Method for burning back thermal desorption tail gas of petroleum hydrocarbon polluted site

Abstract

The invention relates to the technical field of soil remediation and waste gas treatment, in particular to a thermal desorption tail gas burn-back method for a petroleum hydrocarbon polluted site, organic waste gas extracted by thermal desorption is sent to a burner to be burnt, so that the organic polluted waste gas does not need to be treated by traditional technologies such as adsorption and oxidation, secondary pollution is avoided, and the method is environment-friendly and energy-saving. Petroleum hydrocarbon organic pollutants can generate a heat value during combustion, the heat value can be just used for heating the polluted soil needing to be repaired, the use amount of natural gas or liquefied petroleum gas can be reduced, higher efficiency and energy conservation are achieved, and the problem that after the organic pollutants in the soil are extracted, the soil cannot be polluted is effectively solved. The organic pollution waste gas still needs to be treated through traditional adsorption and oxidation technologies, the treatment effect of the mode is common, and hazardous waste can be generated; and if an incineration mode is adopted, the situation of relatively high energy consumption also exists.

Description

Technical Field

[0001] The invention relates to the technical field of soil remediation and waste gas treatment, and in particular to a method for thermal desorption of tail gas from a petroleum hydrocarbon contaminated site and burning back the tail gas. Background Art

[0002] In-situ thermal desorption is a relatively mature method for treating petroleum hydrocarbon contaminated sites. Its principle can be briefly described as follows: natural gas or liquefied petroleum gas is burned in a combustion chamber to produce high-temperature gas; the high-temperature gas is injected into a single heating well and allowed to flow back and forth in the well; the high-temperature gas indirectly heats the soil, and the target remediation area is heated by heat conduction, so that the soil temperature rises to the target temperature; when the soil temperature reaches the target value, the pollutants in the soil can be rapidly desorbed and separated from the soil, and the separated organic pollutants are separated from the original soil by extraction to achieve the purpose of remediation.

[0003] However, after the organic pollutants in the soil are extracted, they still need to be treated through traditional adsorption and oxidation technologies. The treatment effect of this method is general and it will also produce hazardous waste. If incineration is used, it will consume a lot of energy. Summary of the invention

[0004] The purpose of the present invention is to provide a method for thermal desorption and incineration of tail gas from petroleum hydrocarbon contaminated sites, so as to solve the problem that after the organic pollutants in the soil are extracted, the organic polluted waste gas still needs to be treated by traditional adsorption and oxidation technologies, and the treatment effect of this method is general and hazardous waste is generated; and if incineration is used, there is a problem of high energy consumption.

[0005] To achieve the above-mentioned purpose, the present invention provides a method for thermal desorption tail gas reburning at a petroleum hydrocarbon contaminated site, which is applied to an extraction and reburning device, wherein the extraction and reburning device comprises a first gas-liquid separator, a primary heat exchanger, a second gas-liquid separator, a secondary heat exchanger, a third gas-liquid separator, a vacuum pump and a burner, wherein the first gas-liquid separator, the second gas-liquid separator and the third gas-liquid separator are connected to a water treatment system, the gas outlet end of the burner is connected to a wellhead, a reburning fan is arranged at the wellhead, the first gas-liquid separator, the primary heat exchanger, the second gas-liquid separator, the secondary heat exchanger, the third gas-liquid separator, the vacuum pump and the burner are sequentially connected, and the method comprises the following steps:

[0006] S1: The high-temperature polluted steam extracted from the two-phase extraction well enters the first gas-liquid separator for primary gas-liquid separation, and the tail gas enters the primary heat exchanger for cooling, and the tail water generated by the gas-liquid separation is discharged into the water treatment system for treatment;

[0007] S2: the tail gas after cooling enters the second gas-liquid separator for secondary gas-liquid separation, and then the tail gas enters the secondary heat exchanger for further cooling, and the tail water generated by the gas-liquid separation is discharged into the water treatment system for treatment;

[0008] S3: the tail gas after further cooling enters the third gas-liquid separator for three-stage gas-liquid separation, and then the tail gas enters the vacuum pump, and the tail water generated by the gas-liquid separation is discharged into the water treatment system for treatment;

[0009] S4: starting the backfire blower and the vacuum pump, and adjusting the pipeline valve of the burner, so that a negative pressure is formed in the pipeline between the wellhead and the burner, and the negative pressure can offset the positive pressure of the vacuum pump, and then the tail gas is discharged into the burner;

[0010] S5: Finally, the exhaust gas is incinerated by the flame of the burner, and the exhaust gas after combustion is tested to ensure that the emission meets the standard.

