GB1023051A - Waste material converter - Google Patents

Abstract

In the continuous production of fertilizer from garbage or dewatered sewage by aerobic thermophilic decomposition in a horizontally moving bed in a digester, a line of rotary screws or bucket conveyers is passed through the bed to raise material from the bottom to the top of the bed. 1-10% of the bed may be agitated at one time. The temperature in the bed may be 120-170 DEG F. A desired temperature may be maintained by controlling the speed of movement of the screws through the bed or by controlling the speed of rotation of the screws. According to Figs. 1 and 2 (not shown), a circular digester 11 has screw agitators 15 which are carried by a rotary carriage 20 which also carries a conveyer for feeding fresh material around the periphery of the bed. The fertilizer product flows over an inner wall 35 through an opening 34 to a conveyer 39. The screw agitators may be at an angle of 12 degrees with the vertical (Fig. 4, not shown) to aid movement through the material. Each agitator may be surrounded by a sleeve (Fig. 5 and 6, not shown) having an outlet port which may be rotated to direct material in a direction opposite to that of travel of the carriage or towards inner wall 35. Air may be drawn or forced through the interior of the agitators to outlets below the surface of the bed (Figs. 7-9, not shown). Air may also be supplied through perforated air distribution pipes near the floor of the digester or through opening 34. The carriage may carry barriers (Figs. 12-14, not shown) which prevent material passing along the surface of the bed. Alternatively, a single annular barrier may be provided (Fig. 15, not shown). In another embodiment (Fig. 10, not shown), material may pass from one side to another of a rectangular digester and the agitators may pass repeatedly in one direction across the direction of travel of the material. In a longer rectangular bed (Fig. 11, not shown), the agitators may pass down one side of the bed and up the other.