US3404875A

US3404875A - Furnace for burning insulation

Info

Publication number: US3404875A
Authority: US
Inventors: Hall Isaiah Lees
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-10-19
Filing date: 1965-10-14
Publication date: 1968-10-08
Anticipated expiration: 1985-10-08
Also published as: GB1036499A

Description

Oct. 8, 1968 1.1.. HALL 3,404,875

FURNACE FOR BURNING INSULATION Filed Oct. 14. 1965 4 Sheets-Sheet 1 INVENTOR= \SAlAH LEESHALL 13 cum", 52% cmm Oct. 8, l. L. HALL FURNACE FOR BURNING INSULATION Filed Oct. 14. 1965 4 Sheets-Sheet 2 INVENTOR= ISAIAH LEES HALL Oct. 8, 1968 L. HALL FURNACE FOR BURNING INSULATION 4 SheetsSheet 5 Filed Oct. 14. 1965 \NVENTOR \SA\AH LEES HALL B CA9, Slam-m1? CGMIBL Oct. 8, 1968 L. HALL 3, 0 ,8 5

FURNACE FOR BURNING INSULATION Filed. Oct. 14. 1965 4 Sheets-$heet 4 T INVENTOR:

\SAIAH LEES HALL B3, CAM,Scvmn{Cm-M United States Patent 3,404,875 FURNACE FOR BURNING INSULATION Isaiah Lees Hall, Meeching House, Church Hill, Newhaven, Sussex, England Filed Oct. 14, 1965, Ser. No. 495,962 Claims priority, application Great Britain, Oct. 19, 1964, 42,508/64 1 Claim. (Cl. 266-37) ABSTRACT OF THE DISCLOSURE A furnace for burning insulation off of cables and for the recovery of metal from such cables comprises a smoke-burning chamber, located above and rearwardly of the hearth with a bridge wall extending upwardly and running transversely across the rear of the hearth but terminating below the roof of the hearth to define a flue entrance leading from the hearth to the smoke-burning chamber. The outlet to the chimney from said smoke burning chamber is located below the top of the bridge wall.

A second smoke-burning chamber may be located downstream in the chimney and triggered by a photosensitive smoke warning device so as to be operable only when the smoke density exceeds a predetermined level.

The present invention relates to furnaces and in particular to furnaces of the kind that are, for example, suitable for the burning off of insulation from cables and for the running off of lead and reclaiming copper from such cables.

It is an object of the present invention to provide a furnace of the kind stated that ensures maximum thermal efiiciency and minimum fuel consumption, as Well as an effective elimination of the smoke produced by the burning off process.

It is a further object of the present invention to provide a basic furnace structure that is capable of handling rubber covered cable and that is capable of maintaining the smoke produced therefrom below 50% obscurity (Ringlernann 2), which is the figure set out by the provisions of the Clean Air Act.

It is a further object of the present invention to provide a basic furnace as stated plus additional means whereby P.V.C. covered cables can be burnt off in the furnace and the numerous chemical gases generated by the burning of the P.V.C. can be eliminated. Such gases include Phosgene and HCl.

According to the present invention a furnace for the burning off of insulation from cables and for the recovery of metal from such cables, comprises a hearth that slopes downwardly towards the front of the furnace, a roof and side walls extending along the hearth, one or more burners associated with said hearth for burning off said insulation, a flue at the upper end of said hearth, said flue being closed at its upper end to form a smoke burning chamber for collecting gases generated above the hearth, one or more burners associated with said smoke burning chamber for burning the gases collecting therein, and an outlet for the burnt gases at or near the lower end of the smoke burning chamber.

With a furnace constructed in this manner all the smoke created above the hearth must first pass, preferably over a bridge wall or through checker brick, into the smoke burning chamber where it is destroyed by the burners therein before passing downwardly and outwardly at the bottom of the smoke burning chamber into a smoke stack which then conveys the destroyed gases away into the atmosphere. The smoke burning chamber is, of

course, of an adequate size to accommodate all of the smoke produced above the hearth and the burners therein may operate in a manner maintaining the chamber at approximately 900 C.

To enable the lead and copper of the cables to be recovered the hearth slopes downwardly towards the front of the furnace, said hearth also having a gentle downward slope from each of its two sides towards its centre so as to form a central gully that terminates at the front of the furnace in the form of a pouring spout.

The furnace is provided with an arched roof over the hearth and the roof, hearth, and side walls are of brick to ensure a maximum of heat radiation onto the materials being treated on the hearth. Such brickwork preferably comprises three courses to ensure long life at high temperatures and the sloping hearth is preferably covered with steel plate to withstand the raking out of the cable.

