unit comprises a treatment box, and a plurality of material conveying mesh belts which are arranged at intervals up and down are mounted in the treatment box; one side of the upper end of the treatment box is provided with a sludge feeding device, and one side of the lower end is provided with a discharge port; the heat exchange unit is connected with a high-temperature medium generated in the conversion reaction stage, the bottom of the treatment box is communicated with a hot air conveying pipe connected with the heat exchange unit, the top of the treatment box is connected with an air return pipe, the end of the air return pipe is connected with the condensation unit, and the condensation unit is connected with the heat exchange unit; according to the system, the effective combination of low-temperature waste heat and sludge drying treatment in the conversion reaction stage is realized, the system has the advantages of energy conservation and environmental protection in the sludge treatment process, and meanwhile, the sludge drying unit can continuously convey the sludge, so that the efficient treatment of continuous drying of the sludge is realized.

Description

Technical Field

[0001] The invention relates to the technical field of sludge treatment, and specifically discloses a sludge drying system and method for converting waste heat for recycling. Background Art

[0002] At present, various coal gasification processes are used in factories that use coal as raw materials to produce chemical products at home and abroad. The typical HT-L aerospace furnace pulverized coal gasification process is a process that uses dry coal powder as raw material and adopts a chilling process to produce crude synthesis gas. The synthesis gas has the characteristics of high water-gas ratio and high pressure. In order to meet the requirements of synthesis gas, a conversion section needs to be set up. Under the action of a catalyst, CO in the raw gas reacts with H2O to generate corresponding amounts of CO2 and H2. The conversion reaction is a highly exothermic reaction, and heat recovery is an important link. How to recover the low-temperature waste heat of the conversion and reduce the temperature of the conversion gas has always been a relatively difficult topic to overcome in the conversion process.

[0003] At the same time, coal chemical enterprises at home and abroad will produce a large amount of sludge. The treatment of these sludges usually adopts drying treatment to reduce its moisture content to about 10%~40%. At present, the domestic sludge drying devices mainly include paddle drying, two-stage drying and low-temperature waste heat drying. The paddle drying technology uses 0.6~0.8MPa steam to heat saturated water vapor as a heat carrier, which enters the jacket of the dryer shell and the inner cavity of the paddle shaft. The heat carrier temperature is 130~180℃, and the discharge temperature is high, about 100℃. The sludge moisture content is about 60%, and there is a "sticky phase" stage. The moisture content can only be adjusted by adjusting the speed. It is not easy to control the original form. The particle size is uneven and blocky. The mechanical friction is large, resulting in a high dust content, causing secondary air pollution. The two-stage drying technology uses a high-pressure belt filter press to dehydrate the wet mud to a moisture content of 65% in the first stage, and then undergoes a second-stage chemical treatment to reduce the final water content to 10%~40%. However, the first-stage dehydration requires the addition of a large amount of powdered sludge modifier, and the on-site dust is difficult to control. The amount of sludge to be treated in the later stage is greatly increased. At the same time, it is difficult to form, which is not conducive to the second-stage treatment. In addition, the pH of the effluent from the filter press is high, and it needs to be returned to the comprehensive pool for dilution and post-treatment, and the start-up and shutdown operations are complicated. The low-temperature waste heat dryer adopts a low-temperature fully enclosed chemical mode. The operation site is clean, odorless, and no odor overflows. There is no need to install complex deodorization and other environmental protection devices. After drying, the sludge has a low moisture content and almost no dust is generated. The sludge temperature is low (<50°C) and does not need to be cooled, so it can be stored directly. However, the existing low-temperature waste heat dryer requires an additional heat source fan, and its heat recovery effect is not good, resulting in a large loss of electricity. Therefore, in view of the above-mentioned deficiencies of the existing sludge drying technology, the present application proposes a system and a sludge drying method for drying sludge by utilizing conversion waste heat and realizing effective recovery of the conversion waste heat. Summary of the invention

[0004] The purpose of the present invention is to provide a sludge drying system and method for recycling conversion waste heat, so as to effectively utilize the low-temperature waste heat in the conversion stage of coal chemical enterprises, and dry the sludge generated by the coal chemical enterprises, so as to achieve energy saving, environmental protection and sludge management effects.

