A sludge reduction treatment process and a special device thereof

Abstract

The present invention provides a sludge reduction treatment process and a special device thereof, belonging to the field of environmental sludge treatment. The multi-layer mesh belt type sludge low-temperature drying machine of the present invention comprises: a conveying mesh belt, an auxiliary guide device and a return duct; the conveying mesh belt conveys the sludge block along the direction of movement until the end enters the auxiliary guide device, and under the action of the auxiliary guide device, the sludge block is uniformly turned over; the opening of the return duct enhances the circulation of dry hot air flow, effectively increases the drying air volume and reduces the working pressure of the dehumidification heat pump; multiple evaporators in series, multiple refrigeration compressors in parallel and multiple condensers in series; multiple evaporators cool the incoming air flow in stages and discharge condensed water; under the parallel operation of multiple refrigeration compressors, saturated air reaches the condenser, and multiple condensers heat the incoming air flow in stages to obtain dry hot air; the dehumidification heat pump freely sets the evaporation and condensation temperatures, reduces the heat pump pressure difference, and makes the system more energy-efficient.

Description

Technical Field

[0001] The invention belongs to the field of environmental sludge treatment, and specifically relates to a sludge reduction treatment process and a special device thereof. Background Art

[0002] Wet sludge is a byproduct of sewage treatment. The composition of sludge is extremely complex, mainly containing about 80-90% water, as well as other recyclable organic matter, various organic substances, multiple trace elements, and pathogenic microorganisms, parasite eggs, heavy metals, etc. that may have adverse effects on the environment. The harmless and resourceful treatment of wet sludge is an important issue in ecological and environmental protection worldwide.

[0003] At present, the amount of residual sludge generated by urban sewage treatment plants in my country is huge, and the sludge treatment situation is very severe. With the development of sludge treatment technology in recent years, sludge drying and pyrolysis technology has become the primary treatment solution. Sludge drying and pyrolysis technology is a technology that decomposes sludge under high temperature and oxygen-free environment and finally obtains organic matter. On the basis of thermal drying, it can ensure the superiority of sludge incineration while largely avoiding secondary pollution in the sludge treatment process.

[0004] At present, a large part of sludge drying technology adopts steam with a temperature exceeding 100℃ or other methods for drying, which not only consumes a large amount of phase change heat of water evaporation, but also causes a large amount of organic matter and odor to evaporate into the air, causing serious air pollution. At the same time, it causes the loss of a large amount of low-boiling point organic matter, which is not conducive to the subsequent sludge resource utilization, including thermochemical energy and land utilization. How to achieve green and low-carbon sludge drying is one of the key technologies of sludge drying.

[0005] Patent CN200410086312.5 discloses a wet sludge incineration treatment method and incineration treatment device, which integrates the drying, incineration and smoke harmless treatment of wet sludge in a single device for simultaneous processing. Although the treatment process is simplified, the treatment device and method require the wet sludge to be incinerated in an incinerator at a temperature of 800-950°C, which has high requirements for equipment and relatively high energy consumption. The use of this device and process has problems such as large initial investment and high operating costs.

[0006] Low-temperature drying is one of the main research directions for treating sludge because of its low cost and relatively small equipment requirements. Therefore, it has become an urgent problem to develop a treatment process that can effectively improve the drying efficiency, enhance the utilization rate of heat, and reduce the cost of sludge drying while drying sludge at low temperature.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The first object of the present invention is to provide a sludge reduction treatment process, which can effectively improve the drying efficiency and heat utilization rate while drying the sludge at low temperature;

[0009] The second purpose of the present invention is to provide a special device for sludge reduction treatment process, which greatly improves the sludge drying efficiency and process feasibility through clever design and reasonable combination.

