Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28C—PREPARING CLAY; PRODUCING MIXTURES CONTAINING CLAY OR CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28C5/00—Apparatus or methods for producing mixtures of cement with other substances, e.g. slurries, mortars, porous or fibrous compositions
  • B28C5/08—Apparatus or methods for producing mixtures of cement with other substances, e.g. slurries, mortars, porous or fibrous compositions using driven mechanical means affecting the mixing
  • B28C5/0881—Apparatus or methods for producing mixtures of cement with other substances, e.g. slurries, mortars, porous or fibrous compositions using driven mechanical means affecting the mixing having a stator-rotor system with intermeshing teeth or cages
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/50—Mixing liquids with solids
  • B01F23/58—Mixing liquids with solids characterised by the nature of the liquid
  • B01F23/581—Mixing liquids with solids, slurries or sludge, for obtaining a diluted slurry
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
  • B01F25/50—Circulation mixers, e.g. wherein at least part of the mixture is discharged from and reintroduced into a receptacle
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
  • B01F27/05—Stirrers
  • B01F27/11—Stirrers characterised by the configuration of the stirrers
  • B01F27/115—Stirrers characterised by the configuration of the stirrers comprising discs or disc-like elements essentially perpendicular to the stirrer shaft axis
  • B01F27/1152—Stirrers characterised by the configuration of the stirrers comprising discs or disc-like elements essentially perpendicular to the stirrer shaft axis with separate elements other than discs fixed on the discs, e.g. vanes fixed on the discs

