JPS61261395A - Method and apparatus for producing coal/water fuel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for producing coal-water fuel (CWF) on a commercial scale by a unique application of conventional commercial equipment.

BACKGROUND OF THE INVENTION The individual unit operations in the present invention include coal crushing, rod milling (grinding using iron rods), arc sieve sorting, froth flotation (foam end flotation), waste dewatering, and ball milling. be. These operations have been practiced for many years in coal preparation and beneficiation operations. The present invention also uses a reverse flotation operation.

Grinding unit operations such as crushing, red milling, ball milling, etc. are commonly used in ore processing plants, such as steel and molybdenum ore concentration operations. However, lid mill and ball milling operations are not used in conventional coal beneficiation operations. This is because current technology states that the production of pulverized coal should be avoided, primarily because of the inefficiency of conventional pulverized coal cleaning operations.

In conventional coal froth flotation operations, chemicals are added to the mixture of ground coal and water to selectively attach air bubbles to the coal particles and cause them to float. The mineral particles remain at the bottom of the flotation tank. In the case of reverse flotation, different agents are used to sediment the coal particles and selectively attach air bubbles to the liberated pyrite particles. Thus, pyrite (the primary sulfur-containing mineral associated with coal) rises to the surface and can be skimmed off, reducing the sulfur content in the feed stream.

Froth flotation is a commercially well-established technique for reducing the ash content of feed coal, but in most conventional coal flotation operations only 10-20% of the total feed to the plant is
only those that are passed through the flotation circuit.

In contrast, in the present invention, depending on the properties of the coal, the entire feed stream can be passed through the treasure flotation circuit. In order to increase the efficiency of the flotation circuit, it has been found to be advantageous to separate the feed to be flotated into a coarse grain stream and a fine grain stream (separate feeding).

Separately fed flotation is practiced in some commercial operations, but is not common. Separate flotation of coarse-grained coal was first carried out around 1960 at the Hunch Coal Company's pipeline plant in Ohio, USA. Kerr Matsugee Company also has a state-of-the-art coal preparation plant (capacity 1200 tons per hour).
Separate feed flotation equipment has been installed to process 28 mesh x 0 coking coal. Multi-stage flotation i.e.
Multi-stage flotation with rough selection and selection has been practiced in the coal industry for more than 20 years. The first coarse-finishing circuit in the US coal industry was designed in 1963 and installed at three Bethlehem Mines Corporation plants in Pennsylvania, USA. This flotation circuit is 2 days old.

It was designed to process 60 grains of coal per hour.

Reverse flotation has been used at both the experimental and pilot plant levels for several types of Pennsylvanian and West Virginia coal (coal feed [12t/
) and the results of these tests showed that 70% of the pyrite sulfur
It has been found that % to 90% can be removed by reverse flotation.

Much of the early research, which began in the late 1960s, was supported by the US Bureau of Mines. Technical details of this method are described in the literature. Some companies still continue this research as private research programs.

The use of vacuum disc filters for fine particle dewatering is a common technique in both coal and mineral beneficiation plants.

However, the present invention requires more sophisticated control in existing coal washing plants. however,
Such sophisticated control is standard operation in iron ore concentrators where the wet foot of the filter cake is a determining parameter for the subsequent granulation process.

The final stage of the CWF production process of the present invention, a high-density ball milling operation, was experimented at the pilot plant level. Capacity 5 installed at Kennedy Pan Thorne Corporation in Danville, Pennsylvania, USA
A 0-100 t/day pilot plant has been in operation since 1982. Coal-water fuel (CWF) technology is
U.S. Pat. No. 4,282. OO6 and 4.441
．． It is described in No. 887, etc.

SUMMARY OF THE INVENTION The present invention uniquely combines several unit operations, which are individually known, to produce coal on a commercial scale.
A method and apparatus for producing water fuel (CWF) is provided. As previously mentioned, the individual unit operations used in the present invention include coal crushing, four-sided milling, arc sieve sorting, glass flotation, vacuum filtration, waste dewatering, ball milling, reverse flotation, etc. be. These operations involve producing fine particles by grinding coal in stages in p-Radomill and ball mill circuits, a technique not used in the conventional coal industry. Furthermore, the froth flotation circuit used in the present invention does not have to be complicated as seen in the conventional coal industry. Ru.

By incorporating a coal beneficiation circuit into the process of the present invention, it is possible to reduce the ash and sulfur content of raw coal.

