A biochemical sludge treatment method

Abstract

The present invention belongs to the field of environmental protection technology, and discloses a biochemical sludge treatment method. The biochemical sludge treatment method comprises the following steps: (1) using a plate press to press the biochemical sludge to obtain a sludge plate; (2) using a low-temperature evaporator to evaporate the sludge plate in step (1); (3) treating the gas obtained after the evaporation treatment in step (2) in turn through a precooler and a cryogenic refrigerator; (4) using activated carbon to adsorb the gas after the condensation treatment in step (3), and discharging the purified gas. The treatment method can achieve good treatment of biochemical sludge containing organic solvents, and has the advantages of safety, high efficiency and low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to a biochemical sludge treatment method. Background Art

[0002] In the existing process water treatment process, activated sludge is often used to biochemically treat process water. Due to the survival and adaptation problems of the bacterial flora, the soil (biochemical sludge) in the treatment pool needs to be replaced and treated from time to time to ensure the activity of the bacteria. However, in the preparation process of industrial chemicals, organic solvents are often used to assist the reaction. Therefore, the process water generated in the production process also contains organic solvents, which in turn causes the biochemical sludge to contain organic solvents. If the conventional heating evaporation method is used to reduce the amount of biochemical sludge, the organic solvent contained in the biochemical sludge will have the risk of combustion and explosion, posing a safety hazard.

[0003] Therefore, the present invention hopes to propose a safe, efficient and low-cost biochemical sludge treatment method to meet the treatment needs of the above-mentioned biochemical sludge containing organic solvents. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a biochemical sludge treatment method, which can achieve good treatment of biochemical sludge containing organic solvents and has the advantages of safety, high efficiency and low cost.

[0005] The present invention provides a biochemical sludge treatment method, comprising the following steps:

[0006] (1) using a press machine to press the biochemical sludge to obtain a mud plate;

[0007] (2) using a low-temperature evaporator to evaporate the mud plate described in step (1);

[0008] (3) treating the gas obtained after the evaporation treatment in step (2) in a precooler and a cryogenic refrigerator in sequence;

[0009] (4) The gas after condensation treatment in step (3) is then adsorbed by activated carbon and the purified gas is discharged.

[0010] Among them, after the condensation treatment in the precooler and the deep cooler in step (3), the organic solvent and water contained in the gas can be effectively condensed into a liquid state for collection and treatment. The adsorption treatment in step (4) can remove the VOC (volatile organic compounds) contained in the gas to prevent the discharged gas from polluting the environment.

[0011] Preferably, in step (1), a pneumatic pump is used to transport the biochemical sludge to a press for pressing.

[0012] Preferably, the pressing pressure in step (1) is controlled at 0.1-1 MPa. It should be noted that the pressing pressure is the pressure of the filter cloth part of the plate press.

[0013] Preferably, the pressing time in step (1) is controlled within 15-30 hours.

[0014] Preferably, in step (2), a stirrer is also used to break up the mud plate. Using a stirrer to break up the mud plate can expand the surface area of ​​the sludge, thereby increasing the speed and effect of evaporation.

[0015] Preferably, the setting temperature of the low-temperature evaporator in step (2) is 35-45°C.

[0016] Preferably, the evaporation treatment in step (2) also includes a vacuuming operation. The negative pressure effect formed by the vacuuming can reduce the boiling point of the solvent in the sludge, thereby achieving good evaporation and separation of the solvent even at low temperatures.

[0017] Preferably, the condensing medium in the precooler in step (3) is chilled water, and the condensing medium in the deep cooler is ethylene glycol.

[0018] Preferably, the cooling temperature of the precooler in step (3) is 5-12°C.

[0019] Preferably, the cooling temperature of the cryogenic freezer in step (3) is -10 to -20°C.

[0020] Preferably, step (4) further comprises the operation of desorbing and regenerating the activated carbon. When the activated carbon adsorption reaches saturation, the saturated activated carbon can be desorbed and regenerated so that the activated carbon can be recycled, thereby reducing costs.

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

[0022] 1. The present invention uses low-temperature evaporation technology to treat biochemical sludge, thereby avoiding the risk of combustion and explosion of organic solvents in biochemical sludge; in addition, since the evaporation temperature of low-temperature evaporation is low, the steam used in the factory can be used for secondary utilization, which can achieve cascade utilization of energy compared to ordinary steam, thereby achieving the purpose of energy saving.

[0023] 2. The present invention also condenses the gas obtained after low-temperature evaporation by combining pre-cooling and deep cooling technology, which can effectively separate the organic solvent and water vapor brought out by the gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the process of biochemical sludge treatment method in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make those skilled in the art more clearly understand the technical solution of the present invention, the following examples are listed for illustration. It should be pointed out that the following examples are only preferred embodiments of the present invention and do not constitute a limitation on the protection scope of the present invention. Any modification, substitution, and combination made without violating the spirit and principle of the present invention are included in the protection scope of the present invention.

