KR101917465B1 - Coal water slurry comprising sludge containg calcium and method for preparing the same - Google Patents

Abstract

The present invention relates to a coal-water slurry comprising coal and water, said slurry comprising a calcium-containing sludge. According to the present invention, a calcium-containing sludge, which is a by-product generated in a steelmaking process, can be added during the production of a coal-water slurry to provide a coal-water slurry capable of lowering the viscosity of the coal-water slurry and increasing the concentration of coal. In addition, the efficiency of the wet coal gasifier and the combustor (reactor, internal combustion engine) using the coal-water slurry can be increased by increasing the heat generation amount.

Description

TECHNICAL FIELD The present invention relates to a coal-water slurry containing calcium-containing sludge and a method for producing the same. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coal-

The present invention relates to a coal-water slurry comprising calcium-containing sludge and a process for its preparation.

Recently, in order to reduce dependence on petroleum and reduce energy source unit, technology is being actively developed for replacing expensive oil with cheap coal. However, it is impossible to convert coal to conventional boilers or urine by conventional combustion methods. Therefore, coal-water slurry fuel can be used only by modifying existing oil-fired combustion equipment, and its use is spreading because it is easy to transport, store and burn in a liquid state.

Generally, coal-water slurry fuel is a liquid fuel obtained by pulverizing and mixing coal, water and a small amount of additives. When a coal-water slurry is prepared without using additives other than coal and water, the viscosity of the slurry becomes high, and a slurry with a high coal concentration can not be produced. When the coal concentration is low, the transportation efficiency is lowered and the dehydration process is required again before the combustion, so that there is a problem that additional cost is required.

 In order to increase the concentration of coal slurry, a method of introducing a surfactant has been disclosed. However, in the case of a high concentration technique using a surfactant, it is difficult to utilize it in a commercial facility because of economical problems.

On the other hand, in the field of coal gasification, usually two types of methods are used to supply coal to a gasifier for gasification. One is a dry method of spraying coal into a gasifier by transferring coal to the air with pressurized nitrogen.

The other is a wet method of producing a slurry of coal and water and feeding the coal-water slurry to the gasifier. Coal-water slurries have been widely used because they are easier to move relative to the method of using coal in a dry state and can be applied to higher gasification pressures.

In general, high coal concentrations in coal-water slurries lead to high gasification efficiencies and low coal and oxygen consumption. Therefore, coal-water slurry for use in a wet coal gasifier process preferably has a high coal concentration.

Attempts have been made to increase the coal concentration. For example, there is a method of changing the particle size distribution of a coal-water slurry. However, alteration of the coal particle size distribution can cause unwanted viscosities in the coal-water slurry.

On the other hand, in the steel making process using iron ore and coal, which are representative raw materials, by-products of various forms and compositions are generated depending on the physical properties of raw materials. Although processes for extracting the necessary components to utilize the byproducts have been introduced, there are disadvantages in economical efficiency when a specific process is developed to utilize the byproducts. If the byproducts are not utilized, there is a problem in cost of disposal.

In order to solve the above problems, the present invention provides a coal-water slurry, which is a byproduct of a steelmaking process, added to coal-water slurry during the production of the coal-water slurry to lower the viscosity of the coal- .

The present invention also provides a method for producing the coal-slurry.

According to one embodiment of the present invention, in a coal-water slurry comprising coal and water, the slurry is provided with a coal-water slurry comprising calcium-containing sludge.

The calcium-containing sludge may be a waste of a steelmaking process.

The calcium-containing sludge content may be 20 to 40 wt% based on the ash content of the coal.

The coal may have a ash content of 6 wt% or less.

The coal may be at least one selected from peat, lignite, bituminous coal, bituminous coal and anthracite coal.

The coal may be small coal having a particle size of 45 탆 or less, medium-sized coal having a particle size of 45 탆 to 200 탆 and large coal having a particle size of 200 탆 to 300 탆.

1 to 30% by weight of the small coal, 60 to 98% by weight of the medium coal and 1 to 10% by weight of the large coal.

The viscosity of the coal-water slurry may be 500 to 2000 Cp.

According to still another embodiment of the present invention, there is provided a method for producing coal, comprising: pulverizing coal; Adding water and calcium-containing sludge to the pulverized coal to prepare a mixture; And pulverizing the mixture. A method for producing a coal-water slurry is provided.

The calcium-containing sludge may be a waste of a steelmaking process.

