Current UK coal preparation status
Following the privatization of the mines in 1994 , the UK coal industry has been run by three major companies. Scottish Coal in Scotland, Celtic Coal in Wales and UK Coal pic in England. The bulk of the coal is produced for power generation and the coal preparation processing policy has been to remove the finest material from the raw coal, wash the coarser fractions and to blend the two products together to form a saleable product having around 15% ash content. This applies to both deep mined coal and that obtained from opencast sites which is roughly half the total output.
The fact that deep cleaning is not necessary, the traditional use of dense medium systems and Baum jigs has been replaced in many instances by Barrel Washers. These units can treat raw coal up to 125 mm in size, separating at around 1. 6~1. 8 RD, producing a clean coal at an ash content suitable for blending with the untreated fines. Loss of coal in discard is found to be within acceptable limits (1. 5%~2. 0% floats at 1. 6 RD). Small coal that is present in Barrel Washer feeds is further cleaned in natural medium cyclones.
Until recently the largest coal preparation plant in the UK was at Gascoigne Wood operating this system, treating 3 000 tons/hour in Barrels and water only cyclones for many years. However as the quality of the run of mine deteriorated and the demand by the power stations for lower ash coal, a 800 ton/hour small coal dense medium plant and a column flotation unit was added to provide more clean coal for the blend. Unfortunately this plant closed in 2005 following the exhaustion of coal in the mine.
There is now only one mine in the UK producing anthracite, a privately owned mine in Wales. There are no deep mines in Scotland, all the coal is produced from opencast sites.
There is still some coal produced from tip washing sites where old waste heaps, many dating back 100 years, are being leveled and landscaped. During the landscaping the waste is treated usually by Barrel Washers to recover the coal.
For many years coal preparation plants were operated by the mine owners. However towards the end of public ownership under British Coal there was a tendency to employ private contractors to operate and maintain coal preparation plants. Competitive tenders were invited from up to three different contractors who were required to provide a price per ton for treating the raw coal. The price had to include all operating and maintenance labour as well as consumables such as oils, greases and flocculant reagents. The contacts would be let for a period of three years and at the end of the contract period the plant had to be returned to the mine owners in the same condition as at the start of the contract. Minimum tonnage would be agreed, which meant the contractor was guaranteed an amount of money if the mine fell short on raw coal. In some instances there was a sliding scale of charges per ton if the tonnage exceeded certain values. The contractor would be expected to meet guarantees of performance in terms of coal quality and losses of coal in rejects, with penalties for failure to comply.
Where it was considered that the existing plant could was not suitable for current market requirements, contractors would be asked to tender for the installation and operation of a plant. Cost to be recouped by charging on a tonnage rate. The contracts generally were for a three year period and it can be appreciated that the equipment provided was very basic, since the contractor had to recoup his capital investment over the three years. Similar contracts were awarded for washing and landscaping old tips.
At present there are no plans for opening up new mines. Although coal still supplies one third of the UK’s energy requirements, see Fig. 1, more than two thirds of the coal burnt at power stations is imported from places like South America, Poland and South Africa. Coal for carbonization is mainly imported from Australia. Fig. 2.
Until recent times imported coal has been less expensive than UK coal and had the added advantage of being lower in sulphur content. However in the past two years the price of imported coal has risen sharply, due in part to higher shipping costs. Coal in the UK has benefited from that increase having gone from a low of less than $ 30 US/ton in 2003 to $ 75/80US/ton in 2005. See Fig. 3. This has meant that some mines that were due for closure have continued to operate.
As stated the UK coal industry is barely one tenth of what it used to be and coal preparation has suffered a similar decline. At one time there where almost 500 operating coal preparation plants now there is no more than about 15. There is still plenty of coal in reserve, whether it will ever be mined in a conventional way is a matter of speculation. If one is to believe that carbon emissions are damaging the earth’s atmosphere then in practical terms the only alternative is the generation of electric power by nuclear means.
|.Total (including slurry)||130.1||92.8||31.2||30.0||28.3||2S.1|