JPH09264121A - Back washing method for exhaust gas clean up device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back washing method for an exhaust gas cleanup device, whereby the time of back washing is accurately known and the loss of filter performance is prevented. SOLUTION: A back washing method is provided for performing bask wash reproducing by blowing in clean air from the downstream side of a filter 6 for eliminating fine particles contained in exhaust gas. In this case, the pressure losses of two points having different exhaust gas flow rates are calculated within the range of 15g/m or lower of soot accumulation amount per filter 1m<2> , flow rate factors obtained by dividing the calculated pressure losses with exhaust gas flow rates and soot accumulation amounts are expressed in a primary expression beforehand, and during actual running, an exhaust gas flow rate and a pressure loss are measured, a flow rate factor is calculated and then a soot accumulation amount corresponding to the flow rate factor calculated based on the primary expression beforehand is estimated. Back washing is performed when the estimated soot accumulation amount becomes a preset soot accumulation amount in which the amount is lower than 10g/L per filter and lower than 12.5g/m<2> per filter 1m<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backwashing method for an exhaust gas purifying apparatus, in which clean air is blown from the downstream side of a filter for removing fine particles in exhaust gas to carry out backwash regeneration.

[0002]

2. Description of the Related Art Conventionally, various exhaust gas purifying apparatuses have been known for performing backwash regeneration by injecting clean air from a downstream side of a filter for removing fine particles in exhaust gas. The backwash regeneration in this exhaust gas purification device first measures the pressure loss for a number of soot deposits with different flow rates in advance and creates a map.In actual operating conditions, the reverse soot is reversed when a certain soot deposit amount is obtained according to the created map. It was carried out by washing.

That is, as shown in FIG. 3 as an example of the map, the relationship between the pressure loss and the soot accumulation amount is previously obtained under the condition of different flow rates (in FIG. 3, each straight line shows data for one flow rate). In the actual operating state, the pressure loss of the filter and the flow rate of the exhaust gas passing through the filter are measured, and when the soot deposition amount estimated from the measured pressure loss and the flow rate reaches a preset soot amount, it is reversed. I was washing.

[0004]

However, the pressure loss with respect to the soot accumulation amount differs from filter to filter, and it is necessary to create the above map for each exhaust gas measuring device in order to perform accurate control. Therefore, there is a problem that a huge amount of data is required and it is troublesome. Further, if this is not done, when the exhaust gas temperature becomes high, there is a problem that self-combustion of the soot accumulated in the filter occurs, and in the worst case, the filter is melted and damaged.

Further, when the exhaust gas purifying apparatus is incorporated into an automobile and used, backwashing is generally performed by supplying air in the same series as the air brake tank, so waste of backwashing air deteriorates fuel efficiency. It is necessary to prioritize the air for brakes, which causes deterioration of backwash efficiency.Soot accumulated excessively is not completely removed by backwash, and it is necessary to replace the filter. There was also a problem.

The present invention is intended to solve the above-mentioned problems and to provide a method for backwashing an exhaust gas purifying apparatus which can accurately know the time of backwashing and does not impair the performance of the filter.

[0007]

A method for backwashing an exhaust gas purifying apparatus according to the present invention is a backwashing method for an exhaust gas purifying apparatus for performing backwash regeneration by blowing clean air from a downstream side of a filter for removing fine particles in exhaust gas. In the method, pressure loss at two points where the exhaust gas flow rate is different within a range where the soot deposition amount per 1 m ² of the filter is 15 g / m ² or less is obtained, and the flow coefficient obtained by dividing the obtained pressure loss by the exhaust gas flow rate and the soot deposition amount are first-ordered. It is converted into a formula and obtained in advance. During actual operation, the exhaust gas flow rate and pressure loss are measured, the flow rate coefficient is calculated, and the soot accumulation amount corresponding to the flow rate coefficient obtained by the previously obtained linear equation is estimated,
Estimated soot accumulation amount is 10 g / L per 1 L of filter
It is characterized in that the backwashing is carried out at the time when the preset soot accumulation amount of 12.5 g / m ² or less per 1 m ^{2 of the} filter is reached.

