CN111215439A - Method and device for controlling oxygen content of tail gas of thermal desorption system of organic contaminated soil - Google Patents
Method and device for controlling oxygen content of tail gas of thermal desorption system of organic contaminated soil Download PDFInfo
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- CN111215439A CN111215439A CN201910965147.7A CN201910965147A CN111215439A CN 111215439 A CN111215439 A CN 111215439A CN 201910965147 A CN201910965147 A CN 201910965147A CN 111215439 A CN111215439 A CN 111215439A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/06—Reclamation of contaminated soil thermally
- B09C1/065—Reclamation of contaminated soil thermally by pyrolysis
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/005—Extraction of vapours or gases using vacuum or venting
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Abstract
The invention discloses a method and a device for controlling the oxygen content of tail gas of a thermal desorption system of organic contaminated soil. The device comprises an air purification pretreatment unit, a nitrogen preparation unit and an online nitrogen supplement control unit which are sequentially connected according to the gas trend, and the online nitrogen supplement control unit provides nitrogen protection for the thermal desorption system of the organic contaminated soil. According to the invention, the air purification pretreatment unit enables the oil, water and dust content in the air to meet the requirements of the raw materials of the nitrogen generator; obtaining nitrogen with the purity of 98-99.99% through a nitrogen preparation unit; the nitrogen is automatically supplemented into the thermal desorption system through the online nitrogen supplementing unit. According to the invention, when the oxygen content in the thermal desorption system reaches or exceeds a preset value, nitrogen can be automatically supplemented and added, so that the oxygen-free state in the thermal desorption system is ensured to be maintained, and the safety protection function of the thermal desorption system is realized.
Description
Technical Field
The invention relates to the technical field of contaminated soil treatment, in particular to a method and a device for oxygen content of tail gas of a thermal desorption system of organic contaminated soil.
Background
At present, a large number of organic polluted sites such as POPs (persistent organic pollutants), PCBs (polychlorinated biphenyls) and petroleum hydrocarbons exist in China, thermal desorption treatment is a technology widely used for harmless treatment of the polluted soil, when the organic polluted sites are repaired by adopting a thermal desorption technology, a large number of flammable and combustible tail gas can be generated in thermal desorption equipment, the traditional thermal desorption equipment is internally heated, and the tail gas is directly contacted with open fire, so that the oxygen content in the thermal desorption equipment must be strictly controlled to enable fuel to be fully combusted, the thermal desorption equipment is ensured to heat the soil in an anaerobic state, and otherwise, explosion danger can be brought.
At present, the oxygen content in thermal desorption equipment is generally interlocked with a blower, the oxygen content of a system is controlled mainly by the frequency change of the blower, but the oxygen content can be changed by adjusting other parameters, and when the oxygen content of the system is changed greatly, if no other atmosphere protection systems exist, the explosion danger still exists.
However, no report related to an atmosphere protection method and device capable of automatically supplementing nitrogen according to the change of oxygen content in thermal desorption equipment is available at present.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method and a device for the oxygen content of tail gas of a thermal desorption system of organic contaminated soil.
The invention solves the technical problems by the following technical scheme:
the invention discloses a method for controlling the oxygen content of tail gas of a thermal desorption system of organic contaminated soil, which comprises the following operation steps:
1) air purification pretreatment: compressing air by an air compressor, then sending the compressed air into an air purification unit, filtering, dehydrating and deoiling the air by the air purification unit, and then introducing the air into an air storage tank for temporary storage;
2) preparing nitrogen gas: introducing air in an air storage tank into two carbon molecular sieve adsorption towers which can be circularly and alternately changed to realize adsorption and desorption processes, continuously separating nitrogen from the air through the carbon molecular sieve adsorption towers, inputting the nitrogen into a nitrogen buffer tank for temporary storage, and providing nitrogen protection for an organic contaminated soil thermal desorption system through a nitrogen output pipeline;
3) and (3) online nitrogen supplement: install oxygen content analysis appearance in organic contaminated soil thermal desorption system, establish interlocking switch device between the nitrogen gas output pipeline of oxygen content analysis appearance and nitrogen buffer tank, and by PLC control system control interlocking switch device's switching action according to oxygen content analysis appearance's testing result, tail gas after thermal desorption system handles detects when oxygen content is higher than 2% through oxygen content analysis appearance, will trigger the interlocking, open interlocking switch device, make nitrogen gas output pipeline be the on-state, the nitrogen gas in the nitrogen buffer tank then supplyes in the thermal desorption system, detect that the oxygen content is lower than 2%, close interlocking switch device, stop to mend nitrogen.
