US1907202A - Means for and method of controlling furnaces - Google Patents

Description

May 2, 1933. F. .1. RYAN 1,907,202

MEANS FOR AND METHOD OF CONTROLLING FURNACES Filed April 15, 1927 AIR v 1 vs UNIT (WA T801150 6w! Tc TEMPERATURE CONTROL Patented May 2, 1 933 v (UNITE STATES PATENT OFFICE FREDERICK .LRY'AN, or PHILADELPHIA, PENNSYLVANIA, ASSIGNOR, BY MESNE As- SIGNMENTSQTQ THE LEHIGH COAL AND NAVIGATION COMPANY, OF PHILADEL- PHIA, PENNSYLVANIA, A CORPORATION or PENNSYLVANIA MEANS FOR AND METHOD OF CONTROLLING FURNACES Application filed April 15,

3 My invention relates to means for and method of cont-rolling furnaces, and it has for one object the provision of a system whereby a desiredmaterial may be automatically maintained at a predetermined temperature and in an atmosphere of desired characteristics.

Another object of my invention is to provide a system of control, whereby a treatment for the desired material requiring a predetermined temperature and atmospheric conditionmay be carried out in repeatable operations under full automatic control, so that like results may-be obtained at all times irrespective of variations due to external atmospheric conditions, slight changes in the uniformity of-the material under treatment and the like.

A further objectof my invention is to provide in apparatus ofthe character described means whereby the atmosphere in which the material under treatment is contained may beiautomatically maintained. in a reducing state.

A still further object-of my invention is to provide means responsive to different conditions of a material under treatment, whereby the material maybe maintained automatically at a predetermined temperature and in a reducing atmosphere of desired CO content, so that the final product is substantially unaffected by moisture or temperatures under 212 F.

1 A still further object of my invention is to provide in a furnace for the treatment of molded materials, such, for example, as briquettes, means for automatically maintaining the molded materials at a desired temperature, means responsive to the firstmentioned means for automatically adjusting the furnace draft, and means governed by the gases passing from the material for automatically maintaining the atmosphere in whichthe material is contained In such reor burning of the material. 7

. "Astill further object ofmy invention is to provide amethod of treating a molded granularo material and a carbonaceous binder,

ducing condition as to prevent the oxidation whichconsists in heating the granular ma- 1927. Serial No. 184,132.

terial and the binder to a high temperature v operation, whereby my invention may be.

practiced, will be apparent more fully hereinafter, when taken in connection with the accompanying drawing, wherein Figure 1 of the drawing is a view of circuits and apparatus embodying my invention, thefurnace only being shown in vertical section. a

Figure 2 is an elevational view of the motor 17 on a larger scale than in Fig. 1.

I Thebriquetting processes of the prior art have been particularly characterized by the absence of automatic control apparatus adapted to maintain desired conditions substantially constant during the heat treat]- ment. For example, the briquettes to be treated were positioned on a grate of the usual furnace chamber and a fire established under the grate for the development of the heat necessary for the briquetting operation.

During the continuance of the process there was no -means provided for automatically maintaining constant such variables as the temperature of the briquettes and the surrounding atmospheric conditions. As a result, when the treatment was at an end, the briquettes were not only burnt or ashed but also insufliciently cooked or carbonized, so

that disintegration occurred very quickly in the, presence of moisture or temperatures under 212 F.

According to my invention, I provide means whereby a desired high temperature, say 1500 F. and above and a predetermined atmospheric condition may be automatically maintained, irrespective of variables due to furnace conditions, outside atmospheric conditions and variations in the uniformity'o'f the material treated. Such treatment, moreover, may be carried out in repeatable operations under full automatic control, so that like results may be obtained at all times, repetitions being based on charts formed from instrument settings.

To this end, I provide a furnace 1 comprising an inner furnace chamber 2 and an outer enclosing furnace chamber 3. The outer chamber 3 is provided with a lower combustion portion 4 having an opening 5 for an oil burner 6 or other heating apparatus. The

combustion chamber 4 extends into engage ment with a hearth 7 which constitutes a bottom wall for the inner furnace chamber 2. The hearth may support, as shown, a material 8 which is to be processed. Such material may comprise a mixture of coal and a carbonaceous binder in desired relative proportions. The process embodying my invention also lends itself to the treatment of such materials as flue dust, iron ore, "magnetic ores and other granular substances adapted to heat treatments.