[0005] The present invention is achieved through the following technical solutions: A sludge drying system for waste heat conversion and recycling, comprising a heat exchange unit, a sludge forming unit, a sludge drying unit and a condensing unit, wherein the sludge drying unit comprises a processing box, wherein a plurality of conveying mesh belts arranged at intervals from top to bottom are installed in the processing box, the sludge forming unit is arranged on one side of the upper end of the processing box, and a discharge port is arranged on one side of the lower end of the processing box; The waste heat medium inlet end of the heat exchange unit is connected to the high-temperature medium generated in the conversion reaction stage, the bottom of the treatment box is connected to a hot air delivery pipe connected to the dry hot air exhaust end of the heat exchange unit, the top of the treatment box is connected to a return air pipe, the end of the return air pipe is connected to the condensation unit, and the liquefied dehumidified gas exhaust end of the condensation unit is connected to the heat exchange unit.

[0006] As a further configuration of the above scheme, a constant temperature controlled heat exchanger is arranged in the middle of the hot air conveying pipe, and the constant temperature controlled heat exchanger is connected to the high temperature medium generated in the shift reaction stage.

[0007] As a further configuration of the above scheme, the material conveying mesh belts in the processing box are provided with three mesh belts, namely, upper, middle and lower, and the upper and lower adjacent mesh belts are staggered in head and tail configuration.

[0008] As a further arrangement of the above scheme, a plurality of moist hot air exhaust hoods are arranged at intervals on the upper end of the processing box, the upper ends of the plurality of moist hot air exhaust hoods are connected to the return air pipe, and a plurality of hot air inlets are arranged on the bottom of the processing box, and the hot air inlets are connected to the hot air delivery pipe.

[0009] As a further configuration of the above solution, the sludge drying unit includes a hopper and a strip cutting mechanism, and the strip cutting mechanism is arranged at the bottom of the hopper.

[0010] The present invention also discloses a sludge drying method using the above sludge drying system, which comprises the following steps: 1) After the desalted water and the shift gas are exchanged for heat, a portion of the desalted water is passed into the deaerator tank, and the other portion is passed into the heat exchange unit, so that the heat exchange unit generates dry hot air, and then the dry hot air is passed into the bottom of the treatment box in the sludge forming unit; 2) After flocculation, the sludge is put into the butterfly screw machine for dehydration. After dehydration, it is sent to the sludge forming unit for cutting into strips, and then discharged onto the conveyor mesh belt, so that the cut sludge is evenly laid on the conveyor mesh belt and transported by the conveyor mesh belt; 3) The dry hot air introduced into the treatment box contacts the sludge on the conveyor belt during its upward flow and takes away the moisture in the sludge to dry it. At the same time, the hot and humid gas generated is introduced into the condensation unit for liquefaction and dehumidification. The dehumidified dry cold air then enters the heat exchange unit for heat exchange with high-temperature desalted water to realize circulation.

[0011] As a further configuration of the above scheme, the temperature of the hot dry air introduced into the processing box in step 1 is controlled between 70-80°C.

[0012] As a further configuration of the above scheme, in step three, variable frequency stepless speed regulation is used to control the conveying speed of the conveyor belt to control the moisture content of the dried sludge between 10-40%.

[0013] During the operation of the sludge drying system for conversion waste heat recovery disclosed in the present invention, after the high-temperature desalted water generated in the conversion reaction stage is heat exchanged with the conversion gas through the desalted water heat exchanger, a part of it enters the deaeration tank, and the other part enters the heat exchange unit, thereby exchanging heat with the dry cold air flowing through the heat exchange unit to raise its temperature to 70-80°C. The dry hot air after absorbing heat then enters the bottom of the treatment box through the hot air conveying pipe, and then moves upward from the bottom of the treatment box. In the process of the dry hot air flowing from bottom to top, the sludge on multiple feeding mesh belts will be dried in turn, and then the generated humid hot air will enter the condensing unit through the return air pipe for liquefaction and dehumidification. The dehumidified dry air will enter the heat exchange unit again to absorb heat and heat up, and will be sent to the treatment box as dry hot air again to dry the sludge. Beneficial Effects

[0014] The sludge drying system and method for recovering conversion waste heat disclosed in this patent realize the effective combination of low-temperature waste heat in the conversion reaction stage and sludge drying treatment, and has the advantages of energy saving and environmental protection in the process of sludge treatment.

[0015] The sludge drying unit in this patent can continuously transport the sludge, and dry it through the continuous introduction of circulating dry hot air flow during the sludge transportation process, thereby achieving efficient treatment of continuous drying of the sludge.