[0010] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] A special device for sludge reduction treatment process comprises a multi-layer mesh belt type sludge low-temperature dryer and a dehumidification heat pump, wherein the multi-layer mesh belt type sludge low-temperature dryer comprises: a conveying mesh belt, an auxiliary guide device and a return duct; the conveying mesh belt conveys the sludge block along the moving direction until the end enters the auxiliary guide device, and under the action of the auxiliary guide device, the sludge block is uniformly turned over; the opening of the return duct enhances the circulation of dry hot air flow, effectively increases the drying air volume and reduces the working pressure of the dehumidification heat pump; the dehumidification heat pump adopts a multi-stage heat pump, comprising: a plurality of evaporators in series, a plurality of refrigeration compressors in parallel and a plurality of condensers in series; a plurality of evaporators cool the incoming air flow in stages and discharge condensed water; when a plurality of refrigeration compressors work in parallel, saturated air reaches the condenser, and a plurality of condensers heat the incoming air flow in stages to obtain dry hot air; the dehumidification heat pump freely sets the evaporation and condensation temperatures, reduces the pressure difference of the heat pump, and makes the system more energy-efficient.

[0012] Furthermore, the multi-layer mesh-belt sludge low-temperature dryer includes: a feed inlet, a conveying mesh belt, an auxiliary guide device, a dry mud outlet, a hot and humid air duct, a hot and humid air duct valve, a dry air duct valve, a dry air duct, a reflux duct main valve, a reflux duct, a reflux duct sub-valve 01, a reflux duct sub-valve 02, a reflux duct sub-valve 03 and a special distributor.

[0013] Furthermore, after the original sludge is dehydrated, a solidifying agent and a flocculant are added, and after being compressed by a high-pressure belt machine, it is sent to a low-temperature dryer for drying. By opening and closing the valve, the number of reflux cycles of the dry hot air flow and the independent operation of the heat pump in parallel are controlled to improve the drying efficiency.

[0014] Furthermore, the moisture content of the original sludge is 95%.

[0015] Furthermore, the added curing agent is a composite iron salt, accounting for 7.5%; the added flocculant is PAM, accounting for 0.5%.

[0016] Furthermore, the moisture content of the sludge after compression by the high-pressure belt machine is 73%.

[0017] Furthermore, the temperature of the low temperature drying is 65-75°C.

[0018] Furthermore, the number of reflux cycles of the dry hot airflow is 3-5 times.

[0019] Furthermore, the hot and humid air duct valve is closed, and the reflux duct main valve is opened to allow most of the gas to flow into the reflux duct, and most of the gas is re-integrated into the bottom of the dryer through the reflux duct to increase the air volume of the dry air, thereby improving the drying efficiency; according to actual needs, the corresponding reflux sub-valve 01, reflux sub-valve 02 and / or reflux sub-valve 03 are opened in a targeted manner to enhance the drying of the sludge on the conveyor belt 2.

[0020] Furthermore, the overall efficiency of the dehumidification heat pump is 700%.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] (1) The sludge reduction treatment process of the present invention can effectively improve the drying efficiency and heat utilization rate while drying the sludge at low temperature.

[0023] (2) The dedicated device for sludge reduction treatment process of the present invention greatly improves the sludge drying efficiency and process feasibility through ingenious design and reasonable combination.

[0024] (3) The present invention uses the ingenious design of a multi-layer conveyor belt and an auxiliary guide device to allow the sludge strips or blocks to be turned over three times, with both the upper and lower surfaces being dried by hot air, thereby greatly improving the drying efficiency and drying uniformity.

[0025] (4) The present invention opens relevant valves and pipelines to allow most of the dry hot air flow to circulate and dry, thereby increasing the air volume of the drying air and thus improving the drying efficiency; the corresponding reflux valve can also be opened in a targeted manner according to actual needs to achieve enhanced drying of the sludge on the conveyor belt.

[0026] (5) In the present invention, the hot and humid air coming out of the dryer is first returned to the evaporator, and multiple evaporators cool the incoming air flow in stages (down to a wind temperature of 20°C in sequence) and discharge condensed water; when multiple refrigeration compressors work in parallel (each heat pump operates independently and does not interfere with each other), the saturated air reaches the condenser, and multiple condensers heat the incoming air flow in stages (up to a wind temperature of 70°C) to obtain dry hot air. The dehumidification heat pump can set the evaporation and condensation temperatures to reduce the heat pump pressure difference, making the system more energy-efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of the whole process of the present invention.

[0028] Figure 2This is a schematic diagram of the working principle and structure of the multi-layer mesh-belt sludge low-temperature dryer.

