Use of fly ashes from municipal sewage sludge combustion in production of ash concretes

This paper presents analysis of results of investigations of flow rate of sand (Qs) and water (Qw) in an air lift pump. The investigations were performed on an air lift pump test rig, constructed in a laboratory on a scale of 1:1. The paper describes the construction and working principle of this air lift pump test rig and presents a methodology of derivation of empirical formulas for calculation of sand and water flow rate. A comparative analysis of the values of the sand and water flow rate obtained in direct measurements with analogical values of flow rate calculated with use of the derived empirical formulas was carried out. The research scope encompassed the derivation of the aforementioned empirical formulas in the PVC air lift pump with the internal diameter of the discharge pipe d = 0.03 m by the fixed sand-water mix delivery heads H: 0.40 m, 0.80 m, 1.20 m. To derive the empirical formulas for calculation of the sand and water flow rate, dimensional analysis and multiple regression was applied. In the air lift pump being tested, the water and sand flow rate felt along with the rise in the delivery head and the water flow rate was higher than the sand flow rate. Air pressure in such devices cannot be lower than 110 kPa and cannot exceed 150 kPa as for higher values of air pressure the sand and water flow rate starts to fall. The values of the sand and water flow rate calculated with use of the derived formulas coincide very well with the values determined from the direct measurements.