Method for improving yellow phosphorus polluted soil treatment efficiency by using fuel gas in-situ thermal desorption high-temperature flue gas

Abstract

The invention relates to the technical field of soil treatment, in particular to a method for improving the yellow phosphorus contaminated soil treatment efficiency through fuel gas in-situ thermal desorption of high-temperature flue gas. The method comprises the following steps: step 1, grinding the yellow phosphorus polluted soil into slurry; step 2, continuously introducing high-temperature flue gas generated by fuel gas in-situ thermal desorption into the slurry; step 3, conveying the slurry to an atomizer at the top of a combustion tower, atomizing the slurry into small particles by using high-pressure air, and continuously introducing high-temperature flue gas into the bottom of the combustion tower; 4, smoke generated by the combustion tower is absorbed into a scrubber tower, and meanwhile it is guaranteed that the combustion tower is always in negative pressure; 5, the treated slurry is conveyed out from the bottom of the combustion tower. According to the invention, the temperature of the yellow phosphorus slurry is increased by using the fuel gas in-situ thermal desorption high-temperature flue gas, the combustion reaction rate of the yellow phosphorus slurry is increased, and meanwhile, the heat energy loss is also reduced. Through sufficient combustion treatment of yellow phosphorus, thorough treatment of yellow phosphorus polluted soil can be achieved, and no chemical agent needs to be added into the soil in the treatment process.

Description

Technical Field

[0001] The invention relates to the technical field of soil treatment, and in particular to a method for improving the treatment efficiency of yellow phosphorus-contaminated soil by utilizing in-situ thermal desorption of high-temperature flue gas from fuel gas. Background Art

[0002] With the acceleration of urbanization, the function of urban land has been adjusted, and a large number of polluting enterprises have relocated, leaving behind a large number of high-risk industrial pollution sites such as pesticides and chemicals. Due to the previous production history activities, the soil of these polluted sites has been polluted to varying degrees, and the types of pollutants are also relatively complex. Typical types of pollution include compound pollution of organic matter and yellow phosphorus, among which organic matter is represented by benzene series and chlorinated hydrocarbons. These two types of substances are generally toxic, irritating, teratogenic and carcinogenic. In particular, benzene, toluene, vinyl chloride, trichloroethylene, etc. can cause great harm to human health. Therefore, such pollutants often need to be strictly controlled.

[0003] Organic pollution in the decommissioning sites of pesticide chemical plants often has the characteristics of many types of pollutants, high pollution concentration, deep pollution depth, and wide pollution range. Therefore, gas in-situ thermal desorption technology is often used. It is widely used due to its wide range of applications, high heating temperature, and easy access to energy. The principle of gas in-situ thermal desorption technology is to heat underground soil and groundwater with gas, and promote the volatilization of pollutants in the soil and groundwater by increasing the temperature, thereby achieving the goal of remediation. However, the high-temperature flue gas generated after gas heating is often directly discharged into the atmosphere, resulting in a waste of heat energy.

[0004] Yellow phosphorus is flammable, with an ignition point of 40°C and a melting point of 44°C. After spontaneous combustion, it will produce white smoke of phosphorus pentoxide, which is dispersed in the air in the form of white powder and produces a strong irritating odor, endangering the safety and health of personnel. Yellow phosphorus is an important industrial raw material, which can be used as a raw material for the production of pesticide products such as methyl parathion and dichlorvos, as well as chemical products such as trichlorothiophos. Therefore, yellow phosphorus-contaminated soil can often be found on the decommissioned sites of pesticide chemical plants. Chinese patents CN106345798A, CN113024064A, CN113290037A, CN113996646A, etc. mainly repair yellow phosphorus-contaminated soil by chemical oxidation. The principle is to use oxidants to oxidize yellow phosphorus in the soil into harmless phosphates. However, in actual use, it has problems such as cumbersome procedures, excessive use of repair agents, and incomplete oxidation of yellow phosphorus, which affect the final repair effect. Summary of the invention

[0005] In order to make full use of the thermal energy of high-temperature flue gas generated by in-situ thermal desorption of fuel gas and solve the problem of poor oxidation remediation effect of yellow phosphorus contaminated soil, the purpose of the present invention is to provide a method for improving the treatment efficiency of yellow phosphorus contaminated soil by in-situ thermal desorption of high-temperature flue gas.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0007] A method for improving the treatment efficiency of yellow phosphorus contaminated soil by in-situ thermal desorption of high-temperature flue gas using fuel gas is provided, which comprises the following steps:

[0008] Step 1, grinding yellow phosphorus contaminated soil into slurry;

[0009] Step 2, continuously introducing high-temperature flue gas generated by in-situ thermal desorption of fuel gas into the mud;

[0010] Step 3: Send the slurry to the atomizer at the top of the combustion tower, use high-pressure air to atomize the slurry into small particles, and continue to introduce hot flue gas at the bottom of the combustion tower;

[0011] Step 4, absorbing the smoke generated by the combustion tower into the scrubber, while ensuring that the combustion tower is always under negative pressure;

[0012] Step 5: The treated mud is transferred out from the bottom of the combustion tower.

