PVC燃烧时HCI的释放规律

火灾中PVC燃烧后会产生大量HCl气体，危及人的生命安全。利用火灾烟气发生装置和红外傅立叶变换气体分析仪（FTIR）对PVC热解和燃烧时产生的烟气中的HCl气体浓度进行了实时在线的定量分析，结果表明PVC在受热升温后的热解阶段就会释放出大部分HCl气体，使得烟气毒性达到峰值。对于PVC燃烧产生的火灾，其烟气毒性最大工况发生在火焰出现之前。     

Al(OH)3和Mg(OH)2对PVC热解特性的影响研究

利用热重分析仪并借助电导率测定法探讨了Al(OH)3和Mg(OH)2对PVC热解特性的影响,简要分析了其机理。结果表明:加入Al(OH)3和Mg(OH)2后均能增加PVC体系在第一阶段的最大热解速率和残炭量,最大热解速率增加约1倍,残炭量增加约4倍。并且分解产生的结晶水吸收大量的热量,惰性金属氧化物也有利于成核、炭层生长和凝聚,有着明显的阻燃和抑烟作用。HCl毒性气体的释放主要集中在体系的第一阶段,Al(OH)3能促使HCl提前释放,HCl的释放总量增加,Mg(OH)2也能促使HCl提前释放,但HCl的释放总量却是减少的。     

城市生活垃圾焚烧体系化学热力学平衡分析

采用化学热力学平衡分析方法，分析城市生活垃圾焚烧体系污染物的排放特性。主要计算了聚氯乙烯（PVC）及典型城市垃圾焚烧过程氯元素的化学平衡组成及其浓度，同时研究了脱氯剂对PVC及垃圾中氯转化的影响。计算结果表明，PVC热态反应的主要产物是HCl气体，在加入脱氯剂后温度低于600℃时，脱氯剂对HCl的脱除作用很明显；城市生活垃圾热解和燃烧过程中在温度超过600 ℃，垃圾中的有机氯和无机氯都将转化为HCl气体，而此时脱氯剂失去效果。由计算结果得到控制HCl生成，消除二口恶英污染物的生成反应工艺条件。     

PVC的热解/红外(Py/FTIR)研究

采用热解／红外联用仪（Py/FTIR)考察了PVC的热解过程，结果表明，PVC在200℃时开始放出HCl,300℃左右达到最大，在红外谱图上HCl气体的振－转吸收区是3100cm^-1～2600cm^-1，有P支和R支出现；随后－CH2－基在2860cm^-1和2930cm^-1处的吸收明显增强，可认为是生成的多烯碎片进一步裂解生成脂肪族化合物的结果；同时有芳烃在1620cm^-1、3010cm^-1和900cm^-1～600cm^-1处的吸收出现。这是由于除了部分多烯碎片规则断裂形成酯肪烃类物质的挥发分外，还有一部分通过分子重排、环化形成芳烃结构，其中的一部分以芳烃类物质进入挥发分，另一部分聚合形成稠环芳香族物质，最后变成焦粒。通过上述研究，提出了PVC的热解机理，即PVC首先脱出HCl气体，进一步热解产生多烯结构，并通过分子重排、环化形成芳烃结构。     

城市生活垃圾与煤矸石混烧特性及其HCl排放特性研究

利用热重分析仪对城市生活垃圾与煤矸石单独及混合燃烧特性进行了研究,并采用高温管式炉燃烧装置考察了PVC、NaCl及MSW与煤矸石混烧过程中HCl的排放规律。结果表明,在煤矸石中掺烧部分MSW可有效改善煤矸石的燃烧特性,尤其是脱挥发分和着火特性。综合考虑燃烧特性变化,建议MSW掺混比例为20%。PVC与NaCl掺混比较低时,煤矸石可抑制PVC燃烧过程中HCl的析出,会显著促进NaCl中HCl的析出;当掺混比增大时,上述作用逐渐减弱。MSW与煤矸石混烧时,会促进HCl的析出,增大烟气中HCl的浓度。当掺混比为10%时,HCl排放浓度达到56.22 mg/m~3,已超过中国国家标准,必须采取相应脱氯措施。     

