Pump Performance Tests as a Method of Determining Influent Mass Flows to Dairy Farm Anaerobic Digesters

摘要

A new on-farm anaerobic digester (AD) monitoring protocol, recently released by the Association of State Energy Research Technology and Transfer Institutions (ASERTTI) is being used to assess seven anaerobic digesters on dairy farms in New York State.A key component of the ASERTTI protocol is to perform a mass balance of the AD system. Mass balance data is needed to determine system performance values such as: degree of manure stabilization, biogas produced per unit of influent, and subsequent electrical power produced per unit of influent. The optimal location in the system to obtain AD influent mass flow data is at the AD influent pump. However, pumps used to pump manure generally lack performance data, making it difficult to quantify mass flow without knowing the performance characteristics of the influent pump. In order to determine in-place pump performance, field tests were conducted on each of the two types of influent pumps used on the farms: centrifugal pumps and hydraulic piston pumps. The performance test for the hydraulic piston pump consisted of pumping AD influent to a separate vessel while counting the number of pump strokes; the wet weight per stroke was then determined. The pump test for the centrifugal pump consisted of fillingthe AD influent pit and then pumping the contents to the AD while measuring the change in depth of the pit every ten minutes throughout the test to determine the average flow rate for the dynamic pump head. To date, pump calibration tests have been performed on five of the seven farms. Volumetric efficiencies for four of the hydraulic piston pumps were found to be on average 91, 64, 83 and 57 percent based on three separate trials at each farm, pumping on average about 5,000 gallons per trial. Manure density tests performed the day of the pump performance evaluation resulted in specific gravities of 1.02, 1.01, 1.02 and 1.02, with respect to the efficiencies listed above. Average flow rates for two centrifugal pumps tested at one farm were found to be381 gpm and 564 gpm.