Low-temperature closed circulating sludge drying equipment and method

Abstract

The invention discloses low-temperature closed circulating sludge drying equipment and belongs to the technical field of sludge treatment equipment. The equipment comprises a drying room, a liquid circulating system and a gaseous circulating system which are arranged in a machine shell, the low-temperature closed circulating sludge drying method is characterized in that heat exchange is carried out through the gaseous circulating system and the liquid circulating system, finally, high-temperature low-speed dry air is formed and enters a drying bin, and the dry air absorbs moisture in sludge in the rising process to dry the sludge. Drying equipment is a closed system, so that pollution to the environment is avoided, and emission of malodorous gas is avoided; the gas-state circulating system and the liquid-state circulating system conduct heat transfer mutually, the fastest evaporation speed is obtained with the minimum heat and the minimum air volume, and the energy-saving and efficient drying effect is achieved. Air countercurrent is beneficial to moisture absorption of dry air until the dry air is saturated; the sludge with higher water content has dust absorption performance, and the sludge with different feeding water contents can be self-adapted to the working condition change of the sludge with different feeding water contents through different speed adjustment of each layer; and through low-speed breeze and reverse flow conveying, no dust is brought out in the drying process.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment equipment, and in particular relates to low-temperature closed-cycle sludge drying equipment. Background Art

[0002] The mud quality of sludge has a great influence on sludge treatment, and the moisture content of wet sludge directly affects the stability and economy of the sludge treatment system. The higher the moisture content of the sludge, the greater the energy consumption of sludge treatment. The high moisture content affects the sludge drying operation. In the prior art, sludge drying mostly uses steam or hot air for heating, and the energy consumption accounts for 70% of the total energy consumption of the entire drying process. However, the drying technology currently used in China does not recycle the process heat energy or has a low recycling rate, does not achieve the recycling of heat energy, and has a high unit drying energy consumption index. A Chinese patent with a publication number of CN113955915B discloses a sludge low-temperature drying system and drying method, including a noodle machine, a first closed drying chamber and a drying jet device; but the energy consumption is still large, and dust is easily generated during the drying process, and the dust accumulated in the system needs to be cleaned regularly. Summary of the invention

[0003] The object of the present invention is to provide a sludge drying device and a drying method which are more energy-saving, environmentally friendly and less likely to generate dust.

[0004] The low-temperature closed-cycle sludge drying equipment is characterized by comprising a drying room, a liquid circulation system and a gas circulation system arranged in a casing, a crusher is arranged at the top entrance of the drying room, and a plurality of conveyor belts are arranged below the feed port. The conveyor belts are arranged in layers and the conveying direction of each layer of the conveyor belt is opposite to that of the upper layer of the conveyor belt. A discharge port is arranged at the end of each layer of the conveyor belt, and the discharge ports are opened alternately on the left and right. A baffle of the oblique conveyor belt is also arranged at the discharge port, and a discharge port is arranged below the discharge port of the bottom conveyor belt. The liquid circulation system includes a fin evaporator, a compressor, a shell and tube heat exchanger and a heat recovery condenser connected in sequence through pipelines. The gas circulation system includes an air-to-air heat exchanger, a blower, two hot air pipes and two cold air pipes. The first cold air pipe is connected from the top of the drying room to the air inlet of the air-to-air heat exchanger, and the second cold air pipe is connected from the blower to the air pipe of the fin-type evaporator and then to the air-to-air heat exchanger. The first hot air pipe is connected from the air outlet of the air-to-air heat exchanger to the blower, and the second hot air pipe is connected from the air outlet of the air-to-air heat exchanger to the gas pipe of the heat recovery condenser. The gas circulation system and the liquid circulation system are arranged in the heat exchange bin. A partition is arranged between the heat exchange bin and the drying room. Openings are provided at the top and bottom of the partition. A dust filter is arranged at the top opening. The top of the drying room is connected to the air-to-air heat exchanger through an external air pipe.

[0005] The low-temperature closed-cycle sludge drying equipment exchanges heat through the gas circulation system and the liquid circulation system, and finally forms high-temperature and low-speed dry air that enters the drying chamber. During the rising process of the dry air, it absorbs the moisture in the sludge and dries it. The specific heat exchange process is as follows: The hot air with a temperature of 55-65℃ and a humidity of 10-20% dries the wet mud on the conveyor belt during its rising process in the drying room. At the same time, the heat is absorbed and cooled to a temperature of 35-40℃ and a humidity of 80-90%. The cold air enters the air-to-air heat exchanger through the first cold air duct, cools to a humidity of 31℃, and then is blown into the fin-type evaporator through the blower. It cools down to 20℃ and a humidity of 96% again and then enters the air-to-air heat exchanger. After heat exchange with the cold air sent into the drying room, the temperature reaches 22℃ and the humidity reaches 80%. It enters the heat recovery condenser, and after being heated and dehumidified by the heat recovery condenser, it becomes a return air with a temperature of 55-65℃ and a humidity of 10-20%, and then enters the bottom of the drying room, completing the gas cycle; In the liquid circulation system, the water output from the fin evaporator has a pressure of 4-6kg and a temperature of 20-25℃. It is transported to the compressor for pressurization and temperature increase to become high-pressure hot water with a pressure of 22-26kg and a temperature of 75-80℃. The high-pressure hot water passes through the shell and tube heat exchanger and then enters the heat recovery condenser to heat and dehumidify the gas with a temperature of 22℃ and a humidity of 80% input by the air-to-air heat exchanger. After the heat transfer, the water is cooled to 30-35℃ and then flows back to the fin evaporator to complete the liquid circulation.

