US3535407A

US3535407A - Method of autoclaving building blocks

Info

Publication number: US3535407A
Application number: US698264A
Authority: US
Inventors: John W Pike
Original assignee: Struthers Scient & Intern Corp
Current assignee: Struthers Scient & Intern Corp; Struthers Scientific & Intern Corp
Priority date: 1967-01-20
Filing date: 1968-01-16
Publication date: 1970-10-20
Anticipated expiration: 1987-10-20
Also published as: GB1211221A

Description

Oct. 20, 1970 J. w. PIKE METHOD OF AUTOCLAVING BUILDING BLOCKS 5 Sheeds-Sheet 1 Filed Jan. 16, 1968 m Q9 ,5 kg 8 8 m9 zq imfi 1+ 3 vw wwwx mm F @255 v .w H @m Q 9v v m m m mm m, ND MP1,; 1.1 A F mw UH}- m a QR T i mm mm mm mm mm mm mm mm rial Oct. 20, 1970 J. w. PIKE 3,535,407

METHOD OF AUTOCLAVING BUILDING BLOCKS I Filed Jan. 16, 1965.: s Sheets-Sheet g Oct. 20, 1970 J. w. PIKE 3,535,407

METHOD OF AUTOCLAVING BUILDING BLOCKS Filed Jan. 16, 1968 3 Sheets-Sheet 5 United States Patent US. Cl. 264-37 3 Claims ABSTRACT OF THE DISCLOSURE An indirectly heated autoclave for building blocks has a heating tank containing coils which are used for the indirect heating of Water in the heating tank when the indirect heating capacity is not needed for the autoclave. This provides a source of heated water to shorten time between autoclaving cycles.

This invention relates to autoclaves, and to a method of operating the same. The invention is of particular utility in the curing of concrete blocks, and the description herein will refer specifically to such articles; but it is to be understood that the invention is not so limited. The essential features of the invention may be employed in the steam treating of other articles.

In general the invention comprises both method and apparatus, and wherein an autoclave system is provided with a tank adjacent the autoclave. The autoclave itself is provided with a darn at the door end, to retain water in the bottom thereof of sufiicient depth to cover pipe coils also in the bottom of the autoclave chamber. These coils are supplied with hot oil or other fluid medium, heated at some external location, whereby the Water in the bottom of the autoclave is heated and vaporized to build up the desired steam pressure, and to hold that pressure for the predetermined cycle time for the particular articles being treated or cured. During the holding cycle, steam condenses on the sides of the autoclave and on the equipment and material therein, and merely runs down to the bottom thereof where it is again vaporized by the heating coils. At the end of the cycle time, a valve may be opened providing communication between the upper portion of the autoclave and the tank previously mentioned. This equalizes the pressure in the autoclave and the tank, which in the case of curing concrete blocks is of the order of 150 p.s.i. The water in the bottom of the autoclave is at a temperature of about 365 F. When the pressure is equalized in the autoclave and tank, a pump is operated to pump the hot pressurized water from the autoclave into the tank. and the previously described valve is then closed to seal the tank and retain pressure therein. A vent valve communicating with the autoclave is then opened to relieve pressure and exhaust the remaining steam therefrom. The vented steam is directed into a muffler tunnel.

This invention also provides, exterior from the autoclave, a water heating tank which may be in addition to the tank mentioned above or may comprise this tank. Coils are disposed in the heating tank to receive the hot oil or other fluid medium which is externally heated. During the holding cycle, whether or not it is desirable to retain the water heated in the autoclave, additional makeup water can be heated in the heating tank. Once the autoclave has had water in it brought to a desired curing temperature and pressure, additional heat need only be added to balance heat losses. The oil or other fluid heating capacity may then be applied to raising cold makeup water in the heating tank to a desired temperature and pressure. This heated makeup Water may then be introduced into the auto- Patented Oct. 20, 1970 clave at the start of a subseqeunt cycle to reduce the time between cycles.

At the end of each cycle after the pressure in the autoclave is reduced to atmospheric, the door thereof is opened and the cured blocks removed. The autoclave is then charged With a fresh batch of blocks to be cured, and again closed. The pump previously referred to is then operated to pump hot pressurized Water from the tank into the autoclave; and, since the water is at a high temperature and pressure, when it enters the autoclave at atmospheric pressure, it immediately flashes into steam. Circulation of the heating medium through the water in the bottom of the autoclave is again started, and the previously described cycle is repeated.

If it is not desired to retain water in the tank referred to above, or if only some of the water needed is retained in this tank, additional preheated water from the heating tank is introduced into the autoclave.

