毕业设计（论文）年产4万吨合成氨全中变换工序工艺

1、中 南 大 学本科生毕业论文(设计)题 目年产4万吨合成氨全中变换工序工艺学生姓名 指导教师 学 院 湖南化工职业技术学院 专业班级 化 工 0615 完成时间 2010年10月9日 年产4万吨合成氨全中变变换工序工艺设计任务书一、设计项目：合成氨厂变换工序工艺设计二、设计规模：4 三、设计阶段：初步设计四、设计时间 2010年 10月28日 2010年 11月9 日五、设计条件：1、原料（半水煤气）规格： 组成 v%(干) 38.0 22.0 30.0 8.3 1.5 0.2 100.0半水煤气入系统（入饱和塔）温度为：502、产品规格出变换工序气体中 3.5%（干）；变换气出系统温度353

2、、生产方式：加压变换 半水煤气进系统压力：0.8mpa；系统压差0.05mpa 4、地区条件：湖南5、触媒型号：中变催化剂（型号自选）6、其他条件：外加蒸汽1.0mpa饱和或过热蒸汽（过热温度为300）。六、设计成果：1、设计说明书一份2、带控制点的工艺流程图（中变流程）3、设备平面布置图七、设计主要参考文献：1、梅安华主编.小合成氨厂工艺技术与设计手册上册、下册，北京：化学工业出版社.19952、化工（含轻工）类毕业设计指导书.北京：中央广播电视大学出版社，19863、周大军主编，化工制图.北京：化学工业出版社.20054、陈声宗主编，化工设计.北京：化学工业出版社.20015、天津大学化工

3、原理教研室编.化工原理上册、下册，北京：化学工业出版社.2000目 录1前言 12工艺条件 23工艺流程的确定 34主要设备的选择说明 35对本设计的评述 26英文翻译 4第一章 变换工段物料及热量衡算 8第一节 中温变换物料及热量衡算 811确定转化气组成81.2水汽比的确定 91.3中变炉一段催化床层的物料衡算 101.4中变炉一段催化床层的热量衡算 101.5中变炉催化剂平衡曲线 111.6最佳温度曲线的计算 111.7操作线计算 121.8中间冷淋过程的物料和热量计算 121.9中变炉二段催化床层的物料衡算 121.10中变炉二段催化床层的热量衡算 131.11中变炉三段催化剂床层的物

4、料衡算 141.12中变炉三段催化床层的热量衡算 15第二节 中变炉的物料与热量计算 17第三节 废热锅炉的热量和物料计算 18第四节 主换热器的物料与热量的计算 20第五节 调温水加热器的物料与热量计算 22第二章 设备的计算 231. 中温变换炉计算 232. 饱和热水塔计算 273主热交换器计算 30参考文献及致谢 34前 言氨是一种重要的化工产品，主要用于化学肥料的生产。我国合成氨工业的发展情况解放前我国只有两家模不大的合成氨厂，解放后合成氨工业有了迅速发展。1949年全国氮肥产量仅0.6万吨，而1982年达到1021.9万吨，成为世界上产量最高的国家之一。近几年来，我国引进

5、了一批年产30万吨氮肥的大型化肥厂设备。我国自行设计和建造的上海吴泾化工厂也是年产30万吨氮肥的大型化肥厂。这些化肥厂以天然气、石油、炼油气等为原料，生产中能量损耗低、产量高，技术和设备都很先进。合成氨生产经过多年的发展，现已发展成为一种成熟的化工生产工艺。合成氨的生产主要分为：原料气的制取；原料气的净化与合成。粗原料气中常含有大量的c，由于co是合成氨催化剂的毒物，所以必须进行净化处理，通常，先经过co变换反应，使其转化为易于清除的co2和氨合成所需要的h2。因此，co变换既是原料气的净化过程，又是原料气造气的继续。最后，少量的co用液氨洗涤法，或是低温变换串联甲烷化法加以脱除。变换工段是指

6、co与水蒸气反应生成二氧化碳和氢气的过程。在合成氨工艺流程中起着非常重要的作用。工艺原理：一氧化碳变换反应式为：co+h2o=co2+h2+q (1-1) co+h2 = c+h2o (1-2) 其中反应（1）是主反应，反应（2）是副反应，为了控制反应向生成目的产物的方向进行，工业上采用对式反应（11）具有良好选择性催化剂，进而抑制其它副反应的发生。一氧化碳与水蒸气的反应是一个可逆的放热反应，反应热是温度的函数。变换过程中还包括下列反应式：h2+o2=h2o+q工艺条件1.压力：压力对变换反应的平衡几乎没有影响。但是提高压力将使析炭和生成甲烷等副反应易于进行。单就平衡而言，加压并无好处。但从动