[0013] Furthermore, the method of step 1 is specifically as follows:

[0014] The yellow phosphorus contaminated soil is preliminarily screened to remove stones and construction waste from the soil; clean water is added to grind the soil into mud, and the ground mud is stored in a closed mud pool, with the water-to-soil ratio controlled at 1:3 to 1:6.

[0015] Furthermore, the yellow phosphorus contaminated soil is a high-concentration yellow phosphorus contaminated soil with a yellow phosphorus content of more than 20%.

[0016] Furthermore, in step 2, the temperature of the high-temperature flue gas is 150-350°C.

[0017] Furthermore, in step 3, the combustion tower is designed to be in a cone shape.

[0018] Furthermore, in step 3, 2 to 3 lining layers are designed in the combustion tower, the mud is sprayed on the lining layer by atomization, and the yellow phosphorus spontaneously combusts on the lining layer.

[0019] Furthermore, the lining can realize pulse oscillation through a pulse controller and an electromagnetic valve arranged outside the tower, and can be set to oscillate once every 3 to 10 minutes to remove soil or dust attached to the surface of the lining.

[0020] Furthermore, the combustion tower and the scrubbing tower are both made of acid-resistant stainless steel or glass fiber reinforced plastic.

[0021] The beneficial effects of the present invention are:

[0022] 1. Energy saving and consumption reduction: Use gas to thermally desorb high-temperature flue gas in situ to increase the temperature of yellow phosphorus slurry, improve its combustion reaction rate, and also reduce heat energy loss.

[0023] 2. Complete restoration: Through the complete combustion of yellow phosphorus, the soil contaminated by yellow phosphorus can be completely treated.

[0024] 3. Small secondary pollution: No chemical agents need to be added to the soil during the treatment process, which protects the soil quality and future use function. DETAILED DESCRIPTION

[0025] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0026] Example 1

[0027] 1. 1000kg of soil contaminated with high concentration of yellow phosphorus with a yellow phosphorus content of 23.8% was preliminarily screened to remove stones, construction waste, etc. in the soil.

[0028] 2. Use a wet ball mill to grind the soil into mud with clean water. The ground mud is stored in a closed mud pool. The water-soil ratio of the mud is controlled at 1:3. The yellow phosphorus-contaminated soil is turned into mud, which can avoid the combustion of yellow phosphorus in the pretreatment process of the contaminated soil.

[0029] 3. Utilize the high-temperature flue gas (generally at 150-350°C) generated by the combustion of the in-situ heating well gas, which does not contain any harmful substances. After a simple on-site modification of the flue gas discharge pipeline of the hot well added by the gas thermal degassing, the high-temperature flue gas is continuously introduced into the mud in the closed mud pool. The functions are: (1) to fully stir the mud, improve the fluidity of the mud, and prevent it from settling into agglomerates; (2) to increase the mud temperature, which is controlled at 60-90°C, accelerating its combustion speed in the combustion tower.

[0030] 4. The mud in the mud pool is delivered to the atomizer at the top of the combustion tower through a mud pump, and the mud is atomized into small particles by high-pressure air. High-temperature flue gas is continuously introduced into the bottom of the combustion tower through a fan to ensure that the yellow phosphorus attached with fine particles burns under high temperature and sufficient oxygen conditions to generate phosphorus pentoxide smoke.

[0031] 5. The combustion tower is designed in a cone shape so that the heat can be gradually concentrated from the bottom to the top, which can effectively utilize the heat and improve the combustion efficiency of yellow phosphorus. There are two lining layers in the combustion tower. The mud is sprayed on the lining layer by atomization. The yellow phosphorus spontaneously burns on the lining layer. The lining layer can realize pulse oscillation through the pulse controller and solenoid valve set outside the tower. It is set to oscillate every 3 minutes to remove the soil or dust attached to the surface of the lining layer.

[0032] 6. The smoke generated by the combustion tower is absorbed into the scrubber through the fan, and the combustion tower is always kept at a negative pressure (-10 to -30 kpa). The scrubber mainly removes acidic substances such as HF and PH3 in the tail gas generated by the combustion of yellow phosphorus through alkaline liquid, and can also remove a small amount of dust carried by the tail gas, and finally discharge it into the air. The alkaline liquid can be prepared by flake caustic soda, lime, etc.

