Coal gasification energy balance

The velocity of the combustion front is determined by the volatile matter content of the raw coal, Wv. If the volatile matter content of the coal is high the frontal velocity will be slowed. With low volatility coals the frontal velocity will be relatively fast for the same excess energy production in the com-bustion/gasification regions of the bed. The velocity vc is set by the requirement that the volatiles content of the coal ahead of the devolatilization zone be essentially that of the raw coal. From an analysis of the energy balance in the region near the front of the devolatilization zone, it can be shown that a particular root of the relation below establishes v (3) ... 

The software system, to meet the needs of the 1980 s, has wide flexibility and capabilities. For processes such as coal gasification or coal liquefaction, it can be used to perform steady state material and energy balances, calculate sizes of equipment, and carry out economic evaluations. Its flexibility can allow for the handling of coal or other solids in streams and equipment, and its capabilities allow for the simulation of many different types of process equipment and the calculations of physical properties under widely different conditions. Included in this is the ability to analyze conventional chemical and petroleum processes. Another valuable feature 1s a good preliminary cost estimation capability that permits the comparison of alternative processes on an economically consistent basis at an early stage of development. 

Natural gas will remain the preferred feedstock of present ammonia production technology in the medium term (15-20 years) as may be assumed from the world energy balance shown in Table 47. Partial oxidation of heavy hydrocarbon residues will be limited to special cases and coal gasification might not play a major role in this period. 

Table 10-13. Energy Balance of Plasma-Chemical Coal Gasification by Water Vapor with Heating the Reagents in Thermal Plasma Jets of Other Gases...

As mentioned already in the previous chapter, time does not play a role in the formulation of equilibrium conditions. The mass and energy balances and the maximum conversion rate that can be achieved when the system is in thermal equilibrium are therefore not sufficient to define the dimensions of the best suited coal gasification equipment, which will here be termed the gas generator. A knowledge of how the gasification reactions proceed with time is therefore indispensable. To measure and, wherever possible, calculate this dependence on time is the object of reaction kinetics. Dealing with details of kinetic laws would go beyond the scope and purpose of this book and the reader should turn to the relevant literature [1.4]. 

Coal was added to the secondary fuels to balance out the significant fluctuations in fuel properties, e.g. heating value, and to provide residual char as energy source for the endothermic gasification process (autothermal operation). In 2007 the Swiss Sustec Industries AG, then owner of SVZ, put the gasification plant out of service and discontinued the waste conversion operation because of insufficient profitability. 

---