JPH04260407A - Waste gas treatment device and filter for use therein - Google Patents

Abstract

PURPOSE:To provide a waste gas treatment device for efficiently removing dioxin and the like contained in the waste gas of a waste incinerator. CONSTITUTION:A waste gas treatment device includes a filter 1 having non- woven fabric composed of filaments having a diameter of 0.5mum or smaller to which surface treatment of fluororesin is applied.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment device, and particularly to an exhaust gas treatment device suitable for removing particulates contained in the exhaust gas of an incinerator.

0002

[Prior Art] The exhaust gas from incinerators that incinerate waste discharged from businesses and households contains harmful substances such as chlorine compounds, nitrogen compounds, sulfur compounds, and soot.
If these are released into the atmosphere as they are, they will cause serious air pollution. In particular, among chlorine compounds, polychlorinated dibenzo-p-dioxin (Polychlor
inated dibenzo-p-dioxin;P
CDDs), polychlorinated dibenzofurans (Polychl
orinated dibenzofuran;PDD
Fs), Coplanar PCB, etc.
Dioxin-related substances (hereinafter referred to as
They contain dioxins (dioxins), so the efficient removal of these is an important issue in preventing air pollution.

Conventionally, the regulation value for dioxins contained in incinerator exhaust gas was set at 0.5 ng/m3N in the report of the ``Dioxins, etc. Expert Committee on Waste Treatment'' (May 1981). This value was also adopted in the ``Guidelines for Prevention of Dioxins'' established in December 1990 (Environmental Development Division, Water Supply and Environment Department, Ministry of Health and Welfare). However, in many European and American countries, the above regulation value is set at 0.1ng/m3N,
In Japan, there is a strong opinion that this regulatory value should be raised to the same level as in Europe and the United States, so it is thought that the trend will be toward raising the regulatory value in the future.

0004

[Problems to be Solved by the Invention] Currently, there are no particularly new devices for removing dioxins contained in the exhaust gas of incinerators, but there are conventional dust collectors for treating exhaust gas, that is, electrostatic precipitators. Containers and bag filters are used. In addition, the guidelines also mention electrostatic precipitators or filtration type precipitators as devices,
It merely recommends that the exhaust gas temperature at the inlet of these precipitators be reduced as much as possible.

However, the electrostatic precipitator and bag filter described above have a problem in that they cannot efficiently remove dioxins from exhaust gas for the following reason.

First, electrostatic precipitators have low pressure loss;
It is also suitable for large-capacity gas processing, so it is widely used for incinerator exhaust gas processing. However, recently, when the operating temperature is usually around 300°C, dioxins are generated inside the dust collector. It has been pointed out that the
8) See P336-P343).

[0007] This is because the suitable temperature for chlorine compounds to react and produce dioxins is around 300°C;
This is thought to be due to the fact that the exhaust gas remains in the precipitator for a relatively long time at a temperature around this temperature, and in addition to this, corona discharge in the precipitator accelerates the above reaction. Therefore, in order to suppress the production of dioxins, it has been proposed that it is effective to operate the dust collector at a temperature of 200 degrees Celsius or less (see the above document), but this has not yet been put to practical use. .

On the other hand, the basic performance of bag filters is that they have poor collection efficiency for submicron-order fine particles (the collection efficiency for particles of 0.3 to 0.5 μm is about 99%), and that they have poor collection efficiency for dioxins. Since dioxins are often adsorbed by fly ash with a size of 0.5 μm or less, efficient removal of dioxins by bag filters cannot be expected. In addition, bag filters have a large pressure loss (150 to 250 m
There is also the drawback of mAq).

[0009] A HEPA filter (Hi
gh Efficiency Particulate
Air Filter) is known. However, since normal HEPA filters cannot be backwashed, they have to be disposable, which is uneconomical.Also, in order to increase dust collection efficiency and extend the lifespan, the ventilation speed must be set to 0. It is necessary to set the speed to about 5m/min,
This method requires a very large filtration area for treating exhaust gas from an incinerator, and has many drawbacks, such as requiring an extremely large installation area, and cannot be put to practical use.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide an exhaust gas treatment device that can efficiently remove dioxins contained in the exhaust gas of an incinerator. It is in.

