Syngas mixtures

Gasification. Gasification converts soHd fuel, tars, and oils to gaseous products such as CO, H2, and CH that can be burned direcdy or used in synthesis gas (syngas) mixtures, ie, CO and mixtures for production of Hquid fuels and other chemicals (47,48) (see Coal conversion processes, gasification Euels, synthetic-gaseous fuel Hydrogen). 

The heating value of the resultant syngas mixture per mole of methane supplied, but now containing (1 — a) moles of CH4, /3 moles of hydrogen and (4a — (3) moles of... 

Calorimetric Enthalpy Data for Binary Syngas Mixtures"... 

Y. Nishiyama, N. Otsuka and T. Kudo, Metal Dusting Behavior of Cr-Ni Steel and Ni-base Alloys in a Simulated Syngas Mixture, Corrosion Science, 48 2064-2083 (2006). 

During ATR, air (or O2), fuel, and steam react to form a syngas mixture with a net heat of reaction near zero at temperatures of 600-800°C (A more thorough discussion can be found in Section 5). A number of reactions take place in this step, including POX and SR The primary reactions i.e., those leading to CO and H2) can be represented as follows ... 

Catalyst batches were activated under two different activation conditions H2/CO (with 3% Ar) = 2.6 3.87 xmol/s (FT synthesis reaction mixture with H2/CO = 0.7) for 2 h at (1) 523 K and (2) 543 K. These conditions are based on temperatures and gases used by PETC to activate these catalysts for testing prior to a large scale pilot plant run. After activation, reactions were carried out over the catalyst samples in the same reactor tube at 523 K with H2/CO = 0.7 and a total gas flow rate of 6.47 pmol/s (with Ar as internal standard) at a pressure of 83.8 kPa (normal atmospheric pressure in Albuquerque). Two sets of samples were made, one for each of the two activation conditions. Each set consisted of three samples after activation, activation followed by FT reaction for 10 h, and activation followed by FT reaction for 45 h. In the case of the activation at 523 K, the first 2 h of the run were considered the activation step. Therefore, the activation in this case was at 523 K. For activation at 543 K, the catalyst bed was cooled to 523 K in the syngas mixture of activation. 

Methanol is produced from a nonstoichiometric syngas mixture (CC>2 CO H2 = 5 5 90) at 50-100 bar pressure and a temperature between 225°C and 275°C over a Cu/Zn0/Al203 catalyst. The predominant reaction is... 

In general, the addition of alkaline promoters gives similar results to the use of syngas mixtures rich in CO. and also the waicrgas shift reaction is enhanced. The carbon deposition on potassium-promoted iron has recently been investigated using X-ray phoioemission spectroscopy (XPS) [57]. Measurements on the K 2p levels showed that the potassium compound is not covered by the deposited carbon but rather sits on top of the carbon layer. 

Using the catalyst system known from the Monsanto process, Dumas et at. have been able to direct the reaction towards ethanol formation using syngas mixtures extremely rich in hydrogen [87]. As is shown in Table XII, no acetic acid and only minor amounts of acetates are formed at an H3/CO ratio of 60. Ethanol and acetaldehyde aie the main products along with considerable amounts of methyl ethyl ether. Unfortunately, the Dumas c/ at. based the yields and conversion on carbon monoxide and not on methanol. This makes the data of this interesting process difficult to compare with those of other catalyst systems. 

The water-gas shift (WGS) reaction (Reaction 11) is frequently used to produce additional hydrogen fi om the syngas mixture. This process could be used to adjust the H2/CO ratio for downstream fuel processes or to produce large volumes of hydrogen to be used as an ultra-clean transportation fuel. Simply... 

The exhaust heat from the combustion turbine is recovered in the heat recovery steam generator to produce steam. The waste heat is passed to a steam turbine system, while heat is recovered from both the gasification process and the gas turbine exhaust in advanced boilers producing steam. The steam is then used in steam turbines to produce additional electrical power, while the syngas mixture could also feed a fuel cell plant (IGFC). 

