Engineering and economic impacts of prohibiting recombination recirculation dust at export elevators

Abstract

The objectives of this research were to develop engineering descriptions of dust control systems currently being used in grain export facilities, to determine the retrofit requirements of the dust control and handling systems to comply with disallowed R/R, and to estimate the equipment, operation, and maintenance costs that would be incurred by the industry as a result of complying with disallowed R/R. Data were collected from seven terminal export elevators, a questionnaire was sent to all 63 export elevators, and manufacturers data for dust control equipment were collected. There were three basic types of dust control systems. Two systems were R/R which either recombined the dust upstream from the pick-up points, or reintroduced the captured dust downstream. The third system, a bin dust system, employed dust motivators (high pressure blowers) to convey the captured dust from the filters to dust storage tanks. Data from the seven elevators revealed that electrical energy costs to operate dust systems ranged from $82.3 to $238 per 1000 m3 ($2.89 to $8.34 per 1000 bu). Also, elevators handling lower volumes of grain per year would pay more for electrical energy per unit volume than those handling larger quantities of grain. Electrical energy costs were higher for elevators with larger percentages of bin dust systems. It was determined, from data from the seven elevators and the questionnaire, that a facility would collect 1. 6 kg of dust per I 000 kg (3.2 lb per ton) of grain if all captured dust were collected to storage bins. It was estimated that the industry would spend $29 million to retrofit and $35.8 million annually to comply with disallowed R/R. Also, elevators handling less then 1.76x 106 MI (SOx 106 bu) would pay as much as 13 times more per volume of grain handled in capital costs and 2 times more in annual expenditures than larger, higher volume elevators. Based on a total export volume of 168 million cubic meters (4.8 x 109 bu) per year, the grain export industry would spend 17 cents per m3 (0.6 cents/bu) to retrofit facilities and approximately 23 cents per m3 (0.8 cents/bu) annually.