Control valves in controlled pneumatic aeration processes

Summary

Through the 2013–2019 program of the Ministry of Energy and Public Utilities of the Samara Area «Samarskie Kommunal’nye Sistemy» Company has developed and has been successfully implementing the project of upgrading the municipal wastewater treatment facilities. In order to improve the energy efficiency retrofitting the systems of aeration and air distribution, equipping with compressors with controlled air supply to the aeration tanks within 45–100% range is envisaged. The general concept of control has been substantiated that includes complex level of process control and a two-loop automation scheme «aeration tank gate valve control – air blower group». The method of selecting control valves for the air supply control system for pneumatic wastewater aeration has been developed and substantiated. The method is based on the dependence of compressed media flow through the control valve stated in IEC 60534-2-1 International Standard. Under full-scale conditions with the use of precision equipment the flow characteristics of IRIS (DN300) control valve manufactured by Egger were studied. The average percentage error of the method was 6.79%. The method error does not matter much for the automated control since PID-control provides for supplying the required air amount according to the condition of compliance to О₂, NH₄ set values and current measurements of the supplied air amount. The classification of control valves is presented based on the type of the dependence of K_v/K_vs valve capacity coefficients from the rate of valve opening. Technological modes were identified: comparison of the theoretical and experimental flow characteristics of the control valve, pressure difference at the control valve, pressure difference in the «control valve – aerators» system, aerial environment temperature before the valve. The suggested method of the control valve calculation is a part of the «Energy efficiency of the controlled air supply to the aeration tanks» comprehensive mathematical model.

Key words

energy efficiency , automated control system , membrane aerator , wastewater treatment facilities , pneumatic aeration system , control valves , flow coefficient , diaphragm gate valve