Screw Press Dewatering Control with Torque–Pressure Feedback
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Solution Overview
Problem
Existing methods for controlling the operation of devices for dewatering and compacting pressed materials, such as sludge and screenings, suffer from sluggish torque controllers that react too slowly to pressure surges, leading to unstable oscillations and potential damage, while pressure regulators react too quickly, causing oscillations and instability.
Innovation Solution
A method and device that control the speed of the screw shaft based on both torque and internal pressure using characteristic curves, allowing for fast and stable operation by adjusting the torque characteristic curve based on internal pressure and vice versa, thereby stabilizing the control system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque control is used to regulate screw shaft speed, then the control system is simple, but the response to pressure surges is too slow
Solution Approach 1:
The patent combines torque control and pressure control into a unified control system. The control unit receives both torque signals from the drive motor and pressure signals from the pressure sensor, then integrates them to regulate the screw shaft speed. This merging allows the system to benefit from both the simplicity of torque control and the responsiveness of pressure control without the full complexity of separate independent control systems.
Solution Approach 2:
The control unit acts as an intermediary that processes both torque and pressure signals. It uses the pressure signal to adjust the torque characteristic curve, effectively mediating between the simple torque control mechanism and the need for rapid pressure response. This intermediary approach allows fast response to pressure surges while maintaining the overall simplicity of torque-based control.
2Reliability
If pressure control is used to regulate screw shaft speed, then the response to pressure changes is fast, but oscillations and instability occur
Solution Approach 1:
The system implements feedback control by continuously monitoring both torque and pressure, then using this information to adjust the screw shaft speed. The control unit uses the pressure signal to modify the torque characteristic curve in real-time, creating a feedback loop that responds to pressure changes while dampening oscillations through the integrated control approach.
Solution Approach 2:
The patent changes the torque characteristic curve parameter dynamically based on pressure conditions. Instead of using a fixed torque characteristic, the control unit adjusts the curve according to the pressure signal, allowing the system to adapt its behavior to current operating conditions. This parameter change enables fast response to pressure changes while maintaining stability by preventing excessive oscillations.
3Reliability
If the torque characteristic curve is adjusted based on pressure, then the response to pressure surges improves, but the control system complexity increases
Solution Approach 1:
The system transitions from a static torque characteristic curve to a dynamic one that changes with pressure conditions. The control unit continuously adjusts the torque characteristic based on the pressure signal, allowing the system to adapt to varying operating conditions. This dynamic adjustment improves response speed to pressure surges while the control algorithm remains relatively simple by directly modifying the characteristic curve rather than implementing complex control logic.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method and device achieve stable and efficient dewatering and compaction of pressed materials by quickly responding to pressure changes, reducing oscillations, and ensuring consistent material properties, thus preventing damage and improving operational stability.
Implementation Method 1
A screw shaft (4) which can be set into rotation about a rotational axis (29) by a drive motor (5)
Implementation Method 2
The distance between adjacent helix sections can, particularly in the case of a screw press, decrease at least in sections in the conveying direction of the material to be pressed toward an outlet opening and/or an exit opening, thereby causing compression of the material to be pressed
Implementation Method 3
driving a screw shaft of the pressing arrangement at a speed with the aid of a drive motor
Implementation Method 4
detecting a torque introduced by the drive motor
Implementation Method 5
detecting a torque introduced by the drive motor and an internal pressure prevailing within the pressing arrangement
Data Source
Figure 1
AI summary
The invention relates to a method for operating a device (1) for dewatering and compacting material to be pressed (2), in particular sludge, screenings, or screened material, comprising the following steps: - introducing the material to be pressed (2) into a press assembly (3), - driving a screw shaft (4) of the press assembly (3) at a speed using a drive motor (5), - expelling any liquid (6) present in the material to be pressed (2) using the screw shaft (4), - detecting a torque applied by the drive motor (5) and an internal pressure prevailing within the press assembly (3), and - controlling the speed of the screw shaft (4) based on the torque along a torque characteristic curve (7a, 7b) and/or based on the internal pressure along a pressure characteristic curve (8). According to the invention, the torque characteristic curve (7a, 7b) is changed based on the internal pressure and/or the pressure characteristic curve (8) is changed based on the torque.Furthermore, the invention relates to a device (1) for dewatering and compacting pressed material (2).