A sludge drying system and drying process based on high-temperature heat pump steam technology

Abstract

The application discloses a sludge drying system and drying process based on high-temperature heat pump steam technology, which comprises a partition type sludge drying device, a low-temperature side heat exchange device, a heat pump steam generator, a heat pump compressor, a throttling device and a circulating pipeline; further comprising a pressurized circulating pump, a wastewater treatment module and a waste gas treatment module. The drying process adopts high-temperature heat pump technology to absorb heat from a waste gas heat source above 100 DEG C, then heats the condensed water at 100 DEG C to generate high-temperature steam above 150 DEG C, realizes closed circulation of the steam heat source for sludge high-temperature drying, and simultaneously carries out organic phase liquefaction separation on the waste gas generated in the sludge drying process, thereby reducing the difficulty of waste gas treatment. The overall energy consumption is reduced by more than 60% compared with a municipal steam system, the process can be distributedly arranged, resources are saved, and the emission of pollutants in the sludge drying process is reduced, so that the process has high economic value and environmental protection value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sludge drying system and process, in particular to a sludge drying system and drying process based on high-temperature heat pump steam technology. BACKGROUND

[0002] In the field of sludge drying, there are currently two main directions for sludge drying treatment: the first is low-temperature sludge drying: the heat source directly heats air, and the hot air directly heats the sludge, then the hot air carries out the moisture and organic matter in the sludge, achieving the purpose of sludge drying and concentration; this direct hot air drying method not only conducts heat transfer but also mass transfer, requiring a low-temperature heat source, belonging to low-temperature drying, the exhaust gas has a low concentration of organic phase, and the total exhaust gas volume is large, making the exhaust gas treatment difficult.

[0003] The other is high-temperature sludge drying: the heat source heats the sludge through a partition, so that the moisture and organic matter in the sludge are directly vaporized after being heated and separated from the sludge, achieving the purpose of sludge drying and concentration; this method of heating the sludge through a heat source partition requires a high-temperature heat source, belongs to high-temperature drying, the exhaust gas has a high concentration of organic phase, and the total exhaust gas volume is small, making the exhaust gas treatment relatively easy. In high-temperature sludge drying, high-temperature steam at about 150℃ is usually used as the heat source, the condensate water generated after the steam is heated has a temperature of about 100℃, and the exhaust gas after the sludge is dried has a temperature of above 100℃. Such high-temperature steam sources are usually municipal steam or gas boilers, and the energy consumption and cost are relatively high.

[0004] With the development of heat pump technology, heat pump technology has been applied in the field of sludge drying to some extent, but most of the applications are in the field of low-temperature sludge drying. For example, Chinese patent CN115893797A discloses a process scheme in which a heat pump condenser provides circulating hot air to heat and dry the sludge, and a low-temperature side heat exchange device cools and dehydrates the circulating air. Chinese patent CN116102231A discloses a process scheme in which a heat pump condenser provides circulating hot air to heat and dry the sludge, and a low-temperature side heat exchange device provides cold water to cool and dehydrate the circulating air. These are all applications of heat pump technology in the field of low-temperature sludge drying. The existing high-temperature drying process still mainly relies on external high-temperature steam sources, resulting in low energy utilization rate; the exhaust gas treatment of low-temperature drying is complex. When heat pump technology is applied to the high-temperature drying process, the following problems exist: the steam generated by the heat pump is not hot enough, a water vapor compressor is needed to increase the pressure and temperature, the process is complex, the cost is high, the system stability is poor, and the energy-saving effect is worse than that of the heat pump directly generating high-temperature steam. If a heat pump system can be developed to directly recover waste heat and generate steam, the energy consumption can be reduced by about 60%. SUMMARY

[0005] Purpose of the invention: In order to solve the problems existing in the prior art, the present invention provides a sludge drying system and drying process based on high-temperature heat pump steam technology, which achieves high efficiency and energy saving and reduces the difficulty of waste gas treatment through waste heat recovery and closed-loop circulation.

