AU720167B3

AU720167B3 - Process for reclaiming coal fines from coal slurry

Info

Publication number: AU720167B3
Application number: AU48837/99A
Authority: AU
Inventors: Robert Pieter Du Preez
Original assignee: SLURRY RECLAIMERS CC
Current assignee: SLURRY RECLAIMERS CC
Priority date: 1998-09-21
Filing date: 1999-09-21
Publication date: 2000-05-25
Anticipated expiration: 2005-09-21

Description

P/00/012 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION PETTY PATENT Invention Title: Applicant: PROCESSES FOR RECLAIMING COAL FINES FROM COAL SLURRY SLURRY RECLAIMERS CC The following statement is a full description of this invention, including the best method of performing it known to me: 1 Document4 BAKGRUNDT TE DfNON.

This invention relates to processes for recliming coal fines from coal 8isury.

SUMMARY OF INVENTION According to the invention there is provided a process for reclaiming coal fines from coal slurry, the process including the steps of: a process for reclaiming coal fines from coal slurry, the process including the steps of: pumping a slurry containing coal fines into a slurry pond to form a wet coal sediment; mechanically treating an upper layer of from 10 to 500 mm of the coal sediment when said upper layer has dried to a moisture content of between to 35%; and removing the upper layer of mechanically treated coal sediment when it has dried to a moisture content of from 17% to 11%.

Typically, the sediment is mechanically treated with equipment which is adapted to travel over coal sediment having a moisture content above 20%, usually not more than The mechanical treatment is preferably by way of scarification or compaction.

Typically, the sediment is compacted with compaction equipment in the form of rollers and/or vibration equipment.

DETAILED DESCRIPTION OF EMBODIMENTS Coal slurry containing coal fines in suspension from coal wash plants is pumped and deposited in slurry ponds. Slurry ponds vary in size but generally range from an area of 6,000 to 40,000 m 2 The depth of the ponds range from between 2 to 8 m.

Once the slurry the has been pumped into a pond, excess water is decanted from the pond by way of pumping or by allowing the water to flow out of the pond under gravity. During this time, the coal fines settle to form a wet sediment. The wet sediment is then allowed to dry in the atmosphere.

Accordingly, the speed with which the sediment dries depends on prevailing weather conditions. When the upper layer of the sediment is at a moisture of greater than 20% and up to as much as 35%, it is scarified cut, turned and loosened) with vehicles carrying scarifying equipment to expose more sediment to the atmosphere to make the sediment dry faster.

Coal sediment having a high moisture content of greater than 20% is unstable and has poor vehicle bearing capacity. The vehicles used in the process according to the invention to scarify the sediment are specially adapted to travel over coal sediment having a moisture content above 20% and as high as 35% and are fitted either with wide tracks or wide tyres. The type of vehicle used is typically a tractor and the scarifying equipment is a rotavator or plough which rips, cuts and turns the sediment up to a depth of approximately 500 mm The upper layer of sediment is scarified until it reaches a moisture content of from 17% to 11% whereafter an upper layer of between 10 to 500 mm of sediment is removed by an earth moving machine such as a front end loader.

At moisture contents lower than 11%, coal fines in the sediment become fine coal dust which blows away and which can cause serious health andi pollution problem. At moisture contents Uiglier than 171/c, there is a tendency for the coal particles to adhere to surfaces that they comae into) contact with and this results in blockages and retards the flow of coal into, storage containers.

The coal mateirial removed by the earth moving machine is then moved to a crusher where it is crushed to break up any large lumps or clods and it is then fed on to a conveyor belt which transports the coal fines to a power station.

The clods and lumps may be used as a component of a mixc of fu~el for the power station- The process described above continues until the slurry pond is empty.

The main benefit of starting to scarify the sediment when it is at a high moisture content (above 20% and up to is that the whole process can be started sooner and carried out more quickly (the sediment takes less time to dry) which results in less area required to construct slurry ponds- Slurry ponds can therefore be made smnaller. This is particularly advantageous in.

view of the fact that the cost of rehabilitating the area is reduced when the operation is discontinued. Another benefit is th-at productivity is increased.

A further benefit is that the coal fines may be transported and used as a source of power for power stations and thus do not go to waste.

According to another aspect of the invention, instead of scarifying the sediment, the sedirnept is compacted. Coal sediment having a moisture content of greater than 20% and up to 35% is compacted by using towed or self-propelled rollers or impact rollers. Several passes using the compaction equipment take place until the sediment has reached the required state of compaction- Vibration may also be employed to improve the efficiency of the operation. This compaction step serves to dry the top layer of sediment by building up a high pore pressure withiin the high moisture content sediment to force moisture out of the layers of sediment.

When the top layer of the sediment reaches a moisture content of from 17% to 11 a layer of 10 to 5 00mm of sedimenit is removed in a manner as described above. The exposed sediment layer is then compacted and the process is continued until the slurry pond is empty- The step of compacting the sediment means that the sediment reaches acceptable moisture content for removal more quickly so that the process can be carried out more quickly (as explained above), and this results in less area requaired to construct slurry ponds and slurry ponds can be made smaller.

Claims

1. A process for reclaiming coal fines from coal slurry, the process including the steps of: pumping a slurry containing coal fines into a slurry pond to form a wet coal sediment; mechanically treating an upper layer of from 10 to 500 mm of the coal sediment when said upper layer has dried to a moisture content of between to 35%; and removing the upper layer of mechanically treated coal sediment when it has dried to a moisture content of from 17% to 11

2. A process according to claim 1 wherein the sediment is mechanically treated with equipment which is adapted to travel over coal sediment having a moisture content above

3. A process according.to claim 1 or claim 2 wherein the mechanical treatment is by way of scarification or compaction. DATED: 22 March, 2000 PHILLIPS ORMONDE FITZPATRICK Attorneys for: SLURRY RECLAIMERS CC