The air pressure of the air compressor is 0.75-1.0 MPa, the dew point of the water content in the raw material air after air purification pretreatment is less than or equal to-17 ℃, the oil content is less than or equal to 5ppm, and the solid particle size is less than or equal to 0.01 mu m.
The device for controlling the oxygen content of the tail gas of the thermal desorption system of the organic contaminated soil comprises an air purification pretreatment unit, a nitrogen preparation unit and an online nitrogen supplement unit which are connected in sequence, wherein a nitrogen output pipeline of the nitrogen preparation unit is connected with the thermal desorption system of the organic contaminated soil to provide nitrogen protection for the thermal desorption system of the organic contaminated soil.
The air purification pretreatment unit consists of an air compressor, an air buffer tank, an air purification unit and an air storage tank which are sequentially connected and arranged according to the gas direction, wherein the air purification unit consists of a C-level filter, a cold dryer, an A-level filter and an active carbon adsorption tower which are sequentially connected and arranged according to the gas direction; the inlet end of the C-stage filter is connected with an air buffer tank, and the outlet end of the activated carbon adsorption tower is connected with an air storage tank.
The nitrogen preparation unit comprises two carbon molecular sieve adsorption towers connected in parallel, the front end converging pipelines of the two carbon molecular sieve adsorption towers are connected with an air storage tank, the rear end converging pipelines are connected with a nitrogen buffer tank through an H-level filter, the two carbon molecular sieve adsorption towers are controlled by a programmable controller to alternately operate to realize alternate adsorption and desorption, and then nitrogen in the air is continuously separated out, so that the nitrogen is continuously conveyed to the nitrogen buffer tank.
The bottom of the two carbon molecular sieve adsorption towers is provided with an exhaust pipeline, and the exhaust pipeline is provided with a silencer.
The online nitrogen supplementing unit comprises an interlocking switch device and an oxygen content analyzer, the oxygen content analyzer is installed on a tail gas pipeline of the organic contaminated soil thermal desorption system, the interlocking switch device is electrically connected with the oxygen content analyzer, the PLC control system controls the on-off action of the interlocking switch device, and the online nitrogen supplementing into the organic contaminated soil thermal desorption system is realized.
And a one-way throttle valve is arranged on the inlet end pipeline of the nitrogen buffer tank, and a plunger valve, a pressure regulating valve, a flow meter and a nitrogen analyzer which are sequentially connected from front to back are arranged on the outlet end pipeline.
The air compressor is a screw air compressor, and two air compressors are arranged and can be independently controlled.
Compared with the prior art, the invention has the following advantages:
(1) the invention establishes interlocking with the oxygen content analyzer arranged in the thermal desorption treatment system, automatically supplements nitrogen when the oxygen content in the thermal desorption system fluctuates greatly, provides atmosphere protection for the thermal desorption system, can improve the safety protection level of the thermal desorption treatment system to a certain extent, and reduces the explosion risk.
(2) The invention uses two groups of adsorption towers which are connected in parallel, and controls the electromagnetic pneumatic valve through the programmable controller to lead the two groups of adsorption towers to automatically and alternately carry out pressurization adsorption and decompression regeneration, thus completing the separation of nitrogen and oxygen and realizing the continuous acquisition of nitrogen with different purities.
Drawings
FIG. 1 is a process flow diagram of the method for controlling the oxygen content of the tail gas of the thermal desorption system of the organic contaminated soil according to the invention.
FIG. 2 is a schematic structural diagram of the apparatus for controlling the oxygen content of the tail gas of the thermal desorption system for organic contaminated soil according to the present invention.
