JPH0244568B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present application relates to a method for treating particulates consisting primarily of carbon particles discharged into the atmosphere from a combustion device such as a flue of a diesel engine or a metal melting furnace.

The above-mentioned particulates must be separated and removed before being released into the atmosphere due to the need to preserve the atmosphere.
Therefore, it is conceivable to treat it using a storage tank. However, the particle size of the fine particles is said to be on the order of submicrons, and when ordinary materials are used, they cause early clogging and cannot function effectively for a long period of time. As an improvement over these shortcomings, there is a device that uses a heat-resistant material to trap fine particles and, after reaching a predetermined clogging state, burns them using a burner or electric heating means to regenerate the overfunction. method is known. However, even in this case, there are the following drawbacks. That is, since fine particles made of carbon particles have a high ignition temperature of about 500° C. and a slow burning rate, they require heating means to maintain a predetermined temperature for a predetermined period of time, resulting in large energy losses. This is a fatal drawback, especially in the above-mentioned diesel engine, which has limited heating means.

In view of the above, the present application provides a processing method that separates and removes fine particles consisting of carbon particles without consuming a large amount of external energy.

The method of the present invention will be explained by taking as an example the treatment of particulates discharged from a diesel engine. In FIG. 1, an exhaust pipe 3 near an exhaust manifold 2 of a diesel engine 1
A heat-resistant filter 4 is disposed between the filter 4 and the manifold 2, and an alkali metal compound supply device 5 is provided between the filter 4 and the manifold 2, and the alkali metal compound is discharged from the device in the form of a powder or a mist from an aqueous solution to the exhaust gas. It is designed to be brought into contact with carbon particles.

The heat-resistant filter 4 is made of a steel wool filling, a porous ceramic body, and a porous metal body. Alkali metal compounds are hydroxides and oxides of alkali metals such as Li, Na, and Ca.

In FIG. 1, particulates in the exhaust gas are captured by a heat-resistant filter. As the capture progresses, the heat-resistant filter reaches a predetermined clogging state, but at the same time, the filter is heated by the waste heat. In this state, when an alkali metal compound is discharged from the alkali metal compound supply device and brought into contact with the captured particles, the particles are ignited and burned. In this case, the ignition temperature and combustion rate are lower and faster than usual due to the action of the alkali metal compound.

These phenomena are based on the well-known properties of alkali metal compounds, and are said to occur because carbon is modified by the alkali metal compounds. Therefore, the particulates captured by the filter are quickly burned away at a temperature below the normal ignition temperature.

To describe the effects of specific examples, in Figure 1, as a heat-resistant filter made of densely packed steel wool and an alkali metal compound.
When using NaOH aqueous solution and spraying it,
It ignited at 350-400℃ and continued to burn. On the other hand, if NaOH aqueous solution is not added, approx.
The fire ignited at 500℃, but the fire did not spread and was quickly extinguished.

As described above, in the treatment method of the present invention, fine particles in exhaust gas are once captured in a heat-resistant filter, and then the captured particles are brought into contact with an alkali metal compound that has the properties of lowering the ignition temperature and increasing the combustion rate. Since the filter function is regenerated by burning out the particles, it is possible to permanently remove the particles without requiring a large amount of energy for combustion.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a diesel engine for explaining the method of the present invention. 4...Heat-resistant filter, 5...Alkali metal compound supply device.

Claims (1)

[Claims] 1. An exhaust system in which fine particles consisting of carbon particles in the exhaust gas are captured by a heat-resistant filter, and when a predetermined clogging occurs, an alkali metal compound is discharged into the exhaust gas, and the captured particles are ignited and burned. A method for treating particulates in gas.