US2865739A - Process and apparatus for recovering zinc - Google Patents

Description

Dec. 23, 1958 G. E. ALDERSON ET AL 2,865,739

PROCESS AND APPARATUS FOR RECOVERING ZINC 2 Sheets-Sheet 1 Filed Dec. 20, 1956 R. m n N d m mm mf mmwmd/ s uu AHWRWJ w E AH v. if? 0 m WWW H 6 65m: A w

Dec. 23, 1958 G. E. ALDERSON ET AL 2,865,739

PROCESS AND APPARATUS FOR RECOVERING ZINC Filed Dec. 20, 1956 2 Sheets-Sheet 2 M IF INVENTOR. 9e E- Aldersan ugene glpod IMKGL m '-r' +0rn :35

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5 EdW/n 2,865,739 PROCESS AND APPARATUS FOR REKIUVERJING ZINC George E. Alderson, Eugene W. Wood, and Edwin A. Britney, Birmingham, Ala, assignors to i i. .5. Bullock, line, a corporation of Delaware Application December 2t 1956, Serial N o. 629,594 3 Claims. (Cl. 75-88) This invention relates to a process and apparatus for recovering zinc from waste products, such for instance as from dross resulting from zinc plating operations and the like, or, as will be apparent, from many other materials in which there is metallic zinc.

Heretofore in the art to which our invention relates, it has been customary to provide furnaces in which the zinc containing material was placed and heated. These furnaces were provided with a relatively large opening in one upper part thereof to which was connected 2. con denser. Upon heating the material to the boiling point of zinc, the zinc volatilizes, passes over in gaseous form into the condenser there to be condensed back into metallic zinc. In the operation of such furnace-condenser systems, so far as we know there heretofore has been no accurate way to determine just when the furnace was substantially out of zinc. That is to say, if the starting material contains several metals of different kinds which become red hot or molten in the furnace, it is-very difiicult to ascertain by any known temperature measurements just when the optimum point in zinc recovery has been reached. Thus, it has been customary to operate the system at full heat for a certain arbitrarily determined number of hours and then to shut it down. it is readily appreciated that there is a point, near the end of the zinc recovery cycle, at which is reached the point of diminishing return with respect to cost of operation versus the value of the zinc recovered. As stated, insofar aswe are aware there has been no previous, accurate, reliable means to determine just when this point has been reached. Consequently, there heretofore has been much waste of heat, time and labor in the operation of these systems.

in view of the foregoing a prime object of our invention is to provide a process for operating zinc furnace-condenser systems which shall be fully effective to determine the point in the heating cycle when the cost of continuing the system in operation is substantially equal to the return on the zinc then being recovered, whereby the system may be shut down at the optimum time during the cycle of operation.

Another object of our invention is to provide a process of the character designated in which the optimum shutting down time of the furnace-condenser system is determined by sensing or reading a temperature corresponding to that in the condenser and, in accordance with a predetermined variation in the condenser temperature, shutting down the system.

Another object of ourinvention is to provide a process of the character designated in which the amount of heat carried over by the gaseous zinc from the furnace to the condenser, in unit time, is the criterion or measurement which is used to determine when the furnace should be shut down and the cycle ended.

A still further object is to provide a process ofthe character designated in which the temperature reading used in determining the end of the cycle is read on the outside of the condenser, thereby eliminating the necesasars Patented Dec. 23, 1958 2. sity of having to insert temperature measuring devices into tne corrosive gases and gaseous metals inside the condenser.

A rurtner object is to provide. apparatus of the char- .xcter designated in which the condenser is provided with an outer metal shell and an inner refractory lining, a part of the shell being cutaway to expose a section of the lining, and there being placed adjacent the outer surface of the refractory lining a temperature responsive device for taking the temperature measurements of the condenser.

Another object is to provide apparatus of the character designated in which the temperature measurement just mentioned is taken from a block of metal which is held in physically closecontact with the outer surface of the condenser lining, and in which the temperature responsive device is imbedded or placed inside the metal block, thus eliminating variations in the temperature reading which might be occasioned by variations in outside temperature.

Apparatus illustrating features of our invention and which is entirely suitable for carrying out our improved process is illustrated in the accompanying drawings forming a part of this applicationin which:

Fig. 1 is a side elevational view, partly broken away and in section and showing a zinc furnace-condenser system to which our invention has been applied;

Fig. 2 is an enlarged detail sectional view taken gen erally along line II-II of Fig. 1;

Fig. 3 is a detail sectional view taken generally along line Ill-Ill of Fig. 2;

Fig. 4 is an elevational view, with certain parts removed, and showing one of the time-temperature charts in place on the recording mechanism and as the chart appears at the end of a heating cycle; and,

Fig. 5 is a detail detached view of a signal indicating device which is responsive to a fall in temperature, thus to indicate the end of the cycle.

