Methane process parameters

GP 8] [R 7] Ignition occurs at a rhodium catalyst at catalyst temperatures between 550 and 700 °C, depending on the process parameters [3]. Total oxidation to water and carbon dioxide is favored at low conversion (< 10%) prior to ignition. Once ignited, the methane conversion increases and hence the catalyst temperature increases abruptly. 

The study of the effects of process parameters reveals that (1) methane can be substantially reduced by higher pressure, shorter contact time, lower temperature, and lower H2/C0 ratio and (2) the aromatics production is greatly favored by lower H2/CO ratio at moderate temperature. 

Energy from Organic Waste Influence of the Process Parameters on the Production of Methane and Hydrogen... 

The principal methods of gas activation are thermal and electrical much less common are chemical and photochemical activation. In the most commonly used thermal activation technique - the hot filament technique - a W or Ta wire is arranged in the immediate vicinity of the substrate to be coated by diamond (Fig. 1). The wire is heated until it reaches the temperature when H2 molecules dissociate readily. The gas phase is a mixture of a carbon-containing gas (e.g. methane, acetone or methanol vapor), at a concentration of a few per cent, and hydrogen. Upon the contact of the gas with the activator surface, excited carbon-containing molecules and radicals are produced, in addition to the hydrogen atoms. They are transferred to the substrate surface, where deposition occurs. Table 2 gives an indication of the hot-filament deposition process parameters. 

Methane-coupling reaction conversions and yields less than 25 percent initially were—and still are—below those acceptable for commercial fuel and chemical feedstock production. But worldwide research and development in more recent years continue to suggest that variations in process parameters, reactor design, and catalyst composition and structure may bridge this gap. Lower reaction temperatures—in the 300-400°C range may... 

The predicted effect of load emissivity, combustion space size, and refractory emissivity for a particular furnace and load is shown in Fig. 18.46 [197], A furnace 5 m long by 1 m high by 1 m wide was loaded with a 0.15-m-thick sheet of iron, while the refractory walls were constructed of 0.5-m-thick red clay brick. The methane burners fired at a rate of 500 kW during operation. Additional process parameters and thermophysical properties are listed in [197]. 

Thus the evaluation of the basic process parameters reduces to the determination of the amount of the element contained in the initial and resultant components of the raw material and the end product. Such values can be established in different ways, some of which were discussed by Pankov and Khripin [175], To obtain a value proportional to the amount of carbon in the key component, the zones of compounds separated in a chromatographic column are converted into carbon dioxide or methane. 

The yield of the reforming process is a mixture of H2, CO, CO2, plus residual steam and still unreformed methane, the so-called reformer gas. The equilibrium composition of the gases depends on the process parameters temperature and pressure which are chosen according to the desired subsequent synthesis gas applications. The example shown in Fig. 5-2 is for a 4 MPa system pressure and a water to methane ratio of 2. The mixture of H2 and CO left after purification is what is called synthesis gas which is an important feedstock in the chemical industry. 

Main process parameters used for the techno-economical comparison are summarized in Table 8.1, where the novel process is compared with a conventional Claus unit -I- tail gas treatment (TGT) and steam methane reforming (SMR) for hydrogen production. 

In order to simulate the process parameters of thermal cracking in the refinery better experiments were carried out in a hydrocarbon atmosphere (methane) at 10 bar pressure. This corresponds to the maximum pressure of the gas supply. 

Water is a common impurity in natural gas that must be removed to prevent hydrate formation. This is a good opportunity for the apphcation of membrane technology, but to be competitive, the membrane system must minimize the loss of methane with the permeate water [5], This loss can be reduced, on the one hand, by choosing membranes with desired selectivity, but, on the other hand, by the process parameters, because this separation is pressure ratio-limited [5]. 

Figure 21.16 Selectivity for CO2 and H2S separation from methane as a function of process parameters. (Source Park et al. [81b]- Reproduced with permission of Elsevier.)...