This capability expands the range of sources that can be accepted as coal feedstock, making it possible to offer a variety of fuel qualities tailored to specific customer requirements. Also,
The method of the present invention can extend the generally established limits of conventional coal beneficiation operations. This is because the fine grinding required for CWF production results in the liberation of undesirable minerals and pyrite sulfur from the coking coal. Production of CWF also eliminates the need for thermal drying of pulverized coal, thus avoiding the subsequent handling and storage problems associated with dry pulverized coal.

It is therefore an object of the present invention to provide a crushing and primary grinding stage to liberate undesirable constituents of the coal, a conventional froth flotation stage to remove pyrite, and a dewatering stage to concentrate the solids. It is an object of the present invention to provide a coal-water fuel production method and apparatus comprising a slurry preparation step for controlling particle size distribution, and a waste dewatering and water purification step.

Although the individual functional circuitry remains unchanged in various embodiments of the invention, individual parts and elements of the device may be replaced. Therefore, in an actual operating plant, parallel equipment can be installed so that individual units can be bypassed in case of equipment failure or when switching to produce different types of products. It will constitute purcess piping.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows an embodiment of the CWF production apparatus and method of the present invention for producing coal-water fuel (CWF). This equipment consists of six functional circuits, namely a raw coal crushing and primary crushing circuit 2, a 7!2 foam flotation circuit 4 for reducing the ash and sulfur content of pyrite, and a predetermined solid content a product dewatering circuit 6 for determining the rate and a slurry preparation circuit 8 for establishing the desired particle size distribution in the fuel;
and a waste dewatering and water purification circuit 10 for treating waste from one or more of the other functional circuits and purifying water from those circuits. FIG. 2 shows a crushing circuit. 22, a froth flotation circuit 24, a reverse flotation circuit 26, a dewatering circuit 28, a slurry M production circuit 30, and a waste treatment circuit 32.

In the following, the individual functional circuits of the invention will be explained with reference to FIGS. 1 and 2.

Coking coal delivered to the crushing and primary crushing plant is sample inspected,
If necessary, they are stored in separate piles (not shown). The coal is extracted from the pile into one of several coking coal storage bins 202 (only one is shown in Figure 2).
transferred to one. Coal can be blended to meet specific feed requirements by individual feeders in each bin prior to processing.

Initial comminution of coking coal with a nominal particle size of 3″ to 5″
This is done using a mold crusher 104 or 204. Several types of impact crushers are commercially available; for example, a hammer mill or a Nazi mill type crusher would be a preferred choice. The crusher 104 or 204 is sized and operated to produce a subgranular product for further processing. An overall reduction or grinding ratio of approximately 6:1 is required. In order to achieve this reduction ratio, it may be necessary to arrange multiple stages of crushers. (Second
The illustrated crusher 204 is a double roll crusher. ) The maximum particle size of the crushed coal can be adjusted to suit specific processing requirements.

In FIG. 1, a crusher 104, such as a roll crusher, is shown.
The crushed coal flows down by gravity to the primary wet grinding operation section 106 (for example, a ball mill). This wet milling operation serves several important functions. That is, (l
) Provides a uniform coal particle size distribution for subsequent processing steps, regardless of the particle size distribution of the coking coal. (2) Provide a highly active, freshly milled coal surface site for subsequent froth flotation operations. (3) Preventing surface oxidation of newly generated active coal sites. (4) Acts as an efficient wet mixing and conditioning device.

Suitable equipment for this knitting operation is a conventional wet ball mill 106 (Fig. 1), 206 (Fig. 2) or a rod mill. Both ball mills and rod mills produce grain size 2B mesh × from a feed of grain size Ll × 0.
0 products can be produced. This corresponds to a reduction ratio of 33:1. Both mills are operated at approximately 50% solids content. The operating conditions of the mill and the particle size distribution of the product are determined by the properties of the coal being treated.

Here, two different milling circuit designs were devised. 1
One is shown in FIG. 2 and is a conventional closed circuit wet ball mill process. In this mode of operation, the mill product (coal ground by the mill) is transferred to a hydrocyclone classifier. , is pumped. (Cyclone separation is based on particle mass.) Cyclone 2 contains oversized coal and fine pyrite particles.
The underflow from 08 is passed through an arcuate sieve 210. The sieve top of the arc sieve is mill 2 for re-grinding.
06 and the pyrite-rich undersieve is sent to the waste concentrator 284 of the waste treatment circuit 32. The overflow of cyclone 208 is sent to froth flotation circuit 24. This type of M crushing circuit is particularly suitable for processing coal containing relatively large amounts of coarse pyrite.

Another milling circuit selected was an open circuit rod mill process cell (not shown).

