Sludge hot-pressing dehydration method

Abstract

The invention discloses a sludge hot-pressing dehydration method which comprises the following steps: 1) loading quantitative sludge into a mold: weighing a certain amount of sludge, wrapping the sludge with filter cloth, and putting the wrapped sludge into the mold; 2) hot-pressing dehydration: after a hot press is preheated, putting the mold filled with the sludge into the hot press, and dehydrating by controlling the temperature, the pressure and the hot-pressing time; wherein the thickness of a sludge material layer in the mold is 5-34 mm, the temperature is 90-130 DEG C, the pressure is 1-9 MPa, and the hot pressing time is 30 min or above; and (3) sludge demoulding and water testing: stopping the hot press, opening the mould, taking out the sludge, and testing the water content of the sludge, and meanwhile, the invention discloses equipment for implementing the method. The sludge dewatering speed is high, energy consumption is low, the limit of traditional mechanical dewatering can be broken through, and deep sludge dewatering is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge dehydration and drying, and particularly relates to a sludge hot-pressing dehydration method. Background Art

[0002] Sludge is a byproduct of the sewage treatment process. It is large in volume, high in water content, and contains a large amount of organic matter and heavy metals. The water content of sludge treated by the sewage treatment plant is as high as 80%-85%. The high water content of these sludges increases the transportation cost. In addition, the sludge contains a large amount of organic matter and rich nutrients such as nitrogen, phosphorus and potassium. If it is not handled properly, it is very easy to cause secondary pollution.

[0003] Mechanical dehydration is the main method of sludge dehydration in my country. Mechanical dehydration refers to the use of mechanical equipment to remove water from sludge by physical methods. Traditional mechanical dehydration mainly removes free water and part of capillary water in sludge. Commonly used mechanical dehydration methods include vacuum filtration, filter press, centrifugal and belt press filtration. For municipal sludge, the moisture content of sludge after dehydration by centrifuge and belt filter is 75%-80%, and the moisture content of sludge after dehydration by diaphragm plate and frame filter press is about 60%.

[0004] Chinese patent CN105800891A discloses a sewage sludge dehydration method that couples electroosmosis with mechanical filter pressing. In an alternating voltage dehydration mode, the sludge is dehydrated by adjusting the power supply of the anode plate and the cathode plate, so that the moisture content of the dehydrated sludge is reduced to below 50%.

[0005] Chinese patent CN114772892A discloses a sludge dehydration method using low-pressure hot air segmented filter press blowing, which combines air filter press technology with a skeleton net to cut and split the sludge, and then quickly blows the inside of the sludge filter cake with hot air to quickly dehydrate the sludge, reducing the moisture content of the dehydrated sludge to 57.03%.

[0006] Chinese patent CN103206844A discloses a method for hot pressing and drying dehydration of highly water-containing viscous and non-viscous wet materials. The patent mentions the hot pressing temperature and pressure, but does not disclose the correlation between process parameters such as temperature and pressure, material layer thickness, and hot pressing time, nor does it mention the moisture content of the material after hot pressing.

[0007] In 2010, Duan Xiaoren, a master's thesis at Soochow University, was titled "Research on the Mechanism of High-Dryness Dehydration of Domestic Sludge by Hot-Pressure Filtration". The thesis used steam to fill the membrane of a diaphragm filter press to achieve hot-pressed sludge dehydration, and concluded that "the economical and efficient process parameters of the activated sludge steam heating and mechanical pressing composite process are: heating temperature between (135°C and 145°C), dehydration time between (25 and 30 minutes), pressing force (0.6 to 1.0 MPa), and the sludge water content dropped from 92.5% to 58.5%."

[0008] Due to the presence of intracellular water in sludge, mechanical dehydration has a limit to solid-liquid separation. Most of the existing pressing dehydration and hot pressing dehydration technologies can only reduce the sludge moisture from 80-85% to 50-60%, which cannot meet the needs of deep sludge dehydration. Summary of the invention

[0009] The object of the present invention is to provide a sludge hot-pressing dehydration method, which has a fast sludge dehydration speed and low energy consumption, can break through the limit of traditional mechanical dehydration and achieve deep sludge dehydration.

[0010] To achieve the above object, the present invention provides a sludge hot-pressing dehydration method, comprising the following steps:

[0011] 1) Loading a certain amount of sludge into the mold: Weigh a certain amount of sludge, wrap it with filter cloth and put it into the mold;

[0012] 2) Hot pressing dehydration: After the hot press is preheated, the mold containing the sludge is placed in the hot press, and the temperature, pressure and hot pressing time are controlled for dehydration;

[0013] The thickness of the sludge layer in the mold is 5-34mm, the temperature is 90-130℃, the pressure is 1-9MPa, and the hot pressing time is more than 30min;

[0014] 3) Demolding and testing the water content of sludge: Stop the hot press, open the mold, take out the sludge, and test its moisture content.

