CONSEQUENCES OF RECENT GAS-TURBINE DEVELOPMENTS FOR INDUSTRIAL CHP APPLICATIONS

Developments in gas turbine (GT) technology have been considerable during the last few years. In this paper, consequences regarding the technical performance for industrial combined heat and power applications are discussed and the most important design parameters are identified. Some GT types, which represent different stages of the developmental trend, are analysed in the simple and the combined cycle. Both the industrial and the aero-derivative GT classes are included. Conclusions are: (i) Generally, the developments have broadened the span of achievable power-to-heat ratios (alpha-values). Values between 0 and 1.5 are obtainable for different GT-based schemes with acceptable total efficiencies. (ii) The total efficiencies achievable depend strongly, and differently for different GT types, on the nature of the heat demands in the industrial process. (iii) When opportunities do not exist to cool the exhaust gases in an economizer, i.e. when the stack temperature is directly given by process heat demands, the total efficiency is independent of the GT class. For both classes, however, the development has led to higher total efficiencies when the process temperature demands are high. (iv) When opportunities exist to cool the exhaust gases in an economizer (which is often the case for the simple cycle and always for the combined cycle), the industrial GT developments have given improved ability to reach a high total efficiency. The new aero-derivative types, on the contrary, are worse than the conventional ones in this respect. This can also lead to worse performance in combined cycles for the new aero-derivative types. (v) When supplementary firing is applied, however, the total efficiency is high and similar for all various units and conditions. The 'new acro-derivative' units have, in that case, superior alpha-values-especially in the combined cycle.