Carbon dioxide hydrogenation to methanol has the potential to play a pivotal role in addressing environmental and energy challenges and the transition toward a more sustainable future. This study explores the synergistic effects of circulating fast fluidization with in-situ sorption and condensation at low pressures to enhance the hydrogenation of carbon dioxide to methanol by mitigating its thermodynamic and kinetic limitations. It analyzed the single bed and multi-stage circulating fast fluidized bed reactor configurations. Conditions for source of carbon converted to methanol are developed for various possibilities of methanol formation as an integral part of the analysis process, providing a conceptual structure for the analysis of the results. In-situ sorption has created fascinating phenomena in the single bed configuration such as two distinct regions separated by a transition region. The transition region can have a significant impact on the contrasting transformations seen in the first and third regions. This study offers a comprehensive analysis of the intricate behaviors that encountered in these regions. It is believed that this is the first time a transition region has ever been observed. The study revealed that the single-bed configuration with in-situ sorption can achieve an exit carbon conversion to methanol of 73.07%, while the four-bed configuration with in-situ condensation can achieve 44.87%. Their combined effects can reach up to 96.85% in the multi-stage configuration. The multi-stage configuration also exhibited phenomenon of waves of maxima extending along the length of reactor. In addition, the critical point E can appear twice in the same bed.

The theme of this study is to explore the enhancement of carbon conversion to methanol by introducing the concept of circulating fast fluidization coupled with in-situ condensation (IC) and in-situ sorption. According to the best of our knowledge, this is the first time a novel multi-stage circulating fast fluidized bed reactor (CFFBR) is implemented in methanol synthesis. The validity of the reactor and thermodynamic models was verified by industrial and experimental data and good agreement is found. It has been found that the combination of IC and in-situ sorption with the short reactor bed policy achieves remarkable improvement in carbon conversion to MeOH (99.20%). The simulation results indicate that considerable improvement in conversion to MeOH (88.02%) can be achieved by the single bed CFFBR configuration with the in-situ sorption. For the same reactor condition, the IC achieves 59.95% conversion to MeOH. It is apparent that sorption is more pronounced than that of IC. Also, it is found that a large multi-stage configuration with IC can greatly improve the carbon conversion to MeOH (98.24%). It has been observed that excessive sorption inhibits the WGS and increases the accumulation of CO, leads to a considerable drop in carbon conversion to MeOH. Two critical points were identified and used to determine the instantaneous equilibrium of the WGS and the beginning of the total carbon conversion to methanol. The results of this study reveal that fascinating phenomena appear when the in-situ sorption with highly selective water adsorbent of zeolite-4A particles is implemented in the single bed CFFBR.

In this study, the influence of distribution of ammonia feed along the height of a fixed bed membrane reactor (FBMR) for ammonia decomposition to hydrogen is investigated to understand the leverage of this approach. A rigorous heterogeneous model with verified kinetics is implemented to simulate the reactor. The simulation results indicate that the application of a distributed ammonia feed with equal distribution of injection points resulted in a 17.45% improvement in hydrogen production rate at a low temperature of 800.0 K over a FBMR without feed distribution. In the parameter space of this study, it has been shown that the ammonia conversion is sensitive to the number of distribution points and has an optimal value. It is found that the implication of the optimum number of injection points can substantially reduce the length of the reactor by 75.0% to achieve 100.0% ammonia conversion. The hydrogen reversal permeation phenomenon is observed at a low pressure and the upper part of the reactor. A novel configuration of a FBR and a FBMR with feed distribution is proposed for efficient production of ultra-pure hydrogen at a relatively low pressure. The critical reactor length ratio has been provided for this configuration. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

A heterogeneous mathematical model is used to simulate a cascade of multi-stage fixed bed membrane reactors (MSFBMR) for the decomposition of ammonia.The numerical results show that a single fixed bed membrane reactor (FBMR) exhibits a poor performance and limited by the kinetics to give 29.49% exit ammonia conversion, whereas efficient seven multi-stage beds achieve 100% ammonia conversion.An effective hydrogen permeation zone has been identified by a critical point.It is observed that the locus of the total inter-stage heating load assumes a maximum inflection point.The results show that the multi-stage fixed bed membrane reactors configuration has many benefits and can the future generation of reactors for production of hydrogen.

