The feeding of coal-water mixtures (CWMs) into a pressurised fluidised-bed combustor (PFBC) could considerably simplify the more usual method of pneumatically-feeding dried coal from lock hoppers. The UK National Coal Board has developed a flow sheeting computer package ARACHNE, and it has been used to evaluate the effect of additional moisture on cycle efficiency and plant output. The evaluation showed that operation with a CWM containing 30% water would lower the cycle efficiency by only 0.8 percentage point and have little effect on the overall plant output. An experimental program is being undertaken at CURL, to assess the performance (e.g., combustion efficiency, sulphur retention) when burning CWMs. Some initial tests are described. Operation using CWMs with solids contents of 65, 70 and 75% was extremely steady with excellent control of bed temperature. Combustion efficiency was greater than 99% at 1560/sup 0/F bed temperature and about 98% at 1380/sup 0/F bed temperature, which equals efficiencies obtained when burning normal crushed coal at comparable conditions in this combustor. Sulphur retention performance was somewhat better than has been obtained with a normal (high sulphur) crushed coal in this combustor with the same sorbent. NO/sub x/ emissions varied between 0.25 and 0.47 lb/10/sup 6/ Btu, depending on excess air - similar to values obtained on other rigs with normal crushed coal. Results from the limited tests carried out so far are extremely promising. Further tests are planned. (LCL)