[0011] Wherein, a cooling tower is arranged on the second gas-liquid separator.

[0012] Wherein, the burner, the vacuum pump and the wellhead are connected via a three-way valve.

[0013] Wherein, the water treatment system includes three water pumps, a pretreatment tank, water treatment equipment and a water outlet tank. The three water pumps are connected to the pretreatment tank respectively, and one of the water pumps is connected to the first gas-liquid separator, one of the water pumps is connected to the second gas-liquid separator, and one of the water pumps is connected to the third gas-liquid separator. The pretreatment tank, the water treatment equipment and the water outlet tank are connected in sequence.

[0014] Among them, in step S3, most of the water vapor is removed from the exhaust gas and it is in a high temperature positive pressure state.

[0015] In step S4, before installing the burner, the maximum and minimum air-fuel ratios are first determined, and then based on the results, the air volume and speed of each air outlet in the system are adjusted through an anemometer.

[0016] Wherein, in step S5, the burner is in a negative pressure state.

[0017] Wherein, in step S5, the exhaust gas after combustion is detected, and the detection includes flame temperature, outlet air volume, wind speed, water vapor content and exhaust gas pollutant concentration.

[0018] The invention discloses a method for thermal desorption tail gas re-burning of a petroleum hydrocarbon contaminated site, wherein the organic waste gas extracted by thermal desorption is sent to a burner for incineration, thereby eliminating the need to use conventional adsorption, oxidation and other technologies to treat the organic polluted waste gas, thereby preventing secondary pollution. Furthermore, petroleum hydrocarbon organic pollutants generate calorific value when burned, which can be used to heat the contaminated soil to be repaired, thereby reducing the use of natural gas or liquefied petroleum gas, and achieving greater efficiency and energy saving. This effectively solves the problem that after the organic pollutants in the soil are extracted, the organic polluted waste gas still needs to be treated by conventional adsorption and oxidation technologies, which has a general treatment effect and also generates hazardous waste. If the incineration method is used, the technical problem of high energy consumption exists. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 The invention provides a flow chart of the steps of the method for thermal desorption of tail gas from a petroleum hydrocarbon contaminated site.

[0021] Figure 2 It is a flow chart of the extraction and reburning device provided by the present invention.

[0022] 1-first gas-liquid separator, 2-primary heat exchanger, 3-second gas-liquid separator, 4-secondary heat exchanger, 5-third gas-liquid separator, 6-vacuum pump, 7-burner, 8-wellhead, 9-backfire fan, 10-cooling tower, 11-three-way valve, 12-water pump, 13-pretreatment tank, 14-water treatment equipment, 15-water outlet tank, 16-two-phase extraction well. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0024] See also Figure 1-2The present invention provides a method for thermal desorption tail gas reburning at a petroleum hydrocarbon contaminated site, which is applied to an extraction and reburning device, wherein the extraction and reburning device comprises a first gas-liquid separator 1, a primary heat exchanger 2, a second gas-liquid separator 3, a secondary heat exchanger 4, a third gas-liquid separator 5, a vacuum pump 6 and a burner 7, wherein the first gas-liquid separator 1, the second gas-liquid separator 3 and the third gas-liquid separator 5 are connected to a water treatment system, the gas outlet end of the burner 7 is connected to a wellhead 8, and a reburning fan 9 is provided at the wellhead 8, the first gas-liquid separator 1, the primary heat exchanger 2, the second gas-liquid separator 3, the secondary heat exchanger 4, the third gas-liquid separator 5, the vacuum pump 6 and the burner 7 are sequentially connected, and the method comprises the following steps:

[0025] S1: The high-temperature polluted steam extracted through the two-phase extraction well 16 enters the first gas-liquid separator 1 for primary gas-liquid separation, and the tail gas enters the primary heat exchanger 2 for cooling, and the tail water generated by the gas-liquid separation is discharged into the water treatment system for treatment;

[0026] S2: the tail gas after cooling enters the second gas-liquid separator 3 for secondary gas-liquid separation, and then the tail gas enters the secondary heat exchanger 4 for further cooling, and the tail water generated by the gas-liquid separation is discharged into the water treatment system for treatment;

[0027] S3: the tail gas after further cooling enters the third gas-liquid separator 5 for three-stage gas-liquid separation, and then the tail gas enters the vacuum pump 6, and the tail water generated by the gas-liquid separation is discharged into the water treatment system for treatment;

[0028] S4: starting the backfire blower 9 and the vacuum pump 6, and adjusting the pipeline valve of the burner 7, so that a negative pressure is formed in the pipeline between the wellhead 8 and the burner 7, and the negative pressure can offset the positive pressure of the vacuum pump 6, and then the tail gas is discharged into the burner 7;

[0029] S5: Finally, the tail gas is incinerated by the flame of the burner 7, and the tail gas after combustion is tested to ensure that the emission meets the standard.

