Synthetic fuel reactors

Sweefland filter, 319,323-325 Symbols, flowsheet, 21-25 Synthetic fuel reactors, 585, 594, 595... 

Sasol produces synthetic fuels and chemicals from coal-derived synthesis gas. Two significant variations of this technology have been commercialized, and new process variations are continually under development. Sasol One used both the fixed-bed (Arge) process, operated at about 240°C, as weU as a circulating fluidized-bed (Synthol) system operating at 340°C. Each ET reactor type has a characteristic product distribution that includes coproducts isolated for use in the chemical industry. Paraffin wax is one of the principal coproducts of the low temperature Arge process. Alcohols, ketones, and lower paraffins are among the valuable coproducts obtained from the Synthol process. 

Several other processes that are aimed at the manufacture of gasoline from coal have been applied over the years. The main reactor in these processes uses three phase fluidization in which solid coal particles, gases, and liquids are all contacted at very high temperatures and pressures. Fluid bed dryers and fluid cokers are also used in synthetic fuels manufacmre. 

The development of three-phase reactor technologies in the 1970 s saw renewed interest in the synthetic fuel area due to the energy crisis of 1973. Several processes were developed for direct coal liquefaction using both slurry bubble column reactors (Exxon Donor Solvent process and Solvent Refined Coal process) and three-phase fluidized bed reactors (H-Coal process). These processes were again shelved in the early 1980 s due to the low price of petroleum crudes. 

KBW [Koppers Babcock Wilcox] A coal gasification process developed jointly by the Koppers Company and Babcock Wilcox, intended to supply the synthetic fuels industry. The product is a mixture of carbon monoxide and hydrogen. Dry, powdered coal, oxygen, and steam are injected into the reactor. The reaction temperature is sufficiently high that the ash is molten it runs down the reactor walls, is tapped out as a molten slag, and is quenched in water before disposal. In 1984, seven commercial synfuels projects planned to use this process but it is not known whether any was commercialized. 

Figure 17.24. Types of reactors for synthetic fuels [Meyers (Ed.), Handbook of Synfuels Technology, McGraw-Hill, New York, 1984], (a) ICI methanol reactor, showing internal distributors. C, D and E are cold shot nozzles, F = catalyst dropout, L = thermocouple, and O = catalyst input, (b) ICI methanol reactor with internal heat exchange and cold shots, (c) Fixed bed reactor for gasoline from coal synthesis gas dimensions 10 x 42 ft, 2000 2-in. dia tubes packed with promoted iron catalyst, production rate 5 tons/day per reactor, (d) Synthol fluidized bed continuous reactor system for gasoline from coal synthesis gas.

High temperature reactors to possibly extend the nuclear production to the supply of process heat to the industry, especially for the production of hydrogen and synthetic fuels for transportation. 

Measurements from synthetic fuel spray flames and laboratory droplet reactors indicated the extent to which fuel properties and combustion conditions influenced particulate yields. A series of seven fuels were tested in a 21 kW spray combustor for total particulate by gravimetric sampling and soot by Bacharach smoke number. Variations in total particulate were dominated by the tendency of the fuel to form ceno-spheres while smoke number correlated with the C H ratio of the fuel. The laboratory droplet studies were performed in a gas flame supported reaction environment. These results confirmed the correlation between soot yield and C H ratio. In addition, two distinct forms of disruptive droplet combustion were observed. 

The high mechanical stability of nitrides suggest their application to synthesis in commercial-type reactors wherever the product distribution of the nitrided catalysts is acceptable. In general the products from nitrided catalysts appear more suitable for production of chemicals than of synthetic fuel however, the selectivity may possibly be considerably different in pilot-plant or large-scale reactors, although these differences are not expected. 

Fig. 19.11. Generic coal gasification reactors. (Source Electric Power Research Institute and Synthetic Fuels Associates, Inc.)...

Thermal effects also are major factors in the design of reactors for making synthetic fuels. The units of Figure 17.24 for synthesis of methanol and gasoline are typical fixed bed types. 

Figure 17.24. Types of reactors for synthetic fuels [Meyers Ed.), Handbook of Synfuels Technology, McGraw-Hill, New York, (a)...

The reverse of reaction (2.1) is methanation. Used to remove residual CO traces from ammonia synthesis feedstocks, it was also developed as an important source of substitute natural gas (SNG) in the synthetic fuels industry. Since this reaction is exothermic, equilibrium yields are better at low temperatures (300-500 C). Thus, high activity is critical. Nickel must be highly dispersed. Preparational methods are required to produce small nickel crystallites. This high metal area must be maintained in the presence of extreme exothermicity, so that sintering must be avoided. This is partially accomplished through proper catalyst design, but process reactor type must also be considered. Recycle, fluidized, and slurry reactors are appropriate. 

The formation of carbon deposits is an undesirable feature of a number of industrial processes, for example on the fuel pins in nuclear reactors, on the catalysts and structural materials of reactors in petrochemical plant, and on furnace wall linings. A greater understanding of the mechanism of deposition is required in order to develop improved methods of control. Metal-carbon interactions are also important in the catalysis of carbon gasification for the manufacture of synthetic fuels. 

Venezuela is one of the world s largest energy suppliers, in particular, of extraheavy crude oils and bitumens. Continuous steam injection could raise the oil recovery rates. Studies have been conducted in Venezuela to apply a high-temperature gas-cooled reactor to the chemical processes of extracting and upgrading the domestic heavy crude oil resources, of the production of synthetic fuel, and of the gasification of extra heavy oil and the so-called Orimulsion (mixture of bitumens and water) fuel [18]. 

The PIPU is a pilot plant system built in the early 1980s for studying a multitude of synthetic fuel/chemical processes. In the mid 1990s, a direct coal liquefaction reactor within the PIPU plant was reconfigured as a SBCR for FTS studies (see Figure 1.). The reactor was originally designed to operate with coarse catalyst pellets (>500 pm). Consequently, the reactor system did not contain a wax separation system sufficient for smaller catalyst particles that are typically used in FTS. Therefore, a slurry accumulator and a batch wax filtration system were installed. 

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