轴径向型氨合成塔的数学模型及工艺优化研究

运用氨合成化学反应本征动力学方程,建立了轴径向型氨合成塔拟均相一维的催化床层内氨浓度和反应温度分布的数学模型。利用正常生产运行的操作数据反算得到了各段催化床层的催化剂活性系数;逐一对单元工艺操作条件进行了优化,模拟计算出系统压力随氨合成塔工艺操作条件变化的情况,从中确定出一组工艺操作条件的优化值;通过实际生产运行,对优化前后氨合成塔工艺操作数据进行了对比,结果实明,生产操作工况良好。     

Evidence for bulk-phase nitrogen dissolution in iron in catalytic ammonia synthesis

Experiments were carried out in which the reactants, nitrogen and hydrogen were admitted to a fixed bed of triply-promoted iron catalyst in the form of concentration step-functions. Temperature was about 400°C, and total pressure was 2.38 MPs. The bed was stabilized with equimolal flows of hydrogen and nitrogen and then stepped up to pure hydrogen or down to pure nitrogen. From the rate of ammonia production, catalyst properties, and bed temperature behaviour, it was inferred that nitrogen is dissolved by the bulk phase of the iron catalyst. This result has important implications for a general model of transient and forced cyclic operation of catalyst beds.     

A110-5Q 型氨合成催化剂在双层并流合成塔中的使用

介绍了A 11025Q 型氨合成催化剂的装填、升温还原及使用情况。装填该催化剂后, 在合成塔有缺陷的情况下仍创出了合成氨产量记录, 表明该催化剂性能优良、活性好、生产强度大,在双层并流合成塔的应用是成功的。     

一轴二径大型氨合成塔的应用

介绍了一轴二径大型氨合成塔的压力确定、结构特点、工艺流程、催化剂装填与升温还原等情况。通过生产应用,证明该国产化氨合成塔具有操作稳定、负荷调节裕度大、氨净值高、床层阻力小等特点。     

氨合成铁、钌催化剂联用工艺

在实验室和工业侧线装置上考察了FA-Ru型氨合成钌催化剂与铁系A202型催化剂的性能差异,以及铁催化剂和钌催化剂联用工艺与单铁催化剂工艺对氨合成效果的影响。结果表明,FA-Ru催化剂在低温（375～425℃）、低压（10～15 MPa）、低氢氮比（R=1.5～2.3）和合成气高氨浓度（10%～16 %,体积分数）条件下,活性比A202催化剂相对提高44%～75%。铁催化剂与钌催化剂混装工艺的氨合成率随着钌催化剂装量的增加而增加,比单铁催化剂的氨合成率提高24.5%～44.8%。铁催化剂串钌催化剂工艺的氨合成率同样随着钌催化剂装量的增加而增加,比单铁催化剂的氨合成率提高27.7%～58.8%。对于铁、钌催化剂联用的氨合成工艺,在实验条件下,当钌催化剂用量达铁催化剂用量1/2以上时,催化剂的最高活性点温度降至400℃。工业侧线实验表明,FA-Ru催化剂在13.0 MPa、10000～15000 h-1条件下的氨合成率可达到铁催化剂在相同空速、26 MPa 压力下的水平。根据不同工况,铁催化剂串钌催化剂生产工艺比单铁催化剂生产工艺氨合成率可相对提高43%～56%。     

三套管连续换热式氨合成塔催化床的二维模型

本文建立了三套管连续换热式氨合成塔催化床的二维数学模型,用逸度表示反应速率,求得了床层内轴向和径向温度及浓度分布的数值解。模拟计算结果表明,由于冷却段催化床内插冷管,冷管内与床层内的温差较大,使床层的径向存在较大的温差。采用一维模型进行计算与实际情况存在一定的偏差,这一点在反应器的设计和催化剂的还原中是不容忽视的。     

氨合成塔的优化设计

通过数学模拟计算,定量地分析和讨论了三套管氨合成塔在一定的设计压力、热点温度和氢氮比条件下,催化床进口氨含量、惰气含量、温度、空速和催化荆活性系数对氨合成反应的影响以及这些因素之间的内在关系,提出了在最优调节参数下实现氨合成塔优化操作和确定较适宜工艺设计参数的理论依据和方法。结果表明,催化床进口温度是实现氨合成塔优化操作的最优调节参数。     

甲烷化催化剂的水洗处理

介绍中石油大庆石化公司化肥厂合成氨装置甲烷化催化剂水洗情况.运行结果表明,水洗后催化剂床层压差明显降低,活性没有受到影响.     

