JPH08278011A - Ash melting method in plasma type ash melting furnace and plasma type ash melting furnace - Google Patents

Abstract

PURPOSE: To melt ash efficiently while reducing the generating amount of NOx and permitting the restriction of operation cost. CONSTITUTION: Electrodes 21A, 21B are arranged in a melting chamber 2. reserving base metal 3 on the bottom part thereof, and a hydrocarbon gas supplying device 23, supplying hydrocarbon gas for operating plasma in the melting chamber 2 through gas supplying holes 22A, 22B formed in the electrodes 21A, 21B, is provided while a combustion air supplying nozzle 24 for supplying combustion air to burn hydrocarbon gas within the range of 0.7-1.0 of logical air ratio, is arranged in the melting chamber 2. The reduction combustion of hydrocarbon gas is effected and the combustion heat is utilized for the melting of ash whereby a power consumption is reduced, the generation of NOx is restrained and the oxidizing consumption of the electrode can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ash melting method and a plasma ash melting furnace in a plasma ash melting furnace for heating and melting ash by a plasma arc.

[0002]

2. Description of the Related Art In a conventional plasma-type ash melting furnace, when water-cooled copper is used for the electrode, low-cost air is used as the plasma working gas, and when carbon is used for the electrode, the electrode is oxidized. In order to suppress consumption, an inert gas such as nitrogen gas or argon gas has been used as a plasma working gas.

[0003]

However, when air is used as the plasma working gas, a large amount of NO _X is generated because it is heated to a high temperature, and there is a problem that a NO _X countermeasure is required. Further, when an inert gas such as nitrogen gas or argon gas is used as the plasma working gas, there is a problem that the operating cost increases.

The present invention solves the above problems and eliminates NO _x.
It is an object of the present invention to provide an ash melting method and a plasma ash melting furnace in a plasma ash melting furnace that can perform efficient ash melting with no need for countermeasures, operating cost reduction.

[0005]

In order to solve the above problems, an ash melting method in a plasma ash melting furnace of the present invention supplies a hydrocarbon gas as a plasma working gas to an electrode arranged in a melting chamber. At the same time, combustion air for combusting the hydrocarbon gas with a theoretical air ratio of 0.7 to 1.0 is supplied into the melting chamber.

Further, in the plasma ash melting furnace, an electrode is arranged in a melting chamber for accommodating a conductor at the bottom, and a hydrocarbon gas for supplying a hydrocarbon gas to a tip portion from a gas supply hole formed in the electrode. A supply device is provided, and a combustion air supply nozzle for supplying combustion air for combusting the combustible gas in an air ratio range of 0.7 to 1.0 is provided in the melting chamber.

Further, in the above structure, a reburning burner is arranged to face the slag outlet and burn unburned hydrocarbon gas.

[0008]

According to the above construction, the combustion heat obtained by burning the hydrocarbon gas can be used for melting the ash in addition to the heat generated by the plasma arc, so that the power consumption of the electrode can be reduced. As a result, the cost of the hydrocarbon gas can be supplemented and the ash can be efficiently melted. Since the melting chamber is combusted in a reducing atmosphere, it is possible to reduce the oxidation loss of the electrode can achieve low NO _X reduction in the exhaust gas.

Further, since the unburned exhaust gas remaining can be burned by the reburning burner, the exhaust gas can be safely sent, and the combustion heat of the unburned content can be prevented from solidifying the molten slag at the slag outlet. Can be used.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the plasma ash melting furnace according to the present invention will be described below with reference to the drawings.

In the melting chamber 2 formed by the furnace body 1,
A base metal 3, which is an example of a conductor, is housed in the bottom portion,
An ash inlet 5 is formed on one side wall 1a of the melting chamber 2, and a slag outlet 6 is formed on the other side wall 1b. The ash input port 5 is provided with an ash pusher device 8 for sending the ash A from the ash supply hopper 7 to the melting chamber 2 through the ash input port 5. Further, outside the slag extraction outlet 6, a slag extraction chamber 10 having a water granulation pit 9 at the bottom is provided, and a re-combustion chamber 11 is provided at the upper part in succession to the slag extraction chamber 10, An exhaust gas duct 12 is connected to the reburn chamber 11. Further, the side wall 11a of the re-combustion chamber 11 facing the slag outlet 6 prevents a blockage due to the solidification of the molten slag S, and a reburn burner that burns unburned components of a plasma working gas (hydrocarbon gas) described later. 13 are provided. 14 in the case of containing harmful gases such as HCl and SO _X in the exhaust gas, a Araikemuri device interposed flue gas duct 12 as necessary.

A pair of electrodes 21A and 21B consisting of a cathode and an anode are provided through a supporting device on the ceiling wall 1a of the furnace body 1, and the tips of these electrodes 21A and 21B are opposite to the base metal 3. Of the gas supply holes 22A and 22B for supplying the plasma working gas to the shaft center portion, respectively. These gas supply holes 22
A hydrocarbon gas supply device 23 is connected to the base ends of A and 22B. The hydrocarbon gas supply device 23 includes a gas supply pipe 23b that connects the gas supply holes 22A and 22B and a gas tank 23a, and a gas supply pipe 23b. It is composed of gas flow rate adjusting valves 23c and 23c interposed in the supply pipe 23b. In this ash melting furnace, CH ₄ , C is used as plasma working gas.
₂ H ₆ , C ₃ H _8, etc., LNG gas (city gas), LP
Hydrocarbon gas such as G gas (propane gas) is used.