In the figure: the system comprises an air compressor 1, an air buffer tank 2, a C-grade filter 301, a freeze dryer 302, an A-grade filter 303, an activated carbon adsorption tower 304, an air storage tank 4, a carbon molecular sieve adsorption tower 5-A, a carbon molecular sieve adsorption tower 5-B, a programmable controller 501, a silencer 502, an H-grade filter 6, a nitrogen buffer tank 7, a flowmeter 701, a nitrogen analyzer 702, an interlocking switch device 8 and an oxygen content analyzer 9.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
As shown in figure 1, the method for controlling the oxygen content of the tail gas of the thermal desorption system of the organic contaminated soil comprises the following operation steps:
1) air purification pretreatment: the method comprises the following steps of (1) compressing ambient air by an air compressor, then sending the compressed ambient air into an air purification unit, carrying out pretreatment such as filtration, dehydration and oil removal on raw material air in the air purification unit, controlling the air pressure of the air compressor to be 0.75-1.0 Mpa, and controlling the dew point of the water content in the raw material air to be less than or equal to-17 ℃ after the pretreatment of air purification; the oil content is less than or equal to 5 ppm; the particle size of the solid is less than or equal to 0.01 mu m, and the air after purification pretreatment is introduced into an air storage tank for temporary storage. This is the prerequisite of guaranteeing the normal operating of follow-up pressure swing adsorption preparation nitrogen gas unit.
2) Preparing nitrogen by pressure swing adsorption: introducing the air subjected to purification pretreatment in the step 1 into a carbon molecular sieve adsorption tower, removing impurity components in the air by pressure adsorption by utilizing the characteristics that carbon molecular sieve adsorbents in the carbon molecular sieve adsorption tower have different adsorption capacities under different pressures and selectively adsorb each component of a separated gas mixture under a certain pressure, decompressing and removing the impurities to regenerate the adsorbents, wherein the pressure (normally 0.7-0.8 MPa) of the air during adsorption is controlled within a proper pressure range so as to obtain a better adsorption effect. The carbon molecular sieve adsorption tower applies the principle of pressure swing adsorption, so that the carbon molecular sieve adsorbent filled with micropores selectively adsorbs gas molecules, and nitrogen with the purity of 98-99.99% is obtained. The invention adopts two carbon molecular sieve adsorption towers which are arranged in parallel, and controls the cyclic alternate change of the pressure in the two carbon molecular sieve adsorption towers through the matched electromagnetic pneumatic valve to realize the adsorption and desorption processes, thereby achieving the purpose of continuously separating oxygen and nitrogen from air, and continuously conveying the formed nitrogen to the nitrogen buffer tank.
3) And (3) online nitrogen supplement: install oxygen content analysis appearance in thermal desorption system, establish interlocking switching device between oxygen content analysis appearance and the nitrogen gas output pipeline of nitrogen buffer tank, this interlocking switching device is the pneumatic valve, forms electric connection between pneumatic valve and the oxygen content analysis appearance to by the switching action of PLC control system according to the testing result control pneumatic valve of oxygen content analysis appearance. When the tail gas of the thermal desorption system is detected to have oxygen content higher than 2% through the oxygen content analyzer, the PLC control system controls the valve of the pneumatic valve to be opened, so that the nitrogen in the nitrogen buffer tank is supplemented into the thermal desorption system, and the valve of the pneumatic valve is controlled to be closed until the oxygen content is lower than 2%, and the nitrogen supplementation is stopped.
As shown in FIG. 2, the method can be implemented by using the device shown in FIG. 2, which comprises an air purification pretreatment unit, a nitrogen preparation unit and an on-line nitrogen supplement unit which are connected in sequence.
The air purification pretreatment unit consists of an air compressor 1, an air buffer tank 2, an air purification unit and an air storage tank 4 which are sequentially connected and arranged according to the gas direction, wherein the air purification unit consists of a C-stage filter 301, a cold dryer 302 (namely a cooling dryer), an A-stage filter 303 and an active carbon adsorption tower 304 which are sequentially connected and arranged according to the gas direction; the inlet end of the C-stage filter 301 is connected with the air buffer tank 2, and the outlet end of the activated carbon adsorption tower 304 is connected with the air storage tank 4.
