JPS59149989A - Preparation of coal/water slurry - Google Patents

Abstract

PURPOSE:To prepare coal/water slurry having high concn. of coal of a particle size suitable for fluid gasification and capable of being stably supplied without sedimentation, by adding and mixing water compounded with a thickening agent and a surfactant, with coal adjusted in particle size. CONSTITUTION:Coal 15 adjusted in particle size and consisting of 60-75wt% coarse coal of a particle size of about 0.25-1mm. and 40-25wt% fine coal of a particle size <= about 0.25mm., is formed by crushing and classifying coal 11 by using a rough crusher 101 and fine crusher 102. Water 20, a thickening agent 21 such as polyethylene oxide and a surfactant 22 such as sodium alkylbenzene- sulfonate are fed into a mixing tank 201 and mixed by agitation. The obtd. liquid medium 25 is fed along with said coal 15 adjusted in particle size to a mixing tank 202 and mixed/agitated to prepare coal/water slurry (marks 24 and 31 each represent a pump).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for producing a coal-water slurry particularly suitable for use in a fluidized bed coal gasifier.

[Prior art]

Since coal is solid and contains ash, there is a need for technology to convert it into fluid energy through gasification, liquefaction, etc., and various processes are being proposed and developed.

In particular, conversion to methane-rich gas is an important technology as a substitute for natural gas. In this case, the gasifier type is:
It is roughly divided into fixed bed, fluidized bed, and spouted bed, and each type of coal is lumped coal (above the bed), pulverized coal (below the bed), and pulverized coal (below 0.1 m) is partially combusted using oxygen-containing gas. Among these, in the fixed bed, the temperature inside the furnace is uneven, and the temperature in the coal insertion part is particularly low, so there is a lot of tar by-product, and in the spouted bed, coal and gasification agent are supplied to the burner nozzle.
Since it is gasified at such high temperatures, it is suitable for producing CO and H2, but it hardly produces methane and is not suitable for obtaining high-calorie fuel gas. On the other hand, a fluidized bed has excellent heat transfer pressure within the bed, so it is easy to generate methane750
It is easy to maintain the temperature in the range of ~900C, and large capacity is also possible by operating under pressure.

In a fluidized bed gasifier with these characteristics, particles are kept in a bubble-diffused state by the gas flow inside the furnace, so small particles are easily scattered, so it is necessary to use particles that have been classified to an appropriate particle size. . In addition, the common dry method for supplying coal to a pressurized gasifier is a lock hopper type, but it requires a large amount of IJ, n-manual force for the hopper, and there are also problems with wear and tear during valve switching operations. Therefore, it is desirable to supply the material in the form of a slurry. It is cheapest to use water as a medium for slurrying, but since water absorbs the latent heat of evaporation inside the furnace, there is a risk of thermal loss. In order to reduce such heat loss, it is necessary to produce slurry 17-1 with a small amount of water, that is, a slurry with a coal concentration. but,
Higher coal concentrations make transport more difficult, especially in tanks and pipes, where they are more likely to become clogged by sedimentation of particles.

Generally, coal particle size is reduced to suppress sedimentation, but coal with small particle size easily scatters in a fluidized bed gasifier, and has the disadvantage that gasification efficiency cannot be increased. In addition, a method has been proposed to increase the viscosity of water by adding a water-soluble polymer to prevent sedimentation. When passing through, the pressure loss becomes large, which has the disadvantage of hindering stable supply.

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to obtain a coal/water slurry that contains a high concentration of coal with a particle size suitable for fluidized bed gasification, and that can be stably supplied without sedimentation. It is something.

[Episode 1''] ヮThe settling velocity U of the fluid-fluid solid is expressed by the following equation.

U, = g(ρ, -ρ)D-/18μ, where g: Gravitational acceleration (m/8”) ρP: Solid particle density (Kg/m”) ρ: Fluid density (Kf/m”) μ: Fluid Viscosity (Kf/m-8)+p, t:
1.2-1.4 b/cm” coal water (ρ: 1.9
In order to reduce the sedimentation velocity in 7cm"), it is sufficient to reduce ρ, -ρ, or to increase μ.

