Pd/activated carbon sorbents for mid-temperature capture of mercury from coal-derived fuel gas

Higher concentrations of Hg can be emitted from coal pyrolysis or gasification than from coal combustion, especially elemental Hg. Highly efficient Hg removal technology from coal-derived fuel gas is thus of great importance. Based on the very excellent Hg removal ability of Pd and the high adsorption abilities of activated carbon（AC） for H2 S and Hg, a series of Pd/AC sorbents was prepared by using pore volume impregnation, and their performance in capturing Hg and H2 S from coal-derived fuel gas was investigated using a laboratory-scale fixed-bed reactor. The effects of loading amount, reaction temperature and reaction atmosphere on Hg removal from coal-derived fuel gas were studied. The sorbents were characterized by N2 adsorption, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS）. The results indicated that the efficiency of Hg removal increased with the increasing of Pd loading amount, but the effective utilization rate of the active component Pd decreased significantly at the same time. High temperature had a negative influence on the Hg removal. The efficiency of Hg removal in the N2-H2S-H2-CO-Hg atmosphere（simulated coal gas） was higher than that in N2-H2S-Hg and N2-Hg atmospheres, which showed that H2 and CO, with their reducing capacity, could benefit promote the removal of Hg. The XPS results suggested that there were two different ways of capturing Hg over sorbents in N2-H2S-Hg and N2-Hg atmospheres.     

树脂基固态胺吸附剂室温下对低浓度CO2的吸附性能研究

以大孔甲基丙烯酸酯吸附树脂为载体,聚乙烯亚胺(PEI)为有机胺,采用液相浸渍法制备出固态胺吸附剂,并研究了其在室温下对低浓度CO2的吸附行为.同时,利用氮气吸附、热重分析和扫描电镜表征了材料的物理化学性质,并采用热重法和固定床吸附法考察了材料的CO2吸附性能.结果表明,大孔树脂担载50%PEI(质量分数)时吸附性能最佳,对纯CO2的最大吸附量为175 mg·g-1;CO2的吸附行为由扩散动力学与吸附热力学共同决定,低温有利于提高吸附容量;吸附剂对400 ppm~15%浓度的CO2都具有优异的动态吸附性能,其中对400 ppm CO2的吸附量达到86 mg·g-1,对15%CO2的吸附量达到150 mg·g-1;湿度对吸附起促进作用,相对湿度为10%时,对400 ppm CO2的吸附量提高至139mg·g-1;吸附剂具有优异的循环性能,具有直接空气捕集CO2的潜力.     

用于干式脱污的CaO蒸汽活化实验研究

利用小型活化转炉实验台对以CaO为主要成分的钙基脱污剂在300～650℃的温度范围内进行蒸汽活化处理,结合X射线衍射和压汞仪的分析结果,初步探讨了蒸汽活化的机理.研究表明,蒸汽活化温度在600℃以上时,脱污剂孔隙结构有显著的改善,比孔容积和比表面积有着显著的增加,微孔(＜100nm)的数量大量增加,而低温下蒸汽活化的效果不是十分明显;研究还发现高温下延长活化时间有利于改善脱污剂的孔隙结构.     

Treatment of tunnel wash waters – experiments with organic sorbent materials. Part II: Removal of toxic metals

In the first part of the article, the column and the bag experiments concerning removal of polycyclic aromatic hydrocarbons (PAHs) and nonpolar oil (NPO) from tunnel wash waters using organic sorbent materials have been described. This part presents the results of removal of toxic metals. The metals of concern (Al, As, Cd, Cr, Cu, Fe, Pb, Mo, Ni, and Zn) were selected based on the priority toxicant pollutants defined in surface water quality criteria. Concentrations of these metals in the collected effluent...     

固态合成粉煤灰类脱硫吸附剂的脱硫活性测试

固态合成的粉煤灰吸附剂的脱硫活性测试结果表明 ,30 0℃得到的无定形硅铝钠高效脱硫剂 (FA NSA)在 5 0 0℃的脱硫温度下 ,穿透和饱和硫容分别为 64 6mg·g- 1 和 1 34 0mg·g- 1 ;穿透和饱和效率分别为 46 3%和 96 2 % .     