The concept of circulating fast fluidization with in-situ water removal using zeolite-4A particles is introduced to the methanol synthesis process. The mathematical model of a circulating fast fluidized bed reactor (CFFBR) is validated by an actual industrial plant data. Also, the industrial plant feed data is used to test the performance of a bubbling fluidized bed reactor (FBR). The CFFBR with varying adsorbent compositions is investigated. The system exhibits optimum conditions at a low feed temperature of 201.75 degrees C due to water removal and thermodynamic equilibrium shift. The methanol production has substantially increased about 14-folds. The increase of the adsorbent mass concentration > 50.0% has a little effect on the maxima due to the total conversion of carbon. It is interesting to note that feeds rich in CO2 and lean in CO are susceptible to a significant improvement of methanol production. The sensitivity analysis shows that the increase of H-2 in the feed decreases CO formation and consequently increases the carbon conversion to methanol. Moreover, the pressure is more effective at low ranges due to a high carbon conversion. The high efficiency shown by the CFFBR in this study suggests a promising application of these reactor generations in the methanol industry.

A rigorous heterogeneous mathematical model is used to simulate a cascade of multi-stage fixed bed membrane reactors (MSFBMR) with inter-stage heating and fresh sweep gas for the decomposition of ammonia to produce high purity hydrogen suitable for the PEM fuel cells. Different reactor configurations are compared. The comparison between a single fixed bed reactor (FBR) and a single fixed bed membrane reactor (FBMR) shows that the FBMR is superior to the FBR and gives 60.48% ammonia conversion higher than the FBR. However, 20.91% exit ammonia conversion obtained by the FBMR is considered to be poor. The FBMR is limited by the kinetics at low temperatures. The numerical results show that the MSFBMR of four beds achieve 100.0% ammonia conversion. It was found that the membrane plays the prime role in the displacement of the thermodynamic equilibrium. The results also show that, a linear relationship exists between the number of beds and the feed temperature and a correlation has been developed. A critical point for an effective hydrogen permeation zone has been identified. It is observed that the diffusion limitation is confined to a slim region at the entrance of the reactor. It is also observed that the heat load assumes a maximum inflection point and explanations offered. The results show that the multi-stage configuration has a promising potential to be applied successfully on-site for ultra-clean hydrogen production.

Sustainable Development (SD) is essential for modern economy. Sustainable Development Engineering (SDE) is a subsystem of SD and concentrates on the engineering sides of SD. Environmental Engineering (EE) is also essential for clean modern industry. EE is necessary for SD but is not sufficient, in order to make it sufficient the feedstock must be from Renewable Raw Materials (RRMs) sources. SD is formed of the sub-systems SDE, EE and RRMs. In this paper membrane catalytic reactors are used to achieve Maximum Production and Minimum Pollution (MPMP) by removing hydrogen from dehydrogenation side. The efficiency increases when a hydrogenation reaction is taking place in the other side of the membrane. This paper is addressing a practical case for this behavior giving MPMP which is necessary but not sufficient for sustainability. The further step to make it sufficient is the use of feedstock from RRMs which is not addressed in the paper. It is shown that the counter-current process is more efficient than the co-current one. This investigation and conclusions are obtained by reliable mathematical modeling, numerical solution and computer simulation of the model differential equations. More difficult ones for the Countercurrent case.

