JPH05228330A - Dry treatment of waste gas - Google Patents

Abstract

PURPOSE:To efficiently treat a waste gas without using ammonia as an additive and with the amt. of calcium oxide or magnesium oxide to be used remarkably reduced by combining a dust collector and a desulfurizer and removing a back corona. CONSTITUTION:Calcium oxide or magnesium oxide is injected on the upstream side of a dust collector impressed with a pulse charge as an additive. The sulfur dioxide contained in a waste gas is oxidized by a pulsed corona discharge into gaseous sulfur dioxide, which is adsorbed by the fine powder of the calcium oxide or magnesium oxide and removed by the dust collector along with the dust.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to harmful components in exhaust gas,
In particular, it relates to an exhaust gas dry treatment method for removing sulfur dioxide SO ₂ , hydrogen chloride HCl and the like by a dry method.

[0002]

2. Description of the Related Art A large-scale exhaust gas treatment facility used in a thermal power plant or the like is composed of a denitration device, a dust removal device, a desulfurization device, etc., and each device was separately arranged. Figure 5
Fig. 1 shows an example of the configuration of a conventional large-scale exhaust gas treatment facility.
In FIG. 5, ammonia is introduced into the exhaust gas discharged from the coal boiler, and the nitrogen oxide NO _x in the exhaust gas is removed by the denitration device. In this denitration apparatus, for example, exhaust gas is brought into contact with a denitration catalyst in which titanium oxide carries vanadium oxide or the like, and nitrogen oxide NO _x is selectively converted into nitrogen N ₂ and removed. The exhaust gas from which the nitrogen oxides have been removed is then heat-exchanged by an air heater and dedusted by a dust collector to which continuous charging is applied. Sulfur dioxide SO ₂ is then removed in a desulfurizer. The wet method in which a slurry of calcium oxide (CaO) is sprayed to a desulfurization device has become the mainstream in large devices.

Various systems are used as small and medium-sized exhaust gas treatment equipment such as garbage incineration equipment, but recently, calcium oxide powder is put into the exhaust gas and reacted with sulfur dioxide SO ₂ or hydrogen chloride HCl, and a bag filter is used. The method of collecting is beginning to be adopted. FIG. 6 shows an example of an exhaust gas treatment facility of a conventional refuse incineration facility. The exhaust gas discharged from the incinerator is introduced into the waste heat boiler, calcium oxide powder is added to the exhaust gas discharged from the waste heat boiler, and dust removal, dechlorination, and desulfurization are performed by the next bag filter.

A bag filter has been conventionally used for the high electric resistance dust containing a large amount of calcium oxide as described above. However, it has been confirmed that an electrostatic precipitator employing pulse charging has been put into practical use in recent years and is excellent in performance. This dust collector suppresses the back corona phenomenon that tends to occur in the electric dust collector that employs continuous charging.
The re-scattering of the collected dust is small and the dust particles are efficiently charged, so that the application of the electrostatic precipitator is expanded.

[0005]

For removing sulfur dioxide SO ₂ and hydrogen chloride HCL by the dry method, a method of introducing calcium oxide CaO powder into exhaust gas is known, but sulfur dioxide SO ₂ and hydrogen chloride HCL are known. The reaction between calcium oxide CaO and calcium oxide CaO is not efficient, and the amount of calcium oxide CaO added needs to be added 3 to 6 times more than the equivalent amount of the gas to be collected. there were.

Dust containing a large amount of calcium oxide CaO has a high electric resistance value in the conventional continuously charged electrostatic precipitator,
Back corona phenomenon occurred and it was difficult to collect. Also,
A method is known in which ammonia NH ₃ gas is sprayed in front of the electrostatic precipitator to perform desulfurization, but in this method, a large amount of ammonia NH ₃ is contained in the collected dust, which causes the following problems. Was there. That is, when the temperature of the dust is cooled, ammonium salts such as ammonium salt NH ₄ Cl and ammonium sulfate NH ₄ SO ₄ are generated and adhere or bridge on the inner wall of the hopper, which causes unstable discharge. Was there. In addition, the same problem occurs in the dust transportation device. Furthermore, most of the collected dust is landfilled, but in the case of dust containing such ammonia salts, ammonia separates during landfilling, the surroundings smell like ammonia, and ammonia dissolves in water. It was released and decomposed, and the total nitrogen content in water increased, which was one of the causes of water pollution.