A301催化剂用于日产千吨径向氨合成塔操作工况的模拟及优化

采用拟均相一维数学模型，模拟计算了国内较具代表性的3种日产千吨径向氨合成塔操作工况，得到了各段催化床层的催化剂活性校正系数，在此基础上，对这3种氨合成塔在分别装填A110、IC174-I、A301催化剂的操作条件及各段催化床的装填量进行了优化，结果表明，通过对现有塔的操作条件进行优化或调整各段催化床体积，可以达到提高产量的目的。A301催化剂的效果最为显著，可提高氨产量6%～9%，副产更多蒸汽，这一结果表明，引进的大型合成氨厂第二次改造和催化剂更换采用A301型催化剂可以达到节能降耗和增产的目的。     

如何实现氨合成塔的优化操作

采用数学模拟的方法 ,从理论上分析和讨论了连续换热三套管并流式氨合成塔在其催化剂有效使用期内 ,随着催化剂活性系数的逐渐衰减 ,分别调节催化床进口温度或进口氨含量、惰气含量和空速等四个设计参数 (单参数 ) ,观察其对出口温度和氨产量的影响 ,并与最佳出口温度和氨含量进行了比较。计算结果表明 :当进口氨含量或惰气含量为调节参数时 ,氨产量均不能达到设计的生产能力 ;而调节进口温度或空速时 ,氨产量均可超过设计的生产能力 ,其中 ,前者超过的幅度较大且能耗较小 ,可选择为实现氨合成塔优化操作的最佳调节参数     

NC型1200mm氨合成塔内件特性及系统配置的优化设计

NC型12 0 0mm氨合成塔内件采用一轴二径绝热反应形式 :轴向冷激采用菱形分布器结构 ,两段径向采用鱼鳞筒或径向流分布器 ,使气流呈辐射状进入催化剂床层 ,路径缩短 ,床层阻力降低 ,特点是对三段催化剂床层进行冷激控制 ,使其在最佳温度范围内反应。在系统中采用气体分流进塔设计 :将水冷出口气体进氨分改为先进冷交 ;系统设置新鲜气氨冷器 ;对系统的主要辅助设备预留了较大的富裕量     

连续换热式氨触媒床轴向最佳温度的分布

通过建立数学模型和编制电算程序计算，作出了连续换热式氨合成塔内最佳温度Ｔｍ和最佳浓度ｙＮＨ，ｍ沿触媒床高度ｌ分布的曲线Ｔｍ—ｌ和ｙＮＨ３，ｍ－ｌ，比Ｔ—Ｙ图更能直接、明确地反映床层轴向实际温度和氨浓度与最佳温度和氨浓度之间的偏差分布规律．     

Analysis of the Coupling of HC–SCR by Ethanol and NH3–SCR on Real Engine Emissions

Selective catalytic reduction by ethanol on silver-based catalysts was proved to be very effective to abate the nitrogen oxides emitted at the exhaust of an automotive engine. Moreover, the selectivity to ammonia of this reaction may be exploited to further enhance the NOx reduction using a dedicated transition metal exchanged zeolite catalyst. This coupling between HC– and NH₃–SCR is called Dual SCR. In order to control the silver-based catalyst efficiency via ethanol injection, a NOx sensor is located downstream of it, as usually done for urea–SCR on series vehicles. Furthermore, based on the cross-sensitivity of this NOx sensor, large amounts of ammonia were estimated that would help to reduce the remaining NOx on the zeolite based catalyst. However, when measured by FTIR technique, the concentrations of ammonia produced by the HC–SCR catalyst were surprisingly not as high as expected, while large amounts of acetaldehyde were detected and, in a lesser extent, formaldehyde and hydrogen cyanide. NOx were partly reduced over the iron-exchanged zeolite catalyst, improving the overall deNOx efficiency by up to 15 points, while acetaldehyde to formaldehyde ratio reversed and ammonia concentration remains unchanged. The cross-sensitivity of the NOx sensor was further investigated on synthetic gas bench. If its partial dependence on the ammonia concentration is rather well known, the influence of aldehydes and hydrogen cyanide in presence of ammonia had not yet been investigated. The NOx sensor’s signal remains unchanged whatever the aldehydes concentration and a strong sensitivity to the hydrogen cyanide was highlighted.     

660MW燃煤机组SCR流场模拟优化与喷氨优化运行

以某电厂660 MW亚临界燃煤机组SCR烟气脱硝系统为研究对象,对SCR反应器内烟气流动以及喷氨分布均匀性进行数值模拟研究。通过对比首层催化剂前烟气速度分布及NH_3浓度分布,研究了SCR反应器内均流部件对烟气流场均匀特性的影响,并且在数值模拟的基础上对喷氨方式进行了优化调整研究。研究结果表明:优化调整烟道内均流部件对速度、浓度均匀性有显著改善作用;通过分析流场不均匀性得到的分区喷氨方法能够进一步优化NH_3在烟道中分布;现场试验验证了调节喷氨格栅阀门可降低SCR反应器出口NO_x浓度。本文研究可为燃煤机组SCR系统导流板优化及实际电厂喷氨优化调试提供参考。     

An NMR Imaging Study of Steady-State and Periodic Operation Modes of a Trickle Bed Reactor

