Patent GB-975308-A (GB)
Title: Method and apparatus for converting organic waste material
Inventor: MACDUFFIE MARSHALL
IPC: C05F17/00
Filed: 1963-02-15
Abstract: <PICT:0975308/C1/1> <PICT:0975308/C1/2> Organic waste material is advanced from a receiving area to a grinding area and then, as ground pulp, moved to a storage zone from which it is withdrawn, at a rate independent of the rate of advance to the receiving area, to a digestion zone. The pulp is continuously agitated and simultaneously linearly advanced through the digestion zone while passing air through a space above the pulp and withdrawn from the digestion zone when decomposed to a predetermined state by aerobic bacteria.  All portions of the pulp are repeatedly exposed to the air above it, which may be heated.  Waste is unloaded at doors 21-26 (Fig. 1) on to conveyers A1 and A2, manually sorted at 30-33, and passed, via conveyers B1, B2 and F1, F2 and compressors E1 and E2, to grinders G1 and G2.  Ground pulp is discharged to screens and/or magnetic separators MG1 and MG2, re-ground at J1 and J2 and passed selectively by shoots 34-39 and conveyers M1, M2, N1 and N2 to one of storage tanks Z1-Z4 (Fig. 2).  Large objects and screened matter are removed at C1-C4.  The storage tanks may be provided with perforated double floors and inlets for air or steam.  Pulp is discharged from the storage tanks by hoppers and is conveyed by belts P1, P2, R1, R2, S1, and S2, together with additives K if desired, to digestors 47, 48 where the pulp is discharged to first, third or fifth levels by plough and shoot combinations 49-54 (Fig. 3). The additives may be bacteria or phosphorus, potassium or nitrogen compounds. Provision is made for withdrawal of partially decomposed pulp by shoots 59-64 and its recycling by conveyers T1 and T2 to the digestors.  Ploughs 65 and 66 (Fig. 2) permit transfer of pulp from T1 to P2 and from T2 to P1. Completely digested pulp is carried by belts, pipes or blowers X1 and X2 to screens V1 and V2 and thence to storage areas.  Screenings may be returned by Y to belts R1 and R2.  Each <PICT:0975308/C1/3> <PICT:0975308/C1/4> <PICT:0975308/C1/5> digestor 47, 48 may consist of a series of elongated, superimposed, vertically spaced, stationary decks 101-108 (Fig. 8) held in a covered frame structure 113 provided with ladders 115. The decks may be of steel and may be formed with ridges and troughs (Fig. 11).  Pulp is discharged from conveyers S1 and S2 on to deck 101 by ploughs 117-120 and is either moved along deck 101 by rake assembly 109 mounted on endless chains passing round pulleys 127, 128 or is allowed to drop on to deck 103 through slidable gate 121 under opening 122 in deck 101. Pulp reaching the end of deck 101 falls on to deck 102, is moved therealong by rakes 109 and similarly drops to succeeding decks through open gates and is moved along these decks by rake assemblies 110-112.  Partial or total closure of a gate at any intermediate deck causes pulp to pass over the gate and fall on to a conveyer, e.g. 159, connected to shoot 160 having movable discharge section 161.  By this means, partially composted pulp is recycled via conveyers T1 and T2.  Each deck is provided with an air blower and an exhaust pipe (not shown). Pivoted baffles 129-132 prevent "short-circuiting" of the air flow.  The desired depth of pulp on the decks may be maintained by a series of transverse bars or pipes mounted on the endless chains between adjacent sets of rakes.