[0029] Figure 3 This is the working principle diagram of the dehumidification heat pump.

[0030] Figure 4 This is the energy efficiency diagram of the dehumidification heat pump.

[0031] Figure numerals: 1. Feed inlet; 2. Conveyor mesh belt; 3. Auxiliary guide device; 4. Dry mud outlet; 5. Hot and humid air duct; 6. Hot and humid air duct valve; 7. Dehumidification heat pump; 8. Dry air duct valve; 9. Dry air duct; 10. Reflux duct main valve; 11. Reflux duct; 12. Reflux sub-valve 01; 13. Reflux sub-valve 02; 14. Reflux sub-valve 03; 15. Special distributor. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0033] A special device for sludge reduction treatment process comprises: a screw stack dehydration compressor, a mixer, a high-pressure belt machine, a buffer silo, a multi-layer mesh belt type sludge low-temperature drying machine and a dehumidification heat pump.

[0034] Among them, the multi-layer mesh belt type sludge low-temperature dryer includes: a feed inlet 1, a conveying mesh belt 2, an auxiliary guide device 3, a dry mud outlet 4, a hot and humid air duct 5, a hot and humid air duct valve 6, a dry air duct valve 8, a dry air duct 9, a reflux duct main valve 10, a reflux duct 11, a reflux duct sub-valve 01 12, a reflux duct sub-valve 02 13, a reflux duct sub-valve 03 14 and a special distributor 15.

[0035] The dehumidification heat pump includes: evaporator, refrigeration compressor, condenser and expansion valve.

[0036] like Figure 2As shown, the working principle of the multi-layer mesh belt type sludge low-temperature dryer is as follows: before the sludge is added, electric energy is input into the refrigeration compressor in the dehumidification heat pump 7, and the wet sludge (water content 73%) enters the dryer from the feed inlet 1, and is sheared by the special distributor 15 to form strips or blocks; at this time, the dry air duct valve 8 is opened, and the dry hot air in the dehumidification heat pump 7 will enter the bottom of the dryer through the dry air duct 9, pass through the four layers of conveyor mesh belts 2 from bottom to top, dry the sludge on the conveyor mesh belt 2, and finally flow out of the dryer from the wet hot air duct 5 at the top of the dryer; the sludge strips or blocks are subjected to weight. The force acts on the conveyor mesh belt 2. As the conveyor mesh belt 2 is transported from left to right and reaches the end of the conveyor mesh belt 2, the sludge strips are affected by the auxiliary guide device 3 and still maintain the original contact state (that is, the side in contact with the conveyor mesh belt 2 is still close to the conveyor mesh belt 2) until the sludge strips or blocks are removed from the auxiliary guide device 3. At this time, due to the effect of gravity, the sludge strips or blocks will fall from the first layer of conveyor mesh belt 2 to the second layer of conveyor mesh belt 2. The upper and lower surfaces of the sludge strips or blocks falling on the second layer of conveyor mesh belt 2 are exactly opposite to those of the first layer of conveyor mesh belt 2, which can achieve rapid air drying on both sides of the sludge. The sludge that reaches the second-layer conveyor mesh belt 2 then continues to move from right to left along the conveyor mesh belt 2 until it reaches the end of the second-layer conveyor mesh belt 2, enters the auxiliary guide device 3, and continues to flow out to the third-layer conveyor mesh belt 2 in the same principle. The sludge strips or blocks move along the third conveyor mesh belt 2 in the same way and then reach the fourth-layer conveyor mesh belt. At this time, the sludge strips or blocks are turned over three times, and both the upper and lower surfaces are dried by hot air, which greatly improves the drying efficiency and drying uniformity. With the transmission of the fourth-layer conveyor mesh belt 2, the sludge strips or blocks finally reach the end of the conveyor mesh belt 2 and flow out of the dryer from the dry mud outlet at the lower end of the conveyor mesh belt 2. In order to enhance the drying efficiency of the sludge low-temperature dryer, when the dry hot air enters the bottom of the dryer through the dry air duct 9, it passes through the four layers of conveyor mesh belts 2 from bottom to top in turn, and dries the sludge on the conveyor mesh belt 2, due to the fast air flow speed, the moisture brought out is often not high (that is, the moisture content of the air flow reaching the top at this time is not high). In order to improve the utilization rate of the hot dry gas, reduce the working pressure of the dehumidification heat pump and increase the drying air volume, the moist hot air duct valve 6 can be closed at this time, and the reflux duct main valve 10 can be opened to allow most of the gas to flow into the reflux duct 11, and most of the gas is re-integrated into the bottom of the dryer through the reflux duct 11, thereby increasing the air volume of the dry air and thus improving the drying efficiency; the corresponding reflux sub-valve 01 12, reflux sub-valve 02 13 and / or reflux sub-valve 03 14 can also be opened in a targeted manner according to actual needs to enhance the drying of the sludge on the conveyor mesh belt 2.

