Swinging agitator for a gypsum calcining apparatus and the like

An agitation mechanism for a gypsum processing apparatus which includes a housing having a bottom wall, and at least one side wall. The housing can be constructed and arranged to receive and process gypsum-based products. An agitator frame having a similarly shaped cross-section to the cross-section of the housing is provided and positioned adjacent the bottom wall of the housing. The agitator frame is pivotally connected internally to the housing for reciprocating movement between first and second positions. The agitation mechanism is operable for preventing fluid channeling to ensure good fluidization of the gypsum products from collecting adjacent the bottom wall of the housing.

The present invention relates to a method and apparatus for agitating gypsum product.

BACKGROUND OF THE INVENTION

Calcining of gypsum comprises converting calcium sulfate dihydrate by heating into calcium sulfate hemihydrate, better known as stucco. Prior calcining apparatus and methods have taken various forms. Traditionally, the calcining of gypsum has occurred in a large kettle, having a thickened dome-shaped bottom, against which a gas-fired flame is directed, with the kettle and burner flame being enclosed in a suitable refractory structure. There is usually an associated hot pit into which the calcined material is fed. The kettle must withstand temperatures in the 2,000°–2,400° F. range, hence requiring expensive fire box steel plate on its domed bottom, which was typically 1¾ inches thick. U.S. Pat. No. 3,236,509 typifies this type construction. This approach had numerous disadvantages, such as the extreme waste of hot burner gases, and the associated refractory brick enclosure which, when repairs or kettle shut-down were needed, first required a lengthy cool-down period.

After the gypsum has been calcined, further processing is sometimes required. The calcined gypsum, or stucco, can be placed in a fluid bed stucco cooling apparatus wherein water is sprayed into the apparatus to cool the stucco to a predetermined temperature. In addition, other types of stucco processing apparatus are known such as a cooling coil fluid bed stucco treaters where the stucco is cooled with a cooling coil that is positioned within the apparatus to control the temperature of the stucco. Other processing apparatus such as post-stucco treatment retention devices can be used in the manufacture of gypsum-based products.

SUMMARY OF THE INVENTION

The present invention provides for an agitation mechanism for a gypsum processing apparatus which includes a housing having a bottom wall, and at least one side wall. The housing can be constructed and arranged to receive and process gypsum-based products. A fluidization mechanism can be provided for delivering fluid to the gypsum-based products. An agitator frame having a similarly shaped cross-section to the cross-section of the housing is provided and positioned adjacent the bottom wall of the housing. The agitator frame is pivotally connected internally to the housing for reciprocating movement between first and second positions. The agitation mechanism is operable for preventing channeling of the fluid through the gypsum, ensuring good fluidization, and preventing gypsum product from collecting adjacent the bottom wall of the housing. The agitation mechanism can include a plurality of agitation members connected to the frame for agitating the gypsum product adjacent the bottom wall when the agitator frame moves. The agitation mechanism can also include at least one pivotal support arm for pivotally connecting the frame to the apparatus.

The agitation mechanism can be used in a fluidized stucco cooler utilizing water injection. The agitation mechanism can be used in a fluidized bed stucco cooler utilizing cooling coils. Further, the agitation mechanism can also be used in a post-stucco treatment retention device.

A method is provided for agitating gypsum based material in a processing housing. The gypsum based material is delivered to the housing, and an agitation mechanism having a frame with agitation members attached thereto is positioned adjacent the bottom wall of the housing. The agitation mechanism is moved between first and second positions to agitate the fluidized material in the housing to prevent material from coagulating near the bottom of the housing and to prevent fluid channeling and dead zones of non fluidized gypsum.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 1, an apparatus10for calcining gypsum is shown therein. A housing12includes a bottom wall14, an open top16, and a plurality of side walls18extending between the bottom wall14and the open top16. An inlet fixture20is located on the housing12for receiving crushed or synthetic raw gypsum from a source (not shown) and for transferring the gypsum into the housing12. At least one burner22is connected to the housing12. The burner22is operable for combusting an air-fuel mixture supplied by a forced air conduit24and a fuel conduit26. The burner22can be any type known to those skilled in the art, but will typically burn a hydrocarbon based fuel. The heated exhaust from the burner22will flow through at least one serpentine shaped burner conduit28that extends through a gypsum support floor23adjacent the bottom wall14of the housing12. The hot exhaust flow from the burner22is utilized to heat the gypsum material to approximately 300° F. In known manner, the heating process converts the gypsum into calcium sulfate hemihydrate, or stucco. Alternatively, the heating process can simply heat wet synthetic gypsum to a desired temperature, typically below 300° F. in order to dry excess moisture from the wet synthetic gypsum for subsequent calcination in a separate process. Alternatively, the heating process can perform the drying and calcination processes in the same vessel.

