Partial oxidation plants

Partial methane oxidation comprises very high rates so that high space-time yields can be achieved (see original citations in [3]). Residence times are in the range of a few milliseconds. Based on this and other information, it is believed that syngas facilities can be far smaller and less costly in investment than reforming plants. Industrial partial oxidation plants are on the market, as e.g. provided by the Syntroleum Corporation (Tulsa, OK, USA). Requirements for such processes are operation at elevated pressure, to meet the downstream process requirements, and autothermal operation. 

Partial oxidation (POX), 13 844 catalytic aerogels for, l 763t economic process of, 13 781-783 of hydrocarbons, 13 780-783 Partial oxidation facility, 13 792—793 Partial oxidation plants, 13 775-776 Partial oxidation units, 13 782... 

The Rectisol process [667], [707], [711]-[715] seems to be the prime choice in partial oxidation plants. The process, invented by Lurgi and developed further by Linde, operates with chilled methanol, a cheap and readily available solvent, in which carbon dioxide, hydrogen sulfide and carbonyl sulfide (COS) are readily soluble at low operating temperatures of below - 30 °C. The Henry absorption coefficient for H2S is about six times higher than for C02-... 

Other compression duties in the plants, such as process air in steam reforming plants and air, and oxygen, and nitrogen compression in partial oxidation plants, are... 

Integrating ammonia and urea production [1218] has been discussed frequently in the past, in most cases with respect to energy and C02 supply. For total conversion of the ammonia, the CO, produced in partial oxidation plants suffices but is at deficit in plants based on steam reforming of natural gas. 

Corrosion by hydrogen sulfide in partial oxidation plants can be controlled by the use of austenitic steels, but special care to ensure proper stress relief of welds is advisable to avoid stress corrosion cracking in these plants caused by traces of chlorine sometimes present in the feed oil. 

The availability of inexpensive oil and gas in the late 1950s caused Texaco to direct its development efforts toward partial oxidation of oil and gas. Over 100 commercial Texaco partial-oxidation plants have been licensed worldwide to convert a variety of hydrocarbon feedstocks to carbon monoxide and hydrogen (1). 

The adverse effect caused by a high concentration of water has also been demonstrated on an industrial scale. In a partial oxidation plant with a liquid nitrogen wash, about 100 ppm of oxygen leaked into the synthesis loop, giving an [0] content in the inlet gas of about 20-30 ppm. This resulted in an immediate activity decline. The pressure was increased as well as the temperature. However, the production declined somewhat. After some months of operation, the oxygen contaminant was removed and the catalyst regained its former activity. 

Acetaldehyde, first used extensively during World War I as a starting material for making acetone [67-64-1] from acetic acid [64-19-7] is currendy an important intermediate in the production of acetic acid, acetic anhydride [108-24-7] ethyl acetate [141-78-6] peracetic acid [79-21 -0] pentaerythritol [115-77-5] chloral [302-17-0], glyoxal [107-22-2], aLkylamines, and pyridines. Commercial processes for acetaldehyde production include the oxidation or dehydrogenation of ethanol, the addition of water to acetylene, the partial oxidation of hydrocarbons, and the direct oxidation of ethylene [74-85-1]. In 1989, it was estimated that 28 companies having more than 98% of the wodd s 2.5 megaton per year plant capacity used the Wacker-Hoechst processes for the direct oxidation of ethylene. 

The electrons undergo the equivalent of a partial oxidation process ia a dark reaction to a positive potential of +0.4 V, and Photosystem I then raises the potential of the electrons to as high as —0.7 V. Under normal photosynthesis conditions, these electrons reduce tryphosphopyridine-nucleotide (TPN) to TPNH, which reduces carbon dioxide to organic plant material. In the biophotolysis of water, these electrons are diverted from carbon dioxide to a microbial hydrogenase for reduction of protons to hydrogen ... 

Medium Heat- Value Gas. Medium heat-value (medium Btu) gas (6,7) has a heating value between 9 and 26 MJ/m (250 and 700 Btu/fT). At the lower end of this range, the gas is produced like low heat-value gas, with the notable exception that an air separation plant is added and relatively pure oxygen (qv) is used instead of air to partially oxidize the coal. This eliminates the potential for nitrogen in the product and increases the heating value of the product to 10.6 MJ /m (285 Btu/fT). Medium heat-value gas consists of a mixture of methane, carbon monoxide, hydrogen, and various other gases and is suitable as a fuel for industrial consumers. 

Equipment. Partial-oxidation gasification section equipment in many plants consists essentially of (/) the gasification reactor (2) the waste-heat exchanger for heat recovery from the hot reactor gas or direct quench system (J) the economizer heat exchanger for further heat recovery (4) the carbon removal system for separating carbon from the reactor product gas and (5) the carbon recovery system for recycle of carbon. 

Of the raw material hydrogen sources—natural gas, coal, and petroleum fractions—natural gas is the most often employed in ammonia plants in the 1990s and steam reforming is by far the most often used process. Partial oxidation processes are utilized where steam-reformable feeds are not available or in special situations where local conditions exist to provide favorable economics. Table 5 fists the contribution of the various feedstocks to world ammonia... 

Capital costs which foUow the same trend as energy consumption, can be about 1.5 to 2.0 times for partial oxidation and coal gasification, respectively, that for natural gas reforming (41). A naphtha reforming plant would cost about 15—20% more than one based on natural gas because of the requirement for hydrotreatiag faciUties and a larger front-end needed for carbon dioxide removal. 

Conventional Transportation Fuels. Synthesis gas produced from coal gasification or from natural gas by partial oxidation or steam reforming can be converted into a variety of transportation fuels, such as gasoline, aviation turbine fuel (see Aviation and other gas turbine fuels), and diesel fuel. A widely known process used for this appHcation is the Eischer-Tropsch process which converts synthesis gas into largely aHphatic hydrocarbons over an iron or cobalt catalyst. The process was operated successfully in Germany during World War II and is being used commercially at the Sasol plants in South Africa. 

In conventional cycles, combustion is the major source of irreversibility, leading to reduction in thermal efficiency. Some novel plants involve partial oxidation (PO) of the fuel in two or more stages, with the temperature increased before each stage of combustion, and the combustion irreversibility consequently reduced. In other plants full oxidation is employed which makes CO2 removal easier. 

Newby and his colleagues provided some calculations of the performance of this partial oxidation cycle. They show that a major parameter in the performance of the PO cycle is the PO turbine inlet pressure, and listed calculations for three values of this pressure 45 bar, 60 and 100 bar. Their results for the composition of the gas streams round the plant (from the 60 bar calculation, which gave 49.3% for 335 MW) are given in Table 8.2. 

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