JPH0639997B2 - Waste heat recovery method for graphitization furnace - Google Patents

Description

The present invention relates to a waste heat recovery method for a graphitization furnace.

[Conventional technology]

Conventionally, the graphitization furnace kept at a high temperature is only naturally cooled, and there is no example of recovering the waste heat.

[Problems to be solved by the invention]

Conventionally, in order to graphitize a product, the inside of the furnace is heated to about 3000 ° C. and then naturally cooled to about 400 ° C., and the product in the furnace is taken out. However, there are the following problems.

(1) It is uneconomical because it releases a huge amount of heat by natural cooling.

(2) Cooling takes about 15 days, resulting in poor productivity.

(3) In order to solve both, we want to recover the waste heat by forced cooling, but the temperature inside the furnace is high at 3000 ° C, and there are problems such as heat resistance of the waste heat recovery device and the outflow of heat insulating material, so it remains untouched. is there.

The present invention intends to provide a method capable of recovering waste heat of such a graphitization furnace for a purpose.

[Means for solving problems]

 The present invention is characterized by the following operations.

(1) Until the temperature in the furnace falls from about 3000 ° C to 1500 ° C or less, spontaneous cooling is performed as usual, and forced cooling is performed from 1500 ° C or less.

(2) In forced cooling, a low-temperature inert gas is passed as a heat medium into the furnace to cool the furnace and recover the heated inert gas as a heat source.

(3) The inert gas whose temperature has been lowered due to heat recovery is reused as a heat medium for forced cooling.

(4) Operate a plurality of graphitization furnaces by sequentially shifting the time,
The graphitization furnace in the forced cooling process is operated so that waste heat can be continuously recovered.

That is, the present invention is a method for graphitizing a product by arranging a plurality of graphitization furnaces in parallel, heating the inside of the furnace to 3000 ° C. to graphitize the product, and then spontaneously releasing it until the temperature falls below 1500 ° C. After cooling and then shutting off the atmosphere from the inside of the furnace, low-temperature inert gas is passed through the furnace as a heat medium to forcibly cool it, and the heated inert gas is used as a heat source and used as a heat source. As a result, the inert gas that has become low in temperature is repeatedly used as a forced cooling medium, and each graphitization furnace is operated by sequentially shifting the time to recover waste heat continuously. This is a waste heat recovery method for the graphitization furnace.

[Action]

This is possible because the waste heat recovery device has to withstand 1500 ° C by forcibly cooling from 1500 ° C or less like an inert gas.

(2) At a high temperature of 1500 ° C. or higher, the heat insulating material has a large flow and flows out together with the inert gas, but at a temperature of 1500 ° C. or less, the fluidity of the heat insulating material can be suppressed to prevent the heat flow out together with the inert gas.

(3) Since the product is a carbon material and has a high temperature, there is a risk that it will oxidize when it is exposed to air, for example, but since an inert gas is used, this risk can be prevented.

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a system diagram of waste heat recovery, FIG. 2 is a vertical sectional view of a graphitization furnace, and FIG. 3 is a process diagram of furnace operation.

There are multiple furnaces 1 for product insertion, natural cooling
The process of forced cooling product removal is as shown in Fig. 3.
The furnaces are operated with a time lag t.

Here, product insertion is a process of inserting a carbon product into a graphitization furnace, heating is a process of energizing the graphitization furnace to graphitize the carbon product, and natural cooling is a temperature of the graphitization furnace of 3000.
After cooling to around 1500 ° C, it is cooled to around 1500 ° C, forced cooling is a waste heat recovery process that uses a cooling gas, and product removal is the process of taking out a graphitized product from a graphitization furnace. Say.

The operation in each step will be described for one furnace in the order of steps.

When inserting the product, the valves 9, 10 and 14 are closed and the cover 6 is removed, and the product is inserted from above.

The cover 6 is attached at the time of heating, but the temperature of the inside of the cover 6 becomes high due to the gas generated in the furnace at the time of heating. Open the valve 14 to suck the gas generated in the furnace through the suction duct 15,
It is released into the atmosphere after gas cleaning. Heating is performed by electricity, and the product is graphitized by heating until the temperature inside the furnace reaches about 3000 ° C.

At the time of natural cooling, close the valve 14 and remove the cover 6,
It is allowed to cool until the temperature in the furnace becomes 1500 ° C or lower.