The burner conduit28advantageously includes an elongate linear portion30extending away from the burner22. The linear portion increases the life span of the burner conduit28. That is, if the flames from the burner22were to directly impinge the burner conduit28along a curved or angled portion, the flames would overheat the side wall of the conduit causing high stress which shortens the life of the conduit28. However, due to the presence of the initial elongated linear burner section30(which can extend some fifteen to twenty feet in a commercial installation), the burner flames do not directly impinge on the burner conduit, and this is because the flames have converted, along the length of section30, to hot exhaust gases. Importantly, the burner conduit28includes a plurality of curved sections32to connect the linear portions30,31, and33, provide the serpentine shape. The burner conduit28may include at least one reduced diameter section34to provide increased exhaust flow velocity to thereby enhance the heat transfer effectiveness of the conduit28. The temperature of the exhaust cools proportionally to the distance it moves away from the burner22, therefore the velocity may be increased to maintain a suitable heat transfer rate. The burner conduit28can also include a multi-conduit portion36wherein a plurality of relatively smaller diameter conduits38are formed to be in fluid communication with relatively larger single conduit portions32. The smaller diameter conduits38provide more surface area for a given effective flow area and thus increase the heat transfer relative to the larger conduit32. The multi-conduit portions36can be connected to the single conduit portions32through various means known to those skilled in the art such as welding, brazing, and press fit, mechanical fasteners, etc. The burner conduit28can be attached to the burner22via a flange40with a plurality of threaded fasteners42. The burner conduit28likewise can be attached at the discharge end44to an outlet conduit46that extends through the support floor23. The burner conduit28can be attached to the outlet conduit46via a flange48with a plurality of threaded fasteners50.

A fluidization base52, shown inFIGS. 1,2,4and6, (best seen inFIG. 2) can be positioned in a lower portion of the housing12to receive exhaust flow from the burner conduit28. The fluidization base52has a plurality of sidewalls53extending upwardly from a bottom55. The fluidization base52can have a fluidization pad54positioned above the bottom55of the fluidization base52. The fluidization pad54forms at least a portion of the support floor23of the housing12. The fluidization pad54is operable for containing the gypsum product along the lower portions of housing12, and for evenly distributing the exhaust flow as it passes from the fluidization base52directly into the gypsum. The fluidization base52delivers the aeration, the agitation ensures good fluidization especially of cohesive powders that will not otherwise fluidize. The fluidization pad54includes first and second outer perforated plates56,58. The plates56,58include a plurality of through apertures57that permit the exhaust flow to pass therethrough. A bore hole59is formed in the fluidization pad54to provide access for the conduit46(seeFIG. 1) to pass through and deliver the exhaust flow to the fluidization base52. At least one intermediate porous layer60, formed of a porous fiber mat or woven stainless steel media, is positioned between the outer plates56,58. The intermediate layer60of media can be made from compressed silica fiber, woven stainless steel mesh or similar materials suitable for fluidization as known to those skilled in the art to withstand high exhaust gas temperatures. The perforated plates56,58are most preferably made from a metal such as stainless steel or the like. The fluidization pad54operates by allowing diffused exhaust gas to bubble out through the generally evenly spaced apertures57of perforated plate56. One advantage to using woven stainless steel media60is that the perforated plates56,58are not required except to provide support and protection for the media from punctures.

An agitation mechanism62, shown inFIGS. 1,3,4,6,7,8, and9(best seen inFIG. 3), can be positioned just above the fluidization pad54. The agitation mechanism62includes an agitator frame64having a pair of side beams65. The agitator frame64has a plurality of agitation members66connected to the agitator frame64for agitating the gypsum product adjacent the fluidization pad54along the support floor23. In one embodiment, the agitation members66can take the form of a cross bar pattern. The agitation mechanism62locally churns the heated gypsum product when the agitator frame64is set into motion. At least one pivotal support arm68pivotally connects the agitation frame64to the housing12(shown inFIG. 1). The connection to the housing12can be formed with an angle plate70affixed to the housing12in a suitable manner such as by welding or mechanically fastening, etc. The support arm68can be secured to the angle plate70via a threaded fastener72or the like. The pivotal support arm68is most preferably a cable or similar structure to more easily facilitate a swinging motion by the agitator frame64about a common pivot axis when motion is imparted to the agitator frame64. Alternate moving patterns by the agitator frame64are contemplated by the present invention. For example, one skilled in the art would readily understand how to impart motion to the agitator frame64in a vertical, horizontal, or arcute pattern, or any combination thereof.