The upper walls 9 and 11 of the inner and outer furnace chambers 2 and 3, respectively, are provided with substantially aligned outlet openings 12 and 13 for the furnace gases. The outlet opening 12 for the outer furnace chamber 3 is extended by means of a stack 14 having a control valve 15, which is connected by linkage 16 to an air operated motor 17, the linkage 16 having a counterweighted lever 18 tending to hold the stack valve 16 in its normally closed position. The valve 15 may be so adjusted, however, as to insure a desired minimum passage of gases through the stack 14 from the furnace 1, for reasons as will presently appear;

The burner 6, which may take the form of that disclosed in Patent No. 1,161,183, issued November 23, 1915, to George F. Beach, is connected by an oil-feed pipe 19 to an oil valve 21 constituting one element of a valve group 22. The oil valve 21 may be connected to an oil reservoir (not shown). The oil burner ,6 is also connected by an air pipe 23 to an elongated casing 24 having a butterfly valve 25 which constitutes another element of the valve group 22. r

The air motor 17 is connected by an air pipe 26 to a pilot valve 27 which constitutes still another element of the valve group 22. Air is supplied to the valve 27 by means of a supply pipe 28, leading to a main air-supply pipe 29. One end of the pipe 29 is connected to an air blower (not shown), while the other end is connected to the casing 24. The valves 21, 25 and 27 may be operated by mechanism 31 which is connected to a solenoid 32. The mechanism 31 is provided with a plurality of adjustable abutments 33 whereby one, another or all of said valves may be independ ently or simultaneously operated and adjusted. 7 v

The zero position of the air valve 25, which may be indicated by an index plate 34, is preferably such that a minimumsupply of air is continuously assured the oil burner 6 sufficient to maintain proper combustion conditions in the furnace 1, as well as the proper'operation of the burner 6, when only the furnace losses are to be supplied, The oil valve 21 is also provided with by-pa'ss means having. a control element 35, whereby sulficient oil may be supplied to the burner ,6 when only the furnace losses are to'be' compen sated. Similarly, the closed position of the stack valve 15 is such that, for the conditions just stated, sufficient draft is established to assure the efiicient operation of the furnace 1.

The operation of the several parts of the valve group 22 from the no-load positions shown in the drawing may be effected by the energization of the solenoid 32 thro ugh'an electrical control'circuit 36 comprising a pair of conductors 37 and 38 extending from: the solenoid32 to an instrument'panel 39. p The panel'39 is also connected by thermocouple leads 41 and 42 to a thermocouple 43 which extends through a furnace wall 44 of the outer furnace chamber 3 into engagement with an underside 45 of the hearth 7. -The panel 39 is provided with temperature control apparatus 46 of known design which is responsive to variations in the thermocouple leads 41 and 42 due to temperature varia- V tions of the thermocouple43. -A relay 47 is also provided for the connection and dis-connection of the solenoid conductors'37, 38 to and from a main supply circuit (not shown), in accordance with the operation of the temperature control instrument 46. The details of these instruments constitute nopart of'my present invention and, therefore, will not be "further described and illustrated. It is also noted that certain of the constructional features ofthe valve group 22 are not shown in detail inasmuch as they are embodied in the patent to George F. Beach, granted March 17 1931, No. 1,797,118. a r a In operation, when the temperature-control instrument 46 is adjusted to the value to which it is desired to'heat the briquettes 8,

currents are supplied to the solenoid 32 through the conductors 37, 38, causing the energization ofthe solenoid 32 and the actuation of the mechanism 31. The operation of the mechanism 31 resultsin the opening of the oil valve 21, the butterfly valve 25 and the pilot valve 27 the extent of opening in each instance being determined by the adjustment of the several abutments 33. Oil and air are now supplied to the'burner 6 through the pipes 19 and 23, respectively, while air is supplied to the air motor 17 to cause the opening of the stack valve 15. The increase in the amount of oil and air thus supplied to the burner 6, as well as the increase'in'the furnace draft through the opening of *the stack valve 15, causes an incre'asein the temperature of the gases in [the combustion chamber 4, these gases passing, as indicated,

over the underside of'the hearth 7 and final ly. discharging from the outer furnace chamstack 14.

'Vihen the temperature of the briquettes 8 reaches and starts to exceed the desired value, the currents generated by the thermocou ple' as, through the medium of the temperature control instrument 16 and the relay 47, cause the open circuiting of the supply conductors 37, 38 for the solenoid 32 and the consequent de-energization of the latter. The operating mechanism 31 now drops from its raised operating position to its original po- 9 sition, with the result that the oil valve 21,

the butterfly valve 25 and the pilot valve 27 are closed, the first two valves remaining open sufficiently to supply the furnace losses. The pilot valve 27 is so constructed that when .it closes, a relief port (not shown) is opened,

permitting the air in the pipe 26 to be discharged to atmosphere, so that the counterweighted lever 18 may drop and return the stack valve to its original position.