The calcium-containing sludge content may be 20 to 40 wt% based on the ash content of the coal.

The coal may have a ash content of 6 wt% or less.

The coal may be small coal having a particle size of 45 탆 or less, medium-sized coal having a particle size of 45 탆 to 200 탆 and large coal having a particle size of 200 탆 to 300 탆.

The pulverization may be performed with any one selected from a rod mill and a ball mill.

According to one embodiment of the present invention, a calcium-containing sludge, which is a byproduct generated in a steelmaking process, is added during the production of a coal-water slurry to provide a coal-water slurry capable of lowering the viscosity of the coal- can do.

In addition, the efficiency of the wet coal gasifier and the combustor using the coal-water slurry can be increased by increasing the heating value.

1 shows the viscosity of Example 1 and Comparative Example 1 in accordance with the concentration of the coal-water slurry.

Hereinafter, preferred embodiments of the present invention will be described with reference to various embodiments. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

According to one embodiment of the present invention, in a coal-water slurry comprising coal and water, the slurry is provided with a coal-water slurry comprising calcium-containing sludge.

Generally, the coal-water slurry may comprise from about 55 wt.% To about 70 wt.% Coal particles, from about 30 wt.% To about 45 wt.% Water and less than 1 wt.% Additive, The concentration is determined by the type of coal, the distribution of the particles, and the chemical characteristics of the particles.

Among the various methods of producing slurry fuel having a high coal component ratio by decreasing the viscosity in the coal-water slurry, the most convenient and universally used is to mix the chemical additives and the dispersing agent of the water-soluble surfactant type Is used.

Generally, the proportion of additives mixed in coal-water slurry is less than 1% by weight, but the proportion of additives in manufacturing cost is more than 20% of the total. Therefore, developing high performance and low cost additives is a very important factor to be considered for producing high concentration coal-water slurry fuels.

The calcium-containing sludge added to the coal-water blended fuel in the present invention may be derived from the wastes of the iron-making process.

The steelmaking process consists of steelmaking, steelmaking, and rolling. In the steelmaking process for producing pig iron from blast furnace and coke limestone, reduction and melting of ores are the main objectives and emissions are generated most during the entire production process.

In the steelmaking process, oxygen is injected into a refining furnace using a basic oxygen furnace (BOF) to remove impurities such as excess carbon, silicon and phosphorus in the charcoal. In electric furnace steelmaking, which uses scrap as a raw material, scrap is dissolved and refined by using electric power and oxygen, and waste such as slag electric furnace dust is generated in this process.

In addition, steel refined steel is manufactured through intermediate process such as slab broom or billet through casting process. This intermediate material is regulated in material and surface quality through reheating and hot rolling forming process, .

Various kinds of wastes are generated in the manufacturing process of such products. Researches are being conducted in various fields to reduce the cost incurred in disposing of various by-products of the steel making process and to utilize them as new applications.

The present inventors have found that when the calcium-containing sludge is added during the production of the coal-water slurry in the wastes of various steel making processes as described above, the viscosity can be lowered and the concentration of coal can be increased, and the present invention has been accomplished.

The composition of the calcium-containing sludge generated as a by-product of the steel making process is shown in Table 1 below.

Kinds SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO Na ₂ O K ₂ O SO ₃ Etc. Ca sludge 3.18 1.65 1.87 53.5 3.11 0.066 0.283 0.109 36.106

Referring to Table 1, the calcium-containing sludge added to the coal-water slurry in the present invention contains a large amount of calcium oxide (CaO), and the calcium oxide reacts with water to be absorbed, exothermic, and expanded to become calcium hydroxide. The reaction formula is as follows.

CaO + H ₂ O -> Ca (OH) ₂ +15.6 mol ^-1

That is, when the sludge containing a large amount of calcium oxide is mixed with the coal-water slurry having a high water content, calcium hydroxide may be generated in the above reaction and the water content of the coal-water slurry may be reduced. In addition, since the heat generated by the reaction evaporates moisture, the viscosity of the coal-water slurry can be further reduced, thereby making it possible to produce a coal-water slurry having a high concentration.

On the other hand, coal ash means a residue of incombustible remaining after the coal is completely burned. It is also possible to use an acidic component such as SiO ₂ , Al ₂ O ₃ , TiO ₂ and the like such as Fe ₂ O ₃ , CaO, MgO, Na ₂ O It is composed of basic ingredients. The composition of coal ash is shown in Table 2 below.

