JPS62121786A - Method of drying coking coal - Google Patents

Abstract

PURPOSE:To appropriately dry coking coal without dangers of explosion of coal dust etc., by charging a heating container with coking coal and passing a carrier gas comprised of a combustion exhaust gas contg. a low level of oxygen. CONSTITUTION:A dryer 1 is provided in its inside with a heat transfer pipe. A heating medium is passed from the outside of the dryer through the heat transfer pipe, thereby heat-drying the charged coking coal (A). The coking coal (A) is continuously charged into the dryer through a charging hole 2 provided at one end of the dryer and is discharged after heating through a discharging hole 3 provided at the other end of the dryer. A carrier gas is fed into the dryer 1 through one end of the dryer, and the gas which entrains water evaporated through heating from the coking coal is discharged outside the container. The discharged carrier gas contg. coal dust is discharged after the removal of the dust with a dust collector 4. In the drying process of the coking coal, a combustion exhaust gas contg. a low level of oxygen is used as the carrier gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for drying coal, which is a raw material for coke production.

[Conventional technology and its problems]

Coking coal used in coke oven operation usually contains about 8 to 9 mos of water on average. If such coking coal is used as it is, approximately 40 to 50% of the heat of carbonization is used to evaporate the water, and moreover, evaporation of the water in the coking coal normally requires about 1.5 times the heat of evaporation. Therefore, by lowering the coking coal moisture content, a very large energy saving effect can be obtained in terms of coke oven operation. In addition, as the coking coal moisture content decreases, the packing density improves, and improvements in coke productivity and quality can also be expected.

On the other hand, the moisture content of coking coal varies from 7 to 1,396 degrees depending on weather changes, etc.
It fluctuates within a range of , and this fluctuation occupies a large proportion of the factors controlling the variation in actual coke strength. Therefore, by suppressing fluctuations in the moisture content of the coking coal and maintaining it at a low constant level, not only the above-mentioned energy saving effect but also the accuracy of coking coal blending management can be achieved, making it possible to achieve an optimal economical blending.

For this reason, installing coal humidity control equipment (dryer) in coke manufacturing equipment to perform humidity control processing (drying processing) of coal has recently been attracting attention, and there have been many reports as an effective drying method. Coking coal is continuously charged into a dryer with heat tubes from one end, the heating medium is passed through the heat transfer tubes to indirectly heat the coking coal, and the heated and dried coking coal is transferred to the other end. A so-called multi-tube rotary heating dryer is known in which evaporated water is discharged outside the dryer by passing a carrier gas through the dryer during heating drying.

However, when coking coal is dried using this type of method, coal dust explosions tend to occur when the moisture content of the coking coal becomes low.In particular, when the moisture content is less than 5 liters, the amount of dust generated increases rapidly and coal dust A major problem is the increased risk of causing an explosion.

[Means to solve the problem]

In view of these problems, the present invention aims to provide a method that can appropriately dry coking coal without causing dangers such as coal dust explosion.

The present inventors first investigated the causes of coal dust explosions during coal drying. As a result, it was found that coal dust explosions are closely related to three conditions: (1) oxygen concentration in the atmosphere, zero dust generation amount, and (2) ambient temperature.

By the way, as mentioned above, it is necessary not only to simply reduce the moisture content of raw coal but also to control the moisture content after drying to a constant level in order to ensure the accuracy of raw coal blending management.

In the dryer described above, a method is adopted in which the moisture content on the moisture-adjusting coal discharge side is controlled to a constant level.
There are changes in the flow rate and temperature of the carrier gas introduced into the dryer container to discharge evaporated water. However, since the carrier gas is the gas that makes up the atmosphere inside the dryer,
Changes in the flow rate and temperature have an extremely large effect on the above three conditions that govern coal dust explosions, creating a major problem in terms of safety measures.

Taking these circumstances into consideration, we conducted further studies and found that by using combustion exhaust gas with a low O8 concentration as a carrier gas, we were able to perform humidity control processing without causing a coal dust explosion, and at the same time, the gas temperature It was found that the moisture content can be easily controlled by adjusting the flow rate. That is, the present invention provides a method for drying coke coking coal in which coking coal is placed in a heating container, and during heating of the coking coal, a carrier gas is passed through the heating container to discharge evaporated water to the outside of the heating container. , as a carrier gas, low O! Its basic feature is that it uses concentrated combustion exhaust gas.