Further, in the method of collecting with a bag filter as in the above-mentioned small and medium-sized exhaust gas treatment equipment, there has been a problem that the pressure loss becomes as large as 150 to 200 mmAg. Further, in the conventional exhaust gas treatment facility, the dust removal device and the desulfurization device are separately provided as described above, and thus a large site area is required for the entire exhaust gas treatment facility.

Therefore, in the present invention, the amount of the additive such as calcium oxide, which is used for removing the harmful substances in the exhaust gas by the dry method and for removing the harmful components, is much smaller than that conventionally used. An object of the present invention is to provide an exhaust gas treatment method that can be performed, has a small pressure loss, and has a high removal efficiency.

[0009]

In order to solve the above-mentioned problems, the present invention provides a powder of calcium oxide Ca in exhaust gas.
Additives such as O and magnesium oxide MgO are introduced into the upstream side of the dust collector to which pulse charge is applied, and passed through a pulse-shaped corona discharge region in the dust collector, whereby sulfur dioxide SO ₂ in the gas is discharged. The present invention provides a dry exhaust gas treatment method characterized by removing harmful substances such as hydrogen chloride and HCl at the same time as removing dust.

The additive is charged in a place upstream of the electrostatic precipitator equipped with the pulse charging device. In the exhaust gas discharged from the fluidized bed boiler, lime is used as a fluid medium, and this fluid medium can also serve as an additive. Therefore, in this case, there is a sufficient concentration of calcium oxide CaO in the dust, and it is not necessary to newly add calcium oxide CaO for desulfurization.

[0011]

For example, the sulfur dioxide SO ₂ gas in the exhaust gas is easily oxidized by the pulsed corona discharge, and is oxidized to the sulfurous acid SO ₃ gas. The sulfurous acid SO ₃ gas is immediately adsorbed on the surface of the floating dust and the fine powder of calcium oxide CaO (or magnesium oxide MgO) that has been introduced. This adsorption method uses calcium oxide C
High desulfurization efficiency can be obtained with a small amount of calcium oxide CaO, as compared with the case where aO and sulfur dioxide SO ₂ gas are simply subjected to solid-gas reaction.

[0012] The sulfur dust adsorbed and floating is collected and removed by the above-mentioned electric dust collector using pulse charging. Various exhaust gas treatment facilities using a desulfurization device using this pulse charging device are conceivable, some of which are shown in FIGS. 1 to 4 and explained in the next embodiment.

[0013]

[Embodiment 1] FIG. 1 is an exhaust gas treatment according to an embodiment of the present invention.
The total equipment configuration of the equipment is shown, and it is large for thermal power plants.
The exhaust gas treatment equipment of is shown. This equipment consists of boiler, air
A heater, pulsed charged electrostatic precipitator, pulse
It consists of a denitration device to which a charge is applied. This exhaust gas treatment
Exhaust gas discharged from the boiler at the facility is
The temperature can be lowered by the data. This temperature is adjusted
CaO powder CaO powder was added to the exhaust gas
And introduced into the electrostatic precipitator. With this electric dust collector
Is present in the exhaust gas because pulsed charging is applied.
Sulfur dioxide SO ₂Is oxidized to sulfurous acid SO₃To gas
Become. This sulfurous acid SO₃Gas is floating calcium oxide
Um is adsorbed on the surface of CaO and, together with floating dust, this powder
The dust is collected by an electric dust collector to which loose charges are applied.
That is, desulfurization is performed at the same time as dust removal. Next,
Ammonia is introduced into dust and desulfurized exhaust gas to remove NOx.
Be done.

[0014]

[Embodiment 2] FIG. 2 shows a total apparatus configuration of an exhaust gas treatment facility according to another embodiment of the present invention, showing a large-scale exhaust gas treatment facility such as a thermal power plant. The difference in the device configuration from the first embodiment is that the activated carbon type denitration device is adopted in the exhaust gas treatment equipment of the first embodiment instead of the pulse charging type denitration device. In this exhaust gas treatment facility, Example 1
Similarly, heat exchange by an air heater and dust removal and desulfurization by pulse charging in the presence of calcium oxide CaO powder are performed. Then, denitration is performed by an activated carbon type denitration device.

