Several researchers have determined that water (H2O) and sulfur dioxide (SO2) in a flue gas stream have an impact on the amount of elemental mercury (Hg0) that is homogeneously oxidized by a chlorine-containing species. Generally, it is concluded that H2O inhibits Hg oxidation by chlorine (Cl2). However, doubt remains as to whether SO2 promotes or inhibits Hg oxidation. Further, most published results seem to indicate that nitric oxide (NO) does not have a significant impact on Hg oxidation. This paper will present data taken in a laboratory-scale apparatus designed to test these observations. In this work, Cl2 is intentionally added to a synthetic flue gas stream containing known amounts of elemental mercury. This gas blend is similar to a flue gas obtained by burning Powder River Basin coal in a pulverized coal fired power plant and is subject to a time−temperature profile similar to a power plant. The results obtained show that H2O, SO2, and NO all have an inhibitory effect on the homogeneous oxidation of Hg by Cl2. Further, the presence of H2O increases the inhibitory effect of SO2 and NO. Two new reactions are proposed to explain these results, in which SO2 and NO react with Cl2. The consequences of these reactions are a reduction in the oxidative interactions that take place between Hg and Cl2, thus decreasing the amount of Hg oxidation that occurs.

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Staged combustion is an effective technology to control NOx emissions for coal-fired boilers. In this paper, the characteristics of NOx emissions under a high temperature and strong reducing atmosphere conditions in staged air and O2/CO2 combustion were investigated by CHEMKIN. A methane flame doped with ammonia and hydrogen cyanide in a tandem-type tube furnace was simulated to detect the effects of combustion temperature and stoichiometric ratio on NOx emissions. Mechanism analysis was performed to identify the elementary steps for NOx formation and reduction at high temperatures. The results indicate that in both air and O2/CO2 staged combustion, the conversion ratios of fuel-N to NOx at the main combustion zone exit increase as the stoichiometric ratio rises, and they are slightly affected by the combustion temperature. The conversion ratios at the burnout zone exit decrease with the increasing stoichiometric ratio at low temperatures, and they are much higher than those at the main combustion zone exit. A lot of nitrogen compounds remain in the exhaust of the main combustion zone and are oxidized to NOx after the injection of a secondary gas. Staged combustion can lower NOx emissions remarkably, especially under a high temperature (≥1600 °C) and strong reducing atmosphere (SR ≤ 0.8) conditions. Increasing the combustion temperature under strong reducing atmosphere conditions can raise the H atom concentration and change the radical pool composition and size, which facilitate the reduction of NO to N2. Ultimately, the increased OH/H ratio in staged O2/CO2 combustion offsets part of the reducibility, resulting in the final NOx emissions being higher than those in air combustion under the same conditions.

In terms of CO2 emissions, the year 2030 has been addressed as a very crucial deadline for both European Union (EU) and the U.S. Whereas the U.S. Clean Power Plan proposes the reduction of national CO2 emissions from the existing power stations by 30% with respect to 2005, the EU aims at cutback by 40% from their levels in 1990. Due to the restricted emission goals dictated by the European and U.S. energy policies, both energy markets witness currently drastic changes. Whereas the U.S. wants to shift away from coal, the EU shifts away from gas due to high natural gas prices in Europe while drastically increasing the feed-ins from renewable energy sources (RES). In some of the European countries constantly growing installation of renewable energy plants is superseding natural gas-fired power plants and thus causing the electrical grid stabilization to be overtaken by coal fired power stations. On the contrary, the U.S. market due to increasing extraction of shale gas and low natural gas prices puts the gas power plants in favor and poses increasing pressure on closing some coal fired plants. A solution that uses the potential of the existing site and reduces overall emissions is converting from coal into gas-fired power plants, so-called fuel switch. Whereas for the U.S. market the later solution is relevant, in the vast majority of EU Member States the focus is on increasing the flexibility of coal fired power plants. The challenges and technical solutions developed and applied according to the demands of the market in both EU and U.S. are addressed in this paper. Both currently applied technologies and technologies under development are shortly presented.

A new gas supply system for residents was designed, taking puleyuan village as the research object. Aiming at the rural areas with abundant biomass energy and considering the seasonal difference of gas supply to residents, the gas supply system with biomass gasification coupled with hydrocarbons was used. Through the analysis of the system design principle, the calculation of combustible mixture property and the numerical calculation of energy conversion process, the energy efficiency design of the system was analyzed and optimized in this paper. At the same time, the system was evaluated from the economic perspective of energy conservation and emission reduction, compared with those of traditional fossil energy heating. The results showed that the gas supply system could bring considerable economic and environmental benefits, and it was feasible and expansible to implement in the rural areas in the north of China and the southern areas where winter heating was needed.