An iron-enhanced anaerobic digestion device for waste aluminum activated sludge

Abstract

The present invention relates to the technical field of sludge treatment, and in particular to an iron-reinforced anaerobic digestion device for waste aluminum activated sludge. The device comprises a closed digestion tank, a discharge port is provided at the lower end of the digestion tank, an exhaust port and a feed port are provided at the upper end, an electrode rod is inserted into the digestion tank, the anode rod is made of iron, and the cathode rod is made of carbon, the anode rod is energized to generate ferrous ions, and the remaining air in the digestion tank oxidizes the ferrous ions into trivalent ferrous ions, and a partition is provided inside the digestion tank, the partition is provided with a through hole and the partition divides the digestion tank into an upper chamber and a lower chamber connected to each other, limestone is accumulated on the partition, and the temperature of the upper chamber is higher than that of the lower chamber; the present invention utilizes the ferrous ions generated by the electrolytic anode rod to consume oxygen in anaerobic conditions and be oxidized into trivalent ferrous ions, the ferric ions can, on the one hand, break down the dense physical structure of the aluminum-containing sludge and ensure effective contact between microorganisms and the sludge, and on the other hand, reduce the reaction potential energy on the sludge surface, which is conducive to the progress of biochemical reactions.

Description

Technical Field

[0001] The present invention relates to the technical field of sludge treatment, in particular to an iron-reinforced waste aluminum activated sludge anaerobic digestion device. Background Art

[0002] The water purification process used in sewage treatment plants and waterworks first involves adding a flocculant through a flocculation device to cause coagulation. After a certain period of time, the coagulated material is allowed to settle, thereby achieving the purpose of removing large particles of impurities and organic matter. Polyaluminium chloride has become a recognized excellent water purifier both domestically and internationally due to its outstanding characteristics and wide range of applications. However, this process produces a large amount of aluminium-containing activated sludge. This sludge contains suspended solids from the raw water, clay, organic matter such as humic acid, microorganisms, hydroxides formed by the hydrolysis of aluminium salt coagulants, coagulants, and substances introduced into other water treatment units such as powdered activated carbon. However, due to the strong agglomeration of the coagulant, the structure of the aluminium-containing sludge is dense, and the reaction potential energy of the interfacial reaction is also high, which is not conducive to biological treatment.

[0003] At present, most of the scrap aluminum sludge is regarded as waste and is eventually dehydrated and landfilled. However, sanitary landfill is a relatively passive treatment method after all. The permeability of pollutants and the concentration of heavy metals are particularly important factors affecting the soil ecological environment. In addition, the landfill site is far away from the city, and transporting sludge will incur high costs. At the same time, it is not easy to manage and control the landfill site, which will eventually damage the surrounding soil environment and the available resources cannot be fully utilized. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in order to overcome the problem of landfill treatment of waste aluminum sludge in the prior art, which causes damage to the soil environment, an iron-enhanced waste aluminum activated sludge anaerobic digestion device is provided, which can simultaneously achieve rapid anaerobic digestion of waste aluminum sludge and recovery and utilization of methane.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: an iron-enhanced waste aluminum activated sludge anaerobic digestion device, comprising a closed digestion tank, wherein the digestion tank is provided with a discharge port at the lower end and an exhaust port and a feed port at the upper end;

[0006] Multiple sets of electrode rods are inserted into the digester. The anode rods are made of iron and the cathode rods are made of carbon. When the anode rods are energized, ferrous ions are generated. The remaining air in the digester oxidizes the ferrous ions into ferric ions, thereby consuming the air and forming an anaerobic environment inside the digester.

[0007] A partition is provided inside the digester, which is provided with a through hole and divides the digester into an upper chamber and a lower chamber that are connected to each other. Limestone is piled on the partition, and the temperature of the upper chamber is higher than that of the lower chamber. The upper chamber forms a high-temperature digestion area for maturing organic matter, and the lower chamber forms a medium-temperature digestion area for degrading organic matter.