The exterior of the furnace is preferably sheathed in steel and the whole is supported by a main framework constructed of heavy steel reinforced to withstand rough usage and the high temperatures involved in the burning off of various materials in the furnace.

Mounted in each side wall of the furnace, near the front thereof, are oil or gas fired burners of the single lever self-proportioning type to ensure correct atmosphere regardless of the smoke or gases produced by the rubber, P.V.C., etc., which burners are operated in conjunction with a motorised fan. At various points along the side walls of the furnace there are also a number of forced auxiliary air supply nozzles to ensure an adequate air supply for the burning of the waste materials in the furnace, these auxiliary air supplies being additional to the air used for atomising the fuel oil if fuel oil is used or for supplying the necessary air for the combustion of the gas if gas firing is used.

Where the furnace is to be used for the burning off of P.V.C. the furnace is associated with a cooling and a scrubbing plant for eliminating the dangerous gases produced by the burning of P.V.C. before the residual gases are released to atmosphere through a stack.

In order that the invention may be clearly understood reference will now be made to one particular embodiment thereof as depicted diagrammatically in the accompanying drawings and in which:

FIGURE 1 is a side elevation, in cross section, of the basic structure of the furnaces;

FIGURE 2 is a view similar to FIGURE 1 but showing the exterior of the furnaces;

FIGURE 3 is a front elevation of FIGURE 2;

FIGURE 4 shows an optional additional smoke burning chamber associated with the smoke stack from the basic furnace; and

FIGURE 5 shows the basic structure supplemented by a gas cooling and scrubbing plant.

Referri g first to FIGURE 1, it will be seen that there is shown in cross section a furnace in which a hearth 1 is provided that slopes gently downwardly towards the front of the furnace. As is shown in broken lines in FIG- URE 3 this hearth also has a gentle downward slope from each of its two sides towards its centre so as to form a central gully that terminates at the front of the furnace in the form of a pouring spout 2. This hearth is of brickwork and is reinforced on its upper surface with steel plate 3 to withstand the raking out of the materials from the hearth.

Over the hearth 1 is an arched brick roof 4, also made of brick, said roof 4 being supported by two brick side walls 5. Extending across the rear of the hearth 1 is a bridge wall 50 that does not reach the roof 4, the res-ulting opening acting as a flue leading to a smoke burning chamber 10 described hereinafter.

In each of the side walls 5, forwardly of the furnace and spaced above the hearth 1 is a burner 6 that is illusrated diagrammatically by a rectangle and may be of any suitable form. Preferably, however, each burner is of the oil or gas fired type and of the single level self proportioning type to ensure correct atmosphere regardless of the smoke that is present above the hearth. Burners of this type are manufactured by The Wallsend Slipway & Engineering Company Limited and many other firms.

Near the rear of the hearth 1 there is provided in each of the side walls an air inlet 7 for supplying air for the burning of the waste materials on the hearth.

The arched roof 4, at its inner end, rises upwardly in the form of a bridge wall 8 and then extends rearwardly again as at 9 to form a covered flue or smoke burning chamber 10, into which the hot smoke and gases from the hearth pass over the bridge wall 50 and collect for burning by two further burners 11, also indicated diagrammatically by squares there being a burner 11 in each of the side walls supporting the top 9 of the smoke burning chamber 10. These burners 11 are preferably the same as the burners 6 and may operate at approximately 900 C., and maintained at this temperature by automatic control.

The rear of the smoke burning chamber is defined by a wall 12 that extends downwardly towards a base 13 of the furnace but is spaced from the base 13 so as to form an outlet 14 for the burnt gases. In each of the side walls of the smoke burning chamber 10, near the base 13, there is provided an air inlet 15 by means of which the necessary air to support the combustion of the burning gases is provided.

The burnt gases escaping via the outlet 14 are led into a chimney 16 that extends upwardly past a damper 17 for controlling the rate at which the gases are permitted to escape.

The whole of the brickwork is encased externally in steel 18 and is supported by a main framework 19 of steel.

At the front of the furnace there is a door 20 that is vertically displaceable by means of suitably counterbalanced hoisting gear indicated generally at 21, the sides of the door sliding in guiding channels 22 and having door sealing means 23 of any known kind for ensuring an accurate hermetic seal when the door is closed and the furnace is in operation. The door 20 has an inspection hole 24. The door 20 is preferably electrically operated and is energised through suitable switching means such that the motor driving the door is stopped when the door is fully raised or fully lowered.

Extending over the door 20 is a cowling 25 for taking away any fumes or smoke accumulating at the front of the furnace when the door is open, and also to take care of steam and smoke if materials that are being treated are quenched in water near the entrance to the furnace.

