Title of Invention

A PROCESS FOR REDUCING VARIATION IN DISTRIBUTION OF COAL WATER SLURRY

Abstract

The present invention discloses a process for reducing variation in distribution of coal water slurry in coal preparation plants through the distributor, comprising the steps of providing a cylindrical insert at the center of the distributor lower chamber, providing tangential water inlets in the upper chamber, feeding cola from a feeder provided at the top of the distributor for mixing with water to form coal-water slurry and directing the coal slurry to a set of outlet ports using said cylindrical insert for uniform distribution of coal water slurry.

Full Text

FIELD OF APPLICATION This invention relates to a process for reducing variation in distribution of coal water slurry through the distributor. BACKGROUND OF THE INVENTION The development of large scale coal preparation plants led to the requirement for the subdivision of solid / liquid slurries at a number of stages. The sub- division of slurry feed to a number of unit operations in parallel (e.g., cyclones, spirals and flotation units) is usually accomplished using multi-port distributors, which can have a wide range of shape and dimensions. A typical sputnik multi- port distributor comprises two separated parts, the upper chamber and the lower chamber. The upper chamber is mainly used to enhance the mixing process through the vortex motion, while the lower chamber directs the coal slurry form the top to the outlets at the bottom. The distributor insert is designed in the form of a frustum to push the coal slurry into these outlets. Desirable performance of the distributor is unbiased coal slurry output from all in the outlets. However biased distributors have been reported from coal preparation plants. Since the distributor is the first stage of the coal preparation process, the biased distributions have serious effect on the overall performance of the coal preparation plant, leading to a serious economic loss. The biased sub- division of slurry fed to a number of unit operating in parallel would cause each unit to operate under different separation density, volumetric flow-rate, feed pressure and feed concentration leading to reduced operating efficiencies in mineral and coal preparation plants. Thus, there was a need for obtaining unbiased coal slurry output form all the outlets of the distributor. SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to provide a process for reducing variation in distribution of coal water slurry by modifying feed distribution for feed to the coal preparation. Another object of the invention is to reduce the bias or non-uniformity in distribution. A further object of this invention is to provide a process for reducing variation in distribution of coal water slurry for the modified distributor that would reduce the economic losses due to biased distribution of feed to coal preparation plants and which can be practiced without difficulty. These and other objects of the present invention are achieved by providing a cylindrical insert above the frustum at the center of the distributor in its lower chamber. The cylindrical insert can be extended upto the tangential water inlets provided in the upper chamber. This arrangement is able to arrest formulation of low velocity zones inside the distributor causing non-uniform distribution of coal particles from the distributor outlets. In the present invention four tangential water inlets are provided along with an inverted "V" shaped feeder to allow the feed to fall peripherally in the distributor through an annular ring. This arrangement will further reduce chances of formation of dead zones inside the distributor and thereby causing non-uniform distribution of coal through the distributor outlets. Thus the present invention provides a process for reducing variation in distribution of coal water slurry in coal preparation plants through the distributor, comprising the steps of providing a cylindrical insert at the center of the distributor lower chamber; providing tangential water inlets in the upper chamber; feeding coal from a feeder provided at the top of the distributor for mixing with water to form coal-water slurry; and directing the coal slurry to a set of outlet ports using said cylindrical insert for uniform distribution of coal water slurry. The nature of the invention, its objects and further advantages residing in the same wilt be apparent from the following description made with reference to the non-limiting accompanying drawings. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The invention can now be deserted in detail with the help of the figures of the accompanying drawing in which: Figure 1 shows the existing design of the sputnik distributor in a coal washery. Figure 2 shows the dead zone in the existing design of the distributor that does not participate in the mixing process. Figures 3(a) (b), 3(c) and 3(d) show the reporting of different size of coal particles through different ports of the distributor. Figure 4 shows the velocity contours in the design of the distributor of the present invention Figure 5 shows the design of the distributor of the present invention. DETAILED DESCRIPTION OF THE INVENTION A typical sputnik multi-port distributor as shown in Figure 1. The distributor comprises an upper chamber 2 used for feeding coal through a feeder 3 and for enhancing the mixing of coal, with water fed through tangential water inlets 4 using the vortex motion. The distributor is also provided with a lower chamber for directing the coal slurry from the top to the outlet ports 6. A distributor insert 7 is provided, in the form of a frustum for pushing the coal slurry into onlet ports 6. As described earlier, there have been reports of biased or non-uniforms distribution of coal slurry from the distributor outlets. The problem was studied and the variation of solids flow through different outlets and the variation in size distribution were calculated using two indices the coal split ratio and