JPS58215492A - Preparation of concentrated coal/water slurry with good fluidity - Google Patents

Abstract

PURPOSE:To prepare a concentrated coal/water slurry with excellent fluidity, by adding inert spherical fine particles with a specified diameter to an aqueous slurry of coal. CONSTITUTION:Fine powder consisting of spherical inert/particles with an average diameter of 0.5mm. or smaller (e.g. fly ash) is added in an amount of 5- 10wt% to a concentrated aqueous slurry of coal prepared by suspending pulverized coal in water. EFFECT:The fine particles are presumed to be positioned between coal particles together with water and act as a bearing material to facilitate move of coal particles leading to formation of a slurry with required fluidity even when water is present only in a small amount.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a highly concentrated coal-water slurry having good fluidity.

In recent years, many large-scale coal projects have been planned to utilize coal as an energy source, but coal generally has a calorific value of 50 to
Since coal is small (80%), it has to be handled in a large amount, and since it is solid, it generates coal dust and oxidizes in the air, making it difficult to transport and handle. In order to achieve this goal, we will improve the efficiency, cleanliness, and safety of various facilities such as ships, ports, and cargo handling facilities, as well as facilities for environmental and disaster prevention measures, on a scale that Japan has never experienced in the past. It is desirable to establish handling technology to achieve this goal, and it is important to ensure the reliability of coal procurement, reduce the related expenses added to fuel costs as much as possible, and meet various conditions to be accepted by the local community at the time of location. It has become a challenge.

As one solution to this problem, a proposal has been made to crush solid coal, mix it uniformly with a fluid to form a slurry, and treat it as a fluid in the same way as petroleum. However, coal and water slurry is considered to be a promising method, with examples of practical use in the United States as a method for transporting large quantities of coal reliably, and large-scale projects using this slurry being planned around the world. There is.

However, this coal-water slurry'J-1ce requires securing a large amount of raw water and large-scale dewatering and wastewater treatment at the end of transportation or before combustion. For this reason, some areas often become bottlenecks for planned routes.

Therefore, it is desirable to make a highly concentrated slurry with as little amount of mixed water as possible. (The amount of mixed water is sufficiently small.
Research is also progressing from the furnace side so that highly concentrated slurry with i<L can be directly injected into the furnace as a fluid fuel in place of petroleum. ) However, if the amount of mixed water is reduced, the fluidity of the slurry decreases1~, and it loses its function both in terms of handling and as a fuel.

Even when the particle size distribution of general F1 crushed coal powder is properly adjusted, if the coal/slurry ratio is higher than about 55% by weight, the slurry becomes clay-like and solidifies, making pipe transportation difficult. . In addition, crushed coal has an angular particle shape, and coal is hydrophobic, meaning that the surface of the particles lacks wettability with water. It is thought that the level of lK- significantly decreases the ;f: By adding chemical agents such as trowels and surfactants to completely improve the properties of the surface of coal particles against water, and by facilitating mutual movement between particles, good fluidity can be achieved with a small amount of water. Methods have already been proposed. However, adding such chemical-based substances to fuel materials may affect fuel equipment and smoke exhaust properties, and since a huge amount of slurry is handled, there are risks of side effects. One must also be prepared for the accumulation of chemicals, and such chemical agents are generally expensive and unsuitable for mass consumption.

The present invention aims to completely increase the fluidity of coal-water slurry and further reduce the amount of added water, without using chemical agents that are associated with such problems to improve the wettability of coal particles with water. It was done for a purpose.

For this purpose, the present invention has an average particle size of 0.5 mrn.
Fine powder consisting of the following substantially spherical inert fine particles,
The present invention provides a method for obtaining a highly concentrated coal-water slurry with good fluidity by blending coal and water in an amount of 10% by weight or less based on the total amount of coal and water. Here, inert fine particles mean physically and chemically stable fine particles that do not dissolve in water, react with coal and water, or undergo metamorphosis. For example, a vitreous material mainly composed of silicon dioxide is suitable. and,
Preferably, such inert fine particles have a substantially spherical shape. More specifically, such substantially spherical inert fine particles include fly ash, which is pulverized coal combustion ash, volcanic ash, and artificial glass bulb powder.