[0030] In this embodiment, the organic waste gas extracted by thermal desorption is sent to the burner 7 for incineration, so there is no need to use traditional adsorption, oxidation and other technologies to treat the organic polluted waste gas, so that no secondary pollution will be generated, and petroleum hydrocarbon organic pollutants will generate calorific value when burned, which can be used to provide heating for the contaminated soil to be repaired, which can reduce the use of natural gas or liquefied petroleum gas, and is more efficient and energy-saving. This effectively solves the problem that after the organic pollutants in the soil are extracted, the organic polluted waste gas still needs to be treated by traditional adsorption and oxidation technologies, and the treatment effect of this method is general and hazardous waste will be generated; if the incineration method is adopted, it will have the technical problem of high energy consumption.

[0031] Wherein, a cooling tower 10 is arranged on the second gas-liquid separator 3. The arrangement of the cooling tower 10 helps to reduce the temperature of the gas coming out of the second gas-liquid separator 3, further remove the water vapor in the tail gas, and improve the purity of the tail gas.

[0032] The burner 7, the vacuum pump 6 and the wellhead 8 are connected via a three-way valve 11. The three-way valve 11 can be used to adjust the exhaust gas flow direction as needed to switch the exhaust gas between different treatment paths.

[0033] Among them, the water treatment system includes three water pumps 12, a pretreatment tank 13, a water treatment equipment 14 and a water outlet tank 15. The three water pumps 12 are connected to the pretreatment tank 13 respectively, and one of the water pumps 12 is connected to the first gas-liquid separator 1, one water pump 12 is connected to the second gas-liquid separator 3, and one water pump 12 is connected to the third gas-liquid separator 5. The pretreatment tank 13, the water treatment equipment 14 and the water outlet tank 15 are connected in sequence.

[0034] Among them, in step S3, most of the water vapor is removed from the exhaust gas, and it is in a high-temperature positive pressure state. The exhaust gas after removing the water vapor is drier, which is beneficial to the subsequent combustion treatment, and the high-temperature positive pressure state ensures that the exhaust gas can flow stably to the burner 7, providing good conditions for the combustion process.

[0035] Among them, in step S4, before the burner 7 is installed, the maximum and minimum air-fuel ratios are first determined, and then according to the results, the air volume and speed of each air outlet in the system are adjusted through the anemometer. This step can ensure that the burner 7 can operate under the best working conditions, which not only ensures the combustion efficiency, but also avoids the problems of incomplete combustion or excessive pollutant emissions caused by improper air-fuel ratio.

[0036] Among them, in step S5, the burner 7 is in a negative pressure state. The negative pressure state helps to prevent exhaust gas leakage and ensures that the exhaust gas can be completely burned and discharged into the atmosphere. At the same time, the negative pressure state also helps to improve the air suction capacity of the burner 7, so that the exhaust gas can be more fully mixed with the air and burned.

[0037] Among them, in step S5, the exhaust gas after combustion is detected, and the detection includes flame temperature, outlet air volume, wind speed, water vapor content and exhaust pollutant concentration. By real-time monitoring of various parameters of the exhaust gas, potential problems can be discovered and dealt with in time. Among them, too high or too low flame temperature will affect the combustion efficiency; changes in outlet air volume and wind speed reflect the working status of the burner 7; monitoring of water vapor content and exhaust pollutant concentration helps to evaluate the exhaust treatment effect and ensure that emissions meet standards.

[0038] In the present invention, the backfire blower 9 can be selected to be a high temperature resistant type, because the burner 7 is started at negative pressure, and the outlet of the vacuum pump 6 is positive pressure, so the backfire blower 9 can offset the negative pressure of the positive pressure in the vacuum pump 6, ensuring that the burner 7 is in a negative pressure state.

