Abstract: A porous paste, especially a plaster paste or slurry for producing sandwich-type plasterboard, is made in a disk-shaped mixer having a rotor rotatable in a mixing chamber by introducing compressed air or other pressurizable gas through a wall or bottom segment directly into the chamber so that the incoming pressurized gas meets the mixture with a shearing action along the wall or bottom.

Abstract: A porous paste, especially a plaster paste or slurry for producing sandwich-type plasterboard, is made in a disk-shaped mixer having a rotor rotatable in a mixing chamber by introducing compressed air or other pressurizable gas through a wall or bottom segment directly into the chamber so that the incoming pressurized gas meets the mixture with a shearing action along the wall or bottom.

Abstract: A porous paste, especially a plaster paste or slurry for producing sandwich-type plasterboard, is made in a disk-shaped mixer having a rotor rotatable in a mixing chamber by introducing compressed air or other pressurizable gas through a wall or bottom segment directly into the chamber so that the incoming pressurized gas meets the mixture with a shearing action along the wall or bottom.

Abstract: Fore many applications it is desirable to determine the operating level, i.e. the current flow rate V and the total pressure difference &Dgr;pt of a fan in the installed state without external measuring points and calibration. The invention should develop a suitable method and a corresponding fan. In the method of the invention, from a measured effective pressure difference &Dgr;pMw a flow rate V is determined and from that, via an operational characteristic curve a target value for the total pressure difference &Dgr;pst is found. By comparing the target value &Dgr;pst determined this way with its measured value &Dgr;pMt the operating level and its accuracy are determined. For this purpose on the fan of the invention measuring points are provided for measuring one or more effective pressure differences &Dgr;pMw and the total pressure difference &Dgr;pMt.

Abstract: Directly heated rotary drums are used in the drying of pourable goods such as wood chips or strands. Drums are provided with built-in fixtures such as cross fixtures, in order to ensure good heat transmission from the drying gas to the goods. The invention comprises a design for a rotary drum (4) which enables good transmission of drying gas to the goods and which is cheap to produce and assemble in comparison with cross fixtures. According to the invention the built-in fixtures in the rotary drum (4) extend radially in the direction of the middle of the drum, starting from the perimeter, over an area of 60 to 85% of the radius of the rotary drum (4), form at least two pockets, and run, apart from the area close to the perimeter, substantially in the direction of rotation (25), in front of the radial starting from their point of attachment. These radially shaped built-in fixtures enable constant distribution of the goods over the cross-section and are substantially cheaper to manufacture and assemble.

Abstract: A drying apparatus has a housing, a conveyor for displacing a flat workpiece horizontally in a travel direction through the housing on a level, and a horizontal array of horizontally elongated upper nozzle boxes lying generally in a plane above the level. Each box is formed with a plurality of downwardly directed nozzle holes and heated air is fed to the boxes so it is projected from the holes against the workpiece for drying same. Respective upper shield plates each formed with a plurality of apertures are slidable on the respective boxes between a position with the apertures aligned with at least some of the respective holes and a position with the apertures out of line with the respective holes. At least one pivotal rod extending along a rod axis in the direction has radially projecting arms each engaged with a respective one of the respective shield plates. The rod can be pivoted about the rod axis to shift all the shield plates between their positions.

Abstract: A drier for broad articles such as plasterboard has a conveyor in entraining the plasterboard along a drying path in a transport plane and the nozzle boxes for contacting the plasterboard with the drying air have their orifice surfaces inclined to the plasterboard to achieve uniformity of drying in terms of residual moisture content.

Abstract: In order to dry boards, the boards are guided on racks through a drier and brought into contact with drying air in two stages. In a stage A with a higher drying power, the drying air is supplied at a higher temperature and with an at least average humidity, and in the other stage B, it is supplied at an average temperature and with a low humidity. The waste heat of the outgoing air from stage A is used for preheating the drying air. This process should reduce the consumption of primary energy. For that purpose, a process is known that consists of also using the outgoing air condensation heat. This has the inconvenience, however, of requiring substantially more secondary energy, as important air mass flows are required to transfer heat because of the low condensation temperature. Primary energy should be reduced by using condensation heat without substantially increasing secondary energy requirements.