[0006] Technical Solution: To achieve the above objectives, the present invention can adopt the following technical solution: a sludge drying system based on high-temperature heat pump steam technology, comprising:

[0007] A partition wall sludge drying unit is used to receive wet sludge sources and complete the drying process;

[0008] Low-temperature side heat exchange device, used to recover waste heat from exhaust gas and exchange heat with heat pump system;

[0009] A heat pump system includes a heat pump steam generator, a heat pump compressor, a throttling device, and circulation piping.

[0010] A pressurized circulating pump is connected to the condensate outlet of the partitioned sludge drying device and the heat pump steam generator.

[0011] Wastewater treatment module, used to treat liquid wastewater separated by the low-temperature side heat exchange device;

[0012] The exhaust gas treatment module is used to treat the non-condensable gas separated from the low-temperature side heat exchanger.

[0013] Furthermore, the partition wall sludge drying device is used to receive wet sludge sources and complete the drying process to form dry sludge.

[0014] Furthermore, in the heat pump system, the heat pump compressor and the throttling device form a working fluid circulation pipeline, which is connected between the heat pump steam generator and the low-temperature side heat exchange device to realize the vaporization drive of the working fluid by the waste heat of the exhaust gas.

[0015] Furthermore, the partition wall sludge drying device is also connected to a preheating steam source, which preheats the sludge to produce high-temperature exhaust gas above 100°C and condensate above 100°C.

[0016] Furthermore, a dust removal device is provided between the partition wall sludge drying device and the low-temperature side heat exchange device, and the dust removal device is connected to the exhaust gas outlet of the partition wall sludge drying device.

[0017] The drying process of the sludge drying system based on high-temperature heat pump steam technology mentioned above includes the following steps:

[0018] 1) Input the wet sludge source into the partition-type sludge drying unit;

[0019] 2) The partition wall sludge drying device is preheated by a preheating steam source to generate high-temperature waste gas and condensate;

[0020] 3) The high-temperature exhaust gas is treated by a dust removal device and then introduced into a low-temperature heat exchange device;

[0021] 4) The condensate is pressurized by a pressurized circulating pump and then delivered to the heat pump steam generator;

[0022] 5) Start the heat pump system, and use the heat pump compressor, throttling device, and low-temperature heat exchanger to compress and heat the working fluid, regenerate the working fluid, and treat the waste gas in a coordinated manner.

[0023] 6) Turn off the preheating steam source and return the high-temperature steam to the indirect sludge drying unit to dry the wet sludge. The water and organic phase in the wet sludge are vaporized and discharged to the dust removal unit and then enter the low-temperature heat exchange unit. The high-temperature steam releases heat in the indirect sludge drying unit and becomes condensate. The condensate is then pumped back into the heat pump steam generator by a pressurized circulating pump, and the cycle continues.

[0024] 7) The sludge drying exhaust gas discharged from the partition wall sludge drying device is separated into liquid wastewater and non-condensable gas after dust removal and low-temperature heat exchange, and then enters the wastewater treatment module and the exhaust gas treatment module for treatment respectively.

[0025] Furthermore, the working fluid compression process described in step 5) is as follows: the heat pump system compresses the heat pump working fluid through the heat pump compressor, turning the low-temperature, low-pressure working fluid into a high-temperature, high-pressure gaseous working fluid. The high-temperature, high-pressure gaseous working fluid enters the heat pump steam generator, where the condensate is heated and vaporized into high-temperature water vapor. At the same time, the high-temperature, high-pressure gaseous working fluid becomes a high-pressure liquid working fluid.

[0026] Furthermore, the working fluid circulation step described in step 5) is as follows: the high-pressure liquid working fluid is cooled by isenthalpic means through a throttling device to become a low-temperature, low-pressure liquid working fluid. The low-temperature, low-pressure liquid working fluid enters the low-temperature side heat exchange device to directly / indirectly absorb the total heat of the waste gas, vaporizes, and then enters the heat pump compressor, thus completing the cycle.

