JPH088060A - Method for controlling power of three-phase arc type ash melting furnace - Google Patents

Abstract

PURPOSE:To enhance the efficiency of a quick melting process and to prevent the wear of furnace walls by enabling the amount of heat generated to be distributed to three electrodes as required, in a three-phase arc type ash melting furnace into which the ashes of municipal and industrial wastes or the like are put so as to be subjected to the melting process in which an arc discharge is caused at the three electrodes using a three-phase AC power supply. CONSTITUTION:An arc discharge using a three-phase AC power supply is caused between each of three electrodes A, B, C hanging down into a furnace and a molten slug to melt ashes in the furnace. In this three-phase arc type ash melting furnace, desired impedances ra, rb, rc, are set for the electrodes A, B, C, respectively, and the electrodes A, B, C are independently raised and lowered so that the impedances of the electrodes are held at the desired impedances ra, rb, rc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to incinerate incinerated ash of municipal waste, industrial waste, etc. into a furnace and subject the three electrodes to arc discharge using a three-phase alternating current as a power source to melt the incinerated ash. The present invention relates to a power control method for a three-phase arc type ash melting furnace.

[0002]

2. Description of the Related Art If the incineration ash discharged from an incinerator for municipal solid waste, industrial waste, etc. is thrown into a landfill site as it is, it may cause environmental damage such as elution of harmful substances. The incinerator ash is melted in a melting furnace and solidified into a glass.

As is well known, this arc type melting furnace hangs down a rod-shaped electrode supported by an electrode supporting device into the furnace.
An arc discharge is generated between the lower end of the electrode and the molten slag surface at the bottom of the furnace to heat the incineration ash by the heat generation, but conventionally, the power control is performed by adjusting the impedance to stabilize the input power. A method called constant impedance control is adopted in which the electrodes are automatically moved up and down to keep them constant.

[0004] Therefore, when the first described this constant impedance control, in FIG. 6, A is the electrode, M is a motor for raising and lowering movement of the electrode, the inverter 1NV is for controlling the motor, T _r is a furnace transformer, CT, PT is current detection means and voltage detection means provided in the power transmission cable to the electrode A, R and I ₂ are resistors and detection currents connected to the current detection means CT, and A ₁ is a control module.

Secondary current and voltage of the transformer for the furnace are I ₁ , V
₁ , and the CT ratio and the PT ratio are α ₁ and α ₂ , respectively, the measured voltage E _i transmitted from the current detection means CT to the control module A ₁ and the voltage detection means PT to the control module A ₁
The measured voltage E _v transmitted to the device is expressed by the following equation.

[Equation 1] Also

[Equation 2] Then, the electrode is controlled so as to stop when M = O, and the balance point is

(Equation 3) Becomes

Here, if the impedance is Z _a ,

[Equation 4] Than

(Equation 5) Becomes The current is Δi ₁ from the balance point for some reason.
If it increases,

(Equation 6)

When M is positive (+), the electrode A rises,
When minus (-), it descends. From the diagram in the control module A ₁ , when the electrode A rises at a speed v corresponding to M ′ = α · Δi ₁ · R, the arc length increases and the transformer secondary side current I ₁ decreases. When the amount of increase in arc current Δi ₁ decreases and returns to I ₁ , M = 0 and the electrode stops. Therefore, the impedance Z _a is always controlled to be constant. Also, from the equation (1), by adjusting the R, it can be seen that adjusting the impedance Z _a.

By the way, in a three-phase arc type ash melting furnace using a three-phase alternating current as a power source, as shown in FIGS. 2 and 3, three electrodes A, B and C are provided in the furnace at each vertex of an equilateral triangle. There is a form in which they are arranged so as to be positioned, or a form in which they are arranged at equal intervals on a straight line as illustrated in FIG. Power was supplied evenly regardless of the relative positional relationship with the outlet.

[0009]

Therefore, in the portion near the ash input port D, molten incineration ash is accumulated due to insufficient heat amount, but in the vicinity of the electrode A, the heat amount is excessive and the furnace wall is overheated, and its wear is accelerated. However, problems such as efficiency deterioration and durability deterioration due to excess and deficiency of electric power have occurred.

However, in the conventional power control method for a three-phase arc type ash melting furnace, even though the total amount of power can be controlled, the power distribution to each electrode cannot be controlled individually and is uniform. There was a problem.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and the inside of the furnace is arc-discharged between the three electrodes hanging in the furnace and the molten slag by using a three-phase AC power source. In a three-phase arc type ash melting furnace in which a constant impedance control device that melts the incinerated ash of each is added to each electrode, each phase is determined from the power supply voltage, the total input power required for melting, and the power distribution ratio to each electrode. It is characterized in that the target impedance of is calculated.

[0012]

[Function] Maintaining the total input power required for melting without excess or deficiency,
In addition, an appropriate power distribution to each electrode can be set freely, and an appropriate amount of heat can be generated in a necessary portion without excess or deficiency.

