GB909872A - Improvements relating to the treatment of sewage and like sludges - Google Patents

Abstract

909,872. Digesters. NORSTEL & TEMPLEWOOD HAWKSLEY Ltd. April 20, 1961 [Feb. 16, 1960], No. 5429/60. Class 64 (1). Raw organic sludge is passed through anon- return valve to a preheating stage and then mixed with steam before passing vertically through a closed reaction vessel, the rate of passage of the sludge through the reaction vessel being regulated so that the emerging sludge is conditioned to the required degree and the level of the sludge is maintained constant in the vessel so that sufficient space is provided for gas given off from the sludge before being vented from the vessel. Sludge is pumped from a container 10 by a variable feed pump 11 through a non-return valve 24 to a heatexchanger 13 to be preheated. The sludge then passes through the pipe 14 to the reaction vessel 15. Steam from a boiler 22 also enters the vessel 15 by the pipe 14. Sludge passes from the vessel 15 via pipes 16 and 17 to the settlement tank 19, but when the plant is first started up then the sludge is recirculated by closing the valve 18 and opening valves 20, 21 and 23, the valve 21 being closed when sufficient sludge has entered the vessel 15. When the operating temperature is reached the valves 21 and 18 are opened and valve 20 closed. Electrical flow gauges (not shown) are connected to the valves 18 and 21 to enable the flow into the plant to be equal to the flow out of the plant. In a modified arrangement a pair of electricallyoperated probes is located within the vessel 15 to adjust the valve 18 so that the level of the sludge in the vessel 15 is constant. Electric probes 25 may also be fitted to the vessel 15 to indicate the level of sludge in the vessel. A gas relief valve 26 is fitted to the vessel 15. Fig. 2 shows the reaction vessel 15 while another embodiment, Fig. 3 (not shown), has an annular baffle depending from the roof of the vessel forming in effect a second vessel with no base. In two other embodiments, Fig. 4 and 5 (not shown), the sludge and steam enter the vessel from the top. Fig. 4 has an horizontal baffle fitted at the end of the pipe 14 and another parallel to and a short distance from 7, while Fig. 5 has an annular baffle. In Fig. 6 a secondary vessel 35 is placed inside vessel 15, and also a conical baffle 36 is provided to deflect the flow in the required direction.