CN112065546A - Method for reducing content of polycyclic aromatic hydrocarbon substances in micron-sized particles of diesel engine - Google Patents
Method for reducing content of polycyclic aromatic hydrocarbon substances in micron-sized particles of diesel engine Download PDFInfo
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- CN112065546A CN112065546A CN202010921485.3A CN202010921485A CN112065546A CN 112065546 A CN112065546 A CN 112065546A CN 202010921485 A CN202010921485 A CN 202010921485A CN 112065546 A CN112065546 A CN 112065546A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N9/00—Electrical control of exhaust gas treating apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
- F01N13/0093—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are of the same type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/01—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust by means of electric or electrostatic separators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
- F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
- F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
- F01N3/0222—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0821—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with particulate filters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
- F01N3/0835—Hydrocarbons
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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- General Engineering & Computer Science (AREA)
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- Exhaust Gas After Treatment (AREA)
Abstract
The invention discloses a method for reducing the content of polycyclic aromatic hydrocarbon substances in micron-sized particles of a diesel engine, which comprises the following steps,By the real-time pressure P in the cylinder along with the crank angleVariation curve of (2) and in-cylinder real-time temperature T along with crank angleJudging the combustion state of the diesel engine cylinder by the change curve, and spraying alcohol oxygen-containing fuel, dimethyl ether or dimethyl carbonate or introducing oxygen ions at different periods; step two, judging the concentration of micron-sized particles with the particle size of less than 2.5 microns in the exhaust process, performing electrostatic adsorption treatment, high-temperature oxidation and particle trap trapping and filtering, and controlling polycyclic aromatic hydrocarbon in the micron-sized particles; and step three, carrying out plasma treatment, OH free radical heating treatment and activated carbon adsorption on the exhaust gas. The method has obvious effect of reducing the content of polycyclic aromatic hydrocarbon in micron-sized particles of engine exhaust.
Description
Technical Field
The invention relates to a method for reducing the emission of vehicle particles, in particular to a method for reducing the content of polycyclic aromatic hydrocarbon substances in micron-sized particles of a diesel engine.
Background
Currently, methods for reducing particulate matter emission, such as Low Temperature Combustion (LTC) and particulate filter (DPF), are proposed for diesel particulate matter from two aspects of combustion control and exhaust gas aftertreatment. The novel combustion mode (such as LTC) can avoid the temperature and equivalence ratio area where a large amount of particulate matters are generated by optimizing the combustion process, and the emission of the particulate matters is greatly reduced. However, on one hand, the novel combustion mode has the problem of narrow working condition range, and on the other hand, the combustion optimization control has limited effect on reducing the emission of micro-nano-scale particles. The trapping efficiency of the particulate matter emission of the particulate trap (DPF) can reach about 90%, and the particulate matter emission can be effectively reduced. However, the particulate trap has problems in use, such as an increase in exhaust back pressure when a certain amount of trapped particulates is reached, a decrease in trapping efficiency, and the need for trap regeneration. In addition, the efficiency of trapping micro-nano particles depends on the trapping principle, structure, material and other factors of the trap, and the micro-nano particles cannot be efficiently trapped.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for reducing the content of polycyclic aromatic hydrocarbon substances in micron-sized particles of a diesel engine, which reduces the content of polycyclic aromatic hydrocarbon in the micron-sized particles which are difficult to control combustion and difficult to trap by an aftertreatment device, thereby reducing the harm of the absorbable micron-sized particles to human bodies.
The technical scheme of the invention is as follows: a method for reducing the content of polycyclic aromatic hydrocarbon substances in micron-sized particles of a diesel engine comprises the following steps:
step one, real-time pressure P in a cylinder is used for measuring the angle of a crankshaftVariation curve of (2) and in-cylinder real-time temperature T along with crank angleJudging the combustion state of the diesel engine in the cylinder by the change curve, and spraying alcohol oxygenated fuel when the combustion is in a fast combustion period and the temperature in the cylinder exceeds a first temperature threshold value; when the combustion is in a slow combustion period and the oxygen concentration in the cylinder is not higher than a first oxygen concentration threshold value, oxygen-containing fuel dimethyl ether or dimethyl carbonate is injected; introducing oxygen ions when the combustion is in a post combustion period and the temperature in the cylinder is not lower than a second temperature threshold;
step two, judging the concentration of micron-sized particles with the particle size smaller than 2.5 microns in the exhaust gas obtained in the step one, and performing electrostatic adsorption treatment on the exhaust gas when the concentration of the micron-sized particles exceeds a first particle concentration threshold value, or else, sequentially trapping and filtering by a first particle trap, a second particle trap and a third particle trap; judging the fractal dimension of the particles of the exhaust gas after electrostatic adsorption treatment, spraying the atomized methanol and dimethyl ether oxygen-containing mixed fuel into the exhaust gas when the fractal dimension exceeds a first threshold value, then carrying out high-temperature oxidation, or directly carrying out high-temperature oxidation, and then sequentially trapping and filtering by a second particle trap and a third particle trap;
and step three, carrying out plasma treatment, OH free radical heating treatment and activated carbon adsorption on the exhaust gas in the step two.