The air compressor 1 can adopt a screw air compressor and is provided with two groups, the two groups of air compressors 1 are connected in parallel, the output ends of the first group of air compressors and the second group of air compressors are respectively connected with a ball valve V1 and a ball valve V2 which can be independently controlled, and the two ball valves V are used for connecting the output ends of the first group of air compressors and the second group of air compressors1、V2The amount of air entering the air buffer tank 2 is controlled.
The C-stage filter 301, the cold dryer 302 and the A-stage filter 303 can also be provided with a plurality of groups, the C-stage filter 301, the cold dryer 302 and the A-stage filter 303 in each group are connected in series, and are respectively connected with the air buffer tank 2 through the C-stage filter 301, and the A-stage filter 303 is connected with the activated carbon adsorption tower 304. According to the air quantity required by the nitrogen preparation unit through pressure swing adsorption, two groups of equipment arranged in parallel can be started at the same time, and can be used for one equipment.
The nitrogen preparation unit comprises a carbon molecular sieve adsorption tower 5-A and a carbon molecular sieve adsorption tower 5-B, the carbon molecular sieve adsorption tower 5-A and the carbon molecular sieve adsorption tower 5-B are connected in parallel, a front converging pipeline of the two carbon molecular sieve adsorption towers is connected with an air storage tank 4, a rear converging pipeline is connected with a nitrogen buffer tank 7 through an H-level filter 6, the two carbon molecular sieve adsorption towers are controlled by a programmable controller 501 to alternately operate to realize alternate adsorption and desorption, and then nitrogen in the air is continuously separated out, so that nitrogen is continuously conveyed to the nitrogen buffer tank 7, and the nitrogen buffer tank 7 provides nitrogen atmosphere protection for the thermal desorption treatment system.
A plunger valve V3 and an electromagnetic pneumatic valve Y1 are arranged on a converging pipeline at the front ends of the carbon molecular sieve adsorption tower 5-A and the carbon molecular sieve adsorption tower 5-B, an electromagnetic pneumatic valve Y2 and an electromagnetic pneumatic valve Y3 which are independently controlled are respectively arranged on an inlet pipeline of the carbon molecular sieve adsorption tower 5-A and an inlet pipeline of the carbon molecular sieve adsorption tower 5-B, a communicated pipeline is connected between the two inlet pipelines, and the electromagnetic pneumatic valve Y4 and the electromagnetic pneumatic valve Y5 are arranged on the pipeline; an outlet pipeline of the carbon molecular sieve adsorption tower 5-A and an outlet pipeline of the carbon molecular sieve adsorption tower 5-B are respectively provided with an independently controlled electromagnetic pneumatic valve Y6 and an electromagnetic pneumatic valve Y7, a communicated pipeline is connected between the two outlet pipelines, and a needle valve V4 is arranged on the pipeline; an electromagnetic pneumatic valve Y8 is arranged on a converging pipeline at the rear ends of the two carbon molecular sieve adsorption towers; the inlet end of the nitrogen buffer tank 7 is provided with a one-way throttle valve V5, and the outlet end is connected with a nitrogen output pipeline.
The two carbon molecular sieve adsorption towers of the invention control the action sequence of the electromagnetic pneumatic valve by the programmable controller 501 to realize alternate adsorption and desorption, thereby continuously conveying nitrogen to the nitrogen buffer tank.