This rod milling method provides a relatively narrow particle size distribution,
In other words, it is possible to reduce the generation of ultrafine particles, but the particle size is 2.
A product (crushed coal) of 8 mesh or less can be produced. Reducing the amount of ultrafine particles will enhance the performance of subsequent froth flotation circuits.

The product from the milling or crushing circuit 22 with a particle size of 28 mesh or less may be sent to a beneficiation circuit (i.e., a four-stage flotation circuit 24 and a reverse flotation circuit 26) or to a sterry preparation circuit 50. The feed may be sent to a vacuum filtration device 229 for dehydration in a dehydration circuit 28. The latter option may be used if the coal is of sufficient quality to meet the customer's requirements without further ash or sulfur removal, or if pre-washed coal is used as feed to this purcess. Can be used if selected.

Conventional froth flotation The performance of the flotation process, like all beneficiation processes, depends to some extent on the particle size distribution of the feed.

Flotation kinetics and optimal cell operating conditions depend on particle size (
particle size).

Therefore, precise control of particle size is required to improve selectivity and therefore ash removal and coal recovery. The feed (crushed coal) to be subjected to flotation can be separated into a coarse particle fraction and a fine particle fraction, depending on the characteristics of the coal to be treated. Making this selection requires measuring the particle size distribution of the feed to predict the mass flow rate to each circuit and analyzing the flotation behavior of each particle fraction. In this regard, the attrition mill can be controlled to adjust the particle size distribution of the product.

Referring to FIG. 2, the product of the grinding or crushing circuit may be classified using a two-stage arc sieve 212. If the attrition mill is adjusted to consistently produce product with a particle size of 28 mesh or less, the first stage arc sieve divides the feed stream into a stream of particles with a particle size of 28 x 48 mesh (or 28 x 65 mesh). 214 and particle flow 2 of less than 4 days mesh (or less than 65 mesh)
It is designed to be separated into 16 parts. The actual particle size breakpoint is determined by the characteristics of the coal being treated. If the sorting accuracy is not sufficient, some fine particles will be carried along with the arc sieve.

Such sieves can be passed through a second stage of arcuate sieves, also designed to capture particles of 48 mesh or 65 mesh or more, to increase the removal rate of fine particles. This second stage arc-shaped sieve needs to be sprayed with water spray to increase the sorting efficiency.

The coarse and fine particle fractions are collected in separate reservoirs and pumped into respective multi-stage flotation circuits.

The multi-stage flotation operation also includes the step of reprocessing the cross product (product captured and floated by the seven basins) to further remove ash and sulfur content therefrom. Usually at least one flotation stage 218.219.220.221.2
22 or 223 required. The actual number of stages required is
It is determined by the measured quality of the froth product and the characteristics of the coal being treated. Generally, each sequence of flotation stages is operated to produce progressively higher quality products. Physically, the stages are sequentially arranged at different heights so that the floss product from each stage can be fed by gravity to the next stage. It is not contemplated to recycle high ash and sulfur waste (waste) and such waste is sent from each stage 218-223 to the waste dewatering and water purification circuit 32 as indicated by the dotted lines. .

Each stage consists of one or more individual flotation cells (compartments). The floss product from each cell can be collected separately so that the quality of the floss product can be closely monitored and controlled. If necessary,
The floss (foam) can also be sprayed with water to remove middling particles loosely held by the floss.

Flotation promoters (foam-forming chemicals or foaming agents) can be added directly to the flotation cell or to a conditioning tank upstream of the flotation cell. An alcohol or glycol foaming agent such as methyl amyl alcohol (or methyl isobutyl carbinol) is used to produce a stable selective froth. If necessary, fuel oil (M2 or A6) or other flotation enhancer is added to increase coal recovery. The chemicals actually required must be selected according to the type of coal to be treated, and their suitability must be confirmed through experiments for each application.

Separation of the product from the crushing circuit into coarse and fine particle streams may or may not be necessary depending on the characteristics of the coal being treated. Since most of the water in the coarse particle fraction has passed through the arc sieve together with the fine particles, it has a high solids content and is therefore not suitable for effective flotation. , the plant recirculated water (second (indicated by the dashed-dotted line in the figure) is supplied to the coarse coal pool. In order to increase the selectivity of the floss, the first two coarse flotation
In No. 8, the amount of foaming agent is reduced (foaming agent α1 to o, 5xb per 1 coal), and the amount of air blown is also relatively small (
Air blowing amount α05~α20ft3 per cell capacity @1ft'l
). The froth product (suspended coal particles attached to the froth) from these cells may or may not need to be processed in the purification flotation stage 219. Furthermore, chemicals (foaming agents) can also be added to the residue in the coarse flotation tank in order to suspend as many useful particles as possible. Those froth products can also be sent to a purification flotation stage 219. Coarse flotation unit 219
The quality of the floss product from the last cell is generally inferior to the product from the previous cells. This lower grade scrap product can be passed through an arc sieve (not shown), the top of the sieve can be returned to the crushing circuit 22 for re-grinding, and the bottom of the sieve can be sent to the scrap dewatering circuit 32.