[0015] As a further solution of the present invention: the material layer thickness is 20-30 mm, the temperature is 120-130° C., the pressure is 6-9 MPa, and the hot pressing time is 45-60 min.

[0016] As a further solution of the present invention: the material layer thickness is 10-20 mm, the temperature is 120-130° C., the pressure is 6-9 MPa, and the hot pressing time is 60-90 min.

[0017] As a further solution of the present invention: the material layer thickness is 5-10 mm, the temperature is 90-110° C., the pressure is 1-5 MPa, and the hot pressing time is more than 90 min.

[0018] To achieve the above object, the present invention also provides a sludge hot-pressing dehydration device, comprising:

[0019] A hot press is used to heat and pressurize the sludge, including a hydraulic mechanism and an upper hot press plate and a lower hot press plate with electric heating, and the hydraulic structure drives and controls the upper hot press plate and the lower hot press plate;

[0020] A controller, used to control the temperature and pressure of the upper hot pressing plate and the lower hot pressing plate;

[0021] The mold is located between the upper hot pressing plate and the lower hot pressing plate and is used to load the wrapped sludge.

[0022] As a further solution of the present invention: the mold includes a lower pressing plate and a lower pressing plate, a frame and a permeable screen plate are connected above the lower pressing plate, the permeable screen plate is located inside the frame, and the upper pressing plate is located above the permeable screen plate, and the size of the upper pressing plate matches the inner diameter of the frame.

[0023] As a further solution of the present invention: grooves for inserting the frame are provided around the upper surface of the upper pressing plate, and a plurality of vertical water outlet holes are provided on the inner side of the grooves on the upper surface of the upper pressing plate.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The deep dehydration of sludge is achieved by coupling heat and pressure and coordinating multiple parameters such as temperature, pressure, material layer thickness, and hot pressing time. This method breaks through the limits of traditional mechanical dehydration and achieves deep dehydration of sludge.

[0026] It realizes the combination of pressing dehydration and thermal drying dehydration. The equipment occupies a small space and requires little investment. In addition, the sludge dehydration speed is fast, the energy consumption is low, and the cost is low.

[0027] The use of molds can also avoid dust pollution caused by thermal drying and dehydration. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the sludge hot-pressing dehydration method of the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of the sludge hot-pressing dehydration equipment of the present invention;

[0030] Figure 3 It is the moisture content diagram of the sludge under different pressure conditions of the present invention;

[0031] Figure 4 The figure is the moisture content diagram of the sludge under different hot pressing time of the present invention;

[0032] Figure 5 It is the moisture content diagram of the sludge under different temperature conditions of the present invention;

[0033] Figure 6 It is the moisture content diagram of sludge under different material amounts of the present invention;

[0034] Figure 2 Middle: 1. Upper hot pressing plate, 2. Lower hot pressing plate, 3. Hydraulic mechanism, 4. Controller, 5. Upper pressing plate, 6. Frame, 7. Filter cloth, 8. Sludge, 9. Permeable screen plate, 10. Lower pressing plate, 11. Vertical water outlet. DETAILED DESCRIPTION

[0035] The present invention will be further described below by way of examples.

[0036] like Figure 1 As shown, a sludge hot pressure dehydration method comprises the following steps:

[0037] 1) Loading a certain amount of sludge 8 into the mold: Weigh a certain amount of sludge 8, wrap it with filter cloth 7 and put it into the mold;

[0038] 2) Hot pressing dehydration: After the hot press is preheated, the mold containing the sludge 8 is placed in the hot press, and the temperature, pressure and hot pressing time are controlled for dehydration;

[0039] The thickness of the sludge 8 material layer in the mold is 5-34mm, the temperature is 90-130℃, the pressure is 1-9MPa, and the hot pressing time is more than 30min;

[0040] 3) Demolding and testing the moisture content of the sludge 8: Stop the hot press, open the mold, take out the sludge 8, and test its moisture content. Weigh the hot-pressed sludge 8 and put it into a constant temperature blast drying oven to measure the moisture content of the hot-pressed sludge 8 by weight method.