Definitions

• the present invention relates generally to the production of gypsum wallboard panels, and more specifically to operation of a gypsum slurry mixer used to produce the slurry forming the core of the wallboard panels.
• gypsum products i.e., products comprising calcium sulfate dihydrate
• starting materials comprising calcined gypsum (i.e., calcium sulfate hemihydrate) and water.
• calcined gypsum i.e., calcium sulfate hemihydrate
• water a popular application of gypsum chemistry is in the production of gypsum wallboard panels.
• the basic technology of gypsum wallboard panel manufacture is disclosed in U.S. Patent Nos. 1 ,500,452; 2,207,339 and 4,009,062 all of which are incorporated by reference.
• calcined gypsum is uniformly dispersed in water to form a slurry, and then the slurry is deposited upon a continuously moving web of facing paper located on a conveyor line. After deposit upon the face paper, a top layer of backing paper is deposited upon the slurry, which is then cast into a desired shape and allowed to set to form hardened gypsum by reaction of the calcined gypsum (calcium sulfate hemihydrite or anhydrite) with the water to form hydrated gypsum (calcium sulfate dihydrate). As is well known in the art, after the panels are formed, they are heated to dry the excess water, and cut into building panels.
• a mixer In the formation of the gypsum slurry, a mixer is typically used to mix the dry calcined gypsum, water and selected additives.
• Gypsum wallboard slurry mixers are well known in the art, and suitable examples are described in U.S. Patent Nos. 6,494,609; 6,059,444; and 3,459,620, all of which are incorporated by reference.
• a gypsum wallboard slurry mixer typically includes a housing defining a mixing chamber with inlets for receiving separate supplies of calcined gypsum and water, among the additives which are well known in the art.
• the mixer includes a rotating pin-laden disk, impeller or other type of agitator for agitating the contents to be mixed into a mixture or slurry.
• the discharge gate controls the flow of slurry from the mixer to the dispensing system.
• gypsum wallboard production lines usually have performance goals for the board as it is being formed, as well as of the resulting wallboard panels. These goals include, among other things, rapid setting time and reduced water demand to reduce kiln time and accompanying drying energy, reduced panel weight to facilitate installation, and panel strength for desired structural integrity of the resulting wall, often measured as Nail Pull. Nail Pull is the force in pounds needed to pull a panel over the head of a nail securing the panel to a framing stud of wood or metal.
• HRA Heat Resistant Accelerator
• HRA is a combination of low moisture landplaster and dextrose (sugar).
• HRA is typically mixed with other dry gypsum wallboard ingredients or additives prior to adding water to form the gypsum wallboard slurry.
• HRA has been found to enhance the development of crystals in the gypsum as the hydration process (hemihydrate to dihydrate) progresses, which causes the gypsum to set and harden, forming the wallboard core.
• HRA is known to enhance wallboard strength, to increase setting at the point where the set panels are cut to a desired panel length along the production line, and to complete hydration before the board is sent to a kiln for drying.
• HRA makes up about only 1% of the feed stock of dry wallboard ingredients, but enhances the performance of the resulting gypsum wallboard, in that less gypsum hemihydrate is needed to create the panels due to the enhanced crystal formation properties of HRA.
• the HRA is produced in a ball mill rotating at approximately 70 RPM before being placed in a feed hopper.
• Entoleter® comminuters or mills reduce the stucco particle size and increase the fraction of slurry particles in the 1 -10 microns size range.
• a representative description of an Entoleter® comminuter is found in US Patent No. 4,083,504 which is incorporated by reference.
• a production goal using these comminuters is producing at least 20-30% of the gypsum particles (by volume) to be in the range of 1 to 10 microns.
• conventional synthetic gypsum sources have a rather narrow size distribution of 40-50 microns and almost negligible number of particles smaller than that. In this way, the specific surface area (cm 2 / gram) of calcined gypsum is increased.
• Entoleter® comminuters are used to increase gypsum strength via Nail Pull (increases of 2-5 lbs) and have a slight impact on setting and hydration.
• HRA and Entoleter® comminuters carries significant and operational expenses.
• micro crystallizer is a dedicated mixer and mill for stucco and water agitation.
• the short residence time of stucco in the system did not allow for any dihydrate formation, and was essentially just a highly agitated mixed hemihydrate slurry pumped into the main mixer.
• This technology basically required the operation and maintenance of two mixers and was phased out and replaced by other dihydrate-based systems and HRA.
• a modification of the existing mixer includes the use of an existing extractor conventionally used to divert a portion of the slurry for creating a relatively higher density layer adjacent the face paper, and a hose or conduit connected to the extractor and directed back into the mixer to redirect the diverted slurry portion back into a main mixing chamber for additional mixing.
• water or other additives are contemplated as being added to the diverted slurry portion.
• the main objective of the present process is to “double mix” a selected portion of the slurry and increase the percentage of fine particles in the total of particles forming the slurry.
• up to 20% of the volume of slurry in the mixer is diverted for remixing. In another embodiment, approximately 5-7% of the volume of the slurry in the mixer is diverted for remixing.
• the diverted flow of slurry is reintroduced into the existing mixer vent.
• the approximate residence time in the mixer for the recycled, reintroduced slurry is in the range of 2-3 seconds.
• a process for creating a gypsum wallboard slurry with enhanced strength.
• the process includes providing a gypsum wallboard slurry mixer, providing suitable amounts of calcined gypsum and water in the mixer to create a slurry, agitating the slurry in the mixer, extracting a portion of the slurry in the mixer, reintroducing the extracted portion into the mixer for further mixing, and dispensing the mixed slurry from an outlet of the mixer.
• the mixer further includes at least one extractor, and the extracted portion of the slurry is dispensed in a conduit connected to the extractor into a port for reintroduction into the mixer.
• up to 20 % of a volume of the slurry in the mixer is diverted and reintroduced for further mixing.
• approximately 5-7% of the slurry volume is reintroduced into the mixer for supplemental mixing.
• the reintroduced slurry resides in the mixer for 2-3 seconds. It is also contemplated that the mixer is provided with upper and lower extractors, and the extracted portion of the slurry is dispensed in a conduit connected to the upper extractor and reintroduced into a port in the mixer.
• a process for creating a gypsum wallboard slurry with enhanced strength including providing a gypsum wallboard slurry mixer, providing suitable amounts of calcined gypsum and water in the mixer to create a slurry, agitating the slurry in the mixer, extracting up to 20% of the volume of slurry in the mixer, reintroducing the extracted portion into the mixer for further mixing for 2-3 seconds, and dispensing the mixed slurry from an outlet of the mixer.
• FIG. 1 is a top plan view of a gypsum mixer configured for performing the present process
• FIG. 3 is a top perspective view of the mixer agitator used in the mixer of
• FIG. 1. DETAILED DESCRIPTION
• the inlets 20, 22 are connected to corresponding supplies of calcined gypsum and water that deliver constituents to the mixer 10 by gravity feed.
• additives including but are not limited to accelerators, foam, retarders, fillers, binders and the like.
• the additives are supplied through the inlets 20, 22 or through supplemental designated inlets.
• the ring 34 is often referred to as a “lid ring”, and enhances mixing action in the mixer 10 by preventing larger agglomerations or lumps of calcined gypsum from exiting an interior chamber 38 of the mixer before becoming more finely divided and dispersed in the slurry.
• the agitator 24 is located within the chamber 38. Under normal operation, a supply of calcined gypsum is provided into the inlet 20, and a supply of water is provided into the inlet 22. The water and gypsum are mixed together in the mixing chamber 38 to form a slurry due to the rotation of the agitator 24.
• conduit 50 is optionally oriented to dispense the slurry into the gypsum inlet 20. Regardless of the location of the particular inlet port, the supplemental conduit 50 dispenses a selected portion of gypsum slurry back into the mixing chamber 38 for additional or further mixing, which reduces the average particle size of the re-mixed portion.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Dispersion Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Structural Engineering (AREA)
• Preparation Of Clay, And Manufacture Of Mixtures Containing Clay Or Cement (AREA)

Applications Claiming Priority (3)

Publications (1)

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Family Applications (1)

Country Status (5)

Family Cites Families (9)

• 2023
  • 2023-05-25 EP EP23734094.8A patent/EP4532159A1/de active Pending
  • 2023-05-25 WO PCT/US2023/023569 patent/WO2023244426A1/en not_active Ceased
  • 2023-05-25 IL IL316977A patent/IL316977A/en unknown
  • 2023-05-25 CA CA3258249A patent/CA3258249A1/en active Pending
• 2024
  • 2024-11-26 MX MX2024014604A patent/MX2024014604A/es unknown

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