The suitable froth product from the coarse flotation stage 218 may be fed to a coarse coal purification stage 219. Water is added to the froth product feed trough from coarsening unit 218 to dilute the feed to purification stage 219 (fross product) to a solids content of approximately 10 M% solids. The purpose of the purification stage 219 is to produce a final coal product that is clean in terms of low ash and sulfur content, and high in carbon. Did you have a high sulfur removal rate? b NiCa O, KMn Oa 'Etaha ni 2
A pyrite sedimentation agent such as Cr207 can be added to the flotation cell of the purification stage 219. 7 from purification stage 219
The filter product flows to vacuum filter feed sump 228 . As in roughing stage 218 , the 70% product from the final cell of purification stage 219 may also have to be screened and returned to grinding mill 206 . Purification stage 2
The waste from 19 is sent to waste dewatering circuit 32.

The underflow obtained by the particle size classification of the product of the crushing circuit (typically particle size 48 mesh x 0 or 65 mesh Sent. The solid content of the feed to the coarse particle coal separation unit 221 is lower than the solid content of the feed to the coarse particle coal separation unit 218, and is about 5 to 7%. This is because most of the water in the product (50% solids) from the crushing circuit passes through the arc sieve 212 along with the particulate carbon.

However, it is not practical to install a dewatering device at this stage of the process, so the rough separation unit 2 for fine coal
21 must treat this large amount of water. This diluted feed (ie, the water-rich particulate coal fraction from the crushing circuit) is advantageous in terms of flotation efficiency, but increases the required size and number of flotation cells.

If necessary, the froth product from all cells of the fine coal coarsening unit 221 is purified in a purification stage 222;
Then repurification stage 223 with a solids content of about 10% by weight.
to remove as much ash and sulfur as possible.

The actual number of flotation stages required will depend on the characteristics of the coal being treated. The removal of sulfur content at this stage is from 48 mesh to
150 metsushi (“metshu” is written as rMJ)
limited to particle sizes in the range of . The waste from each flotation stage is
Both are sent to the waste treatment circuit 32 for dewatering and water purification.

Multi-stage flotation operations of granulated coal produce carbon-rich coal particles that are clean in terms of low ash and sulfur content across all particle sizes. The final FPS product exiting the repurification stage 223 has some particle size of 100M (100M).
In some cases, the product may contain a pyrite sulfur content of less than or equal to pyrite flotation circuit (reverse flotation circuit) 26 for pulverized coal.

Pyrite Flotation (Reverse Flotation) The reverse flotation circuit 26 is operated to remove pyrite sulfur in the granulated coal fraction and maximize coal recovery (coal fraction). Reverse flotation cannot be applied to remove ash.

Also, reverse flotation is not efficient for separating pyrite with a grain size of 100M or more. Therefore, before the reverse flotation circuit 26,
A conventional flotation circuit 24 must precede it.

The process of the present invention utilizes two stages to reduce the sulfur content of the granulated coal captured by the froth in circuit 24.
26,227) using reverse flotation.

The froth product from the froth flotation circuit 24 (solids content 20-25 i% by weight) must condition the particle 1 surface to sediment the coal and float the pyrite. To this end, approximately 0.4 to 0.71 b of coal sedimentation agent per 1 coal and approximately Q, 4 to α71 b of pyrite flotation agent (indicated by dotted lines in FIG. 2) per 1 coal are added to the adjustment tank 224. do. The type and amount of chemicals actually used are determined depending on the characteristics of the coal to be treated. Furthermore, tank 22
The contents of 4 must be reduced to an H value of 4.

This acidic property helps remove certain groups of compounds from the surface of pyrite particles and increases the hydrophobicity of pyrite. Additionally, the slurry prepared in tank 224 may need to be diluted to 15-20% solids content before it is fed to feed channel flotation unit 226.

Past experience has shown that the feeder flotation stage 226 produces a high sulfur content 7 spoiled product and a correspondingly low sulfur content clean tilling product. Tilling (i.e., sediment, also referred to as "tail") from this feeding channel flotation stage 226
is sent to the clean coal dehydration circuit 28. The froth product (pyrite) from the last 2.3 cells of the food flotation unit 226 may contain a significant amount of carbon, which is recovered by the food flotation unit 226. The froth product from 226 is reprocessed in a purification reverse flotation stage 22.7.