Kinds SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO Na ₂ O SO ₃ P ₂ O ₅ TiO ₂ Mn ₃ O ₄ Abundance
(%) 40-60 15-35 5-25 1-15 0.5-8 1-4 0.5-20 0.1-1.5 0.1-2 0.02-1

Generally, when a large amount of acidic components such as SiO ₂ , Al ₂ O ₃ and TiO ₂ contained in the coal ash has a high melting point, a large amount of basic components such as Fe ₂ O ₃ , CaO, MgO and Na ₂ O lowers the melting point.

Referring to Tables 1 and 2, the calcium-containing sludge added to the coal-water slurry in the present invention contains not only a large amount of calcium oxide (CaO) but also a base such as Fe ₂ O ₃ , K ₂ O, MgO ≪ / RTI >

That is, in the case of a wet gasifier using coal-water slurry, it is important to lower the melting temperature of the coal ash in terms of energy efficiency. As shown in Table 2, calcium-containing sludge generated as a by-product of the steel making process contains a large amount of basic calcium oxide.

Therefore, when the calcium-containing sludge is added to the coal-water slurry, the basic component of the coal ash is increased and the melting temperature can be lowered. Thus, the wet coal gasifier and the combustor using the coal- The efficiency of the engine can be increased.

On the other hand, if the addition amount of the calcium-containing sludge is increased, the calorific value of the coal-water slurry can be reduced.

Therefore, in the present invention, the content of calcium-containing sludge may be 20 to 40% by weight, preferably 25 to 35% by weight based on the ash content of the coal. If the content of the calcium-containing sludge is less than 20 wt%, the content of coal in the slurry may be excessively small. If the content of the calcium-containing sludge is more than 40 wt%, the melting point of the coal ash may be increased to reduce the efficiency of the gasifier.

The coal may have an ash content of 6 wt% or less (excluding 0), and preferably 3 wt% or less (excluding 0). It is preferred that the ash content of the coal is less than or equal to 6% by weight in order to reduce the energy of melting the coal ash in the gasifier.

The coal used in the production of the coal-water slurry in the present invention is not particularly limited, and for example, at least one selected from peat, lignite, bituminous coal, bituminous coal and anthracite can be used.

Coal can be classified into peat, lignite, bituminous coal, bituminous coal and anthracite coal depending on the carbon content. Generally, low carbonized coal such as peat, lignite and bituminous coal has high inherent moisture content and is used as a high concentration coal- However, when the calcium-containing sludge according to the present invention is added to the coal-water slurry, it is possible to produce the low carbonized coal with a high concentration of the coal-water slurry fuel, which is advantageous in cost.

The coal may be small coal having a particle size of 45 μm or less (excluding 0), medium-sized coal having a particle size of 45 μm to 200 μm, and large-sized coal having a particle size of 200 μm to 300 μm.

A high concentration of coal-water slurry can be produced by controlling the particle size of the coal in the production of the coal-water slurry to reduce the porosity between the particles to have the maximum filling density.

Particularly, when coal having a different size is mixed to produce a high concentration coal-water slurry, the larger the average grain size of the large coal and the smaller the average grain size of the small coal, the higher the coal concentration in the coal-water slurry.

However, if the average particle diameter of the coal is too large, problems such as a decrease in the stability of the coal-water slurry, clogging of the nozzle of the sprayer, generation of unburned carbon after combustion occur, and if the average particle diameter is too small, The problem of falling occurs.

Accordingly, in the present invention, the coal is preferably a mixture of 1 to 30% by weight of small coal having a particle size of 45 탆 or less, 60 to 98% by weight of medium coal having a particle size of 45 탆 to 200 탆 and 1 to 10 Water slurry can be produced by mixing coal to water to reduce the amount of water filling the space between the coal particles to a minimum and to provide a high concentration of coal-water slurry with a high percentage of coal.

Meanwhile, the calcium-containing sludge according to the present invention may have a viscosity of 500 to 2000 Cp.

According to still another embodiment of the present invention, there is provided a method for producing coal, comprising: pulverizing coal; Adding water and calcium-containing sludge to the pulverized coal to prepare a mixture; And pulverizing the mixture. A method for producing a coal-water slurry is provided.

