Coal Mill Control Device for Output Pattern Deviation
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Solution Overview
Problem
The variability in coal properties such as Hardgrove grindability index (HGI) and moisture percentage affects the grindability and transportability in coal pulverizers, leading to delays in coal output and instability in steam temperature or steam pressure control in boilers, making real-time control challenging.
Innovation Solution
A control device for coal pulverizers that estimates coal output by calculating a correction signal based on the deviation between a standard coal output pattern and the current output pattern, using detection data from the pulverizer, boiler, and power generator, and adjusts the coal feed rate command to maintain stability and responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the feed rate of coal is changed for load fluctuation of the boiler, then the boiler load response is improved, but the delay of coal output from the mill varies depending on coal properties, causing disturbance in steam temperature or steam pressure control
Solution Approach 1:
The control device measures actual coal output from the mill and feeds this information back to the control system. The feedback signal is used to generate correction signals that adjust the coal feed rate command, thereby compensating for variations in coal output delay caused by different coal properties and maintaining stable steam temperature and pressure control.
Solution Approach 2:
The control device calculates a coal output delay correction value based on measured coal output before it fully affects the boiler steam parameters. This preliminary correction is applied to the coal feed rate command in advance, allowing the system to proactively compensate for delays rather than reacting after disturbances occur.
2Device complexity
If conventional control methods are used without coal output estimation, then the control system is simpler, but the delay of coal output becomes a disturbance that cannot be compensated
Solution Approach 1:
The control device introduces an intermediary measurement system that directly measures coal output from the mill. This intermediary measurement provides real-time information about actual coal output, which is then used to generate correction signals. This intermediary layer bridges the gap between coal feed rate command and actual boiler input, enabling compensation without requiring complex predictive models.
3Ease of operation
If no correction signal is applied, then the control device is simpler to operate, but the deviation between current and standard coal output patterns causes instability in boiler operation
Solution Approach 1:
The control device automatically calculates correction signals based on measured coal output and compares it with the standard coal output pattern. The system self-adjusts the coal feed rate command without requiring manual intervention or complex operator judgment, maintaining stable boiler operation while keeping the operation interface simple.
Data Source
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AI summary
There is provided a control device of a coal pulverizer which enables estimation of a coal output with a precision suited for a purpose. In a control device of a coal pulverizer which pulverizes coal by the coal pulverizer and estimates coal output by which the pulverized coal is output to a boiler, the control device includes a main operation circuit which calculates a command signal associated with a coal feed rate on the basis of detection data from a boiler or a power generator connected to the boiler, and an additional control unit which calculates the deviation between a standard coal output pattern preset in the coal pulverizer, and a current coal output pattern, and adds a calculation result by the additional control unit to the main operation circuit as a correction signal.