By reason of the furnace losses, the temperature of the combustion chamber 1 and consequently that of the briquettes 8 now drops below the predetermined value, whereupon the thermocouple as, through the temperature control instrument l6 and the relay 47, again effects the connection ofthe conductors 3T, 38 to their source of energy (not shown) and thereby causes the re-energization of the solenoid 32. The solenoid 32 again actuates the mechanism 31 from its position shown in the drawing to its raised operating position, causing the opening of the oil valve 21, the butterfly valve and the. pilot valve 27 and a consequent increase in thetemperature of the briquettes 8 to the predetermined value. Thus, the temperature of the briquettesS is automatically maintained within predetermined limits, and this operation may be repeated as many times as desired, the settings of-the apparatus being to my invention, I provide means, which is responsive to the emitted or passing from the briquettes 8, for assuring automatically that said briquettes, during the carbonization period, shall be contained in a reducing atmosphere of desired characteristics.

To this end a gas-sampling tube 48 of an atmospheric instrument 49 is so mounted on the furnace that an end portion 51 thereof extends throughthe top walls9 and 11 of to a butterfly valve 64 mounted in an elon the furnace chambers 2 and 3, respectively, and terminates in a so-called I combustion portion 52 of the inner furnace, chamber 2 which is positioned immediately adjacent to the top wall ll'but'in spaced relation to the briquettes 8. A so-called reducing portion 53 of the inner chamber 2is positioned be tween the combustion portion 52Ha nd the briquettes 8 but in direct engagementwith the briquettes 8.

The other end of the sampling tube 48 terminates in a gas cell 54 such as that shown in the patent to Reineke, 1,645,350, dated October 11, 1927 and relating to Apparatus for regulating air supply,.and, as is usual in such cells, a control circuit 55 extends therefrom to agas-control instrument 56 that is mounted on a second panel board 57. The panel board 57 also supports a relay 58 which is responsive to variations in thecurrent passing through the gas-control instru ment 56 and which serves to control the connection of a solenoid-energizing circuit 59to a main-supply circuit (not shown). The relay 58 is preferably so adjusted that when the current through the instrument 56 increases, by reason of a decrease'in the C02 content of the gases passing from the briquettes 8, the solenoid circuit 59 is energized,

but that a decrease in the currents'passing through the instrument 56 due to an increase in the (20; content of the gases causes the deenergization of the solenoid circuit 59. If

it is desired that the relay 58 respond directly to the (10 content of the gasesinthe chamber portion 53, the tube 48 is lengthened sufficiently to pass through thechamber portion 52 into the portion 53. p

The circuit 59 is connected to. a solenoid 61 of a valve group 62 corresponding to the valve group 23 with the exception that the .oil valve 21 and the pilot valve 27 are omitted.

Movement of the solenoid 61, however, is lmparted through operating mechanism 63 gated casing 65, one end of which is connected bya supply pipe 66 to the main airsupply pipe 29. p

The other end of the casing is connected by an airpip-e 67 to the furnace 1. An end portion 68 of the pipe-67 passes through outer and innerv furnace walls 69 and 71 and terminates in the combustion portion 52 of the inner furnace chamber 2. The solenoid 61, the operating mechanism 63 and the butterfly valve 64 are so adjusted thativhen the solenoid 61 is deenergized, the butterfly valve 64; is closed but that when the solenoid 61is energized, the valve 64: is opened to permit asupply of air to the combustion portion 52 of the inner furnace chamber p v Hence, when the volume of gas passing from the briquettes 8 increases, so. that. there is a decrease in the CO content of these gases,'the solenoid 61is energized to cause the opening of the valve 64, thereby per mitting a sup ly of air to the combustion chamber 52. uch supply of air permits the combustion of at least a portionof the gases in the furnace portion 52, thereby increasing the furnace pressure present in the discharge opening 13 and also very greatly facilitating the process of degasifying the material 8. The supply of air to the furnace chamber 2 also prevents the formation of a vacuum 7 therein and resulting decrease in the effect of thestack 14. Desirable resultsalso follow from the heating of the upper Wall 11 of the inner furnace chamber 2. 7

Should the gases passing from the briquettes 8 decrease in volume or increase in COgcOntent, unless the air passing into the inner chamber portion 52 is correspondingly decreased, the combustion portion 52 extends down into the reducing portion or blanket 53 and finally entirely eliminates this portion and directly engages the briquettes 8, whereupon an oxidation or ashing of the briquettes occurs. This undesirable result, however,i'is prevented by'reason of the fact that when the CO content of the gases passing from the briquettes 8 increases, the currents from the gas cell 54 fall to a value that permits the relay 58 to open the energizing circuit 59 of the solenoid 61. The latter now permits the mechanism 63 to drop and thereby close the valve 64 and shut off the supply of airto the combustion chamber portion '52. The adjustment of the control instrument 56 necessary to maintain the combustion furnace portion 52 and the reducing furnace portion 53 in desired relative proportions may be previously determined upon and' charted, so that subsequent operations may be repeated as many times as desired.

