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Abstract(s)
O presente trabalho teve como objetivo realizar um estudo das perdas de energia térmica em válvulas e acessórios não isolados numa linha de vapor de uma indústria de processo químico (RAR-Refinaria de Açúcar Reunidas S.A.).
A energia perdida numa linha de vapor é muito significativa e, por tal, houve a necessidade de estudar o isolamento de tubagens e acessórios (como válvulas) de forma a minimizar as perdas e reduzir o consumo de combustível. Para determinar essas perdas, estudaram-se dois métodos diferentes, cujos resultados foram comparados com valores obtidos pela norma standard BS 5422: 1990.
As perdas de calor para tubagens sem isolamento ou com várias espessuras de isolamento foram determinadas em alguns ensaios prévios. Os resultados obtidos usando o software 3EPlus ou determinados por correlações empíricas apresentam, em média, uma diferença de 6,6% e 2,6%, respetivamente, quando comparados com os valores da norma. Admitindo o critério de um limite máximo de 7% para esta diferença, pode-se concluir que o uso do software 3EPlus permite obter uma aproximação válida para o cálculo das perdas de calor.
Os valores, em média, das perdas de calor determinados em válvulas e acessórios não isolados foram de 153 kW/ano, o que corresponde a um consumo de 78.459 kg/ano de fuel considerando uma eficiência da caldeira de 88%.
Após a verificação que o investimento no isolamento seria economicamente interessante, procedeu-se à sua aplicação. Este possibilitou um ganho energético de 133 kW/ano, que corresponde a 68.400 kg/ano de fuel, representando um proveito financeiro anual aproximado de 20.000€ após o primeiro ano de investimento.
The main goal of this work was the evaluation of the energy losses in nonisolated valves and accessories in a steam line of a chemical process (RAR-Refinaria de Açúcar Reunidas S.A.). The energy lost in the steam lines is considerably high, therefore the isolation of the pumps and accessories is of the extreme importance in order to increase the efficiency of the overall system. To evaluate these losses, two different methods were studied and the results of both were compared with standard values (BS 5422: 1990). The heat losses without isolation or with different isolation thickness values were determined in previous simulations. The results obtained in the software 3EPlus presented an average difference of 6.6% and 2.6% to the standard values (BS 5422: 1990), without or with isolation, respectively. Considering a maximum difference of 7%, it is possible to conclude that the 3EPLus produce acceptable results. The total heat energy loss in the non-isolated valves and accessories was 153 kW/year, which correspond to the consumption of 78459 kg/year of fuel, considering a boiler efficiency of 88%, but after the application of isolation the savings were 133 kW/year, which correspond to 68400 kg/year of fuel, evaluated approximately in 20.000€/year.
The main goal of this work was the evaluation of the energy losses in nonisolated valves and accessories in a steam line of a chemical process (RAR-Refinaria de Açúcar Reunidas S.A.). The energy lost in the steam lines is considerably high, therefore the isolation of the pumps and accessories is of the extreme importance in order to increase the efficiency of the overall system. To evaluate these losses, two different methods were studied and the results of both were compared with standard values (BS 5422: 1990). The heat losses without isolation or with different isolation thickness values were determined in previous simulations. The results obtained in the software 3EPlus presented an average difference of 6.6% and 2.6% to the standard values (BS 5422: 1990), without or with isolation, respectively. Considering a maximum difference of 7%, it is possible to conclude that the 3EPLus produce acceptable results. The total heat energy loss in the non-isolated valves and accessories was 153 kW/year, which correspond to the consumption of 78459 kg/year of fuel, considering a boiler efficiency of 88%, but after the application of isolation the savings were 133 kW/year, which correspond to 68400 kg/year of fuel, evaluated approximately in 20.000€/year.
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Keywords
Isolamento Válvulas Transferência de calor Espessura económica Refinaria de açúcar Insulation Valves Heat transfer Economic thickness Sugar refinery