[0037] The dehumidification heat pump uses a multi-stage heat pump, and its working principle is: the hot and humid air (40-50℃) coming out of the dryer first returns to the evaporator, and multiple evaporators cool the incoming air flow in stages (down to 20℃ in sequence) and discharge condensed water; under the parallel operation of multiple refrigeration compressors (each heat pump operates independently and does not interfere with each other), saturated air reaches the condenser, and multiple condensers heat the incoming air flow in stages (until the air temperature is 70℃) to obtain dry hot air. The dehumidification heat pump can set the evaporation and condensation temperatures, reduce the heat pump pressure difference, and make the system more energy-efficient.

[0038] like Figure 4 As shown in the figure, the efficiency of the dehumidification heat pump is analyzed: when 1KW of electric energy is input from the refrigeration compressor, 4KW of heating capacity can be released when it reaches the condenser (i.e. 1KW of electric energy can obtain 4KW of heat, and the heat pump heating efficiency is 400%), and 3KW of cooling capacity can be absorbed from the evaporator mechanism, so the comprehensive efficiency (heat pump dehumidification + heating) is 700% (i.e. 1KW of electric energy can obtain 4KW of heat + 3KW of cooling capacity). The use of multiple compressors in parallel and the independent operation of each heat pump can reduce the compression ratio of the single-stage compressor in the heat pump unit, so that the compressor has a lower failure rate and a longer life during use, and the recovery of heat energy and heating of air flow are more efficient, and the compressor efficiency is high.

[0039] The working principle of the whole sludge reduction treatment process dedicated device is as follows: the original sludge is first transported to the spiral dehydration compressor for preliminary dehydration to reduce the water content of the sludge for the first time; the sludge after the first dehydration enters the mixer, and after adding the curing agent and flocculant, it is transported to the high-pressure belt machine for high-pressure compression, and the sludge water content is further reduced, and it is transported to the buffer silo for temporary storage; at this time, although the sludge water content is controlled at 70-80%, if it is directly incinerated at this time, on the one hand, the higher water content will lead to a decrease in the calorific value of the sludge combustion, causing unnecessary energy waste; on the other hand, it may cause environmental pollution or dangerous accidents due to insufficient combustion or uneven heating. Therefore, the sludge temporarily stored in the buffer silo will be transported to the multi-layer mesh belt low-temperature dryer for drying treatment. Through the full drying of the sludge low-temperature dryer and the efficient use of the heat of the dehumidification heat pump, the dried sludge with a water content of 10%-40% is finally obtained and collected in the sludge drying silo.

[0040] Example 1

[0041] A sludge reduction treatment process is carried out using the above device, and the steps are as follows:

[0042] (1) First, the original sludge with a moisture content of about 95% is dehydrated by a spiral dehydration concentrator to reduce the moisture content of the sludge to about 85%;

[0043] (2) Then, 7.5% of the total amount of composite iron salt and 0.5% of the total amount of PAM are added to the sludge concentrated by the screw dehydration concentrator, mixed by a mixer and then transported to the high-pressure belt conveyor. After high-pressure compression by the high-pressure belt conveyor (high-pressure belt filter press), the moisture content of the sludge after passing through the high-pressure belt conveyor is reduced from 85% to 73%;