Mounted above the furnace is a suction fan 26 that extracts all the smoke, fumes, and air from the cowling 25 via ducting 27 and feeds this mixture back into the furnace via ducting 28 leading to the air inlets 7 and 15. Thus, all offensive smoke, fumes, etc., collecting in the cowling 25 are fed back into the furnace to be burnt therein before escaping up the chimney 16.

The suction fan 26 is also used to supply air to the burners 6 and 11 there being air-feed pipes 29 for this purpose interconnecting the suction fan 26 and the burners 6, 11.

It will be seen from the above, which is one example only of a basic furnace according to the present invention, that not only is the smoke produced above the hearth subjected to considerable combustion but that any smoke escaping from the hearth must pass upwardly into the smoke burning chamber 10 where it is subjected to further burning by the burners 11 before being permitted to escape downwardly via the outlet 14 and into the chimney 16. The furnace is provided with a photo-electric smoke warning device 52, such a device being positioned at any suitable locality for example in the chimney 16. Such a device may operate a flashing light and bell to indicate if the furnace is overloaded at any time and is thereby creating an excess of fumes and smoke at the flue outlet.

The temperature in the smoke burning chamber 10 is preferably maintained constant and to this end the furnace includes a pyrometer temperature indicator associated with the smoke burning chamber 10.

In the case of certain insulating materials, such as P.V.C., or in ca:e the furnace becomes accidentally overloaded, a second smoke burning chamber may be provided. This second smoke burning chamber 30, FIG- URE 4, may be mounted above and be independent of the first smoke burning chamber 10. As shown in FIG- URE 4 this second smoke burning chamber 30 is connected to the chimney 16 by means of two gas ducts, one of said gas ducts 31 acting as a smoke inlet from the chimney 16 into said second smoke burning chamber 30 and the other gas duct 32 acting as a smoke outlet from said second smoke burning chamber 30 into the chimney. This second smoke burning chamber 30 is also provided with the one or more oil or gas fired burners 33 of the kind already described with reference to burners 6 and 11. As will be seen from FIGURE 4 the second smoke burning chamber 30 includes a bridge wall 34 that projects into the chamber 30 to ensure that the smoke entering via the gas duct 31 shall pass the one or more burners 33 before escaping via the gas duct 32. An air ducting 35 receives air from the suction fan 26.

Indicated diagrammatically in FIGURE 4 is a motorised damper 36 that extends across the chimney 16 between the

gas ducts

31 and 32, which damper 36 is normally in its open position. Also shown diagrammatically in FIGURE 4 is a motorised damper 37 extending across the gas duct 31, the damper 37 normally being in its closed setting. The operation of the second smoke burning chamber 30 can be made automatic by connecting the

controls

38, 39 for the dampers 36 and 3-7 to the photo-electric smoke warning device 52 already referred to. Operation of the photo-electric smoke warning device causes the control 38 to close the damper 36 and the control 39 to open the damper 37 thereby diverting the smoke rising up the chimney 16 through the second smoke burning chamber 30 to be burnt by the one or more burners 33 before escaping up the chimney, the photo-electric smoke warning device bringing the one or more burners 33 and the flow of air through the ducting 35 into operation during this period. Alternatively the photo-electric smoke warning device can be used to operate a flashing light and/ or a bell, as already stated, to indicate that the smoke obscurity is beyond 50% and to indicate to the operators of the furnaces that the

dampers

36 and 37 of the furnace must be manually operated to divett the smoke rising in the chimney 16 into the second smoke burning chamber 30.

When dealing with cables covered with P.V.C. there are, as already stated, numerous chemical gases to be eliminated, such as Phosgene, and HCl, these gases being produced by the burning of the P.V.C. To eliminate these gases the furnace may be associated with a gas cooling and scrubbing plant of any suitable known form. Such plant may be connected to the furnace, for example below the damper 17 shown in FIGURE 1 so that when the damper 17 is closed the gases rising up the chimney 16 are forced to pass through said cooling and scrubbing plant.

As shown in the particular embodiment illustrated in FIGURE 5 a ducting 40 is coupled to the chimney 16 at a point below a damper 41 extending across the chimney 16. The ducting 40 leads to the top of a cooling tower 42 containing a number of sprays that are supplied with water via a pipe 43, there being also a pipe 44 connected to the cooling tower 42 said pipe 44 being used to supply a dilute solution of caustic soda to a jet at the top of the cooling tower.

The cooled gases are conveyed from the bottom of the cooling tower 42 to a gas washer 45 having a drain cock 46. Finally, an extractor fan 47 removes the purified gases from the gas washer 45 and directs them into an exhaust stack 48, preferably fibre glass lined, for discharge to atmosphere. A motorised or manually controlled damper 49 is included in the ducting 40 so that the cooling and scrubbing plant can be shut off from the chimney 16 when not required, under which conditions the damper 41 will be opened.