[0026] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0027] It is known that the process water produced in the production of acrylic acid esters contains organic solvents such as toluene and cyclohexane, and the biochemical sludge formed after treatment also contains the above organic solvents. This embodiment provides a method for treating biochemical sludge to achieve the purpose of treating the above and similar biochemical sludges efficiently, environmentally friendly and at low cost. Figure 1 , specifically including the following steps:

[0028] (1) The biochemical sludge (i.e., sludge water) at the bottom of each treatment pool of the sewage station is pumped into a press (model XMYJ60 / 800-UB) with a pneumatic pump, and the pressing pressure is controlled to be 0.8MPa (filter cloth part) for 20 hours. Under the action of the press, most of the water in the sludge water is pressed out to form a mud plate (the water content of the mud plate is about 20%). The water produced by pressing is filtered through the filter cloth outside the press and then flows into the mixing tank of the sewage station.

[0029] (2) Take out the mud plate and put it into the low-temperature evaporator (FEV-400S). The low-temperature evaporator is also equipped with a stirrer. By turning on the stirrer (set the speed to 80r / min), the mud plate is broken to increase the surface area of ​​the sludge, which is conducive to the evaporation and dehydration operation in the low-temperature evaporator. First, adjust the heating temperature of the low-temperature evaporator to 35°C, and turn on the vacuum pump to reduce the boiling point of the solvent (organic solvent and water) in the sludge under the vacuum negative pressure, and separate the solvent from the sludge under the low-temperature evaporation. After most of the solvent is separated, break the negative pressure state, increase the heating temperature to 45°C, and introduce dry air. The dry air is fully in contact with the sludge. During this contact process, the dry air reaches a saturated state and becomes wet air, thereby achieving the purpose of reducing the amount. After low-temperature evaporation treatment, the moisture content of the sludge can be reduced to 5%. During the condensation and evaporation period, the speed of the evaporator stirrer, the temperature of the evaporator and the air flow rate can be adjusted according to the specific state of the sludge and the humidity value of the air outlet to improve the dehydration efficiency of the low-temperature evaporator.

[0030] One of the advantages of low-temperature evaporation is that the evaporation temperature is low (less than 50°C), which can be used to reuse the steam used in the factory. Compared with ordinary steam, it can achieve cascade utilization of energy and achieve energy saving. In addition, since the temperature of low-temperature evaporation is low, the risk of combustion and explosion of organic solvents can be avoided, making the treatment of biochemical sludge safer and more reliable.

[0031] (3) The gas obtained after low-temperature evaporation treatment is first added to a precooler with chilled water as the condensing medium (the precooling temperature is about 12°C) to condense the solvent and water vapor in the gas and collect them in buffer tank A. After the precooling stage, the gas enters a deep freezer with ethylene glycol as the condensing medium (the deep cooling temperature is about -15°C) to further condense the solvent and water vapor in the gas and collect them in buffer tank B. The condensed solvent and water vapor in buffer tank A / B are pumped into a high-concentration water tank.

[0032] Since the gas obtained after low-temperature evaporation contains a variety of hydrocarbons and non-hydrocarbon organic substances with different molecular sizes and chemical structures, the condensation is divided into a pre-cooling stage and a deep cooling stage. In the pre-cooling stage, chilled water is used as the condensation medium to cool the hot gas; in the deep cooling stage, ethylene glycol is used as the condensation medium to further cool the gas, thereby separating part of the solvent and water vapor brought out by the gas.

[0033] (4) The gas condensed in step (3) is passed through an activated carbon tank to capture and adsorb VOC (volatile organic compounds) in the air. The activated carbon tank is divided into two tanks A / B and used alternately. For example, when the activated carbon tank A adsorbs to the limit, the activated carbon tank B is switched to adsorb, and at the same time, the activated carbon tank A is subjected to activated carbon desorption treatment, using steam heating for desorption. The purified gas is discharged into the atmosphere. After testing, the total non-methane hydrocarbon value of the gas discharged into the atmosphere is 5mg / m 3 , less than 6mg / m 3 concentration limit.

[0034] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A biochemical sludge treatment method, characterized in that: The following steps are involved: (1) Using a press machine to press the biochemical sludge to obtain a sludge board; (2) using a low-temperature evaporator to evaporate the mud plate described in step (1); (3) condensing the gas obtained after the evaporation treatment in step (2) in a precooler and a cryogenic refrigerator in sequence; (4) The gas condensed in step (3) is then adsorbed by activated carbon and the purified gas is discharged; The pressing pressure in step (1) is controlled at 0.1-1 MPa; In step (2), the low temperature evaporator is set at a temperature of 35-45°C; The evaporation process in step (2) also includes a vacuum operation.

2. The biochemical sludge treatment method according to claim 1, characterized in that: In step (1), a pneumatic pump is used to transport the biochemical sludge to a press for pressing.

3. The biochemical sludge treatment method according to claim 1, characterized in that: The pressing time in step (1) is controlled within 15-30 hours.

4. The biochemical sludge treatment method according to claim 1, characterized in that: In step (2), a stirrer is also used to break up the mud plate.

5. The biochemical sludge treatment method according to claim 1, characterized in that: In step (3), the condensing medium in the precooler is chilled water, and the condensing medium in the deep cooler is ethylene glycol.

6. The biochemical sludge treatment method according to claim 1, characterized in that: The cooling temperature of the precooler in step (3) is 5-12°C, and the cooling temperature of the deep freezer is -10 to -20°C.

7. The biochemical sludge treatment method according to claim 1, characterized in that: Step (4) also includes the operation of desorption and regeneration of the activated carbon.

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