In the present invention, as a result of studying whether or not the map, which was conventionally required for each filter, that is, for each exhaust gas measuring device, could be replaced by a simple method, the linear equation of the flow coefficient and the soot accumulation amount was obtained. If the backwashing control for the exhaust gas measuring device is performed based on this linear expression without changing according to the change in the flow rate of each filter, that is, for each exhaust gas measuring device, the reverse of the exhaust gas measuring device can be performed easily and accurately. It has been found that washing can be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the construction of an example of an exhaust gas purifying apparatus for carrying out the backwashing method of the present invention. In the example shown in FIG. 1, the exhaust gas purifying apparatus 1 includes a supply pipe 4 for supplying exhaust gas from a diesel engine 3 having a dynamometer 2 for measuring the engine speed, and an exhaust gas supply chamber 5.
And a filter 6 for removing fine particles from the exhaust gas
And a processing gas exhaust chamber 7 and an exhaust pipe 8 for exhausting the processing gas to the outside. Further, the processing gas exhaust chamber 7 is provided with a backwashing cleaning device 9 for blowing clean air, which is the reverse of exhaust gas, into the filter 6 from the downstream side of the filter 6. The exhaust gas supply chamber 5 is backwashed with a filter 6
10 for burning the soot removed from the furnace
Is provided with a soot processing chamber 11.

In this embodiment, the pressure loss of the filter 6 can be obtained from the differential pressure between the pressure gauge 12 provided in the exhaust gas supply chamber 5 and the pressure gauge 13 provided in the processing gas exhaust chamber 7. At this time, if the temperature before and after the filter 6 is measured and the pressure values in the pressure gauges 12 and 13 are corrected according to the temperature, more accurate pressure loss can be measured. Further, the flow rate of exhaust gas can be calculated from the engine speed obtained by the dynamometer 2. Of course, the flow rate of this exhaust gas can also be obtained by another method, for example, by a flow meter provided in the supply pipe 4. Since the backwash cleaning device 9 is used for the backwash operation, a backwash solenoid valve 14 is provided between the backwash cleaning device 9 and the processing gas exhaust chamber 7, and a check valve 15 is provided in the exhaust pipe 8. It is provided.

Further, as the filter 6, a ceramic honeycomb structure, which is conventionally known as a diesel particulate filter (DPF), has an exhaust gas inlet side end and an exhaust gas side end alternately plugged. The body can be preferably used. Here, when the material of the ceramics is cordierite as the main crystal phase and the partition wall thickness of the honeycomb structure is 700 μm or less, the flow coefficient and soot deposition are accurately calculated by the linear equation required in the present invention. It is preferable because the relationship with the amount can be obtained.

Next, the backwashing method of the present invention will be described. First, the relationship between the flow coefficient of the exhaust gas purifying apparatus and the soot accumulation amount is obtained in advance. That is, the soot accumulation amount is measured and obtained at two points where the soot accumulation amount and the exhaust gas flow amount are different, and the pressure loss and the flow amount at that time are measured, and the pressure loss per unit flow amount is calculated to obtain the flow coefficient. Then, the soot accumulation amount with respect to the above-mentioned two points of the flow coefficient is plotted on the graph, and the plotted two points are connected on the graph to obtain a linear expression. After that, at the time of actual operation, the exhaust gas flow rate and the pressure loss are measured, and the flow rate coefficient is calculated from the measured exhaust gas flow rate and the pressure loss. Then, the soot accumulation amount is estimated from the calculated flow coefficient based on a previously obtained linear equation, and backwashing is performed when the estimated soot accumulation amount reaches a preset soot accumulation amount.

At this time, the two points for obtaining the relationship between the flow coefficient and the soot accumulation amount are as follows:
It is necessary to set below / m ² . Regarding the soot accumulation amount for backwashing, the soot accumulation amount is the filter 1L.
10 g / L or less and per 1 m ^{2 of} filter 12.
It is necessary to set the backwashing to be performed when a preset soot deposition amount is reached within a range of 5 g / m ² or less. These configurations will be apparent from the examples below.

[0014]

Example First, the amount of soot deposited for backwashing was examined. Example 1 In the exhaust gas purifying apparatus shown in FIG. 1, the test No. in which the partition wall thickness and the cell density of the filter 6 used were variously changed. 1 to
28 exhaust gas purifiers were prepared. The size of the filter 6 is uniformly diameter: 144 mm, length: 152 mm
(Volume: 2.47 L). The prepared exhaust gas purifying apparatus was backwashed by changing the opening time of the backwash solenoid valve 14, and the soot accumulation amount of each filter 6 was set to a predetermined value as shown in Table 1 below. After that, the diesel engine 3 was placed in a high load state and the soot was self-combusted in the filter 6. The confirmation of self-ignition, which is the start of self-combustion, was confirmed by the decrease in pressure loss. Then, after confirming self-ignition, the engine was stopped 1 hour after idling, the filter 6 of each exhaust gas purifying apparatus was disassembled, and the internal melting state was confirmed. The exhaust gas flow rate is 4 Nm ³ /
min. The results are shown in Table 1 below.

