土壤污染修复植物热处置及其重金属迁移转化规律研究

发布时间：2018-01-06 07:17

本文关键词：土壤污染修复植物热处置及其重金属迁移转化规律研究　出处：《东南大学》2017年博士论文　论文类型：学位论文

【摘要】：随着植物技术在土壤重金属污染修复中的广泛应用,修复后大量植物收获物的安全处置成为亟需解决的难题。修复植物热处置技术具有占地面积小、减容率高等优点,得到广泛关注。本文应用小试管式炉和中试流化床试验台对镉锌超积累植物伴矿景天进行焚烧和热解处置,研究了植物残体中重金属在热处置过程中的化学形态、在灰渣及细微颗粒中的分布特征,同时研究了热解产物生物油的成分及重金属浓度。在小试管式炉试验台上考察了农田和矿区伴矿景天焚烧过程中重金属的迁移规律,并结合最小Gibbs自由能计算方法研究了焚烧过程中重金属形态。结果表明,农田和矿区伴矿景天焚烧后大于99%重金属存在于飞灰与底渣中;温度升高增大了飞灰中重金属的回收率;矿区伴矿景天在高温焚烧时飞灰中重金属回收率高于农田伴矿景天;在还原性气氛下,硫和硫化物的存在抑制了重金属的挥发;而在氧化气氛下,重金属的挥发不受硫(S)、氯(Cl)、二氧化硅(SiO2)和三氧化二铝(Al2O3)的影响,锌(Zn)、镉(Cd)和铅(Pb)的主要化学形态是单质和氧化物。应用中试流化床试验台对农田伴矿景天进行焚烧试验研究,主要考察了温度与床料对伴矿景天植物焚烧过程中重金属迁移转化规律的影响;结果发现,底渣中Pb浓度随着温度升高而升高、而Zn却降低,Cd在底渣中浓度受温度影响较小;三种床料中,以凹凸棒土为床料时底渣中Zn和Pb回收率高,而以高铝矾土为床料时底渣中Cd的回收率最高;Zn主要是随未完全燃烧的生物质的夹带而离开炉膛,部分Pb被纤维状颗粒夹带离开炉膛、也有部分存在于不规则聚合体颗粒和KCl晶体中,Cd主要以挥发物离开炉膛;随着温度的降低,重金属与CaO和S等形成共晶熔融的颗粒,从而被除尘器捕捉;PM1、PM2.5和PM10颗粒的形成受床料类型和温度的影响较大,PM10中Zn浓度高,PM2.5具有较高浓度的Zn和Pb,PM1中Cd浓度高。建立了伴矿景天的流化床焚烧数学模型,应用欧拉-欧拉-化学反应方法对伴矿景天焚烧过程进行研究,模拟结果显示重金属的挥发主要发生于炉膛的中部,并随空气流动逸出炉膛。Cd在炉膛内的挥发率大于78%;而Pb和Zn的挥发率在823K时都很低,挥发率随着温度升高而升高。模拟值中重金属的挥发率高于试验值,但总体而言模拟研究可较好地表示重金属的挥发过程。在小试管式炉试验台研究了农田和矿区伴矿景天热解过程中重金属的迁移规律、热解产物及生物油成分。温度升高提高了气态产物的产率并促进了重金属向生物油的富集;与农田伴矿景天相比,矿区伴矿景天热解可获得更高的气态产物;Pb和Cd主要富集于生物油当中,而Zn主要存在于残炭当中;在450℃下进行热解,生物油的主要成分为酸类化合物,在650℃进行热解,烷烃的含量较高。采用流化床试验台对伴矿景天植物进行热解中试试验,结果表明,随着热解温度升高,热解炭的产率降低、热解气产率增加。生物油的产率在39.9～46.3wt%之间,于550℃时生物油的产率最高。热解过程中重金属主要存在于残炭,二级油的重金属浓度高于一级油,一级油中Cd浓度在为0.014～0.045 mg/kg,Pb浓度为0.14～0.53mg/kg,Zn浓度为53.6～142.2mg/kg。550℃条件下、以凹凸棒土为床料,在流化床内对伴矿景天进行热解,可获得产率高、品质好和重金属含量低的一级油,并可实现伴矿景天的资源化再利用。
[Abstract]:With the wide application of plant technology in the remediation of soils contaminated by heavy metals, after the restoration of the safe disposal of a large number of plant harvest is the problem to be solved urgently. Phytoremediation of heat treatment technology has a small footprint, the volume reduction rate is high, has received extensive attention. The trial application of tube furnace and pilot fluidized bed of cadmium and zinc super the accumulation of plant Sedum plumbizincicola of incineration and pyrolysis disposal, chemical speciation of heavy metals in plant residues in the heat treatment process of distribution in ash and fine particles in the study at the same time, composition and concentration of heavy metals of pyrolysis products of bio oil. In the small tube furnace was studied on the migration of farmland and the heavy metal mining Sedum plumbizincicola incineration process, combined with the minimum Gibbs free energy of heavy metals during the incineration of calculation method. The results showed that farmland and ore mining area with landscape After more than 99% days of burning heavy metals in fly ash and bottom ash; temperature increase the recovery rate of heavy metals in fly ash; mining Sedum plumbizincicola fly ash heavy metal recovery rate is higher than that of farmland plumbizincicola in high temperature incineration; under reducing atmosphere, sulfur and sulfide inhibit the volatilization of heavy metals; in the oxidizing atmosphere, heavy metal volatilization from sulfur (S), chlorine (Cl), silicon dioxide (SiO2) and three (Al2O3) of two aluminum oxide, zinc (Zn), cadmium (Cd) and lead (Pb) of the main chemical substances and oxides. The application form is in a fluidized bed Taiwan on the farmland plumbizincicola incineration