The above described gas cooling and scrubbing plant is by way of example only and any other suitable cooling and scrubbing plant may be substituted therefor.

Having now described one particular embodiment of the invention it will be appreciated that many modifications thereof are possible as may fall within the scope of the appended claims.

Thus, for example, although only one air inlet 7 has been shown on each side of the hearth there may be a plurality of such air inlets at spaced distances apart along the hearth.

Also, whereas the suction fan 26 has been described as taking its entire air supply from the cowling 25 it will be appreciated that such a fan can take an additional supply of air from some other additional position should this be deemed desirable.

Also, whereas the burners 6 and 11 have been shown as being disposed in the side walls of the furnace such burners may be replaced by, or supplemented by, burners situated in the roof 4 and in the top 9 of the smoke burning chamber 10.

The fuel supply lines to the burners 6 and 11 have not been shown in FIGURE 2 since these may be arranged in any convenient manner.

It will -be appreciated that the furnace can be used to deal with materials other than electric cables and the like and that these have been quoted by way of example only.

It is also within the scope of the present invention to provide two furnaces arranged as a single operative unit in a side-by-side relationship in order to provide a unit having double the capacity of a single unit. The advantage of such a construction is that for double capacity, the two furnaces can share a common cowling 25 extending across the door of each furnace, and further economy can be effected by utilising a single suction fan 26 to supply air to the furnaces. Also, if desired, one final outlet chimney may be provided.

If a scrubbing plant is associated with such a unit, further economy can be effected since the scrubbing plant will not be very much larger for two furnaces than for one.

With two furnaces arranged as a single operative unit, the unit can be more effectively operated if one unit is used for running of lead from waste cables and the like whilst the other furnace is used for burning off rubber since the final gases passing up a common outlet chimney would then be less intense, as smoke, than the gases produced by a single furnace burning off rubber, the reason for this being, of course, that the practically smokeless gases from the furnace running off lead will mix with the gases escaping from the furnace burning off rubber before passing up a common outlet chimney. Similar considerations apply if one furnace is used for burning off a mixture of goods, some of which incorporate P.V.C., and the other furnace is used for running off lead or burning off rubber since the resulting mixture of gases passing up a common chimney would then contain a smaller percentage of poisonous gases as produced by the P.V.C. goods than a single furnace burning off P.V.C.

Operation of the two furnaces in this manner can result in the elimination of the scrubber plant if too great a concentration of P.V.C. is not present in the one furnace.

What I claim is:

1. A furnace for burning insulation off of cables and for recovering metal from such cables comprising:

a hearth sloping downwardly towards the front of the furnace;

front and side walls and a roof extending over and along said hearth to thereby define a first burning chamber;

first burner means in said burning chamber for generating heat to burn insulation off of cables placed therein;

a bridge wall extending upwardly and running transversely across the rear of said hearth, said bridge wall terminating below the level of the first burning chamber roof to thereby define a flue opening;

said flue leading to a smoke burning chamber disposed behind and above said hearth, said smoke burning chamber having a roof at a higher elevation than that of the first burning chamber roof;

second burner means in said smoke burning chamber for burning the smoke and gases located therein;

an outlet to a chimney from said smoke burning chamber located below the level of the top of said bridge wall;

a photoelectric smoke warning device mounted at the outlet of said smoke burning chamber to trigger a flashing light and bell to indicate when the furnace is overloaded and is creating excess fumes and smoke;

and a second smoke burning chamber located adjacent said chimney and downstream from said first smoke burning chamber outlet, said second smoke burning chamber including an inlet duct through which smoke from said chimney may enter, third burner means, and an outlet duct through which smoke returns to said chimney, said inlet and outlet ducts being provided with motor-operated dampers connected to and controlled by said photo-electric smoke warning device, whereby said inlet and outlet ducts are opened to permit said second smoke-burning chamber to function only when the unburned gas and smoke content of said chimney exceeds a pre-selected limit,

References Cited UNITED STATES PATENTS 2,051,463 8/193 6 Barker 266-40 2,729,301 1/1956 Ekstrom 26631 X 2,832,585 4/1958 Hansen 26631 2,964,304 12/1960 Rice 2663l X 2,995,354 8/1961 Tunder et al 266-31 3,129,932 4/1964 Richaud 26327 3,190,747 6/1965 Namy et al 26631 X 3,271,134 9/1966 Derham 26633 X J. SPENCER OVERHOLSER, Primary Examiner. E. MAR, Assistant Examiner.