The implementation of four configurations of a cogeneration system in a hot-dip galvanizing steel wire process has been studied. The configurations can have the following characteristics: (a) the inlet air to the cogeneration unit can be preheated with its own flue gas (Configuration 1) or with the flue gas from the hot-dip galvanised process (Configuration 3 and Configuration 4), (b) the inlet air to the burners of the hot-dip galvanised process can be non-preheated (Configuration 2), preheated only with the flue gas from the cogeneration units (Configuration 3), or preheated with the flue gas from the cogeneration units and the hot-dip galvanised process (Configuration 1 and Configuration 4). The analysis was carried out under six assessment indicators: natural gas consumption, power generation, fuel cost, CO 2 emissions, flue gas temperature and flue gas quantity. This study required an experimental setup, a modelling of the flue gases using the Aspen HYSYS model, and a modelling of the galvanising barrel using the computational fluid dynamics ( C F D ) model, as well as the validation of the model. The analyses were carried out in the 24-wire hot-dip galvanizing line (Base plant) belongs to the company Moreda Riviere Trefilerías S.A., located in Spain. The main conclusions of this study are: (i) From an operational point of view, Configuration 1, Configuration 3 and Configuration 4 are suitable for implementation, as they comply with the operating conditions of the hot-dip galvanizing process, whereas Configuration 2 does not comply with the operating temperatures; (ii) All configurations have a higher natural gas consumption than the Base plant. These percentages are 4.06% (Configuration 1), 170.07% (Configuration 2), 19.07% (Configuration 3) and 4.43% (Configuration 4). These results exclude Configuration 2 and Configuration 3 due to their low economic viability; (iii) The balance of energy consumed and generated shows that the consumption of natural gas equivalent is lower in Configuration 1 (12.81%) and Configuration 4 (12.44%) compared to the Base plant, and higher in Configuration 2 (147.58%) and Configuration 3 (2.20%). These results exclude Configurations 2 and Configuration 3 due to their low economic viability; (iv) The fuel cost is lower in Configuration 1 (20.81%), Configuration 3 (5.81%) and Configuration 4 (20.46%) compared to the Base plant, and higher in Configuration 2 (136.95). These results exclude Configuration 2 due to its low economic viability; (v) Configuration 1 and Configuration 4 produce CO 2 emission savings compared to the Base plant, 3.13% and 2.76% respectively. In contrast, Configurations 2 and Configuration 3 generate more CO 2 emissions, 160.30% and 11.80% respectively. These results exclude Configuration 2 and Configuration 3 due to their negative environmental impact; (vi) The flue gas temperature at the chimney outlet is lower in Configuration 1 (41.11%), Configuration 3 (13.66%) and Configuration 4 (40.38%) compared to the Base plant. In contrast, Configuration 2 operates at a similar temperature. Configuration 2 has a neutral impact on this assessment indicator; and (vii) The amount of flue gas at the chimney outlet is higher in Configuration 1 (16.85%), Configuration 3 (17.31%) and Configuration 4 (16.86%) compared to the Base plant, and very higher in Configuration 2 (152.66%). Therefore, Configuration 1 and Configuration 4 are the appropriate configurations for implementation in a cogeneration system. • 4 configurations of cogeneration in a hot-dip galvanizing process has been studied. • The fuel cost is lower in C1 (20.81%), C3 (5.81%) and C4 (20.46%) compared to Base plant. • CO2 emission savings are C1 (3.13%) and C4 (2.76%) compared to the Base plant. • The gas temperature is lower in C1 (41.11%) and C4 (40.38%) compared to Base plant. • These results show the advantages of cogeneration technologies in the process.
Álvarez-Álvarez et al. (Sun,) studied this question.