An experimental and simulation study has been carried out for the boiling temperature chlorination process of ethylene-to-ethylene dichloride in a gaslift reactor. A substantial improvement in the reactor performance is observed when perforated plate spargers are used compared to nozzle spargers. The backflow cell model is validated with experimental data and is observed to correctly predict the reactor performance in the range of experimental conditions investigated. The model has been utilized to investigate the effects of some important design (height to diameter ratio) and operating (feed ratio, top pressure) parameters on the performance of the reactor. The results suggest that tall systems with excess ethylene favor the conversion of chlorine.

The two-phase model with verified reaction kinetics has been implemented to study numerically dimethyl ether (DME) production in a novel multi-stage fluidized bed catalytic reactor. The single-bed configuration results show that the bifunctional catalyst composition [CuO-ZnO-Al2O3/FIZSM-5] has a pronounced impact on enhancing the reactor performance. Also, the simulation results indicated that the two-bed configuration gives a substantial enhancement of DME yield of 32.67% compared to the single-bed configuration. This yield improvement is also accompanied by significantly improved DME selectivity of almost 100%. The complex interactions of the bifunctional catalyst composition, feed composition and multi-stage configuration play a central role in the extent of the synergy. Interesting two types of maximum phenomena are observed and explanations have been offered. It seeing that synergistic effects have kinetics and thermodynamic strong impact on the development of these phenomena. The loci of these maxima are significant for optimal design and control of multi-bed configurations. It appears that application of multi-stage fluidized bed catalytic reactors is highly promising in DME industry.

In this short communication, the impact of the influence of a dynamic membrane on a bioreactor forced by high amplitude oscillations is investigated. The chaotic state of the reactor bifurcates to unprecedented complex dynamics. Very interesting exotic geometrical structures embedded in a high dimensional phase space are developed. Despite the complexity of the dynamics of this system, it can produce an increase of average ethanol yield up to 19.62% compared to unforced system.

The main indication for cytologic study of the liver is the evaluation of mass-forming lesions, either symptomatic or incidentally discovered. Fortunately, recent major significant progress in cutting-edge imaging methods is shifting the spectrum of cytologic diagnostics toward smaller lesions, which are very often challenging (Wee, 2011). The convenience of relatively easy fine needle aspiration (FNA) procedures with high diagnostic accuracy and low risk for complications has made cytologic examination of primary and metastatic neoplasms in the liver generally well accepted as a first line diagnostic modality (Chhieng, 2004; Kuo et al., 2004; Wee, 2005; Pupulim et al., 2008; Jenssen and Dietrich, 2009). Furthermore, for most patients, treatment (including major surgery or chemotherapy) may be safely instituted based on the diagnosis of a malignant neoplasm in FNA, without obligatory histologic confirmation. In cases of metastatic disease, the availability of diagnostic cytologic material to determine predictive markers becomes progressively more significant. Liver FNAC is a safe technique with a low rate of serious complications, mostly bleeding or infection

Modeling and numerical simulation are implemented to investigate the influence of membrane excitations on the production of bioethanol in a forced fermentor. Three well developed attractors in the frequency locking, quasi-periodic and chaotic regions are subjected to membrane excitations. Two membrane configurations are employed for each case: the shock type and the linear dynamic membranes. It is interesting that all membrane configurations exhibit wealthy regions of complex dynamics and very beneficial to the fermentor performance. The simulated results reveal various fascinating phenomena such as hyperchaos, chaos and large bubble windows. It was shown that the chaotic regions are the attractive and best potential regions for the implementation of the membrane excitations. It is interesting to note that when the shock type and linear membranes are imposed on chaotic regions, the hyperchaotic attractors arise and have substantial impact in increasing the average ethanol yield to 18.98% and 19.29%, respectively. It is obvious that the linear dynamic membranes are superior to the shock type membranes with respect to the bioreactor performance. The bubble windows show an incomplete odd sequence of bubble birth of 1, 3 and 5 bubbles.

