CN114165321A

CN114165321A - Method for prepositioning diesel engine black smoke particle filtering device

Info

Publication number: CN114165321A
Application number: CN202010965962.6A
Authority: CN
Inventors: 胡定灏
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-09-11
Filing date: 2020-09-11
Publication date: 2022-03-11

Abstract

The invention provides a method for preposing a diesel engine black smoke particle filtering device, which aims to solve the defects of DOC + DPF + SCR. At the moment, the exhaust pollutants containing a small amount of black smoke particles are subjected to catalytic reaction through DOC and selective reduction reaction through SCR. Because DPF and other black smoke particle filter equipment are before DOC and SCR, the content of black smoke particle is less in the exhaust pollutant through DOC and SCR, thereby prolong DOC and SCR's best operating condition's time, guarantee DOC and SCR work efficiency, extension DOC and SCR's life.

Description

Method for prepositioning diesel engine black smoke particle filtering device

Technical Field

The invention relates to the filtration and purification of black smoke particles and harmful gases generated in the working process of a diesel engine, in particular to a method for installing a black smoke particle filter device of the diesel engine in front of other purification devices in an exhaust system of the diesel engine.

Background

When a diesel engine works, as the working principle of the diesel engine belongs to the compression ignition type and the chemical composition components of diesel oil, the mixture of the diesel oil and air can generate incompletely combusted residues, namely black smoke particles, and generate Hydrocarbons (HC), Nitrogen Oxides (NO) and carbon monoxide (CO), aiming at the pollutants, the method adopted in the world at present is to intercept and filter the black smoke particles in the tail gas of the diesel engine by a DPF (black smoke particle filter) and purify the Nitrogen Oxides (NO) and the carbon monoxide (CO) in the tail gas of the diesel engine by a DOC (diesel particulate filter).

An Oxidation-type catalytic converter (DOC) is installed in an engine exhaust pipeline and converts carbon monoxide (CO) and Hydrocarbons (HC) in engine exhaust into harmless water (H) through Oxidation reaction₂O) and carbon dioxide (CO)₂) The apparatus of (1). Oxidation type catalytic converters typically require secondary air injectionAnd the oxygen is matched to provide oxygen required by oxidation reaction, so that the emission of carbon monoxide (CO) and Hydrocarbon (HC) in the exhaust gas is reduced.

An oxidation catalyst is installed in a diesel engine for a vehicle, and a noble metal such as platinum (Pt) or palladium (Pd) is used as a catalyst to mainly reduce the content of SOF in particulate emissions and reduce PM emissions. Meanwhile, HC and CO in the exhaust gas can be effectively reduced. The oxidation catalyst may remove 90% of the SOF, thereby reducing PM emissions by 40% -50%. The HC and CO treatment efficiency can reach 88 percent and 68 percent respectively. The catalytic oxidation technology has good effect on removing soluble organic components (SOF) in particulates discharged by a diesel engine, namely a catalytic converter is additionally arranged in an exhaust system of the diesel engine, and the SOF is subjected to oxidation reaction under the action of noble metal catalysts such as platinum, rhodium, palladium and the like or rare earth catalysts and the like to be converted into CO₂And H2O, typically with a removal efficiency of up to 80%. And simultaneously, harmful substances such as HC and CO in the tail gas can be removed.

However, this technique is relatively ineffective in removing carbon particles and the catalyst has the effect of removing SO in the exhaust gas₂Catalytic conversion to SO₃The tendency to form sulfate particles, especially at higher temperatures, is increased, resulting in a minimal reduction in the total particulate matter emissions. And the presence of sulfides also tends to poison and deteriorate the catalyst. Diesel particulate catalytic oxidation technology is generally applicable to diesel fuels having a relatively low sulfur content. DOC does not have as good a PM trapping effect as particulate filters, but because the ignition temperature of hydrocarbons is low (renewable at 170 ℃), DOC does not require expensive regeneration systems and the investment costs are low.

