Hydrothermal treatment to remove sodium from high sodium coal and its influence on combustion characteristics

Considering the form of sodium existing in coal, series of water washing and hydrothermal treatments were used to remove alkali metals from a high sodium coal from Wucaiwan. The variation of combustion characteristics of coal after pretreatment was investigated. The results show that the sodium in the coal mainly exists as water-soluble form. The Na removal ratio by water washing treatment does not reach the expectation with the characteristics of time consuming and high water consumption. The hydrothermal treatment is effective in sodium removal as high as 90.5%, and Na₂O content in the ash decreases to 0.7% which belongs to the scope of low sodium level in coal ash. The burning curves of coal samples after hydrothermal treatment move to the low temperature zone, and the combustion characteristics is improved compared with raw coal.