In the ammonia synthesis process like most other processes the main processing unit and one that attracts most attention from a control point of view is the rector. In ammonia production plant there exists two reactors, the mathanation and the synthesis. The methanation reactor is of much less importance as little amount of reaction takes place in it, while the synthesis reactor is of outmost importance. In this paper initially a four-bed ammonia synthesis catalytic reactor is simulated in a dynamic environment. The simulation is then used to analyze the effect of sudden change on feed pressure and variation of feed distribution on different beds on process parameters such as temperature, pressure, flow rate and concentration through the process. 

Table 5.8 Three examples of process parameters proposed for temperature-staged methanation as proposed by Xu et ai. [399] selectivity is defined as the ratio of moles carbon monoxide converted into moles of methane formed.

The activation of C-H bond in methane is a crucial hrst step in its combustion for power and heat generation. Once the hrst bond has been broken, sequential oxidation reactions to CO2 and H2O are relatively easy. A basic understanding of the activation of C-H bonds in methane is of vital importance since it permits one to assess the inhuence of catalytic and process parameters on the rate and efficiency of its catalytic combustion [29]. Several types of catalysts — including nonreducible oxides, reducible oxides, and metals — are capable of oxidizing methane with varying efficiencies. It is harder for C-H bonds to be activated in methane than in other hydrocarbons, due to the weaker adsorption of methane on oxides or on oxidized metal surfaces [30]. Strong adsorption of a saturated hydrocarbon is a prerequisite for combustion, but factors other than the strength of the C-H bond also affect the rate of combustion. 

Later, a few small plants were built, the process parameters for which were, apparently, quite different. According to [262], the process occurred without catalyst. In this case, natural gas containing 25% ethane yielded a liquid product containing 35% methanol, 20% formaldehyde, 5% acetaldehyde, and some amounts of acetone and dimethyl acetal. According to [263], 1 m of natural gas containing 60% methane (the rest, propane and butane) was... 

One goal of the present study is to develop a process model which can predict particle sizes, size distributions, and production rates for a specified precursor given the process parameter inputs (e.g. pressure, fuel equivalence ratio, flow rates, etc.). Such a model would inevitably involve complex gas phase chemistry which would be capable of predicting the chemical and thermal environment through which the precursor gas passes. Considerable progress has been made with combustion chemical mechanisms, especially for methane and hydrogen fuels. These full mechanisms can readily be applied to one-dimensional flows such as those in our study, and the numerical solution remains computationally tractable. 

A mechanistic model for the kinetics of gas hydrate formation was proposed by Englezos et al. (1987). The model contains one adjustable parameter for each gas hydrate forming substance. The parameters for methane and ethane were determined from experimental data in a semi-batch agitated gas-liquid vessel. During a typical experiment in such a vessel one monitors the rate of methane or ethane gas consumption, the temperature and the pressure. Gas hydrate formation is a crystallization process but the fact that it occurs from a gas-liquid system under pressure makes it difficult to measure and monitor in situ the particle size and particle size distribution as well as the concentration of the methane or ethane in the water phase. 

For the range of industrially relevant conditions, the developed model could accurately predict both the observed CO conversion and the products distribution up to n = 49, in terms of total hydrocarbons, n-paraffins, and a-olefins. In particular, using thirteen adaptive parameters, the model is able to describe the typical deviations of the product distribution from the ASF model, i.e., the methane high selectivity, the low selectivity to C2 species, and the change of the slope of the ASF plot with growing carbon number. Accordingly, the present model can be applied to identify optimized process conditions that are suitable to grant the desired conversion with the requested products distribution. 

The potential of these reactions for methane production can be compared in terms of theoretical yields and heat recovery efficiencies. Theoretical methane yield is defined by the chemical equations. Theoretical heat recovery efficiency is defined as the percent of the higher heating value of the coal which is recovered in the form of methane product. These idealized parameters provide a measure of the ultimate capability of conversion systems and are useful for evaluating actual conversion processes. 

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