[0044] (3) The discharge of the high-pressure belt conveyor enters the wet sludge buffer silo, and enters the low-temperature dryer through the transmission of the screw conveyor. It is sheared by the special distributor 15 to form strips or blocks. At this time, electric energy is input to the refrigeration compressor in the dehumidification heat pump 7 to raise the temperature of the gas to 70°C, and the dry air duct valve 8 is opened. The dry hot air (70°C) in the dehumidification heat pump 7 will pass through the dry air duct 9 into the bottom of the dryer, and pass through the four layers of conveyor mesh belts 2 from bottom to top in turn to dry the sludge on the conveyor mesh belt 2. At this time, the wet hot air duct valve 6 is closed, and the return duct main valve 10 is opened. Most of the gas flows into the return duct 11, and most of the gas is re-collected into the bottom of the dryer through the return duct 11, and converges with the dry gas transported from the dehumidification heat pump 7 through the dry air duct 9 into the dryer, realizing a circulation of the dry gas. Repeating 3 times (i.e., circulating 3 times) increases the air volume of the dry air, thereby improving the drying efficiency. The corresponding return sub-valve 01 can also be opened in a targeted manner according to actual needs. 12, reflux valve 02 13 and / or reflux valve 03 14, to achieve enhanced drying of the sludge on different conveyor belts 2. Finally, close the reflux conduit main valve 10, open the moist hot air conduit valve 6, and transport the moist hot gas to the dehumidification heat pump 7 through the moist hot air conduit. The discharge of the low temperature dryer is sent to the sludge drying bin through the scraper conveyor.

[0045] Example 2

[0046] The second circulation of the dry gas is achieved only by closing the moist hot air conduit valve 6 and opening the return conduit main valve 10. The remaining steps are the same as those in Example 1.

[0047] Example 3

[0048] Only by closing the moist hot air conduit valve 6 and opening the return conduit main valve 10, one circulation of the dry gas is achieved, and the remaining steps are the same as those in Example 1.

[0049] Example 4

[0050] Only by closing the moist hot air conduit valve 6 and opening the return conduit main valve 10, four cycles of dry gas are achieved, and the remaining steps are the same as those in Example 1.

[0051] Example 5

[0052] Only by closing the moist hot air conduit valve 6 and opening the return conduit main valve 10, five cycles of dry gas are achieved, and the remaining steps are the same as those in Example 1.

[0053] Example 6

[0054] By closing the hot and humid air duct valve 6 and opening the return duct main valve 10, the three cycles of dry gas are realized, and the dry hot air (60° C.) in the dehumidification heat pump 7 is controlled to enter the bottom of the dryer through the dry air duct 9. The remaining steps are the same as in Example 1.

[0055] Example 7

[0056] By closing the moist hot air conduit valve 6 and opening the return conduit main valve 10, the three cycles of dry gas are realized, and the dry hot air (65° C.) in the dehumidification heat pump 7 is controlled to enter the bottom of the dryer through the dry air conduit 9. The remaining steps are the same as in Example 1.

[0057] Example 8

[0058] By closing the hot and humid air duct valve 6 and opening the return duct main valve 10, the three cycles of dry gas are realized, and the dry hot air (75° C.) in the dehumidification heat pump 7 is controlled to enter the bottom of the dryer through the dry air duct 9. The remaining steps are the same as those in Example 1.

[0059] Example 9

[0060] By closing the moist hot air conduit valve 6 and opening the return conduit main valve 10, the three cycles of dry gas are realized, and the dry hot air (80° C.) in the dehumidification heat pump 7 is controlled to enter the bottom of the dryer through the dry air conduit 9. The remaining steps are the same as in Example 1.

[0061] Comparative Example 1

[0062] (1) First, the original sludge with a moisture content of about 95% is dehydrated by a spiral dehydration concentrator to reduce the moisture content of the sludge to about 85%;

[0063] (2) The sludge is then mixed with chemicals in a mixer and transported to a high-pressure belt conveyor. After high-pressure compression by the high-pressure belt conveyor (high-pressure belt filter press), the moisture content of the sludge is reduced from 85% to 68% after passing through the high-pressure belt conveyor.