[0013]

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 shows a power system diagram of a three-phase arc ash melting furnace according to the present invention. In the figure, 1 is a transformer for a three-phase AC reactor,
2 is a furnace body, A, B, C are motors 4A, 4 in the furnace body 2.
Power transmission cables 5A, 5B, and 5C are wired from the secondary side of the transformer 1 to the electrodes A, B, and C, respectively, which are electrodes that can be lifted and lowered by the operation of B and 4C.

6A, 6B and 6C are motors 4A, 4B and 4
An impedance control device for issuing an electrode ascending / descending speed command to each of the motors 4A, 4B, 4C in order to individually ascend / descend the electrodes 3A, 3B, 3C by C. impedance r _a a target, r _b, r _c is commanded, the electrodes a,
B, C and arcs and furnace molten slag impedance is respectively the impedance r _a, including, r _b, respective electrodes A to be held in r _c, B, to move up and down the C.

The arithmetic unit 7 has a power supply voltage E (V) on the secondary side of the transformer of the three-phase AC power supply and a total input power P _o (KW).
And the required power distribution ratio P _a to each electrode A, B, C: P
_{b: P c = 1: n} : n (n> 0) because the impedance r _a, r _b, the r _c is calculated by the following equation (2) the impedance control unit 6A, 6B, it instructs the 6C.

(Equation 7) However, r and k are respectively calculated from the following equations (3) and (4).

[Equation 8]

[Equation 9]

As an example, power supply voltage E = 310 v, total input power P _o = 1200 KW, power distribution ratio P _a : P _b :
_{P c = 1: 1.1: 1.1} (n = 1.1) and the impedance for r _a, r _b, is as follows when determining the r _c.

[Equation 10]

In short, the impedance r _a on the electrode A side is 55.6 mΩ, and the impedance on the electrode B side and C side is 9
By raising and lowering each of the electrodes so as to be held at 5.5 mΩ, the input power by the electrode A is controlled to 375 KW, the input power by the electrodes B and C is controlled to 412.5 KW, and the total input power P _o is 1200 KW. Can be controlled.

Next, the calculation of the above general formulas (2) to (4) will be described. In the case of a melting furnace, the resistance component on the secondary side of the reactor transformer 1 is much larger than the reactance component.
The reactance can be ignored and calculated. The equivalent circuit on the secondary side of the transformer and its Y → Δ conversion equivalent circuit are as shown in FIG. The power supply voltage (transformer secondary side voltage) that makes the phase rotation A → B → C is expressed by the following equation (5).

[Equation 11] When the impedance is converted from Y to Δ,

[Equation 12] Therefore, the line current of each phase of the three-phase alternating current flowing through the electrodes A, B, C is

[Equation 13] It is represented by.

On the other hand, considering that electric power is equally applied to the electrodes B and C near the ash inlet, r _b = r _c . Further, the impedance r _a on the electrode A side is r,
If the ratio of r _a and r _b (r _c ) is k,

[Equation 14] If the electrodes B, C may lengthen the arc length as compared with the electrode A, Radiated heat of the arc is shifted to unmelted ashes, rapid melting is because it is conducive _{r a <r b (r c} ). Therefore, k> 1. The above formula (9) is the same as the above formula (2).

Further, by substituting the equation (9) into the equation (6), R ₁
When R ₃ is represented by k and r,

(Equation 15)

[Equation 16]

[Equation 17]

(Equation 18)

Therefore, the power distribution ratio n is substituted into the above equation (4) to obtain k, and the required total input power P is obtained in the equation (3).
Substituting _o , the power supply voltage E and the above k to obtain r, the equation (2)
By substituting the respective electrodes A side, B side, the impedance is a target C side r _a, calculates r _b, r _c, the r _a, r _b, the r _c the impedance control unit 6A, 6
By instructing B and 6C, it is possible to operate with sufficient power distribution.

[0022]

As described above, according to the present invention, it is possible to always properly set the power distribution of each electrode in an arc type ash melting furnace using a three-phase alternating current as a power source, and to reduce efficiency due to excess or deficiency of the amount of heat generated. It also has the beneficial effect of eliminating wear and tear on the furnace wall.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a power control method for a three-phase arc ash melting furnace according to the present invention.

FIG. 2 is a plan view of a furnace body showing an arrangement example of electrodes.

FIG. 3 is a vertical cross-sectional view of a furnace body showing an arrangement example of electrodes.

FIG. 4 is a plan view of a furnace body showing another example of arrangement of electrodes.

FIG. 5 is an equivalent circuit diagram of the transformer secondary side.

FIG. 6 is a block diagram showing a constant impedance control method.

[Explanation of symbols]

A, B, C electrode 1 furnace transformer 2 furnace 6A, 6B, 6C impedance control unit r _a, r _b, r _c impedance

Claims (1)

[Claims] 1. A constant impedance control device for melting an incinerated ash in a furnace by performing arc discharge using a three-phase AC power supply between the three electrodes hanging in the furnace and the molten slag is added to each electrode. In the three-phase arc type ash melting furnace, the target impedance of each phase is calculated from the power supply voltage, the total input power required for melting, and the power distribution ratio to each electrode. Power control method for three-phase arc type ash melting furnace.