Further, the real-time pressure P in the cylinder is along with the crank angleThe time when the variation curve of the pressure difference is separated from the cylinder pressure curve of the diesel engine under the condition of non-combustion is a fast combustion period, the time when the combustion is in the fast combustion period and the real-time pressure P in the cylinder rises and an inflection point appears is a slow combustion period, and the time when the combustion is in the slow combustion period and the temperature T in the cylinder rises and the inflection point appears is a post-combustion period.
Further, when the oxygen concentration in the cylinder is lower than a first oxygen concentration threshold value and higher than a second oxygen concentration threshold value, oxygen-containing fuel ethanol or n-butanol is sprayed, when the oxygen concentration in the cylinder is not higher than the second oxygen concentration threshold value, oxygen-containing fuel dimethyl carbonate is sprayed, and the first oxygen concentration threshold value is larger than the second oxygen concentration threshold value.
Further, the third step comprises performing plasma treatment on the exhaust gas when the concentration of the gaseous aromatic hydrocarbon is greater than a first aromatic hydrocarbon concentration threshold value according to the concentration of the gaseous aromatic hydrocarbon in the exhaust gas of the engine; when the concentration of the gaseous aromatic hydrocarbon is not more than the first aromatic hydrocarbon concentration threshold value but more than the second aromatic hydrocarbon concentration threshold value, carrying out OH free radical heating treatment on the exhaust gas; when the concentration of the gaseous aromatic hydrocarbon is not greater than the second aromatic hydrocarbon concentration threshold value, performing activated carbon adsorption on the exhaust gas; and after the exhaust gas is treated, when the concentration of the gaseous aromatic hydrocarbon is greater than a third aromatic hydrocarbon concentration threshold value, the second step is carried out again, wherein the first aromatic hydrocarbon concentration threshold value is greater than a second aromatic hydrocarbon concentration threshold value, and the second aromatic hydrocarbon concentration threshold value is greater than the third aromatic hydrocarbon concentration threshold value.
Further, after the electrostatic adsorption treatment is carried out on the exhaust gas, whether the voltage drop of the electrostatic adsorption is larger than a first voltage drop threshold value is judged, if so, the reverse voltage is loaded and then the electrostatic adsorption is directly trapped and filtered by a third particle trap, if not, the electrostatic adsorption treatment is carried out again and whether the voltage drop of the electrostatic adsorption is larger than a second voltage drop threshold value is judged, if so, the step of judging the fractal dimension of the particles is carried out, and if not, the step of sequentially trapping and filtering is carried out by the first particle trap, the second particle trap and the third particle trap.
Further, the first particle catcher is made of honeycomb ceramics, and the structural parameters are as follows: the average pore diameter is 22-25 μm, the porosity is 72-76%, the wall thickness is 7-8mil, and the length-to-diameter ratio is 0.5-0.7; the second particle catcher is made of honeycomb ceramics, and the structural parameters are as follows: average pore diameter is 15-18 μm, porosity is 65-68%, wall thickness is 10-12mil, and length-to-diameter ratio is 0.9-1.1; the third particle catcher is made of honeycomb ceramics, and the structural parameters are as follows: the average pore diameter is 10-12 μm, the porosity is 58-62%, the wall thickness is 14-16mil, and the length-to-diameter ratio is 1.3-1.5.
