An Experimental Study on Oxidized Mercury Adsorption by Bromide Blended Coal Combustion Fly Ash

The application of forced mercury oxidation technology would lead to an increase of Hg^(2+)concentration in the flue gas.Although Hg^(2+)can be easily removed in the WFGD,the mercury re-emission in the WFGD can decrease the total removal of mercury from coal-fired power plants.Hence,it is necessary to control Hg^(2+)concentration in the devices before the WFGD.Fly ash adsorbent is considered as a potential alternative for commercial activated carbon adsorbent.However,the adsorption efficiency of the original fly ash is low.Modification procedure is needed to enhance the adsorption performance.In this study,the adsorption of Hg^(2+)by brominated fly ash was studied.The fly ash was collected from the full-scale power plant utilizing bromide-blended coal combustion technology.The brominated fly ash exhibited excellent performance for Hg^(2+)removal.The flue gas component HBr and SO_(2)could improve adsorbent’s performance,while HCl would hinder its adsorption process.Also,it was demonstrated by Hg-TPD experiments that the adsorbed Hg^(2+)mainly existed on the fly ash surface in the form of HgBr_(2).In summary,the brominated fly ash has a broad application prospect for mercury control.

A critical review on lead migration, transformation and emission control in Chinese coal-fired power plants

Coal is widely utilized as an important energy source,but coal-fired power plant was considered to be an important anthropogenic lead emission source.In the present study,the distribution characteristics of lead in coal and combustion by-products are reviewed.Specifically,lead is mainly transferred to ash particles and the formation and migration mechanisms of particulate lead are summarized.Also,targeted measures are proposed to control the formation of fine particulate lead as well as to increase the removal efficiency during the low-temperature flue gas clean process.In detail,interactions between gaseous lead and some coal-bearing minerals or added adsorbents could obviously suppress the formation of fine particulate lead.On the other hand,some efforts(including promoting capture of fine particles,reducing resistivity of particles and strengthening the gas-liquid contact)could be made to improve the fine particulate lead removal capacity.Notably,the formation mechanism of fine particulate lead is still unclear due to the limitations of research methods.Some differences in the removal principles of fine particles and particulate lead make the lead emission precisely control a great challenge.Finally,the environmental potential risk of lead emission from flue gas and ash residues is addressed and further discussed.

Effect of semi-continuous water washing on the combustion behaviors of agricultural organic solid waste

Combustion of agricultural organic solid waste(AOSW)was an ideal solution for their resource utilization in view of their massive annual production and great potential for reduction of fossil fuel utilization.However,high alkali and alkaline earth metals(AAEMs)content in the feedstock can arose severe fouling and slagging issues and thus prohibiting its vast utilization.In this study,a semi-continuous water washing method was proposed to preliminarily remove AAEMs from agricultural organic solid waste and its effects on the combustion behaviors of washed solid product were investigated.Results showed that the combustion index S were improved to 2.63×10-6,over 68%of the total ashes were removed from the cotton stalk,and 96.3%,89.0%and 74.7%of K,Na and Mg were effectively removed,respectively.Moreover,the softening temperature of low temperature ash from the washed sample was as high as 1450◦C,538◦C higher than the low temperature ash from the original sample;the base acid ratio and fouling index were improved from high slagging and fouling risk(1.7 and 90.8)of the original organic solid waste to low and medium risk(0.4 and 3.5),respectively.All these results signified the contributing effect of proposed semi-continuous water washing method on the combustion of agricultural organic solid waste.In a word,this study provided a promising method for fouling and slagging inhibition during the agricultural organic solid waste combustion.

Characteristics of gas-solid micro fluidized beds for thermochemical reaction analysis

Fuel conversion and clean energy reaction systems involve a variety of catalytic and non-catalytic gas-solid thermochemical reactions.A good understanding of the correct reaction mechanism and kinetics,as well as the profiles of reaction products,is of great significance to the development,design,and operation of such reaction systems.The micro fluidized bed reaction analysis provides an efficient and reliable method to acquire this essential information with low capital and operating costs,low energy consumption and enhanced safety.This paper provides an overview of the system and its characteristics for the micro fluidized bed reaction analyzer that has been well proven to be a reliable new approach as well as an instrument for characterizing various gas-solid thermochemical reactions.

Degradative solvent extraction of low-rank coal:Role of water on pyrolysis mechanism of low-rank coal in a highly-dispersed medium

A degradative solvent extraction(DSE)method was proposed to upgrade low-rank coals(LRC)for their cascaded utilizations in a highly-dispersed medium.The derived products exhibited well improved properties in comparison to the raw LRCs.Previously,the LRCs were pre-dried to eliminate the potential impact of the varied water content of raw LRCs,but in light of the abundant water in fresh coals,the hydrolyzing effect of water on coals under heating,and the energy cost to pre-dry the LRCs,it is consequently essential to clarify the effect of water so as to verify the necessity of pre-drying process.In this study,the roles of inherent water and extra-added water were respectively investigated,using dried,raw and wet coals from two typical LRCs.The results show that increasing the moisture content of raw LRCs contributed to the extraction ability of DSE method without noticeably changing the elemental composition,chemical structure and thermal decomposition behavior of extractable products,thus pre-drying of LRCs before DSE treatment was proven unnecessary.Additionally,the roles of the inherent water were concluded as:1)leading to the formation of stable covalent bond during drying process;and 2)acting as H donor to promote extraction ability,while the added water can only function as H donor.Since excessive water will increase the pressure during DSE treatment and lead to the waste water treatment,the LRCs with a water content between 10%and 30%were consequently recommended for the practical application of DSE treatment.