PVC热解动力学的研究

PVC作为城市固体废弃物中的重要组分,国内外学者已对它的热解或燃烧动力学模型进行了一些研究。Danforth和Takeuchi根据链式理论研究了PVC在220－240℃的热解动力学^[1],Troiskii和Troiskaya提出了用来描述PVC分解初始阶段（转化率约10％以内）HCl析出的数学模型^[2];Wu等分别研究了PVC在高转化率（＞60％）时及在127℃-427℃范围内的热解动力学^[3,4];上述研究主要集中于某一确定的转化范围,而国内近年才开始对PVC的热解或燃烧动力学进行研究,一般都采用较简单的一次反应方程^[5]或常见的固体反应方程6[6]来求解动力学参数,为了能较好地拟合实验结果,计算中只能分段拟合,这样不可避免地会出现断点,所以,对PVC热解动力学的研究还缺乏完整性或连续性,不便于应用。     

以高聚物为载体的汽油燃烧烟气的便携式红外分析

利用便携式红外气体分析仪,系统地对不同高聚物及以不同高聚物为载体的汽油燃烧初期烟气进行在线分析,寻找出烟气的主要成分及变化规律,为火灾原因鉴定提供技术支持。通过对火场初期产生的烟气进行在线分析,初步确定了其中的有毒有害气体种类。     

高挥发分烟煤的热解、燃烧特性研究

采用固定床热解反应器、热解 红外联用仪 (Py FTIR)和热重分析仪 ,考察了高挥发分烟煤的热解、燃烧特性 ,实验结果表明 ,高挥发分烟煤在热解过程中放出大量烃类气体 ,从燃烧试验看 ,明显分为热解段和燃烧段 ,且热解段挥发分的释放非常迅速 ,从而揭示出高挥发分烟煤燃烧过程中产生大量黑烟的原因。     

预脱氯处理PVC残渣和平朔煤共热解的协同效应研究

热解是煤炭清洁高效利用的有效途径,也是处理废旧塑料高效转化的重要方式。本文针对无害化处理困难的含氯塑料,以聚氯乙烯(PVC)和平朔煤为研究对象,提出将PVC先经预热处理脱除大部分氯,然后将预处理后的PVC残渣与煤进行共热解,并利用气相色谱(GC)、模拟蒸馏、GC-MS、元素分析、红外光谱及拉曼光谱等对热解产生的气体、焦油以及半焦的组成和性质进行分析表征。结果表明,预脱氯处理后的PVC和平朔煤的共热解过程存在协同效应,共热解对半焦和焦油的形成具有明显的正协同作用,焦油产率实验值比理论计算值最大高3.35%;而对热解水和气体的形成产生负协同作用,其中,CH_4产率下降最多,即出现最强的负协同效应;共热解使焦油中轻质焦油含量提高,其中,萘类物质含量显著增加,沥青减少,当预脱氯处理PVC添加量为10%时,轻质焦油含量比理论计算值提高5个百分点。此外,共热解半焦表面更为光滑,结构变得更加有序,石墨化度提高。     

基于锥形量热仪试验的聚合物材料火灾危险评价研究

简述了锥形量热仪的试验原理,以聚合物材料锥形量热仪试验数据为基础,导出了火势增长指数（FGI）、放热指数（THRI6min）、发烟指数（TSPI6min）和毒性气体生成速率指数（ToxGI）4个评价聚合物材料火灾危险的参数,并利用这四个参数对ABS、PS、PVC、PA 4类16种商用塑料样品的火灾危险性逐项进行了分析评价.在此基础上,采用层次分析法的原理对样品的火灾危险进行了综合评价,结果表明,ABS、PS、PVC、PA四类样品的火灾综合危险依次减小.     

