584Hydrogasification
During the 1970s and 1980s there was considerable interest in developing a process to produce synthetic natural gas by direct hydrogenation of coal to methane. The principle reaction involved is that of methanation. C 2H2 S CH4 -75 MJ kmol 2-6 The thermodynamics of this reaction demand that it be operated at high pressure. Although the reaction is exothermic, the reactants must first be brought to a high temperature for the reaction to proceed at an economically acceptable rate. Furthermore,...
WetCataiysis
Processing H2S to sulfuric acid differs from conventional acid plants whether using sulfur or metallurgical off gases as feed in that water is already present in the converter. This water reacts immediately with the SO3 formed there and therefore demands a totally different approach to the recovery of liquid acid compared with a standard double absorption unit. The H2S component of the acid gas is first combusted with excess oxygen to form SO2 and water see Figure 8-18 . The excess is selected...
523 The HighTemperature Winkler HTW Process
The name high-temperature Winkler for the process developed by Rheinbraun primarily for lignite gasification is to some extent a misnomer. The most important development vis- -vis the original Winkler process is the increase of pressure, which has now been demonstrated at 30 bar. Rheinbraun, an important lignite producer in Germany, began work on the process in the 1970s. A Rheinbraun subsidiary, Union Kraftstoff, Wesseling, had operated atmospheric Winkler generators between 1956 and 1964, and...
311 Devolatilization
The first step, heating up of the coal particles, is in one sense the simplest part of the process. Nonetheless, the speed at which it takes place has an influence on the subsequent steps, so that it is of great importance in any accurate model. Devolatilization takes place already at low temperatures 350-800 C and in parallel with the heating up of the coal particles. The rate of heating of the coal particles influences the way in which the devolatilization takes place J ntgen and van Heek...
541 The Texaco Gasification Process
The Texaco Gasification Process was developed in the late 1940s. Early research efforts focused on producing syngas from natural gas to produce liquid hydrocarbons via Fischer-Tropsch technology. The first commercial-scale plant based on natural gas as a feedstock was commissioned in 1950 for the production of ammonia. The first commercial-scale use of oil feedstocks occurred in 1956, and early coal work began at about the same time. In the 1970s research efforts were then focused on coal...
6114 Metal Dusting
Metal dusting is a particularly aggressive form of high-temperature mostly CO corrosion, which has received particular attention in connection with the manufacture of CO-rich synthesis gases using steam reforming or catalytic partial oxidation. Although certain details of the mechanism of metal dusting, and particularly the potential for countermeasures, remain the subject of some debate, the essentials have been understood for many years Hochmann 1972 Grabke, Brach-Troconis, and M ller-Lorenz...
Literature Data Bank
The literature databank gaslit.mdb contains over 500 entries on the topic of gasification, including all the literature cited in this book. It includes titles, authors, and keywords for all papers presented at the Gasification Technologies Council Conferences since 1998, all the IChemE Gasification Conferences, and a number of other important sources not normally accessible to nonparticipants. The database includes a keyword-based search facility, with up to six specified keywords per article....
Flow Scheme
The flow scheme of the Tophat cycle is shown in Figure 7-20 van der Burgt and van Liere 1996 . The water is injected in the air A entering the compressor in such a way that the compressor does not suffer from a parasitic pressure drop. It is injected in the form of very fine droplets of a mean diameter of about 1-3 These droplets, that can be made by combining flash evaporation with efficient atomizers as in the swirl flash technology van Paassen and van Liere 1980 , are so small that the...
High Temperature HT Shift
Conventional high temperature shift uses an iron oxide-based catalyst promoted typically with chromium and more recently with copper. The operating range of these catalysts is between 300 and 500 C. Much above 500 C sintering of the catalyst sets in and it is deactivated. HT shift catalyst is tolerant of sulfur up to a practical limit of about 100ppmv, but it is likely to loose mechanical strength, particularly if subjected to changing amounts of sulfur. An important aspect in the design of CO...
331 Modeling
The systems described in this chapter are extremely complex, which has to date placed limitations on the application of kinetic models to commercial gasification reactor design. Nonetheless the availability of increasingly powerful computers with a deeper understanding of the physical and chemical processes of coal combustion Figure 3-8. CFD Model of a Gasification Burner Outlet Zone Source Hofmockel, Liebner, and Ulber 2000 Figure 3-8. CFD Model of a Gasification Burner Outlet Zone Source...
233 Fuel Footprint
For a good understanding of the gasification of any particular feedstock, whether coal, heavy oil, waste biomass, or gas, it is important to calculate the gasification characteristics of the fuel in order to be able to understand what is going on in the reactor and to optimize the reaction conditions. Figure 2-3. Variation of Syngas Compositions with Pressure at 30 bar Figure 2-3. Variation of Syngas Compositions with Pressure at 30 bar Figure 2-4. Variation of Yields with Pressure at 30 bar...
221 Basic Data
A model for gasification is only as good as the basic thermodynamic data used. To ensure consistency of mass and heat balances it is of fundamental importance to limit the data set to a minimum and generate all other data from this. In the calculations used in this book and in the website programs, use has been made of various sources, the most important being Barin 1989 . For the thermodynamic calculations standard enthalpy and entropy data have been used in combination with a curve-fit for...