[0039] The organic waste gas extracted by thermal desorption is sent to the burner 7 for incineration, so there is no need to use traditional adsorption, oxidation and other technologies to treat the organic polluted waste gas, so that no secondary pollution will be generated, and petroleum hydrocarbon organic pollutants will generate calorific value when burned, which can be used to provide heating for the contaminated soil to be repaired, which can reduce the use of natural gas or liquefied petroleum gas, and is more efficient and energy-saving. This effectively solves the problem that after the organic pollutants in the soil are extracted, the organic polluted waste gas still needs to be treated by traditional adsorption and oxidation technologies. The treatment effect of this method is general and hazardous waste will be generated; if the incineration method is adopted, it will have the technical problem of high energy consumption.

[0040] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for thermal desorption and burning back of tail gas from a petroleum hydrocarbon contaminated site, which is applied to an extraction and burning back device, wherein the extraction and burning back device comprises a first gas-liquid separator, a primary heat exchanger, a second gas-liquid separator, a secondary heat exchanger, a third gas-liquid separator, a vacuum pump and a burner, wherein the first gas-liquid separator, the second gas-liquid separator and the third gas-liquid separator are connected to a water treatment system, the gas outlet of the burner is connected to a wellhead, a backfire blower is provided at the wellhead, the first gas-liquid separator, the primary heat exchanger, the second gas-liquid separator, the secondary heat exchanger, the third gas-liquid separator and the vacuum pump are sequentially connected to the burner, and characterized in that: The steps include: S1: The high-temperature polluted steam extracted from the two-phase extraction well enters the first gas-liquid separator for primary gas-liquid separation, and the tail gas enters the primary heat exchanger for cooling, and the tail water generated by the gas-liquid separation is discharged into the water treatment system for treatment; S2: the tail gas after cooling enters the second gas-liquid separator for secondary gas-liquid separation, and then the tail gas enters the secondary heat exchanger for further cooling, and the tail water generated by the gas-liquid separation is discharged into the water treatment system for treatment; S3: the tail gas after further cooling enters the third gas-liquid separator for three-stage gas-liquid separation, and then the tail gas enters the vacuum pump, and the tail water generated by the gas-liquid separation is discharged into the water treatment system for treatment; S4: starting the backfire blower and the vacuum pump, and adjusting the pipeline valve of the burner, so that a negative pressure is formed in the pipeline between the wellhead and the burner, and the negative pressure can offset the positive pressure of the vacuum pump, and then the tail gas is discharged into the burner; S5: Finally, the exhaust gas is incinerated by the flame of the burner, and the exhaust gas after combustion is tested to ensure that the emission meets the standard.

2. The method for thermal desorption of tail gas from a petroleum hydrocarbon contaminated site as claimed in claim 1, characterized in that: A cooling tower is arranged on the second gas-liquid separator.

3. The method for thermal desorption of tail gas from a petroleum hydrocarbon contaminated site as claimed in claim 2, characterized in that: The burner, the vacuum pump and the wellhead are connected via a three-way valve.

4. The method for thermal desorption of tail gas from a petroleum hydrocarbon contaminated site as claimed in claim 3, characterized in that: The water treatment system includes three water pumps, a pretreatment tank, water treatment equipment and a water outlet tank. The three water pumps are connected to the pretreatment tank respectively, and one of the water pumps is connected to the first gas-liquid separator, one of the water pumps is connected to the second gas-liquid separator, and one of the water pumps is connected to the third gas-liquid separator. The pretreatment tank, the water treatment equipment and the water outlet tank are connected in sequence.

5. The method for thermal desorption of tail gas from a petroleum hydrocarbon contaminated site as claimed in claim 4, characterized in that: In step S3, most of the water vapor is removed from the exhaust gas, and the exhaust gas is in a high-temperature positive-pressure state.

6. The method for thermal desorption of tail gas from a petroleum hydrocarbon contaminated site as claimed in claim 5, characterized in that: In step S4, before installing the burner, the maximum and minimum air-fuel ratios are first determined, and then based on the results, the air volume and speed of each air outlet in the system are adjusted through an anemometer.

7. The method for thermal desorption of tail gas from a petroleum hydrocarbon contaminated site as claimed in claim 6, characterized in that: In step S5, the burner is in a negative pressure state.

8. The method for thermal desorption of tail gas from a petroleum hydrocarbon contaminated site as claimed in claim 7, characterized in that: In step S5, the exhaust gas after combustion is tested, including flame temperature, outlet air volume, wind speed, water vapor content and exhaust gas pollutant concentration.

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