Patent GB-455604-A (GB)
Title: Improvements in method of and apparatus for disposing of sewage and other municipal waste
IPC: F23G7/00
Filed: 1935-01-21
Abstract: 455,604. Disposal of sewage. DUNDAS, W. A., 1234, Cherry Street, Winnetka, Illinois, and HARRINGTON, P., 3240, North Lake Shore Drive, Chicago, both in U.S.A. Jan. 21, 1935, No. 1996. [Class 34 (ii)] [See also Groups XII and XXXVII] A method of treating sewage and other municipal waste includes the steps of drying the material by contact with a stream of hot gas while it is in loosely suspended condition without mechanical support, comminuting the material, burning the dried material and utilizing heat derived from the combustion for supplying heat to the gas. Various forms of apparatus are described with electrical means for controlling motors of conveyers and fans. Liquid waste 10, Fig. 1, is passed through a cloth covered vacuum drum 11a divided into chambers 11c whereby a partial vacuum is maintained during rotation of the drum in connection with suction pipes 12. Sewage adheres to the surface of the drum till it reaches a scraper 14 and is assisted by pressure from a pipe 15 to be free of the drum and fall into a hopper 17. A quantity of previously dried sewage is mixed with it, being conveyed on a belt 21. The mixed material is fed by a screw 18a driven by a motor 19 to a drying tower 20 where it is ground by rotary chopping devices 23 and falls through the tower where it meets a stream of hot air through a conduit 24. The air is heated to about 1500‹ F. developed in the incinerating stages. The heated air is controlled by a valve 25 and on meeting with wet material is cooled to a safe heat of 800- 900‹ F. The material then passes to a pulverizing and drying mill 27 in which a series of discs 29 and beater arms 30 pivoted thereon are mounted to rotate about a shaft 28 which also carries a fan 31 driven by a motor 28. Finely divided material, air and steam pass upwards past a motor driven fan 33 into a separator 36 provided with cone-shaped walls 36a, 36b. Vapour is discharged through a conduit 40 but solid matter passes partly to a conduit 41 to the belt-conveyer 21 and partly to a conduit 42 and thence to a drying tower 43 similar to that at 20. Lump coal may be supplied by a hopper 46 and ground by the pulverizer beneath. Ground material passes by a conduit 50 to an enclosed incinerating furnace 52. A conduit 53 delivers heated air adjacent the conduit 50 for the purposes of combustion. Ash drops out at 52c. Hot gases pass out at 55 either to the atmosphere at 56 or at 56a to a preheater 58. Air is drawn in at 64a round the wall of the furnace and upwardly, by a conduit 60 through coils 59, heated by furnace gases, and thence by a conduit 24 to the tower 20. Cold air enters by a damper 65a. Dampers 57 and 65a opening to the atmosphere may be electrically controlled responsive to temperature conditions. A second preheater 68 may be added and other separators 71 for ash. The motors for driving the conveyer, first and second stage pulverizers, exhauster fans, preheater fans and induced draught fans have interlocking control to prevent clogging with wet sludge or burning due to hot gases in an empty tower &c. Three phase electric current supply is used but two phase or direct may serve. Three electric conductors 80a, 80b, 80c, Fig. 2, lead from a three phase source to two series of bus-bars 81a, &c. 82a, &c. The series 81a supplies motors for preheater fans, induced draught and second stage pulverizer, while bus-bars 82a &c., supply motors for the conveyer, first pulverizer and exhauster. As regards the motor 26a driving the second pulverizer the three bus-bars 81a &c., are connected through three conductors 83a &c. and contactors 84 of a starter 85 with conductors 86a &c. connected with the motor terminals. The starter 85 has its contactors 84 connected for operation by a rod 87 actuated by a series of mechanical connections leading to a closing coil 88. This coil is connected across one phase of the circuit through overload relay coils 89, contacts 90, conductor 91, momentarily contacting push button 92 and conductor 93. The contactors are selfmaintained. In case of an overload on the motor 26a excess current through conductors 86a, 86c and relays 89 open contacts 90 and de-energize coil 88 opening contactors 84 to open the motor circuit. In a similar way starters 85a &c., establish control of motors 