[0011]

[Means for Solving the Problems] In order to develop a backwashable HEPA filter (class 50 or less for particles of 0.5 μm according to NASA [National Aeronautics and Space Administration] standards) As a result of intensive research, we have found that the above objective can be achieved by using a filter made of a nonwoven fabric made of fibers of 0.5 μm or smaller and surface-treated with a fluororesin.

The present inventors have previously developed a HEPA filter for collecting fine particles made of fibers that have been surface-treated with fluororesin (Japanese Patent Application Laid-Open No. 111915/1983). Compared to HEPA filters, it has significantly superior performance, at least in terms of removing particulates contained in incinerator exhaust gas. This is because, while the above-mentioned HEPA filter for collecting fine particles is substantially composed of a woven fabric, the filter of the present invention is composed of a non-woven fabric. This is thought to be because the collection efficiency is better.

The nonwoven fabric used in the filter of the present invention includes inorganic fibers such as glass fibers and carbon fibers, polyester fibers,
Although any organic fibers such as vinylon fibers can be used, inorganic fibers are more preferable in terms of heat resistance, and glass fibers are particularly preferable among inorganic fibers in view of manufacturing cost. The filter of the present invention is intended to collect submicron-order fine particles, especially fine particles of 0.5 μm or less to which harmful substances such as dioxins are adsorbed, so the diameter of the fibers used is 0.5 μm or less. It needs to be less than that.

[0014] The filter of the present invention has a fluororesin coating on the surface of the fibers constituting the nonwoven fabric.
Since it is difficult for fine particles to adhere to the surface of the fibers, the fine particles can be easily peeled off during backwashing. It is not necessarily necessary to coat each and every fiber with fluororesin; for example, an emulsion or solution containing fluororesin may be applied to the side that will be the inlet side of the exhaust gas when the filter is installed in an exhaust gas treatment device. is sufficient. The filter of the present invention differs in particulate collection efficiency depending on the fiber diameter, the density of the nonwoven fabric, and the degree of fluororesin surface treatment, but it is not difficult to obtain performance comparable to conventional HEPA filters. Backwashing is also possible in this case.

[0015] As described above, since the filter of the present invention can be backwashed, it can be used for a long period of time without deteriorating its particulate collection performance, and the ventilation speed can be increased to about 1 to 2 m/min. Therefore, it is economically advantageous, such as requiring only a small installation area.

An example of a preferred shape of the filter of the present invention is shown in FIGS. 1 and 2. FIG. 2 is a partially enlarged view of the filter shown in FIG. The entire filter 1 is processed into a pleated shape so that the collection area can be increased with a small volume. A mountain-shaped separator 2 made of metal, paper, synthetic resin, etc. is interposed in the gap between each fold, and the filter 1
prevents deformation. The filter 1 and separator 2 are inserted into the frame 3 and installed in an exhaust gas treatment device. As shown by the solid arrow in FIG. 2, the exhaust gas flows upward from the bottom of the filter 1, and at this time, particulates in the exhaust gas are collected on the lower surface side of the filter 1. Further, during backwashing, as shown by the broken line arrow in the figure, the ejected gas is caused to flow from above to below the filter 1, and the collected particles are separated from the filter 1 by the vibration of the separator 2 at that time.

FIG. 3 shows another example of the shape of the filter 1. This filter 1 is folded inside and out to form an endless continuous pleat, and a porous separator 2 having a similar shape is attached to the inner peripheral surface of the filter 1. As shown by the solid arrow in the figure, this filter 1 is designed so that exhaust gas flows from its outer peripheral surface to the inner peripheral surface of the separator 2, and fine particles in the exhaust gas are collected on the outer peripheral surface of the filter 1. It has become. In addition, during backwashing, as shown by the broken line arrow in the figure, the ejected gas is caused to flow from the opening 4 of the filter 1 through the inner circumferential surface of the separator 2 to the outer circumferential surface of the filter 1, and the vibration of the separator 2 at this time is The collected particulates are removed from the filter 1.