In the curing of concrete blocks a substantial amount of water is introduced into the system by evaporation from the blocks themselves. This water also collects in the bottom of the autoclave where it overflows a level control dam and is discharged or collected for reuse.

The novel system described briefly above offers many advantages. The fired heater for heating the oil or other heat transfer medium operates at a low pressure; and, since the autoclave itself is an unfired pressure vessel, a licensed fireman or stationary engineer is not required. No high pressure boiler is used. In localities where water is expensive a considerable savings results in the recovery and reuse of condensate. However, the water may be economically treated chemically, which would otherwise be too expensive, and thus eliminate or minimize rack corrosion. The recovery and reuse of condensate permits a very substantial heat conservation with subsequent savings. If desired, blowdown steam can also be condensed and recovered.

Whether or not heated Water from the autoclave is con served, the heating tank of this invention allows minimum time loss between cycles. This is particularly important during the peak building periods durng the year when block making facilities are often operated at capacity for 24 hours each day.

It is therefore an object of this invention to provide a method of operating an autoclave system which results in the conservation of heat and water and a substantial acceleration of the cycling time.

Another object of the invention is to provide a method of operating an autoclave system that is highly economical and reliable in operation.

Still another object of the invention is to provide a method and apparatus in an autoclave system whereby hot condensate is stored for reuse in a subsequent cycle.

Still another object of this invention is to provide a method of operating an autoclave system with a minimum loss of time between cycles, the autoclave system having a given external heating capacity.

Still further and additional objects and advantages will become apparent to those skilled in the art as the description proceeds with reference to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic plan view of an autoclave system according to the present invention;

FIG. 2 is a diagrammatic side view of the apparatus shown in FIG. 1;

FIG. 3 is an enlarged transverse sectional view taken substantially along the line 3-3 of FIG. 1;

FIG. 4 is a further enlarged fragmentary sectional view taken along the line 4-4 of FIG. 3; and

FIG. 5 is an enlarged transverse sectional view taken along line 3-3 of FIG. 1 through the heating tank of this invention.

With reference particularly to FIGS. 1 and 2, a more or less conventional autoclave 2 is shown which comprises a tank-like structure defining a pressure chamber having an openable sealing door 4 at one end thereof. Inside the chamber 2 are tracks 6 (see also FIG. 3) upon which cars or carts may be rolled to load and unload the autoclave with the articles to be treated. A pipe 8 is arranged along the bottom of the autoclave chamber, and as shown, is sinuously arranged therein but may be arranged in parallel lengths connected to common headers at their ends. Any other suitable arrangement, however, could be employed and applicant will herein use the term coi to refer to the pipe 8.

As shown in FIGS. 3 and 4, the autoclave is provided with a transverse dam 10 defined by an upright plate of steel or the like at the end thereof near the door 4. The dam 10 extends to a sufiicient height to retain water in the bottom of the autoclave to a level sufficient to cover the coil =8. It is to be noted that the water level is below the level of the tracks 6. The tracks 6 are mounted on spaced blocks or the like 12 providing a space therebetween to permit condensate to run down the inside surface of the autoclave to the bottom thereof.

The forward end of the coil 8 is connected through a conduit 14 to a suitable heater 16. The conduit 14 is provided with a valve 18 therein. As diagrammatically shown in FIGS. 1 and 2, the heater 16 is fed by a pump 20 through a conduit 22 from a supply of oil or other heating medium in an expansion or supply tank 24. The expansion tank 24 is connected, through conduit 26, to a fitting 28 at the rear end of the autoclave and an internal conduit (not shown) connects the fitting 28 to the rear portion of the coil 8, thus defining a closed circulation system. It is obvious that, with valve 18 open and pump 20 operating, oil is pumped into the heater where it is heated to the high temperature necessary and thence through the coil 8 where it heats the water held in the autoclave by the dam 10. The oil circulates through the coil 8 and fitting 28, thence through conduit 26 back to the pump 20, the inlet side of which is in communication with the expansion tank 24.

A condensate storage tank 30 is provided adjacent the autoclave chamber 2 and the upper portion of tank 30 is connected through conduit 32 to the upper portion of the autoclave 2. A selectively operable valve 34 is provided in the conduit 32.

A pump 36 having an inlet 38 and an outlet 40 (see FIG. 1) is connected through the piping shown to the tank 30, the bottom portion of autoclave 2 and to a source of makeup water, not shown. By manipulating the

valves

42, 44, 46, 48 and 50, in a manner to be described, the pump 36 may be operated to pump condensate from autoclave 2 into tank 30, to pump the water from a source of makeup water either into the autoclave 2 or into the condensate tank 30, all as will be described in greater detail.

