以天然气为原料合成氨工艺.docx

1、以天然气为原料合成氨工艺以天然气为原料合成氨工艺设计参数年产10万吨合成氨的合成工段工艺设计（以天然气为原料）产量：10万吨/年，液氨合成塔入口惰性气体含量：15%合成塔进口氨浓度：2.5%合成塔出口氨浓度：13.2%合成塔操作压力：30MPa新鲜补充气：N2 24%；H2 75%；CH4 0.3%；Ar 0.7%精炼气温度：35水冷器出口气体温度：35循环机进出口压差：1.47Mpa年工作日：300d产品质量规格：氨含量(wt%)=99%以天然气为原料年产10万吨合成氨厂合成工段的工艺设计设计说明书任务来源：本次设计按照化工系下达的设计任务书进行编制的，并且参照石家庄双联化工厂合成氨工段的现

2、场生产而设计而成。设计标准：按照国家相关化工安全生产标准和化工仪器设备设计标准设计设计原则：本设计的原则是以绿色化工为准则，低耗能、低成本、无污染的原则。设计的主要内容及特点：本工段生产液氨，生产能力为10万吨液氨/年，与传统的流程相比较具有节能低耗的特点。在废热锅炉和水冷器之间设计一个热交换器，通过热交换器回收了废热锅炉出来的气体中剩余的热量并同时为原料气进行了预热，另外也进一步降低了合成气的温度，为对后续的冷凝工作有利，间接的节约了消耗的热量和冷量。现将具体的设计内容介绍如下：（1）循环机位置本工段循环机设置在氨分离系统后，合成塔之前，从而充分利用循环机压缩功，提高进合成塔温度，减少冷量消

3、耗，降低氨冷器负荷，同时提高进塔压力，提高合成率，而进循环机的氨冷量较低，避免了塔后循环机流程容易带液氨而导致循环机泄漏。（2）反应热回收的方式及利用热量的回收主要集中在合成塔处，这里涉及到废热锅炉的热量回收利用和合成塔塔外换热器如何科学设置的问题，废热锅炉的配置实际上是如何提高反应热的回收率和获得高品位热的问题，本次设计选择的是塔后换热器及后置锅炉的工艺路线，设置塔后换热器使废热锅炉出口气体与合成塔二进气体换热，充分提高合成塔二进温度，相应提高了合成塔二出温度，进废热锅炉的气体温度为365度，副产1.372兆帕的中压蒸汽，充分提高回收热量品位。（3）采用“二进二出”合成流程全部冷气经合成塔的

4、外围环隙后进入热交换器，可使合成塔塔体各点温度分布均匀，出口气体保持较低温度，确保合成塔长期安全稳定运行，与循环机来的冷气直接进入热交换器相比，使热交换器出口温度增大。进入水冷的气体温度降低意味着合成余热回收率高和水冷器的负荷低。（4）水冷器和氨冷器的设置水冷后直接进行分离液氨然后再进行冷交，水冷有利于降低后续氨冷的负荷，边冷却边分离液氨，即提高了液氨的分离效果，又避免了气液两相流的存在，通过设置氨冷器的冷凝充分解决了低压下，水冷后很少有氨冷凝下来的矛盾，达到了进一步冷却，保证合成塔入口氨含量的要求。（5）新鲜气及放空点位置设置新鲜气的补充设置在冷交换气的二次入口，以便减少系统阻力，并通过氨冷

5、器进一步洗脱微量二氧化碳和一氧化碳及氨基甲酸等杂质，有利于保护触媒、防止管道和设备堵塞。放空点设置在冷交换器和氨分离器之间，氨分后有效气体浓度较低，惰性气体含量较高，有利于降低新鲜气单耗。（6）冷交换器设备的使用分离器为外向型旋流板，上部换热器为列管换热器和下部氨分离器，将热气体在进入氨冷器前用冷气体进行冷却换热，以回收冷气体的冷冻量，使入氨冷器的热气体预冷却，从而节省冷冻量，同时分离经氨冷后含氨混和气中的液氨，安徽淮南化工公司发表与小氮肥杂志上的有关资料表明，该设备节能降耗显著。（7）三废治理及环境保护放空气弛放气送膜提氢回收系统，先用氨洗涤塔回收几乎全部氨，制成浓氨水，再回收大部分氨送入高

6、压机压缩后制氨既可以避免氨气进入大气，与放空气作燃料相比又更合理经济。其他废水废渣集中处理达到国家排放标准后排放。（8）生产制度：每年操作日300天，三班连续操作。（9）结论本设计主要是对于合成氨的工艺流程的设计；其中包括合成氨各主要工段设备的物料衡算和热量核算包括：合成塔的物料衡算和热量衡算、氨冷器的物料衡算及热量核算、冷交换器的物料衡算和热量核算等；合成氨各主要设备的工艺计算和选型；合成氨车间的安全因素及防范措施；工艺流程、车间中设备布置图以及氨合成塔、废热锅炉、水冷器三个主要设备的CAD图纸。关键词：合成氨；物料衡算；热量核算；工艺设计Using natural gas as raw m

