Nonlinear inferential control of an autonomous periodic fixed-bed reactor

This paper deals with the control of an autonomous periodic fixed-bed reactor, which is called circulation loop reactor (CLR). This process can be described by a distributed parameter system with sustained oscillations. The state variables at some positions of such a process, e.g. the conversion at the reactor exit, may be required to vary in a smooth fashion, which in general is a difficult task due to the process's inherent complex behavior. Here, a straightforward control strategy of the CLR based on direct exit concentration regulation is presented. A relay feedback controller is found to be effective for achieving overall conversion while using relatively small external heating. In order to implement the control scheme without on-line concentration measurement, a nonlinear inferential control concept is adopted. A newly-developed nonlinear distributed parameter observer is used to infer the exit concentration from the temperature measurements at only a few positions. Moreover, an approach based on integrating a disturbance estimator is presented for improving the performance of the observer in the case of unmeasured inlet concentration. It is found that there exist simple determinate relations between the inlet variables or the model parameters and the maximum amplitude or the period of the oscillatory temperature at an axial position for the considered cases. By employing the oscillatory feature of the CLR, a method of estimating the inlet concentration is proposed, and a parameter estimation method based on the least square technique is given to update offline model parameters. It is shown that substantial benefits could be realized using the proposed nonlinear inferential control scheme for the CLR because it can provide excellent disturbance rejection capabilities and strong robustness.     

高硫煤泥燃烧过程中的汞排放特性

通过固定床程序升温汞脱附试验系统对所选高硫煤泥中汞排放特性进行在线监测,并利用热重分析仪对煤泥热解和燃烧特性进行研究,结合试验所得热解和燃烧特性参数,采用分布活化能模型,进行动力学分析。结果表明：煤泥的热解和燃烧过程可分为3个阶段,非等温条件下,随着升温速率增加,热解过程在高温区发生,最大失重率提升,对应峰值温度偏移,产生热滞后,利于挥发分析出;在煤泥热解过程中少量氧气的参与,抑制挥发分的析出,在7% O₂条件下综合热解特性参数值D最大。热解性能随CO₂浓度升高而得到改善;煤泥燃烧性能随升温速率的增加而得到加强,其活化能随转化率变化呈现“U”型趋势分布;煤泥中无机汞化合物主要为HgCl₂、α-HgS、HgSO₄以及硅铝酸盐类结合汞,总汞释放主要范围对应200~600℃;煤泥中汞释放量随O₂浓度增大,CO₂气氛条件下,随着CO₂浓度增加,总汞释放量逐渐增大。     

水稻深床干燥工艺参数对爆腰增率的影响

利用深床干燥试验台，采用二次正交旋转组合设计对辽宁省水稻主栽品种辽粳294进行研究，分析了热风温度、表现风速、谷层厚度对爆腰增率的影响规律，建立了水稻爆腰增率的回归方程，利用贡献率法确定各因素在二次非线性模型中的主次关系，并确定了爆腰增率最低条件下工艺参数的优化组合。     

轴向流固定床反应器内渗流方程的力学分析

根据轴向流固定床反应器内部固定床层中流体的流动特性，建立了渗流模型与渗流基本方程，并对渗透阻力及其他作用力进行了力学分析与讨论。     

固定床反应器中直接法合成甲基氯硅烷

在固定床反应器中,对不同反应压力下直接法合成甲基氯硅烷的原料氯甲烷及硅粉的转化率进行了研究。采用氯原子守恒的方法计算氯甲烷的转化率,并提出对反应后固体残留物进行热解重量分析(TGA)得到硅粉平均转化率的新测量方法。研究表明,在相同反应压力下,原料氯甲烷的转化率和副产物甲基三氯硅烷的选择性随反应时间的变化具有相同趋势。在一定压力范围内,氯甲烷和硅粉的平均转化率均随反应压力的升高而提高,提高反应压力有助于优化反应过程。     

On-Line Prediction of a Fixed-Bed Reactor Using K-L Expansion and Neural Networks

An on-line prediction scheme combining the Karhunen-Love expansion and a recurrent neural network for a wall-cooled fixed-bed reactor is presented.Benzene oxidation in a pilotscale,single tube fixed-bed reactor is chosen as a working system and a pseudo-homogeneous twodimensional model is used to generate simulation data to investigate the prediction scheme presentedunder randomly changing operating conditions.The scheme consisting of the K-L expansion andneural network performs satisfactorily for on-line prediction of reaction yield and bed temperatures.     

