KR20060002677A - Method for preventing of spontaneous combustion and storing problems in coal stockpiles - Google Patents

Abstract

The present invention relates to a method for reducing low burnout problems such as spontaneous ignition and carbonic acid scattering generated in a coal handling station. According to the present invention, when a coal ash slurry having a surface coagulant additive is added to a low coal surface is sprayed according to coal handling. It is possible to reduce problems such as spontaneous ignition, carbon dioxide scattering, and loss of combustion heat efficiency, and it is economical to reuse by-products.

Coal ash slurry, spontaneous ignition, surface coagulant additive

Description

Coal yard spontaneous ignition and low burnout prevention technology using coal ash {METHOD FOR PREVENTING OF SPONTANEOUS COMBUSTION AND STORING PROBLEMS IN COAL STOCKPILES}

1 is a flow diagram of a coal ash slurry spreading device in the present invention.

* Brief Description of Drawings

1. Coal ash slurry preparation tank 2. Surface coagulation additive preparation tank

3. Fly Ash Flow 4, 6. Dilution Water Flow

5. Surface Coagulant Flow 7. Coal Ash Slurry Spray Pump

8. Surface coagulation additive spray pump 9. Coal ash slurry spray nozzle

10. Surface coagulation additive spray nozzle

The present invention relates to a method that is effective in solving problems such as spontaneous ignition, carbon scattering, low coal collapse, and calorie loss, which occur in large-scale coal handling stations (coal fired power plants, steel mills, etc.), in particular surface coagulant additives. The present invention relates to a method of spraying coal ash slurry.

In general, low-carbon countermeasures include sprinkling, crushing, and heat dissipation methods to prevent spontaneous combustion, and passive methods of premature consumption of problem coals are used. In most cases, there is little practicality.

In order to solve some problems in low coal, a conventional method of surface coating on coal piles is to apply surface hardeners (calcite, cement, etc.) to reduce environmental pollution and fuel loss caused by carbonic acid scattering in some steel mills. Although there have been cases where it is applied to the surface or mixed by spraying acrylate polymer resin film, the problem of cracking is caused by simple surface hardening agent alone. Obstacle problems.

On the other hand, there are cases of V. Fierro et al. (V. Fierro et al., "Prevention of spontaneous combustion in coal stockpiles", Fuel Processing) Technology 59 (1999) 23-24).

However, in case of actual application, the surface hardening degree is different according to the type of coal. In case of rain, strong wind, and surface ash, the coal ash is scattered due to surface desorption. In this growing large power plant, problems such as spontaneous ignition and deterioration are continuously raised, and therefore, an economical and effective method that can be applied to all weather is required.

Accordingly, an object of the present invention is to add a surface coagulant additive coal ash which can effectively prevent various problems such as spontaneous combustion, carbon scattering, and calorie loss while having the advantages of low installation cost and operating cost without obstacle to combustion device in coal handling workplace. By using the slurry spreading method, low coal management, environmental management, and combustion management are effectively performed.

In order to achieve the above object, in the present invention, coal ash having a suitable CaO content is mixed with water at a weight ratio of 10-60% to prepare a slurry and sprayed on a low-carbon pile to dry and solidify, and then surface hardening to further harden the coated surface. Provided is a method for reducing spontaneous ignition, carbonic acid scattering, heat loss, etc. in a coal handling site, characterized in that the additive is additionally treated in the range of 0.5 to 75% by weight of water.

Hereinafter, the present invention will be described in detail.

Coal Combustion In the workplaces that use large amounts of coal, such as large-scale power plants, there are many problems in low coal and combustion management due to the use of various coal types. Increase in combustion heat efficiency, increase and decrease of power generation output due to blockage of coal storage facilities (Bunker and coal feeder), environmental pollution and energy loss due to carbon scattering.

All of these low coal disturbances are caused by the penetration of air and moisture into the coal pile. In other words, imported coal briquettes contain chemicals that generate heat by reacting with oxygen in the air depending on the type of coal and degree of coalification. For example, carbonyl group, hydroxyl group and aldehyde group. Therefore, the greater the amount of air and the longer the elapsed time, the greater the heat accumulation and the spontaneous ignition within the low coal pile.