At the time of forced cooling, the cover 6 is first attached without floating, the valves 14 and 9 are opened, the air in the cover 6 is purged with an inert gas (for example, N ₂ gas), and then the valve 14 is closed and the valve 10 is opened. It is a circuit for forced cooling, that is, waste heat recovery. The waste heat recovery circuit is a blower 7 that is in continuous operation.
Causes a low temperature inert gas to pass through the duct 8 and the valve 9,
As shown in FIG. 2, it is fed into the furnace from the nozzle 5, passes through the gap between the heat generating material 3 and the product 4, cools the inside of the furnace, and then is fed into the cover 6. When the inert gas passes through the inside of the furnace, the heat insulating material 2 has a temperature of 1500 ° C. or lower at a stage so as not to be caught in the flow of the inert gas. The high temperature inert gas sent to the cover 6 passes through the valve 10 and the duct 11 to generate steam in the waste heat boiler 12. As for one furnace, cooling the furnace gradually lowers the temperature of the inert gas at the furnace outlet. Therefore, in the case of only one carbonization furnace, once the furnace is cooled, the waste heat cannot be recovered until the furnace is restarted. Even if multiple furnaces are installed, the waste heat can be used intermittently if the operation is irregular.

On the other hand, steam generation requires a continuous heat source. Therefore, as shown in FIG. 3, there are one or more, preferably a plurality of furnaces that belong to the process of forced cooling at any time by shifting the operating steps of a plurality of graphitization furnaces at appropriate intervals. In this way, the heat source will be continuously supplied.

The cooled inert gas passes through the dust collector 13 and the blower 7
And is repeatedly circulated as a heat medium. Since the inert gas is consumed when purging the air in the cover 6, the replenishment is performed by opening the valve 16 from the cylinder 17 that stores the inert gas.

When removing the product, close the valves 9, 10, 14 and cover 6.
Remove. The product is removed from the top of the furnace 1.

The recovered heat can be used not only for generating steam but also for preheating the product 4 and the heat generating material 3.

It is to be noted that FIG. 3 is a process chart schematically showing the situation of the steps of the graphitization furnace operation in the method of the present invention when three furnaces are used. In FIG. 3, T ₁ is the end point of product insertion in each furnace, T ₂ is the end point of graphitization, T ₃
Indicates the beginning of the process of cooling the graphitization furnace to 1500 ° C. and using the cooling gas, and T ₄ indicates the ending of the process of using the cooling gas. That is, when the No. 1 furnace enters forced cooling, the No. 2 and 3 furnaces are still in the natural cooling stage, and the No. 2 furnace enters forced cooling after a certain period of time. Before and after the No. 1 furnace finishes forced cooling, the No. 3 furnace enters forced cooling. In this way, by operating each furnace with an appropriate time lag, the cooling gas can be continuously flowed into the furnace, and as a result, the heated gas can be continuously taken out and exchanged with heat. However, it is difficult to unambiguously determine this time difference depending on the structure of the furnace and the state of the filling of the furnace. Therefore, it is desirable to keep one or more, preferably two furnaces in the forced cooling state at all times. In this case, if the number of furnaces is set so that the total value of the time required for forced cooling of each furnace is longer than the total time from the product insertion to the product removal for one furnace, it is possible to eliminate waste throughout the operating time. It is possible to recover heat and generate steam.

〔The invention's effect〕

By forcibly cooling a plurality of furnaces with an inert gas from a furnace temperature of 1500 ° C or less for a certain period of time, (1) the cooling time of the graphitization furnace can be shortened and the products in the furnace can be delivered early. It will be possible and productivity will be improved.

(2) The inert gas heated by forced cooling can be continuously used as a heat source, and effective waste heat recovery can be performed, resulting in a large energy saving effect.

[Brief description of drawings]

Fig. 1 is a waste heat recovery system diagram, Fig. 2 is a longitudinal sectional view of the furnace, and Fig. 3
The figure is a process diagram of the furnace operation.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuaki Makino 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Inventor Yasuhisa Yamamoto 569, Hamakata, Hofu City, Yamaguchi Prefecture Tokai Carbon Co., Ltd. Hofu Plant (72) Inventor Shigeyuki Mukai No. 569, Hamakata, Hofu City, Yamaguchi Prefecture Tokai Carbon Co., Ltd. Hofu Plant

Claims (1)

[Claims] 1. A method of graphitizing a product by arranging a plurality of graphitizing furnaces in parallel, wherein the inside of the furnace is 30 for graphitizing the product.
After heating to 00 ° C, let it cool naturally until it drops below 1500 ° C, then shut off the atmosphere from the inside of the furnace, then pass a low-temperature inert gas as a heat medium into the furnace to forcibly cool it and heat it. Use the high temperature inert gas as a heat source,
The inert gas that has become low in temperature as a result of being used as a heat source should be repeatedly used as a forced cooling medium, and the graphitization furnaces should be operated sequentially at different times to continuously recover waste heat. A characteristic method for recovering waste heat from a graphitization furnace.