JPS5844114B2 - How to turn tar sludge into fuel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of utilizing tar slag generated in a coke manufacturing process as a fuel for an industrial kiln.

In the refining process of coke oven gas, when the tar contained in the gas is recovered together with the gas-cooled gas liquid and separated by gravity into tar and gas liquid, solids such as coal powder and coke powder that accompany the gas are collected. Materials are also separated and recovered along with the tar and discharged from the system as tar slag.

This tar slag has a solid content of 20-30% and a tar content of 60%.
It has a diameter of ~70 φ and is almost solidified at room temperature, making it extremely difficult to transport and handle, and also poses the problem of environmental pollution.

Therefore, various methods have been proposed in which the slag is slightly diluted and treated in order to separate and recover the solid content and tar content.

For example, Special Publications No. 49-20361, No. 49-20362,
50-14645, 52-19849, 53-9
No. 768, and these are made by adding tar, water, ammonium water, etc. to tar slag, making it fluidized by heating and crushing it to make it easier to handle, and then dispersing the solid content in the tar or separating and recovering it. There is.

However, in these proposals, the reuse of recovered solids is mixed into coking coal or dispersed in tar, and even though the harmful effects of the slag may be reduced, this is not a sufficient effective method of reuse. I can't tell.

In addition, in order to utilize it as fuel for industrial furnaces, a method of extracting it outside the coke factory system and burning it is considered, but the following problems arise when burning cool slag in its original state.

(1) Due to its high viscosity, it cannot be fluidized and cannot be pumped.

Moreover, even if it is transferred by some method, it cannot be atomized for complete combustion and black smoke is likely to be emitted.

(2) Due to its high viscosity, it is extremely difficult to measure and control the flow rate.

Furthermore, even if heated to lower the viscosity, solids will partially settle, making it impossible to measure and control the flow rate.

(3) Even if the solids are fluidized by heating, the particle size and hardness of the solids are very low, so the equipment and burners are subject to severe wear or blockage, and combustion is not completed within the flame, turning into sparks and falling into the furnace. and damage the furnace wall.

Therefore, continuous and smooth combustion cannot be maintained.Due to the above-mentioned disadvantages, there has been no attempt to use slag alone as fuel for industrial furnaces. It is simply used as fuel after being dispersed.

As mentioned above, tar slag is difficult to handle and turn into fuel, so it cannot be effectively utilized industrially by taking advantage of its combustion characteristics, and most of the slag is mixed with coking coal in its original state. Moreover, environmental pollution problems are unavoidable.

The present invention was made to solve these problems, and provides a method for completely eliminating the harmful effects of tar slag and at the same time utilizing it as fuel for industrial kilns.

The present invention will be explained below based on examples.

Tar slag generated from coke factories is in a solidified state at room temperature and usually has properties as shown in Table 1.

In order to utilize tar slag as a fuel for industrial furnaces, it is necessary to make it possible to transport it and to atomize it at the tip of a combustion burner.

Atomization in an oil burner is performed by finely shearing oil using an air flow or steam flow, and the shearing conditions vary depending on the energy of the air flow, the contact between the air flow and the oil, the viscosity of the oil, etc. Determined.

Therefore, for oil in a certain viscosity range, the atomization conditions can be determined by setting the burner type, structure, or usage conditions, such as the energy of the air flow and the contact with the oil.

However, in the case of this tar sludge, the viscosity is significantly higher than that of ordinary oil, so it is necessary to reduce the viscosity to the viscosity range of oil. Figure 2 shows the relationship with the spray particle size and the temperature dependence of tar slag viscosity. According to Figure 1, the viscosity suitable for atomization is 25.
~l 30 cst, and the inventors have determined that in order to obtain this viscosity, the temperature of the tar slag should be adjusted to 80 to 12 cst as shown in Figure 2.
It was found that the temperature needed to be 0°C.

Furthermore, by finely pulverizing the solid content in the slag to increase the specific surface area, it is necessary to maintain the same level of combustibility as the atomized particles, which has been adjusted by selecting the burner model and air flow conditions. Become.

In this case, for the combustion characteristics of the solid content, it is possible to use numerical values related to pulverized coal combustion due to its nature.

An example of the time required to burn pulverized coal is shown in Figure 3, showing the relationship between coal particle diameter and combustion time. In order to burn coal, it is necessary to crush it to 6 microns or less.

However, in industrial kilns, the ambient temperature is high, and the combustion speed of coal grains is greatly affected by this atmospheric temperature. As shown in Figure 4, the higher the temperature, the faster the coal grains burn. In high-temperature industrial kilns, the average particle size of coal is reduced to 50~ by using pulverized coal burners.
It was found that combustion could be completed even at 200μ.

Furthermore, as a special feature of the slag, since it contains a large amount of solid content, even if it is made fine, the solid content still forms pseudo particles and has the same effect as coarse particles.

Therefore, the viscosity of the tar content is lowered and pseudo particles are destroyed.
The particle size of the solid content is slightly lower than the particle size of pulverized coal combustion, and 2
It is necessary to reduce the amount of particles larger than 50μ to 1% or less.