[0015]

[Table 1]

From the results shown in Table 1, the soot accumulation amount was 10 g /
It can be seen that when L is exceeded, melting loss can be confirmed in the filter 6. Further, even if the soot accumulation amount was 10 g / L or less, when the soot accumulation amount per filter area exceeded 12.5 g / m ² , the filter 6 was found to be melted. This is because when the soot accumulation amount exceeds 10 g / L, the combustion heat amount generated by the combustion of the soot increases and melting loss occurs in the filter 6, and even when the soot accumulation amount is 10 g / L or less, It is considered that when the soot deposition amount increases, the amount of heat given to a certain filter area increases and melting loss occurs.

Therefore, in order to improve the reliability of the backwashing operation, it is important to avoid the melting loss of the filter 6, and the backwashing is performed so that the soot accumulation amount is at least 10 g / L and 12.5 g / m. ^By carrying out at the time when the preset soot deposition amount within the range of ² or less is reached, the filter 6 will not be melted even if the deposited soot self-combusts, and a highly reliable backwashing method can be obtained. I understand.
The amount of soot deposited to carry out the above-mentioned backwash is 10 g above.
The threshold value may be set anywhere within the range of / L or less and 12.5 g / m ² or less, but if it is set too small, backwashing becomes too frequent. It is preferable to set the value close to.

Next, the range in which two points are set when the relationship between the flow coefficient and the soot accumulation amount is obtained was examined. Example 2 An exhaust gas purifying apparatus was prepared in the same manner as in Example 1, and the relationship between pressure loss and soot accumulation amount was investigated. In this example, the first embodiment
Since the exhaust gas flow rate is constant at 4 Nm ³ / min as shown in, the relationship between the pressure loss and the soot accumulation amount is the relationship between the flow coefficient and the soot accumulation amount. FIG. 2 shows the result.

From the results shown in FIG. 2, although the pressure loss varies depending on the partition wall thickness, cell density, etc., the soot deposition amount and the pressure loss are in a substantially linear relationship in any example up to a soot deposition amount of around 15 g / m ^2. Recognize. Therefore, the soot accumulation amount is 1
It can be seen that the linear equation showing the relationship between the soot accumulation amount and the pressure loss can be obtained by measuring two points in the range of 5 g / m ² or less. Here, if the soot deposition amount exceeds 15 g / m ² , a linear relationship does not hold, so if a linear expression is created including points of 15 g / m ² or more, accurate control cannot be performed.

[0020]

As is apparent from the above description, according to the present invention, the relationship between the flow coefficient and the soot accumulation amount is obtained in advance as a linear equation, and the inverse equation is obtained based on this linear equation during actual operation. Since the washing is controlled, it is possible to obtain the backwashing method of the exhaust gas purifying apparatus which can accurately know the time of the backwashing and does not impair the performance of the filter.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an example of an exhaust gas purifying apparatus for carrying out a backwashing method of the present invention.

FIG. 2 is a graph showing a relationship between pressure loss and soot accumulation amount in the present invention.

FIG. 3 is a graph showing a relationship between pressure loss and soot accumulation amount in a conventional example.

[Explanation of symbols]

1 exhaust gas purification device, 2 dynamometer, 3 diesel engine, 4 supply pipe, 5 exhaust gas supply chamber, 6 filter,
7 processing gas exhaust chamber, 8 exhaust pipe, 9 backwash cleaning device,
10 heater, 11 soot processing chamber, 12, 13 pressure gauge, 14 backwash solenoid valve, 14 check valve

Claims (4)

[Claims] 1. A fill for removing fine particles in exhaust gas.
Clean air is blown from the downstream side of the
In backwashing method of gas purifier, filter 1m ^Two Hit
The amount of soot deposited is 15 g / m^Two Exhaust gas flow within the following range
Calculate the pressure loss at two points with different amounts, and use the calculated pressure loss as the exhaust gas flow rate.
Convert the flow coefficient divided by and the soot accumulation amount into a linear equation
Obtained in advance, and during actual operation, exhaust gas flow rate and pressure
The loss is measured, the flow coefficient is calculated, and the linear equation obtained in advance is used.
The soot accumulation amount corresponding to the calculated flow coefficient is estimated and estimated.
Fixed soot accumulation amount is 10 g / L or less per 1 L of filter
Bottom and filter 1m^Two Per 12.5 g / m^Two The following
Backwash when the soot accumulation amount reaches the set value.
And a backwashing method for an exhaust gas purifying device. 2. The method of backwashing an exhaust gas purifying apparatus according to claim 1, wherein the temperature of the exhaust gas is measured to correct the pressure loss value. 3. The backwashing method for an exhaust gas purifying apparatus according to claim 1, wherein the filter is a honeycomb structure made of ceramics. 4. The backwashing method for an exhaust gas purifying apparatus according to claim 3, wherein the honeycomb structure made of the ceramic has cordierite as a main crystal phase and the partition wall thickness of the honeycomb structure is 700 μm or less.