Power Plant Flue Gas Desulfurization Research Articles

In vivo creation of plasmid pCRT01 and its use for the construction of carotenoid-producing Paracoccus spp. strains that grow efficiently on industrial wastes

BackgroundCarotenoids are natural tetraterpene pigments widely utilized in the food, pharmaceutical and cosmetic industries. Currently, chemical synthesis of these compounds outperforms their production in Escherichia coli or yeast due to the limited efficiency of the latter. The use of natural microbial carotenoid producers, such as bacteria of the genus Paracoccus (Alphaproteobacteria), may help to optimize this process. In order to couple the ability to synthesize these pigments with the metabolic versatility of this genus, we explored the possibility of introducing carotenoid synthesis genes into strains capable of efficient growth on simple low-cost media.ResultsWe constructed two carotenoid-producing strains of Paracoccus carrying a new plasmid, pCRT01, which contains the carotenoid synthesis gene locus crt from Paracoccus marcusii OS22. The plasmid was created in vivo via illegitimate recombination between crt-carrying vector pABW1 and a natural “paracoccal” plasmid pAMI2. Consequently, the obtained fusion replicon is stably maintained in the bacterial population without the need for antibiotic selection. The introduction of pCRT01 into fast-growing “colorless” strains of Paracoccus aminophilus and Paracoccus kondratievae converted them into efficient producers of a range of both carotenes and xanthophylls. The exact profile of the produced pigments was dependent on the strain genetic background. To reduce the cost of carotenoid production in this system, we tested the growth and pigment synthesis efficiency of the two strains on various simple media, including raw industrial effluent (coal-fired power plant flue gas desulfurization wastewater) supplemented with molasses, an industrial by-product rich in sucrose.ConclusionsWe demonstrated a new approach for the construction of carotenoid-producing bacterial strains which relies on a single plasmid-mediated transfer of a pigment synthesis gene locus between Paracoccus strains. This strategy facilitates screening for producer strains in terms of synthesis efficiency, pigment profile and ability to grow on low-cost industrial waste-based media, which should increase the cost-effectiveness of microbial production of carotenoids.

Alternative Approach to Current EU BAT Recommendation for Coal-Fired Power Plant Flue Gas Desulfurization Wastewater Treatment

Fossil fuel combustion is a serious environmental problem. Significant quantities of flue gasses and wastewater, requiring further treatment, are produced. This article compares three wet flue gas desulfurization (FGD) wastewater treatment methods: coagulation with precipitation using iron(III) ions—recommended by the European Union as the best available technique (BAT)—and two alternative advanced oxidation processes (Fe2+/H2O2 and Fe0/H2O2). Both oxidation processes that were used met the technical FGD wastewater treatment requirements of the BAT. The best treatment effects, expressed as pollutants’ removal, were obtained for the Fe2+/H2O2 process for 150/300 mg/L reagent doses. It allows effective removal of boron up to 212 mg/L and heavy metals up to below the detection limit <0.010 mg/L for Pb and <0.005 mg/L for Cu. Therefore, the Fe2+/H2O2 process could be an option for FGD wastewater treatment as an alternative to the BAT recommended iron(III)-based coagulation with precipitation. Additionally, an analysis of variance was applied to check the significance of the two independent variables and their interactions. Statistical analysis confirmed high efficiency and applicability of treatment process.

Numerical investigation of multiphase flow in flue gas desulphurization system with rotary jet stirring

There exits multiphase flow of oxygenized air, lime slurry and limestone particles in power plant flue gas desulfurization (FGD) system. A rotary jet stirring device (RJSD) is installed in the slurry pond at the bottom center of absorption tank to get an appropriate mixing flow field so far as possible to get off sulfur dioxide. By employing the standard k-ε turbulence model and the Eulerian multiphase model, numerical investigations for liquid-solid and liquid-solid-gas flow field are presented to discuss the distribution of flow hydrodynamic parameters under a certain operational condition, respectively. In liquid-solid flow, limestone particle concentration shows a decreasing trend with the increase of the rotation angular velocity. The core jet length of the rotary mixer tend to be much longer with the increase of jet velocity under the surrounding pressure, but the dispersed slurry velocity tends to reduce after an initial increasing during the starting period due to the inadequate mixing process. This phenomenon shows that the stirring down-stream is more important than the advection stream in liquid-solid condition. Compared to the liquid-solid condition, the distribution of the air volume of fraction in gas-liquid-solid flow is getting uniform because of the participation of the solid phase, and the down-stream plays an important role in air lateral distribution. The concentration of the limestone particle in liquid-solid condition is higher than in the multiphase flow field. The reason is that the particle distributing velocity near the tank wall is lower and the vertical velocity is higher than in the liquid-solid condition when the jet down-stream velocity is equal. The numerical results could be a useful exploration for an attempt usage of rotary jet device in FGD system.

Mercury and other trace elements in Ohio River fish collected near coal-fired power plants: Interspecific patterns and consideration of consumption risks.

