Two-hopper coal and limestone feeder control system
(Lime Kiln Skip Lift Automatic Loading System).

A project has been implemented to automate the process of preparing a mixture of two components: coal and limestone (for loading into lime kilns).

The functional diagram of a two-hopper coal and limestone dispenser is shown in Pic. 1, where:

• 1. Weighing hopper for dosing coal (first weighing hopper).
• 2. Storage hopper for limestone.
• 3. Device for unloading coal from the first weighing bin.
• 4. Feeder with reciprocating movement of the feeding device.
• 5. Weighing hopper for a mixture of coal and limestone (second weighing hopper).
• 6. Gate for unloading a mixture of coal and limestone.

The dosing controllers included in the control system provide the followingalgorithm for the operation of a two-hopper coal and limestone doser:

• 1) waiting for the “Start” button located on the front panel to be pressed (if the “Mode” switch is in the “Manual” position, the dosing cycle will not start);
• 2) turning on the coal feeder into the first weighing hopper;
• 3) waiting for the specified dose of coal to be reached and turning off the feeder;
• 4) turning on the device for feeding stone into the second weighing hopper and the device for unloading coal from the first weighing hopper (the combined inclusion of the feeder and unloading device ensures mixing of coal and limestone);
• 5) waiting for the first weighing bin to be unloaded and turning off the coal unloading device;
• 6) waiting for the specified dose of coal and stone to be reached and turning off the stone feeder;
• 7) generation of the “dose is ready” signal;
• 8) waiting for the end signal “skip below”;
• 9) unloading the contents from the second weighing bin into the skip (opening the damper and checking the “damper open” sensor);
• 10) turning off the unloading device from the second weighing bin (closing the damper and checking the status of the “damper closed” sensor);
• 11) generation of the “skip loaded” signal;
• 12) waiting for the end signal “skip up”;
• 13) transition to the beginning of the cycle of step 2 (if the “Cycle” switch is in the “Off” position, then a new dosing cycle will not start).

Total dosing results

Dosing controllers accumulate and store the total dosing results. The maximum value of the total mass is 4294967295 (does not depend on the position of the decimal separator), the number of doses is 65535. If after the next dosing cycle the total mass S exceeds the maximum value, then a value equal to: S – 4294967295 will be stored in the device’s memory.

At the completion of each dispensing cycle, the total results are updated (incomplete cycles are not taken into account) and saved in non-volatile memory, so this data is not lost when the power is turned off.

When the dispenser is stopped, you can display the total mass of any of the components (total mass of coal or limestone) on the indicator.

Rice. 2. Total mass.

        CS Features:

• dosing controllers are powered from a 24V power source;
• CS equipment is installed in an IP54 cabinet to protect the equipment from dust (Fig. 3);
• on the cabinet panel there is a light alarm “Work”, “Dose ready”, “Skip loaded”;
• control outputs for actuators – relay contacts (220V 5A);
• total dosing results are stored in non-volatile memory;
• digital output for PC connection (RS232, RS485).