[0041] The hot pressing dehydration rate of sludge 8 is closely related to the process parameters such as the hot pressing plate temperature (the temperature of the upper hot pressing plate 1 and the lower hot pressing plate 2), the hot pressing plate pressure (the pressure between the upper hot pressing plate 1 and the lower hot pressing plate 2), the sludge 8 material layer thickness, and the hot pressing time. This requires determining the above process parameters based on comprehensive factors such as the sludge 8 treatment scale, dehydration energy consumption, equipment investment, and production cost.

[0042] For large-scale sludge dehydration with a daily treatment capacity of more than 100 tons, if a higher dehydration rate of more than 70% is desired, a high temperature, high pressure and thick material layer short time dehydration strategy should be adopted. Furthermore, the material layer thickness is 20-30mm, the temperature is 120-130℃, the pressure is 6-9MPa, and the hot pressing time is 45-60min.

[0043] For small-scale sludge dehydration with a daily processing capacity of less than 100 tons, if a higher dehydration rate of more than 70% is desired, a high temperature, high pressure and thin material layer long time dehydration strategy should be adopted. Furthermore, the material layer thickness is 10-20mm, the temperature is 120-130℃, the pressure is 6-9MPa, and the hot pressing time is 60-90min.

[0044] If low investment, low cost and high dehydration rate are the main goals of sludge 8 dehydration, a low temperature, low pressure and thin material layer long time dehydration strategy should be adopted. Furthermore, the material layer thickness is 5-10mm, the temperature is 90-110℃, the pressure is 1-5MPa, and the hot pressing time is more than 90min.

[0045] like Figure 2 As shown, a sludge hot-pressing dehydration device comprises:

[0046] A hot press, used for heating and pressurizing the sludge 8, comprises a hydraulic mechanism 3 and an upper hot press plate 1 and a lower hot press plate 2 with electric heating, wherein the hydraulic structure drives and controls the upper hot press plate 1 and the lower hot press plate 2;

[0047] The controller 4 is used to control the temperature and pressure of the upper hot pressing plate 1 and the lower hot pressing plate 2; the temperature range of the upper hot pressing plate 1 and the lower hot pressing plate 2 is from room temperature to 200°C, and the pressure between the upper hot pressing plate 1 and the lower hot pressing plate 2 is from room temperature to 11MPa;

[0048] The mold is located between the upper hot pressing plate 1 and the lower hot pressing plate 2 and is used for loading the wrapped sludge 8 .

[0049] In order to improve the dehydration effect, the mold further includes a lower pressing plate 10 and a lower pressing plate 10, and a frame 6 and a permeable screen plate 9 are connected above the lower pressing plate 10, the permeable screen plate 9 is located inside the frame 6, and the upper pressing plate 5 is located above the permeable screen plate 9, and the size of the upper pressing plate 5 matches the inner diameter of the frame 6.

[0050] Furthermore, grooves for inserting the frame 6 are provided around the upper surface of the upper pressing plate 5 , and a plurality of vertical water outlet holes 11 are provided on the inner side of the grooves on the upper surface of the upper pressing plate 5 , which can facilitate the assembly and drainage of the mold.

[0051] Example 1: The temperature of the hot press is preheated to 130°C and the pressure is set to 1 MPa; 8800 g of the sludge with a moisture content of 84.24% is taken, the sludge 8 is wrapped with filter cloth 7 and placed on the permeable screen plate 9 of the mold and in the frame 6, the filter cloth 7 is folded inward along the inner wall of the frame 6 so that the filter cloth 7 completely wraps the sludge 8, and the thickness of the sludge layer 8 is measured; then the mold is placed on the hot press, the hot press is started, and the hot press is performed for 30 minutes. After the hot pressing is completed, the sludge 8 is taken out and the thickness and moisture content of the sludge 8 after filtration are measured.

[0052] In Example 2-17, the sludge 8 was hot pressed according to the method of Example 1. The specific conditions are listed in Table 1.

[0053] According to the industry standard "GJ / T 221-2005 Urban Sewage Treatment Plant Sludge Testing Method" the moisture content of the hot pressed sludge 8 of Example 1-17 was tested, and the results are shown in Figures 3 to 6 And Table 1.

[0054] Table 1 Sludge hot pressing parameters and dehydration data of Examples 1-17.

[0055]

[0056] In all the above embodiments, the size of the upper pressure plate 5 in the mold used is 200ⅹ200ⅹ15mm, the size of the frame 6 is 200ⅹ200ⅹ50mm, the size of the lower pressure plate 10 is 220ⅹ220ⅹ20mm, the size of the permeable screen plate 9 is 200ⅹ200ⅹ3mm, the filter cloth 7 used is made of polypropylene, has a thickness of 0.9mm, and a filter hole diameter of 400 meshes. The sludge 8 used comes from a sewage treatment plant in Xuzhou.

