黄磷尾气对燃气设备高温腐蚀行为及燃烧特性研究

【作者】 郜华萍；

【导师】 宁平；

【作者基本信息】 昆明理工大学 ， 环境工程， 2015， 博士

【摘要】 黄磷尾气是高热值、但杂质含量复杂的工业尾气,由于有磷、硫等杂质的存在,尾气利用过程中,短时间内使设备严重腐蚀而失效,利用率不足50%,其余是火炬燃烧后排入大气,既浪费了有价、宝贵的CO资源,又污染了大气环境,资源高消耗、环境严重污染制约了黄磷行业的健康发展。有效利用黄磷尾气,是磷化工多年来国内外的研究热点。黄磷尾气杂质及含量、燃烧利用过程形成的燃烧产物、腐蚀产物演化过程、腐蚀类型、燃烧特性,是决定黄磷尾气有效利用的关键因素。本论文通过测定黄磷原料、炉气以及尾气成份,进行了定性、定量分析,获得了真实有效的数据,开展了黄磷尾气燃烧现场腐蚀研究和模拟实验腐蚀研究,同时对磷单组分腐蚀、磷-硫共存腐蚀环境下,不同材料的腐蚀产物组织结构和形貌进行了鉴定和分析,揭示了其腐蚀机理；提出了磷的腐蚀露点概念,研究了尾气混合气COx-POx-NOx-H2O的腐蚀露点,验证了PH3是加速黄磷尾气燃气对设备的腐蚀设想；采用传统燃气燃烧理论,开展了燃烧特性研究,提出了黄磷尾气混合体系平均质量、平均动力粘度、平均理论燃烧温度等指标,为对黄磷尾气的资源化利用提供了科学的理论依据。论文揭示了黄磷尾气燃气最新成果,归纳总结正确。1、采用传统腐蚀机理理论研究——电化学方法与实际烧蚀部件鉴定、分析方法相结合,开展了黄磷尾气资源化利用过程中燃气对设备腐蚀行为研究。在本课题组发明的系列腐蚀研究专利装置中,研究不同材料的样件,在磷酸腐蚀、硫酸-硫酸协同腐蚀环境下的腐蚀产物的形成机制；通过XRD、XPS、SEM等腐蚀产物形貌和组织结构鉴定、分析,揭示了黄磷尾气燃气腐蚀类型是电化学腐蚀、晶界腐蚀、露点腐蚀、高温腐蚀、硫化物应力开裂(SSC)、连多硫酸晶间腐蚀共存。腐蚀动力学研究表明：(1)在磷酸环境COx-POx-NOx-H2O下,材料年腐蚀速率为：Q245R>16MnR>>304>316L；低温耐磷酸腐蚀性能：16MnR>>Q245R;高温耐磷酸腐蚀性能：316L>304>16MnR>>Q245R。(2)在磷酸-硫酸共存环境COx-POx-SO-NOx-H2O下,材料腐蚀速率为：16MnR>Q245R>>304>316L>合金；高温耐磷酸-硫酸腐蚀性能：合金>316L>304>>16MnR>Q245R。2、采用腐蚀动力学和腐蚀热力学研究,结合新的理论计算方法,提出了磷的露点腐蚀概念。通过测定、分析不同材料在不同低温下的腐蚀极化曲线(Polarizationalcuvers)、塔菲尔曲线(Tafel cuvers)、腐蚀交流阻抗(AC impedance corroded),分析磷环境下及磷-硫共存环境下腐蚀动力学曲线,运用Gibbs相律,推导黄磷尾气多成分混合气COx-POx-NOx-H2O体系磷酸露点计算式,通过现场腐蚀研究和实验模拟腐蚀研究,获得了磷环境下的低温腐蚀露点、高温磷腐蚀露点、高温磷-硫共存腐蚀露点,验证了PH3加速了燃气对设备的腐蚀的设想。(1)在磷酸环境POx-NOx-COx-H2O尾气体系,Q245R、304、316L、合金,高温磷酸的露点温度均为300℃-350℃；16MnR高温腐蚀露点为700℃。(2)在磷-硫共存环境POx-SOx-NOx-COx-H2O尾气混合体系中,Q245R、304、316L、合金,露点腐蚀温度为300℃-350℃。黄磷尾气混合体系CO-H2-CH4-H2S-PH3-COS-SC2-P4的腐蚀露点,与理论计算温度为358.25℃相符,表明PH3加速了燃气对设备的腐蚀。3、采用理论计算与实际检测相结合研究方法,开展了黄磷尾气燃气燃烧特性研究。在本课题组发明的专利装置中,利用Tanford扩散理论、ESCMO湍流燃烧等理论,测定实际黄磷尾气燃烧的温度、不同空气过剩系数下的燃烧温度场分布,研究火焰的辐射特性,获得了黄磷尾气燃气燃烧时的温度场、流场分布。结合采用热力学软件Factsage6.1,计算CO-H2-CH4-H2S-PH3-COS-SC2-P4体系下,不同温度的熵变、焓变、比热吉布斯自由能变、平衡常数等。采用传统燃气燃烧理论,提出了黄磷尾气混合体系CO-H2-CH4-H2S-PH3-COS-SC2-P4平均质量为28.48806667 g/mol,平均动力粘度为1.68232E-05(Pa.s),着火点为100℃,平均理论燃烧温度为2017.267℃,平均燃烧特征系数β=0.283646933；最佳空气过剩系数α：净化前α=1.2-1.4,净化后α=1.3,理论计算α=1.02等,为黄磷尾气燃气利用提出了理论依据。4、结合以上研究成果,成功开发了系列黄磷尾气燃气锅炉,实现了黄磷企业几十年一直要做而未能做的黄磷尾气燃气锅炉产业化应用。更多还原