A Diesel Particulate Filter (DPF) is a device installed in an exhaust system of a diesel vehicle to reduce Particulate Matter (PM) in exhaust gas by filtration. The DPF, which captures particles by a filter device mixed with surface and inside, such as diffusion precipitation, inertial precipitation or linear interception, can effectively purify 70% to 90% of particles in exhaust gas, is one of the most effective and direct methods for purifying diesel particulate matter, and has been commercialized internationally. To meet the euro VI or us 2010 emission regulations, diesel exhaust aftertreatment systems will be more complex, requiring integration of a Diesel Oxidation Catalyst (DOC), a Diesel Particulate Filter (DPF), a Selective Catalytic Reduction (SCR), etc. to control diesel emissions.

A Diesel Particulate Filter (DPF) mainly has 3 processes of a particulate filter empty, a particulate filter full, and a particulate filter reduction. In the empty working state of the particle filter, because the DPF is not blocked by any particles stored in the DPF, the flow resistance of the exhaust gas is very low, and the normal work (such as oil consumption and power) of the engine cannot be influenced. As soot particles are continuously generated, the amount of soot particles trapped inside the DPF increases, which results in an increase in exhaust resistance of the exhaust gas, and fuel consumption and power of the engine are affected by an increase in exhaust back pressure. The engine control unit monitors the pressure inside the DPF through the exhaust gas pressure sensor, when the engine control unit monitors that the pressure inside the DPF reaches a certain value, exhaust gas is difficult to discharge, the dynamic property and the fuel economy of the engine are greatly limited, the engine control unit controls the automatic cleaning and reduction work of soot particles, the soot particles accumulated inside the DPF are burnt at high temperature, and the regeneration of the DPF is realized.

Selective Catalytic Reduction (SCR) is carried out on SCR tail gas of a diesel engine, and the technical principle is that nitrogen oxides are selectively reduced to generate nitrogen and water in an oxygen-rich environment by utilizing a reducing agent under the action of a catalyst. The basic working principle is that the combustion process in a cylinder of the diesel engine is optimized, so that the emissions of carbon monoxide (CO), Hydrocarbon (HC), Particles (PM) and the like in the combustion exhaust gas are effectively controlled and meet the requirements of regulations, and finally, Nitrogen Oxides (NOX) with higher content in the exhaust gas discharged by the engine are treated by a special vehicle-mounted after-treatment system so as to meet the requirements of the regulations. During the post-treatment process, the dosing unit can accurately inject the urea amount matched with the operation condition of the engine into the exhaust pipe according to the instruction given by the electronic control unit of the engine, and the ammonia and the nitrogen oxides decomposed from the urea are subjected to catalytic reduction reaction in the catalyst to finally generate harmless nitrogen (N2) and water (H2O). It has been determined that the conversion of nitrogen oxides by SCR exhaust aftertreatment systems can typically reach over 60%.

The DOC + DPF + SCR is a combination mode popular in the world at present, namely, a mixture (harmful gas and black smoke particles) exhausted by a diesel engine is catalyzed by the DOC, then the black smoke particles are filtered by the DPF, and selective reduction is carried out by the SCR so as to discharge cleaner, nontoxic and harmless gas. However, after the DOC works for a period of time, the surface of the carrier coated with the catalyst is attached with a layer of black smoke particles, the black smoke particles form an isolation layer between the surface of the carrier coated with the catalyst of the DOC and exhaust gas flow, the surface of the carrier coated with the catalyst cannot be continuously contacted with toxic gas, and catalytic reaction in the later period is carried out, so that the working efficiency of the DOC is reduced, and even when the black smoke particles are continuously accumulated, the gas flow channel of the DOC is blocked, so that the exhaust back pressure of the diesel engine is increased, and the normal work of the diesel engine is influenced.

Disclosure of Invention

Detailed Description

The technical solutions and methods in the examples and comparative examples of the present invention will be described in detail below, and the examples and comparative examples are a part of the examples and comparative examples of the present invention but not all of them. Based on the examples and comparative examples of the present invention, other examples and comparative examples obtained by a person of ordinary skill in the art without any inventive work are within the scope of the present invention.

