Mercury emissions from polish pulverized coalfired boiler

The current paper presents the research results carried out at one of Polish power plants at a pulverized hard coal-fired 225 MW unit. The research was carried out at full load of the boiler (100% MCR) and focused on analysis of mercury content in the input fuel and limestone sorbent for wet flue gas desulfurization (FGD) system, as well as investigation of mercury content in the combustion products, i.e. fly ash, slag, FGD product (gypsum) and FGD effluents (waste). Within the framework of the present study the concentration of mercury vapor in the exhaust gas was also investigated. The analysis was performed using Lumex RA-915+ spectrometer with an attachment (RP-91C). The measurements were carried out at three locations, i.e. before the electrostatic precipitator (ESP), downstream the ESP, and downstream the wet FGD plant. Design of the measurement system allowed to determine both forms of mercury in the flue gas (Hg0 and Hg2+) at all measurement locations.Based on the measurement results the balance of mercury for a pulverized coal (PC) boiler was calculated and the amount of mercury was assessed both in the input solids (fuel and sorbent), as well as the gaseous and solids products (flue gas, slag, ash, gypsum and FGD waste)

Mapping the substrate-binding subsite specificity of a Porphyromonas gingivalis Tpr peptidase

Calcium-dependent peptidases of the calpain family are widespread in eukaryotes but uncommon in prokaryotes. A few bacterial calpain homologs have been discovered but none of them have been characterized in detail. Here we present an in-depth substrate specificity analysis of the bacterial calpain-like peptidase Tpr from Porphyromonas gingivalis. Using the positional scanning hybrid combinatorial substrate library method, we found that the specificity of Tpr peptidase differs substantially from the papain family of cysteine proteases, showing a strong preference for proline residues at positions P2 and P3. Such a degree of specificity indicates that this P. gingivalis cell-surface peptidase has a more sophisticated role than indiscriminate protein degradation to generate peptide nutrients, and may fulfil virulence-related functions such as immune evasion

Influence of RDF composition on mercury release during thermal pretreatment

The growing world population is contributing to the increasing amounts of waste and a significant increase in energy demand. Therefore, coal will increasingly be replaced by refuse derived fuel (RDF), which is produced from municipal solid waste. The use of such fuel poses many difficulties because of its heterogeneity and high mercury emission. One method to stabilize the properties of RDF and reduce the mercury content is thermal pretreatment. The purpose of this study was to investigate the release of mercury from RDF samples following thermal pretreatment. The study was carried out in the temperature range of 100–350 ◦C. Statistical analysis was performed on the correlation between the composition of the RDF samples and the release of mercury. The RDF samples showed a very high variation in the mercury content, ranging from 45 to 849 µg Hg/kg (1.7 to 35.3 µg Hg/MJ). Thermal pretreatment removed a significant amount of mercury at 250 ◦C (94–99%). Paper content positively affected mercury release. Relatively low correlation coefficients were obtained in the statistical analysis, which may be explained by the significant heterogeneity of the RDF samples magnified by the variability in the mercury content within particular fractions.Web of Science162art. no. 77

Enhancing the removal of hazardous pollutants from coke making wastewater by dosing activated carbon to a pilot‐scale activated sludge process

Powdered activated carbon (PAC) was investigated for its ability to remove 6 polycyclic aromatic hydrocarbons (Σ6PAHs) (fluoranthene, benzo[b + J]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, benzo[g,h,i]perylene), trace metals and colour from coke making wastewater when dosed to a pilot-plant activated sludge process (ASP). The ASP had a volume of 0.68 m3 and was operated to simulate the full-scale ASP treating coke wastewater from a steel works. Operational conditions included a flow rate of 0.78 m3/day, a hydraulic retention time of 21 hours, a sludge retention time of 38 days and a temperature of 27°C. The ASP was operated for a control period before PAC was dosed directly into the aeration cell at a dose of 400 mg/L. Powdered activated carbon addition resulted in a 20% increase in removal efficiency of the Σ6PAHs. Removal efficiency of trace metals was variable, but increased for nickel, chromium and cadmium by 22.6%, 20.5% and 12.4%, respectively. Improvement in colour removal efficiency was marginal at 5%. PAC addition allowed the improvement of treatment efficiencies in the ASP process at relatively low capital and operational costs, which may assist in reaching tighter effluent emission limits set for the industry