On the other hand, imported coal briquettes have 50-60% of their particle size in the range of 2mm depending on the type of coal. Therefore, during the rainfall, capillary phenomenon rapidly increases the water content as the water flows into the voids between the particles, and again along the flow path. The inflow of air is increased and thermal accumulation is further progressed by the reaction with the chemical. These problems are more common in most subbituminous coals, with higher volatilities and smaller particles.

When burning in a coal-fired power plant, fly ash, which is a large amount of coal, is properly mixed with water to make slurry, and when sprayed, non-ash particles (less than 75μm) in slurry are closed the pores between the particles in the coal pipe. by air, and prevents the penetration of moisture, prevent natural degradation of the ignition and coal, and further, non-rotating, the specific component (CaO, SiO ₂₎ a small amount of dissolution, reaction bonded by amorphous water-insoluble on the surface of the particles when mixed with water Since it has a pozzolan effect to generate and solidify a hydrate coating, it is possible to harden the surface by self-hardening, thereby preventing rain penetration and blocking low carbon. CaO content in fly ash is in the range of 4.5-21.3% (cement 62-66%).

Summarizing the reaction in low coal piles of coal ash slurry

1) Permeability and air inflow blocking by capillary phenomenon of water by particle pore closing action by fine coal ash particles

2) Surface solidification occurs by mutual hydration of CaO, SiO ₂ , Al ₂ O ₃ components with water in coal ash

3) Surface hardening by surface coagulation additive

In general, Fly Ash is mixed with water at a weight ratio of 10-60% to prepare a slurry, and then sprayed on a low-carbon pile. When the product is naturally dried for 2-3 hours after spraying, the surface coating thickness can be 0.5-3 cm. . However, in some cases, scattering and shelling may occur due to a certain amount of epidermal dropout, and in particular, a problem of film breakage and scattering in case of heavy rain (more than 100 mm / hour) or strong wind (more than 14 m / second) Can be expected. This can be solved by additional surface spraying of condensation additives. The coagulant additive is an inorganic additive. Specifically, SiO ₂ or Al ₂ O ₃ and Na ₂ O are the main components. The coagulation time can be adjusted depending on the concentration and drying conditions. Further injection of additives is possible by spraying a suitable concentration of surface coagulation additive on the first solidified coal ash slurry, the preferred concentration being in the range of 0.5-75% by weight of water.

1 is a flow diagram of a coal ash slurry spreading apparatus according to the present invention. Coal ash slurry is prepared in a separate tank (1), which requires the operation of the stirrer to prevent the precipitation of slurry, and when the coal ash (3) is mixed with water, the liquid is strongly alkaline, and the coating treatment and material to prevent wear Selection is necessary. The coagulant additive (5) is also highly alkaline and requires attention to the material when selecting the tank (2). Slurry sprinkling pump (7), injector (8) and nozzles (9, 10) can be applied mutatis mutandis conventional spraying device and liquid spraying device, but it is necessary to select the material and the addition of self-cleaning device after use. In addition, a stacker / reclaimer is installed and operated as a transportation facility at a large-scale coal handling site. have.

According to the present invention, after drying the coal ash slurry, a dry solidification phenomenon occurs in about 3 hours, after that, when the spraying additives are further sprayed, a harder curing phenomenon occurs within a short time to form a hard cured film within 24 hours do. On the other hand, the cured film can form an environmentally friendly coating film according to the trace amount of dye added to the coagulant additive.

The field to which the method of the present invention can be applied may be of all types known in the art, for example, coal-fired power plant, coal-fired steel mill, low coal and coal-fired district heating of a coal-fired power plant, coal-treated steelworks, a plant related to the production, sale and use of coal. There is a workplace.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

Example 1

After preparing the coal ash slurry as shown in FIG. 1, the results of a simple test performed to check the water permeability during rainfall by spraying water with 350gr of sample coal 350gr on a 18mesh sieve (1.0mm) were shown in Table 1.

