Flue Gas Desulfurization Wastewater Treatment for Coal-Fired Power Industry

Abstract

The United States Environmental Protection Agency (USEPA)’s announcement that it will revise the effluent limitation guidelines for steam electric power generating units could affect not only how power plants use water, but also how they discharge it. The revised guidelines may lower discharge limits for various contaminants in flue gas desulfurization (FGD) wastewater including mercury, selenium, arsenic, and nitrate/nitrite. Although the specific details of the guidelines are unknown at present, the power industry is evaluating various technologies that may address the new effluent limitation guidelines and promote water conservation. Moreover, the power industry is looking for avenues to increase water usage efficiency, reuse and recycle throughout its plant processes. Final rule approval is expected by the middle of 2014 and new regulations are expected to be implemented between 2017 and 2022 through 5-year NPDES permit cycles. discharge limits for various contaminants including arsenic, mercury, selenium, and nitrate/nitrite [1]. These pollutant limits may be below the levels achievable today with conventional treatment [2]. A growing interest exists in zero liquid discharge (ZLD) facilities and processes in power plant operations. Potentially stringent discharge limits along with water conservation and reuse efforts are two of the major drivers to achieve ZLD. Potential pollutant levels are so low that ZLD may be the best option, if not an outright requirement [1]. Thermal ZLD systems have been the subject of increased interest and discussion lately. They employ evaporating processes such as ponds, evaporators and crystallizers, or spray dryers to produce a reusable water stream and a solid residue (i.e. waste). Evaporators and crystallizers have been employed in the power industry for a number of years. However, typical A growing interest exists in zero liquid discharge (ZLD) facilities and processes in power plant operations. Potentially stringent discharge limits along with water conservation and reuse efforts are two of the major drivers to achieve ZLD. Potential pollutant levels are so low that ZLD may be the best option, if not an outright requirement. A key disadvantage of thermal ZLD is its high capital cost. One way to reduce this cost is to pre-treat the liquid stream using innovative membrane technologies and reverse osmosis (RO).

Energy Efficient Waste Heat Coupled Forward Osmosis for Effluent Water Management at Coal-Fired Power Plants

“…The composition of the FGDWW used in this study was similar to that reported for Plant Bowen in Georgia, USA, operated by Georgia Power (Pakzadeh, 2014). The concentrations of magnesium (Mg 2+ ) and calcium (Ca 2+ ) contribute high hardness to the as-is FGDWW.…”

Current Status of Zero Liquid Discharge Technology for Desulfurization Wastewater

“…This method involves the collection of samples of desulfurization wastewater from the desulfurization system to understand the composition and nature of the wastewater, and via testing and sample analysis, the main types and concentrations of pollutants in the wastewater are determined. Next, the pH of the wastewater is adjusted, usually by adding a neutralizing agent Ca(OH) 2 , and proper pH adjustment contributes to the mildness of the treatment environment and promotes subsequent chemical reactions and precipitation formation [13]. In general, precipitants for pH adjustment include Ca(OH) 2 , NaOH, FeCl 3 , and AlCl 3 [14].…”

Experimental and model research on chloride ion gas–solid distribution in the process of desulfurization wastewater evaporation

“…8. The nal chloride ion gas-solid phase distribution coefficient model is showed in the form of formula (13): The comparison of the calculated results for the heterogeneous distribution coefficient of chloride ion with the other similar studies is shown in Table 6. It can be obviously seen that the experiment object of this study is aimed at the distribution of chloride ion between gas and solid phase, while the other researches focused on gas and liquid phase.…”

“…Thus, a series of ZLD technologies are being developed gradually, the comparison for ZLD technology routines in recent years are shown in Table 1 in detail. [12][13][14][15][16][17] Two feasible technical routes were put forward to achieve ZLD of desulfurization wastewater in China. Flue gas evaporation drying and crystallization were suggested.…”