Referring ,tothe drawings for a better understanding of our invention we show in'Fig. 1 a somewhat standard form .of zinc recovery furnace-condenser system. The furnace is indicated generally by the letter A and the condenser generally by the letter B.

The furnace may be mounted on a main trunnion lit suitably supported in A frames 11. A quadrant gear 12 may be provided on the trunnion It) and this gear may be in mesh with a gear 13 which may be rotated by a hand wheel 14, thus to'tilt the furnace when the condenser is removed, as will be explained. It will be understood that gas or other fuel is supplied to the furnace through a conduit 16 and that there are branch conduits 17 and 18 which lead to burners, one of at 19.

The condenser B isremovably coupled to communicate with an opening in the furnace end by means of a transition pipe 21. The body ofth-e condenser B comprises an outer shell of metal 22 and an inner refractory lining 23. The condenser is provided with lifting eyes 24 and it may be suitably supported on an A frame 26 while connected to the furnace.

By reference particularly to Figs. 2 and 3 it will be seen that along a side of the condenser B we cut a hole 27 in the outer metal shell 22 what rectangular portion of the outer surface of the refractory lining 2 the opening,

which is indicated along the lower edges thereof, an L-shaped plate having a horizontal bottom leg 28 and a vertical leg thus to expose a some-' We weld or otherwise secure in or the like. We prefer to insulate this block by means of a layer of insulating material 33. It will be noted that the insulating material, which may be fiber glass or the like, completely surrounds the sides and ends of the block except that surface thereof indicated at 34 which con acts the exposed outer surface of the inner lining 23.

The copper block 32 is provided with a bore 36 to re ceive a heat responsive bulb 37. The bulb 37 is connected by the usual capillary tube 38 to a time-temperature recording instrument indicated general y by the numeral 39. The bulb casing 40 may be provided with a handle 40a by means of which the bulb may be inserted in and withdrawn from the block 32. As will be understood and is quite standard in the art, the instrument 39 com rises a holder 41 which is rotatable by means of a synchronous electric motor or other clock mech nism, not shown. Mounted on the holder are changeable pacer discs 42 which are laid out to represent tem erature and hour readings as shown. The apparatus 39 is provided with an inking pen for drawing the line 43 which has been removed from the drawing for the sake of clarity. The tube 38 is connected in suitable manner to the inking pen so that the position of the pen radia'ly inward or outward of the chart varies in accordance with the tem erature on the bulb.

As shown in Fig. the instrument 39 also may be equip ed with a bellows-like expansible member 44 which actua es a switch having a stationary contact 46 and a movable contact 47 carried by the bellows. This switch contr s the circuits shown in Fig. 5, whereby upon a suitable drop in the temperature below a predetermined m nimum a s nal means such as the incandescent light 470 is energi ed through the lines 48 from a source of current. not shown.

From the foregoing the method of carrying out our improved orocess together with the method of constructing and using our improved apparatus may now be explained and understood. With the furnace charged with material contain ng metallic zinc, such for instance as dross obtained from zinc using industrial processes, the condenser is put in place as shown. The furnace is now fired bv su lying as through the line 16 and the branch lines 17 and 18 to the burners. Curve 43 begins at 43a. As the temperature in the condenser rises the curve commenees to be drawn upon the disc 42 which is rotating in the di e ion of the arrow 49. For instance, the temperature indicated bv bulb 37 on the condenser B may come u to around 500 F. within about an hour and a half after the commencement of the firing of the furnace, mav rise to around 600? F. after about eight hours after the furnace is first fired, and then may reach 700 F. after about eleven hours of the firing of the furnace. The tem erature then will remain at approximately 700 F. for about 4 hours. At that time the temperature will commence to drop and, after approximately the 19th h ur the tem erature will have fallen approximately 60 F. As has been stated, our invention is predicated upon the concept that the heat being transferred from the furnace to the condenser is taken over to the condenser by the gaseous zinc. Therefore, during the time that the condenser is coming up to temperature and during that time that the condenser maintains its maximum temperature, about 700 F. on. the bulb 37, zinc is being transferred from the furnace to the condenser in gaseous form. Heat thus is being transferred by the gaseous zinc from the furnace to the condenser. However, when the temperature commences to fall from its maximum point, we have discovered that this indicates that the furnace is now commencing to run out of metal lic zinc. Further, we have discovered that after the temperature falls as much as about 40 F. to 80 F. as indicated by bulb 37, the system has reached the point of diminishing return, namely, has reached the point where the cost of continuing the system in operation exceeds the value of the zinc being recovered. Therefore, that is the optimum time to shut down the furnace, clean it out, and recharge it for a new cycle. In order to indicate this to the operator the signal light 47a is energized by the closing of the switch 46-47 in response to the fall in temperature, telling the operator that the optimum time has come to shut down the furnace.

