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LIQUID SOLVENT EXTRACTION PILOT PLANT - OPERATING PHASE [PHASE 4B]

Objective

The overall project aim is to design, construct and operate a pilot industrial plant for the evaluation of British Coal's Liquid Solvent Extraction Process for the production of transport fuels from coal. Tnis entry refers to part of the Operating Phase of the project, which includes a period of data assessment and reporting after the termination of plant operations.
No technical problems were encountered with the process itself, although certain items and classes of equipment were found to be unreliable. Remedial actions in these areas greatly improved plant operability and over 1000 hours of fully integrated operation was obtained in the final demonstration run. In general, the results obtained were better than had been expected on the basis of smaller scale development. In particular, control of solvent quality and maintenance of solvent inventory were shown to be readily achievable. Liquid product yields in excess of 60%, based on dry, ash-free coal, were obtained without the need to remove any high-boiling material as a pitch-by-product. The space velocity in the hydrocrackers was typically twice that anticipated from smaller scale work, greatly reducing the projected capital cost of a full scale commercial plant. Reassessment of the process economics is to be carried out under contract SF./00095/94/UK. A significant improvement is anticipated.
British Coal is developing a two-stage coal liquefaction process. Coal is dissolved in a process derived solvent, insolubles (including mineral matter) are filtered out and the resulting coal solution is hydrocracked and then fractionated to yield products and recycle solvent.
The objectives of the Project are to:
- demonstrate the process under continuous full recycle operation, determine operational flexibilities and establish the operating envelope
- identify and solve effluent disposal problems
- produce tonnage quantities of light to medium oils for testing
The plant design allows for variations in certain key parameters to allow the investigation and proving of the technical and technological feasibility of the process. In the process, coal is dried, pulverised and slurried with a hydrogen donor solvent (a mixture of aromatic hydrocarbons) produced within the process, pressurized to 24 bar and preheated to 410 deg. C. The slurry is fed to a digester, where 90% of the coal dissolves, cooled to 300 deg. C and depressurised to 2 bar to remove light liquids and gases. Undissolved coal and mineral matter is filtered out, and the filter cake is washed with solvent and vacuum dried. The coal solution is pressurized to 210 bar, heated to 420 deg. C and hydrocracked in two reactors arranged in series with hydrogen injection facilities to cool the reactants. Liquids leaving the hydrocracker are fractionated to give three main liquid products, in the ranges:
- C5 - 250 deg. C (light distillate)
- 250 deg. C - 460 deg. C (basis for recycle solvent)
- pitch (nominally + 460 deg. C)
The pitch may be fed to a delayed coker, to provide an analogue of one configuration of a commercial plant, producing coke and additional solvent, light distillate and gases.
The total project is expected to take approximately 12 years to complete, terminating in 1995, at an overall cost of UK 40 million. The UK Department of Energy and Ruhrkohle AG are participating in the project. Participation by other organisations could be accommodated.

Call for proposal

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Coordinator

BRITISH COAL CORPORATION (RESEARCH ESTABLISHMENT
EU contribution
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Address
COAL RESEARCH ESTABLISHMENT STOKE ORCHARD, CHELTENHAM
GL52 4RZ Gloucester
United Kingdom

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Total cost
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