Fuel Processing Technology (v.88, #5)

Production of biodiesel from waste fryer grease using mixed methanol/ethanol system by Titipong Issariyakul; Mangesh G. Kulkarni; Ajay K. Dalai; Narendra N. Bakhshi (429-436).
Transesterification of waste fryer grease (WFG) containing 5–6 wt.% free fatty acid (FFA) was carried out with methanol, ethanol, and mixtures of methanol/ethanol maintaining the oil to alcohol molar ratio of 1:6, and initially with KOH as a catalyst. Mixtures of methanol and ethanol were used for transesterification in order to use the better solvent property of ethanol and rapid equilibrium using methanol. Formation of soap by reaction of FFA present in WFG with KOH instigated difficulty in the separation of glycerol from biodiesel ester. To untangle this problem, two-stage (acid and alkali catalyzed) method was used for biodiesel synthesis. More than 90% ester was obtained when two-stage method was used compared to ∼ 50% ester in single stage alkaline catalyst. In the case of mixed alcohol, a relatively smaller amount of ethyl esters was formed along with methyl esters. Acid value, viscosity, and cetane number of all the esters prepared from WFG were within the range of the ASTM standard. Esters obtained from WFG showed good performance as a lubricity additive.
Keywords: Biodiesel; Lubricity; Transesterification; Waste fryer grease;

Behaviors of coke deposition on SAPO-34 catalyst during methanol conversion to light olefins by Guozhen Qi; Zaiku Xie; Weimin Yang; Siqing Zhong; Hongxing Liu; Chengfang Zhang; Qingling Chen (437-441).
The deposition of coke on SAPO-34 during methanol conversion to olefins at temperatures of 623–823 K was observed to be fast initially but moderate in the later stage. Micropores are blocked badly at coke contents of above 4 wt.%. The coke deposition influences olefins selectivity significantly and selectivities of ethylene plus propylene reach maximum at a coke content of about 5.7 wt.%. The coke formation can be attenuated by the presence of water, but the effect of water weakens gradually with the progress of the reaction. A model relating the coke content over SAPO-34 to cumulative amount of methanol fed to the catalysts is proposed and proved the validity to estimate the coke content on SAPO-34 at different reaction conditions. The coke deposited at different reaction temperatures has different compositions.
Keywords: MTO; SAPO-34; Coke; FTIR; DTA;

Preparation of egg-shell nanonickel catalyst for CO hydrogenation by Ji-Rui Song; Li-Xiong Wen; Zeng-Min Xia; Jian-Feng Chen (443-449).
Egg-shell like Ni-based catalyst was prepared on a porous hollow silica (PHS) support to synthesize methanol from CO hydrogenation. It was found from Transmission Electron Microscope (TEM) that Ni particles with a size of 9–11 nm were loaded on PHS to obtain the egg-shell catalysts. X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) analyses indicated that the active site of the catalysts was metallic Ni, which would not be oxidized during the reaction. When the as-prepared Ni/SiO2 egg-shell catalyst was used for CO hydrogenation at 220 °C and 2.0 MPa, the conversion of CO and selectivity to methanol were about 69.5 mol% and 92 mol%, respectively, showing higher activity and selectivity than conventional catalysts. The thermodynamic analysis of CO hydrogenation for methanol synthesis indicated that the conversion of CO is 69.5 mol% under these conditions.
Keywords: Ni catalyst; Porous hollow silica; Egg-shell; Methanol; Synthesis;

Performance of an entrained-flow gasification technology of pulverized coal in pilot-scale plant by Xiaolei Guo; Zhenghua Dai; Xin Gong; Xueli Chen; Haifeng Liu; Fuchen Wang; Zunhong Yu (451-459).
Performance of an entrained-flow gasification technology of pulverized coal in pilot-scale plant is introduced. The gasifier was operated for a throughput of 30–45 t coal per day at pressures of 1–3 MPa. Dense-phase pneumatic conveying was employed for coal's feeding to the gasifier using nitrogen and carbon dioxide as carrier gas, respectively. Effects of the operating conditions including oxygen/carbon ratio and steam/carbon ratio on gasification results were investigated, and the concentration of (CO + H2) in gaseous products reached up to about 97% (vol., dry basis) when CO2 was employed as carrier gas. Moreover, performances of some important instruments in the conveying system of pulverized coal, such as the level indicator and the solid mass flow meter, were also investigated. The typical operating results in this plant such as (CO + H2) concentration, oxygen consumption, coal consumption, carbon conversion and cold gas efficiency were almost as good as those of some well-known dry-fed entrained-flow coal gasification plants.
Keywords: Entrained-flow gasification; Pulverized coal; Pilot-scale plant;