The technical scheme provided by the invention has the advantages that: the method of combined control obviously reduces the content of polycyclic aromatic hydrocarbon substances of micron-sized particulate matters of the diesel engine by controlling the injection of oxygen-containing fuel in the combustion process, performing plasma treatment, OH free radical heating treatment and activated carbon adsorption on the exhaust gas in the exhaust stage, then performing electrostatic adsorption, high-temperature oxidation treatment and finally trapping by a particle trap.
Drawings
FIG. 1 is a flow chart of the method steps of the present invention.
FIG. 2 is a schematic flow chart of the steps of the method of the present invention.
FIG. 3 is a schematic diagram of the exhaust path in step two of the method of the present invention.
FIG. 4 is a schematic flow chart of the method steps of the present invention.
FIG. 5 is a schematic view of the exhaust path in step three of the method of the present invention.
FIG. 6 is a graph showing the total polycyclic aromatic hydrocarbon emission concentration of the present invention and the comparative example.
Detailed Description
The present invention is further described in the following examples, which are intended to be illustrative only and not to be limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalent modifications thereof which would occur to persons skilled in the art upon reading the present specification and which are intended to be within the scope of the present invention as defined in the appended claims.
The specific method for reducing the content of polycyclic aromatic hydrocarbon substances in micron-sized particles of the diesel engine mainly comprises the following three steps: step one, real-time pressure P in a cylinder is used for measuring the angle of a crankshaftVariation curve of (2) and in-cylinder real-time temperature T along with crank angleThe combustion state judgment of the diesel engine cylinder with the change curve intervenes in different combustion stages, and aims to mainly reduce polycyclic aromatic hydrocarbon formed in the combustion process; step two, judging the concentration of micron-sized particles with the particle size of less than 2.5 microns in the exhaust process to control polycyclic aromatic hydrocarbon in the micron-sized particles; and step three, carrying out plasma treatment, OH free radical heating treatment and activated carbon adsorption on the exhaust gas.
Specifically, referring to fig. 1, a cylinder pressure curve (pure compression line) of a diesel engine without combustion is a known parameter, and the first step includes the following steps:
1. detecting whether to spray oil
a) If so, perform "step 2".
b) If not, "no operation".
2. The fuel injection quantity is recorded and then "step 3" is performed.
3. Recording the real-time pressure P in the cylinder along with the crank angleIs performed (by means of a pressure sensor installed in the cylinder), and then "step 4" is performed.
a) If so, step 5 is executed and the in-cylinder pressure P1 at this time is recorded.
b) If not, determining that the combustion is in a stagnation period, and returning to the step 3.
5. It is determined that "combustion is in/in the rapid combustion period", and then "step 6" and "step 7" are performed simultaneously.
6. Step 9 is entered after waiting for the inflection point of the pressure curve (after reaching the maximum value, starting to decrease).
7. Detecting the temperature in the cylinder, and judging whether the temperature in the cylinder is higher than 1700K:
a) if so, go to "step 8".
b) If not, "no operation".
8. The alcohol oxygenated fuel methanol or ethanol is injected in an amount of 3% of the initial fuel volume injection amount and then returns to step 7.
9. It is determined that "combustion is in/in the slow combustion period", and then "step 10" and "step 11" are performed simultaneously.
10. Waiting temperature profileStep 15 is entered after the inflection point (after reaching the maximum, starting to descend) appears.
11. Detecting the oxygen concentration in the cylinder by using an oxygen sensor, and judging whether the oxygen concentration is higher than 21 percent or not
a) If so, "no operation";
b) if not, go to "step 12".
12. Judging whether the oxygen concentration is higher than 19%
a) If yes, go to step 13;
b) if not, go to "step 14".
13. And injecting the oxygenated fuel dimethyl ether, wherein the injection amount is 3% of the initial fuel volume injection amount.
14. The oxygenate dimethyl carbonate was injected in an amount of 5% of the initial fuel volume injection.
15. It is determined that "combustion is in/during the post combustion period", and then "step 16" and "step 17" are performed simultaneously.
16. And (4) waiting for the in-cylinder pressure to be less than P1 to indicate that the combustion process is ended, and ending the step one process.
17. Judging whether the temperature in the cylinder is lower than 2000K:
a) if so, "no operation".
b) If not, proceed to "step 18".