72, 39, 62. A circuit breaker 100 is interlocked with circuits of starters 85, 85a, &c., through a reset-relay 120, Fig. 4. When any one of the motors 26a, 39, 62 or 72 is thrown out of operation by any one or more of the circuit breakers, the coil 106 of the circuit breaker 100 is automatically short circuited by deenergizing coils 88 and to eliminate the short circuit and permit the breaker 100 to be again closed the reset relay 120 is operated. Assuming the contact members 101, Fig. 3, are open as when the sludge disposal system is not in operation, the first step to eliminate the short circuit and permit the closing of the. circuit breaker 100, Fig. 4, is to turn the handle 133 of the reset relay, rotating the shaft 121 through 90‹ until the contact member 122 breaks connection between the stationary contacts 126. With the opening of the connection between the contacts 126 by rotation of the handle 133 the short circuit of the coil 106 is eliminated so that when the contacts 101, Fig. 3, are closed by the manipulation of the handle 104, the coil 106 may be energized thereby to operate the latch 107 to hold the circuit breaker in its closed position. Assuming one or more of the motors 26a, 39, 62 and 72 have been stopped and all the motors have been subsequently started in operation again with the opening of all the contacts 135, 135a &c., Fig. 4, it is then necessary to energize the coil 132 to effect the resetting of the relay 120 and this is brought about by current from the line conductor 80a through conductors 112, 138, 148 contacts 129, 125, conductor 147, coil 132, conductors 146, 144, resistor 143, conductor 142, contacts 124, 128, conductors 141, 115 back to line 80b. When the coil 132 is thus energized, the plunger 131 is elevated and the cam and shaft return to normal under the spring 134. To prevent any of the motors 19, 26 or 34, Fig. 1, or any connected to 82a &c., starting before all of the motors 26a, 39, 62, 72 have been started, a circuit breaker 150, Fig. 4, is connected to the line conductors 80a, &c. at a point between the connections which are made to the bus-bars 81a, &c., and the connections which are made to the bus-bars 82a &c. This circuit breaker is similar in construction to the circuit breaker 100. The coil 153 is connected to the closed circuit between the conductors 80a, 80b at the time the reset relay 120 has been reset following the opening of all the contacts 135, 135a, &c., and the starting of all the motors 26a, 39, 62, 72 so that the circuit breaker 150 may then be operated to close the circuit to the bus-bars 82a &c., thus the coil 153 will be energized and will latch this circuit breaker in its closed position. Thus the circuit breaker cannot be closed until after the previous closing of the circuit breaker 100 with the resulting operation of closing the contacts 110. The contactors 161, Fig. 2a, constitute parts of the motor starter 163 which is substantially similar to the motor starter 85, shown in Fig. 2. The motor 26 for driving the pulverizer 29 is operated by a starter 163a and the motor 19 by a starter 163b. These starters are similar to the starter 163 except that interlocking connections are provided so that the starter 163a cannot be operated until the starter 163 has been actuated to start the motor 34 and the starter 163b cannot be operated until the starter 163a has been started to actuate the motor 26. Connections are made from the starter 163b to the contact 175 of the starter 163a so that the starter must be actuated to close the circuit of the motor 26 before the starter 163b may be actuated to close the circuit of the motor 19 and establish a circuit through the coil 165 of the starter to prevent hot gas flowing into the drying tower 20, Fig. 1, and pulverizer 27 in case any of the motors break down. The damper 25 is automatically controlled by a coil 180, Fig. 2, between conductors 160b and 160c leading to the motor 19. As shown in Fig. 5, the damper 25 is mounted on a shaft 181 in a section 24a of the conduit and has a weighted arm 182 normally closing the damper. After manual opening it can be held by a cam 184 with a notch 184a engaging a plunger 185 which serves to latch it while operating as the core of the coil 180. When the coil is de-energized the plunger 185 falls and the damper closes shutting off the tower 20, Fig. 1. Similarly the same result is brought about if either of motors 26, 34 is stopped.