A vent conduit 52 communicates with the interior of the autoclave, at the bottom thereof, and is provided with a vent valve 54. The vent conduit 52 terminates in one end of a muffler tunnel indicated in FIGS. 1 and 2 generally by the numeral 5 6.

Referring further to FIGS. 1, 2 and 5, the heating tank 100 of this invention is mounted on legs 101 and contains the heating coils 102 within its lower portion. Valve 103 may be opened to allow pump 36 to introduce feed water into tank 100 through pipe 104 and valve 105 may be opened to allow heated feed water in tank 100 to flow through pipe 106 into autoclave 2. By completely or partially closing valve 110 in hot oil line 26 and opening or partly opening valve 111 in line 112, hot oil or the like can be made to flow through the heating coils 102 of heating tank 100 to heat feed Water 115 therein. The hot oil or the like flowing through the coils 102 returns to the oil circulating system through pipe 116.

In first starting the system for its initial cycle of operation, the heater 16 is fired to start heating the oil therein.

Valves

42, 44 and 48 are closed, as are the valves 18 and vent valve 54 along with equalizer valve 34. The pump 36 is then started with

valves

46 and 50 being open, to pump an initial supply of water into the autoclave 2. It is assumed that the autoclave has been charged with concrete blocks to be cured and the door 4 remains open. When the level of the water reaches the top of the dam 10, as determined visually,

valves

46 and 50 are closed, pump 36 is stopped, and door 4 is closed and locked. It is further contemplated that a suitable level control device (indicated schematically at 84 in FIG. 1) be provided to detect lowering of the water level in the autoclave, during a cycle of operation, to too low a level. Any overflow from the dam 10, due to gain in water by evaporation from the blocks being cured, is discharged through any suitable trap of well-known design (not shown).

When the autoclave 2 has thus been charged with the required amount of starting water, the valve 18 is opened and pump 20 started in operation to commence circulating hot oil through the coil 8. The hot oil heats the water in the autoclave to produce steam. The air trapped in the autoclave upon charging the same with the articles to be cured, is vented through suitable thermostatic vent devices 82. The vent devices 82 are of conventional construction and are well known in the art. They remain open as long as air flows therethrough but closes when the flow of air stops and steam begins to fiow out. Thus all of the air is exhausted from the autoclave by the initially produced steam and the autoclave is then sealed so that steam pressure can build up to the required level. In curing concrete blocks it has been found desirable to heat the oil in heater 16 to a temperature of about 550 F. It is further contemplated that pressure control means be provided to limit the steam pressure in the autoclave to about p.s.i., the water in the bottom thereof then being at a temperature of about 365 F.

When the curing pressure has been attained automatic valves (not shown) function to permit flow of only the amount of oil necessary to revaporize condensate within the autoclave, the only heat loss from the system being by radiation and condensation. All the steam that condenses within the autoclave flows to the bottom thereof and is continuously re-evaporated during the holding or curing cycle.

After the predetermined cycle time has elapsed and the concrete blocks completely cured, flow of hot oil through the coil 8 is stopped by closing valve 18 and stopping pump 20. Thereafter equalizer valve 34 is opened, which permits high pressure steam from the autoclave to enter the condensate storage tank 30 and to equalize the pressure in the two enclosures. After the pressure is thus equalized, valve 48 is opened to provide communication between the bottom of the autoclave and the inlet to pump 36. Valve 44 is also opened and pump 36 is started to pump all of the hot pressurized water from the autoclave 2 into the condensate storage tank 30. After all of the Water has been thus pumped into the tank 30, the

valves

48 and 44 are closed, as is valve 34, to seal the tank 30 and retain the water therein at the high pressure of 150 p.s.i. At this time nothing but steam is left in the autoclave 2. The vent valve 54 is now opened to exhaust steam'from the autoclave into the mufller tunnel already described and to reduce the pressure in the autoclave to atmospheric. Thereafter the door 4 is opened and the cured blocks are removed for use. The autoclave is then recharged with a new supply of blocks to be cured and the door 4 is closed and sealed before water is introduced. The vent valve 54 is then closed and

valves

42 and 46 are opened. Pump 36 is then started and pumps the stored hot pressurized water from the storage tank 30 into the autoclave 2. The level control device previously referred to may be in control of the pump 36 at this time to stop the same when the desired water level is reached. Under the temperature and pressure conditions described, entry of the hot pressurized water into the autoclave results in immediate flashing of the same into steam, due to the reduction in pressure thereon from 150 psi. to atmospheric. Any air in the autoclave is exhausted through the thermal valves 82 previously described and when the required level of Water is achieved in the autoclave, pump 36 is stopped and

valves

42 and 46 are again closed. Valve 18- is then opened and pump 20 is started and the previously described cycle is repeated.