7、力学角度，加压可提高反应速率。从能量消耗上看，加压也是有利。由于干原料气摩尔数小于干变换气的摩尔数，所以，先压缩原料气后再进行变换的能耗，比常压变换再进行压缩的能耗底。具体操作压力的数值，应根据中小型氨厂的特点，特别是工艺蒸汽的压力及压缩机投各段压力的合理配置而定。一般小型氨厂操作压力为0.7-1.2mpa,中型氨厂为1.21.8mpa。本设计的原料气由小型合成氨厂天然气蒸汽转化而来，故压力可取1.7mpa.2.温度：变化反应是可逆放热反应。从反应动力学的角度来看，温度升高，反应速率常数增大对反应速率有利，但平衡常数随温度的升高而变小，即 co平衡含量增大，反应推动力变小，对反应速率不利，可见

8、温度对两者的影响是相反的。因而存在着最佳反应温对一定催化剂及气相组成，从动力学角度推导的计算式为tm= 式中tm、te分别为最佳反应温度及平衡温度，最佳反应温度随系统组成和催化剂的不同而变化。3.汽气比：水蒸汽比例一般指h2o/co比值或水蒸汽/干原料气.改变水蒸汽比例是工业变换反应中最主要的调节手段。增加水蒸汽用量，提高了co的平衡变换率，从而有利于降低co残余含量，加速变换反应的进行。由于过量水蒸汽的存在，保证催化剂中活性组分fe3o4的稳定而不被还原，并使析炭及生成甲烷等副反应不易发生。但是，水蒸气用量是变换过程中最主要消耗指标，尽量减少其用量对过程的经济性具有重要的意义，蒸汽比例如果过

9、高，将造成催化剂床层阻力增加；co停留时间缩短，余热回收设备附和加重等，所以，中（高）变换时适宜的水蒸气比例一般为：h2o/co=35，经反应后，中变气中h2o/co可达15以上，不必再添加蒸汽即可满足低温变换的要求。工艺流程确定:目前的变化工艺有：中温变换，中串低，全低及中低低4种工艺。本设计选用中变工艺。以煤为原料的中小型氨厂制得的半水煤气中含有较高的一氧化碳,需采用多段中变流程.而且由于出脱硫塔系统的半水煤气温度与水蒸气含量较低,气体在进入中变炉之前设有原料气预热及增湿装置.另外,由于中变的反应量大,反应放热多,应充分考虑反应的移热和余热回收半水煤气首先进入饱和热水塔1,在饱和塔内气体与

10、塔顶喷淋下来的130-140的热水逆流接触,使半水煤气提高增湿。出饱和塔的气体进入气水分离器2分离夹带的液滴,并与蒸汽过热器5送来的300-500的过热蒸汽相混,使半水煤气中的汽气比达到工艺条件的要求,然后进入主热交换器3和中间换热器4,使气体温度升至380进入变换炉,经第一段催化床层反应后温度升到480-500,经蒸汽过热器,中间换热器与蒸汽,半水煤气换热,降温后进入第二段催化床层反应.反应后的高温气体用冷凝水冷凝降温后,进入第三段催化剂床层反应.气体离开变换炉的温度为400左右,变换气依次经过主热交换器,第一水加热器,热水塔,第二热水塔第二水加热器回收热量,再经变换气冷却器9降至常温后送到

11、下一工序.主要设备的选择说明:中变流程中，主要设备有中变炉、饱和热水塔,换热器等。中变炉选用b109型催化剂，计算得中变催化剂实际用量10.59m3。以上设备的选择主要是依据所给定的合成氨系统的生产能力、原料气中碳氧化物的含量以及变换气中所要求的co浓度。对本设计评述半水煤气变换工段工序是合成氨生产中的第一步，也是较为关键的一步，因为能正常生产出合格的压缩气，是后面的所有工序正常运转的前提条件。因此，必须控制一定的工艺条件，使转化气的组成，满足的工艺生产的要求。在本设计中，根据已知的半水煤气组成，操作条件，采用了全中变的工艺流程路线。首先对中变进行了物料和热量衡算，在计算的基础上，根据计算结果

12、对主要设备选型，最终完成了本设计的宗旨。设计中一共有中变炉，主换热器，调温水换热器，饱和热水塔,中间换热器几个主要设备。由于半水煤气变换工段工序是成熟工艺，参考文献资料较多，在本设计中，主要参考了小合成氨厂工艺技术与设计手册和合成氨工艺学这两本书。由于时间有限，设计可能不完善，请各位老师指出。谢谢！英文翻译 forewordammonia is an important chemical products, mainly for the production of chemical fertilizers. china's industrial ammonia development

13、of the liberation of our country, only two small ammonia plant, after the liberation of synthetic ammonia industry has developed rapidly. national production of nitrogen fertilizer in 1949 only 06,000 tons, and in 1982 reached 10,219,000 tons, the world's highest output of one of the countries.

