| Resumo : |
The exponential increase in the world population brings as an inherent effect the increase in food demand. This demand has made several countries with agricultural production capacity to constitute themselves as great world exporters of grains. The conditioning and storage process of these large volumes of grains requires a large amount of energy. One of these processes is grain drying, an essential process to keep grains within safe moisture levels for storage, transport and export. In order to know the behavior of energy and costs associated with the drying process of soybeans, an exergetic analysis of an industrial column-type drying system is performed. The analysis is carried out for the dryer operat- ing in Paraguay, Brazil, United States and China with different degrees of hybridization, considering its operation from completely fossil to completely electric and, thus, deter- mining possible advantages and disadvantages of the use of electricity from the point of view of exergetic, environmental and commercial costs, incorporating the composition of the electrical matrices of each country. For this, a computational model was developed ca- pable of simulating the drying process of soybeans and determine the conditions of grains and air at the exit of the drying chamber and, thus, perform the calculations of first and second law for the countries in different degrees of hybridization. The computer program is composed of three sections, where the main section is composed of the energy, exergetic and cost calculations, then, the secondary functions that make up the second section of the program are called, and the last section is composed of thermodynamic tables and other constants needed for the calculations. The results show that the model developed was consistent with experimental data from the literature and that there is a decrease in environmental and exergetic costs with the increase of the degree of hybridization. For completely electrical operation from the point of view of exergoenviromental and mone- tary costs, Paraguay proved to be the country with the greatest gains due to its highly renewable energy matrix and low cost of electricity. Regarding the exergetic costs, the re- sults show a small variation with the variation of the hybridization degree, mainly because there is no great difference between the exergetic costs per unit related to the production of natural gas and electricity. |