Combustion air nozzles 24 for supplying combustion air for combusting the hydrocarbon gas are arranged on both sides of the electrodes 21A and 21B, respectively, and are sent from an air supply pump 25 through an air supply pipe 26. Combustion air is supplied from the combustion air nozzle 24 into the melting chamber 2, and the hydrocarbon gas is burned at a theoretical air ratio of 0.7 to 1.0 by the air flow rate adjusting valve 27 interposed in the air supply pipe 26. Composed. Here, the combustion air ratio is set in the range of 0.7 to 1.0 because when the ratio exceeds 1.0, the carbon electrodes 21A, 21
As the oxidative consumption of B increases, NO _{X is} contained in the exhaust gas.
This is because the amount of generation is significantly increased, and if it is less than 0.7, the unburned amount in the exhaust gas becomes too large and the hydrocarbon gas is wasted.

Next, the operation of the plasma type ash melting furnace having the above structure will be described. The ash A sent from the ash supply hopper 7 to the melting chamber 2 by the ash pusher device 8 is the electrode 2 to which the power is supplied.
The hydrocarbon gas heated as a plasma working gas while being heated by the plasma arc formed between 1A, 21B and the base metal 3 is burned by the combustion air nozzle 26.
Combustion air supplied from the above to the melting chamber 2 undergoes reduction combustion in the theoretical air ratio range of 0.7 to 1.0 to be heated and melted. The amount of heat generated by the hydrocarbon gas at this time occupies about 6 to 10% of the total amount of heat, so that the electrodes 21A, 2
1B power consumption can be reduced by about 6-10%,
The cost of hydrocarbon gas can be supplemented. Further, since the carbon is reduced and burned, it is possible to prevent the carbon electrodes 21A and 21B from being consumed by oxidation, and to reduce the NO in the exhaust gas.
_The amount of _X generation can be suppressed.

As a result, the melted molten slag S is dropped from the slag outlet 6 through the slag extraction chamber 10 into the water granulation pit 9 to form water granulated slag. At this time, at the slag outlet 6, the reburning burner 13 is activated and its combustion heat prevents clogging due to solidification of the molten slag S,
Furthermore, the unburned components in the exhaust gas discharged from the melting chamber 2 are burned.

[0016]

As described above, according to the present invention, the combustion heat obtained by burning a hydrocarbon gas is
Since it can be used for melting ash in addition to the heat generated by the plasma arc, it can reduce the power consumption of the electrode, which can compensate the cost of hydrocarbon gas and efficiently melt ash. You can Since the melting chamber is combusted in a reducing atmosphere, it is possible to reduce the oxidation loss of the electrode can achieve low NO _X reduction in the exhaust gas.

Further, since the exhaust gas remaining unburned can be burned by the reburn burner, the exhaust gas can be safely sent, and the combustion heat of the unburned content can be prevented from solidifying the molten slag at the slag outlet. Can be used.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a plasma type ash melting furnace according to the present invention.

[Explanation of symbols]

 A ash S Molten slag 1 Furnace body 2 Melting chamber 3 Base metal 5 Ash inlet 6 Slag outlet 10 Slag outlet 11 Reburning chamber 12 Exhaust gas duct 13 Reburning burner 21A, 21B Electrode 22A, 22B Gas supply hole 23 Hydrocarbon gas Supply device 23c Gas flow rate control valve 24 Combustion air supply nozzle 27 Air flow rate control valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location F23J 1/00 ZAB F23J 1/00 ZABB H05B 7/18 ZAB H05B 7/18 ZABE (72) Inventor Michio Ishida 5-3-28 Nishikujo, Konohana-ku, Osaka-shi, Osaka Prefecture Hitachi Shipbuilding Co., Ltd. (72) Inventor Tsutomu Kuwahara 5-3-28 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd. (72) Inventor Hideo Sato 5-3-28 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd. (72) Inventor Hiroshi Kosaka 5-3-28 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd.

Claims (3)

[Claims] 1. Combustion in which a hydrocarbon gas is supplied as a plasma working gas to an electrode arranged in a melting chamber and the hydrocarbon gas is burned in the melting chamber in a theoretical air ratio range of 0.7 to 1.0. A method for melting ash in a plasma-type ash melting furnace characterized by supplying air for use. 2. A hydrocarbon gas supply device in which an electrode is disposed in a melting chamber having a conductor accommodated in the bottom thereof, and a hydrocarbon gas for plasma operation is supplied into the melting chamber from a gas supply hole formed in the electrode. And a combustion air supply nozzle for supplying combustion air for combusting the hydrocarbon gas in an air ratio range of 0.7 to 1.0 in the melting chamber. 3. A plasma-type ash melting furnace according to claim 2, further comprising a reburning burner for burning unburned hydrocarbon gas, facing the slag outlet.