[0057] The method provided by the present invention is used to dehydrate the sludge 8, wherein the hot pressing temperature is 90-130°C, the pressure is 1-9MPa, the hot pressing time is 30-90min, the material layer thickness is 12-34mm, and the mass of the sludge 8 is 400-1200g. The sludge 8 containing 84.24% of water can be dehydrated to between 4.33% and 61.51%. The moisture content of the hot-pressed sludge 8 is much lower than that of mechanical dehydration, and the time used for dehydration is shorter and the water loss rate is faster than that of thermal drying dehydration.

[0058] Principle of the present invention: The sludge 8 is simultaneously subjected to the upper and lower squeezing forces and the heat transferred from the outside to the inside. The squeezing force promotes the extrusion of the free water between the cells of the sludge 8, while the heat promotes the removal of the water inside the cells of the sludge 8. The squeezing force and the heat work together to remove the water inside and between the cells of the sludge 8, thereby achieving deep dehydration of the sludge 8. That is, under the action of the squeezing force, the free water between the cells in the sludge 8 first penetrates the material layer, escapes from the gaps between the cells, and finally flows out from the vertical water outlet 11 of the mold; the heat is transferred from the upper hot pressing plate 1 and the lower hot pressing plate 2 to the cell wall of the sludge 8 through the upper pressing plate 5 and the lower pressing plate 10 of the mold, and heats the water inside the cell wall of the sludge 8. After being heated, the water inside the cell wall begins to vaporize, and the volume expands rapidly, and finally breaks through the cell wall, escapes from the gaps between the cells and the vertical water outlet 11 of the mold, completing the deep dehydration of the sludge 8.

Claims

1. A method for hot-pressing dehydration of sludge, characterized in that: The following steps are involved: 1) Loading a certain amount of sludge (8) into a mold: weigh a certain amount of sludge (8), wrap it with filter cloth (7) and put it into a mold; 2) Hot pressing dehydration: After the hot press is preheated, the mold containing the sludge (8) is placed in the hot press, and the temperature, pressure and hot pressing time are controlled to perform dehydration; The thickness of the sludge (8) layer in the mold is 5-34 mm, the temperature is 90-130° C., the pressure is 1-9 MPa, and the hot pressing time is more than 30 min; 3) Demolding the sludge (8) and testing its water content: stop the hot press, open the mold, take out the sludge (8), and test its water content.

2. A sludge hot-pressing dehydration method according to claim 1, characterized in that: The material layer thickness is 20-30mm, the temperature is 120-130℃, the pressure is 6-9MPa, and the hot pressing time is 45-60min.

3. A sludge hot-pressing dehydration method according to claim 1, characterized in that: The material layer thickness is 10-20 mm, the temperature is 120-130°C, the pressure is 6-9 MPa, and the hot pressing time is 60-90 min.

4. A sludge hot-pressing dehydration method according to claim 1, characterized in that: The material layer thickness is 5-10mm, the temperature is 90-110°C, the pressure is 1-5MPa, and the hot pressing time is more than 90min.

5. A sludge hot-pressing dehydration device, characterized in that: include: A hot press, used for heating and pressurizing sludge (8), comprising a hydraulic mechanism (3) and an upper hot press plate (1) and a lower hot press plate (2) with electric heating, wherein the hydraulic structure drives and controls the upper hot press plate (1) and the lower hot press plate (2); A controller (4) for controlling the temperature and pressure of the upper hot pressing plate (1) and the lower hot pressing plate (2); The mold is located between the upper hot pressing plate (1) and the lower hot pressing plate (2) and is used to load the wrapped sludge (8).

6. The sludge hot-pressing dehydration equipment according to claim 5, characterized in that: The mold comprises a lower pressing plate (10) and a lower pressing plate (10), a frame (6) and a water-permeable screen plate (9) are connected above the lower pressing plate (10), the water-permeable screen plate (9) is located inside the frame (6), and an upper pressing plate (5) is located above the water-permeable screen plate (9), and the size of the upper pressing plate (5) matches the inner diameter of the frame (6).

7. The sludge hot-pressing dehydration equipment according to claim 6, characterized in that: The upper surface of the upper pressing plate (5) is provided with grooves for inserting the frame (6) around its periphery, and the upper surface of the upper pressing plate (5) is provided with a plurality of vertical water outlet holes (11) located inside the grooves.

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