[0027] Furthermore, the waste gas treatment linkage step in step 5) is as follows: the low-temperature, low-pressure liquid working fluid absorbs heat from the waste gas through the low-temperature side heat exchange device to cool the waste gas, causing the organic phase and part of the water vapor in the waste gas to liquefy and become wastewater.

[0028] Furthermore, in step 7), the sludge drying exhaust gas containing water vapor, organic phase, and other substances discharged from the partition sludge drying device at a temperature above 100°C is cooled to below 100°C after being removed by a dust removal device. Most of the water vapor and organic phase are converted into liquid wastewater, and the remaining non-condensable gas is discharged to the exhaust gas treatment module for treatment; the wastewater enters the wastewater treatment module for treatment.

[0029] Beneficial effects: This invention has the following advantages:

[0030] (1) Significantly reduce energy consumption and improve energy utilization rate: This invention recovers the waste heat of waste gas above 100°C generated during sludge drying process through high-temperature heat pump technology, and uses it to heat 100°C condensate to generate high-temperature steam above 150°C, forming a closed heat source cycle. Compared with traditional municipal steam or gas boiler heating, the overall energy consumption is reduced by more than 60%, and the energy utilization rate is increased to more than 80%, greatly reducing the dependence on external heat sources. (2) Simplify the waste gas treatment process and reduce treatment costs: After the dried waste gas is cooled by the low-temperature side heat exchange device, the water vapor and organic phase are separated into liquid wastewater and non-condensable gas through liquefaction. The concentration of pollutants in the waste gas is reduced, the wastewater can directly enter the conventional treatment system, the volume of non-condensable gas is reduced, and the load of the waste gas treatment device is significantly reduced. (3) Outstanding environmental benefits and reduced carbon emissions: The closed-loop system avoids the heat loss of high-temperature steam discharge in the traditional process, and at the same time reduces the emission of volatile organic compounds and dust, greatly reducing the total emission of pollutants. (4) Supports distributed deployment and is highly adaptable: The modular design of the system (such as the independent and separable partition drying unit and heat pump system) supports distributed installation and is suitable for small and medium-sized sewage treatment plants or industrial parks. The footprint of a single set of equipment is reduced by 30%, and it does not rely on a centralized steam pipeline network, significantly improving scalability and flexibility. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the system structure and process flow of a specific embodiment of the present invention.

[0032] Explanation of reference numerals in the attached drawings: 1. Wet sludge source; 2. Indirect sludge drying device; 3. Dust removal device; 4. Low-temperature side heat exchange device; 5. Waste gas treatment module; 6. Wastewater treatment module; 7. Heat pump compressor; 8. Throttling device; 9. Heat pump steam generator; 10. Pressurized circulating pump; 11. Preheated steam source; 12. Dry sludge. Detailed Implementation

[0033] like Figure 1 As shown, the sludge drying system based on high-temperature heat pump steam technology of the present invention includes a partitioned sludge drying device 2, a dust removal device 3, a low-temperature side heat exchange device 4, a waste gas treatment module 5, a wastewater treatment module 6, a heat pump compressor 7, a throttling device 8, a heat pump steam generator 9, a pressurized circulating pump 10, and a preheating steam source 11.

[0034] The indirect-contact sludge drying device 2 receives wet sludge source 1 and dries it to form dry sludge 12. The low-temperature side heat exchange device 4 recovers waste heat from the exhaust gas and exchanges heat with the heat pump system. A dust removal device 3 is provided between the indirect-contact sludge drying device 2 and the low-temperature side heat exchange device 4, and the dust removal device 3 is connected to the exhaust gas outlet of the indirect-contact sludge drying device 2. The indirect-contact sludge drying device 2 is also connected to a preheating steam source 11, which preheats the sludge to produce high-temperature exhaust gas above 100°C and condensate at 100°C.