Thermal and burning properties of wood flour-poly(vinyl chloride) composite

The present study deals with the effects of wood flour on thermal and burning properties of wood flour-poly(vinyl chloride) composites (WF-PVC) using thermogravimetric (TG), cone calorimetry (CONE), and pyrolysis?Cgas chromatography/mass spectrometry (Py?CGC/MS). TG tests show that an interaction occurred between wood flour and PVC during the thermal degradation of WF-PVC. Wood flour decreased the temperature of onset of decomposition of PVC. However, the char formation could be increased by adding wood flour to PVC. CONE test indicates that wood flour had positive effects on heat release and smoke emission of PVC. Comparing with PVC, WF-PVC reduced average heat release rate and the peak HRR by about 14 and 28%, respectively; smoke production rate was also decreased. The degradation mechanism was studied by Py?CGC/MS. The results show that the volatile pyrolysis products of WF-PVC are very different from PVC. The yields of HCl and aromatic compounds decreased dramatically, and the aliphatic compounds increased by the incorporation of WF.     

Factors affecting the combustion toxicity of polymeric materials

Fire gas toxicity is an essential component of any fire hazard analysis. However, fire toxicity, like flammability, is both scenario and material dependent. A number of different methods exist to assess the fire toxicity, but many of them fail to relate this to a particular fire scenario. Sample thickness alone, in a closed box test such as the NBS Smoke Chamber, is shown to change the fire scenario from well-ventilated to under-ventilated. Data from two flow-through tests, the static tube furnace (NF X 70-100) and the steady state tube furnace (the Purser furnace, BS 7990 and ISO TS 19700) show that there are different patterns of behaviour for different polymers (LDPE, polystyrene, rigid PVC and Nylon 6.6). The predicted toxicities show variation of up to two orders of magnitude with change in fire scenario. They also show change of at least one order of magnitude for different materials in the same fire scenario. Finally, they show that in many cases CO, which is often assumed to be the most, or even the only toxicologically significant fire gas, is of less importance than either HCl, or HCN, when present, and in some cases less important than organo-irritants. Nylon 6.6 shows the highest predicted toxicity, the greatest scenario dependence, and the least sensitivity to different apparatuses, while polystyrene shows the highest sensitivity to the different apparatuses, but the lowest to different fire scenarios. PVC shows high toxicity, mostly due to HCl in the fire effluent, under all fire conditions, and LDPE shows a more progressive increase in toxicity from well-ventilated flaming to both smouldering and under-ventilated flaming.     

The effect of OCoAl‐LDH and OCoFe‐LDH on the combustion behaviors of polyvinyl chloride

The effects of the modified layered double hydroxide (LDH) of Co/Al (OCoAl‐LDH) and the modified LDH of Co/Fe (OCoFe‐LDH) on the combustion behaviors of polyvinyl chloride (PVC) during pyrolysis processes were compared and investigated. The thermal degradation and combustion behavior of the PVC composites were investigated by thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC), and cone calorimetry (CONE). The results indicate that the incorporation of LDHs brought about the improved thermal stability and reduced heat release of PVC composites at a high temperature. The smoke‐suppression properties of the composites are investigated by steady‐state tube furnace (SSTF), and the results indicated that the toxic gases such as CH₄, CO, and N_xO were inhibited by both of the two LDHs, but the OCoFe‐LDH has a better effect on the smoke suppression. Subsequently, the char layer was investigated by scanning electron microscopy–energy‐dispersive spectrometry (SEM‐EDS) and Raman analysis. The results indicate that the LDHs can promote the dechlorination of PVC during the thermal oxidation process and can inhibit the production of HCl in inert gas. Generally, OCoAl‐LDH and OCoFe‐LDH can be potential catalysts for waste disposal and can improve the fire safety of PVC.     