the variation index. To calculate the variation index, the difference between the maximum percentage and minimum weight percentage of particles of the particular size reporting from the outlets are added. The coal split ratio is calculated as the ratio of maximum solids flow in any outlet to minimum solids flow in another outlet in g / min. As shown in Figure 2, in CFD simulations there exists a low velocity zone at the center to the distributor, which is a dead zone and which does not take part in mixing activity. The major bias in size distribution is observed in the distribution of coarse coal i.e. + 10 mm (in outlets 1 and 5 - outlets directly below the water inlet) since their trajectories were mostly affected by gravitational force. Hence, once caught into the water flow the particles entered the central low velocity zone and went down the port below as shown in Figures 3 (a), 3 (b), 3 (c) and (d). The path of fine particles followed the water flow and they got discharged with water. They were greatly influenced by turbulence. It was noticed that though the water splits were uniform, there was a significant variation in particle distribution. Therefore, alternate designs had to be explored. The non-uniform distribution of coal particles from the outlets could be expected because of the existence of tow velocity regions. Generally the particles are likely to deposit in the low velocity region. In order to arrest these core low velocity regions, various new designs were explored like redesigning the insert. As shown in Figure 5 a cylindrical insert 17 is used in the present invention. This insert 17 can be placed over the frustum 17' of the lower chamber 15 of the distributor 10 of the present invention. The design of a combination of the cylinder and the frustum was able to arrest the formation of low velocity zone inside the distributor 10 as shown in Figure 4. The cylindrical insert 17 can be extended upto the top of tangential water inlets 14. An inverted V feeder 13' is provided below a coal feeder 13 for distributing the coal in an annular ring in the distributor 10 which allows the feed to fall peripherally. It was observed that letting the feed fall peripherally in the distributor further reduced the chance of formation of the dead zone. The summary of the test results with modified inserts and feeding position are shown in Table 1. Table 1: Result showing the value* of (I) variation index and (II) coal split ratio in the present and modified design of the distributor. The least variation index and the coal split ratio were obtained at the optimum conditions (Test 12 in Table 1). Four water inlets 14 with equal water flow in two opposites inlets were used. A cylindrical insert 17 was provided above a frustum 17 as a combination central insert. Symmetrically arranged outlets ports 16 were used. A lower turbulence, a higher volume percentage of solids (20 %) and the particles falling in an annular ring in the distributor 10 were used. As can be seen, the new insert design and distribution in an annular ring have resulted in better distribution of coal particles at higher volume percentage of solids. The new design of the distributor 10 of the present invention is shown in Figure 5. In the present invention the economic losses to variation in coal distributor are reduced. The composite yield from the dense media cyclone increases as a result of addition of the viscosity modifier. WE CLAIM 1. A process for reducing variation in distribution of coal water slurry in coal preparation plants through the distributor, comprising the steps of: - providing a cylindrical insert at the center of the distributor lower chamber; - providing tangential water inlets in the upper chamber; - feeding coal from a feeder provided at the top of the distributor for mixing with water to form coal-water slurry; and - directing the coal slurry to a set of outlet ports using said cylindrical insert for uniform distribution of coal water slurry. 2. The process as claimed in claim 1, wherein said cylindrical insert is provided above the frustum at the center of the distributor lower chamber. 3. The process as claimed in claim 2, wherein said cylindrical insert expands upto the top of the tangential water inlets. 4. The process as claimed in claim 1, wherein four tangential water inlets are provided for inlet of equal water flow through two opposite inlets. 5. The process as claimed in claim 1, wherein said feeder is an inverted "V" type feeder for distributing the coal in an annular ring in the distributor for allowing the feed to fall peripherally. 6. The process as claimed in claim 1, wherein said outlet ports are symmetrically arranged at the bottom of the lower chamber. 7. A process for reducing variation in distribution of coal water slurry in coal preparation plants through the distributor substantially as herein described and illustrated in the accompanying drawings. The present invention discloses a process for reducing variation in distribution of coal water slurry in coal preparation plants through the distributor, comprising the steps of providing a cylindrical insert at the center of the distributor lower chamber, providing tangential water inlets in the upper chamber, feeding cola from a feeder provided at the top of the distributor for mixing with water to form coal-water slurry and directing the coal slurry to a set of outlet ports using said cylindrical insert for uniform distribution of coal water slurry.

Documents:

15-kol-2005-granted-abstract.pdf

15-kol-2005-granted-claims.pdf

15-kol-2005-granted-correspondence.pdf

15-kol-2005-granted-description (complete).pdf

15-kol-2005-granted-drawings.pdf

15-kol-2005-granted-examination report.pdf

15-kol-2005-granted-form 1.pdf

15-kol-2005-granted-form 13.pdf

15-kol-2005-granted-form 18.pdf

15-kol-2005-granted-form 2.pdf

15-kol-2005-granted-form 3.pdf

15-kol-2005-granted-form 5.pdf

15-kol-2005-granted-gpa.pdf

15-kol-2005-granted-reply to examination report.pdf

15-kol-2005-granted-specification.pdf