Evaluating tar production via the release of volatile matters for H2-rich syngas production

Tar measurement and calculation is crucial for understanding the in-situ tar elimination and hydrogen-rich syngas production during the biomass gasification process. In this study, the method of evaluating tar production was proposed and studied on a two-stage fixed-bed reactor. Two different groups of oxidized and reduced oxygen carriers were investigated for comparison. The collected tar was tested on a gas chromatography–mass spectrometry (GC-MS) system. The types of the tar were all belonged to aromatic hydrocarbons. The H₂ composition in the syngas was over 34% in three reduced-OC conditions. The carbon percentage identified by the GC-MS was at the range of 93.75–95.05 wt%. The average carbon from the char combustion period was 2.85 mmol. The tar yield in the three oxidized-OC conditions was 43 ± 22 mg/g, 53 ± 11 mg/g, and 62 ± 8 mg/g, respectively. The result indicated that the reduced OC had a catalytic effect for increasing the H₂ composition in syngas. On the other hand, the oxidized OC influenced the reactions by providing with lattice oxygen. The evaluation of the produced tar was beneficial for a further understanding of the mechanism for producing the H₂-rich syngas.     

球磨时间对机械化学法NaBr改性飞灰脱汞性能的影响

采用全方位行星式球磨机对燃煤飞灰进行机械化学改性。在固定床反应装置上探究了球磨时间对改性飞灰脱汞性能的影响,并对飞灰改性前后的理化特性和脱汞机理进行了分析。结果表明,在单一机械球磨改性条件下,飞灰的脱汞效率随着球磨时间的增加出现先升高后降低的趋势。这是由于球磨过程中飞灰粒径变小,非晶相程度增加,Hg⁰与飞灰样品接触面积增加,有利于Hg⁰的脱除;但过长的球磨时间会造成飞灰孔隙结构的破坏并发生细微颗粒的团聚,使比表面积降低,不利于Hg⁰的脱除。机械球磨条件下添加改性剂NaBr后,飞灰的脱汞效率显著提升,并随着球磨时间的增加而单调增加,这是由于在机械球磨与NaBr的共同作用下,在飞灰表面产生了较多的羰基、羧基/酯基等活性官能团,同时生成C-Br共价基团,促进Hg⁰的吸附脱除。原始飞灰和单一机械化学改性飞灰对Hg⁰的脱除主要以吸附为主,氧化作用占比较少,约为吸附作用的1/3。机械化学NaBr改性飞灰对Hg⁰的吸附能力和氧化能力均显著提升,且吸附作用和氧化作用占比相当。     

K2CO3对兰炭催化气化特性的影响

在固定床中考察了不同K₂CO₃植入浓度和不同温度条件下兰炭催化气化特性。结果表明，5%的催化剂植入浓度主要起到填充孔隙的作用，当植入浓度增加到10%以后，催化剂发生堆积会使颗粒表面及内部形成较多孔隙。提高气化温度可提高兰炭转化率，超过750℃之后碳转化率增幅减缓，催化剂饱和装载浓度为10%。在颗粒表面和开放孔隙中的高浓度C(O)才具有较高的脱附速率，并提高CO生成速率。在非催化条件下，随着气化的进行CO/CO₂下降，而H₂/(2CO₂+CO)先增后减。在催化条件下，H₂/(2CO₂+CO)稳定在1.5～1.7。催化剂兰炭样品中出现了K₂Ca(CO₃)₂双金属碳酸盐、K₂O、KO₂等活性组分，并随催化剂植入浓度的增加而增加。催化剂植入浓度的增加会导致失活现象加重，但兰炭在750℃条件下气化1 h 催化剂没有完全失活。     

Fe2O3对甘氨酸热解特性及氮转化的影响

选用污泥中典型氨基酸-甘氨酸（Gly）为研究对象,利用差式热值分析-质谱联用技术（DSC-MS）和固定床实验研究了Fe₂O₃对甘氨酸热解特性、NO _x 前驱物生成规律以及氮转化特性的影响。结果表明：热解特性实验中,由于Fe₂O₃将Gly的第一热失重阶段一分为二,导致其热解过程由2个阶段增至3个;Fe₂O₃使Gly热解起始温度及气体析出温度降低50℃,并通过促进半焦的二次裂解反应使Gly失重率增加23%。与Fe₂O₃对Gly热解过程的影响一致,Fe₂O₃将含N气体析出过程同样分成3个独立的阶段。固定床实验中,在Fe₂O₃/N=0.5时,Fe₂O₃最大程度地抑制了NO _x 前驱物（NH₃和HCN）析出,使其减少30%。由于Fe₂O₃促进肽脱水缩合、环化和芳香化反应,使得更多P-N、N-5和N-6固定在半焦中,半焦氮残留率增加5%。