Numerical Study on the Homogeneous Reactions of Mercury in a 600 MW Coal-Fired Utility Boiler

The homogeneous oxidation of elemental mercury (Hg0) can promote Hg pollution control in coal-fired power plants, while the mechanisms and quantitative contributions of homogeneous reactions in Hg0 oxidation, especially the reactions between Hg and chlorine (Cl), are still unclear. Here, a numerical study on the homogeneous reactions of Hg was conducted within a 600 MW tangentially fired boiler for the first time. A novel Hg sub-model was established by coupling the thermodynamics, reaction kinetics and fluid dynamics. The results showed that the higher Cl content in coal was beneficial to the oxidation of Hg0. The homogeneous reactions of Hg mainly occurred in the vertical flue pass at low temperature. Hg0 was still the dominant Hg-containing species at the boiler exit, and the concentration of mercury chloride (HgCl2) was the highest among the oxidized mercury. When low-Cl coal was fired, the addition of a small amount of chlorine species into the boiler at the burnout area increased the ratio of HgCl2 by over 16 times without causing serious chlorine corrosion problems.

Thermal slip and homogeneous/heterogeneous reaction characteristics of second-grade fluid flow over an exponentially stretching sheet

This paper deals with an unsteady magnetohydrodynamic two-dimensional second-grade fluid flow towards a permeable exponentially stretching surface with heterogeneous–homogeneous reactions. The nonuniform heat source/sink, thermal slip, and thermal radiation effect are also considered to analyze the thermal attributes. The modeled equations of motions are converted into nonlinear ordinary differential equations (ODEs) by suitable transformations. A MATLAB Bvp4c approach is employed for the numerical solution of ODEs. The outcomes of various parameters are scrutinized by graphs. The quantities of interests such as Nusselt number and the skin friction are presented and discussed. The resistance effects take place due to higher estimations of second-grade parameter, as a result, the velocity field declines. The temperature field raises with the increment of radiation parameter. The concentration of nanoparticles decaying when heterogeneous-homogeneous reactions become larger. Moreover, from the tabulated data, it is noticed the growing estimations of K and M boosts the coefficient of skin friction.

When Attempting Chain Extension, Even Without Solvent, It Is Not Possible to Avoid Chojnowski Metathesis Giving D3

A simple, mild and efficient method to prepare HSi- or HOSi-telechelic, high-molecular-weight polydimethylsiloxane polymers (to 41,600 g·mol−1) using the one-shot hydrolysis of MHMH is reported; titration of the water allowed for higher molecular weights (to 153,900 g·mol−1). The “living” character of the chain extension processes was demonstrated by adding a small portion of MHMH and B(C6F5)3 (BCF) to a first formed polymer, which led to a ~2-fold, second growth in molecular weight. The heterogeneous reaction reached completion in less than 30 min, much less in some cases, regardless of whether it was performed neat or 50 wt% in dry toluene; homogeneous reactions in toluene were much slower. The process does not involve traditional redistribution, as judged by the low quantities (<3%) of D4 produced. However, it is not possible to avoid Chojnowski metathesis from MHDDMH giving D3, which occurs competitively with chain extension.