Accelerated deactivation of 15 wt.% Co/Al2O3 catalyst in Fischer–Tropsch synthesis (FTS) in a single-bed and a dual-bed reactor is reported. Water was found to have a remarkable effect on the deactivation of Co/Al2O3 catalyst during FTS. Synthesis at higher temperatures and lower space velocities resulted in higher values of P H2O/(P CO  +  P H2 ) and P H2O/P CO and higher catalyst deactivation rates. Water-induced back-oxidation of cobalt, cobalt–alumina interactions, irreducible cobalt aluminates formation and refractory coke formation are the main sources of deactivation. When the water to carbon monoxide plus hydrogen ratio P H2O/(P CO  +  P H2 ) is greater than about 0.55 or water to carbon monoxide ratio P H2O/P CO is greater than about 1.5, it is not uncommon to find rapid catalyst deactivation. Separation of water and heavy hydrocarbons between the two catalytic beds of the dual-bed reactor, resulted in 62% lower catalyst deactivation rate than that of the single-bed reactor. The amount of refractory coke formation on the catalysts of the dual-bed reactor is 34% lower than that of the single-bed reactor. It was revealed that activity recovery of the used catalysts of the dual-bed is higher than that of the single-bed reactor.
Keywords: Fischer–Tropsch; Cobalt catalyst; Dual-bed; Activity; Lifetime;

Sulphur dioxide (SO2) electrotransfer in electric field generated by corona discharge by Zu-wu Wang; Jia Guo; Han-cai Zeng; Chun-liang Ge; Jiang Yu (471-475).
The mechanism of the forming SO2 negative ions and their electrotransfer in the corona discharge electric field was investigated in this paper. The experimental results showed that SO2 electrotransfer occurred in the electric field with corona discharge, which had potential applications in removal of SO2 of the flue gas from coal-fired power plants by electrotransfer. SO2 electrotransfer was enhanced by higher electric-field intensity or a larger discharging area. Assistant uniform electric field after the corona discharge electric field would improve SO2 electrotransfer. The increment of the desulphurization efficiency by SO2 electrotransfer might reach as high as 50%.
Keywords: Flue gas desulphurization; SO2 negative ions; Corona discharge; Electrotransfer;

Transesterification of the crude oil of rapeseed with NaOH in supercritical and subcritical methanol by Lianyuan Wang; Huayang He; Zifeng Xie; Jichu Yang; Shenlin Zhu (477-481).
Transesterification reaction of the crude oil of rapeseed with supercritical/subcritical methanol in the presence of a relatively low amount of NaOH was successfully carried out, where soap formation didn't occur. The main factors affecting the methyl ester yield during the transesterification reaction were the catalyst content, the reaction temperature, the molar ratio of alcohol to oil and the water content. High methyl ester yield and fast reaction rate could be obtained even if the reaction pressure was relatively low. In addition, kinetics of the transesterification reaction was also discussed.
Keywords: Crude oil of rapeseed; Transesterification; Methyl ester; NaOH; Supercritical methanol; Subcritical methanol;

Modeling mercury speciation is an important requirement for estimating harmful emissions from coal-fired power plants and developing strategies to reduce them. First-principle models based on chemical, kinetic, and thermodynamic aspects exist, but these are complex and difficult to develop. The use of modern data-based machine learning techniques has been recently introduced, including neural networks. Here we propose an alternative approach using abductive networks based on the group method of data handling (GMDH) algorithm, with the advantages of simplified and more automated model synthesis, automatic selection of significant inputs, and more transparent input–output model relationships. Models were developed for predicting three types of mercury speciation (elemental, oxidized, and particulate) using a small dataset containing six inputs parameters on the composition of the coal used and boiler operating conditions. Prediction performance compares favourably with neural network models developed using the same dataset, with correlation coefficients as high as 0.97 for training data. Network committees (ensembles) are proposed as a means of improving prediction accuracy, and suggestions are made for future work to further improve performance.
Keywords: Mercury speciation; Flue gases; Boiler emissions; Predictive modeling; Inferential emission monitoring; Soft sensors; Abductive networks; GMDH algorithm; Neural networks; Network committees; Network ensembles;

Gas-to-liquid technologies: India's perspective by Tirupati Reddy Keshav; S. Basu (493-500).
Gas-to-liquid (GTL) technologies are capable of converting gas to clean, useful liquid hydrocarbons and thus suitable for addressing problems of remote gas utilization, increase in crude oil price, depletion of fossil fuel and environmental pollution. The Indian state of Tripura is considered to be the richest province with 26 billion cubic meters of gas reserves. Neighboring country Myanmar has huge gas reserves but these reserves remain unutilized mainly because of land-locked situation. GTL is a well developed and proven technology and it is an important option for moving natural gas to the market place. GTL options include not only the well-known production of Fischer–Tropsch synthesis liquids but also the production of oxygen containing fuels, fuel additives and chemicals, such as methanol and DME. An alternative, promising option to convert surplus gas is the direct route of methane conversion, which is more energy efficient than the indirect route since it bypasses the energy intensive endothermic steam reforming step of syngas formation. On-site conversion to liquid products of commercial importance using direct route would make transportation of these natural deposits much more economical and practical. In this paper an attempt has been made to review recent developments in syngas technologies, direct routes of methane conversion into useful liquids, and status of both existing and future developments in GTL industry around the world. Finally challenges in GTL technology are discussed.
Keywords: GTL; Syngas technology; Direct conversion of methane; Oxygenates;