As a result of various experiments regarding this combustion condition, it was found that if the particle size of the solids is 149μ or less to 90% or more, the particle size of 250μ or more can be reduced to 1 or less, and the combustion of the solids can be suitably completed within the flame of the burner. I found out what I got.

By heating and crushing the slag as described above, it has become possible to atomize it at the tip of the burner, that is, to burn it in exactly the same way as normal fuel.

Moreover, this heating and pulverization makes it possible to transport the slag using the pump 1, and it is possible to significantly reduce wear and blockage of the combustion device and burner.

However, even if slag is pulverized, it still contains a large amount of solid content, so it is more likely to wear out and clog equipment than normal fuels such as heavy oil or kerosene. Meter, internal air mixture type, etc. are not suitable for long-term use.

Therefore, in carrying out the present invention, it is desirable to apply the following apparatus.

In other words, the oil pump adopts a diaphragm type pump that has a wear-resistant structure and can supply a fixed amount of oil. In particular, tar slag cannot be used with any flow meter because it is clogged with solids, so the flow rate cannot be controlled. In this respect, since the diaphragm pump is a fixed quantity transfer type, it is possible to control the flow rate.

Furthermore, in order to deal with the abrasion and clogging of the burner oil nozzle caused by slag, an external mixture burner with a simple structure and a large oil nozzle diameter is suitable. is slow and prevents nozzle wear.

Next, processing steps for carrying out the present invention will be explained according to the example shown in FIG.

First, tar slag, which is generated in a coke factory and is solidified at room temperature, is heated in a first heater to a viscosity that can be charged into a crusher.

This viscosity is equal to the pumpable viscosity of 500
Therefore, the slag temperature should be 50°C or higher as shown in Figure 2, but if it is 80°C or higher, odor will be generated significantly, so a range of 50 to 80°C is suitable for pulverization. It can be said that the temperature is

The heated slag is then crushed, but compared to an open type crusher, which has the risk of environmental pollution such as slag scattering and odor generation.
It is preferable to use a semi-closed crusher such as a vibratory mill or a rotary grindstone.

The pulverized particle size is limited by equipment wear and blockage, and the combustion state of solids, but it is appropriate to use a diaphragm pump and an external mixture burner to prevent equipment wear and blockage. If the particle size of the solid is 149,
This can be solved by setting μ to 90% or more.

The slag pulverized in this way is once sent to a storage tank and stored in a warm and stirred state, and then sent to a second heater using a pump and heated to 80 to 120°C.

The reason why the slag is heated to 80 to 120° C. in the second heater is as described above, but especially regarding the maximum temperature (120° C.), there is the following restriction in addition to the above reason.

That is, water and low boiling point organic matter are present in the slag.
This is because the boiling phenomenon begins at around 00°C, which causes pulsation in external mixing burners characterized by low oil pressure, which contributes to incomplete combustion, and the maximum allowable temperature according to experiments is about 120°C. It depends on what happened.

The tar slag heated to 80-120°C in this way is
It completely burns an external air mixture type burner into which air is introduced, and can be used without any problems as a fuel for industrial furnaces such as rotary kilns.

Example 1 To investigate the effect of tar slag temperature on combustion,
Raw tar sludge is processed into a vibration mill to reduce the particle size to 149μ or less, 96.5
Table 2 shows the results of burning the finely pulverized material in an external air mixture burner.
It was found that it could withstand long-term use at 0°C.

Example 2 In order to investigate the influence of tar sludge particle size on combustion,
Table 3 shows the results of combustion in an external air mixture burner at a constant temperature of 100° C. for three types of particles having a particle size of 149 μm or less: 86.5, 91.2°, and 96.5%.

According to this, it can be seen that if the tar slag particle size is 149μ or less in 90% or more, it can withstand long-term industrial use without causing damage to the furnace body.

Example 3 Raw tar sludge was milled with a vibration mill to a particle size of 149μ or less, 96.5
Table 4 shows the state of wear and clogging in the conventional combustion device and the combustion device applied in the present invention using the pulverized material as a test material.

As a result of experiments, it was found that the conventional equipment was not able to stably burn tar sludge due to severe wear and blockage, whereas the combustion equipment to which the present invention was applied was able to completely burn tar sludge even after 200 hours of operation, and the equipment did not wear out. , there was no occlusion.

As described above, according to the present invention, tar sludge, which conventionally had to be mixed into coking coal or dispersed in tar, can be removed.
It can be used on its own as a fuel for industrial kilns, making effective use of waste and preventing environmental pollution at the same time.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between oil viscosity and oil spray particle size for each burner type, Figure 2 is a diagram showing the temperature dependence of tar sludge viscosity, Figure 3 is a diagram showing the time required to burn coal particles, and Figure 4 is a diagram showing the temperature dependence of tar sludge viscosity. 5 is a diagram showing the relationship between the furnace temperature and the combustion rate of coal grains, and FIG. 5 is a processing process chart showing an embodiment of the present invention.

Claims (1)

[Claims] 1 After finely pulverizing tar slag to make the particle size of the combustible solids contained within 149μ or less 90% or more,
A method for converting tar slag into fuel, the method comprising heating it to 120°C and burning it with a burner.