Methanation operating conditions

The methanation reaction is carried out over a catalyst at operating conditions of 503—723 K, 0.1—10 MPa (1—100 atm), and space velocities of 500—25,000 h . Although many catalysts are suitable for effecting the conversion of synthesis gas to methane, nickel-based catalysts are are used almost exclusively for industrial appHcations. Methanation is extremely exothermic (AT/ qq = —214.6 kJ or —51.3 kcal), and heat must be removed efficiently to minimise loss of catalyst activity from metal sintering or reactor plugging by nickel carbide formation. 

Instead of conversion, some producers prefer to use other identifications of severity, including coil outlet temperature, propylene to methane ratio, propylene to ethylene ratio, or cracking severity index (33). Of course, all these definitions are somewhat dependent on feed properties, and most also depend on the operating conditions. 

Predicting the appropriate level of duetile fraeture resistance involves an analysis of fluid properties, operating conditions, and material properties. For natural gas pipelines containing mostly methane with very... 

Because some hydrocracking occurs, Powerforming also produces saturated C to Q light hydrocarbons. The methane and ethane formed normally are consumed as refinery fuel. Propane and butane products are frequently marketed as LPG. The relative quantities of each of these products vary considerably with feed quality, operating conditions and octane severity. 

A thermal plasma system has been developed for the decomposition of methane. A schematic diagram of the experimental apparatus is shown in Fig. 1. The system consists primarily of D.C. plasma torch, plasma reactor and filter assembly. Plasma was discharged between a tungsten cathode and a copper anode using N2 gas. All the experiments were carried out at atmospheric pressure at 6 kW input electric power and N2 flow rate of 10 to 12 1/min. The feed gas (CH4) flow rates were varied from 3 to 15 1/min depending on the operating conditions, shown in Table. 1. 

Controlled elimination of mass and heat transport resistances is an important prerequisite for obtaining intrinsic kinetic parameters of the fast exothermic reaction of partial oxidation of methane to synthesis gas. It has been demonstrated that under conditions of strong transport limitations erroneous conclusions concerning the reaction scheme can be derived [7-9]. It was determined in this laboratory that transport limitations are practically absent over a wide range of operating conditions if one portion of the catalyst (< 40 pm) is diluted with -5 portions of an... 

Figure 4.2 presents a simplified flow diagram of the ENCOAL Liquid from Coal (LFC) process. The process upgrades low-rank coals to two fuels, Process-Derived Coal (PDF ) and Coal-Derived Liquid (CDL ). Coal is first crushed and screened to about 50 mm by 3 mm and conveyed to a rotary grate dryer, where it is heated and dried by a hot gas stream under controlled conditions. The gas temperature and solids residence time are controlled so that the moisture content of the coal is reduced but pyrolysis reactions are not initiated. Under the drier operating conditions most of the coal moisture content is released however, releases of methane, carbon dioxide, and monoxide are minimal. The dried coal is then transferred to a pyrolysis reactor, where hot recycled gas heats the coal to about 540°C. The solids residence time... 

Reduction of C02 past formic acid generates formaldehyde, methanol or methane (Eqs. (16-18)), and ethanol can be produced by homologation of the methanol. The liberation of water makes these reactions thermodynamically favorable but economically less favorable. The reductions typically require much higher temperatures than does the reduction to formic acid, and consequently few homogeneous catalysts are both kinetically capable and able to withstand the operating conditions. 

Non-noble metal catalysts, particularly those containing nickel, have also been investigated extensively since 1990. Lunsford et al. (107) examined a 25 wt% Ni/Al203 catalyst in the temperature range 723-1173 K. Carbon monoxide selectivities approaching 95% and virtually complete conversion of the methane were achieved at temperatures above 973 K. The authors observed that, under their operating conditions, the calcined catalyst bed consisted of... 

P = 150-250 bar, T = 250-600 °C) is considered as a promising technique to convert such wet streams into a gas that is rich in either hydrogen or methane (see Section 6.7.3 for reaction equations), depending on the operating conditions and applied catalysts [17, 18, 46-48]. Feed stocks are either homogeneous liquids or slurries. 

The model analytes, which were used to show the sensor performance of the microsystems include carbon monoxide, CO, and methane, CH4. The sensor microsystems were designed for practical applications, such as environmental monitoring, industrial safety applications or household surveillance, which implies that oxygen and water vapors are present under normal operating conditions. In the following, a brief overview of the relevant gas sensor mechanisms focused on nano crystalline tin-oxide thick-film layers will be given. 

In the first part of the chapter, a state-of-the-art review and also a thermodynamic analysis of the autothermal reforming reaction are reported. The former, relevant to both chemical and engineering aspects, refers to the reaction system and the relevant catalysts investigated. The latter discusses the effect of the operating conditions on methane conversion and hydrogen yield. 

After the ignition phase, water is fed to the reactor and the 02 CH4 and H20 CH4 ratios are varied until the desired operating conditions are reached. It must be noted that after the ignition phase, due to the lower values of the 02 CH4 ratio, the homogeneous combustion of methane is inhibited and consequently POX, SR and WGS reactions occur simultaneously in the catalytic bed, while the temperature on the SiC foam decreases to values lower than 400 °C. 

Noble metal catalysts High yields of synthesis gas were reported for the partial oxidation of methane over nearly all noble metal catalysts (Pd, Rh, Ru, Pt, Ir) [110]. The observed performances (degree of methane conversion and yields of CO and H2) vary with the catalyst and the operating conditions but all reported data share these common features (i) no carbon deposition is observed (Claridge and co-workers [135]... 

Catalytic Activity. The world-wide interest focused in the catalytic partial oxidation of methane to formaldehyde has led to a great variety of conflicting results (9), The main reason of such discrepancies lies in the lack of a generally valid rule for evaluating and comparing the proposed catalytic systems. In effect, this reaction involves a very complex pathway since the desired partial oxidation product, HCHO, exhibits a limited thermal stability at T>4(X)°C and can be oxidized to more easily than CH itself. Hence, a suitable reactor device and appropriate operating conditions result to be of fundamental importance in order to attain reliable data unaffected by experimental artefacts. 

Two sets of typical operating conditions are used for the simulations presented. These are shown in Table IV and will be referred to as standard type I or II conditions. Type I corresponds to operation at moderate to high temperatures, pressures, and flow rates with relatively low inlet CO and H2 concentrations and small amounts of inlet CH4, C02, and HzO either from recycle or from the upstream process. Type II is based on conditions for the industrial use of methanation in synthetic natural gas production. Note that the inlet methane concentration is much higher than in type I. 

Although liquid polymers boiling in the gasoline range can be made from methane, ethane, and ethylene, the yield has been too low and the operating conditions too severe to make gasoline from them economically. 

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