Many coal-fired electric generating facilities in the United States are discharging higher loads of Hg, Se, and other chemicals to receiving streams due to the installation of flue gas desulfurization (FGD) air pollution control units. There are regulatory concerns about the potential increased uptake of these bioaccumulative trace elements into food webs. We evaluated the concentrations of As, total Hg (THg), methylmercury (MeHg), and Se in Ohio River fish collected proximal to coal-fired power plants, of which 75% operate FGD systems. Fillet samples (n = 50) from 6 fish species representing 3 trophic levels were analyzed. Geometric mean fillet concentrations of THg (wet wt), MeHg (wet wt), and Se (dry wt) in 3 species were 0.136, 0.1181, and 3.19 mg/kg (sauger); 0.123, 0.1013, and 1.56 mg/kg (channel catfish); and 0.127, 0.0914, and 3.30 mg/kg (hybrid striped bass). For all species analyzed, only 3 fillet samples (6% of total) had MeHg concentrations that exceeded the US Environmental Protection Agency (USEPA) human health criterion (0.3 mg/kg wet wt); all of these were freshwater drum aged ≥ 19 y. None of the samples analyzed exceeded the USEPA proposed muscle and whole body Se thresholds for protection against reproductive effects in freshwater fish. All but 8 fillet samples had a total As concentration less than 1.0 mg/kg dry wt. Mean Se health benefit values (HBVSe ) for all species were ≥ 4, indicating that potential Hg-related health risks associated with consumption of Ohio River fish are likely to be offset by adequate Se concentrations. Overall, we observed no measurable evidence of enhanced trace element bioaccumulation associated with proximity to power plant FGD facilities, however, some enhanced bioaccumulation could have occurred in the wastewater mixing zones. Furthermore, available evidence indicates that, due to hydraulic and physical factors, the main stem Ohio River appears to have low net Hg methylation potential.

Effect of Power Plant Flue Gas Desulfurization Gypsum on Saturated Hydraulic Conductivity of Heavy Soda-Saline Soil Using Lysismeter

Effect of Power Plant Flue Gas Desulfurization Gypsum on Saturated Hydraulic Conductivity of Heavy Soda-Saline Soil Using Lysismeter

Coal-Fired Power Plant Flue Gas Desulfurization Wastewater Treatment

Coal-Fired Power Plant Flue Gas Desulfurization Wastewater Treatment

Research and Design of the PLC-Based Control System for Thermal Power Plant Flue Gas Desulfurization

According to the characteristics of Wet Flue Gas Desulphurization (FGD), this paper brings forward the automatic control requirements and the control methods. The automatic control system is composed of a Programmable Logic Controller (PLC) and an industrial control computer (PC). The automatic control system can monitor the operating parameters of FGD system automatically and conduct automatic control and adjustment to FGD system. The PLC is responsible for the data collection and automatic control, while the PC is responsible for the surveillance of FGD system operation and the data processing through mutual communications between PC and PLC, which realizes the communication between human and machine and ensures the safe, stable and economic operation of the FGD system.

Sulfur and Carbon Cycling in a Flue Gas Desulfurization Sludge Disposal Site

Products of a power plant flue gas desulfurization scrubber are discharged into a pond as sludge consisting of calcite (initial δ13C 3.2–3.8‰), gypsum (initial δ34S 7.6–8.6‰), and aqueous solution. Reducing conditions exist below a boundary that appears to move vertically as a function of changes in pond water level. Under reducing conditions, bacteria partially reduce aqueous sulfate to low-δ34S sulfide, consuming organic carbon and generating low-δ13C bicarbonate. Under oxidizing conditions, sulfide is converted to sulfate, leading to calcite dissolution, gypsum precipitation, and isotopic re-equilibration of remaining calcite with dissolved bicarbonate near the pond surface. The gypsum has δ34S near 6‰, and calcite has δ13C as low as -1.7‰; the changes from initial values correspond to predictions based on isotopic balance and reaction stoichiometry. The pond largely contains the products of bacterial reduction. After the pond is abandoned, these products may adversely affect attempts to revegetate the site. Future bacterial reduction may be best controlled by dewatering and limiting the supply of organic matter in percolating surface water.

The Importance of Maintenance for Lime Flue Gas Desulfurization Systems

The successful, reliable operation of a power plant flue gas desulfurization (FGD) system depends largely on a good program of maintenance. Identifying the FGD equipment that is most critical to an FGD system’s overall reliability or its ability to meet emission regulations plays an important role in determining the extent of a maintenance program for a particular site. FGD maintenance programs vary considerably, depending on site-specific requirements and the support of plant owners. Many owners are reluctant to spend money on FGD maintenance because an FGD system is a nonproductive part of a power plant; however, a good maintenance program can result in longer equipment life, improved equipment performance, increased system availability, better safety, and lower operating costs. This paper uses wet and dry lime FGD systems to illustrate the advantages of good maintenance and the consequences of poor maintenance. Examples of specific tasks for preventive, scheduled, planned, and emergency maintenance are...