The high sulfur froth product from the purifying reverse flotation stage 227 is
Additionally, it can be passed through arc sieves (not shown) to remove coarse coal and pyrite containing significant amounts of carbon. The sieve top of the arc sieve can be returned to the crushing circuit 22 and re-pulverized to liberate pyrite particles. On the other hand, below the arc sieve is a waste disposal and water treatment circuit 32.
Dehydration and water purification are carried out.

The tilling from the purification inverse flotation unit can also be viewed as a coal middling product, which is transferred to the feed channel flotation stage 226.
can be returned to. Alternatively, the product may be returned to the crushing circuit 22 for re-grinding.

Clean Coal Dewatering 1 The clean coal dewatering circuit 28 must be designed to provide a precisely controlled high solids feed to the slurry preparation circuit 32. The feed with a solids content of about 25% to be sent to the vacuum disc filter 229 is -
It must be dehydrated to a solids content of about 75-78%. This feed consists of the froth product of conventional coal flotation and the tilling product of reverse flotation.

If the beneficiation circuits 24 , 26 were to be bypassed, the product from the crushing circuit 22 would be sent directly to the filter feed sump 228 .

The filter feed reservoir 22, 8 serves as a storage and mixing tank for the feed to the filter.

Experiments have shown that the froth product from flotation circuit 24 is fairly easily broken up by gentle agitation. Providing a consistent feed of maximum solids content to the filter helps to increase the efficiency of the filter.

To maintain optimal filter efficiency, the vacuum suction of the filter must be maintained at a consistently high level. A two-stage vacuum pump is required to maintain a constant vacuum suction force for pulverized coal with different porosity. Another means of maintaining high vacuum is to keep the filter tank full of feed.

The rotational speed of the disc-shaped filter, and thus the rate of production of the filter cake, is controlled to correspond to the output of clean coal per unit time from the steam flotation circuit 24,26. However, the product from the flotation circuit is pumped to the filter 229 at a rate higher than the throughput rate of the filter 229 to ensure that the overflow from the filter tank is constantly returned to the filter feed sump 228. so that This over 7p- serves to maintain a constant feed level (liquid level) in the filter tank of the filter 229. It is preferred to use a snap plow device to obtain good filter cake discharge.

The importance of the dehydration circuit 28 for coal-water fuel production cannot be overemphasized. The solids content of the dehydrated product is determined by the subsequent slurry preparation circuit 30.
should be kept as high as possible to give some flexibility.

Coal-Water Slurry Preparation The slurry preparation circuit 30 consists of a second grinding unit 23 to obtain the best particle size distribution. The slurry is produced by two sets of high shear mixing tanks 232 arranged in series.
controlled by The first set of mixing tanks is for controlling the viscosity of the slurry, and the second set of mixing tanks is for controlling the stability of the slurry. Slurry preparation circuit 30, as with flotation circuits 24, 26, includes the necessary drug delivery, storage and metering equipment (not shown).
It is equipped with

The clean coal particles recovered as a dewatered filter cake from the vacuum disc filter 229 fall directly onto the belt conveyor through a plastic lined chute. The metering scale on the conveyor belt is used to provide accurate measurements of the feed rate of coal particles to the second grinding ball mill 230. The filter cake or coal particles fall into the screw feeder for the ball mill 230. Into the feeder are added a dispersant (drug), a pHge agent, and the required dilution water (indicated by dotted lines in Figure 2). The second, regrinding ball mill 230 is operated at high solids conditions (70-78 wt.% solids).

Stable control of the product particle size distribution is achieved by controlling the viscosity of the ground coal/water slurry through the addition of dispersants. The operating conditions of the regrinding ball mill, such as the distribution of ball sizes used in the ball mill, the ball charge, and the rotational speed of the mill, are selected to maximize the raw mill speed and minimize power consumption. . Ball mills are also extremely efficient mixers, so there is no need for a separate mixer.

For some types of coal, high solids ball mills
It may not be possible to efficiently produce sufficient fine particles to maintain proper rheological and stability properties of the slurry. To correct this situation, a portion of the filter cake (coal particles) from the vacuum filter can be sent to a ball mill with an agitator (not shown) rather than to the high solids ball mill 250. In that case, the feed to the ball mill with stirrer (
Sufficient water is added to dilute the filter cake to a solids content of 50-60%.

The product from this agitated ball mill or micronizer is added to the feed to high solids ball mill 230 to obtain the required amount of fine particles.

