Fuel allocation in a combined steam-injected gas turbine and thermal seawater desalination system

Fuel allocation in a combined steam-injected gas turbine (STIG) power generation and multi-effect thermal vapor compression (METVC) desalination system is studied, using seven methods: (1) Products Energy Method, (2) Products Exergy Method, (3) Power-Generation-Favored Method, (4) Heat-Production-Favored Method, (5) Basic Exergetic Cost Theory, (6) Functional Approach and (7) Splitting Factor Method. The latter three are thermoeconomics-based. Two sample cases are calculated. The methods and results are compared and discussed. The main conclusions are: it is important to carefully choose suitable methods to perform fuel allocation in a dual purpose desalination systems (here a combined STIG-METVC system) since different methods produce very different results; The results obtained from Methods (1) and (5) are unreasonable, and those from Methods (3) and (4) set the range within which the fuel allocation values must reside; Although thermoeconomic methodologies are considered to be the most rational for cost attribution of multi-product systems, false results could be reached if they are not suitably used; When sufficient information is unavailable for performing a thermoeconomic analysis, Method (2) can be taken as an approximation for fuel allocation, as well as for the distribution of fuel cost and combustion pollutant emission, between power and water in a STIG-METVC system. A recommended fuel allocation analysis procedure, based on this study and with some generality for other gas-turbine power plant dual purpose thermal desalination systems, was outlined.