Measurement of air flow through MSW-sewage sludge compost

摘要

Tests were carried out on an immature municipal solid waste (MSW) and sewage sludge compost to determine the resistance to airflow through this material. The material was contained in a 3-section, plywood column with a 0.36 m2 square cross section.Air was blown through the material using a 1.5 kW centrifugal fan at varying rates and the pressure drop across the material was measured with a simple u-tube manometer. Three depths of material were tested: 680, 1450, and 2200 mm. At each depth, the pressure drop was a power function of flow rate and the coefficients and exponents varied linearly with depth of material. The general equation describing all the data was: DELTAP = (101637H + 173473)Q(0.0126H + 1.1998) where DELTAP, Q, and H are pressure drop (Pa), flow rate (m3/s), and depth (m), respectively. Limited tests were carried out on material that had been allowed to stand in the column for 2 weeks. During this time, the material settled by about 10% of its original depth and the flow resistance was increased substantially. This points to the need to turn or loosen the material to maintain porosity and facilitate airflow. In addition to measuring flow resistance, flow uniformity was also investigated. This was done by measuring the velocity ofair passing through holes in a plywood plate laid on the surface of the compost. These measurements indicated that flow uniformity over the column cross-section increased with flow rate and depth of material.