[0016] The sludge drying process in this patent adopts a closed operation in the treatment box. The operation site is clean and there is no odor overflow. There is no need to install complex deodorization and other supporting environmental protection devices. In addition, low-temperature dehumidification is adopted. The evaporating hot air does not carry any dust particles. Almost no dust is generated on site. The condensed water contains almost no solid impurities and can be directly recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0018] Figure 1 It is a schematic diagram of the connection structure of various components in the present invention. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Figure 1 , and describes the application in detail with reference to embodiments. Example 1

[0021] Embodiment 1 discloses a sludge drying system for recycling conversion waste heat, comprising a heat exchange unit 1, a sludge forming unit 2, a sludge drying unit 3 and a condensing unit 4. The waste heat medium inlet end of the heat exchange unit 1 is connected to the high-temperature medium generated in the conversion reaction stage (high-temperature desalted water after heat exchange with conversion gas through a conversion desalted water heat exchanger), so that the conversion waste heat can be absorbed by the dry cold air flowing through the heat exchange unit 1, thereby generating dry hot air at 70-80°C.

[0022] The sludge drying unit 3 includes a processing box 301, in which the upper, middle and lower three-layer conveyor mesh belts 302 are arranged, and the upper and lower adjacent conveyor mesh belts 302 are staggered at a certain distance, so that the sludge to be dried can be transported by the upper, middle and lower three-layer conveyor mesh belts 302 in sequence. A sludge forming unit 2 is arranged on one side of the upper end of the processing box 301. The sludge forming unit 2 is composed of a hopper + a strip cutting mechanism, and the strip cutting mechanism is arranged at the bottom of the hopper. After the sludge is mixed with a cationic flocculant, it is dehydrated by a butterfly screw machine, and after dehydration, it is cut by the strip cutting mechanism and then put into one end of the upper conveyor mesh belt 302, so that the cut sludge can be evenly spread on its upper surface. A discharge port 303 is provided on one side of the lower end of the processing box 301 , and the discharge port 303 is provided on the opposite side of the sludge feeding device 2 , so that the dried sludge discharged from the lower conveying mesh belt 302 can be discharged from the processing box 301 through the discharge port 303 .

[0023] A plurality of hot and humid air exhaust hoods 304 are arranged at intervals at the upper end of the treatment box 301, and then the upper ends of the plurality of hot and humid air exhaust hoods 304 are converged through branches and connected to the same return air pipe 5, and then the end of the return air pipe 5 is connected to the condensation unit 4, so that the hot and humid gas generated after the sludge is dried can enter the condensation unit 4 for liquefaction and dehumidification, and the liquefied condensate is discharged to the factory sewage pipe, and finally the liquefied and dehumidified gas is used as dry cold air and connected to the heat exchange unit 1 through a pipeline, so that the liquefied and dehumidified gas can be used as dry cold air again to absorb and utilize the conversion waste heat, reduce gas discharge, and avoid the leakage of odor in the gas.

[0024] A plurality of hot air inlets 305 are provided at the bottom of the treatment box 301. In the specific design, the hot air inlets 305 can be designed in a row, and then the plurality of hot inlets 305 are connected to a hot air conveying pipe 6 through a branch pipe, and then the end of the hot air conveying pipe 6 is connected to the heat exchange unit 1, so that the dry hot air that fully absorbs the conversion waste heat can enter from the bottom of the treatment box 301, and then in the process of its upward flow, the sludge on the upper, middle and lower three layers of conveying mesh belts 302 is dried in turn, so as to fully ensure the drying effect of the sludge.

[0025] In addition, in order to ensure that the temperature of the hot air entering the treatment box 301 can always be maintained at not less than 70°C, a constant temperature control heat exchanger 7 is also arranged in the middle of the hot air conveying pipe 6. The constant temperature control heat exchanger 7 has a built-in temperature detector and is directly connected to the high-temperature desalted water of the desalted water station in the shift reaction stage. When it is detected that the temperature of the dry hot air after heat exchange by the heat exchange unit 1 does not meet the standard, the high-temperature desalted water is directly introduced into the constant temperature control heat exchanger 7, so that the dry hot air absorbs the heat of the high-temperature desalted water again, so that its temperature can reach above 70°C, thereby ensuring the subsequent drying treatment effect of the dry hot air on the sludge. Example 2