The present invention will be specifically explained below.

Figure 1 shows a dryer (1) for coking coal.
The dryer (1) has a heat transfer tube therein, and heats and dries the loaded raw coal by passing a heating medium through the heat transfer tube from the outside.

Coking coal (A) is continuously charged into the dryer from the charging port (2) at one end, heated and dried, and then passed through the discharge port (2) at the other end.
3) is discharged from. A carrier gas is introduced into the dryer (1) from one end of the dryer (1) so as to entrain moisture evaporated from the raw coal by heating and remove it from the container. The carrier gas accompanied by evaporated water is discharged from the other end of the dryer (1), and since it contains dust, it is discharged after being removed by a dust collector (4).

In the present invention, a low 0° concentration combustion exhaust gas is used as a carrier gas in the coking coal drying process.

FIG. 2 and FIG. 3 show the relationship between the atmospheric oxygen concentration, atmospheric temperature, and powder ruggedness, and the coal dust explosion limit, as investigated by the present inventors. Of these, Figure 1 and 2 show the relationship between the oxygen concentration and ambient temperature in the dryer (1) and the gas ignition range, and Figure 3 shows the relationship between the oxygen concentration and dust concentration and coal dust explosion. According to Figure 2, the dust concentration is 0.2 f/L.
If the oxygen concentration is 3% or less, the ambient temperature is 20
There is no danger of coal dust explosion up to 0°0, and according to Figure 3, when the ambient temperature is 10 G'O, the oxygen concentration is 12.5.
% or less, there is no danger of a coal dust explosion regardless of the dust concentration.Therefore, from these, a coal dust explosion can be caused by using exhaust gas with an oxygen concentration of 34 or less as a carrier gas with an exhaust gas of about 200°0. Drying of coking coal can be carried out without creating any danger. The upper limit of the oxygen concentration of the carrier gas used varies depending on the carrier gas temperature, and has the relationship shown in Table 1, for example.

Table 1 Carrier gas of the present invention 1 As the combustion exhaust gas used, blast furnace hot air Pmff gas, coke oven combustion exhaust gas, etc. shown in Table 2 can be used.

Table 2 These exhaust gases are generally 2% or less in concentration,
As is clear from FIGS. 2 and 3, the risk of coal dust explosion can be appropriately avoided even if the flow rate and temperature of the carrier gas are set within an arbitrary range.

〔Example〕

FIG. 4 shows an embodiment of the coal drying method according to the present invention using low-pressure steam as the heating medium, and is an example in which coke oven combustion exhaust gas is used as the carrier gas. As shown on the right, by using coke oven combustion exhaust gas of about 170 to 180°0 as the carrier gas, the amount of steam used can be reduced to 2.3 T/H (
26,4T/H→24. IT/H) can be reduced.

〔Effect of the invention〕

According to the present invention described above, coking coal can be dried under controlled humidity without causing any danger of coal dust explosion. In addition, since combustion exhaust gas is used as a carrier gas,
This sensible heat can be used to heat the coking coal, reducing the amount of heat required to be supplied from the heat medium (steam, oil, etc.) supplied for heating, and thereby reducing the area of the heat transfer tube of the dryer. , it is possible to reduce the burden on equipment.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a coke coking coal dryer. FIG. 2 shows the relationship between oxygen concentration, ambient temperature, and gas ignition range in the coking coal dryer. Figure 3 shows the same oxygen concentration and powder! This figure shows the relationship between I concentration and coal dust explosion area. FIG. 4 is an explanatory diagram showing one embodiment of the present invention. In the figure, (1) is a dryer, and (A) is raw coal. Special pestle applicant Nippon Kokan Co., Ltd. Inventor Fumi Fujii Rodo
Kitajima - Tsugu, Patent Attorney
Sho Yoshihara Sando High School
Kiyodo Hashi Attorney Yoshi
Hiroko Kui ('5/[5)

Claims (1)

[Claims] Coking coal is continuously charged from one end into a dryer having a heat transfer tube, and the coking coal is heated indirectly by flowing a heating medium through the heat transfer tube, and is heated and dried. In a method for drying coke coking coal, in which coke coking coal is sequentially discharged from the other end and evaporated moisture is discharged outside the dryer by circulating a carrier gas inside the dryer during heating drying, the coke coking coal is used as a carrier gas. A method for drying coking coal, characterized in that low O_2 concentration combustion exhaust gas is used.