Example 1

The combination of a set of DPF + DOC + SCR is installed in a diesel exhaust system of a fifty-bell 4JB1 diesel engine, and diesel engine exhaust pollutants are firstly filtered by black smoke particles of the DPF and then subjected to catalytic reaction and selective reduction by the DOC and the SCR. After the diesel engine works for 5000 hours, a large amount of black smoke particles are intercepted in the DPF, the surfaces of DOC and SCR carriers and an exhaust passage only have a very small amount of black smoke particles, and all pollutants (black smoke particles, HC, CO and NO) in the exhaust gas after filtering, catalytic reaction and selective reduction by the system reach the relevant standards in the China Association for environmental protection GB 36886-2018.

Comparative example 1

Respectively installing a set of combination of DPF + DOC + SCR and a set of combination of DOC + DPF + SCR in the same diesel engine exhaust system of Isuzu 4JB1, and detecting according to the relevant standards in the China environmental protection Association GB36886-2018, wherein the combined detection result of DPF + DOC + SCR is as follows:

has a value of 0.12, HC/10^-6Has a value of 20, CO/% has a value of 0.02, NO/10^-6Has a value of 89; the combined detection result of DOC + DPF + SCR is

Has a value of 0.11, HC/10^-6Has a value of 23, a value of 0.03 for CO/% and a value of NO/10^-6The value of (D) is 81.

Under the same working condition, after the diesel engine with the Isuzu 4JB1 works for 5000 hours, various indexes (black smoke particles, HC, CO and NO) in exhaust pollutants after the two combined filtering, catalytic reaction and selective reduction are respectively detected. The combined detection result of DPF + DOC + SCR is

Has a value of 0.12, HC/10^-6Has a value of 21, a value of 0.02 CO/% and a value of NO/10^-6Has a value of 90; the combined detection result of DOC + DPF + SCR is

Has a value of 0.12, HC/10^-6Has a value of 950, a value of 3.02 CO/% and a value of NO/10^-6Has a value of 780. The conclusion is that the combination of DPF + DOC + SCR has no qualitative change in the catalytic reaction and selective reduction performance of DOC and SCR after 5000 hours of work, and the DOC + DPF + SCR combination cannot perform effective catalytic reaction because the surface of a DOC catalyst carrier is attached with a black smoke particle layer which isolates the contact of the surface of the catalyst carrier and exhaust pollutants, namely, the exhaust gas flow which is not subjected to catalytic reaction is directly discharged through the DPF and the SCR, so HC/10 in the exhaust gas flow^-6Value of (d), value of CO/% NO/10^-6The value of (c) rises in a straight line. That is, since the efficiency of the catalytic reaction of the DOC is greatly affected after the catalytic substrate surface of the DOC is covered with the black smoke particle layer during operation of the combination of DOC + DPF + SCR, the role of the DOC in the entire exhaust system is affected.

It should be noted that the DPF, DOC, SCR used in the two combinations mentioned in the above examples and comparative examples are the same, and their arrangement order is changed during the operation. The conclusion that the method of placing the black smoke particle filtering device in front of the DOC and the SCR can effectively improve the working efficiency of the DOC and the SCR and effectively ensure the optimal working state of the DOC and the SCR is achieved. In particular, in the method of the present invention in which the soot particulate filter is disposed in front of the DOC or SCR, the soot particulate filter may be employed not only as long as it includes the DPF but also as long as it is a soot particulate filter.

Claims

1. A method for prepositioning a black smoke particle filter device of a diesel engine is characterized in that the black smoke particle filter device is positioned in front of other purification and catalysis devices, and exhaust pollutants of the diesel engine are purified and catalyzed by the other purification and catalysis devices after black smoke particles are filtered by an exhaust gas flow through the black smoke particle filter device.

2. The diesel soot particulate filter device as defined in claim 1, comprising DPF and other soot particulate filter devices.

3. The diesel engine as claimed in claim 1 includes all compression ignition diesel engines including automotive diesel engines, engine block diesel engines, engineering machinery diesel engines, ship diesel engines, etc.