An actuation power source, such as an electric motor or pneumatic air cylinder74, can be connected to the agitator frame64through an actuator arm76. An expandable seal78is engaged with the actuator arm76and the housing12(not shown inFIG. 2) to prevent gypsum product from leaking out of the housing12about the actuator arm. The seal78expands and contracts as the actuator arm76moves between first and second positions as the agitator frame64swings. Alternatively, the actuator arm76can be connected to mechanically leveraged linkages (not shown) that can extend from an actuation power source (not shown) positioned at the top of the housing12down to the agitator frame64as is known to those skilled in the art. The seal78can be made from any suitable material that can withstand temperatures greater than 300 degrees Fahrenheit and pressures up to 10 psig (pounds per square inch gage).

Referring again toFIG. 1, an overflow tube80is fluidically connected to the housing12to allow processed gypsum to egress from the housing12into the overflow tube80. An overflow valve82is associated with the overflow tube80to prevent gypsum from egressing from the housing12prior to being heated to a predetermined condition. A dump port84includes a dump valve86that permits the selective draining of the contents in the housing12. The valves82,86can be of any type known to those skilled in the art, but are most preferably electrically or pneumatically actuated.

Referring now toFIG. 4, a conduit support88is slidingly connected to the housing12for supporting the burner conduit28during installation. The support88is operable for sliding between an outer position at least partially external to the housing12(shown inFIG. 4) and the installed position inside the housing12. The conduit support88holds the conduit during installation and removal from the housing12. The support88includes a pair of side rails90,92slidingly connected to slide elements91formed on parallel walls18of the housing12. A plurality of cross-bars94extend between the side rails90,92to provide support surfaces for the burner conduit28to rest thereon. The housing12includes a side panel96operable to open when installing the burner conduit28. A plurality of ties97structurally connects the side walls18of the housing12to one another to prevent outward bowing of the walls18when the housing12is filled with gypsum. The ties97can be welded or otherwise affixed by any means that is conventional.

Referring now toFIG. 5, the apparatus10includes access panels98located on the side of the housing12for permitting servicing of the internal components, such as the burner22and the conduit28, etc. A disengagement chamber100is positioned above the open top16of the housing12and is constructed to permit access thereto for servicing internal components of the housing12. A dust collector102can be positioned above the disengagement chamber100to collect gypsum dust particles and recycle the particles back into the housing12for calcining. The dust collector102can include a plurality of replaceable filters104. The filters104can be of any desired type such as round cartridge filters, bag filters, or the like. The filters104can be periodically cleaned by intermittently injecting air through an opposite side of where the dust is collected or by shaking as is known to those skilled in the art. An exhaust stack106permits the exhaust to be removed from the apparatus10after the gypsum dust particles have been removed by the filters104.

In operation, gypsum powder is fed into an inlet fixture20to fill the housing12. Air and fuel are supplied by the conduits24,26respectively, to the burner22. The burner22combusts the air-fuel mixture and provides hot exhaust gases which flow in the direction of the arrows shown inFIG. 6. The exhaust flows through the serpentine burner conduit28into the fluidization base52. From the fluidization base52, the exhaust flows horizontally and then upwardly through the fluidization pad54positioned above the base52. The fluidization pad54distributes the exhaust gases through the gypsum product so that the heated exhaust gases are evenly distributed therethrough. The outer surface of the burner conduit28provides heat to the gypsum through conduction heat transfer. Thus, the gypsum product is heated both when the exhaust gas flows through the burner conduit28and through the gypsum after traveling through the fluidization pad54. The present invention provides for increased fuel efficiency over the prior art because the dual heating method removes the maximum amount of heat from the exhaust and transfers it into the gypsum. Exhaust gas continues to flow upwardly through the disengagement chamber100permitting some of the gypsum particles to separate from the exhaust flow and fall back into the housing12. The dust collector102cleans the airborne gypsum particles from the exhaust gas before exhaust gas egresses through the exhaust stack106. The gypsum particles can periodically be knocked from the collector filter cartridges (or bags) back into the bed of gypsum.

Advantageously, an agitation mechanism62is provided to ensure good fluidization by preventing exhaust from channeling directly through gypsum powder. Natural gypsum typically includes a fine powder that may be too cohesive to achieve good fluidization without agitation. The agitation mechanism62is operated by swinging between first and second positions to locally mix the gypsum and scrape it away from the fluidized pad54. The calcining apparatus10has a high efficiency because substantially all of the heat produced by the burner22is utilized in heating the gypsum and is not lost through the exhaust process. The temperature of the exhaust gas leaving the gypsum product is approximately 300° F., which is the approximate temperature required for the gypsum to be processed into stucco. Synthetic gypsum that is manufactured with a standard particle size may not require agitation to ensure good fluidization.