18. Passing through an oxygen ion generator, introducing oxygen ions with a concentration of not less than 3000 ten thousand/cm3。
Referring to FIGS. 2 and 3, in the second step, the concentration of the micron-sized particles with a particle size of less than 2.5 μm is determined to control the polycyclic aromatic hydrocarbon in the micron-sized particles
1. Detecting the particle size concentration distribution condition of the particles in the exhaust by adopting a particle size spectrometer 1 (the particle size detection range is 5 nm-10 mu m), and judging whether the concentration of micron-sized particles with the particle size of less than 2.5 mu m is more than 1.0 multiplied by 103Per cm3”:
a) If so, the exhaust gas is introduced into the "first exhaust passage L1" through the first flow rate control valve F1, and "step 2" is performed.
b) If not, the exhaust gas is introduced into the "seventh exhaust passage L7" through the first flow rate control valve F1, and "step 3" is performed.
2. The particles are charged. The exhaust gas passes through a particulate matter electrostatic loading device (charging device) to load the particulate matter in the exhaust gas with electric charges. (the greater the particle size of the particles, the greater the charge that can be loaded.) then "step 4" is performed.
3. The exhaust gas passes through a first particle catcher B1, the first particle catcher B1 is made of honeycomb ceramics, and the specific structural parameters are as follows: the average pore diameter is 22-25 μm, the porosity is 72-76%, the wall thickness is 7-8mil, and the length-to-diameter ratio is 0.5-0.7. Then "step 17" is performed.
4. And (3) performing electrostatic adsorption on micron-sized particles in the exhaust gas by adopting electrostatic adsorption (an electric field loading device) with the electrostatic voltage range of 5-100V, and then performing step 5.
5. The actual voltage in the first exhaust passage L1 is detected, and whether the voltage drop is larger than 15% or not is determined in comparison with the electrostatic adsorption (electric field application device) voltage:
a) if so, go to "step 6".
b) If not, go to "step 7".
6. A reverse voltage is applied to the electrostatic adsorption in a voltage range of 5-100V, and at this time, the second flow control valve F2 controls the flow of the exhaust gas to the second exhaust passage L2, and then "step 18" is performed.
7. The second flow control valve F2 controls the flow of exhaust gas to the third exhaust passage L3, and then "step 8" is performed.
8. And (3) performing electrostatic adsorption on micron-sized particles in the exhaust gas by adopting electrostatic adsorption (an electric field loading device) with the electrostatic voltage range of 200-2000V, and then performing step 9.
9. The actual voltage in the third exhaust passage L3 is detected, and whether the voltage drop is larger than 10% or not is determined in comparison with the electrostatic adsorption (field application device) voltage:
a) if so, go to "step 10".
b) If not, go to "step 11".
10. A reverse voltage is applied to the electrostatic adsorption in the voltage range of 200-2000V, at this time, the third flow control valve F3 controls the flow of the exhaust gas to the fourth exhaust passage L4, and then "step 12" is performed.
11. The third flow rate control valve F3 controls the flow of exhaust gas to the seventh exhaust passage L7, and then "step 3" is performed.
12. Detecting the scattering intensity of the exhaust particles by adopting an X-ray scattering detection method, calculating the fractal dimension of the particles through the scattering intensity, and judging whether the fractal dimension is greater than 2.0':
a) if so, (indicating that the surface has a high degree of surface irregularities and is likely to adsorb PAH, followed by oxidation) the "step 13" is performed.
b) If not, the "step 14" is performed (directly trapping).
13. The fourth flow control valve F4 controls the flow of exhaust gas to the fifth exhaust passage L5, and then proceeds to "step 15".
14. The fourth flow control valve F4 controls the flow of exhaust gas to the sixth exhaust passage L6, and then proceeds to "step 16".
15. And spraying the atomized oxygen-containing mixed fuel of methanol and dimethyl ether into the tail gas, and then carrying out step 16.
16. The tail gas is heated to 800 ℃ by adopting an electric heating method, exhaust particulate matters are subjected to high-temperature oxidation, and then the step 17 is carried out.
17. The exhaust gas passes through a second particle catcher B2, the second particle catcher B2 is made of honeycomb ceramics, and the specific structural parameters are as follows: average pore diameter of 15-18 μm, porosity of 65-68%, wall thickness of 10-12mil, and length-to-diameter ratio of 0.9-1.1. Then "step 18" is performed.