It should be noted that the solids content of the slurry within the ball mill 230 must be maintained at a high level, ie, above 70%. If the amount of product from the agitator-equipped ball mill is so large as to significantly reduce the solids content of the entire slurry in the high-solids ball mill 230, the product may not be supplied directly to the ball mill 250 but may be returned to the filter 229. The semi-finished coal/water slurry from ball mill 230 may require 1
It has a viscosity of 500-4000 centipoise and 70-7
It has a solids content of 5%.

This slurry is pumped to a viscosity treatment mixing tank (not shown) equipped with a low speed, high efficiency impeller type mixer into which the dispersant is added.

The viscosity of the slurry is reduced to about 500-2000 centipoise.

The products from this viscosity treatment mixing tank are:
(particles larger than 48 M) are pumped to a high frequency vibrating screen 231 to remove particles. The amount of oversized particles is
It is usually less than 3% by weight and is recycled to the ball mill 230 for further grinding. This vibrating screen 231 is an external classifier that constitutes a closed crushing circuit for controlling maximum particle size.

The underflow of the vibrating screen 231 flows down by gravity to a stabilizer treatment mixing tank 232 in which the final slurry is prepared. Stabilizers and P HatJi powder caustic agents can be added to the mixing tank 232 to inhibit settling of particles to obtain a final product of predetermined quality. All of the chemicals used for slurry preparation are commercially available, pose no pollution problem, and can be easily obtained from existing drug suppliers.

The final coal-water fuel (CWF) product, indicated at 240, is pumped from the stabilizer treatment mixing tank 232 to a storage tank. These storage tanks are insulated and equipped with mixers to maintain product homogeneity. This product can be transported from the storage tank by tanker truck, freight car, or ship ◎ Waste dewatering and water purification The waste dewatering and water purification circuit 32 disposes of the waste from this plant in an environmentally acceptable manner. It is intended to provide clean process water for preparation and reuse in the plant. Contamination of the recirculated water has a negative impact on product quality, so the recirculated water must be purified in order for the system or plant to operate properly.

All process waste, including tilling from the conventional froth flotation circuit 24, froth from the coarse particle reverse flotation unit 26, and P fluid from the vacuum disc filter 229,
It flows down by gravity to a stationary waste concentrator 284. The concentrator 284 establishes a static environment in which particles settle and
Leaves a purified water layer. This concentrator overflow or purified water is returned to the plant water (process water) supply and recycled to the plant. Fresh makeup water must also be added to this water supply.

Concentrator underflow (solids content approximately 25-30% by weight)
For further dewatering, belt molding filter press 28
A 0-belt filter press pumped to 6 was chosen because it can handle ultrafine particles and clay slime. The p liquid from the conofilter press is returned to the concentrator 284. The dewatered waste filter cake (solid content 60-80% by weight) is conveyed by a belt conveyor to an external storage site and used for landfilling or the like.

In order to avoid interrupting the operation of the entire CWF production plant even if a failure occurs in any part of the waste dewatering and water purification circuit 52, several reservoirs are constructed within the plant area. Provide for storage of excess plant water, continuous or intermittent supply of make-up water, and storage of effluent from the aeration concentrate machine 284 during scheduled or unscheduled interruptions in plant operations. is preferred.

The puta cess of the present invention is advantageous in terms of slurry generation.

It also offers numerous advantages in terms of coal beneficiation. These advantages are broadly divided into those due to modular design that allows individual unit operation and those due to operational flexibility.

The invention was developed from the idea of separate unit operations to accomplish specific functions such as ash and sulfur release, ash removal, sulfur removal, dewatering, slurry preparation, etc. To this end, we have provided a device with a modular structure that enables the following:

- implementation of individual unit operations in the best possible manner; - sample testing of the product between each module (equipment unit) to pinpoint the cause of operational problems; - capacity reduction of the plant; Adding parallel units to increase and - replacement with newly developed, advanced unit operations (particularly coal beneficiation).

The present invention contemplates a high degree of operational flexibility to accommodate variations in coking coal quality and changing customer specifications for the final product.

Some examples of flexibility are as follows.

- Controlling the particle size distribution of raw coal to the initial crushing operation unit according to variations in coal crushing parameters; - Feed to the beneficiation process according to the degree of grinding required to liberate ash and pyrite. control the particle size distribution of the coking coal; and if the quality of the coking coal satisfies the customer's specifications, the beneficiation process can be completely bypassed (thus, the waste filter can also be shut down).
, - the ability to integrate the separate feeds by particle size into a single feed to the froth flotation unit; - the ability to bypass the sulfur removal step of the beneficiation circuit if the coking coal has low ash and sulfur content; The CWF production method of the present invention is unique in that it is specifically directed to the problem of sulfur removal from particulate pyrite.