In this section, several of commercial hydrogen production processes based on recovery of hydrogen from syngas mixture or other petrochemical offgas mixture are briefly summarized. Other commercial hydrogen production processes using natural gas as feedstock are covered in Chapter 4. 

Kummer et al. converted a syngas mixture (CO/H2 = 1/1) that contained either methyl-or methylene-labeled radioactive ethanol over an iron catalyst at about 230 °C and 1 atm pressure. Most runs were with a catalyst that contained 2.82 percent AI2O3 and 1.39 percent Th02 promoters. If ethyl alcohol is either an intermediate or if it becomes... 

Fig. 10.13 COMSOL simulated gas composition of a syngas mixture along the length of a WGSMR...

The oldest patents concerning polyhydric alcohols mention Mn, Cr, and Co catalysts which were applied at very high pressures but nevertheless were still of poor activity and selectivity. Substantial progress in selectivity has been achieved with Rh catalysts by, e.g.. Union Carbide. With proper co-catalysts e.g., firmly co-ordinated Cs) up to 75% of ethylene glycol can be made from syngas mixtures. Keim et al. reported that solvents are also important for the resulting activity and selectivity. For example, the order of activity in oxygenates formation of various metal complexes (mostly carbonyls) dissolved in A -methyl pyrrolidone is ... 

Pinaccia et al. [25] investigated the tubular Pd membrane reactor at higher temperatures, i.e., above 400 °C and higher pressures (100-800 kPa). They did permeation tests for 1200 h at 400 °C and the membrane exhibits excellent stability. After permeation they evaluated membrane reactor for WGS reaction using commercial Fe-Cr catalyst in the syngas mixture. They are able to achieve 85% CO conversion and 82% H2 recovery with 97% purity. 

Augustine et al. [28] reported durability of porous stainless steel supported Pd tubular membranes for WGS reaction. The synthesized membrane is very stable in the presence of H2/H2O mixture. No significant change in the H2 permeance is observed for 2000 h. However, under WGS conditions when the H20 C0 ratio was 2 1, a reduction in H2 recovery was observed over 65 h due to coke formation on the membrane surface. They conducted another WGS experiment for 1000 h with a higher H20 CO ratio of 3 1 and stable behaviour was observed. They achieved 97% CO conversion and 85% H2 recovery from a simulated syngas mixture for 900 h. 

A. Brunetti, G. Barbieria, E. DrioU, Upgrading of a syngas mixture for pure hydrogen production in a Pd-Ag membrane reactor, Chem. Eng. Sci. 64 (2009) 3448-3454. 

Zeolites are also used in the non-cryogenic purification of hydrogen by the adsorption of water, CO2, N2 and hydrocarbons and in the removal of residual CO2 and H2O from syngas mixtures prepared by reforming natural gas according to the reaction CH4+H2O CO + 3H2. These processes are important... 

Precombustion capture. This solution is developed in two phases (1) the conversion of the fuel in a mixture of H2 and CO (syngas mixture) through, for example, partial oxidation, steam reforming, or autothermal reforming of hydrocarbons, followed by water-gas shift (WGS), and (2) the separation of CO2 (at 30%-35%) from the H2 that is then fed as clean fuel to turbines. In these cases, the CO2 separation could happen at very high pressures (up to 80 bar of pressure difference) and high temperatures (300°C-700°C).42... 

LTFT iron catalysts are commonly prepared by precipitation techniques, with a typical composition of potassium oxide, copper, silica and iron (1 1 5 20 by mass). Before use in the LTFT process, the catalysts are prereduced with either hydrogen or a syngas mixture.HTFT catalysts can be formed from the fusion of magnetite with various promoters, typically potassium oxide and aluminium oxide or magnesium oxide. Similarly, HTFT catalysts require a pre-reduction with hydrogen at ca. 400 °C. 

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