[0033] 7. The treated mud is conveyed from the bottom of the combustion tower via a conveyor belt to the repaired soil inspection area, dehydrated by a filter press and dried. After drying, the repair acceptance is carried out.

[0034] In this embodiment, the combustion tower and the scrubbing tower are both made of acid-resistant stainless steel or fiberglass to prevent acid corrosion.

[0035] After testing, the yellow phosphorus content in the soil after treatment dropped from the initial 23.8% to 0.08%.

[0036] Example 2

[0037] 1. 1000kg of soil contaminated with high concentration of yellow phosphorus with a yellow phosphorus content of 30.1% was preliminarily screened to remove stones, construction waste, etc. in the soil.

[0038] 2. Use a wet ball mill to grind the soil into mud with clean water. The ground mud is stored in a closed mud pool. The water-soil ratio of the mud is controlled at 1:5. The yellow phosphorus-contaminated soil is turned into mud, which can avoid the combustion of yellow phosphorus in the pretreatment process of the contaminated soil.

[0039] 3. Utilize the high-temperature flue gas (generally at 150-350°C) generated by the combustion of the in-situ heating well gas, which does not contain any harmful substances. After a simple on-site modification of the flue gas discharge pipeline of the hot well added by the gas thermal degassing, the high-temperature flue gas is continuously introduced into the mud in the closed mud pool. The functions are: (1) to fully stir the mud, improve the fluidity of the mud, and prevent it from settling into agglomerates; (2) to increase the mud temperature, control the mud at 60-90°C, and accelerate its combustion speed in the combustion tower.

[0040] 4. The mud in the mud pool is sent to the atomizer at the top of the combustion tower through a mud pump, and the mud is atomized into small particles by high-pressure air. Hot flue gas is continuously introduced into the bottom of the combustion tower through a fan to ensure that the yellow phosphorus attached with fine particles burns under high temperature and sufficient oxygen conditions to generate phosphorus pentoxide smoke.

[0041] 5. The combustion tower is designed in a cone shape so that the heat can be gradually concentrated from the bottom to the top, which can effectively utilize the heat and improve the combustion efficiency of yellow phosphorus. There are three lining layers in the combustion tower. The mud is sprayed on the lining layer by atomization. The yellow phosphorus spontaneously burns on the lining layer. The lining layer can realize pulse oscillation through the pulse controller and solenoid valve set outside the tower. It can be set to oscillate every 5 minutes to remove the soil or dust attached to the surface of the lining layer.

[0042] 6. The smoke generated by the combustion tower is absorbed into the scrubber through the fan, and the combustion tower is always kept at a negative pressure (-10 to -30 kpa). The scrubber mainly removes acidic substances such as HF and PH3 in the tail gas generated by the combustion of yellow phosphorus through alkaline liquid, and can also remove the dust carried by the tail gas and finally discharge it into the air. The alkaline liquid can be prepared by flake caustic soda, lime, etc.

[0043] 7. The treated mud is conveyed from the bottom of the combustion tower via a conveyor belt to the repaired soil inspection area, dehydrated by a filter press and dried. After drying, the repair acceptance is carried out.

[0044] In this embodiment, the combustion tower and the scrubbing tower are both made of acid-resistant stainless steel or fiberglass to prevent acid corrosion.

[0045] After testing, the yellow phosphorus content in the soil after treatment dropped from the initial 30.1% to 0.05%.

[0046] Example 3

[0047] 1. 1000kg of soil contaminated with high concentration of yellow phosphorus with a yellow phosphorus content of 32.6% was preliminarily screened to remove stones, construction waste, etc. in the soil.

[0048] 2. Use a wet ball mill to add clean water to grind the soil into mud. The ground mud is stored in a closed mud pool. The water-soil ratio of the mud is controlled at 1:6. The yellow phosphorus-contaminated soil is turned into mud, which can avoid the combustion of yellow phosphorus in the pretreatment process of the contaminated soil.

[0049] 3. Utilize the high-temperature flue gas (generally at 150-350°C) generated by the combustion of the in-situ heating well gas, which does not contain any harmful substances. After a simple on-site modification of the flue gas discharge pipeline of the hot well added by the gas thermal degassing, the high-temperature flue gas is continuously introduced into the mud in the closed mud pool. The functions are: (1) to fully stir the mud, improve the fluidity of the mud, and prevent it from settling into agglomerates; (2) to increase the mud temperature, control the mud at 60-90°C, and accelerate its combustion speed in the combustion tower.

[0050] 4. The mud in the mud pool is sent to the atomizer at the top of the combustion tower through a mud pump, and the mud is atomized into small particles by high-pressure air. Hot flue gas is continuously introduced into the bottom of the combustion tower through a fan to ensure that the yellow phosphorus attached with fine particles burns under high temperature and sufficient oxygen conditions to generate phosphorus pentoxide smoke.

