Mercury Absorption And Speciation Dynamic Changes In Sludge During Flue Gas Drying

Drying treatment of sewage sludge is one of the dewatering techniques widely used, attributing to its notable effect on reducing the amount and volume of sewage sludge. While heavy metals are supposed to enrich in the dried sludge, which will produce threaten to the environmental safety. The aim of the present work was to establish the effect of drying treatment on the distribution and mobility of heavy metal Mercury (Hg) in sludge and at the same time, to study the mercury absorption of municipal sludge during flue gas drying at low-temperature and develop the cheap adsorbent.On the basis of testing the mercury contents and analyzing the speciation of municipal sludge, printing and dyeing sludge and paper sludge, simulated experiments were designed to system study the mercury content and speciation changes and analyze the reasons. Results showed that the mercury content of sludge from most to least was municipal sludge, printing and dyeing sludge and paper sludge. When the sludge was drying at the temperature between 25℃to 100℃,the reducing of moisture content didn’t lead to the precipitation of mercury. With the drying temperature increased between 100℃to 200℃, the mercury content decreased slowly, When between 200℃to 300℃,a lot of mercury volatized. At the temperature of 400℃,there was no mercury in the sludge. There was no acid-soluble mercury and reduced mercury in the sludge and only existed oxidisable and residual mercury. With the drying temperature increased, the oxidisable form was transformed gradually into the residual form until all the forms were transformed to the residual form, indicating that the increase of drying temperature would cause the heavy metals like mercury to be more stable.After the detailed discuss of the characteristics of coal-fired flue gas mercury, mercury detection technology, different sorbent and flue gas purification device for mercury adsorption and removal, the advanced platform on researching mercury forms transform and control was used to study the sewage sludge drying at 150℃as an adsorbent of its effect on the adsorption of mercury in simulated flue gas. The ways to describe the characteristics of the adsorbents were systematically introduced and the basic data to support efficiency and mechanism of different adsorbents were provided. The experiments showed that the drying of sewage sludge on the mercury adsorption efficiency was about 10% to 30%.