Coal Mining

Parnaby Cyclones has been a key partner in maximising the efficiency of coal mining for nearly 50 years.  We have developed systems for the washing and separating of different grades of coal, the recovery of fine coal particles and the treatment and disposal of effluent.

Washing and separating improves the saleability of coal.  The end product has:
•  Higher calorific value
•  Lower ash content
•  Potentially lower sulphur content.

There are two main systems for the processing of coal.  One uses a natural medium (water and the raw material) and the other uses a dense medium (with magnetite added).

Natural medium

The natural medium plant is the most cost-effective method of processing easily separated coals - especially run of mine coal for industrial use - and of recovering coal from colliery waste.

The plant uses four types of separating equipment:
•  Barrel
•  Cyclones
•  Dewatering screens
•  Sieve bends.

Operation

Raw material and water are fed into the top of the barrel.  The water combines with the fine coal and shale particles to form a viscous natural medium.  The barrel is angled and the inside is scrolled.  The combination of the viscosity of the medium and the dynamic effect of the barrel revolving causes the coal to float near the top.  The shale, which is heavier, sinks to the bottom and is carried by the scrolls back out of the top end of the barrel.
At the lower end of the barrel there is a sizing screen which lets water and particles smaller than 12mm drain through.  This mixture is pumped to the cyclones.
The larger coal particles pass over a dewatering screen and on to the stock pile.

In the cyclones, the small particles are separated by centrifugal and vortex action (the cyclone itself does not move).  The water/particle mixture is pumped into the side of the cyclone tangentially and swirls around creating a vortex in which the lighter coal particles are sucked to the middle (and out to a dewatering screen).  The heavier shale particles are thrown by centrifugal force to the wall of the cyclone and are discharged at the opposite end.

Options

Parnaby Cyclones makes six sizes of natural medium barrels which can process throughputs of between 20 and 500 tonnes per hour. Cyclone-only plants can be supplied for the cleaning of small coals of less than 40mm particle size.
The modular design of all Parnaby plant allows for several barrels and cyclones to operate together.  A composite natural medium washing plant can process 1,000 tonnes per hour of coal up to 200mm particle size.

Benefits

The Parnaby natural medium washing plant has the following benefits:
•  Low capital cost
•  Low running cost
•  High efficiency
•  Robust modular design
•  Quick to assemble, easy to move
•  Extensive product range
•  Low power use.

Dense Medium

The dense medium washing plant is the most efficient separation process available.  It is ideally suited for
•  Difficult coal separation
•  Cleaning high value coal for domestic and industrial use.

The overall process differs from the natural medium plant because the medium is created using magnetite (fine iron particles) instead of the fine particles in the raw material.  This allows for more control and a wider range of separation gravities.

Operation

This simplified flow diagram shows the dense medium 2 product separation process.
This simplified flow diagram shows the dense medium 2 product separation process
Small and fine particles are removed from the raw material before it is fed into the drum.  First it passes over a dry screen to remove particles smaller than 10mm, and then any remaining fine particles/slimes (smaller than 3mm) are removed by a vibratory rinsing and dewatering screen.  The small particles are then separated in a classifying cyclone.
 
The dense medium drum is horizontal and revolves slowly (about 1 - 3 rpm).  As the raw material enters the drum, magnetite is added via the water circuit to achieve the required density.  Separation is achieved entirely by the buoyancy of the medium; dynamic effect plays no part. The coal floats near the surface of the medium and flows out of the end of the drum.  The heavier shale falls to the bottom of the drum and is moved along the scrolls to perforated lifters which scoop it into a waste chute.

One combined cyclone and dense medium drum plant can process up to 450 tonnes per hour of coal up to 200mm particle size.

Dense medium cyclone-only plants can be supplied for the cleaning of small coals of less than 40mm particle size.

Benefits

The dense medium washing plant can efficiently separate raw material of a wide range of proportions up to 50% coal, 50% shale.  Other benefits include:
•  Choice of 2 or 3 product separator drum
•  Low power requirement
•  High efficiency
•  Low magnetite consumption
•  Robust modular design
•  Quick to assemble, easy to move
•  Can easily be enclosed in a building
•  Extensive product range
•  Single drum capacity up to 250 tonnes per hour.

Fines coal recovery

The natural and dense medium washing plants can recover coal as small as 0.5mm particle size.  Smaller particles pass through the screens and drain to the effluent sump.

We have developed a range of fines coal recovery plants to treat the overflow from the washing plant before it goes for effluent treatment.  These plants can recover and dewater coal particles as small as 100 microns.
 
We supply four products for fines coal recovery:
•  Water-only cyclones
•  Hydrosizers (upward flow separators)
•  Gravity spiral separators
•  Froth floatation cells.