Energy evaluation of the substitution of fuels by replacement fuels in high temperature material treatment processes, Part 2

The evaluation of normal fuels during use in high temperature production processes, for energy conversion in power stations, etc. has to be carried out with the aid of suitable fuel technology criteria, such as the chemical, mechanical, calorific and reaction characteristics - in each case in conjunction with characteristic features of the particular process technology If normal fuels are substituted by replacement fuels then the latter must also be evaluated with the criteria mentioned and a comparative assessment of the particular process must be made during the use of the different fuels (influence of fuel). The so-called energy replacement ratio is important in this situation. In addition to this, other aspects, such as changed cumulative energy and pollutant balances, have to be taken into account during the use of replacement fuels. This article uses the example of the cement industry to examine the calorific properties of replacement fuels in conjunction with the specific conditions of the clinker burning process. The examination is initially confined to important process sections and their representation as ideal stirred-vessel elements to explain the principal aspects of fuel substitution and to illustrate important trends caused by major influencing variables. This simplified, but powerful, survey can be applied in a similar way to other processes in the primary industries, such as the lime, glass and ceramics industries, and to the processes of energy conversion, i.e. to high temperature processes in general. It can be refined and hence carried out in correspondingly greater detail by increasing the number of elements.