The specific control process is as follows:
clean compressed air sent by the air purification pretreatment unit manually adjusts the flow rate of inlet air through a plunger valve V3, then enters a tower body from the lower part of a carbon molecular sieve adsorption tower 5-A through electromagnetic pneumatic valves Y1 and Y2, is adsorbed by a carbon molecular sieve bed layer in the adsorption tower and is gradually pushed upwards, in the process, oxygen molecules in the air are adsorbed in micropores of the carbon molecular sieve, a large amount of nitrogen and a small amount of oxygen flow out from the upper part of the tower, and then enters a nitrogen buffer tank 7 through the electromagnetic pneumatic valves Y6, Y8 and a one-way throttle valve V4, and the process is the adsorption nitrogen making of the 5-A tower. Meanwhile, the oxygen molecules adsorbed in the carbon molecular sieve adsorption tower 5-B are exhausted through the electromagnetic pneumatic valve Y5 and the silencer 10, namely the 5-B tower is desorbed and deoxidized. Thereby realizing continuous nitrogen supply when the two towers work alternately. When the 5-A tower works for a period of time and the adsorption of the carbon molecular sieve in the adsorption tower to oxygen is close to saturation, the adsorption tower stops adsorbing in time. At the moment, the electromagnetic pneumatic valves Y1, Y4, Y5 and Y8 are all in a closed state, the electromagnetic pneumatic valves Y2, Y3, Y6 and Y7 are simultaneously in an open state, pressure equalization is carried out on the two adsorption towers of the 5-A tower and the 5-B tower, the pressure equalization has the effect of transferring gas (the gas has less oxygen content) in the external gas phase of the 5-A tower to the 5-B tower for reuse, the pressure equalization time is generally 1-2 seconds, and the adsorption state of the 5-B tower and the desorption state of the 5-A tower are switched after the pressure equalization. At this time, the compressed air enters the lower part of the 5-B adsorption tower through the electromagnetic pneumatic valves Y1 and Y3. Adsorbing by a carbon molecular sieve bed layer in a 5-B adsorption tower. The separated nitrogen enters a nitrogen storage tank 7 through electromagnetic pneumatic valves Y7, Y8 and V3, namely the 5-B adsorption tower is used for adsorbing and producing nitrogen. In order to completely release the residual oxygen in the adsorption tower after desorption from the adsorption tower into the air, namely clean, a part of nitrogen is shunted from the top of the adsorption tower in the adsorption work, the normal flow is 8.5% -10% of the nitrogen production amount, and the nitrogen enters the adsorption tower for desorption to be blown and swept after being controlled by a needle valve V4, so that the diffusion speed of the oxygen to the outside of the adsorption tower is accelerated until the next cycle. Thereby realizing the alternate adsorption and desorption of the two carbon molecular sieve adsorption towers, namely forming the continuous and continuous nitrogen conveying to the nitrogen buffer tank 7.
The online nitrogen supplementing unit comprises a plunger valve V6, a pressure regulating valve V7, a flow meter 701, a nitrogen analyzer 702, an interlocking switch device 8 and an oxygen content analyzer 9, wherein the oxygen content analyzer 9 is installed on a tail gas pipeline of the organic contaminated soil thermal desorption system, the plunger valve V6, the pressure regulating valve V7, the flow meter 701, the nitrogen analyzer 702 and the interlocking switch device 8 are sequentially installed on a nitrogen output pipeline of the gas buffer tank 7 from front to back, the interlocking switch device 8 is electrically connected with the oxygen content analyzer 9, and a PLC control system controls the on-off action of the interlocking switch device 8 according to the detection result of the oxygen content analyzer, so that the online automatic nitrogen supplementing into the thermal desorption system is realized.
The oxygen content analyzer 7 is used for detecting the oxygen content in the thermal desorption tail gas, and the measured oxygen content value can be remotely displayed, alarmed and recorded from a PLC control system.
The air buffer tank 2 is provided with a pressure test point P1, the two carbon molecular sieve adsorption towers 5 are respectively provided with a pressure test point P4 and a pressure test point P3, the nitrogen buffer tank 7 is provided with a pressure test point P5, and a pipeline between the air storage tank 4 and the carbon molecular sieve adsorption towers 5 is provided with a pressure test point P2.
A silencer 502 is arranged on a connecting pipeline at the bottom of the two carbon molecular sieve adsorption towers 5.
The air buffer tank 2 and the air storage tank 4 are both provided with a sewage discharge valve, so that sewage discharge is facilitated.
The C-level filter, the A-level filter and the H-level filter are all provided with oil-water recovery devices.