The production of hydrogen and syngas from heptane at a low temperature is studied in a circulating fast fluidized bed membrane reactor (CFFBMR). A thin film of palladium-based membrane is employed to the displacement of the thermodynamic equilibrium for high conversion and yield. A mathematical model is developed to simulate the reformer. A substantial improvement of the CFFBMR is achieved by implementing the thin hydrogen membrane. The results showed that almost complete conversion of heptane and 46.25% increase of exit hydrogen yield over the value without membrane are achieved. Also a wide range of the H2/CO ratio within the recommended industrial range is obtained. The phenomena of high spikes of maximum nature at the beginning of the CFFBMR are observed and explanation offered. The sensitivity analysis results have shown that the increase of the steam to carbon feed ratio can increase the exit hydrogen yield up to 108.29%. It was found that the increase of reaction side pressure at a high steam to carbon feed ratio can increase further the exit hydrogen yield by 49.36% at a shorter reactor length. Moreover, the increase of reaction side pressure has an important impact in a significant decrease of the carbon dioxide and this is a positive sign for clean environment.

BACKGROUND:Liver cytology is indicated and requested for evaluating hepatic masses in symptomatic or serendipitous cryptic discovered lesions.OBJECTIVE:To determine the cytomorphological patterns of hepatic lesions identified among a group of Sudanese patients.MATERIALS AND METHODS:This is an analytical descriptive hospital-based study included 165 patients undergoing ultrasound-guided fine needle is an aspiration cytology (FNAC)for hepatic lesions, at Al-Amal Military Hospital and Khartoum Teaching Hospital in Khartoum, Sudan. Clinical data were reviewed. Air dried Diff Quick stained smears were grouped into unsatisfactory samples, benign lesions, and malignant neoplasms.RESULTS:Our population were consisted of 35 (21.2%) females and 130 (78.8%) males, with a male to female ratio 3.7:1 and an age ranged between 47 to 80, and a mean age 57±7. Of 165 cases, 57 (34.5%) were benign, no atypia were noticed, 101 (61.2%) were malignant. Most investigated patients were found to have metastatic lesions.CONCLUSION:FNAC is a useful tool for investigating hepatic lesions.

A rigorous mathematical model is implemented to simulate multistage circulating fast fluidized bed membrane reformers (CFFBMRs) for production of ultraclean hydrogen and a high-grade syngas. Discrete physically well-mixed catalysts are employed in this study. It has been shown that enhancement of the water-gas shift reaction (WGS) by addition of CO in the feed coupled with the heat release from the partial oxidation reactions substantially improved the total H-2 yield by 27.60% in the first CFFBMR1. At the best operating conditions, it was found that the total H-2 yield is significantly increased by 48.75% in the first CFFBMR1 and by 59.66% in the second CFFBMR2. The simulation results show that CO2 concentration can be reduced by 96.39% to a very low level. The results also reveal that the heat integration and energy saving can be realized through coupling endothermic and exothermic reactions reinforced by catalyst patterns.

The performance of multi-stage circulating fast fluidized bed membrane reformers (CFFBMRs) for production of ultraclean hydrogen is investigated in comparison to a single circulating fast fluidized bed membrane reformer (CFFBMR). The two-stage reformer configuration gives significant increase in the methane conversion of 27.46% and ultraclean hydrogen yield of 29.61% compared to the single CFFBMR. The concept of the multi-stage short reformers policy is introduced. Impressively, substantial increase of ultraclean hydrogen yield of 83.91% is achieved.