However, ρ and -ρ are the density differences between coal and water, and it is difficult to reduce them.Reducing D not only increases the crushing power, but also causes scattering when supplied to the fluidized bed gasifier. This makes it difficult to control the operation of the gasifier, which causes the essential problem of reduced gasification efficiency.

Therefore, we thought that it would be most practical to increase the viscosity μ of water.
- e.g. cellulose sodium glycolate (CMC)
was added to vary μ from lO to lO'cp, and the effect on coal sedimentation was investigated. As a result, as shown in FIG. .92m+
The sedimentation velocity of φ) decreases rapidly as shown in curve 2.

On the other hand, pulverized coal has a wide particle size distribution, but the filling rate of particles differs depending on the particle size distribution.

In general, particles with a relatively uniform particle size distribution have a large porosity, and the amount of slurry medium, i.e. water, required to fill the pores is large, making it difficult to obtain a slurry with a high coal concentration. be.

Therefore, it is necessary to appropriately mix coarse particles and fine particles to form a highly concentrated slurry (C4). However, since fine particles are easily scattered in the gasifier, it is important to reduce their amount as much as possible.

Therefore, in order to find a particle size distribution suitable for high concentration, we investigated the correlation between particle size distribution and bulk density. Particles scattered in the gasifier are determined by the gas flow rate under gasification conditions, the shape of the gasifier,
The scattered particle size cannot be determined uniquely because it varies depending on the tower diameter and height of the sky section, but for example, when the gas superficial velocity is 30 to 4
When gasifying at 0.06H/wJ, there was 0.0.
Since there are almost no particles smaller than 25 mg, it is thought that these fine particles are easily scattered. Coarse grains of coal larger than this are considered to be pulverized and scattered by abrasion due to gasification reactions and fluidization, but the residence time of these particles in the furnace is considerably longer than that of fine particles that are immediately scattered. For this reason, the bulk density was examined by changing the blending ratio of fine particles of 0.25 m or less and 0.42 mm or less and coarse particles of larger size (here, one fin at most).

As shown in FIG. 2, the bulk density of both curves 3 and 4 reaches its maximum at a coarse particle ratio of approximately 67% by weight, which can be said to be the particle size distribution that tends to have the highest concentration. In addition, in curve 3, fine particles are 0.
25+m or less, coarse particles are 0.25WI+1 to 1.0 gates,
In addition, curve 4 shows that fine particles are 0.42 mm or less, and coarse particles are 0.4 mm.
2wrm~1. It was blended as Off. Depending on the gas flow rate, particles of 0.25 mm or larger are also scattered, so we divided them at 0.42 m+ and investigated the blending ratio of larger (at 1 mi) and smaller particles, but the coarse particle ratio was still around 67% by weight. There is a maximum value of bulk density.

On the other hand, the viscosity of a slurry of coal and water increases as the coal concentration increases. Especially in water.

When a viscous agent is added, the sedimentation of the coal is suppressed, but the viscosity of the slurry is not high, which leads to an increase in pump power, and there is a restriction on increasing the concentration from the viewpoint of transportation. Therefore, from the standpoint of not lowering the viscosity of water from the standpoint of coal settling properties, and increasing the viscosity of the slurry from the standpoint of slurry transportability, we added a surfactant and investigated its effects. Figure 3 shows the particle size distribution of highly concentrated particles (0.25 to 1
．． A water slurry of coal containing 70% by weight of Otrys coarse particles and approximately 30% by weight of fine particles of 0.25 mm or less was prepared, and the effects of thickeners and surfactants on slurry viscosity were investigated. It is. Curve 5 is simply a mixture of water and coal, and the apparent viscosity at a coal concentration of 65% by weight is relatively low at 400 CP, but as soon as stirring of the slurry is stopped, it settles and the upper phase becomes only water. On the other hand, in curve 6 where 0.2% by weight of thickener was added to water, the coal concentration was 65%.
Although the viscosity is as high as 850 cp in terms of weight percent, a stable slurry with little sedimentation can be obtained. Furthermore, when 0.7% by weight of an anionic surfactant was added to the coal, the slurry viscosity at 65% by weight was approximately 600 cP, as shown in curve 7, and the particles were smaller than when a thickener was added. Sedimentation became more difficult to occur and a stable slurry was obtained. Further, even if the coal concentration is increased to 70% by weight, it can be stirred uniformly, and a much more stable slurry can be obtained than when simply mixed with water.