The working process of the device of the invention is as follows:
the air compressor obtains compressed air supply by taking ambient air as a raw material, has the main functions of providing enough air quantity and relatively constant air supply pressure (0.75-0.85 MPa), is one of necessary conditions for ensuring the normal work of a system, and the compressed air discharged from the air compressor 1 enters the air buffer tank 2 for temporary storage, has the main functions of controlling the overload operation of the air compressor 1 and preventing the pressure fluctuation of the raw material air, and also has the function of depositing partial oil and water in the compressed air. Compressed air sends into the air purification unit through air buffer tank 2, filters raw materials air in the air purification unit, preliminary treatment such as dehydration, deoiling, and cold machine 302 main function is the dewatering to ensure that the water content of the compressed air after cold machine drying process is up to standard. The C-stage filter 301, the A-stage filter 303 and the activated carbon adsorption tower 304 are matched equipment necessary for achieving water removal, oil removal and solid particle removal in the air source purification treatment process and enabling the quality of an air source entering the carbon molecular sieve adsorption tower 5 to reach a standard, the functions of all stages are different, the filtration treatment precision of the C-stage filter 301 is 3 mu, and the main function is primary oil-water filtration; the treatment precision of the A-stage filter 303 is 0.01 mu, and the main function is micro oil removal; the main function of the activated carbon adsorption tower 304 is to further remove oil and water. The purified air source enters the air storage tank 4 for temporary storage. The main function of the air storage tank 4 is to provide continuous and stable clean air for the nitrogen preparation unit by the subsequent pressure swing adsorption, so as to ensure that the nitrogen preparation unit by the pressure swing adsorption canThe unit for preparing nitrogen by pressure swing adsorption has two carbon molecular sieve adsorption towers 5 connected in parallel, and its main function is to control the electromagnetic pneumatic valve Y by means of programmable controller1-Y8The action sequence of the two towers can lead the two towers to alternately adsorb and desorb, thereby ensuring that the system continuously prepares nitrogen with certain purity, the nitrogen from the carbon molecular sieve adsorption tower 5 is further purified by an H-level filter (with the processing precision of 0.001 mu) and then is conveyed to a nitrogen buffer tank 7, and the nitrogen buffer tank 7 has certain capacity and mainly has the function of storing nitrogen. When the tail gas after the thermal desorption system is processed detects that the oxygen content is higher than 2% through the oxygen content analyzer 9, the interlocking switch device 8 can be automatically opened, and the nitrogen in the nitrogen buffer tank 7 passes through the plunger valve V6Pressure regulating valve V7And the flow meter 701 and the nitrogen analyzer 702 can be continuously and stably supplemented into the thermal desorption system so as to ensure that the oxygen content in the thermal desorption system meets the safety requirement of the system.
The following are examples of the use of the present invention:
example one:
the method comprises the following steps of performing thermal desorption treatment by taking the ground oil sludge of a certain oil field as an object, directly heating the oil sludge by burning natural gas in thermal desorption equipment, controlling the temperature range of the oil sludge in the thermal desorption equipment to be 300-500 ℃, controlling the retention time to be 18min, supplying air required by combustion of the natural gas by an air blower, and controlling the ratio (volume ratio) of the natural gas to the air to be 1 by a proportional valve: when 10, the oxygen content in the thermal desorption equipment is shown to be 1.70% by the oxygen measuring instrument, and the site and the PLC system do not give an alarm, and when the ratio (volume ratio) of the natural gas to the air is adjusted to be 1: 10.5, the oxygen content in the thermal desorption equipment that the appearance shows of oxygen is 1.85%, and on-the-spot and PLC system all report to the police, is 1 when adjusting the proportion (the volume ratio) of natural gas and air: and 12, the oxygen measuring instrument displays that the oxygen content in the thermal desorption equipment is 2.3%, the interlocking switch device is triggered to be opened, the nitrogen in the nitrogen buffer tank is supplemented into the thermal desorption equipment until the oxygen content is lower than 2%, and the interlocking switch device is closed to stop nitrogen supplementation.