Referring now toFIG. 7, a water spray fluid bed stucco treater110for cooling stucco is shown therein. Hot stucco can enter the water spray treater110through an inlet118. Cooled stucco and fluidization gas can exit through an outlet119. The water spray stucco treater110includes an agitation mechanism62having an agitator frame64. The agitation mechanism62includes an agitator frame64having a pair of side beams65. The agitator frame64has a plurality of agitation members66, in the form of cross bar pattern, connected to the frame64for agitating the gypsum product adjacent the support base23. The agitation mechanism62locally chums the gypsum product when the frame64is set into motion. At least one pivotal support arm68pivotally connects the agitation frame64to the stucco treater apparatus110. The connections to the apparatus110can be formed with an angle plate70affixed to the housing in a suitable manner such as by welding or mechanically fastening, etc. The support arm68can be secured to the angle plate70via a threaded fastener72or the like. The pivotal support arm68is most preferably a cable or similar structure to more easily facilitate a swinging motion by the frame64about a common pivot axis when motion is imparted to the agitator frame64. A power source, such as an electric motor74, can be connected to the agitator frame64through an actuator arm76. The electric motor74can be utilized to swing the agitation mechanism62about a pivot axis, to agitate the stucco and prevent channeling of the fluidization gases, dead zones, and build-up any where in the fluidized bed, especially along the bottom portion of the apparatus110. A blower (not shown) injects fluid, such as air, or the like through an inlet116formed on the stucco treater110to create a fluidized bed of stucco to prevent the stucco from hardening and coagulating adjacent the fluidization pad54of the water spray cooler apparatus110. The apparatus110can also include a fluidization base52as described above. The water spray cooler110includes a water manifold112for delivering water to a plurality of spray nozzles114. The spray nozzles114are operable for spraying water into the apparatus110and thus cooling the stucco to a predetermined temperature.

Referring now toFIG. 8, a cooling coil fluid bed stucco cooler120is shown therein. Hot stucco can enter the cooling coil stucco cooler120through an inlet118. Cooled stucco and fluidization gas can exit through an outlet119. The cooling coil stucco cooler120includes an agitation mechanism62having an agitator frame64. The agitation mechanism62includes an agitator frame64having a pair of side beams65. The agitator frame64has a plurality of agitation members66connected to the frame64for agitating the gypsum product adjacent the support base23. The agitation mechanism62locally chums the gypsum product when the frame64is set into motion. At least one pivotal support arm68pivotally connects the agitation frame64to the cooling coil stucco cooler120. The connections to the apparatus120can be formed with an angle plate70affixed to the housing in a suitable manner such as by welding or mechanically fastening, etc. The support arm68can be secured to the angle plate70via a threaded fastener72or the like. The pivotal support arm68is most preferably a cable or similar structure to more easily facilitate a swinging motion by the frame64about a common pivot axis when motion is imparted to the frame64. A power source, such as an electric motor74, can be connected to the frame64through an actuator arm76. The electric motor74can be utilized to swing the agitation mechanism62about a pivot axis, to agitate the stucco and prevent build-up along the bottom portion of the apparatus120. A blower (not shown) injects fluid, such as air, through an inlet128formed on the cooling coil stucco cooler120to create a fluidized bed of stucco and the agitation mechanism62prevents the stucco from coagulating adjacent the fluidization pad54of the cooling coil stucco cooler120. The apparatus110can also include a fluidization base52as described above. The cooling coil stucco cooler120includes a serpentine-like cooling coil122designed to transport a suitable cooling fluid such as ethylene glycol, chilled water, or the like through the stucco. The cooling coil122includes a coolant inlet124in which the coolant enters from a supply source (not shown). The coolant follows the serpentine coil122and exits from a coolant outlet126. The coolant traverses the cooling coil122to cool the stucco to a predetermined temperature.

Referring now toFIG. 9, a post stucco treatment retention device130is shown therein. Stucco can enter the post stucco treatment retention device130through an inlet118. Stucco and fluidization gas can exit through an outlet119. The post stucco treatment retention device130includes an agitation mechanism62having an agitator frame64encompassing a plurality of agitation members66. The agitation members66are connected to the frame64and are operable for agitating the gypsum product adjacent the support base23. The agitation mechanism62locally chums the gypsum product when the frame64is set into motion. At least one pivotal support arm68pivotally connects the agitation frame64to the stucco retention apparatus130. The connections to the apparatus130can be formed with an angle plate70affixed to the housing in a suitable manner such as by welding or mechanically fastening, etc. The support arm68can be secured to the angle plate70via a threaded fastener72or the like. The pivotal support arm68is most preferably a cable or similar structure to more easily facilitate a swinging motion by the frame64about a pivot axis when motion is imparted to the frame64. A power source, such as an electric motor74, can be connected to the frame64through an actuator arm76. The electric motor74can be utilized to swing the agitation mechanism62about a pivot axis, to agitate the stucco and prevent build-up along the bottom portion of the apparatus130. In the illustrative embodiment, the post stucco treatment retention device130is shown as having a round cross section, however, various cross sectional geometries can be used with the agitation mechanism62. The post stucco treatment retention device130typically will include a blower (not shown) to provide fluid, such as pressurized air, through an inlet132formed on the retention device130.