[Embodiment of the Invention] - An embodiment of the present invention will be described below with reference to FIG. FIG. 4 shows the flow of the preparation and transportation system for the larvae. The coal 11 is processed by a coarse pulverizer 101 and a fine pulverizer 102 to be suitable for fluidized bed gasification and to have a particle size suitable for high concentration, for example 0.2.
5~1.0 m' 67% by weight, 0, 25w or less 33% by weight, and each line 12
−． Step 14: Pour the coal slurry into the coal slurry preparation tank 202. , while water 20 as a slurry medium is stored in a medium preparation tank 20.
In Step 1, add 0.2 to 1.0% by weight of thickener 21 (based on water) and 0.5 to 2.1% by weight of surfactant 22 (based on coal), mix uniformly, and use a medium transport pump. At 24, the slurry is sent to the slurry preparation tank 202. In the slurry preparation tank 202, the ratio of coal 15 and medium liquid 25 is 60/40 to 70/30.
mixed so that

Note that water-soluble polymer compounds such as poly(ethylene oxide), poly(acrylamide), guar rubber, etc. can be used as the thickener. As the surfactant, anionic surfactants such as sodium alkylbenzenesulfonate and cationic surfactants such as alkyltrimethylammonium halide can be used.

The thus prepared coal/water slurry is sucked in by a slurry pump 31 through a line 30 and transported through a line 32 to the fluidized bed gasifier side.

In the above, when the medium liquid is ■ only, ■ when a thickener is added to water: ■ when a thickener and a surfactant are added to water, ■ when a surfactant is added to water, respectively. The table below shows the results of a comparison of the transport performance of the slurry pump 31.

Here, the transport rate of the water slurry was 30 t/h, and the inner diameter of the pipe on the discharge side line of the slurry pump 31 was 6 cages φ.

When no water pressure was added, the concentration of coal per coal reached a limit of 54% by weight, and if more coal was added, the conduit became noticeably clogged due to sedimentation of particles, and transport became impossible in a short period of time. On the other hand, when a thickener is added, the amount of thickener is 0.2
, '0.5 and 0.9% by weight, the coal concentration was 57% by weight and 60% by weight, respectively.

It was possible to transport slurry up to 60% by weight. moreover,
When the amount of thickener was 0.5 weight and 19 g, and 0.7% by weight of surfactant was added to coal, it was possible to transport up to 65% by weight. The transport limit when only the surfactant was added to water was 61% by weight.

The transport performance of slurry also changes depending on the characteristics of the pump, so the above value of the transport limit concentration is not absolute. It is clear from the above practical example that it is possible to transport.

In addition, when slurry is made using only coal with a particle size range of 0.25 to 1.0, the transport limit is 6.0% by weight of coal even if a thickener and surfactant are used together. and 0
．． By containing 33% by weight of fine powder of 25m+ or less, slurry with a high coal concentration can be transported.

〔Effect of the invention〕

According to the present invention, a stable high-concentration coal/water slurry can be obtained without sedimentation, and even when supplied to a fluidized bed gasifier, for example, the water will cause a drop in the furnace temperature and the gasification will cause particles to scatter. Phenomena unfavorable to the reaction can be greatly reduced.

[Brief explanation of the drawings] Figure 1 shows the relationship between the amount of thickener added, the viscosity of water, and the sedimentation rate of coal particles, and Figure 2 shows the relationship between the blending ratio of coarse particles and fine coal particles and their bulk density. FIG. 3 is a diagram showing the influence of the medium on slurry viscosity, and FIG. 4 is a system diagram explaining one embodiment of the present invention. 101...Coal coarse pulverizer, 102...Coal fine pulverizer, 201...Slurry medium preparation tank, 202...
...Slurry preparation tank, ' 24,,, medium transport pump, No. 1 port 1 @ viscous quantity (1〃) No. 20

Claims (1)

[Claims] 1. The particle size of coal is adjusted, and water, a thickener, and a surfactant are added and mixed to the coal whose particle size has been adjusted, and the /i feature is obtained. Method for producing coal/water slurry. 2. 60-75% by weight of coarse coal, 25-4% of fine coal
The method for producing a coal/water slurry according to claim 1, wherein the slurry is adjusted to 0% by weight.