I want to create an optimized schedule and production to meet demand of four different buyers. I am starting with Pulp but not able to account for continuous production variable and discrete dispatch together. I have following details, objective is to avoid tank top situation:
- Expected production is constant at 6,000m3/h.
- Storage capacity is 400,000m3,
- LNG carrier parcel size is 300,000m3 (1 parcel every 50h),
- Ship loading rate is 20,000m3/h,
- Start of loading occurs such that stock level at end of loading (operational buffer) is 40,000m3.
Objective (Maximmize) = $150/m3*(Volume Shipped on time) - $100/m3*(Volume Produced)-$200/m3*(Volume wasted due to tank top) + $100/m3*(delayed volume shipping)
Constraints: Tank Capacity (Minimum & Maximum); Shipping Capacity (One loading every 50 h)
Decision Variable: Production Rate (+/-10%) Shipping Schedule (+/-24h)
..............Adding details................ With the details mentioned above, I have a base schedule. Now when my production rate changes, I want to move the schedule accordingly such that I am either moving the ships around (comes with a penalty) or using the extra volume (in case of increased production) to load an additional cargo of same capacity or cancel a cargo (in case of reduced production) to ensure that the rest of the schedule is closely met.
so, two decisions to be made:
- Move the ships slightly (number of hours)
- Add or remove a cargo (Where in schedule to put to move the rest the least)
Objective function: Cost minimization = Penalty to move ship + (benefit/loss) of change in number of cargoes
Looking for help. PS: I am looking forward to solve this in continuous time frame.