14、in recent years, china has introduced a number of annual output of 300,000 tons of large-scale nitrogen fertilizer plant equipment. china's self-designed and built by shanghai and jiangsu jing is also a chemical plant with an annual output of 300,000 tons of large-scale nitrogen fertilizer plant

15、. these chemical fertilizer plant to natural gas, oil and gas refining, and other raw materials for the production of low-energy loss, high oammonia production after years of development, has grown into a mature chemical production process. the main ammonia production is divided into: gas in the pre

16、paration of raw materials; raw materials and synthetic gas purification. crude materials often contain a large number of gas c, is the co due to the ammonia catalyst poison, so the need for purification treatment, usually, the first after a co shift reaction to make it easier to translate into the r

17、emoval of synthetic ammonia and co2 needed to h2. therefore, co conversion of raw materials is both a gas purification process and a feed gas to the gas. finally, the co with a small amount of washing liquid ammonia, or low-temperature method to transform serial methanation removal. transform sectio

18、n refers to the co and water vapor to form carbon dioxide and hydrogen. in the process ammonia plays an important role.utput, all-the-art technology and equipment.at present, the transformation section of the main changes in the use of low-string change process, which is developed in the mid-80'

19、s. change in the so-called string of low-flow changes, such as the b107 is the fe-cr catalyst after the string into the department of co-mo temperature shift catalyst. changes in the string of low-change process, as the catalyst for broad changes to the series, operating conditions there have been l

20、arger. on the one hand into the furnace of the steam to a greater degree than has been reduced; on the other hand, transform the gas content of co also significantly reduced. since the change in the string after a wide catalyst for change, so that the operating system's increased operating flexi

21、bility, so that transform the system easy to handle, but also significantly reduced its energy consumption.principles of technology:co-shift reaction:co + h2o = co2 + h2 + q (1-1)co + h2 = c + h2o (1-2) one response (1) is the main reaction (2) is a side effect, in order to control the reaction to g

22、enerate a product aimed at the direction of the industrial use of the reactor (1-1) has a good catalyst for selective and thus inhibit other side effects from happening. the reaction of water vapor and carbon monoxide is a reversible exothermic reaction, reaction heat is a function of temperature.in

23、 the process of transformation include the following reaction:h2 + o2 = h2o + q1 conditions. pressure: pressure on the balance shift reaction is almost no effect. but the pressure to increase will generate methane and carbon analysis of side effects such as easy. one-on balance, the pressure to do s

24、o. but from the perspective of dynamics, the pressure may increase the response rate. from energy consumption, the pressure is also beneficial. as the dry feed gas moore is less than the number of dry gas conversion moore, therefore, be carried out after the feed gas compression transformation of en

25、ergy consumption, atmospheric pressure than the further transformation of energy consumption at the end of compression. pressure on the value of specific operations, according to the characteristics of small and medium-sized ammonia plant, in particular the process of steam and pressure for the comp

26、ressor section of the rational distribution of pressure. general small-scale ammonia plant operating pressure for the 0.7-1.2mpa, medium-sized ammonia plant for 1.2 1.8mpa. the design of the feed gas from small-scale ammonia plant from steam reforming of natural gas, it is desirable pressure 1.7mpa.

27、2. temperature:changes in the exothermic reaction is reversible. kinetics from the point of view, temperature, the rate constant for the reaction rate increases beneficial, but constant balance with the temperature and smaller, that is, the balance of co content increased, the driving force smaller

28、response, the response a negative rate, the temperature can be seen on both the impact to the contrary. there is therefore the best response for a certain temperature and gas composition of the catalyst, derived from the point of view of the dynamics calculation for -tm =in-tm, te-were the best reac

29、tion temperature and the temperature balance, the best response with the temperature and composition of the catalyst systems vary.    gas than steam:the proportion of water vapor h2o/co generally refers to the ratio of water or steam / dry feed gas. to change the ratio of water vapor in in

30、dustrial transformation in response to the most important means of regulation. increase the amount of water vapor, co increased the rate of transformation of the balance, which will help to reduce the residual co content to accelerate the transformation of the reaction carried out. due to the existe