18. The exhaust gas passes through a third particle catcher B3, the third particle catcher B3 is made of honeycomb ceramics, and the specific structural parameters are as follows: the average pore diameter is 10-12 μm, the porosity is 58-62%, the wall thickness is 14-16mil, and the length-to-diameter ratio is 1.3-1.5. Then "step 19" is performed.
19. And (4) exhausting the exhaust gas.
Referring to fig. 4 and 5, the third step of controlling the gaseous polycyclic aromatic hydrocarbon in the exhaust process by plasma treatment, OH radical heating treatment and activated carbon adsorption on the exhaust gas according to the concentration of the gaseous aromatic hydrocarbon in the exhaust gas includes the following steps:
1. detecting the concentration m of the gaseous aromatic hydrocarbon in the exhaust gas by adopting a chromatography-mass spectrometry combined method, and judging whether the concentration m is more than 300 mg/L:
a) if so, go to "step 2".
b) If not, then "judge whether the concentration m is greater than 200 mg/L":
if so, go to "step 3".
If not, go to "step 4".
2. The fifth flow control valve F5 introduces the exhaust gas into the eighth exhaust passage L8, treats the gaseous polycyclic aromatic hydrocarbon in the exhaust gas by plasma, and then proceeds to "step 5".
3. The fifth flow control valve F5 introduces the exhaust gas into the ninth exhaust passage L9, treats the gaseous polycyclic aromatic hydrocarbons in the exhaust gas by OH radical heating treatment, and then proceeds to "step 5".
4. The fifth flow control valve F5 introduces the exhaust gas into the tenth exhaust passage L10, treats the gaseous polycyclic aromatic hydrocarbons in the exhaust gas by activated carbon adsorption, and then proceeds to "step 5".
5. Detecting and judging whether the concentration m of the gaseous aromatic hydrocarbon is more than 100 mg/L:
a) if so, go to "step 6".
b) If not, go to "step 7".
6. The sixth flow control valve F6 directs the exhaust gas into the return path L11, returning the exhaust gas to the original exhaust port.
7. And (4) exhausting the exhaust gas.
Taking a certain diesel engine as an example, the content of polycyclic aromatic hydrocarbons such as naphthalene, phenanthrene, pyrene, benzopyrene and the like in the micron-sized particulate matters in the exhaust gas is respectively measured without any technical measures, by adopting low temperature co-fired ceramic (LTC), by adopting a particle trap (DPF) and by adopting the method for reducing the content of polycyclic aromatic hydrocarbons in the micron-sized particulate matters of the diesel engine designed by the invention, and the result is shown in fig. 6. The diesel engine has a certain effect on reducing the content of the polycyclic aromatic hydrocarbon substances of the micron-sized particles by adopting low temperature co-fired ceramic (LTC) and a particle trap (DPF), and after the scheme for reducing the content of the polycyclic aromatic hydrocarbon substances of the micron-sized particles is adopted, the content of the polycyclic aromatic hydrocarbon substances of the micron-sized particles is further reduced compared with the content of the polycyclic aromatic hydrocarbon substances of the micron-sized particles in the low temperature co-fired ceramic (LTC) and the particle trap (DPF). The scheme of the invention has obvious effect of reducing the content of polycyclic aromatic hydrocarbon substances in micron-sized particles of the diesel engine.
Claims (6)
1. A method for reducing the content of polycyclic aromatic hydrocarbon substances in micron-sized particles of a diesel engine is characterized by comprising the following steps:
step one, real-time pressure P in a cylinder is used for measuring the angle of a crankshaftVariation curve of (2) and in-cylinder real-time temperature T along with crank angleJudging the combustion state of the diesel engine in the cylinder by the change curve, and spraying alcohol oxygenated fuel when the combustion is in a fast combustion period and the temperature in the cylinder exceeds a first temperature threshold value; when the combustion is in a slow combustion period and the oxygen concentration in the cylinder is not higher than a first oxygen concentration threshold value, oxygen-containing fuel dimethyl ether or dimethyl carbonate is injected; introducing oxygen ions when the combustion is in a post combustion period and the temperature in the cylinder is not lower than a second temperature threshold;
step two, judging the concentration of micron-sized particles with the particle size smaller than 2.5 microns in the exhaust gas obtained in the step one, and performing electrostatic adsorption treatment on the exhaust gas when the concentration of the micron-sized particles exceeds a first particle concentration threshold value, or else, sequentially trapping and filtering by a first particle trap, a second particle trap and a third particle trap; judging the fractal dimension of the particles of the exhaust gas after electrostatic adsorption treatment, spraying the atomized methanol and dimethyl ether oxygen-containing mixed fuel into the exhaust gas when the fractal dimension exceeds a first threshold value, then carrying out high-temperature oxidation, or directly carrying out high-temperature oxidation, and then sequentially trapping and filtering by a second particle trap and a third particle trap;
and step three, carrying out plasma treatment, OH free radical heating treatment and activated carbon adsorption on the exhaust gas in the step two.
