The digesters may be heated with direct or indirect steam and, in some cases, an outside liquor circulating system is used.
蒸煮锅可以采用直接加热或间接加热方式，有时也使用外部液体循环系统加热。
2
Effect of furnace wall emissivity on surface heat flux of heated stock is analyzed for direct firing furnace and indirect heating furnace.
分析了炉壁黑度对炉膛辐射换热流的影响，分别对火焰直接加热炉和间接加热炉进行了讨论。
3
The paper introduces a continuous car type furnace for direct reduction of iron ore. Coal-containing iron ore pellets are laid on cars and carried to pass through furnace to be heated and reduced.