experiment research, studied the influence of temperature and bed material migration of heavy metals during the incineration plant Sedum plumbizincicola; results showed that the concentration of Pb in slag increased as the temperature increased, while Zn decreased, Cd concentration in bottom ash was little affected by temperature; Three kinds of bed materials, by using attapulgite as recycled Zn and Pb when the bed bottom rate is high, while using bauxite as bed material when the bottom recovery rate of Cd in the highest; Zn is mainly with the entrainment of incomplete combustion of biomass and leaves the part of Pb is fibrous particle entrainment from the furnace also, some exist in irregular polymer particles and KCl crystal, Cd mainly in the volatiles from the furnace; with the decrease of temperature, heavy metal and CaO and S formation of granular eutectic melting, which is dust capture; PM1, affected by the bed material type and the temperature of the larger PM2.5 and PM10 particles the PM10 Zn PM2.5 with high concentration, high concentrations of Zn and Pb, PM1 in the high concentration of Cd fluidized bed incineration of Sedum plumbizincicola. Establishment of mathematical model by the Euler Euler method was used to study the chemical reaction of Sedum plumbizincicola incineration process, the simulation results show that the main volatile heavy metals In the middle, and with the air flow in the furnace hearth from.Cd volatilization rate greater than 78%; while Pb and Zn volatilization rate when 823K is low, the volatilization rate increased with increasing temperature. The simulated values of heavy metals in the evaporation rate is higher than the experimental values, but the overall simulation can be well expressed volatilization of heavy metals. The transfer law in small tube furnace of farmland and heavy metals plumbizincicola during pyrolysis, pyrolysis products and the composition of bio oil. The temperature increased with increasing gas yield and promote the enrichment of heavy metal to bio oil; compared with farmland plumbizincicola, mining Sedum plumbizincicola pyrolysis gaseous products can obtain higher; Pb and Cd are mainly enriched in the bio oil, and Zn mainly in residual carbon; pyrolysis under 450 degrees, the main components of the bio oil were acids, heat at 650 DEG C The solution, higher content of alkanes. The fluidized bed test, pyrolysis of Sedum plumbizincicola plants. The results showed that with the increase of temperature, reduce the carbon yield, increasing the pyrolysis gas yield. The yield of bio oil was 39.9 ~ 46.3wt%, 550 degrees of bio oil yield is highest. The pyrolysis process of heavy metals mainly exists in the carbon residue, heavy metal concentration is higher than a two grade oil level oil level in oil in the concentration of Cd is 0.014 ~ 0.045 mg/kg, the concentration of Pb was 0.14 ~ 0.53mg/kg, the concentration of Zn was 53.6 ~ 142.2mg/kg.550 deg.c, by using attapulgite as bed material, pyrolysis in a fluidized bed of Sedum plumbizincicola inside, can obtain high yield, good quality and low level of heavy metal content in oil, and can reuse the resources of Sedum plumbizincicola.

【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X53

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