2. The method for reducing the content of polycyclic aromatic hydrocarbon substances in micron-sized particulate matters of a diesel engine as claimed in claim 1, wherein the in-cylinder real-time pressure P is dependent on the crank angleThe time when the variation curve of the pressure difference is separated from the cylinder pressure curve of the diesel engine under the condition of non-combustion is a fast combustion period, the time when the combustion is in the fast combustion period and the real-time pressure P in the cylinder rises and an inflection point appears is a slow combustion period, and the time when the combustion is in the slow combustion period and the temperature T in the cylinder rises and the inflection point appears is a post-combustion period.
3. The method for reducing the content of micron-sized particulate polycyclic aromatic hydrocarbon substances in a diesel engine as set forth in claim 1, wherein oxyfuel ethanol or n-butanol is injected when the in-cylinder oxygen concentration is lower than a first oxygen concentration threshold and higher than a second oxygen concentration threshold, and wherein oxyfuel dimethyl carbonate is injected when the in-cylinder oxygen concentration is not higher than the second oxygen concentration threshold, wherein the first oxygen concentration threshold is higher than the second oxygen concentration threshold.
4. The method for reducing the content of diesel particulate matter in polycyclic aromatic hydrocarbon substances in diesel engine micro-scale particles according to claim 1, wherein the third step comprises performing plasma treatment on the exhaust gas when the concentration of the gaseous aromatic hydrocarbon is greater than a first aromatic hydrocarbon concentration threshold value according to the concentration of the gaseous aromatic hydrocarbon in the exhaust gas of the engine; when the concentration of the gaseous aromatic hydrocarbon is not more than the first aromatic hydrocarbon concentration threshold value but more than the second aromatic hydrocarbon concentration threshold value, carrying out OH free radical heating treatment on the exhaust gas; when the concentration of the gaseous aromatic hydrocarbon is not greater than the second aromatic hydrocarbon concentration threshold value, performing activated carbon adsorption on the exhaust gas; and after the exhaust gas is treated, when the concentration of the gaseous aromatic hydrocarbon is greater than a third aromatic hydrocarbon concentration threshold value, the second step is carried out again, wherein the first aromatic hydrocarbon concentration threshold value is greater than a second aromatic hydrocarbon concentration threshold value, and the second aromatic hydrocarbon concentration threshold value is greater than the third aromatic hydrocarbon concentration threshold value.
5. The method of claim 1, wherein the exhaust gas is subjected to electrostatic adsorption treatment, and then whether the electrostatic adsorption voltage drop is larger than a first voltage drop threshold value is determined, if so, a reverse voltage is applied, and then the exhaust gas is directly trapped and filtered by a third particle trap, if not, the exhaust gas is subjected to electrostatic adsorption treatment again, and if not, the electrostatic adsorption voltage drop is determined to be larger than a second voltage drop threshold value, if so, the fractal dimension of the particles is determined, and if not, the exhaust gas is sequentially trapped and filtered by the first particle trap, the second particle trap and the third particle trap.
6. The method for reducing the polycyclic aromatic hydrocarbon content of diesel particulate matters of claim 1, wherein the first particulate trap is made of honeycomb ceramics, and the structural parameters are as follows: the average pore diameter is 22-25 μm, the porosity is 72-76%, the wall thickness is 7-8mil, and the length-to-diameter ratio is 0.5-0.7; the second particle catcher is made of honeycomb ceramics, and the structural parameters are as follows: average pore diameter is 15-18 μm, porosity is 65-68%, wall thickness is 10-12mil, and length-to-diameter ratio is 0.9-1.1; the third particle catcher is made of honeycomb ceramics, and the structural parameters are as follows: the average pore diameter is 10-12 μm, the porosity is 58-62%, the wall thickness is 14-16mil, and the length-to-diameter ratio is 1.3-1.5.
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