The Effect of Hydrotalcite and Zinc Oxide on Smoke Suppression of Commercial Rigid PVC

To reduce the smoke release of poly(vinyl chloride) (PVC) during burning, layered double hydroxides (LDHs) and zinc oxide (ZnO) powders were used to modify the polymer. The results indicated that the addition of LDHs‐ZnO had a significant effect on smoke suppression. The limiting oxygen index (LOI) reached a maximum value and the smoke density rank (SDR) exhibited a minimum value when the weight percentages of LDHs and ZnO in PVC were 3% and 2%, respectively. Thermal stabilities of the modified PVC and degradation products were investigated by means of thermogravimetry and pyrolysis‐gas chromatography‐mass spectra (Py‐GC‐MS). The LDHs‐ZnO obviously accelerated the decomposition of PVC to release hydrogen chloride, and the decomposed PVC consequently produced the trans‐conjugated polyene sequences, which easily formed crosslinked structures. However, a cyclization reaction in PVC chain without the additives produced aromatic compounds such as benzene, toluene, and naphthalene at 350°C. Even though, an amount of aromatic compounds was released from the PVC modified with LDHs‐ZnO at the temperature of 600°C, the content of the decomposed products is relatively lower compared to unmodified PVC.     

Mechanism of action of a fire retardant chloroparaffin

The mechanism by which a typical fire retardant chloroparaffin imparts fire retardant characteristics to high density polyethylene, polypropylene and polystyrene is studied by comparing the oxygen indices of these mixtures measured before and after dehydrochlorination. It is shown that flame poisoning by HCl evolved from the chloroparaffin is negligible in polystyrene and high density polyethylene, whereas it is noticeable in polypropylene. The results obtained are related to previous data on the thermal degradation of these mixtures. It is concluded that the chloroparaffin acts mainly by modifying the mechanism of pyrolysis of these polymers in the burning process. Only in the case of polypropylene is there an appreciable contribution by flame poisoning.     

Combustion of PVC: Summary of Main Lecture'

Although polyvinyl chloride) is resistant to ignition due to its chemical structure and its mode of decomposition, it will undergo thermal degradation under high thermal or fire exposure. While considerable literature exists on the mechanism of decomposition of PVC, more recent analytical studies have focused on the forced combustion of PVC and the toxicity of those combustion products. Our analytical studies have involved the analysis of combustion products from rigid PVC, flexible PVC, modified flexible PVC, and PVC-wood mixtures. While analytical studies like this cannot predict biological response, they do demonstrate the nature of experimental problems and experimental design in biological testing.     

PVC塑料流化床气化试验研究

为开发城市生活垃圾低污染流化床气化与旋风燃烧熔融技术，研究了垃圾中广泛存在的PVC塑料在流化床内的气化特性与污染物生成机理。不同温度和过量空气系数下进行了流化床PVC气化试验，分析了不同工况对PVC中Cl转化为HCl的影响。实验结果表明，反应高于600 ℃、过量空气系数大约0.4时，Cl转化为HCl的选择性达到95％以上；气化效率达到22％～25％，气化气热值达到2 000 kJ/m3～2 300 kJ/m3。反应高于700 ℃，PVC流化床气化生烟量明显减少，过量空气系数0.6时，生烟量减少到PVC质量的10％左右。提出的HCl析出与生烟机理较好地解释了试验结果，为城市生活垃圾气化熔融技术提供了相关基础数据与污染物生成及控制方法。     

Dehydrochlorination of Poly(vinyl Chloride) in Pyridine. 1. Effect of Conditions

Poly(viny1 chloride) (PVC) was dehydrochlorinated thermally in pyridine solution under N₂ atmosphere and the effect of variation of reaction time, temperature, and concentration of PVC in pyridine was studied. The extent of dehydrochlorination (or conversion, x%) increases with an increase in reaction time and temperature, and with a decrease in the concentration of PVC. Incomplete precipitation of dehydrochlorinated PVC (DHPVC) occurs by nonsolvent (methanol). During dehydrochlorination there is no HCl evolution as it forms a pyridine hydrochloride complex which is supposed to act as a catalyst for dehydrochlorination. A possible mechanism has been proposed. Chain scission and cross-linking reactions are responsible for the molecular weight changes that take place during the reaction.