From the foregoing it will be seen that our invention is especially adapted to save time in the operation of zinc recovery furnaces. While we have specifically disclosed the use of our invention in association with the recovery of zinc, it will be apparent to those skilled in the art that there may be other instances in the recovery of metals and the like in which our invention may have utility. Therefore, the disclosure of the invention for use in recovering zinc and the claim setting forth the recovery of zinc are intended to disclose and claim, respectively, the recovery of other metals and the like.

In actual practice and in the operation of tin zinc recovery systems of the kind shown herein our invention has proved extremely satisfactory. Through its use we have shortened the usual average cycle time from about twenty four hours to approximately twenty hours. It will be understood that in the operation of the system, the furnace is brought up to temperature required to boil the zinc and is held substantially at that temperature during the entire process. This is accomplished by the usual furnace temperature control means, not shown. Therefore, our invention is particularly useful in those types of volatilization recovery furnaces in which the gases are corrosive or the material is apt to deposit on the temperature indicating means, making it impractical to place such means in the gases themselves. By cutting away the side of the shell to expose a part of the surface of the refractory lining we obtain a temperature reading which is substantially directly proportional to the temperature existing in the condenser. Therefore, our improved process and apparatus employs a means for continually sensing a temperature which is substantially constantly proportional to the temperature existing within the condenser. It will be understood, of course, that the temperature indicated on the chart is not the temperature existing in the condenser. We therefore utilize an indirect but proportional reading, lower than the actual temperature in the condenser, to carry out our process.

Furthermore, by checking a series of charts 42 from an individual system, We can tell when the condenser walls become excessively coated with zinc dust, commonly called blue powder. This information is useful in determining when the condenser lining must be freed of this coating.

in actual practice our invention has proved to be extremely satisfactory in operation and has resulted in tremendous savings in the operation of furnaces of the kind indicated. By making a permanent record of each cycle we are enabled to maintain a check on the operation of the system inasmuch as the time, temperature, amount of fuel used and amount of zinc recovered can be compared with the amount of zinc remaining in the furnace after the furnace is shut down, thereby to keep check on the cost of the operation, cycle by cycle.

While we have shown our invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What we claim is:

1. The process of operating a zinc recovery furnacecondenser system which comprises the steps of charging the furnace, bringing the furnace up to zinc vaporizing temperature and holding it at said temperature, continuously sensing a temperature near the outer surface of the condenser which is substantially proportionally constant to the temperature inside the condenser, and shutting down the system when said temperature of the condenser falls a predetermined number of degrees in predetermined time.

2. In a zinc condenser, an outer metal shell forming the outer surface of the condenser, an inner lining of ceramic material contacting the inner circumference of said outer shell, there being an opening in the shell exposing a section of the outer surface of the lining, a block of metal having heat transmitting properties on the order of those of copper contacting the exposed surface of said lining, means holding said block of metal in place on said lining, and a temperature responsive unit inside said block of metal whereby heat is transmitted to said unit from the condenser through said inner lining and said block of metal.

3. Apparatus as defined in claim 2 in which the block is wrapped in insulating material except on the side thereof contacting said lining, and signal means is operatively connected to said temperature unit and operable upon a' predetermined drop in temperature as indicated by said unit.

References Cited in the file of this patent UNITED STATES PATENTS 1,301,011 Scoutten Apr. 15, 1919 1,585,451 White May 18, 1926 1,712,133 Breyer May 7, 1929 1,901,543 Weaton Mar. 14, 1933 2,213,622 Carraway Sept. 3, 1940 2,282,441 Whitlock May 12, 1942 2,577,902 McGrath Dec. 11, 1951 2,749,583 Loewenstein June 12, 1956 OTHER REFERENCES The Metallurgy of Zinc and Cadmium, by Walter Ren-

Claims (1)

1. THE PROCESS OF OPERATING A ZINC RECOVERY FURACECONDENSER SYSTEM WHICH COMPRISES THE STEPS OF CHARGING THE FURNACE, BRINGING THE FURNACE UP TO ZINC VAPORIZING TEMPERATURE AND HOLDING IT AT SAID TEMPERATURE, CONTRINUOUSLY SENSING A TEMPERATURE NEAR THE OUTER SURFACE OF THE CONDENSER WHICH IS SUBSTANTIALLY PROPORTIONALLY CONSTANT TO THE TEMPERATURE INSIDE THE CONDENSER, AND SHUTTING DOWN THE SYSTEM WHEN SAID TEMPERATURE OF THE CONDENSER FALLS A PREDETERMINED NUMBER OF DEGREES IN PREDETERMINED TIME.

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