The suitability of the invention was demonstrated by experiments conducted with several types of coal. These coal samples were first crushed in an experimental patch two-fourth mill, beneficent by multi-stage froth flotation in an experimental flotation machine, dewatered by a vacuum filter, and then processed in an experimental batch ball mill. Shattered.

Here we present representative test results for two types of coal: the Aberfreeboard coal seam and the Pittsburgh coal seam.□
Each operation will be explained step by step below.

Rod Milling The degree of milling required to liberate foreign materials such as ore and pyrite-sulfur from raw coal depends on the nature and distribution of those foreign materials. The foreign substances in the coal of the Pittsburgh coal seam are more finely distributed than the foreign substances in the coal of the Abba-7 Riebau F coal seam. Therefore, the coal of the Pittsburgh coal seam is
Finer grinding is required to achieve the desired foreign material release. However, the degree of grinding allowed at this stage is
Limited by the required particle size distribution of the final coal/water fuel.

The particle size distribution of the feed to the flotation process, obtained by a glue radmill in the laboratory, is shown in the graphs of FIGS. 3 and 4.

2-21j132 This experimental flotation circuit included multi-stage flotation and reverse flotation. As shown in Table 1 below, the removal of ash and sulfur content of the feed is well achieved and the combustibles (BTU
A high recovery rate of 100% was achieved.

Table 1 Performance of froth flotation circuit Ash content (%) in feed 6.08
9.17 Sulfur content (%) in feed t32
Ash content (%) in t74 product 545
5.16 Sulfur content (%) in product t
07 α76BTU recovery rate (%)
The floss product from the above flotation step was dewatered using a laboratory leaf filter. These tests have shown that the product of the particulate flotation process yields a dewatered filter cake (coal particles) with a solids content of 68-77%.

Preparation of CWF The product dehydrated in the above step is 1. Stable coal/
It was mixed with drug to prepare a water slurry and ground in a laboratory batch ball mill.

The properties of the slurries obtained were as shown in the table below: Solid content (%) 7α6 7S, 4 The particle size distribution of these slurries is shown in the graphs of FIGS. 5 and 6.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an apparatus of the present invention for carrying out the method of the present invention, FIG. 2 is a schematic explanatory diagram of another embodiment of the present invention, and FIG. 3 is a block diagram showing an apparatus for carrying out the method of the present invention. FIG. 4 is a graph showing the particle size distribution of the flotation feed obtained by grinding coal from Pittsburgh with a rod mill. FIG. The figure shows the particle size distribution of the final CWF obtained from Aba-7 Leeboat coal.
7, Figure 6 shows the final C obtained from Pittsburgh coal.
It is a graph showing particle size distribution of WF. 2: Crushing and primary crushing circuit 4 Near flotation circuit 6: Product dehydration circuit 8 Nis slurry preparation circuit 10: Product dehydration and water purification circuit 22: Crushing circuit 24: Fus flotation circuit 26: Reverse flotation Selection circuit 2nd day: Dehydration circuit 30 Nislery preparation circuit 32: Waste processing circuit WF FIG, 3 FIG, 4 Warehouse tnk (Mi7a) Taste;

Claims (1)