7、aterial with annual output of 100000 tons of synthetic ammonia plant of the section in process designDesign specificationThe source of the taskThis design is according to the chemical industry department issued the design task book prepared, and referring to Shijiazhuang joint chemical factory ammon

8、ia section on-site production and designed.Design standards:In accordance with the relevant national safety production standard and chemical equipment designDesign principles: The principle of design is based on the green chemical industry as a criterion, low energy consumption, low cost, no polluti

9、on principle.Design of the main contents and characteristics:The production of liquid ammonia, liquid ammonia production capacity of 100000 tons per year, and Compared with the traditional process this process have the characteristics of energy-saving and low consumption. To design a heat exchanger

10、between the waste heat boilers and water coolers, recycling the residual heat in the waste heat boiler gas through the heat exchanger and at the same time as the feed gas preheating. The other also further reduces the synthesis gas for subsequent condensation temperature, favorable for the subsequen

11、t condensation and indirect savings in the consumption of heat and cold.The specific design and content are as follows:(1) circulation machine locationThis section cycle machine is arranged in the behind of the ammonia separation system, and before the synthetic tower, thus make full use of recyclin

12、g machine compression work, raise the gas temperature of synthetic tower, reduce the cold consumption, reduce the ammonia cooler load, meanwhile increasing the inlet pressure of tower, improve the rate of synthesis and into the circulation machine ammonia cooling capacity is relatively low, avoiding

13、 the tower posterior circulation machine process with liquid ammonia and lead to circulating machine easy to leak.(2)The ways of reaction heat recovery and utilizationHeat recovery focuses on the synthetic tower, it involves in waste heat boiler heat recovery utilization and how scientific setting p

14、roblem of heat exchanger of synthetic tower outside, waste heat boiler configuration is actually how to improve reaction heat recovery rate and obtain high grade heat problem. This design is the choice of the process route is that the heat exchanger in behind of the tower and post boiler. Set behind

15、 the tower heat exchanger made of waste heat boiler outlet gas and synthesis tower two into the gas heat exchanger, fully improve the synthetic tower two inlet gas temperature, increase the synthesis tower two outlet gas temperature.The temperature of the gas that is into the waste heat boiler is 36

16、5 degrees, and produce 1.372MPa steam pressure,so it improve recovery of heat grade.(3)The use of the The two gas inlet two outlet synthesis processAll air-conditioning into the heat exchanger after the peripheral annulus of the synthetic tower, the synthetic tower body at each point of a uniform te

17、mperature distribution, and export gas to maintain a lower temperature to ensure that the synthesis tower directly into the long-term safe and stable operation. Compared with the circulation machine to cold gas directly into the heat exchanger, the heat exchanger outlet temperature increase. Enter t

18、he water temperature of the gas to reduce means that there have a high of synthesis waste heat recovery rate and low load of water cooler.(4) Water cooler and ammonia cooler settingsAfter water-cooled ,the gas directly the separation of liquid ammonia then cold exchang, water-cooling is helpful to r

19、educe the subsequent ammonia cooling load, Edge cooling and separation of liquid ammonia not only improve the liquid ammonia separation, but also to avoid the presence of gas-liquid two-phase flow. Through the setting of ammonia tanks condensation fully solved under low pressure after the water cool

20、ing few ammonia condensing the contradiction down, to further cooling, ensure that the content of ammonia synthesis tower entrance requirements. (5) The fresh gas and vent position settingThe supplementary of fresh gas set in the cold exchangers two entrance, so as to reduce the resistance of the sy

21、stem, and through the ammonia cooler further elution trace impurities such as carbon dioxide , carbon monoxide and amino acid and so on, beneficial to the protection of catalysts, and prevent piping and equipment jam. The setting of vent point located between the cold exchanger and ammonia separator

22、. After the concentration of the gas effective ammonia points lower, inert gas content is higher, which helps reduce fresh gas consumption.(6) The use of cold heat exchanger equipmentSeparator for extroversion swirl plate, heat exchanger tube heat exchanger for upper and lower ammonia separator, hot

23、 gas into ammonia cooler for cold air cooling and heat exchange, to recover the freezing cold gas refrigeration, make the hot gas that into the ammonia cooler cooling, which can save frozen volume, meanwhile separated the liquid ammonia after ammonia cooling ammonia containing gas mixture. Anhui che

24、mical industry company in Huainan and Small Nitrogenous Fertilizer published on the magazine of relevant data show that the equipment is saving energy and reducing consumption is significant.(7) Waste management and environmental protectionEmpty gas and purge gas film feeding hydrogen extraction rec