This fly ash is extracted from the flue gas of a pulverized coal-fired boiler.The ash contained in the coal melts during combustion, and it reaches the flue along with the combustion gas, and when the temperature drops, It solidifies into a spherical shape due to its surface tension, and although it contains a very small amount of non-spherical particles such as unburned carbon, it is made up of substantially spherical fine particles with a diameter of 0.1 m or less. The component -f: has a large amount of 5-SiO□, and usually 45% by weight or more is 5i02. (Compared to other similar powders, this fly ash is stably available in terms of quality and quantity, and is also inexpensive.) On the other hand, this fly ash is unavoidably necessary when used as a coal-oil alternative energy source. It is predicted that a large amount of coal will be generated, and the major challenge of coal usage projects is to increase its utilization as much as possible. Therefore, the present invention [,1: It is also very useful in finding new uses for ash. In addition, the discovery of a new use for this fly ash in a coal utilization project means that its recovery and partial reuse can be done in an integrated manner, which has the effect of killing two birds.

In this way, the present invention provides chemically and physically inert fine particles such as fly ash, consisting entirely of glass-like, substantially spherical particles, which can be added to a coal-water slurry in a small amount. 6 - Good fluidity T: Yes, but the amount added should be 10% by weight or less based on the total amount of coal and water, and in the case of fryer sonyu, the amount added is about 5 weight φ However, as shown in the examples below, the flow characteristics are about 1
Reduce the amount of water added by about 0%? <1. But you can get it. The reason why the flow characteristics of the coal-water slurry are improved by adding such chemically and physically stable fine powder is that these fine particles interpose together with water between coal particles and act as a bearing material. lc, l: It is thought that mutual movement of coal particles becomes easier and a slurry having all the required fluidity can be obtained even with a small amount of water. In this respect, it is presumed that the fluidity improvement mechanism is fundamentally different from that of the conventional chemical agent VCX, which improves the wettability of coal particles to water. does not change its effectiveness in slurry or in the atmosphere, can withstand long-term storage and long-term use, and at the same time has advantages that chemical agents cannot obtain in terms of ease of use.
It is also extremely advantageous in terms of price. In addition, even during coal combustion, the components of the glassy powder are of the same quality as the ash originally contained in the coal, so it is advantageous in that it does not have any effect on boiler equipment or exhaust gas equipment. It can be used with existing equipment, and there are many benefits such as no special smoke exhaust measures required.

Examples of the present invention are listed below.

Pulverized coal crushed to a particle size of 3 or less, and a particle size of 20 to 30μ
A mixture consisting of 7 ml of frying fluid, water, and water was placed in a container 1 shown in FIG. 1 with appropriate mixing ratios, and its flow characteristics were measured. For measurement, when a stirring blade 3 for stirring a mixture 2 in a container 1 is rotated by a motor 4, its rotational speed is measured by a reflector 5 attached to its rotating shaft and a reflective rotational speed measuring device 6. At the same time as the measurement, the amount of current to the motor 4 was measured using an ammeter 7VC, and the required stirring torque (Tl'i) was calculated using the following formula.

T=K.- However, T: Torque (kg - cx IK; Stirrer specific coefficient T; Current (A) n: Number of rotations (rpm) Representative values of the measurement results are shown in FIGS. 2 and 5.

In both figures, the vertical axis q1 is expressed as the ratio of the torque of the mixture to the torque in the case of only water (torque ratio). -! Furthermore, in both figures, the broken line (a) shows the control example when no fly ash was added, and the solid line (b) shows the value when 5% by weight was added to the total amount of the fly ash mixture. Second
The figure shows the relationship between water volume ratio (water volume/total weight) and torque ratio, and Figure 3 summarizes the relationship between coal ratio (coal volume/total weight). The same level of fluidity as fly ash-added slurry IJ-H1 compared to additive-free slurry (dashed line) can be obtained with a small amount of water added (approximately 10% less), and it is also effective in increasing the amount of coal. I understand. Therefore, it is clear that according to the present invention, a highly concentrated coal-water slurry with good fluidity can be obtained, and it is possible to improve transportation efficiency and save labor and equipment such as dehydration in the pre-combustion process. .

[Brief explanation of drawings]

Figure 1 is an equipment layout diagram to explain the method for measuring flow characteristics of coal-water slurry, Figure 2 is a relationship diagram between water volume ratio and tonnage V ratio, and Figure 6 is a relationship diagram between coal ratio and torque ratio. It is a diagram. Applicant: Kajima Corporation 10- Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) To obtain a coal-water slurry by dispersing pulverized coal in water, fine powder consisting entirely of substantially spherical inert fine particles with an average particle size of 0.5i71 or less is mixed with coal and water. A method for producing a highly concentrated coal-water slurry with good fluidity, characterized in that the slurry is blended in an amount of 10 weight plates or less based on the total weight. (2) The manufacturing method according to claim 1, wherein the fine powder consists essentially of vitreous spherical particles having an average particle diameter of OAmm or less. (3) The manufacturing method according to claim 1 or 2, wherein the fine powder is fly ash.