JPH0340317B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tunnel kiln with an improved cooling zone from the viewpoint of energy saving.

To explain the structure of a general tunnel kiln, as shown in Figs. 1 to 3, it is equipped with a pre-preparation zone From the entrance 3, it passes through the tunnel kiln successively in the order of pre-heating zone X, firing zone Y, and cooling zone Z toward the exit 4 on the right.

A burner 5 is installed in the firing zone Y. The flame from burner 5 is in the firing zone Y.
While heating, it flows as waste gas in the direction of preheating zone X, preheating the fired product 1 in preheating zone
more excreted.

The fired product 1 that has passed through the preheating zone X and the firing zone Y is cooled in the cooling zone Z by cooling air blown in from an inlet 7 installed in the ceiling, and then pushed out of the furnace through an outlet 4.

The pressure of the cooling air blown in from the inlet 7 is approximately the same at the boundary between the firing zone Y and the cooling zone Z, that is, at the cooling zone Z side of the firing zone Y and at the portion of the cooling zone Z on the firing zone Y side. The cooling air blown into the cooling zone Z is prevented from flowing into the firing zone Y, so that the firing of the fired product 1 in the firing zone Y is not hindered.

The cooling air that has cooled the fired product 1 in the cooling zone Z becomes heated air that absorbs a part of the heat of the fired product 1, and is blown into the preheating zone X through the wind pipe from the exhaust hole 8 installed in the side wall. After the fired product 1 in the preheating zone X is preheated together with the waste gas from the firing zone Y, it is discharged from the chimney 6.

In this way, the tunnel continuously transfers waste gas from the firing zone Y and heated air from the cooling zone Z to the preheating zone X.
Since the heat efficiency is higher than that of a single kiln (a kiln with intermittent motion that repeatedly heats and cools each firing), it is preferable in that respect, but recently there is a demand for even greater energy savings. It's starting to be done.

Therefore, in order to save energy by further increasing the thermal efficiency of the tunnel kiln, sufficient heat recovery from the fired product 1 is performed in the cooling zone Z.
It is necessary to effectively utilize the recovered heat.

That is, the heat held by the fired product 1 that has passed through the firing zone Y is gradually cooled down in the cooling zone Z. A part of the heat dissipated at this time is blown to the preheating zone X and used together with the heat of the waste gas from the firing zone Y to preheat the fired product 1. Air is also blown to the tunnel kiln and used for drying the fired product 1 before entering the tunnel kiln.

However, when utilizing these heats, cooling air is blown into the cooling zone Z, and the heat of the fired product 1 is absorbed and recovered as heated air, and the heated air is sent to the preheating zone X or drying furnace. In this case, it is necessary to maintain the balance of the furnace pressure in the cooling zone Z and the cooling conditions for the fired product 1. Therefore, the amount of cooling air blown is adjusted. Therefore, it was not possible to recover heat beyond this limit. As a result, the heat that is not recovered is either absorbed by the furnace body or radiated out of the furnace as heat carried away by the fired product 1 and the trolley 2.

In addition, heated air is used as the combustion air supplied to the burner in order to utilize the recovered heat, thereby saving fuel. However, cooling zone Z
When heated air recovered from the furnace is used as combustion air, contamination of the heated air becomes a problem.
The heated air recovered from the inside of the furnace in the cooling zone Z is dirty heated air containing dust, waste gas, etc. from inside the furnace, which is undesirable because it reduces combustion efficiency. The heated air for combustion is required to be clean heated air that does not contain dust or waste gas.

This invention solves the above-mentioned drawbacks of conventional tunnel kilns, improves its cooling structure, increases heat recovery efficiency, and improves thermal efficiency by making more effective use of recovered heat. The purpose is to provide an improved tunnel kiln.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 4 to 6.

The main point of this invention is that the cooling zone Z is provided with a heat storage cooling type heat exchanger 9 and an indirect cooling box 10.

As shown in FIGS. 4 to 6, the fired products 12 loaded on the cart 11 are sequentially moved from the preheating zone X through the firing zone Y to the cooling zone Z, where they are continuously fired as in the conventional method. A description of the configuration that is substantially the same as that of the conventional one will be omitted.

When the trolley 11 and the fired product 12 are moved within the tunnel kiln, the fired product 12 is cooled in the cooling zone Z by cooling air blown in through the blow holes 13 installed in the ceiling of the cooling zone Z. Baked product 12
The heated air that has absorbed part of the heat is blown into the preheater X from the exhaust hole 14 through the wind pipe. This structure is also substantially similar to a conventional tunnel kiln, so
Detailed explanation will be omitted.

In the embodiment shown in the figure, in addition to these, a heat storage cooling type heat exchanger 9 and an indirect cooling box 1 are installed, for example, in the cooling zone Z at the positions shown in FIGS. 4 to 6.
0 is installed to enhance heat recovery in cooling zone Z.

In the embodiment shown in the figure, the regenerative cooling type heat exchanger 9 is installed at a position in the cooling zone Z near the firing zone Y, and the firing is performed in the cooling zone Z without blowing cooling air into the furnace in the cooling zone Z. The object 12 is indirectly cooled.

To explain the structure of the heat storage cooling type heat exchanger 9, the ceiling side wall of the heat exchanger portion of the cooling zone Z is made of a refractory material with a high heat capacity (for example, magnesia), which has a high thermal conductivity, specific heat, and specific gravity.
A heat-resistant steel pipe is embedded in the refractory to form a block-like structure, and the outside is kept warm by a heat insulating material (for example, ceramic fiber).

