Experimental study on the stability of the ClHgSO3- in desulfurization wastewater.

Wet flue gas desulfurization technologies have received much concern for their superior performance on co-controlling the acid gases and mercury. However, high concentrations of mercury-containing desulfurization wastewater, which discharge from wet flue gas desulfurization system regularly, have received researchers' attention since it might generate the risk of secondary pollution. In this paper, the species of mercuric complexes in the desulfurization wastewater was investigated. It speculated that ClHgSO3- might determine the residual rate of Hg2+ in the desulfurization wastewater. Besides, the stability of ClHgSO3- on the condition of various wastewater features was also evaluated. The experiment revealed that the high temperature and high pH level promoted the decomposition of ClHgSO3-. SO32- could restrain the decomposition of ClHgSO3- gently; the Hg2+ residual rate was determined by the new mercury complexes which compounded by Hg2+ and SO32-. The decrease of SO42- and increase of Ca2+ concentrations could also stimulate the stability of ClHgSO3- in wastewater. Cu2+ and Fe2+ disturbed the stability of complexes for their catalysis and reduction activities. The study proposed that the ClHgSO3- probably decomposes and releases Hg0 in two pathways. Furthermore, changes of the water's features could disturb the balance of Hg2+-Cl--SO32- systems, which might stimulate the decomposition of ClHgSO3.

Agglomeration rate and action forces between atomized particles of agglomerator and inhaled-particles from coal combustion.

In order to remove efficiently haled-particles emissions from coal combustions, a new way was used to put forward the process of agglomeration and the atomization was produced by the nozzle and then sprayed into the flue before precipitation devices of power station boiler in order to make inhaled-particles agglomerate into bigger particles, which can be easily removed but not change existing running conditions of boiler. According to this idea, a model is set up to study agglomeration rate and effect forces between fly ash inhaled-particles and atomized agglomerator particles. The developed agglomeration rate was expressed by relative particle number decreasing speed per unit volume. The result showed that viscosity force and flow resistance force give main influences on agglomeration effect of inhaled-particles, while springiness force and gravity have little effect on agglomeration effect of theirs. Factors influencing the agglomeration rate and effect forces are studied, including agglomerator concentration, agglomerator flux and agglomerator density, atomized-particles diameters and inhaled-particles diameter and so on.

[Determination of trace mercury in coal by microwave digestion and cold vapor atomic fluorescence spectrometry].

A method of determining trace Hg in coal by microwave digestion and cold vapor atomic fluorescence spectrometry is reported. The digestion system of HNO3-HCl-HF was evaluated. The experimental conditions of microwave digestion, including pressure, temperature, power and time of digestion were evaluated. The operating conditions such as flow rate of carrier gas, flow rate of shield gas and negative high voltage, and interference were also investigated. Testing results show that the detection limit is 0.03 ng x mL(-1) and RSD (n = 7) is below 5%. This method is simple and rapid. The treatment method was applicable to determining trace Hg in coal and gave results that were in good agreement with the certified values of the standard reference material.

[Determination of trace selenium in coal by microwave digestion and hydride generation ICP-AES].

A method for determining trace Se in coal by microwave digestion and hydride generation ICP-AES is reported. The digestion system of HNO3-HCl-HF was evaluated. The hydride generation occurred in 3 mol x L(-1) hydrochloric acid media with 1% sodium tetrahydroborate as a reduction reagent. The experimental conditions of microwave digestion, prereduction, and interferences were investigated. This method is simple and rapid. The treatment method was applicable to Se and gave results that were in good agreement with the certified values of the standard reference material. Testing results showed that the detection limit was 0.3 microg x L(-1) and RSD was below 5%.

[Experimental study on emission characteristics of PM10 in coal-fired boilers].

Fly ash was sampled at the inlet and outlet of ash collectors in four different coal-fired utility boilers using 13-stage low pressure impactor (LPI). The mass distribution, emission characteristics and the composition at different size particle of PM10 were studied. The results show that PM10 of the four boilers have a similar himodal distribution, with two peaks formed around 0.1 microm and 2.36 - 3.95 microm, respectively. The lowest efficiency of ash collectors was between 50% - 65% when the particle sizes were around 0.1 - 1 microm, no matter Venturi water membrane dust collector or ESP was used. Ash collectors show different removal efficiencies to various particle sizes PM. The removal efficiency of ash collectors was about 96% around 10 microm, while under 1 microm it was between 62% - 83%. The chemical composition of the size-segregated ash showed that the element S and Na were obvious enrichment in finer ash, which is possibly formed via vaporization and subsequent condensation of inorganic matter. While the refractory oxides were the major composition in bigger size ash, which may be formed via char fragmentation, excluded mineral fragmentation and included mineral coalescence.

[Characterization of arsenic emissions from a coal-fired power plant].

An emissions study for arsenic was conducted at a 300 MW coal-fired plant equipped with an electrostatic precipitator. The input and output streams such as coal, slag, ESP ash, and flue gas containing the post-ESP particulates were collected. Gaseous arsenic was sampled using EPA method 29 and the arsenic concentrations in the samples were measured using inductively coupled plasma atomic emission spectrometry (HG-ICP-AES). The mass balance recovery of arsenic estimated in this study was 87.2%. Arsenic concentration in stack gas was 2.5 microg/m3. Approximately 0.53% of the coal-derived arsenic was incorporated into slag, 84.6% of the arsenic was found on the fly ash collected by electrostatic precipitators, and 2.16% was found in the vapor phase. The relationship between arsenic concentration and ash particle size was also assessed, and arsenic is significantly concentrated in the small sized particles.