[0035] The heat pump system includes a heat pump steam generator 9, a heat pump compressor 7, a throttling device 8, and a circulation pipeline; the pressurized circulation pump 10 is connected to the condensate outlet of the partition sludge drying device 2 and the heat pump steam generator 9; in the heat pump system, the heat pump compressor 7 and the throttling device 8 form a working fluid circulation pipeline, which is connected between the heat pump steam generator 9 and the low-temperature side heat exchange device 4 to realize the vaporization drive of the working fluid by the waste heat of the exhaust gas.

[0036] The wastewater treatment module 6 is used to treat the liquid wastewater separated by the low-temperature heat exchange device 4; the waste gas treatment module 5 is used to treat the non-condensable gas separated by the low-temperature heat exchange device 4.

[0037] The sludge drying process is as follows:

[0038] 1) Input the wet sludge source 1 into the partition-type sludge drying device 2;

[0039] 2) The partition sludge drying device 2 is preheated by the preheating steam source 11 to generate high-temperature waste gas above 100°C and condensate water at 100°C;

[0040] 3) The high-temperature exhaust gas above 100℃ is treated by the dust removal device 3 and then introduced into the low-temperature side heat exchange device 4;

[0041] 4) The 100℃ condensate is pressurized by the pressurized circulation pump 10 and then delivered to the heat pump steam generator 9 of the heat pump system;

[0042] 5) Start the heat pump system. The heat pump compressor 7, throttling device 8, and low-temperature side heat exchanger 4 work together to compress and heat the working fluid, circulating it and treating the waste gas: The heat pump system compresses the heat pump working fluid (hereinafter referred to as "working fluid") through the heat pump compressor 7, transforming the low-temperature, low-pressure working fluid into a high-temperature, high-pressure gaseous working fluid. This high-temperature, high-pressure gaseous working fluid enters the heat pump steam generator 9, where the condensate is heated and vaporized into 150°C high-temperature water vapor. Simultaneously, the high-temperature, high-pressure gaseous working fluid becomes a high-pressure liquid working fluid. The high-pressure liquid working fluid undergoes isenthalpic cooling through the throttling device 8, becoming a low-temperature, low-pressure liquid working fluid. This low-temperature, low-pressure liquid working fluid enters the low-temperature side heat exchanger 4, directly (or indirectly) absorbing the total heat of the waste gas, vaporizing, and then entering the heat pump compressor 7, thus completing the cycle. The low-temperature, low-pressure liquid working fluid absorbs heat from the waste gas through the low-temperature side heat exchanger 4, cooling the waste gas and liquefying the organic phase and some water vapor in the waste gas into wastewater.

[0043] 6) The preheating steam source is turned off. At the same time, the 150°C high-temperature steam generated in the heat pump steam generator 9 enters the indirect sludge drying device 2 to dry the wet sludge. The water and organic phases in the wet sludge are vaporized and discharged to the dust removal device 3 and then enter the low-temperature heat exchange device 4. The 150°C high-temperature steam releases heat in the indirect sludge drying device 2 and becomes 100°C condensate. The 100°C condensate enters the heat pump steam generator 9 again through the pressurized circulation pump 10. This cycle continues.

[0044] 7) The sludge drying exhaust gas containing water vapor, organic phases, and other substances, discharged from the partition-type sludge drying device 2 at a temperature above 100°C, is filtered by the dust removal device 3 and then enters the low-temperature heat exchange device 4 for cooling to below 100°C. Most of the water vapor and organic phases then become liquid wastewater, and the remaining non-condensable gas is discharged to the exhaust gas treatment module 5 for further treatment. The wastewater then enters the wastewater treatment module 6 for further treatment.

