Water in Brown Coal and Its Removal

The brown coals of Victoria represent an important state and national resource. This chapter deals with the physics, chemistry and analytical aspects of water in brown coal. Victorian brown coals show sigmoid isotherms, typical for physical adsorption of condensable vapors on porous substances. The chapter describes drying and dewatering technologies and emphasizes the binderless briquetting technology for brown coal, where water in the coal plays a critical role. In considering the drying requirements of low rank coals, it is informative to express the moisture content on a dry coal basis to indicate the quantity of water to be removed per unit mass of dried coal and hence the energy which has to be provided. The high moisture content of low rank coals has led to the development of a plethora of drying processes, but a major breakthrough on drying cost is still awaited. Water removal processes for low rank coals can generally be divided into evaporative drying or non-evaporative dewatering, where the water is removed from the coal in liquid form.