Example two:
the method comprises the following steps of performing thermal desorption treatment by taking tank bottom oil sludge of a certain oil field as an object, directly heating the oil sludge by burning natural gas in thermal desorption equipment, controlling the temperature range of the oil sludge in the thermal desorption equipment to be 300-500 ℃, controlling the retention time to be 20min, supplying air required by natural gas combustion by an air blower, and controlling the ratio (volume ratio) of the natural gas to the air to be 1 by a proportional valve: when 9.5 hours, the oxygen meter shows that the oxygen content in the thermal desorption equipment is 1.60%, and the site and the PLC system do not give an alarm, and when the ratio (volume ratio) of the natural gas to the air is adjusted to be 1: during 11, the oxygen content that the appearance shows thermal desorption equipment is 1.90% to the oxygen detector, and on-the-spot and PLC system all report to the police, is 1 when adjusting the proportion (the volume ratio) of natural gas and air: and when 12.5 hours, the oxygen measuring instrument displays that the oxygen content in the thermal desorption equipment is 2.5 percent, the interlocking switch device is triggered to be opened, the nitrogen in the nitrogen buffer tank is supplemented into the thermal desorption equipment until the oxygen content is lower than 2 percent, and the interlocking switch device is closed to stop nitrogen supplementation.
Example three:
carrying out thermal desorption treatment by taking oil sludge sand of a certain oil field as an object, directly heating oil sludge in thermal desorption equipment by burning natural gas, controlling the temperature range of the oil sludge in the thermal desorption equipment to be 300-500 ℃, controlling the retention time to be 20min, supplying air required by natural gas combustion by an air blower, and controlling the ratio (volume ratio) of the natural gas to the air to be 1 by a proportional valve: when 9.0, the oxygen measuring instrument shows that the oxygen content in the thermal desorption equipment is 1.50%, the site and the PLC system do not give an alarm, and when the ratio (volume ratio) of the natural gas to the air is adjusted to be 1: 11.5, the oxygen content in the thermal desorption equipment that the appearance shows of oxygen is 1.95%, and on-the-spot and PLC system all report to the police, is 1 when adjusting the proportion (the volume ratio) of natural gas and air: and 13, the oxygen measuring instrument displays that the oxygen content in the thermal desorption equipment is 2.7%, the interlocking switch device is triggered to be opened, the nitrogen in the nitrogen buffer tank is supplemented into the thermal desorption equipment until the oxygen content is lower than 2%, and the interlocking switch device is closed to stop nitrogen supplementation.
Claims (9)
1. A method for controlling the oxygen content of tail gas of a thermal desorption system of organic contaminated soil is characterized by comprising the following operation steps:
1) air purification pretreatment: compressing air by an air compressor, then sending the compressed air into an air purification unit, filtering, dehydrating and deoiling the air by the air purification unit, and then introducing the air into an air storage tank for temporary storage;
2) preparing nitrogen gas: introducing air in an air storage tank into two carbon molecular sieve adsorption towers which can be circularly and alternately changed to realize adsorption and desorption processes, continuously separating nitrogen from the air through the carbon molecular sieve adsorption towers, inputting the nitrogen into a nitrogen buffer tank for temporary storage, and providing nitrogen protection for an organic contaminated soil thermal desorption system through a nitrogen output pipeline;
3) and (3) online nitrogen supplement: install oxygen content analysis appearance in organic contaminated soil thermal desorption system, establish interlocking switch device between the nitrogen gas output pipeline of oxygen content analysis appearance and nitrogen buffer tank, and by PLC control system control interlocking switch device's switching action according to oxygen content analysis appearance's testing result, tail gas after thermal desorption system handles detects when oxygen content is higher than 2% through oxygen content analysis appearance, will trigger the interlocking, open interlocking switch device, make nitrogen gas output pipeline be the on-state, the nitrogen gas in the nitrogen buffer tank then supplyes in the thermal desorption system, detect that the oxygen content is lower than 2%, close interlocking switch device, stop to mend nitrogen.
2. The method for controlling the oxygen content of the tail gas of the thermal desorption system of the organic contaminated soil as claimed in claim 1, wherein the air pressure of the air compressor is 0.75-1.0 MPa, the dew point of the water content in the raw material air after air purification pretreatment is less than or equal to-17 ℃, the oil content is less than or equal to 5ppm, and the solid particle size is less than or equal to 0.01 μm.