[0006] The beneficial effects of the present invention are as follows: the drying equipment is a closed system, which will not pollute the environment and does not emit any foul-smelling gas; heat is transferred between the gas circulation system and the liquid circulation system to obtain the fastest evaporation rate with minimum heat and air volume, thereby achieving energy-saving and efficient drying effects; in the process of sludge falling from the first layer to the lowest conveyor belt, the moisture content decreases layer by layer, and the dry air flows from bottom to top, in the opposite direction of the sludge. Such a countercurrent is conducive to the moisture absorption of the dry air until it is saturated; the sludge with a higher moisture content has dust absorption performance, and can adapt to changes in the working conditions of sludge with different moisture contents of the feed by adjusting the speed of each layer; through low-speed breeze and reverse process transportation, no dust is brought out during the drying process.

[0007] Furthermore, an external heat exchanger is provided on the first cold air duct, and the external heat exchanger is connected to an external liquid cold source. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic diagram of the structure of the low-temperature closed-cycle sludge drying equipment in Example 1.

[0009] Figure 2 This is a schematic diagram of the structure of the low-temperature closed-cycle sludge drying equipment in Example 2.

[0010] Figure 3Schematic diagram of liquid cycle and gas cycle.

[0011] Among them: 1-crusher, 2-conveyor belt, 3-baffle, 4-discharge port, 5-wing evaporator, 6-compressor, 7-shell and tube heat exchanger, 8-heat recovery condenser, 9-air-to-air heat exchanger, 10-air blower, 11-first cold air duct, 12-second cold air duct, 13-first hot air duct, 14-second hot air duct, 15-partition, 16-dust filter, 17-external heat exchanger. DETAILED DESCRIPTION

[0012] Embodiment 1: Low-temperature closed-cycle sludge drying equipment, characterized in that it includes a drying room, a liquid circulation system and a gas circulation system arranged in a casing, a crusher 1 is provided at the top entrance of the drying room, and a plurality of conveyor belts 2 are provided below the feed port. The conveyor belts 2 are arranged in layers and the conveying direction of the conveyor belt 2 of each layer is opposite to that of the conveyor belt 2 of the upper layer. A discharge port is provided at the transmission end of each layer of the conveyor belt 2, and the discharge ports are opened alternately on the left and right. A baffle 3 for the oblique conveyor belt is also provided at the discharge port, and a discharge port 4 is provided below the discharge port of the bottom conveyor belt 2.

[0013] The liquid circulation system includes a fin-type evaporator 5, a compressor 6, a shell and tube heat exchanger 7 and a heat recovery condenser 8 which are sequentially connected through pipelines.

[0014] The gas circulation system includes an air-to-air heat exchanger 9, an air blower 10, two hot air pipes and two cold air pipes. The first cold air pipe 11 is connected to the air inlet of the air-to-air heat exchanger 9 from the top of the drying room, the second cold air pipe 12 is connected from the air blower 10 to the air pipe of the fin-type evaporator 5 and then connected to the air-to-air heat exchanger 9, the first hot air pipe 13 is connected to the air outlet of the air-to-air heat exchanger 9 to the air blower 10, and the second hot air pipe 14 is connected from the air outlet of the air-to-air heat exchanger 9 to the gas pipe of the heat recovery condenser 8.

[0015] The gas circulation system and the liquid circulation system are arranged in the heat exchange bin, and a partition 15 is arranged between the heat exchange bin and the drying room. The partition 15 has openings at the top and bottom, and a dust filter 16 is arranged at the top opening; the top of the drying room is connected to the air-to-air heat exchanger 9 through the external first cold air duct 11. When the outdoor temperature exceeds 30°C in summer, an external heat exchanger 17 is arranged on the first cold air duct 11, and the external heat exchanger 17 is connected to an external liquid cold source, which comes from wastewater, tap water and cooling tower, and the temperature is below 30°C.

[0016] The hot air with a temperature of 55-65°C and a humidity of 10-20% dries the wet mud on the conveyor belt 2 during its rising process in the drying room. At the same time, the heat is absorbed and cooled to a temperature of 35-40°C and a humidity of 80-90%. The cold air enters the air-to-air heat exchanger 9 from the first cold air duct 11, is cooled to a humidity of 31°C and 95%, and then is blown into the fin-type evaporator 5 through the blower, and is cooled to 20°C and 96% again before entering the air-to-air heat exchanger 9. After heat exchange with the cold air sent into the drying room, the temperature is 22°C and the humidity is 80%, and then enters the heat recovery condenser 8. After being heated and dehumidified by the heat recovery condenser 8, the return air becomes 55-65°C and a humidity of 10-20%, and then enters the bottom of the drying room to complete the gaseous cycle.

