Technologies for remediation of wastewater by industrial solid waste have recently attracted interest. Acid mine drainage is an extraordinarily acidic and highly heavy metal ions contaminated leachate which posed some challenges for the environment. Nonetheless, steel slag shows significant potential application prospects in wastewater treatment, due to its excellent physicochemical properties and structures. This paper elaborately reviewed the structure, properties, water treatment applications of steel slags, and the mechanism for removing heavy metal ions from acid mine drainage, discussed the problems existing in industrial wastewater treatment by steel slag, and proposed the solutions for future research, aiming to provide theoretical references for the practical application of steel slag in AMD treatment.
Research has been conducted under United States Department of Energy Contract (USDOE) DE-AC21-86MC21023 to develop a new type of coal-fired plant for electric power generation. This new type of plant, called a Second Generation Pressurized Fluidized Bed Combustion Plant (2 nd Gen PFB), offers the promise of efficiencies greater than 48%, with both emissions and a cost of electricity that are significantly lower than those of conventional pulverized coal-fired (PC) plants with wet flue gas desulfurization/scrubbers. The 2 nd Gen PFB plant incorporates the partial gasification of coal in a carbonizer, the combustion of carbonizer char in a pressurized circulating fluidized (PCFB) bed boiler, and the combustion of carbonizer syngas in a topping combustor to achieve gas turbine inlet temperatures of 2700°F and higher. Under the USDOE Clean Coal V Demonstration Plant Program, a nominal 260 MWe plant demonstrating 2 nd Gen PFB technology has been proposed for construction at the McIntosh Power Plant of the City of Lakeland, Florida. In the September-December 1997 time period, four test runs were conducted in Foster Wheeler's 12-inch diameter carbonizer pilot plant in Livingston New Jersey to ascertain carbonizer performance characteristics with the Kentucky No 9 coal and Florida limestone proposed for use in the Lakeland plant. The tests were of a shortterm nature exploring carbonizer carbon conversions, sulfur capture efficiencies and syngas alkali levels. The tests were successful; observed carbonizer performance was in agreement with predictions and no operating problems, attributed to the planned feedstocks, were encountered. The results of the four test runs are reported herein.
Steel slag has been proven to be an effective environment remediation media for acid neutralization, and a potential aid to mitigate acid mine drainage (AMD) in passive treatment process. But its acid neutralization capacity (ANC) is frequently inhibited by precipitate after a period of time, while the characteristic of the formation process are unclear yet. In this work, ANC of the SS sample was tested using simulated AMD (H2SO4, 0.1M) and real AMD. Steel slag and AMD has been characterized on pH, ANC, as well as Ca, Mg, Al, Mg-bearing ingredients. Microscopic properties characterization and neutralization experiment results shown that Ca-bearing constitutes leaching and sulfate formation were the two main categories reactions throughout the neutralization process. A prominent transition point of the two kind reactions was selected at 40 % of the neutralization process. Microscopic properties characterization indicated Ca3SiO5 (C3S) played a dominant role among Ca-bearing components in alkaline releasing stage for the present sample. Morphology, pore distribution, composition, surface area and other microscopic properties of the neutralized slag were significantly changed by the crystallized CaSO4 precipitates in sulfate formation stage, which hindered the alkaline releasing behaviors gradually. Neutralization experiments conducted by real AMD suggested that the steel slag ANC property was also influenced by the contained high concentration metal ion due to the precipitate reactions except for sulfate formation reactions.
Mercury in flue gas of coal-fired plants was concerned as another serious pollution when sulfur dioxide pollution was controlled now. The adsorbent made from fly ash by thermal precipitation sulfur to remove mercury in fuel gas from coal combustion plant, SEM, BET, TGA and other measurement methods were used to characterize the effect on surface morphology, sulfur distribution and specific surface. High temperature deposition furnace was applied to increase sulfur content in fly ash based adsorbents produced in lab. The study found that sulfur attached to the adsorbent surface, mesopore and microporous structure, increasing its sulfur content of adsorbent. Sulfur was filled in interspace as small molecule S 2 , S 5 , increased their surface area and enhanced their adsorption capacity. The specific surface area increased by thermal precipitation sulfur, and specific surface area which increased with increasing temperature.
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