以天然气为原料合成氨实用工艺

目录1 引言 (1)1.1 氨的性质 (1)1.2 氨的用途 (2)1.3 合成氨的发展历史 (2)1.3.1 氨气的发现 (2)1.3.2 合成氨的发现及其发展 (2)1.3.3 国外合成氨工业发展 (3)1.3.4 国合成氨工业发展 (3)1.3.5 国合成氨工业的发展趋势 (4)1.4 合成氨工段设计主要参数计算的主要容 (5)2 工艺计算 (6)2.1 生产流程简述 (6)2.2 原始条件 (6)2.3 物料衡算 (7)2.3.1 合成塔物料衡算 (8)2.3.2 氨分离器气液平衡计算 (9)2.3.3 冷交换器气、液平衡计算 (11)2.3.4 液氨贮槽气、液平衡计算 (11)2.3.5 液氨贮槽物料计算 (13)2.3.6 合成系统物料计算 (14)2.3.7 进出合成塔物料计算 (15)2.3.8 进出水冷器物料计算 (16)2.3.9 进出氨分离器物料计算 (16)2.3.10 冷交换器物料计算 (17)2.3.11 氨冷器物料计算： (18)2.3.12 冷交换器物料衡算 (20)2.3.13 液氨贮槽物料计算 (21)2.3.14 物料计算结果汇总 (21)2.4 热量核算 (22)2.4.1 交换器热量核算 (22)2.4.2 氨冷器热量核算 (25)2.4.3 循环机热量核算 (27)2.4.4 合成塔热量核算 (28)2.4.5 废热锅炉热量核算 (31)2.4.6 热交换器热量核算 (32)2.4.7 水冷器热量核算 (33)2.4.8 氨分离器热量核算 (34)3 氨合成过程中的绿色化学化工 (35)3.1 绿色化学化工的基本概念 (35)3.2 合成氨工段的原子经济性 (35)3.3 合成氨工段的热能综合利用 (35)3.4 合成氨工段的“三废”处理 (36)4 设备选型 (37)4.1 合成塔催化剂层设计 (37)4.2 换热器： (42)4.3 废热锅炉设备工艺计算 (43)4.3.1 计算条件 (43)4.3.2 官给热系数α计算 (43)计算 (45)4.3.3 管给热系数αi4.3.4 总传热系数K 计算 (46)计算 (46)4.3.5 平均传热温差Δtm4.3.6 传热面积 (46)4.4 水冷器设备工艺计算: (47)4.4.1 计算条件 (47)4.4.2 管给热系数的计算 (47)4.4.3 管外给热系数 (48)4.4.4 传热温差 (49)4.4.5 传热总系数K (49)4.4.6 传热面积 (49)4.5 冷交换器设备工艺计算 (49)4.5.1 计算条件 (49)4.5.2 管给热系数的计算 (50)4.5.3 管外给热系数 (52)4.5.4 总传热系数 (55)4.5.5 传热面积核算 (55)4.5.6 主要设备选型汇总表 (55)5 合成氨合成车间的安全生产 (57)5.1 合成氨车间的职业危害 (57)5.2 安全措施 (58)5.3 合成氨工序重大事故危险与防 (59)5.3.1 蒸汽锅炉的重大事故危险与防 (59)5.3.2 容器爆炸 (60)5.3.3 灼烫 (60)5.3.4 起重伤害 (60)参考文献 (62)致谢 (63)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，并且参照双联化工厂合成氨工段的现场生产而设计而成。

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，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①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。

②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 material 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 ammonia 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 pollution 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 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 subsequent 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 recycling 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 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 problem of heat exchanger of synthetic tower outside, waste heat boiler configuration is actually how to improve reaction heat recovery rateand 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 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 365 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 temperature 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 the 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 reduce 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 cooling 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 exchanger`s two entrance, so as to reduce the resistance of the system, 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. 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 gas into ammonia cooler for cold air cooling and heat exchange, to recover the freezing cold gas refrigeration, make the hot gas that into theammonia cooler cooling, which can save frozen volume, meanwhile separated the liquid ammonia after ammonia cooling ammonia containing gas mixture. Anhui chemical 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 protection①Empty gas and purge gas film feeding hydrogen extraction recovery 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.②The other wastewater 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 flow 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 results, 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。