Examples of Using Pro-Plan
The following scenarios show how Pro-Plan would be used in a mill with 3 pulp lines, 2 evaporator lines, 2 recovery boilers, causticizers, lime kiln and 5 paper machines.
To start the process, click on the “View” and “Inputs” and the Inputs Dialog will appear:
This dialog shows the current levels in all storages, and the total pulp demands for the scheduled period. The entries for evaporators are the maximum flow into the evaporators. Click on “OK”.
To calculate the recommended strategy, click on “Solve” and “Solve”, and the following Recommendation Summary will appear:
For more detail, it is necessary to go to the graphic displays of the Pulp Mills, e.g. Click on "View", "Graphics" and "Pulp Line 1":
The graphics display shows the recommended rates for each production unit, and the predicted storage levels at the end of the period. The other pulp mills would show the following:
Pulp Line 3 has an off-line storage slab for crumbed pulp. Rules within Pro-Plan determine when pulp is fed to the slab and when it is reclaimed.
The predicted situation for the Weak Black Liquor (WBL) storages and evaporators, recoveries and recausticization areas is:
Another way of viewing the strategy is via trends that compare the predicted levels resulting from following the recommended strategy or continuing with the current strategy. To access the trends, click on "View", "Trends" and "WBL Storages":
If an evaporator wash is necessary, it is set up by clicking on"Evaps Wash" on the Inputs dialog:
Current Maximum: This is the maximum black liquor inflow before the wash.
Hours to Wash: The number of hours before the wash commences.
New Maximum: This is the expected maximum black liquor inflow after the wash.
When the schedule is solved for this situation, the following results:
During the wash, wash liquor is initially run back to the WBL Blend Tank, and then to the Spill Dam. The result of the reduced evaporator capacity is that the level of the liquor storages increases, but not enough to affect production.
If an evaporator line was off-line for the total schedule period (24 hours in this case), liquor storages would increase to their maximum allowed limits, and production would be affected:
To supply the same volume of pulp to the paper machines, at reduced pulp production rates, the desired levels of the storages have been reduced proportionately.
If a constraint is serious enough to restrict pulp production to the point where the pulp demand cannot be satisfied, then an appropriate strategy must be implemented to best handle the situation. Mill “business rules” must be established, agreed and replicated within Pro-Plan. These could include:
Shutting down pulp users
Slowing down pulp users
Changing grades on paper machines
For example, if the causticizers were off-line, and there was not sufficient volume in the White Liquor Clarifier, pulp production would be restricted, and pulp users would be shutdown in order of priority:
In this particular case, the order of priorities resulted in 3 paper machines being forced to shut. Pulp Line 1 was also shutdown, and Pulp Line 3 reduced to its minimum production rate.
Many different strategies can be chosen to deal with a given situation.
Market pulp mills, where output is maximized at all times (within constraints) is also catered for with Pro-Plan.
Forward planning: Pro-Plan has the option to step ahead in time by setting the predicted values of storage levels at the end of the period as the starting values for the next period. Thus many different situations, demands and planned outages can be considered over an extended period of time. This can be used to analyze the effect of an annual maintenance shutdown and to determine the level of stocks required.
Schedule Hours: default value is 24 hours, but can be changed to any value. Because this value sets the time period to achieve optimum levels, larger values are recommended to stabilize the production rates over time.
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