Simultaneous production of hydrogen and syngas from the catalytic reforming of n-heptane in circulating fast fluidized bed reactors (CFFBR) and circulating fast fluidized bed membrane reactors (CFFBMR) is investigated. This paper presents modeling and simulation approach for the analysis of these reformers. Complete conversion of heptane (100%) is attained at high steam to carbon feed ratios and shorter reactor lengths by both configurations. However, the CFFBMR is very efficient in hydrogen production and can produce exit hydrogen yield up to 473.14% higher than the CFFBR. It was found that operating the CFFBMR at the optimal conditions results in a minimum value of hydrogen to carbon monoxide ratio (H2/CO) within the recommended practical range for the syngas used as a feedstock for the gas to liquid processes (GTL). The results of the sensitivity analysis conducted for the CFFBMR has shown that the reaction side pressure and the feed temperature have significant effects on increasing the heptane conversion (up to 100%) and the temperature effect is stronger than the reaction side pressure effect. Considerable improvement in the hydrogen to carbon monoxide ratio (H2/CO) has been achieved by increasing the reaction side pressure, while the high feed temperature has negative effect on this ratio. It seems that the practical range of H2/CO ratio can be achieved by controlling the reformer length and the right combinations of the operating conditions.

Oxidative reforming of methane for efficient production of hydrogen in a circulating fast fluidized bed reactor (CFFBR) at low pressure and oxygen distribution has been simulated and evaluated. It has been found that the oxidative reforming of methane is inexpensive alternative route to the conventional steam reforming of methane processes. Also, the potential application of in situ heat integration in the CFFBR is very promising for energy savings. A comparison between co-feed and oxygen distribution configurations is investigated. The performance of the CFFBR with co-feed configuration is profoundly affected by the development of hot spot temperatures along the length of the reactor. The distribution of oxygen mitigates the temperature along the length of the reactor and eliminates the development of hot spot temperatures and reactor thermal runaway. The results show that the combination of oxygen distribution with part of oxygen directly fed into the reactor is efficient configuration for production of hydrogen and produces almost 100% conversion of methane and high yield of hydrogen up to 2.351 at 70% of the dimensionless reactor length. The sensitivity analysis shows that careful selection of the operation conditions is necessary for best reactor performance.

In this paper, we present mathematical modeling and numerical simulation tools in searching the high parameter space of steam reforming of heptane for the key design parameters, which have the potential to give high heptane conversion, high hydrogen yield and hydrogen to carbon monoxide ratio within the industrial limits for the syngas used as a feedstock for the gas to liquid processes (GTL). The system under consideration is the novel circulating fast fluidized bed membrane reactor (CFFBMR). The simulation results show that the hydrogen membrane has a significant role in the displacement of the thermodynamic equilibriums of the reversible reactions and production of ultraclean hydrogen, which can be used as a fuel for the fuel cells. Also the results of the sensitivity analysis show that the best performance of the CFFBMR can be obtained by a proper selection of combination of several parameters of high feed temperatures, high steam to carbon feed ratios, high reaction side pressures coupled with a large permeation area of a composite thin film membrane. These parameters are interacting in a very complex manner to give 100% conversion of heptane and 496.94% increase in hydrogen yield compared to the reformer without hydrogen membrane. It was found that under these selected operating conditions a low H2/CO ratio of 1.15 is achieved satisfying the practical recommended industrial range.

Modeling and simulation of circulating fast fluidized bed reactors (CFFBR) and circulating fast fluidized bed membrane reactors (CFFBMR) for hydrogen production by oxidative reforming of methane are presented in this paper. The results show that the CFFBR suffers from serious problems of hot spot temperatures. The combined effect of the oxygen distribution and the hydrogen membrane in the CFFBMR eliminates the hot spot temperatures and the danger of the reactor thermal runaway and mitigates nicely the temperature along the length of the CFFBMR. The investigation shows that the oxidative reforming of methane in the CFFBMR with oxygen distribution is cost-effective and inexpensive alternative route to the conventional steam reforming of methane processes due to the in situ heat integration of exothermic and endothermic reactions. The key role of the design parameters on the performance of the reactors are recognized through sensitivity analysis. The simulation results indicate that almost complete conversion of methane (99.99%), high exit hydrogen yield of 3.00 and low exit temperature of 569.8 degrees C are obtained by proper selection of design parameters of the CFFBMR with oxygen distribution. This achievement occurs at low feed temperature of 350.0 degrees C, which does not have destructive effects on the catalyst, reactor and membrane. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.