Next, the indirect cooling box 10 is installed on the ceiling and/or side wall of a low-temperature section at a position further on the exit side of the cooling zone Z than the position of the regenerative cooling type heat exchanger 9. This indirect cooling box 10 also indirectly cools the fired product 12 in the cooling zone Z without blowing cooling air into the furnace in the cooling zone Z, like the heat exchanger 9.

The structure of the indirect cooling box 10 has a hollow wall made of a heat-resistant steel plate that is isolated from the inside of the furnace, and the outside is kept warm with a heat insulating material such as rock wool.

The functions of the heat storage cooling type heat exchanger 9 and the indirect cooling box 10 described above are as follows. That is, in addition to cooling the fired product 12 in the cooling zone Z by blowing cooling air into the cooling zone Z furnace as was conventionally done, in addition to cooling the fired product 12 in the cooling zone Z furnace, the furnace pressure balance in the cooling zone Z furnace is Heat is recovered from the fired product 12 and the trolley 11 as heated air without affecting the heat.

To explain this point, first, cooling air is blown into the cavity wall of the indirect cooling box 10, so that the fired product 12 and the cart The heat accumulated in No. 11 is transmitted and indirectly recovered as heated air while being isolated from the furnace atmosphere. Subsequently, this heated air is supplied to the heat storage cooling heat exchanger 9 through the wind pipe. The heated air from the indirect cooling box 10 is blown through the heat-resistant steel pipes built into the heat storage cooling type heat exchanger 9, so that the outside of the heat-resistant steel pipes is kept warm due to the large heat capacity covering the heat-resistant steel pipes. Similar to the case of the indirect cooling box 10, the heat of the fired product 12 and the trolley 11 stored in the refractory is recovered indirectly as heated air at a higher temperature while being isolated from the furnace atmosphere.

Heated air obtained from the indirect cooling box 10 and the regenerative cooling type heat exchanger 9 is supplied to each burner 15 in the firing zone Y. Since this heated air is clean and does not contain dust or waste gas in the furnace, it can be effectively used as combustion heated air for each burner in firing zone Y, greatly contributing to fuel savings. Can be done.

As described above, in the present invention, the cooling heat of the fired product 12 and the truck 11 in the cooling zone Z of the tunnel kiln can be effectively recovered and utilized as heated air for combustion. Therefore, thermal efficiency can be significantly improved.

In this invention, since the regenerative cooling type heat exchanger 9 and the indirect cooling box 10 are additionally installed in the cooling zone Z of the tunnel kiln, the recovered clean heated air is used as heating air for combustion in each burner 15 of the firing zone Y. It is now possible to supply As a result, we were able to achieve the following remarkable effects.

That is, the heat storage cooling type heat exchanger 9 is placed, for example, at a position in the cooling zone Z where the furnace temperature is approximately 1000°C to 700°C, and the indirect cooling box 10 is placed, for example, at a position where the furnace temperature is approximately 450°C to 300°C in the cooling zone Z. The combustion air is passed through the indirect cooling box 10 and the heat storage cooling type heat exchanger 9 to recover the heat in the cooling zone Z, and as clean heated air heated to approximately 300°C, it is sent to each of the firing zones Y. It became possible to supply it to the burner. Therefore, the fuel consumption is approximately 15% compared to the conventional one.
% could be saved.

Furthermore, by installing the heat storage cooling type heat exchanger 9 and the indirect cooling box 10, in addition to saving fuel, it was possible to achieve the following effects not found in conventional systems. That is, (a) The increase in the cooling capacity of cooling zone Z has made it easier to maintain the pressure balance within the cooling zone Z furnace.

(b) Fired product 12 pushed out of the furnace from the cooling zone Z
and the temperature of the air in the trolley 11 to approximately 100°C to 50°C.
I was able to lower it.

(c) As a result, it became possible to shorten the furnace length of the cooling zone Z by about 10 to 15%.

Note that this invention is not limited to the above-described embodiments.

For example, in the above example, the heated air obtained from the regenerative cooling type heat exchanger and the indirect cooling box installed in the cooling zone was used as combustion air in the burner of the firing zone. Since the heated air is clean and does not contain dust or waste gas, and is stably obtained in the refurbishing furnace, it can be widely used as a heat source for various purposes other than combustion.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing a conventional tunnel kiln, Fig. 2 is a horizontal sectional view thereof, Fig. 3 is a sectional view taken along line A-A in Fig. 1, and Fig. 4 is a tunnel kiln according to the present invention. 5 is a horizontal sectional view thereof, and FIG. 6 is a sectional view taken along line A--A in FIG. 4. 9... Heat storage cooling type heat exchanger, 10... Indirect cooling box, 11... Trolley, 12... Baked product, 13
...Blowing hole, 14...Discharge hole, 15...Burner, X...Pre-heating zone, Y...Calcining zone, Z...Cooling zone.

Claims (1)

[Claims] 1. In a tunnel kiln equipped with a preheating zone, a firing zone, and a cooling zone in sequence, a heat storage device consisting of refractories and heat insulating materials with built-in metal pipes placed on the ceiling and/or side walls of the cooling zone near the firing zone. A cooling type heat exchanger, an indirect cooling box formed by a metal plate and insulation material placed on the ceiling and/or side wall near the outlet side of the cooling zone, and from the indirect cooling box to a storage cooling type heat exchanger. A tunnel kiln characterized in that it has a wind pipe that communicates with the heat exchanger and a wind pipe that communicates with each burner of the firing zone from the heat storage cooling type heat exchanger.