GASIFICATION TODAY
The last ten years have seen the start of a renaissance of gasification technology, as can be seen from Figure 1-1. Electricity generation has emerged as a large new market …
Ash Properties Melting Properties
For all gasifiers the ash-softening and ash-melting or fusion temperatures are important variables. For fluid-bed gasifiers these properties govern the upper operating temperature at which agglomeration of the ash is …
DEDUCTIONS FROM THE THERMODYNAMIC MODEL
1.1.1 Effect of Pressure There is considerable advantage to gasifying under pressure, sufficiently so that practically all modern processes are operated at pressures of at least 10 bar and up …
REACTOR THEORY
Classical chemical engineering theory teaches us about a variety of idealized reactor types. The oldest type of chemical reactor is the batch reactor, of which the coke oven is currently …
The Thermodynamics. of Gasification
In Chapter 1 we defined gasification as the production of gases with a useable heating value from carbonaceous fuels. The range of potential fuels, from coal and oil to biomass …
Chemical Composition of Ash
In Table 4-6 some of the major components of various ashes are given. Apart from these there are many trace components present that do not contribute much to the melting …
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 …
APPLICATIONS TO REACTOR DESIGN
If we include coke ovens as a typical batch reactor in our definition of gasification, then practically all of these idealized reactor forms have been applied at some time or …
REACTIONS
During the process of gasification of solid carbon whether in the form of coal, coke, or char, the principle chemical reactions are those involving carbon, carbon monoxide, carbon dioxide, hydrogen, …
Petroleum Coke
Petroleum coke, more often named petcoke, is increasingly considered as an attractive feedstock for gasification, in particular as it becomes more and more difficult to fire this high-sulfur material as …
Surprises in Calculations
When calculations are carried out for a gasifier assuming heterogeneous reactions, it may come as a surprise that sometimes the quantity of moderator required is negative. The reason may be …
Feedstocks and Feedstock. Characteristics
4.1 COALS AND COKE Approximately 2250MMtoe/y of coal is consumed each year (BP 2002). Of this about 35 MMt/y is gasified to produce 150 million Nm3/d of synthesis gas (Simbeck …
Thermodynamic Equilibrium
As indicated by the double arrows, equations 2-4 to 2-8 are all reversible reactions, that is to say, they may proceed both from right to left as well as from …
LIQUID AND GASEOUS FEEDSTOCKS
In 2002 some 154 million Nm3/d of synthesis gas was produced by partial oxidation of liquid or gaseous feeds (Simbeck and Johnson 2001; SFA Pacific 2001). If fed to state-of-the-art …
OPTIMIZING PROCESS CONDITIONS
Dry coal feed entrained-flow slagging gasifiers operate at temperatures of typically 1500°C. At this temperature the oxygen consumption is high, but nevertheless there is still some moderator required. The challenge …
Formation of Coal
All coal has been formed from biomass. Over time this biomass has been turned into peat. When covered under a layer of overburden, the influence of time, pressure, and temperature …
Other Compounds
Most fuels contain additional material beyond the carbon, hydrogen, and oxygen discussed above. Sulfur in the fuel is converted into H2S and COS, and the nitrogen into elemental nitrogen, NH3, …
Refinery Residues
Over 95% of liquid material gasified consists of refinery residues. Being a high temperature, noncatalytic process, partial oxidation is by and large flexible with Table 4-8 Liquid and Gaseous Gasification …
Process Indicators
When calculating the coal footprint it is very useful to draw also the iso-C02 and iso-CH4 lines (Figure 2-6). The fact that the iso-C02 lines run more or less perpendicular …
Coal Analysis
The methods generally used for specifying the analysis of coals has developed along pragmatic lines and are aimed at providing a useful guide to coal users rather than a purely …
THERMODYNAMIC MODELING OF GASIFICATION
Both designers and operators need to have some knowledge about thermodynamic modeling, although in developing models for gasification, it should be noted that the requirements of a designer and an …
Optimum Operating Point
Efficiencies There are a number of different criteria that are frequently quoted for gasification processes (Reimert 1989). The two most commonly encountered are cold gas efficiency (CGE) and carbon conversion. …
Proximate Analysis
The proximate analysis determines the moisture, volatile matter, fixed carbon, and ash in the coal (see Figure 4-1). The analysis is an essentially practical tool providing an initial indication of …
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 …