[0051] 5. The combustion tower is designed in a cone shape so that the heat can be gradually concentrated from the bottom to the top, which can effectively utilize the heat and improve the combustion efficiency of yellow phosphorus. There are three lining layers in the combustion tower. The mud is sprayed on the lining layer by atomization. The yellow phosphorus spontaneously burns on the lining layer. The lining layer can realize pulse oscillation through the pulse controller and solenoid valve set outside the tower. It can be set to oscillate every 10 minutes to remove the soil or dust attached to the surface of the lining layer.

[0052] 6. The smoke generated by the combustion tower is absorbed into the scrubber through the fan, and the combustion tower is always kept at a negative pressure (-10 to -30 kpa). The scrubber mainly removes acidic substances such as HF and PH3 in the tail gas generated by the combustion of yellow phosphorus through alkaline liquid, and can also remove the dust carried by the tail gas and finally discharge it into the air. The alkaline liquid can be prepared by flake caustic soda, lime, etc.

[0053] 7. The treated mud is conveyed from the bottom of the combustion tower via a conveyor belt to the repaired soil inspection area, dehydrated by a filter press and dried. After drying, the repair acceptance is carried out.

[0054] In this embodiment, the combustion tower and the scrubbing tower are both made of acid-resistant stainless steel or fiberglass to prevent acid corrosion.

[0055] After testing, the yellow phosphorus content in the soil after treatment dropped from the initial 32.6% to 0.06%.

[0056] It should be noted that, except for the improvements mentioned in the technical solution of the present invention, the in-situ heating well, combustion tower and scrubbing tower involved in the present invention are of conventional design and are not within the protection scope of the present invention, so they are not described in detail.

[0057] In summary, combined with the specific implementation cases of the present invention, it can be determined that the technical solution of the present invention can achieve the thorough treatment of soil contaminated by high-concentration yellow phosphorus. And no chemical agent needs to be added to the soil during the treatment process, which can protect the soil quality and future use function.

[0058] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0059] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for improving the treatment efficiency of yellow phosphorus contaminated soil by in-situ thermal desorption of high-temperature flue gas using fuel gas, characterized in that: The following steps are involved: Step 1, grinding yellow phosphorus contaminated soil into slurry; Step 2, continuously introducing high-temperature flue gas generated by in-situ thermal desorption of fuel gas into the mud; Step 3: Send the slurry to the atomizer at the top of the combustion tower, use high-pressure air to atomize the slurry into small particles, and continuously introduce high-temperature flue gas into the bottom of the combustion tower; Step 4, absorbing the smoke generated by the combustion tower into the scrubber, while ensuring that the combustion tower is always under negative pressure; Step 5: The treated mud is transferred out from the bottom of the combustion tower.

2. The method for improving the treatment efficiency of yellow phosphorus contaminated soil by in-situ thermal desorption of high-temperature flue gas using fuel gas according to claim 1, characterized in that: In step 1, the water-to-soil ratio of the mud is controlled at 1:3 to 1:

6.

3. The method for improving the treatment efficiency of yellow phosphorus contaminated soil by in-situ thermal desorption of high-temperature flue gas using fuel gas according to claim 1, characterized in that: In step 1, the yellow phosphorus contaminated soil is a high-concentration yellow phosphorus contaminated soil with a yellow phosphorus content of more than 20%.

4. The method for improving the treatment efficiency of yellow phosphorus contaminated soil by in-situ thermal desorption of high-temperature flue gas using fuel gas according to claim 1, characterized in that: In step 2, the temperature of the high-temperature flue gas is 150-350°C.

5. The method for improving the treatment efficiency of yellow phosphorus contaminated soil by in-situ thermal desorption of high-temperature flue gas using fuel gas according to claim 1, characterized in that: In step 3, the combustion tower is designed to be conical in shape.

6. The method for improving the treatment efficiency of yellow phosphorus contaminated soil by in-situ thermal desorption of high-temperature flue gas using fuel gas according to claim 1, characterized in that: In step 3, 2 to 3 lining layers are designed in the combustion tower, the mud is sprayed on the lining layer by atomization, and the yellow phosphorus spontaneously combusts on the lining layer.

7. The method for improving the treatment efficiency of yellow phosphorus contaminated soil by in-situ thermal desorption of high-temperature flue gas using fuel gas according to claim 6, characterized in that: The lining can achieve pulse oscillation through a pulse controller and solenoid valve installed outside the tower. It can be set to oscillate once every 3 to 10 minutes to remove soil or dust attached to the surface of the lining.