[0008] During operation, first determine the carbon-nitrogen ratio and nutrient concentration of the waste aluminum sludge to ensure that the nutrient concentration of the sludge added to the digester is within the appropriate range, close the discharge port, open the sealing cover of the feed port and add the waste aluminum sludge into the digester, and at the same time apply current to the electrode rod. After the current is applied, the anode produces ferrous ions, which are oxidized into trivalent ferrous ions by the remaining air in the digester. The trivalent ferrous ions can destroy the tight physical structure of the aluminum flocculant sludge, exposing more binding sites with anaerobic bacteria and promoting the biochemical reaction: On the other hand, the addition of trivalent ferrous ions can significantly reduce the reaction potential energy of the sludge surface, change the Gibbs potential energy from positive to negative, and make the reaction proceed in the direction of products with lower free energy, providing energy conditions for the reaction: In addition, trivalent ferrous ions are also beneficial to the release of hydrophobic functional groups on the sludge surface, so that more hydrophobic sites appear on the sludge surface, thereby changing from hydrophilic to hydrophobic, which is beneficial to the subsequent sludge dehydration. By applying an appropriate direct current microcurrent, the intracellular protein content of bacteria can be increased and the activity of cellular ATPase can be enhanced, which can improve the metabolic capacity of cells to a certain extent and reduce energy consumption. The high-temperature environment formed in the upper chamber can make methanogens grow rapidly, and due to the full action of the high-temperature microorganisms above, the organic matter is rapidly matured, and then the acidity of the sludge is adjusted through the neutralization effect of the limestone interlayer, and then enters the medium-temperature digestion area of ​​the lower chamber. Due to the high-temperature maturation above (killing insect eggs and pathogenic bacteria, and decomposing large molecules into small molecules) and the effect of limestone on pH adjustment, the microorganisms in the medium-temperature digestion area of ​​the lower chamber can quickly start the decomposition and gas production process. The methane produced is connected to the methane collection device from the exhaust port, and the sludge discharged from the lower discharge port enters the dehydration system for the next dehydration treatment.

[0009] The above technical solution uses the ferrous ions produced by the electrolytic anode rod to consume oxygen in the anaerobic environment and be oxidized into trivalent ferrous ions. On the one hand, the ferrous ions can break down the dense physical structure of the aluminum-containing sludge, ensuring effective contact between microorganisms and the sludge. On the other hand, they can reduce the reaction potential energy on the sludge surface, which is conducive to the progress of biochemical reactions.

[0010] Furthermore, the temperature of the upper chamber is set to 45-55°C, and the temperature of the lower chamber is set to 33-37°C.

[0011] Furthermore, the upper and lower chambers are both equipped with heat exchangers for adjusting the temperature in the chamber and temperature sensors for monitoring the temperature in the chamber. The temperature sensors monitor the temperature in the chamber, and the heat exchangers adjust the temperature in the chamber according to the monitoring results of the temperature sensors to control the reaction speed in the digester.

[0012] Furthermore, an agitator is provided inside the digester, and the agitator includes at least two stirring blades. Both the upper chamber and the lower chamber have stirring blades. After the waste aluminum sludge is added into the digester, the agitator is started, and the stirring blades in the upper chamber and the stirring blades in the lower chamber stir the materials in the chamber evenly.

[0013] Furthermore, the volume of the lower chamber is 3-6 times that of the upper chamber, and the two chambers form a volume difference, so the residence time of the sludge in the lower chamber is 3-6 times that of the upper chamber.

[0014] Furthermore, the digester is made of stainless steel, and its inner wall is coated with a resin anti-corrosion layer, thereby improving the corrosion resistance of the digester and extending its service life.

[0015] The beneficial effects of the present invention are:

[0016] 1. The ferrous ions produced by the electrolytic anode can consume oxygen in the anaerobic environment and be oxidized into trivalent ferric ions. On the one hand, the ferric ions can break down the dense physical structure of the aluminum-containing sludge and ensure effective contact between microorganisms and sludge; on the other hand, they can reduce the reaction potential energy on the sludge surface, which is conducive to the biochemical reaction.

[0017] 2. Microcurrent can promote the metabolism and proliferation of anaerobic bacteria, thereby accelerating the degradation and transformation of organic matter and significantly increasing biomethane production.

[0018] 3. The aluminum-containing sludge treated by this device will change from hydrophilic to hydrophobic, which is beneficial to subsequent dehydration treatment.

[0019] 4. This device is equipped with a heat exchange device, which can effectively control the digestion temperature and improve the processing efficiency.

[0020] 5. The series design of high-temperature digestion followed by medium-temperature digestion saves energy, shortens digestion time, and realizes continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings and examples.