Experimental study on the separation of CO2 from flue gas using hollow fiber membrane contactors without wetting by Shui-ping Yan; Meng-Xiang Fang; Wei-Feng Zhang; Shu-Yuan Wang; Zhi-Kang Xu; Zhong-Yang Luo; Ke-Fa Cen (501-511).
Experiments on CO2 removal from flue gas using polypropylene (PP) hollow fiber membrane contactors were conducted in this study. Absorbents including aqueous potassium glycinate (PG) solution, aqueous solutions of monoethanolamine (MEA) and methyldiethanolamine (MDEA) were used to absorb CO2 in the experiments. Based on the wetting experimental results, aqueous PG solution can offer a higher surface tension than water, aqueous MEA and MDEA solutions. Aqueous PG solution has a lower potential of membrane wetting after a continuously steady operation for 40 h to maintain CO2 removal efficiency of about 90%. Under moderate operating conditions, effects of the temperature, flow rate, and concentration of absorbents, and the flow rate of flue gas as well as the volumetric concentration of carbon dioxide in the flue gas on the mass transfer rate of CO2 were studied on a pilot-scale test facility. Unlike conventional absorbents, the mass transfer decreases with an increasing liquid temperature when using aqueous PG solution. Results show that CO2 removal efficiency was above 90% and the mass transfer rate was above 2.0 mol/(m2 h) using the PG aqueous solution. It indicates that the hollow fiber membrane contactor has a great potential in the area of CO2 separation from flue gas when absorbent's concentration and liquid–gas pressure difference are designed elaborately.
Keywords: Gas absorption; Carbon dioxide; Hollow fiber membrane contactor; Wetting; Membrane separation;

Ethanolysis of used frying oil. Biodiesel preparation and characterization by J.M. Encinar; J.F. González; A. Rodríguez-Reinares (513-522).
The transesterification reaction of used frying oil by means of ethanol, using sodium hydroxide, potassium hydroxide, sodium methoxide, and potassium methoxide as catalysts, was studied. The objective of the work was to characterize the ethyl esters for its use as biodiesels in compression ignition motors. The operation variables used were ethanol/oil molar ratio (6:1–12:1), catalyst concentration (0.1–1.5 wt.%), temperature (35–78 °C), and catalyst type. The evolution of the process was followed by gas chromatography, determining the concentration of the ethyl esters at different reaction times. The biodiesel was characterized by its density, viscosity, flash point, combustion point, cold filter plugging point, cloud and pour points, Conradson carbon residue, characteristics of distillation, cetane index and high heating value according to ISO norms. The biodiesel with the best properties was obtained using an ethanol/oil molar ratio of 12:1, potassium hydroxide as catalyst (1%), and 78 °C temperature. The density, viscosity, cetane index, Conradson carbon residue and calorific power of the biodiesel obtained had values close to those of a no. 2 diesel. On the contrary, the cold filter plugging point, and cloud and pour points are higher than the conventional diesel fuel. Although higher, flash and combustion points fulfil the norms for ethyl esters derived from vegetable oils. In consequence, the final product obtained had very similar characteristics to a no. 2 diesel oil, and therefore, these ethyl esters might be used as an alternative to fossil fuels. The two-stage transesterification was better than the one-stage process, and the yields of ethyl esters were improved 30% in relation with the one-stage transesterification.
Keywords: Biodiesel; Transesterification; Used frying oil; Ethanolysis;

In this study, fast pyrolysis of safflower seed (Carthamus tinctorius L.) was investigated with the aim to study the product distribution and their chemical compositions and to identify optimum process conditions for maximizing the bio-oil yield. Experiments were performed in a well-swept resistively heated fixed-bed reactor under nitrogen atmosphere. The maximum oil yield of 54% was obtained at the final pyrolysis temperature of 600°C, sweeping gas flow rate of 100 cm3 min− 1 and heating rate of 300 °C min− 1 in a fixed-bed reactor. The elemental analysis and calorific value of the bio-oil were determined and compared with diesel fuel and then the chemical composition of the bio-oil was investigated using chromatographic and spectroscopic techniques (IR, GC/MS, simulated distillation). The char was characterized by elemental, BET surface area and SEM analyses.
Keywords: Safflower seed; Fast pyrolysis; Characterization;

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