31、nce of excess water vapor, the catalyst to ensure the stability of the active component fe3o4 not be restored, and analysis of carbon and methane generation, and other side effects occur easily. however, the amount of water vapor in the process of transformation is the most important indicator of co

32、nsumption, to minimize the amount of the economic process of great significance, if the ratio of steam too, will result in increased resistance to the catalyst bed; co stop time, waste heat recovery equipment add to chime in with, and so on, so in the (high) suitable for conversion when the ratio of

33、 water vapor in general: h2o/co = 3 5, by the reaction after the change in gas h2o/co up more than 15, do not have to add steam to to meet the low temperature conversion.process to determineat present, there are changes in technology: the temperature change in the low strings, all low and low techno

34、logy 4. design of the sichuan zigong honghe reference to the chemical production process, the selection process in the low strings. transformed into gas from the furnace into the waste heat boiler, waste heat boiler in the transformation of gas from 920 down to 330 , the waste heat boiler exports by

35、 adding water to make steam vapor than the gas to reach 3-5, after re-entering the change in the gas furnace will be converted in the concentration of carbon monoxide dropped to below 3%. through heat exchangers to convert the gas temperature dropped to about 180 , the furnace will be changed into t

36、he low conversion of carbon monoxide gas content down to below 0.3 percent, from re-entering the methanation section.the main equipment of choicelow-flow changes in the series, the major equipment change in the furnace, the low variable furnace, waste heat boiler, heat exchanger, and so on. change f

37、urnace selection of low-c6 catalyst, a catalyst changes the calculation is too low, the actual amount of 10.59m3. over the choice of equipment is mainly based on the given systems ammonia production capacity, feed gas carbon oxide content as well as the transformation of gas required by the co conce

38、ntration.design of the commentssection natural gas conversion process is the first step in the production of synthetic ammonia, but also a more crucial step, because the normal ability to produce qualified compressed gas, is behind all the processes a prerequisite for the normal operation. it is the

39、refore necessary to control certain conditions, so that the conversion of gas, to meet the requirements of the production process.in this design, on the basis of known natural gas, operating conditions, using a string variable in the process of changing the low road. first of all, changing, low had

40、a balance of materials and energy, on the basis of the calculation, according to the results of the major equipment selection, the final design of the purposes. a total of design in temperature waste heat boiler, the change in the furnace, the main exchangers, heat exchanger water temperature, low-f

41、urnace several major equipment change. due to natural gas conversion process is the section maturity process, more information on references, in the design of the main reference of the "small ammonia plant technology and design manual" and "ammonia technology," these two books. d

42、ue to time constraints, the design may be imperfect, teachers pointed out. thanks!第一章 变换工段物料及热量衡算第一节 中温变换物料衡算及热量衡算1.1已知条件及计算结果：（1）半水煤气的组成（干）表1 半水煤气的组成（干）组 分co2coh2n2ch4o2合 计%8.330.038.022.01.50.2100(标)274.73993.001257.8728.249.656.623310kmol12.26544.33056.15232.5092.2170.296147.768（2）压力进工段煤气压力0.8mpa

43、(表)进工段蒸汽压力为1.0mpa（表）（3）温度进系统半水煤气温度 50进中变炉一段催化剂气体温度 300出系统那个变换气温度 35精炼来循环水温度 84出系统变换气（干）中co含量 3.5%（4）计算基准以1t氨为计算基准年产4万吨合成氨生产能力：日生产量：40000/300=133.337t/d=5.56t/h要求出中变炉的变换气干组分中co小于3.5工艺计算流程图如图1-1-1所示1.2中温变换炉物料及热量计算（1）干变换气量及变换率的计算设氧与氢在变换炉一段催化剂内完全燃烧生成水，由 +2 =2 知，实际参加co变换反应的半水煤气量为 3310-3 =3310-6.62×3

44、=3290.14 （标）co总变换率为 x= 式中 x= =85.41%  则 =3290.14×(1+85.41%×30.18%)=4138.23 （标）co变换总量： 3290.14×30.18%×85.41%=848.05 （标）=37.86kmol变换气中co量 3290.14×30.18%848.05=144.91 （标）=6.47kmol（2）总蒸汽比计算设低温变换炉出口变换气温度为252，平衡温距取36，t252+36288co变换反应式为 co+ 设 a b c d 则 a=30 b=8.3 d=38co反应量 co=

