【作者】 董洁；

【导师】 谢克昌； 李凡；

【作者基本信息】 太原理工大学 ， 化学工程与技术， 2013， 博士

【摘要】 煤加工利用过程中排放的有机污染物特别是多环芳烃(PAHs)类物质,由于其具有“三致”作用,且是PM2.5的主要承载物,易引发雾霾天气,对生态环境造成了潜在危害,因此其生成、迁移及控制过程受到人们的关注,也越来越引起国内外各政府及环保部门的高度重视。煤的热解是煤热加工必不可少的过程,也是煤清洁利用的基础。因此本课题对煤热解过程中PAHs排放规律及裂解特性进行研究,为煤热加工过程中污染物的控制和煤的清洁利用提供理论依据。研究选取了15种具有代表性的不同变质程度的煤样,首先利用液固萃取方式得到煤中可溶于二氯甲烷的PAHs(作为自由态PAHs,简称为自由PAHs)及其残煤,利用GC-MS对自由PAHs进行分析,并利用对同一个样品可进行多段程序升温的PY-GC-MS分别对其他不同来源(原煤热解PAHs、抽提物热解PAHs、残煤热解PAHs)的16种需优先控制的PAHs进行全面系统的研究,此外还在线研究了廉价易得金属氧化物对煤热解产物中PAHs排放规律的影响。主要内容如下：(1)利用Gerhardt Soxtherm macro414抽提仪对原煤中PAHs进行二氯甲烷抽提,针对原煤中PAHs的萃取,建立了一整套完整的方法。该方法具有抽提效率高、省时、溶剂回收率高、环保的特点。(2)研究了原煤中16种PAHs的分布与原煤煤质指标的关系以及PAHs毒性当量的分布,结果表明：不同变质程度原煤中的自由PAHs都主要以4、5环为主,但烟煤中16种PAHs的种类和数量最多,导致烟煤的TEQ浓度最高,更容易对环境产生污染。(3)研究了原煤快速热解过程中PAHs的生成及其分布规律,结果表明：2-3环的PAHs在原煤热解产物中的比重最大,煤的变质程度对煤热解过程中PAHs的排放量及排放种类有显著的影响,炼焦用烟煤热解时生成的PAHs量最多,且TEQ浓度高；煤热解过程中PAHs的生成量随温度的升高有先增后减的趋势,热解终温相同时,升温速率越高,PAHs的生成量越少。(4)通过对比分析原煤中可抽提的自由PAHs、原煤及其抽提液和残煤热解过程中的PAHs生成量之间的差异,对煤热解过程中16种PAHs的来源进行探讨,结果表明：16种PAHs主要来源于煤热解过程中复杂的化学反应,而非原煤中自由态的PAHs;高环(5-6环)PAHs在一定温度下更易分解；在不同变质程度煤生成的PAHs总量中2、3环所占比例最大。大分子网状结构的断裂和自由基的缩合是煤热解过程中PAHs生成的主要原因。(5)通过对比分析平朔(PS)原煤抽提物及其热解产物的组成,对PAHs的前驱物进行探讨,结果表明：PS原煤抽提物的主要组成是芳烃类化合物,共占总萃取物的70.87%。芳烃类化合物主要包含EPA优先控制的16种PAHs及其烷基化和异构化衍生物,热解过程中,芳烃衍生物生成了小环PAHs,是小环PAHs的前驱体。(6)研究了两种廉价易得金属氧化物(CaO、Fe2O3)在不同温度下对煤热解产物中16种PAHs的催化裂解作用。结果表明：两种金属氧化物都对16种PAHs有催化裂解作用,但发生催化裂解作用的最佳温度不同,其中Fe203在600℃时对16种PAHs的催化裂解效果最好,而CaO催化裂解作用的最佳温度为700℃。更多还原

【Abstract】 Polycyclic Aromatic Hydrocarbons (PAHs) from the coal conversion have attracted increasing attention due to carcinogenicity, teratogenicity, and mutagenicity which affect human’s health and environment when they were released into the environment. Pyrolysis as the starting step plays a key role in coal thermal conversions, where include combustion, gasification and liquefaction, and especially for coking which is a pyrolysis process entirely. Research on the formation, emission and catalytic cracking property of PAHs during coal pyrolysis has significant effect on pollutants control and clean coal utilization at present and in the futureGerhardt Soxtherm macro414Soxhlet was used to fully extract the PAHs from15kinds of Chinese raw coals different in rank by the CH2C12, GC-MS was used to analyze the free PAHs extracted from raw coals and PY (Pyro-probe CDS5250)-GC-MS was used to online pyrolysis analysis of the raw coals, their extraction residues and extracts respectively. The influence of alkaline metal oxides which are inexpensive and easily available on the PAHs catalytic cracking was also investigated. Main contents as follow:(1) The Gerhardt Soxtherm macro414was used to extract the PAHs from raw coals by dichloromethane, a complete method for the extraction and analysis of PAHs from raw coals was established. The method has the characters of high extraction efficiency, time saving, high solvent recovery, high sensitivity and environmental protection.(2) The relationship between the distribution of free PAHs in raw coals and coals properties were studied, and the PAHs Toxicity Equivalent (TEQ) was also mentioned. The results showed that the properties of raw coals have significant effect on the distribution of free PAHs; The free PAHs in the raw coals were mainly dominated by4,5-ring PAHs, and bituminous coal has the highest concentration of TEQ, which may pollute the environment more easily;(3) PAHs emitted from15kinds of Chinese coals different in rank during pyrolysis were studied. The results suggest that the lower-ring (2,3-rings) PAHs prevailed over the higher-ring PAHs during the coals pyrolysis; the amounts and species of PAHs under the same conditons of coal pyrolysis depend on coal properties; Temperature has significant effect on the distribution of PAHs from coal pyrolysis and the emission amount of PAHs showed a single peak at800℃with increasing temperature. The emission amount of PAHs decrease with increasing heating rate at the same pyrolysis temperature.(4) The source of the PAHs from coal pyrolysis is discussed by comparing the difference among the amounts and species of the PAHs from the pyrolysis of raw coals, their extraction residues and extracts, the free PAHs from raw coals. The main conclusions are as follows:the16PAHs mainly came from complex chemical reactions of coal pyrolysis rather than from the free PAHs in the raw coals; the higher-ring (5,6-ring) PAHs were prone to decompose at certain temperature; NaP was formed by the reaction of coal pyrolysis, and the increase of the total PAHs was mainly the contribution of the2,3-ring PAHs; The breakdown of the macromolecular network and the free radicals condensation reaction were the main causes which gave rise to the forming of PAHs in the coal pyrolysis.(5) The precursors of PAHs was studied by comparing the omposition of PS coal extract and its extract pyrolysis. The results indicated that the extract of PS raw coal is mainly composed of aromatic compounds which accounted for70.87wt%of the total extract. Aromatic compounds mainly contains16PAHs and their derivatives of isomerization and alkylation, part of the derivatives which generate low-ring PAHs during the pyrolysis are the precursor of a small ring PAHs.(6) The effect of calcium oxide(CaO) and iron oxide(Fe2O3) on the16PAHs emitted from the coal pyrolysis were analyzed under different operation conditions including temperature, quality and partical size of catalyst. The results showed that the leading effect factor of CaO and Fe2O3on catalytic action of PAHs decomposition was temperature; at600℃, Fe2O3had the best catalytic cracking effect to16PAHs; while under the CaO catalytic cracking effect, the best temperature is700℃.更多还原