【Abstract】 Phosphorus off-gas is a high calorific value industrial off-gas containing complex impurities. The existence of phosphors and sulfur cause serious corrosion to the facilities, as a result, the facilities will lose their efficiency in a short time. Meanwhile, the off-gas application efficiency is less than 50%, the other part of the off-gas will be burned into the atmosphere. As a result, the valuable CO resource was wasted and the environment is being polluted. This kind problem restricts the development of the phosphor industry. So, efficient application of the phosphors off-gas becomes the hot point of investigation over the world. The impurities and their concentration, the types of the burning products and their changing in the burning process, the corrosion type and the combustion characteristic are the essential problem determining the effective application of phosphorus tail-gas.In this dissertation, qualitative and quantitative determinations were carried for the raw phosphorus and the burning gas as well as the tail-gas compositions. As a result, a lot of authentic and effective data were obtained. In the meantime, the site corrosion and imitation investigation were carried. Also, the corrosion products and their structure organization pattern of phosphorus itself and the co-corrosion of phosphorus-sulfur to different materials were determined and analyzed. Finally, their corrosion mechanisms were revealed. The concept of phosphorus corrosion dew point was put forwarded. The corrosion dew point of mixed COx-POx-NOx-H2O-PH3 in the phosphorus tail-gas accelerating the corrosion of the facilities was tested and verified. Based on traditional burning gas combustion theory, the combustion characteristics of this tail-gas were investigated, the indexes of mean mass of mixed phosphorus tail-gas system, the mean dynamic viscosity, the theoretical combustion temperature were put forwarded. Conclusions are as the follows.1.Theoretical corrosion mechanism investigation with traditional methodBy means electrochemical methods together with identification of actual corroded components the corrosion behavior of the facilities were investigated, where a series of patented units owned by our group were used, with which the formation process of corrosion products were able to be revealed for different materials in phosphoric acid environment and phosphoric acid-sulfuric acid environment. The corrosion products and their tissue morphology and structure were identified by XRD,XPS, SEM etc. it revealed that the phosphorus off-gas corrosion belong to a combination corrosion of electrochemical corrosion, inter-granular corrosion, dew point corrosion high temperature corrosion, sulfide stress cracking (SSC) and sulfuric acid inter-crystal corrosion. Corrosion kinetic studies shows.(1) In the phosphoric acid environment of COx-POx-NOx-H2O, corrosion rate of materials are Q245R> 16MnR>>304> 316L; low-temperature corrosion resistant ability to phosphoric acid are 16MnR>>Q245R; high-temperature corrosion-resistant phosphate are 316L>304> 16MnR>>Q245R.(2). In the phosphoric acid environment of COx-POx-SOx-NOx-H2O, corrosion rate are 16MnR> Q245R>> 304> 316L> alloy; high temperature resistant to phosphoric acid-sulfuric acid corrosion are Alloy> 316L stainless steel> 304>>16MnR> Q245R.2. Corrosion kinetics and thermodynamics investigationsBy means of new theoretical calculation method, phosphorus dew point corrosion concept is put forwarded through the determination of low temperature corrosion polarization curves, Tafel curves, AC impedance corroded and related analysis. The COx-POx-NOx-H2O system phosphoric acid corrosion dew point calculation formula was deduced with the help of Gibbs phase rule. Finally, the low temperature and high temperature corrosion dew point of phosphorus were obtained. Also, the assume of PH3 accelerating off-gas corrosion to the facilities was tested and verified.(1)In the phosphoric acid environment of POx-NOx-COx-H2O, the high temperature phosphoric acid dew point temperatures are 300℃-350℃ for Q245R,304,316L, alloys. Meanwhile, for 16MnR dew point temperature corrosion is 700℃.(2) In the phosphorus-sulfur coexistence environment of POX-SOX-NOX-COx-H2O, the corrosion dew point temperature is 300℃～350℃ for Q245R,304,316L, alloy.In phosphorus tail-gas of CO-H2-CH4-H2S-PH3-COS-SC2-P4 system, the determined corrosion dew point temperature is consistent with theoretical calculation value 358.25℃, validating the concept that PH3 accelerates corrosion to the devices.3.Combustion characteristics investigation of yellow phosphorus off gasThe combustion characteristics of yellow phosphorus off gas were investigated combining theoretical calculations and actual testing. In the patented devices invented by our group, the theory of Tanford diffusion, ESCIMO turbulence combustion and so on were carried to determine the combustion temperature of phosphorus off-gas.Also, the combustion temperature distribution field in different excess air coefficient were measured. The temperature field and flow field distribution of yellow phosphorus off gas were obtained by studying the radiation characteristics of the flame. The CO-H2-CH4-H2S-PH3-COS-SC2-P4 system’s entropy, enthalpy, Gibbs free energy and equilibrium constant under different temperature were calculated by the thermodynamic software Factsage 6.1. The estimated average mass of phosphorus off-gas mixture of CO-H2-CH4-H2S-PH3-COS-SC2-P4 is 28.48806667g/mol, the average dynamic viscosity is 1.68232E-05 (Pa. s), the ignition point is 100℃, the average theoretical combustion temperature is 2017.267℃, the average combustion characteristic coefficient β is 0.283646933.For the optimum air excess coefficient a of phosphorus off-gas mixture system:before purification, α= 1.2-1.4, after purification,α=1.3,while the theoretical calculation of α=1.02, etc. These are theoretical basis for phosphorus off-gas recycle.Combining all the above study results, a series of yellow phosphorus tail gas boiler were successfully developed. As a result, phosphorus enterprises are able to bring about phosphorus exhaust gas boiler in the industrial applications, which has been expected for decades.更多还原