[0064] (3) The discharge of the high-pressure belt conveyor enters the wet sludge buffer silo, and enters the low-temperature dryer through the transmission of the screw conveyor. It is sheared by the special distributor 15 to form strips or blocks. At this time, electric energy is input to the refrigeration compressor in the dehumidification heat pump 7 to raise the gas temperature to 70°C, and the dry air duct valve 8 is opened. The dry hot air (70°C) in the dehumidification heat pump 7 will pass through the dry air duct 9 to enter the bottom of the dryer, and pass through the four layers of conveyor mesh belts 2 from bottom to top in turn to dry the sludge on the conveyor mesh belts 2. Finally, the return duct main valve 10 is closed, and the wet hot air duct valve 6 is opened to transport the wet hot gas to the dehumidification heat pump 7 through the wet hot air duct. The discharge of the low-temperature dryer is sent to the sludge drying silo through the scraper conveyor.

[0065] Comparative Example 2

[0066] (1) First, the original sludge with a moisture content of about 95% is dehydrated by a spiral dehydration concentrator to reduce the moisture content of the sludge to about 85%;

[0067] (2) The sludge is then mixed with chemicals in a mixer and transported to a high-pressure belt conveyor. After high-pressure compression by the high-pressure belt conveyor (high-pressure belt filter press), the moisture content of the sludge is reduced from 85% to 75% after passing through the high-pressure belt conveyor.

[0068] (3) The discharge of the high-pressure belt conveyor enters the wet sludge buffer silo, and enters the low-temperature dryer through the transmission of the screw conveyor. It is sheared by the special distributor 15 to form strips or blocks. At this time, electric energy is input to the refrigeration compressor in the dehumidification heat pump 7 to raise the gas temperature to 70°C, and the dry air duct valve 8 is opened. The dry hot air (70°C) in the dehumidification heat pump 7 will pass through the dry air duct 9 to enter the bottom of the dryer, and pass through the four layers of conveyor mesh belts 2 from bottom to top in turn to dry the sludge on the conveyor mesh belts 2. Finally, the return duct main valve 10 is closed, and the wet hot air duct valve 6 is opened to transport the wet hot gas to the dehumidification heat pump 7 through the wet hot air duct. The discharge of the low-temperature dryer is sent to the sludge drying silo through the scraper conveyor.