The filter of the present invention can obtain sufficient strength even when used alone by using a thick non-woven fabric. For example, as shown in FIG. By stacking and using
Benefits in terms of strength, thickness and pressure drop. As the fiber base fabric 1b, inorganic fibers such as glass fibers and carbon fibers, and organic fibers such as polyester fibers and vinylon fibers can be used as in the nonwoven fabric 1a, but from the viewpoint of heat resistance, inorganic fibers, especially glass fibers is suitable.

When the filter of the present invention is applied to the treatment of exhaust gas from a waste incinerator, the temperature of the exhaust gas as it passes through the filter is controlled in advance to 250°C or lower using a well-known cooling means such as a heat exchanger or water injection. Preferably, it is necessary to cool the temperature to 200°C or lower. In addition, in order to remove harmful acidic substances such as hydrogen chloride and sulfur oxides contained in exhaust gas,
It is desirable to use well-known exhaust gas treatment methods, such as injecting lime milk or aqueous ammonia instead of water injection, and if necessary, install a cyclone or bug in the front stage of the exhaust gas treatment equipment equipped with the filter of the present invention. Filters, electrostatic precipitators, scrubbers, etc. may be installed to pre-collect particulates. An example of such waste incineration equipment is shown in FIG.

[0020]

EXAMPLE A filter of the present invention was prepared by surface-treating a nonwoven fabric made of glass fiber with a diameter of about 0.2 μm with a fluororesin. In addition, as a comparative example, a filter having the same shape and dimensions as the above filter was prepared by subjecting a nonwoven fabric made of glass fibers having a diameter of 2 to 3 μm to surface treatment with a fluororesin. Next, 5 pieces of calcium carbonate fine particles with a diameter of 0.2 to 5 μm were added.
A gas containing mg/m3N was passed through each filter under conditions of 80°C and a wind speed of 1 m/min. The number of particles (particles/10 liters) that passed through the filter was measured according to particle size, and the results shown in Table 1 below were obtained.

[0021]

[Table 1]

Next, the performance of the filter of the present invention and a commercially available HEPA filter (class 100) was compared under the same conditions as above, and the results shown in FIG. 6 were obtained. The filter of the present invention has 1
It was used while backwashing every hour to shake off adhering particles. On the other hand, commercially available HEPA filters could not be backwashed, so they were used continuously.

As is clear from the figure, the commercially available HEPA filter broke when the pressure loss exceeded 50 mmAq after about 4 hours.

[0024]

[Effects of the Invention] According to the present invention, the following effects can be obtained.

(1). The filter for an exhaust gas treatment device of the present invention can efficiently remove particulates contained in the exhaust gas of an incinerator, particularly particulates of 0.5 μm or less that contain dioxins.

(2). Since the filter of the present invention can be backwashed, it can be used repeatedly for a long period of time without deteriorating its particulate collection performance.

(3). Since the filter of the present invention allows a large amount of air to pass through, it is possible to downsize the exhaust gas treatment device.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing a filter for an exhaust gas treatment device that is an embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG. 1;

FIG. 3 is a perspective view showing a filter for an exhaust gas treatment device according to another embodiment of the present invention.

FIG. 4 is an enlarged sectional view of a main part of the filter for an exhaust gas treatment device of the present invention.

FIG. 5 is an overall configuration diagram of a waste incineration facility incorporating the exhaust gas treatment device of the present invention.

[Figure 6] Filter for exhaust gas treatment equipment of the present invention and commercially available HE
It is a graph diagram for comparing the performance of PA filters.

[Explanation of symbols]

1 Filter 1a Nonwoven fabric 1b Fiber base fabric 2 Separator 3 Frame 4 Opening

Claims (4)

[Claims] [Claim 1] Diameter 0 with fluororesin surface treatment
．． An exhaust gas treatment device comprising a filter having a nonwoven fabric made of fibers of 5 μm or less. 2. The exhaust gas treatment device according to claim 1, wherein the fibers are glass fibers. [Claim 3] Diameter 0 with fluororesin surface treatment
．． A filter for an exhaust gas treatment device, characterized by having a nonwoven fabric made of fibers of 5 μm or less. 4. The filter for an exhaust gas treatment device according to claim 3, wherein the fiber base fabric is laminated.