Abstract: In the process for making gypsum fiberboard the boards are formed or molded rom a mash containing calcium sulfate dihydrate and fiberous material. By heating and subsequently cooling the boards the dihydrate is first converted into the hemihydrate and subsequently recrystallized again to the dihydrate. Known processes require day line setting times which are economically disadvantageous. According to the present invention these times are shortened by pulling or drawing water, an aqueous solution or a water containing mixture through the boards after the cooling step. Advantageously a setting accelerating agent can be dissolved in the water. By these features the setting time can be shortened to less than two hours. By addition of a binding agent, e.g. starch, to the fluid drawn through the boards the strength of the boards is increased.

Abstract: A method of and apparatus for producing gypsum fiber boards includes introducing shaped boards provided of a mash of calcium sulphate dihydrate and fibrous material and possibly additives after dewatering and shaping the mash into at least one pressure vessel and to heat the boards at saturated steam atmosphere to 120.degree.-160.degree. C. over a predetermined period. Thereafter, the boards are allowed to cool down within the pressure vessel to a temperature of about 100.degree. or less before being discharged therefrom.

Abstract: A continuous drier for plywood sheets is provided at its inlet end with a nsing device measuring the width and the spacing of the plywood sheets entering the drier. The values measured by the sensing device are transmitted to a control device, which by means of a calculator regulates the speed of a conveyor transporting the plywood sheets through consecutive sections of the drier in such a manner that the plywood sheets follow each other closely on the conveyor without overlapping. Each of the sections is provided with a heater and a ventilator which blows air over the heater, and the hot air is directed by installations onto the plywood sheets. In order to compensate the effect of the varying speed of the conveyor with respect to the drying of the plywood sheets, the control device preferably controls also the volume of the streams of hot air by varying the speed of the ventilators. This will result in a considerable saving of the driving energy.

Abstract: Enthalpy quantities such as the degree of moisture of gases, the wetness of steam or the enthalpy of dry steam are measured by passing a specific amount or dosage of a gas or steam through a system such as a cooler or dryer wherein its thermal condition is changed while measuring the inlet and outlet temperature, and measuring heat radiated into the condition changing system whereupon the desired enthalpy quantity is obtained from a heat balance equation set up from the measured and known data.

Abstract: A thermal measurement of mass flow is obtained by passing a flowing mass through a hollow passageway, measuring the temperature of the mass at the inlet and at the outlet of said passageway and additionally measuring the heat flow released or absorbed through the walls of the passageway and then determining the mass flow by setting up the heat balance equation on the basis of the obtained data. Preferably, the data are fed into a computer to solve the resulting heat balance equation. The invention also comprises an apparatus wherein temperature sensors are arranged at both ends of a tubular passageway and wherein the heat flow meter comprises concentric wire coils of a thermic resistance material wound around the outer periphery of the tube and an interposed layer of predetermined thickness formed of a material of at most moderate heat conductivity.

Abstract: Wet plasterboard to be dried is advanced along a path. At an upstream portion of the path, air is heated and directed towards the plasterboard for initial drying of the latter. A portion of the heated air is withdrawn and passed through one section of a heat exchanger whose other section contains water which exchanges heat with the heated air. The heated water is passed through a section of another heat exchanger whose other section contains fresh air which is heated by the heated water. The heated fresh air is directed towards the articles for further drying of the latter at a downstream portion of the path. A portion of the heated fresh air is exhausted and recirculated at the downstream path portion.

Abstract: Plyboard or the like passes through the successive drying zones of a multone drier, has a varying initial moisture content and presents to the drier a fluctuating degree of loading (surface area). The drying action is varied by adjusting the drying-gas temperature and/or the transport speed of the goods through the drier, so as to quickly match the drying action to the fluctuating drying demand. Instead of measuring initial moisture content per se and degree of loading (surface area) per se, temperature measurements are performed, from which equivalent information is derived, and from which in turn are calculated the values of drying-gas temperature and/or transport speed which must be set on the temperature and speed controllers of the drier.