[Scope of Claims] 1) A method for producing coal/water fuel from coking coal, comprising: a crushing step of crushing the coking coal to produce granular coal from which ash and pyrite have been liberated; and adding water to the granular coal. and a froth flotation step of removing ash and coarse pyrite sulfur from the granular coal by froth flotation by adding a chemical and producing an ash-reduced and sulfur-reduced coal; and adding water and a chemical to the ash-reduced coal. a reverse flotation step in which pyrite is removed from the ash-reduced coal by reverse flotation to produce ash- and pyrite-reduced coal; and dehydration in which the ash- and sulfur-reduced coal is dehydrated to produce dehydrated granular coal. and a slurry preparation step for preparing a slurry having a predetermined particle size distribution from the dehydrated granular coal and usable as a coal/water fuel. 2) The method for producing coal/water fuel according to claim 1, wherein the crushing step comprises an initial crushing step followed by a main crushing step. 3) In the crushing step, the particle size is reduced to 3/4 in the initial crushing stage.
(2) Coal/water fuel production according to claim 2, characterized in that granular coal of ×0 is produced, and the granular coal is crushed in the main crushing stage to produce granular coal of particle size 28M × 0. Method. 4) the main crushing step uses a closed-circuit wet ball milling operation to produce the granular coal, classifies the granular coal using a hydrocyclone, and directs the hydrocyclone overflow to the froth flotation step; If necessary, the underflow of the hydrocyclone is passed through an arcuate sieve depending on the characteristics of the coal to generate an upper sieve and an under sieve,
4. The method of producing coal/water fuel according to claim 3, further comprising returning the upper part of the sieve to the wet ball milling operation and feeding the lower part of the sieve to a waste concentrator. 5) The method of producing coal-water fuel according to claim 3, characterized in that the main crushing step consists of producing the granular coal with a particle size of 28M x 0 using an open-circuit rod mill operation. . 6) A patent claim characterized in that low ash and low pyrite coal is used as the raw material coal, and the granular coal with a particle size of 28M x 0 produced in the main crushing stage is directly fed to the dehydration step. Coal/water fuel production method described in Scope 3. 7) The froth flotation process is carried out in one stage or in multiple stages including an initial coarse flotation stage, a second purification flotation stage and a final repurification flotation stage, depending on the type of coal. A coal/water fuel production method according to claim 1, characterized in that: 8) The froth flotation process uses two parallel froth flotation circuits each consisting of one stage or multiple stages including a coarse flotation stage, a purification flotation stage, and a repurification flotation stage. The granular coal from the crushing process is passed through an arc sieve before being sent to the froth flotation process, the sieve top of the arc sieve is fed to one of the froth flotation circuits, and the 8. A method for producing coal/water fuel according to claim 7, characterized in that the bottom of the sieve is fed to the other froth flotation circuit. 9) The method for producing coal/water fuel according to claim 1, wherein the dehydration step is carried out using a clean coal tank and a vacuum disc type filter following the tank. 10) The slurry preparation step includes a high solids regrinding ball mill for crushing the dewatered coal, a vibrating screen for controlling maximum particle size, and receiving the product from the regrinding ball mill. 10. The coal/water fuel production method according to claim 9, wherein the method is carried out using at least one stage of mixer for preparing the slurry. 11) The waste generated in the froth flotation and reverse flotation processes and the dehydration process is collected in a concentrator, separated into recirculation water and concentrated waste, and the concentrated waste can be pressed and disposed of. 2. The coal/water fuel production method according to claim 1, further comprising the step of treating the recirculation water as state waste to make it usable plant water. 12) A coal/water fuel production device for producing coal/water fuel from coking coal, comprising: a crusher for receiving and crushing coking coal; a main pulverizer for receiving and further pulverizing raw coal; and a main pulverizer connected to the main pulverizer, receiving the pulverized raw material coal from the main pulverizer and subjecting it to froth flotation to produce reduced ash coal. a froth flotation means coupled to said froth flotation means for receiving said ash-reduced coal and reverse flotating it to produce ash-reduced and pyrite-reduced coal; a dewatering means connected to the froth flotation means and the reverse flotation means for dewatering the ash-reduced and pyrite-reduced coal; 1. A coal/water fuel production apparatus comprising receiving coal and slurry preparation means for preparing a coal slurry that can be used as a coal/water fuel from the coal. 13) A waste disposal/water treatment means connected to the dewatering means and the reverse flotation means for receiving and treating waste from the dewatering means and the reverse flotation means. The coal/water fuel production device according to item 12. 14) The coal/water fuel production apparatus according to claim 13, wherein the main crushing means comprises a closed circuit wet ball mill. 15) The coal/water fuel production apparatus according to claim 13, wherein the main crushing means comprises an open circuit rod mill. 16) The coal/water flotation method according to claim 13, wherein the froth flotation means comprises one stage or multiple stages of froth flotation connected in sequence depending on the type of coal. Fuel production equipment. 17) The froth flotation means comprises an arcuate sieve, a first set of single stage or series multi-stage floss flotation stages receiving the lower part of the arcuate sieve, and a second set of single stages receiving the upper part of the arcuate sieve. 17. The coal/water fuel production apparatus according to claim 16, comprising a stage or series of multiple stages of froth flotation stage. 18) The coal/water fuel production apparatus according to claim 16, wherein the dewatering means is connected to the froth flotation means. 19) The coal/water fuel production apparatus according to claim 12, wherein the dewatering means comprises a clean coal tank and a vacuum disc type filter. 20) The coal/water fuel production apparatus according to claim 12, wherein the slurry preparation means comprises a ball mill, a screen classifier, and at least one mixer following the ball mill. 21) The dewatering means comprises a clean coal tank and a vacuum disc type filter, the waste disposal means for receiving and treating waste from the filter and the froth flotation means and reverse flotation means. 13. The coal/water fuel production apparatus according to claim 12, wherein the apparatus is connected to a froth flotation means and a reverse flotation means.