[0045] This invention relates to a sludge drying system based on high-temperature heat pump steam technology, which efficiently dries sludge. Based on test results of key process sections, it utilizes high-temperature heat pump technology to absorb heat from waste gas at temperatures above 100°C, then heats condensate at 100°C to generate high-temperature steam exceeding 150°C. This achieves a closed-loop steam heat source for high-temperature sludge drying. Simultaneously, it performs organic phase liquefaction separation on the waste gas generated during sludge drying, reducing the difficulty of waste gas treatment. Overall energy consumption is reduced by more than 60% compared to municipal steam systems. Furthermore, this process can be distributed, saving resources and reducing pollutant emissions during sludge drying, demonstrating significant economic and environmental value.

Claims

1. A drying process of a sludge drying system based on high-temperature heat pump steam technology, characterized by: The system comprises: a partitioned sludge drying device, a low-temperature side heat exchange device, a heat pump system comprising a heat pump steam generator, a heat pump compressor, a throttling device and a circulating pipeline; a pressurized circulating pump connecting the condensate outlet of the partitioned sludge drying device and the heat pump steam generator; a wastewater treatment module, a waste gas treatment module, a preheating steam source, a dust removal device; The drying process comprises the following steps: 1) inputting a wet sludge source into the partitioned sludge drying device; 2) preheating the partitioned sludge drying device by the preheating steam source to generate high-temperature waste gas above 100℃ and condensate water above 100℃; 3) introducing the high-temperature waste gas into the low-temperature side heat exchange device after treatment by the dust removal device; 4) delivering the condensate water to the heat pump steam generator after pressurization by the pressurized circulating pump; 5) starting the heat pump system to perform linkage of working medium compression and heating, working medium circulation regeneration and waste gas treatment by the heat pump compressor, the throttling device and the low-temperature side heat exchange device; wherein the working medium compression treatment step is that the heat pump system compresses the working medium by the heat pump compressor to change the low-temperature and low-pressure working medium into high-temperature and high-pressure gaseous working medium, and the high-temperature and high-pressure gaseous working medium enters the heat pump steam generator to heat the condensate water therein to vaporize it into high-temperature water vapor, while the high-temperature and high-pressure gaseous working medium changes into high-pressure liquid working medium; the waste gas treatment linkage step is that the low-temperature and low-pressure liquid working medium absorbs heat from the waste gas by the low-temperature side heat exchange device to cool the waste gas and liquefy the organic phase and part of the water vapor in the waste gas into wastewater; 6) closing the preheating steam source, returning the high-temperature water vapor to the partitioned sludge drying device to dry the wet sludge therein, vaporizing the water and organic phase in the wet sludge to the dust removal device and then into the low-temperature side heat exchange device; the high-temperature steam changes into condensate water after heat release in the partitioned sludge drying device, and the condensate water enters the heat pump steam generator again by the pressurized circulating pump, thus forming a cycle; 7) the sludge drying waste gas discharged from the partitioned sludge drying device is separated into liquid wastewater and non-condensable gas after dust removal and low-temperature side heat exchange, and is delivered into the wastewater treatment module and the waste gas treatment module respectively for treatment.

2. The drying process according to claim 1, characterized in that: In step 5), the working medium circulation step is that the high-pressure liquid working medium changes into low-temperature and low-pressure liquid working medium after isenthalpic cooling by the throttling device, the low-temperature and low-pressure liquid working medium enters the low-temperature side heat exchange device to directly / indirectly absorb the total heat of the waste gas to vaporize and then enters the heat pump compressor, thus forming a cycle.

3. The drying process of claim 1, wherein: In step 7), the sludge drying waste gas above 100℃ containing water vapor and organic phase discharged from the partitioned sludge drying device is cooled to below 100℃ after dust removal by the dust removal device and enters the low-temperature side heat exchange device, most of the water vapor and organic phase change into liquid wastewater, and the remaining part of the non-condensable gas is discharged to the waste gas treatment module for treatment; the wastewater enters the wastewater treatment module for treatment.

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