[0015]

[Embodiment 3] FIG. 3 shows a total apparatus configuration of an exhaust gas treatment facility according to another embodiment of the present invention, showing a large-scale exhaust gas treatment facility such as a thermal power plant. The difference in the device configuration from the first embodiment is that the configuration order of each device is different, and the order is a boiler, a denitration device, an air heater, and an electric dust collector by pulse charging.

In this exhaust gas treatment equipment, ammonia is introduced into the exhaust gas discharged from the boiler and denitration is performed by the denitration device. Then, heat exchange is performed by the air heater to lower the temperature of the exhaust gas, and calcium oxide is introduced into the exhaust gas. Next, dedusting is performed at the same time as desulfurization by an electrostatic precipitator to which pulse charging is applied.

[0017]

[Embodiment 4] FIG. 4 shows a small-to-medium-sized exhaust gas treatment facility such as a refuse incinerator. The equipment consists of incinerator, waste heat boiler,
It consists of an electrostatic precipitator to which pulse charging is applied and a denitration device. Exhaust gas discharged from the incinerator is heat-exchanged in the waste heat boiler to lower the temperature. Then, the calcium oxide powder is introduced and introduced into the electrostatic precipitator to which pulse charging is applied. Here, desulfurization, dechlorination, and dedusting are performed at the same time. Dechlorination is performed here because the exhaust gas from the refuse incinerator contains hydrogen chloride HCl together with sulfur dioxide SO ₂ . Ammonia is introduced into the exhaust gas that has undergone desulfurization, dechlorination, and dust removal, and is introduced into a denitration device to denitrate.

[0018]

As described above in detail, according to the present invention, sulfur dioxide SO ₂ and hydrogen chloride HCL in exhaust gas are contained.
When subjected to a pulsed corona discharge, is in a state of being easily oxidized, and is adsorbed by floating dust, calcium oxide CaO or magnesium oxide MgO, and efficiently removed by an electrostatic precipitator. Therefore, compared with the conventional case where solid-gas reaction is simply performed, a smaller amount of calcium oxide C
A high removal effect could be obtained with aO or magnesium oxide MgO.

Further, according to the present invention, sulfur dioxide SO ₂ and hydrogen chloride HCl, which are harmful components from the exhaust gas, do not need to be provided with a dust collector and a plurality of these harmful component removing devices, and one dust collecting device can be used. These operations can be performed simultaneously within the device. In the electrostatic precipitator of the present invention, the pressure loss is 2
The pressure loss is about 0 mmAg, which is far smaller than the pressure loss of 150 to 200 mmAg when the conventional bag filter is used.

[Brief description of drawings]

FIG. 1 shows a total device configuration of an exhaust gas treatment facility used for a large-scale exhaust gas treatment facility such as a thermal power plant.

FIG. 2 shows a total apparatus configuration of an exhaust gas treatment facility used in a large-scale exhaust gas treatment facility such as a thermal power plant according to another embodiment.

FIG. 3 shows a total apparatus configuration of an exhaust gas treatment equipment used in a large-scale exhaust gas treatment equipment such as a thermal power plant according to another embodiment.

FIG. 4 shows small and medium-sized exhaust gas treatment equipment such as a refuse incinerator.

FIG. 5 shows an example of the configuration of a conventional large-scale exhaust gas treatment facility.

FIG. 6 shows an example of conventional small and medium-sized exhaust gas treatment equipment.

Claims (2)

[Claims] 1. A powdered additive is introduced into exhaust gas on the upstream side of an electrostatic precipitator to which pulse charge is applied, and the additive is passed through a pulse-shaped corona discharge region in the precipitator, whereby A dry exhaust gas treatment method, which removes harmful substances such as sulfur dioxide SO ₂ and hydrogen chloride HCl while removing dust. 2. The dry exhaust gas treatment method according to claim 1, wherein the additive is calcium oxide CaO or magnesium oxide MgO.