[0022] Figure 1 It is a structural schematic diagram of the present invention;

[0023] In the picture:

[0024] 1. Digester; 101. Discharge port; 102. Exhaust port; 103. Feed port; 104. Upper chamber; 105. Lower chamber; 2. Anode rod; 3. Cathode rod; 4. Partition; 5. Limestone; 6. Heat exchanger; 7. Temperature sensor; 8. Agitator; 801. Mixing blades; 802. Motor; 9. Base. DETAILED DESCRIPTION

[0025] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating the basic structure of the present invention only in a schematic manner. Therefore, they only show components relevant to the present invention, and directions and references such as up, down, left, right, etc., are merely used to facilitate the description of features in the drawings. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the claimed subject matter is defined solely by the appended claims and their equivalents.

[0026] Example 1:

[0027] like Figure 1 As shown, the present invention is an iron-reinforced anaerobic digestion device for waste aluminum activated sludge, comprising: a closed digestion tank 1, which is made of 304 stainless steel and has an inner wall coated with a resin anti-corrosion layer; the digestion tank 1 is supported by a base 9, a discharge port 101 is provided at the lower end thereof, an exhaust port 102 and a feed port 103 are provided at the upper end thereof, and the feed port 103 is provided with a sealing cover;

[0028] A partition 4 is provided inside the digester 1. The partition 4 is provided with a through hole and the partition 4 divides the digester 1 into an upper chamber 104 and a lower chamber 105 that are connected to each other. The volume of the lower chamber 105 is 3-6 times the volume of the upper chamber 104. The two chambers form a volume difference, so the residence time of the sludge in the lower chamber 105 is 3-6 times the residence time of the upper chamber 104. Limestone 5 is piled on the partition 4 with a pile height of 20-40 cm. The temperature of the upper chamber 104 is higher than that of the lower chamber 105. The upper chamber 104 forms a high-temperature digestion area for maturation of organic matter, and the lower chamber 105 forms a medium-temperature digestion area for degradation of organic matter. The temperature of the upper chamber 104 is set to 45-55°C, and the temperature of the lower chamber 105 is set to 33°C-37°C.

[0029] A plurality of electrode rods are inserted into the digester 1, and the electrode rods extend from the upper chamber 104 to the bottom of the lower chamber 105. The anode rod 2 is made of iron and the cathode rod 3 is made of carbon. When the anode rod 2 is energized, ferrous ions are generated. The remaining air in the digester 1 oxidizes the ferrous ions into ferric ions, thereby consuming the air to form an anaerobic environment inside the digester 1.

[0030] A stirrer 8 is provided at the center of the inner cavity of the digester 1, and multiple groups of electrode rods are located on the periphery of the stirrer 8 and distributed in a circle. The stirrer 8 includes a variable frequency speed regulation motor 802 located at the top of the digester 1, a stirring shaft connected to the motor shaft, and at least two stirring blades 801 fixed on the stirring shaft. The stirring blades 801 are both provided inside the upper cavity 104 and the lower cavity 105. A mechanical seal is used between the stirring shaft and the digester 1. After the waste aluminum sludge is added to the digester 1, the stirrer 8 is started, and the stirring blades 801 in the upper cavity 104 and the stirring blades 801 in the lower cavity 105 stir the materials in the cavity evenly.

[0031] The upper chamber 104 and the lower chamber 105 are both equipped with a heat exchanger 6 for adjusting the temperature in the chamber and a temperature sensor 7 for detecting the temperature in the chamber. The temperature sensor 7 monitors the temperature in the chamber, and the heat exchanger 6 adjusts the temperature in the chamber according to the monitoring results of the temperature sensor 7 to control the reaction speed in the digester 1.

[0032] Working principle:

[0033] During operation, first determine the carbon-nitrogen ratio and nutrient concentration of the waste aluminum sludge to ensure that the nutrient concentration of the sludge added to the digester 1 is within the appropriate range, close the discharge port 101, open the sealing cover of the feed port 103 and add the waste aluminum sludge into the digester 1, start the stirrer 8 to stir the material evenly, and control the speed of the stirrer 8 at 150-200 rpm / min. At the same time, the stirring blade 801 is controlled by the PLC to adjust the forward and reverse rotation every 10 minutes to stir it evenly. If the solid content in the digester 1 is high, it can be operated continuously, and if the solid content is low, it can be operated intermittently. At the same time, a current of 25 mA is applied to the electrode rod, and the stirring blade 801 is applied. After the current is applied, the anode produces ferrous ions, which are oxidized to ferric ions by the remaining air in digester 1. The ferric ions can disrupt the tight physical structure of the aluminum flocculant sludge, exposing more binding sites for anaerobic bacteria and promoting the biochemical reaction. Furthermore, the addition of ferric ions can significantly reduce the reaction potential energy on the sludge surface, changing the Gibbs potential from positive to negative, and directing the reaction toward the product with lower free energy, thus providing the energy conditions for the reaction. Furthermore, ferric ions facilitate the release of hydrophobic functional groups on the sludge surface, creating more hydrophobic sites on the sludge surface, thereby converting the hydrophilic to hydrophobic surface and facilitating subsequent sludge dehydration. Applying an appropriate amount of direct current can increase the intracellular protein content of bacteria and enhance the activity of cellular ATPase, which can improve the metabolic capacity of the cells to a certain extent while also reducing energy consumption. The sludge temperature in the digester 1 is monitored by the temperature sensor 7. The temperature of the upper chamber 104 is set to 45-55°C, and the temperature of the lower chamber 105 is set to 33-37°C. When the temperature is higher or lower, the heat exchanger 6 can be used for circulating cooling or heating to ensure the appropriate temperature. The high temperature environment formed by the upper chamber 104 can make methanogens grow rapidly. After starting and running for 10-20 days, the bottom discharge port 12 is opened to form a continuous operation process. The sludge stays in the high temperature area of ​​the upper chamber 104 for 2-5 days, and stays in the lower chamber 105 for about 3-6 times that of the upper chamber, which varies according to the volume ratio of the upper and lower parts, thereby forming a continuous process. During the operation, due to the full action of the high-temperature microorganisms in the upper chamber 104, the organic matter is rapidly matured, and then the acidity of the sludge is adjusted through the neutralization effect of the limestone 5 interlayer, and then enters the medium-temperature digestion area of ​​the lower chamber 105. Due to the high-temperature maturation above (killing insect eggs and pathogenic bacteria, and decomposing large molecules into small molecules) and the pH adjustment effect of the limestone 5, the medium-temperature part of the microorganisms in the lower chamber 105 can quickly start the decomposition and gas production process, saving energy and time, and realizing continuous production. The generated methane is connected to the methane collection device from the exhaust port 102, and the sludge discharged from the lower discharge port 101 enters the dehydration system for the next dehydration treatment.

[0034] The above description of the preferred embodiments of the present invention is intended to serve as a guide. Based on the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. An iron-enhanced anaerobic digestion device for waste aluminum activated sludge, characterized by: It comprises a sealed digester (1), wherein the digester (1) is provided with a discharge port (101) at the lower end, and an exhaust port (102) and a feed port (103) at the upper end; A plurality of electrode rods are inserted into the digestion tank (1), wherein the anode rod (2) is made of iron and the cathode rod (3) is made of carbon. When the anode rod (2) is energized, ferrous ions are generated, and the remaining air in the digestion tank (1) oxidizes the ferrous ions into ferric ions. A partition (4) is provided in the digestion tank (1), the partition (4) having a through hole and dividing the digestion tank (1) into an upper chamber (104) and a lower chamber (105) that are connected to each other. Limestone (5) is deposited on the partition (4), and the temperature of the upper chamber (104) is higher than that of the lower chamber (105). The upper chamber (104) forms a high-temperature digestion area for maturation of organic matter, and the lower chamber (105) forms a medium-temperature digestion area for degradation of organic matter. The temperature of the upper chamber (104) is set to 45°C-55°C, and the temperature of the lower chamber (105) is set to 33°C-37°C; A heat exchanger (6) for regulating the temperature in the cavity and a temperature sensor (7) for monitoring the temperature in the cavity are installed in both the upper cavity (104) and the lower cavity (105); An agitator (8) is provided inside the digestion tank (1), and the agitator (8) comprises at least two agitating blades (801). The agitating blades (801) are both provided inside the upper chamber (104) and the lower chamber (105).

2. The iron-enhanced anaerobic digestion device for waste aluminum activated sludge according to claim 1, characterized in that: The volume of the lower chamber (105) is 3-6 times the volume of the upper chamber (104).

3. The iron-enhanced anaerobic digestion device for waste aluminum activated sludge according to claim 1, characterized in that: The digestion tank (1) is made of stainless steel, and its inner wall is coated with a resin anti-corrosion layer.

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