45、30×85.41%=25.623 （标）co100干半水煤气由查小合成氨厂工艺技术与设计手册表4-2-6得288时 =47.39= = =47.39解得 b=39.61 即汽气=39.61：100上式中 为煤气中氨的浓度需总蒸汽量（包括喷的冷凝水量）147.768×39.61%=58.531kmol=1311.09 （标）（3）中变炉一段催化剂层物料及热量计算a入炉蒸汽比（汽气）计算 设co在一段催化剂层转化率60.1%且 在一段催化剂层与氨完全燃烧而生成水，则co反应量为 =30×60.1%=18.03n 100n （干半水煤气）co总反应量 3300×

46、; =596.793n （标）=26.64koml设气体出一段催化剂层温度为460，平衡温距取12，出口气平衡温度为460+12=472由小合成氨厂工艺技术与工艺手册1表4-2-6查得472时 =6.20则 = 将a,c,d及 等代入式得= =6.20解得 b=37.36 即汽：气=37.36：100入炉蒸汽量 3300 =1236.6 （标）=55.206kmol表2 入炉湿气组成组分co2coh2n2ch4o2合计%6.04321.84027.66516.0161.0920.14527.200100(标)274.73993.001257.8728.249.656.621236.64546.

47、62kmol12.26543.33056.15232.5092.2160.29655.206202.974kg539.661241.24112.30910.2535.469.47993.7183842.09b.平衡变换率计算及出一段催化剂层气体组成设460的co平衡变换率为 ，查表4-2-6得460时 =6.85则 = 将入炉气有关组成代入上式得 = 得 =61.34%实际变换率为平衡变换率的 =97.98%出一段催化剂层干气体量 3310+596.7936.62×3=3886.933 （标）出一段催化剂层干气组成表3 催化剂层干气组成组 分co2coh2n2ch4合 计%22.42

48、10.1947.3818.731.28100(标)871.523396.2071841.353728.20049.6503886.933kmol38.90717.68882.20332.5092.216173.524kg1711.92495.26164.41910.2535.463317.30 出一段催化剂剩余蒸汽量1236.6596.793+6.62×2=653.047 （标）=29.254kmol出一段催化剂层湿气组成表4 催化剂层湿气组成组 分co2coh2n2ch4合 计%19.208.7340.5616.041.0914.38100(标)871.523396.2071841

49、.353728.20049.65653.0474539.980kmol38.90717.68882.20332.5092.21629.155202.679kg1711.92495.26164.41910.2535.46524.773842.07c.热量衡算计算co变换反应气体温升入热co反应放热 设气体由300升至460反应取平衡温度380时热效应由小合成氨厂工艺技术与设计手册查图4-2-1得 kjkmol =（44.33017.688）×38700=1031045.4kj 燃烧热 =0.296×427250=126466kj合计为1157511.4kj出热气体温升吸热 设

50、气体温升为 ，气体在平均温度380下查小合成氨厂工艺技术与设计手册图4-6-1图4-6-8计算得平均热容为33.521 kj(kmol·) =202.679×33.521 =6794.003 热损失 =30095.2964kj合计30095.2964+6794.003 热平衡1176834=30095.2964+6794.003 = =160气体出口温度为t=300+160=460气体出口温度为460,与前面假设温度一致。d.一段催化剂平衡曲线计算根据中变炉一段入口汽中蒸汽比（汽气）0.374，由式（4-3-3）计算各温度下的平衡变换率列于下表。表5 各温度下的平衡变换率t

51、,3003203403603804004200.84930.82140.79240.76270.73270.70260.6725t, 4404664805000.64280.61370.58510.5573把干气体组成折算成湿气组成%= =21.83%= =6.04%= =27.66%= =16.01%= =14.57%= =1.09%= =27.33即 a=21.83 b=27.22 c=6.04 d=27.66由表4-4-6查得300时 =39.758用式4-3-2计算得w=39.7581=38.758u=39.758（21.83+27.22）+（6.04+27.66）=1983.83v=

52、39.758×21.83×27.2227.22×6.0423457.64q= =546.71由表中数据作图即得平衡曲线 （见图12-1-1） e最适宜温度曲线计算最适宜温度曲线式（4-4-2）并以b109催化剂的数据进行计算，由于b109催化剂 =16046kal kmol=67156kj/kmol，变换的逆反应活化能 为： = 对于变换反应 =1，则 = + 为反应热，取其平均温度下的值即 由(4-2-2)式算得 =37686kjkmol =67156+37686=104842 kjkmol 最适宜温度计算结果列于表中表6 最适宜温度计算结果0.84930.82140.79240.76240.73270.70260.67250.64280.61370.58510.5573557.4578.0592.1612.2630.4647.5664.7681.9698.9715.9731.4284.430