[0017] In the liquid circulation system, the water pressure output from the fin evaporator 5 is 4-6kg and the temperature is 20-25℃, which is transported to the compressor 6 for pressurization and temperature increase to become high-pressure hot water with a pressure of 22-26kg and a temperature of 75-80℃. The high-pressure hot water passes through the shell and tube heat exchanger 7 and then enters the heat recovery condenser 8 to heat and dehumidify the gas with a temperature of 22℃ and a humidity of 80% input by the air-to-air heat exchanger 9. After the heat transfer, the water is cooled to 30-35℃ and then flows back to the fin evaporator 5 to complete the liquid circulation.

[0018] The sludge falls from the first conveyor belt 2 to the bottom conveyor belt 2, and the dry air entering the drying room moves from bottom to top, in the opposite direction of the sludge. The dry air absorbs the moisture in the sludge until it is saturated, and finally the sludge falling into the bottom conveyor belt 2 is dried into dry mud and sent out from the discharge port.

[0019] Embodiment 2: The rest of this embodiment is the same as the embodiment 1. When the outdoor temperature is lower than 30°C, the external heat exchanger is removed or disabled, and the gas in the first cold air duct 11 is cooled by the external fresh air, thereby achieving a more energy-saving effect.

Claims

1. Low temperature closed cycle sludge drying equipment, characterized by: It includes a drying room, a liquid circulation system and a gas circulation system arranged in a casing. A crusher is arranged at the top entrance of the drying room. A plurality of conveyor belts are arranged below the feed port. The conveyor belts are arranged in layers and the conveying direction of each layer of conveyor belts is opposite to that of the upper layer of conveyor belts. A discharge port is arranged at the end of each layer of conveyor belts, and the discharge ports are opened alternately on the left and right. A baffle of the oblique conveyor belt is also arranged at the discharge port. A discharge port is arranged below the discharge port of the bottom conveyor belt. The liquid circulation system includes a fin-type evaporator, a compressor, a shell and tube heat exchanger and a heat recovery condenser which are sequentially connected through pipelines; The gas circulation system includes an air-to-air heat exchanger, an air blower, two hot air pipes and two cold air pipes. The first cold air pipe is connected from the top of the drying room to the air inlet of the air-to-air heat exchanger, the second cold air pipe is connected from the air blower to the air pipe of the fin-type evaporator and then connected to the air-to-air heat exchanger, the first hot air pipe is connected from the air outlet of the air-to-air heat exchanger to the air blower, and the second hot air pipe is connected from the air outlet of the air-to-air heat exchanger to the gas pipe of the heat recovery condenser; The gas circulation system and the liquid circulation system are arranged in the heat exchange bin. A partition is arranged between the heat exchange bin and the drying room. Openings are arranged at the top and bottom of the partition. A dust filter is arranged at the top opening. The top of the drying room is connected to the air-to-air heat exchanger through an external air pipe. The low-temperature closed-cycle sludge drying method is characterized in that: the low-temperature closed-cycle sludge drying equipment exchanges heat through a gas circulation system and a liquid circulation system, and finally forms high-temperature and low-speed dry air to enter the drying chamber. During the rising process of the dry air, the water in the sludge is absorbed to dry it. The specific heat exchange process is as follows: The hot air with a temperature of 55-65℃ and a humidity of 10-20% dries the wet mud on the conveyor belt during its rising process in the drying room. At the same time, the heat is absorbed and cooled to a temperature of 35-40℃ and a humidity of 80-90%. The cold air enters the air-to-air heat exchanger through the first cold air duct, cools to a humidity of 31℃, and then is blown into the fin-type evaporator through the blower. It cools down to 20℃ and a humidity of 96% again and then enters the air-to-air heat exchanger. After heat exchange with the cold air sent into the drying room, the temperature reaches 22℃ and the humidity reaches 80%. It enters the heat recovery condenser, and after being heated and dehumidified by the heat recovery condenser, it becomes a return air with a temperature of 55-65℃ and a humidity of 10-20%, and then enters the bottom of the drying room, completing the gas cycle; In the liquid circulation system, the water output from the fin evaporator has a pressure of 4-6kg and a temperature of 20-25℃. It is transported to the compressor for pressurization and temperature increase to become high-pressure hot water with a pressure of 22-26kg and a temperature of 75-80℃. The high-pressure hot water passes through the shell and tube heat exchanger and then enters the heat recovery condenser to heat and dehumidify the gas with a temperature of 22℃ and a humidity of 80% input by the air-to-air heat exchanger. After the heat transfer, the water is cooled to 30-35℃ and then flows back to the fin evaporator to complete the liquid circulation.

2. The low-temperature closed-cycle sludge drying equipment according to claim 1, characterized in that An external heat exchanger is arranged on the first cold air duct, and the external heat exchanger is connected to an external liquid cold source.

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