TABLE 1

* Experimental conditions

A: bullet A (high granular bituminous coal with a particle size of 2mm or less and 51% or more)

B: Sample coated with fly ash fly ash about 2-3mm on A surface

C: Sample dried with fly ash slurry (50wt%) 1-2mm on surface of coal A for 24 hours

D: Sample with bituminous coal Fly Ash (2-3mm) + gypsum (2-3mm) coated on A surface

In the simple experiment for the permeation trend, the water only penetrates water immediately under the condition of coal only (a). Especially, the higher the granularity, the faster the penetration. However, in the coal ash slurry treatment sample (C), only the surface of the coal is wet when spraying, and after drying and solidifying (starting solidification in 2-3 hours), it is only leaking through the body wall surface, and moisture is kept for a long time unless the coating film is destroyed. You can see that it does not pass. From this, it can be seen that in the case of slurry coated coal, rainwater flows along the carbonile slope in a small amount of rainfall without permeability into the coal seam.

Example 2

Experimental results are shown in Table 2 to determine the tendency of spontaneous ignition due to the inflow of air due to long-term low coal by measuring the coal pile of 500 kg externally and measuring the coal bed internal temperature after a certain period of time.

TABLE 2

* Experimental condition:

Pile size: Sample 500kg, Diameter 1.6m, Height 72cm

Temperature measuring position: 15cm below the surface

Outside exposure period: 30 days (covering during rainy weather)

* Cooling effect due to rainfall due to small sample size

Treatment method: Spray and dry bituminous coal fly ash slurry about 2mm

A bullet: 51% or more of particle size less than 2mm, 25% of high volatility bituminous coal

B bullet: less than 33% of particle size less than 2mm, 41% of high volatility

C bullet: 30% of particle size less than 2mm, 31% of volatilized bituminous coal

As can be seen from the above table, the treated samples of coal ash slurry showed little increase in temperature regardless of the type of coal, even in long-term outdoor exposure. This can be said to be applicable because spontaneous ignition occurs mainly in sub-bituminous coal.

Example 3

Although it was confirmed that the coating film of solidified coal ash slurry has the effect of blocking water and air, in actual application, the coating film breakage and detachment phenomenon partially occurred during heavy rain (over 100mm / hour) or strong wind (14M / s). May occur. Surface coagulant additive is to prevent the breakdown and detachment of the coating film, and when additionally sprayed on the coal slurry film formed first, the results of a simple experiment confirming the injection concentration, the setting time and the degree of curing are shown in Table 3 and Table 4.

TABLE 3

TABLE 4

The coagulant additives A and B showed premature curing at water and proper concentration, and A tended to cure in a short time at a lower concentration than B. Generally, as time goes by, the hardenability is increased, but hardening does not occur when the additive solution is administered. This is caused by poor drying in case of the undiluted solution.

According to the present invention, when the surface coagulation additive is additionally treated together with the spraying of the coal ash slurry in the coal handling low coal yard, it is possible to increase the effects of spontaneous ignition, carbonic acid scattering, calorie loss prevention and combustion heat efficiency improvement.

Claims (4)

Method of preventing and burning spontaneous ignition, water increase, carbon scattering, loss of carbon, low coal decay, blockage of coal, combustion and low carbon by forming dry film by preparing and spraying 5 to 60% of ash ash slurry by weight. The coal ash used is imported coal briquette Fly Ash, which is composed of 4-25% CaO and 30-83% SiO ₂ , and is mixed or added with surface coagulant. The surface coagulant additive in paragraph 2) is an inorganic substance. Specifically, Na ₂ O and Al ₂ O ₃ , or Na ₂ O and SiO ₂ are main components. The additive concentration is 0.5 to 75% by weight of water and weight. How to mix and use trace amounts of dye The places where the methods mentioned in 1) 2) 3) are possible include low coal storage at coal-fired power plants, coal handling steel mills, and coal production plants, sales and use of coal;

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