3. The utility model provides a device for controlling organic contaminated soil thermal desorption system tail gas oxygen content which characterized in that, the device is including the air purification preprocessing unit that meets in proper order, preparation nitrogen gas unit and online supplementary nitrogen gas unit, and the nitrogen gas output pipeline of preparation nitrogen gas unit is connected with organic contaminated soil thermal desorption system, provides nitrogen protection for organic contaminated soil thermal desorption system.
4. The device for controlling the oxygen content of the tail gas of the thermal desorption system of the organic contaminated soil according to claim 3, wherein the air purification pretreatment unit comprises an air compressor, an air buffer tank, an air purification unit and an air storage tank which are sequentially connected and arranged according to the gas direction, and the air purification unit comprises a C-grade filter, a cold dryer, an A-grade filter and an activated carbon adsorption tower which are sequentially connected and arranged according to the gas direction; the inlet end of the C-stage filter is connected with an air buffer tank, and the outlet end of the activated carbon adsorption tower is connected with an air storage tank.
5. The device according to claim 3 or 4, wherein the nitrogen preparation unit comprises two carbon molecular sieve adsorption towers connected in parallel, a front converging pipeline of the two carbon molecular sieve adsorption towers is connected with an air storage tank, a rear converging pipeline of the two carbon molecular sieve adsorption towers is connected with the nitrogen buffer tank through an H-stage filter, and the two carbon molecular sieve adsorption towers are controlled by the programmable controller to alternately operate to realize alternate adsorption and desorption, so that nitrogen in the air is continuously separated, and the nitrogen is continuously conveyed to the nitrogen buffer tank.
6. The apparatus according to claim 5, wherein the bottom of each of the two carbon molecular sieve adsorption towers is provided with an exhaust pipe, and the exhaust pipe is provided with a silencer.
7. The device for controlling the oxygen content of the tail gas of the thermal desorption system of the organic contaminated soil according to claim 3 or 4, wherein the on-line nitrogen supplementing unit comprises an interlocking switch device and an oxygen content analyzer, the oxygen content analyzer is installed on a tail gas pipeline of the thermal desorption system of the organic contaminated soil, the interlocking switch device is installed on a nitrogen output pipeline of the nitrogen preparation unit, the interlocking switch device is electrically connected with the oxygen content analyzer, and the PLC control system controls the on-off action of the interlocking switch device according to the detection result of the oxygen content analyzer.
8. The device for controlling the oxygen content of the tail gas of the thermal desorption system of the organic contaminated soil as claimed in claim 5, wherein the inlet end pipeline of the nitrogen buffer tank is provided with a one-way throttle valve, and the outlet end pipeline is sequentially provided with a plunger valve, a pressure regulating valve, a flow meter and a nitrogen analyzer from front to back.
9. The device for controlling the oxygen content of the tail gas of the thermal desorption system of the organic contaminated soil as claimed in claim 4, wherein: the air compressor is a screw air compressor, and two air compressors are arranged and can be independently controlled.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113369294A (en) * | 2021-06-10 | 2021-09-10 | 上海环土环境科技有限公司 | Polluted soil ex-situ low-carbon circulating thermal desorption system |
| CN115121597A (en) * | 2022-06-29 | 2022-09-30 | 国网河北省电力有限公司电力科学研究院 | Vehicle-mounted van-type continuous microwave soil solid waste treatment equipment |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113369294A (en) * | 2021-06-10 | 2021-09-10 | 上海环土环境科技有限公司 | Polluted soil ex-situ low-carbon circulating thermal desorption system |
| CN115121597A (en) * | 2022-06-29 | 2022-09-30 | 国网河北省电力有限公司电力科学研究院 | Vehicle-mounted van-type continuous microwave soil solid waste treatment equipment |
| CN115121597B (en) * | 2022-06-29 | 2023-08-22 | 国网河北省电力有限公司电力科学研究院 | Vehicle-mounted van-type continuous microwave soil solid waste treatment equipment |
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