Coal-water slurry: A status report

During the years of oil shortage and rapidly increasing oil prices, the need to decrease dependence on oil-fired utility boilers became an urgent concern. The alternatives were to: 1.(1) build new coal-fired stations;2.(2) modify oil-fired boilers to fire pulverized coal;3.(3) modify oil-fired boilers to fire coal slurry;4.(4) modify boilers to fire deeply cleaned, finely pulverized coal; or5.(5) fire coal-derived liquids. Of these alternatives, the use of the coal-water slurry (CWS) promised a combination of advantages: near-term readiness, low-fuel costs compared to oil, moderate conversion costs, and low technical/economic risks. The development work sponsored and peformed since 1979 with coal-water slurries (70 wt % coal, 29 wt % water, 1 wt % additives) has confirmed these expectations. Fuel quality guidelines and test standards have been established, production of CWS in 40,000–150,000 ton/yr pilot plants has been demonstrated, utility-scale burner systems (100 MBtu/hr) have been demonstrated, and the effects and costs of modifying typical utility boilers have been predicted. Limited field handling, storage, and use tests were completed successfully.