The step of pulverizing coal can be carried out by appropriately selecting among known pulverizing methods, and is not particularly limited, but can be carried out using, for example, a roll mill, a pin mill, a hemm mill, a ball mill and a wet pulverizer.

As described above, in the present invention, it is preferable to mix small-sized coal having a particle size of 45 μm or less, medium-sized coal having a particle size of 45 μm to 200 μm, and large-sized coal having a particle size of 250 μm to 350 μm. Accordingly, two or more kinds of coal having different grain sizes can be produced through a pulverizing process.

Water and calcium-containing sludge are added to the pulverized coal to prepare a mixture. At this time, the content of the calcium-containing sludge and the ash content of the coal have been described above, and thus a detailed description thereof will be omitted.

Finally, in preparing the coal-water slurry by pulverizing the mixture, the pulverization may be carried out using a rod mill, a ball mill or the like, preferably using a rod mill.

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

Example 1

30 wt% of coal having a particle size of 45 탆 and 10 wt% of coal having a particle size of 250 탆 were prepared and mixed with 60 wt% of coal having a particle size exceeding 45 탆 and less than 250 탆 to prepare a mixed coal.

Water and calcium-containing sludge were added to the mixed coal to prepare a mixture.

The mixture was pulverized in a rod mill to prepare a water-coal slurry and the viscosity of the slurry was measured according to the concentration.

Meanwhile, the ash content of the used coal was 4.5 wt%, and the other specific compositions are shown in Table 3 below.

Industrial analysis
(wt%) moisture 14.10 Volatile substance 38.70 Fixed carbon 42.70 Ash 4.50 Component analysis
(wt%) C 76.08 H 5.42 O 15.96 N 1.52 S 1.02 Calorific value 5542.00

Comparative Example 1

A coal-water slurry was prepared in the same manner as in Example 1, except that no calcium-containing sludge was added.

Fig. 1 shows the results of measuring the viscosity of the coal-water slurry according to the concentration of the coal-water slurry in Example 1 and Comparative Example 1. Fig.

In the coal-water slurry of Comparative Example 1, the concentration of coal was 55.7 wt% at 1000 cP, while that of Example 1 was 56.4 wt% at 1000 cP, indicating that the concentration of 0.7 wt% was increased. On the other hand, at 2000 cP, the coal-water slurry according to the comparative example had a coal concentration of 57.9 wt%, whereas Example 1 contained 58.6 wt%.

That is, when the calcium-containing sludge is added to the coal-water slurry at 30 wt% of the coal ash at 1000 cP to 2000 cP, the concentration of 0.5 to 0.7 wt% is increased.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (14)

In a coal-water slurry comprising coal and water,
Wherein the slurry comprises calcium-containing sludge,
Characterized in that the calcium-containing sludge content is 20 to 40% by weight relative to the ash content of the coal.
The method according to claim 1,
Wherein the calcium-containing sludge is a waste of a steelmaking process.
delete The method according to claim 1,
Wherein the coal has a ash content of 6 wt% or less.
The method according to claim 1,
Wherein the coal is at least one selected from peat, lignite, bituminous coal, bituminous coal and anthracite coal.
The method of claim 1, wherein
Wherein the coal is composed of small-sized coal having a particle size of 45 μm or less, medium-sized coal having a particle size of 45 μm to 200 μm, and large-sized coal having a particle size of 200 μm to 300 μm.
The method according to claim 6,
Wherein the coal-water slurry comprises 1 to 30 wt% of the small coal, 60 to 98 wt% of the medium coal, and 1 to 10 wt% of the large coal.
The method according to claim 1,
Wherein the coal-water slurry has a viscosity of 500 to 2000 Cp.
Pulverizing coal;
Adding water and calcium-containing sludge to the pulverized coal to prepare a mixture; And
And pulverizing the mixture,
Characterized in that the calcium-containing sludge content is 20 to 40% by weight relative to the ash content of the coal
A method for producing a coal-water slurry.
10. The method of claim 9,
Wherein the calcium-containing sludge is a waste of a steelmaking process.
delete 10. The method of claim 9,
Wherein the coal has a ash content of 6 wt% or less.
10. The method of claim 9,
Wherein the coal is composed of small-sized coal having a particle size of 45 μm or less, medium-sized coal having a particle size of 45 μm to 200 μm, and large-sized coal having a particle size of 200 μm to 300 μm.
10. The method of claim 9,
Wherein the pulverization is performed by any one selected from a rod mill and a ball mill.

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