[0026] Example 2 discloses a sludge drying method based on the sludge drying system for recycling waste heat from conversion in Example 1. The specific sludge drying method is as follows: Step 1: Pass the high-temperature shift gas into the desalted water heat exchanger to raise the temperature of the desalted water to about 90°C. A portion of the high-temperature desalted water is passed into the deaerator, and the other portion enters the heat exchange unit 1 in the system, thereby raising the temperature of the dry cold gas passed into the heat exchange unit 1 to 70-80°C to form dry hot air; Step 2: After the sludge is mixed with cationic flocculants, it enters the butterfly screw machine for dehydration, and after dehydration, it is sent to the sludge forming unit 2 to be cut into strips, and then falls into the upper conveying mesh belt 302 in the sludge drying unit 3, so that the cut sludge is evenly laid on the conveying mesh belt 302 and transported by the conveying mesh belt 302; Step 3: The dry hot air after heat exchange is introduced from the bottom of the processing box 301. The dry hot air passes through the sludge on the three-layer conveyor mesh belt 302 in sequence during the upward flow, so that it can fully contact with the sludge and take away the moisture in the sludge to dry the sludge. The frequency conversion stepless speed regulation can be used to control the conveying speed of the conveyor mesh belt 302, and then adjust the contact time between the sludge and the dry hot air, so as to achieve arbitrary adjustment of the sludge drying moisture content between 10-40%.

[0027] Step 4: The hot and humid gas generated in the sludge drying unit 3 is introduced into the condensing unit 4, thereby liquefying the steam in the gas, and the liquefied water is discharged to the factory sewage pipe. The liquefied dry and cold gas enters the heat exchange unit 1 again to exchange heat with the high-temperature desalted water to realize circulation.

[0028] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A sludge drying system for recycling waste heat, characterized in that: It includes a heat exchange unit, a sludge forming unit, a sludge drying unit and a condensing unit. The sludge drying unit includes a processing box, and a plurality of conveying mesh belts arranged at intervals from top to bottom are installed in the processing box. The sludge forming unit is arranged on one side of the upper end of the processing box, and a discharge port is arranged on one side of the lower end of the processing box. The waste heat medium inlet end of the heat exchange unit is connected to the high-temperature medium generated in the conversion reaction stage, the bottom of the treatment box is connected to a hot air delivery pipe connected to the dry hot air exhaust end of the heat exchange unit, the top of the treatment box is connected to a return air pipe, the end of the return air pipe is connected to the condensation unit, and the liquefied dehumidified gas exhaust end of the condensation unit is connected to the heat exchange unit.

2. The sludge drying system for recovering waste heat from conversion according to claim 1 is characterized in that: A constant temperature control heat exchanger is arranged in the middle of the hot air conveying pipe, and the constant temperature control heat exchanger is connected to the high temperature medium generated in the shift reaction stage.

3. The sludge drying system for recovering waste heat from conversion according to claim 1 is characterized in that: The material conveying mesh belts in the processing box are arranged in three parts, namely, upper, middle and lower parts, and the upper and lower adjacent material conveying mesh belts are arranged head to tail in a staggered manner.

4. The sludge drying system for recovering waste heat from conversion according to claim 1 is characterized in that: A plurality of hot and humid air exhaust hoods are arranged at intervals on the upper end of the treatment box, and the upper ends of the plurality of hot and humid air exhaust hoods are connected to the return air pipe. A plurality of hot air inlets are arranged on the bottom of the treatment box, and the hot air inlets are connected to the hot air delivery pipe.

5. The sludge drying system for recovering waste heat from conversion according to claim 1 is characterized in that: The sludge drying unit comprises a hopper and a strip cutting mechanism, and the strip cutting mechanism is arranged at the bottom of the hopper.

6. A sludge drying method using the sludge drying system according to any one of claims 1 to 5, characterized in that: The steps include: After the desalted water and the shift gas are heat exchanged, a portion is passed into the deaerator tank, and the other portion is passed into the heat exchange unit, so that the heat exchange unit generates dry hot air, and then the dry hot air is passed into the bottom of the treatment box in the sludge forming unit; After flocculation, the sludge is put into the butterfly screw machine for dehydration. After dehydration, it is sent to the sludge forming unit for cutting into strips, and then discharged onto the conveyor mesh belt, so that the cut sludge is evenly laid on the conveyor mesh belt and transported by the conveyor mesh belt; The dry hot air introduced into the treatment box contacts the sludge on the conveyor belt during its upward flow and takes away the moisture in the sludge to dry it. At the same time, the hot and humid gas generated is introduced into the condensation unit for liquefaction and dehumidification. The dehumidified dry cold air then enters the heat exchange unit for heat exchange with high-temperature desalted water to realize circulation.

7. The sludge drying method for recovering conversion waste heat according to claim 6 is characterized in that: In the step 1, the temperature of the hot dry air introduced into the treatment box is controlled between 70°C and 80°C.

8. The sludge drying method for recovering conversion waste heat according to claim 6, characterized in that: In the step three, variable frequency stepless speed regulation is used to control the conveying speed of the conveyor belt, and the moisture content of the dried sludge is controlled between 10-40%.

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