Optimization of Sulfur Sublimators Used in the Colombian Flower Industry

Abstract

Abstract The Oidio is considered one of the strongest diseases that attack the rose plantations. To control it, different alternatives are used, being the most common the application of fine sulfur powder over the leaves of the plant. To spray these powder, it is used a sulfur sublimator which warms the sulfur by electrical resistors up to the working temperature, where the sulfur is melted and evaporation takes place. The evaporated sulfur condenses forming very fine particles, which are transported by the natural convective airflow inside the greenhouse. Finally the fine powder is uniformly distributed over the leaves of the rose plants. Previous studies have found that the thermal efficiency of the commercial sulfur sublimators is less than 0.1% and that the use of these sublimators represent more than 60% of the total electrical consumption of the farm. Analytical and experimental work was conducted in order to find the optimum working temperature and the appropriate geometry of high efficiency sublimators. The work involved the characterization of commercial sublimators and the development of a mathematical model to describe the evaporation phenomena in the sublimator. Results showed that the working temperature should be 220°C, the appropriate geometry should be similar to a jar, and that the maximum attainable thermal efficiency working at 220°C is ∼2%. Based on these results, 2 prototypes of sublimators were manufactured. The new sublimators showed efficiencies close to 1%.