Assuming that the briquettes are positioned in the inner furnace chamber 2, that the temperature-control instrument 46 is adjusted to a position corresponding to the desired treating temperature for the briquettes -8, say 2000 F. and that the gas-controlinstrument 56 is adjusted to a position at'Which the combustion and reducing portions or blankets 52 and 53 may be maintained in desired relative proportions, the temperature of the combustion chamber 4 and consequently that of the briquettes 8 increases to the predetermined temperature of 2000 F. A further increase in temperature is prevented by the thermocouple 43 causing the deenergization of the solenoid 32 through the medium of the temperature-control instrument 46 and the relay 47 Such operation of the solenoid 42 causes the closing of the stack valve 15 and the substantial inoperation of f the oil burner 6. When the temperature ofthe briquettes 8, however, fallsbelow the predetermined value,

theithermocouple 43, through apparatus just mentioned,"againcauses theopening of the nace hearth 7 and adjacent briquettes 8. Thus, the briquettes are automatically maintained at a predetermined high temperature.

The gases passing from the briquettes 53 in the beginning of the process may be excessive and this condition is compensated by means of the atmosphere instrument 49 which, through the gas control instrument 56 and the relay 58, causes the operation of the solenoid 61 and the consequent supply of an additional amount of air to the combustion portion 52 of the furnace chamber 2. The combustion portion 52 is prevented from extending'down into engagement with the briquettes 8 and thereby eliminating the reducing atmosphere 53, when the process draws to an end or there is a decrease in the amount of gas passing from the briquettes 8, by reason of the fact that the atmosphere instrument .49 causes the closing of the butterfly valve 64 and, consequently, a decrease in the amount of air supplied to the combustion chamber 52. It is thus apparent that the briquettes 8 are automatically maintained at a desired temperature and in a reducing atmosphere or blanket 53 of desired characteristics independently of outside atmospheric conditions, the furnace draft, variations in the volume of gas passing from the briquettes 8 and other conditions which, heretofore, have'resulted in the failure of the usual open-hearth briquetting process. a v The product resulting from such treatment is particularly desirable inasmuch as it is substantially unaffected by moisture as Well as temperatures under 212 F. Close inspection indicates that Where a carbonaceous binder is employed, the granular material of the main body portion of the briquettes as Well as the binder material are welded together, that is, the binder has a permanent set.

lVhile I have shown only one embodiment of my invention, for the purpose of describing the same and illustrating its principles of construction and operation, it is apparent that various changes and modifications may be made therein, Without departing from the spirit of my invention and I desire, therefore, that only such limitations shall be imposed thereon as are indicated in the appended claims or as are demanded by the prior art.

I claim: 7

l. The method of heat-treating solid carbonizable material comprising carbonizing said'material by establishing a combustion zone in spaced but direct heat radiation relation to the material by combustion of the gases emitted from the material and preventing approach of the combustion zone to the material by controlling the admission of air to said combustion zone by the percentageof CO in the gases at apoint between said combustion zone and said solid carbonizable material.

2. The method of heat-treating solid carbonizable material comprising carbonizing said material by establishing a combustion zone in spaced but direct heat radiation relation to the material by combustion of the gases emitted from the material and preventingapproach of the combustion zone to the material by controlling the admission of air to said combustion zone by the composition of the gases at a point between said combustion zone and said solid carbonizable material.

3. In a heat-treating furnace of the type described, outer and inner furnace chambers, the outer furnace chamber being equipped with a burner and a stack, the inner furnace chamber being Within the outer chamber and having an outlet at its upper part communicating With the interior of the outer furnace chamber, means for controlling the minimum cross sectional area of the stack, means for controlling the supply of fuel to the burner and for controlling the first-named means dependent on the temperature of'the outer furnace chamber,-the inner chamber including a support for the material to be treated, means for admitting air to the inner chamber at a point spaced above said support, and means controlled by the composition of gases in the inner chamber controlling operation of the means for admitting air.

4. In apparatus for heat-treating combustible materials, a chamber including a support for the reception of the material, means for heating said chamber to main tain a predetermined temperature therein, means for admitting air for supporting combustion to said chamber at a point spaced from and above the support contained in the chamber, and means controlled by the composition of gases in said chamber for controlling said means for admitting air.

5. Apparatus for heat-treating carbonaceous materials at temperatures exceeding 1500 F. comprising a chamber including a support for the material to be treated, means for admitting air to said chamber at a point above and in spaced relation to the support, a gas samples conduit communicating with said chamber, means regulated by the composition of gases in said gas sampler conduit controlling the air-admitting means, and means for heating the chamber.

FREDERICK J. RYAN.

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