25、overy system, using ammonia washing tower recovery almost all ammonia, make concentrated ammonia, and recycling most ammonia then into high pressure machine compressed ammonia can avoid the ammonia gas into the atmosphere, and the discharge gas as fuel and more reasonable than ecommic.The other wast

26、ewater reatment to focus on waste residue after national emission standard emissions.(8) Te production systemAnnual operating on the 300 days and three consecutive operations.(9) ConclusionThis design is mainly to the synthetic ammonia processing flow design; it includes synthetic ammonia process fl

27、ow design, the material balance and heat calculation of synthesis tower, ammonia cooler calculation and cold exchanger, the process calculation and equipment selection of the major equipments of ammonia synthesis, and ammonia synthesis plant safety factors and preventive measure. According to the re

28、sults, five CAD drawings on process, workshop equipment layout and ammonia synthesis tower, waste heat boiler, water cooler are attached in the article.Key words: Ammonia synthesis; material balance; thermal calculation; process design1引言氮是植物营养的重要成分之一，大多数的植物不能直接吸收存在于空气中的游离氮，只有当氮与其他元素化合以后，才能被植物吸收利用。将

29、空气中的游离氮转变为化合态氮的过程称为“固定氮”。20世纪初，经过人们的不懈探索，终于成功的开发了三种固定氮的方法：电弧法、氰氨法、和合成氨法。其中合成氨法的能耗最低。1913年工业上实现了氨合成以后，合成氨法发展迅速，30年代以后，合成氨法已成为人工固氮的主要方法。1.1氨的性质氨化学式为NH3常温下为无色有刺激性辛辣味的恶臭气体，会灼伤皮肤、眼睛，刺激呼吸道器官粘膜，空气中氨的质量分数占0.5% 1.0%就会使人在几分钟内窒息。氨的主要物理性质见表0-1。氨在常温加压易液化，称为液氨。氨易溶于水，与水反应形成水合氨（NH3 + H2O=NH3H2O）简称氨水，呈弱碱性，氨水极不稳定，受热分

30、解为氨气和水，氨含量为1%的水溶液PH为11.7。浓氨水氨含量为28% 29%。氨的化学性质比较活泼，能与酸反应生成盐，如与盐酸反应生成氯化铵；与磷酸反应生成磷酸铵；与硝酸反应生成硝酸铵；与二氧化碳反应生成甲基甲酸铵，脱水后生成尿素等等。表1-1氨的主要物理性质1项目数据项目数据相对分子质量17.03 临界密度/(g/cm3)0.235 氮含量82.20 临界压缩系数PV=ZRT0.242 摩尔体积(0，0.1MPa)/(L/mol)22.08 临界热导率kj/K.h.m)0.522 气体密度(0，0.1MPa)/(g/L)0.7714 沸点(0.1MPa)/-33.35液体密度(-33.4,

31、0.1MPa)/(g/cm3)0.6818 蒸发热（-33.4)/(kJ/kg)1368.02 临界温度/132.4 冰点/-77.70 临界压力/MPa11.30 熔化热(-77.7)/(kJ/kg)332.42 临界比体积/(L/kg)4.257 1.2氨的用途氨主要用于制造化学肥料，如农业上使用的所有氮肥、含氮混合肥和复合肥等；也作为生产其他化工产品的原料，如基本化学工业中的硝酸、纯碱、含氮无机盐，有机化学工业的含氮中间体，制药工业中磺胺类药物、维生素，化纤和塑料工业中的己酰胺、己二胺、甲苯二异氰酸酯、人造丝、丙烯腈、酚醛树脂等都需要直接或间接地以氨为原料。另外在国防工业尖端技术中，作为

32、制造三硝基甲苯、三硝基苯酚、硝化甘油、硝化纤维等多种炸药的原料。氨还可以做冷冻，冷藏系统的制冷剂。 1.3合成氨的发展历史1.3.1氨气的发现十七世纪30年代末英国的牧师、化学家 S.哈尔斯（HaLes，16771761）,用氯化铵与石灰的混合物在以水封闭的曲颈瓶中加热，只见水被吸入瓶中而不见气体放出，1774年化学家普利斯德里重做该实验，用汞代替水来密封，制得了碱空气（氨），并且他还研究发现了氨的性质，发现氨极易溶于水、可以燃烧，还发现该气体通以电火花时其容积增加，而且分解为两种气体：H2和N2，其后H.戴维（Davy，17781829）等化学家继续研究，进一步证明了2体积的氨通过电火花放电后，分解为1体积的氮气和3体积的氢气2。1.3.2合成氨的发现及其发展19世纪以前农业上所需的氮肥来源主要来自于有机物的副产物和动植物的废物，如粪便、腐烂动植物等等，随着农业和军工生产的发展的需要，迫切的需要建立规