It is to be understood that, while manually operated valves have been shown and described for the sake of simplicity, a completely automatic control system of any well known type could be employed to cause the sequence of operations herein described to be performed automatically. It is also to be understood that the tank 30, shown separate from the autoclave 2, may be an integral part thereof in the form of a compartment therein.

It is obvious that, since the heat required to hold the autoclave to the required curing pressure is quite small, a series or bank of similar systems may be served by the same heater 16. Such a series of systems would have their cycles staggered so that only one of them would be starting its cycle at a time, the remaining autoclaves being in the holding portion of their cycle and thus requiring only a small amount of heat. The horizontal portion 58 of the muffler tunnel 56 would then be arranged to extend in such direction as to be accessible to all of the autoclaves in the series and would serve as a muffler for each of them.

The storage tank 30 hereinbefore described is not a necessary part of this invention and may be omitted if desired, or the heating tank 100 itself may be used as a storage tank in the manner described. If it is not desired to conserve heated water in the autoclave 2 between cycles, cold feed 'water may be introduced into tank 100. After water in autoclave 2 has been heated to a desired temperature and reaches a desired pressure, comparatively little heat is required to compensate for heat losses from the autoclave 2. Thus

valves

110 and 111 may be manually or automatically adjusted so that at least a portion of the hot oil flows through coils 100 to preheat feed water therein. If water in autoclave 2 is drained off between cycles, the preheated feed water 115 will greatly shorten time required between cycles. The preheated feed water 115 may be heated to as high or even a higher temperature than that required in autoclave 2.

Even in the event that several autoclaves 2 are served by one heating tank 100, which may also be used as a storage tank .30, a given oil heating capacity may be used to preheat feed water. Even if hot water is conserved from autoclaves 2, this water is usually drained off after several cycles as impurities concentrate in it. Thus when fresh feed water is to be used, it may be preheated in the heating tank of this invention to save time between cycles.

In practice, cold feed water introduced into a conventional autoclave 2 may require up to four hours to be brought to a desired temperature and pressure. The conserving of autoclave water from a previous cycle or the preheating of new feed water may save over two hours of this between cycle time.

Heating tank may also be used to produce steam for other uses.

In summation, this invention consists of the process of autoclaving articles adapted to undergo chemical transformation upon subjection thereof to high temperatures and pressures, comprising the steps of:

(1) Supporting said articles out of contact with liquid water within a first closed chamber provided therein with a reservoir of water;

(2) Heating indirectly by an indirect preheated source of heat submerged in said reservoir and thereby vaporizing at least a portion of said water for the development of steam pressure and for the effecting of chemical transformation of said articles;

3) Exhausting steam from said first chamber, thereby relieving said steam pressure within said first chamber to remove autoclaved articles therefrom; and

(4) Preheating feed water in a heating tank by the indirect source of heat after the first closed chamber is brought to a desired steam pressure thereby providing hot water for use in a subsequent autoclaving operation.

What is claimed is:

1. In the process of autoclaving articles which undergo chemical transformation upon subjection to high temperatures and pressures, the steps of:

(a) supporting said articles out of contact with liquid water within at least one closed chamber containing a reservoir of 'water;

(b) heating a non-aqueous heat transfer fluid outside said at least one closed chamber;

(c) passing the heated transfer fluid through coils in the reservoir to develop and maintain steam pressure within said at least one closed chamber;

(d) providing a heating tank for water;

(e) passing at least some of the heated heat transfer fluid through coils in the heating tank heating make up water therein to provide at least some heated water for use in subsequent autoclaving cycles;

(f) exhausting steam from said at least one closed chamber and removing autoclaved articles therefrom; and

(g) passing at least some heated Water from the heating tank into the reservoir of the at least one closed chamber during subsequent autoclaving cycles.

2. The process according to claim 1 wherein said heating tank is a pressure vessel and superheated water under pressure is passed from said reservoir to said heating tank to conserve heat in the vvater between cycles.

3. The process according to claim 1 with the additional step of passing superheated water from said reservoir to a second pressure vessel to conserve heat in the water between cycles.

References Cited UNITED STATES PATENTS 3,423,805 1/1969 Klingel 25133 US. Cl. X.R.