Sorbents with high efficiency for CO2 capture based on amines-supported carbon for biogas upgrading

Sorbents for CO_2 capture have been prepared by wet impregnation of a commercial active carbon(Ketjen-black, Akzo Nobel) with two CO_2-philic compounds, polyethylenimine(PEI)and tetraethylenepentamine(TEPA), respectively. The effects of amine amount(from 10 to70 wt.%), CO_2 concentration in the feed, sorption temperature and gas hourly space velocity on the CO_2 capture performance have been investigated. The sorption capacity has been evaluated using the breakthrough method, with a fixed bed reactor equipped with on line gas chromatograph. The samples have been characterized by N_2 adsorption–desorption,scanning electron microscopy and energy dispersive X-ray(SEM/EDX). A promising CO_2 sorption capacity of 6.90 mmol/gsorbenthas been obtained with 70 wt.% of supported TEPA at 70℃ under a stream containing 80 vol% of CO_2. Sorption tests, carried out with simulated biogas compositions(CH_4/CO_2mixtures), have revealed an appreciable CO_2 separation selectivity; stable performance was maintained for 20 adsorption–desorption cycles.     

Natural and waste materials as metal sorbents in permeable reactive barriers (PRBs)

A range of waste products and natural materials including chitin, fly ash, clay soil, cocoa shell, calcified seaweed and the natural zeolite clinoptilolite were tested in batch experiments to assess their ability to remove metals from a synthetic groundwater containing 10 mg l^–1 Cu, Pb and Zn and 1 mg l^–1 Cd. All had the ability to remove more than 70% of the metals from solution with fly ash being the most efficient, then chitin, clinoptilolite, calcified seaweed, clay soil and cocoa shell. After consideration of geochemical and morphological properties, calcified seaweed and clinoptilolite were shown to have potential as barrier materials. Given current issues with regard to the longevity of zero-valent iron barriers alternative materials could be the key to the future adoption of this remediation technology.     

固定床PVC燃烧脱氯的机理和试验

研究垃圾组分PVC在焚烧过程中HCl的排放和脱除特性的实验在准等温、电加热的水平石英管反应器中进行.随着床温从700℃升高到900℃,HCl的转化率从82.5%平缓增加到88.3%,而过量空气系数的增加促使部分HCl转化为C1₂(1.9%～4.5%)的形式存在.钙基吸收剂CaCO₃,Ca(OH)₂,Ca(CH₃COO)₂对HCl的脱除效率高达68%～79%,而镁基吸收剂的脱氯效率却低于3%.小的吸收剂粒径、高的Ca/Cl比会促进脱氯效率的提高;烟气中CO₂和H₂O对脱氯效率的影响与它们在反应平衡中所起作用有关.高温下燃烧固氯机理反应的平衡常数的计算不仅诠释了实验结果,而且提供了脱氯吸收剂选择的依据.     

The influence of the precursor and synthesis method on the CO2 capture capacity of carpet waste-based sorbents

Adsorption is one of the most promising technologies for reducing CO₂ emissions and at present several different types of sorbents are being investigated. The use of sorbents obtained from low-cost and abundant precursors (i.e. solid wastes) appears an attractive strategy to adopt because it will contribute to a reduction not only in operational costs but also in the amount of waste that is dumped and burned in landfills every year. Following on from previous studies by the authors, in this work several carbon-based adsorbents were developed from different carpet wastes (pre-consumer and post-consumer wastes) by chemical activation with KOH at various activation temperatures (600–900 °C) and KOH:char impregnation ratios (0.5:1 to 4:1). The prepared materials were characterised by chemical analysis and gas adsorption (N₂, −196 °C; CO₂, 0 °C), and tested for CO₂ adsorption at temperatures of 25 and 100 °C. It was found that both the type of precursor and the conditions of activation (i.e. impregnation ratios, and activation temperatures), had a huge influence on the microporosity of the resultant samples and their CO₂ capture capacities. The carbon-based adsorbent that presented the maximum CO₂ capture capacities at 25 and 100 °C (13.8 wt.% and 3.1 wt.%, respectively), was prepared from a pre-consumer carpet waste and was activated at 700 °C using a KOH:char impregnation ratio of 1:1. This sample showed the highest narrow microporosity volume (0.47 cm³ g⁻¹), thus confirming that only pores of less than 1 nm are effective for CO₂ adsorption at atmospheric pressure.