[0069] After testing the moisture content of the dried sludge and the actual power consumption, the moisture content of the sludge was calculated according to the weight method 2 of "Inspection Methods for Sludge in Urban Wastewater Treatment Plants" CJ / T 221-2005. When the drying gas temperature is 70°C and the cycle is 3 times, the drying efficiency is better and the power consumption is lower. When the temperature of the drying gas is higher than 70°C, the power consumption increases significantly and the cost increases; when the number of cycles is less than 3 times, the drying efficiency is low (significantly lower than more than 3 times), which may be due to the small drying air volume and the fast flow rate, resulting in the sludge blocks or strips not being dried completely in time; when the number of cycles is more than 3 times, as the gas moisture content gradually increases with the increase in the number of cycles, when it is close to saturation, it cannot take away the moisture in the sludge blocks, resulting in a decrease in drying efficiency.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A special device for sludge reduction treatment, comprising a multi-layer mesh belt type sludge low-temperature dryer and a dehumidification heat pump, characterized in that: The multi-layer mesh belt type low-temperature sludge dryer comprises: a feed port (1), a conveyor mesh belt (2), an auxiliary guide device (3), a dry mud outlet (4), a moist hot air conduit (5), a moist hot air conduit valve (6), a dry air conduit valve (8), a dry air conduit (9), a return conduit main valve (10), a return conduit (11), a return conduit sub-valve 01 (12), a return conduit sub-valve 02 (13), a return conduit sub-valve 03 (14) and a special distributor (15); wet sludge with a moisture content of 73% enters the dryer from the feed port (1), is sheared by the special distributor (15), and is cut into strips or blocks; the dry air conduit valve (8) is opened, and the dehumidification heat pump The dry hot air in the dryer will pass through the dry air duct (9) and enter the bottom of the dryer, and pass through the four layers of conveyor mesh belts (2) from bottom to top in turn, drying the sludge on the conveyor mesh belts (2), and finally flow out of the dryer from the moist hot air duct (5) at the top of the dryer; the sludge strips or blocks fall on the conveyor mesh belt (2) due to the action of gravity, and as the conveyor mesh belt (2) is conveyed from left to right to the end of the conveyor mesh belt (2), the sludge strips are affected by the auxiliary guide device (3) and still maintain the original contact state until the sludge strips or blocks are removed from the auxiliary guide device (3). At this time, due to the action of gravity, the sludge strips or blocks will fall from the first layer of conveyor mesh belt to the second layer of conveyor mesh belt. On the conveyor belt, the sludge strips or blocks fall onto the upper and lower surfaces of the second conveyor belt, which are just opposite to those of the first conveyor belt, so that both sides of the sludge can be quickly dried; the sludge on the second conveyor belt continues to move from right to left along the conveyor belt until it reaches the end of the second conveyor belt, enters the auxiliary guide device (3), and continues to flow out to the third conveyor belt in the same way. The sludge strips or blocks move along the third conveyor belt in the same way and then reach the fourth conveyor belt. At this time, the sludge strips or blocks have been turned over three times, and both the upper and lower surfaces are subjected to hot air drying, which greatly improves the drying efficiency and the degree of drying uniformity; in order to enhance the drying efficiency of the sludge low-temperature dryer To improve the drying efficiency, when the dry hot air enters the bottom of the dryer through the dry air duct (9), it passes through the four layers of conveyor mesh belts (2) from bottom to top in sequence, and dries the sludge on the conveyor mesh belt (2), the moist hot air duct valve (6) is closed, and the return duct main valve (10) is opened to allow most of the gas to flow into the return duct (11), and most of the gas is re-introduced into the bottom of the dryer through the return duct (11), thereby increasing the air volume of the dry air and thus improving the drying efficiency; the corresponding return sub-valve 01 (12), return sub-valve 02 (13) and / or return sub-valve 03 (14) can also be opened in a targeted manner according to actual needs to achieve enhanced drying of the sludge on the conveyor mesh belt (2); The dehumidification heat pump adopts a multi-stage heat pump, including: multiple evaporators connected in series, multiple refrigeration compressors connected in parallel and multiple condensers connected in series; the hot and humid air discharged from the dryer is first returned to the evaporator, and the multiple evaporators cool the incoming air flow in stages and discharge condensed water; when the multiple refrigeration compressors work in parallel, the saturated air reaches the condenser, and the multiple condensers heat the incoming air flow in stages to obtain dry hot air; the dehumidification heat pump can freely set the evaporation and condensation temperatures, reduce the pressure difference of the heat pump, and make the system more energy-efficient.

2. A sludge reduction treatment process using the sludge reduction treatment device according to claim 1, characterized in that: After the original sludge is dehydrated, a solidifying agent and a flocculant are added, and after being compressed by a high-pressure belt machine, it is sent to a low-temperature dryer for drying. By opening and closing the valve, the number of reflux cycles of the dry hot air flow and the independent operation of the heat pump in parallel are controlled to improve the drying efficiency.

3. The sludge reduction treatment process according to claim 2, characterized in that: The moisture content of the original sludge is 95%.

4. The sludge reduction treatment process according to claim 2, characterized in that: The added curing agent is composite iron salt, accounting for 7.5%; the added flocculant is PAM, accounting for 0.5%.

5. The sludge reduction treatment process according to claim 3, characterized in that: The moisture content of the sludge after compression by the high-pressure belt machine is 73%.

6. The sludge reduction treatment process according to claim 2, characterized in that: The temperature for low temperature drying is 65-75℃.

7. The sludge reduction treatment process according to claim 2, characterized in that: The number of recirculation cycles of the dry hot air flow is 3-5 times.

8. The sludge reduction treatment process according to claim 2, characterized in that: Close the moist hot air duct valve (6), open the return duct main valve (10), and allow most of the gas to flow into the return duct (11), and then return most of the gas to the bottom of the dryer through the return duct (11), thereby increasing the air volume of the dry air and thus improving the drying efficiency; open the corresponding return sub-valve 01 (12), return sub-valve 02 (13) and / or return sub-valve 03 (14) in a targeted manner according to actual needs to achieve enhanced drying of the sludge on the conveyor belt 2.

9. The dedicated device for sludge reduction treatment according to claim 1, characterized in that: The overall efficiency of the dehumidifying heat pump is 700%.

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