NMR imaging has been applied to study the steady-state and the periodic operations of a functioning trickle bed reactor. It has been revealed that under conditions of the continuous supply of a liquid reagent to the catalyst bed, the bed was mostly filled with the liquid phase and was characterized by the uniform and stationary distribution of a liquid phase, whereas under conditions of the periodic supply of a liquid reagent to the catalyst bed with the same liquid flow velocity the bed was mostly dry and was characterized by a non-stationary distribution of the liquid phase. The oscillations of the liquid phase content within the bed, corresponding to the modulated liquid flow, have been observed. It has been shown that performing the hydrogenation reaction in a trickle bed reactor under conditions of the periodic supply of a liquid reagent to the catalyst bed leads to the intensification of the hydrogenation process. It becomes apparent in the significant increase of the temperature of the catalyst bed as well as in the increase of the conversion degree in the regimes under forced time-varying liquid flow rates in comparison to the steady-state regime of the reactor operation.     

三段串联绝热轴向氨合成塔的模拟计算和设计优化

提出三段轴向氨合成反应器的数学模型和设计优化方法，对三段轴向氨合成反应器进行模拟计算。同时计算了操作压力分别为１５７８，１５０，１００，７．５ＭＰａ时，在三段串联绝热轴向反应器中满足日产１０００ｔ氨所需的最少催化剂用量。     

Effect of flow rate on temperature in a Bi-P-O catalyst bed: Global enhancement by forced flow rate cycling

Effects of flow rate on reactivity of oxidative coupling of propylene with Bi₂O₃-P₂O₅ were investigated by reaction experiments and by model calculations. Although the conversion is lower at the higher flow rate because of the shorter contact time, there may be a case that when the temperature in the catalyst bed increases and it causes the reaction rate to accelerate. It is thought that the heat was accumulated in the catalyst bed when heat generation rate was much faster than the heat removal rate. The simple calculation based on the assumption of the pseudo-homogeneous phase indicated that the heat was not accumulated at the higher flow rate by the steady-state operation. However, heat wave emerged and accelerated the reaction after the flow rate was changed from the lower flow rate to the higher flow rate. Forced flow rate cycling, an operation where flow rate is changed periodically, was experimentally conducted. The time averaged conversion was slightly enhanced compared with the result from the steady-state operation at the flow rate of . In addition, even in the steady-state operation under the condition where a non-adiabatic reactor packed with only catalyst was used, the conversion and the yield of benzene became higher at the higher flow rate because of the temperature increase in the catalyst bed.     

Operation of Fixed‐bed Bioreactor for Polluted Surface Water Treatment

Abstract

Dissolved organic matters and ammonia nitrogen are serious contaminants of surface water in Taiwan. These contaminants can interfere with the water treatment process and cause biological instability in the finished water. One solution is to employ a biological treatment stage prior to the conventional water treatment process. A continuous flow biological filter packed with reticulated PU foam was used to remove ammonia nitrogen and organic materials before the conventional water treatment practice. The effect of its operation mode, namely, empty bed contact time (EBCT) and backwash, on the removal efficiencies of ammonia and organic matter was examined. The results suggested that ammonia nitrogen and organic nitrogen can be effectively removed by controlling the operation mode of the biological fixed bed. Efficient ammonia nitrogen removal was achieved upon the combination of the backwash mode with short EBCT or extended EBCT without the backwash. Efficient organic nitrogen and DOC removals were observed at short EBCT without the backwash. This study provides insights into the function of biofiltration, which benefits the design of a fixed‐bed bioreactor for the treatment of polluted surface water.     

合成氨变换出现的问题及处理

本文针对在实际生产过程中出现的一些问题进行处理。合成氨变换装置在接气和正常生产时,变换催化剂床层出现不同程度的超温现象,严重影响变换装置的安全平稳运行,因此在变换炉前增加放空管线,并在正常生产时增加气化水汽比,使催化剂床层温度控制在正常范围内。对粗煤气做带液处理时,由于V1501液位较高,容易将水带入变换炉使催化剂粉化,因此在V1501液相新增管线去气化澄清池,带液问题得到有效控制。由于系统中氨含量较高, E1506容易形成碳铵结晶,针对这个问题将去气化磨煤的尿素废液改成去气化除氧器,同时对内漏的尿素废液换热器进行更换。经过改造确保了装置平稳运行。     

A301催化剂等压合成氨的可行性

原粒度A30 1催化剂在大型合成氨厂实际工况条件下的工业旁路试验结果表明 :在 7.0～ 7.5MPa等压合成氨工艺条件下 ,A30 1催化剂的氨净值为 10 %～ 12 % ,在 8.5MPa或 10MPa微加压合成氨工艺条件下 ,氨净值可达 12 %～ 15 % ,可以满足合成氨工业经济性对氨净值的要求 .因此采用A30 1催化剂实现等压或微加压合成氨是可行的 ,并可获得显著的经济效益