DE4220163A1 - Monitoring, regulating and controlling drying of non-metallic inorganic material - in which electrical conductivity measured in used as signal which triggers heat for drying - Google Patents

Abstract

A process to monitor, regulate and control the drying progress of a non-metallic inorganic material uses the electrical conductivity of the substance. The electrical conductivity so measured is used as a signal which triggers the introduction of more moisture, as required. USE/ADVANTAGE - The process controls the moisture content and drying progress of ceramic clays or plaster. Control of the drying process optimises the finished prod..

Description

In a clay-ceramic processing plant, the ACTUAL humidity of a pre-shredded mass flow on a conveyor belt electrical conductivity determined to ensure the material moisture to the required To be able to bring target value. For this purpose, the mass flow between baffles and one The pressure roller is compressed to such an extent that the relative instantaneous pressure is sufficiently accurate electrical conductivity of the mass flow between the baffles measured continuously can be. According to the size of the deviation of the ACTUAL value from the TARGET value the moisture metering device provides electrical impulses for opening or closing solenoid valves or throttle valves.

On a clay-ceramic mass strand, which with constant mass composition Extrusion is generated, the electrical conductivity of the pressed material between  Mouthpiece and a contact or marking roller measured. With an optimal Press moisture of 20.8% abs. and constant driving style, the electrical conductivity fluctuates in the measuring arrangement between the mouthpiece opening and the contact roller between 3.27 and 3.29 mS. The electrical conductivity increases with higher press moisture, with lower one Press moisture drops below the TARGET value. The conductivity meter that comes with a Limit detector is equipped, signals when the electrical conductivity drops below 3.26 or rises above 3.30 mS. Electrical impulses are sent to the actuator or a downstream regulation to the water metering device in order to increase or decrease the Water added, which is located directly in front of the screw press. The size of the Pulses can be proportional to the deviation from the target value.

In a drying plant for cast gypsum blocks, the drying end of the gypsum blocks is said to be be determined in order to be able to stop the heat supply in good time. The gypsum blocks are located during drying on 2 metallic slatted pads. These requirements are overall electrically insulated from the housing of the drying system, but have separate ones electrical contacts for measuring electrical conductivity.

The drying process should take place until the measured electrical conductivity to the Gypsum blocks goes to zero, then the drying system switches off automatically. The The limit indicator of the conductivity meter delivers the switching impulse.

The end of the first drying section is said to be in a drying plant for perforated brick the moldings are found to automatically dry the drying chambers from this point on to be able to apply a higher amount of heat or to circulating devices adjust. In addition, the end of drying should be detected so that after it has been reached Heat supply stops automatically and the drying chamber in question is switched off. The electrical conductivity is measured simultaneously on 10 moldings, which are based on a selected pair of light metal slats are located in the drying chamber concerned. The electrical contact between the two slats, which are parallel to each other in a 15 cm Distance, and the moldings are created by the contact. The slats themselves are on specially insulated contact plates that are electrically connected to the Conductivity meter are connected. Because the contact plates are permanently installed in the drying chamber are and the loading of the drying chamber takes place systematically, with everyone Drying process the measuring and control process repeated.

For the drying process, the following empirically determined dependency on drying time is Shrinkage and electrical conductivity known:

The end of the first drying section in the measuring arrangement mentioned is at electrical conductivity of 0.3 mS. The conductivity meter that with a Limit detector equipped for 0.3 mS gives when this value is reached and after a Delay time of 15 minutes an electrical pulse to the actuator for automatic Increase in heat exposure.

A second limit detector, which is set to a conductivity value of 0.05 mS, reports after a delay of 15 minutes the end of drying by another electrical signal to the mechanical and electrical actuators that the automatic Switch off the drying chamber.

Legend for illustration

MV loss of mass (% humidity)
TS dry shrinkage (% linear)
EL electrical conductivity (mS)
mS Millisiemens

Claims (6)

1. A method for determining and controlling / regulating current material moisture and drying processes on non-metallic inorganic raw materials based on the measurement of the electrical conductivity, characterized in that for moisture control of such materials in processing or processing these with electrical contacts so in Be brought into contact with the fact that the measured values for the respective instantaneous electrical conductivity of the measured material at the measurement location provide the necessary electrical signals for controlling / regulating a moisture metering and / or an energy or air metering in drying systems. 2. The method according to claim 1, characterized in that for controlling / regulating the Material moisture the tap of the measured values for the current electrical conductivity of the test material during an intermediate compression of the material flow, e.g. B. on one Conveyor belt using baffles and pressure rollers, and the resulting or generated necessary signals used for an upstream or downstream moisture metering will. 3. The method according to claim 1, characterized in that for controlling / regulating the Material moisture the tap of the measured values for the instantaneous electrical conductivity immediately after deformation, e.g. B. on a strand of material or on moldings, by contactor e.g. B. in the form of contact plates or rollers, which touching the flow of material metallic parts of the technical units as one of the two necessary contactors can be used and the signals obtained and necessary for a Deformation unit upstream moisture metering can be used. 4. The method according to claim 1, characterized in that to control a Drying process or to determine the drying progress and to control the Energy supply into the drying chamber or system concerned individual drying objects or the partial or all of the stocking of a drying chamber or plant based on that with the Moisture-decreasing electrical conductivity can be monitored and when reached of measured values of the electrical conductivity characteristic of the drying progress Provides signals through which automatic or manual control / regulation of the energy and / or air exposure to the drying unit in question can be triggered. 5. The method according to claims 1 and 4, characterized in that it is in the electrical contacts for measuring the current electrical conductivity around spatial and Electrically separated and electrically isolated editions of the Items to be dried or special electrodes are used, the carrier system of the Items that can be dried do not allow undesired cross currents. 6. The method according to claims 1 to 5, characterized in that for the measurement used conductivity meter electronic limit detectors and controllers as well Transducers or, if necessary, electronic time modules can be connected can deliver the impulses necessary for a control / regulation for the actuators.