Illustration of interface calculation in batch pipeline systems

The remaining constraints (3.13)-(3.28) remain unchanged. This constitutes the sELSP model with global stocks and interface handling (sELSP-BP-IF). 

A third option to handle interfaces is extraction and external post-processing. This implies that all batches reduce to a certain amount due to the associated interfaces. To reflect this speciflc interface handling procedure in the sELSP-BP-IF, the values of dgt have to be strictly negative such that qsi are negative, too. Note that this implies a total loss of material due to the pumping process. 

Note further that the MINLPs introduced above are hard to solve to optimality even for very small problem sizes. Presumably, heuristics developed for the classic ELSP 

Another approach which promises a good prospect for adoption is the genetic optimization approach of Chatfield (2007). 

Example 5 (Batch pipeline sequencing). Suppose a one-to-one serial pipeline that connects two chemical sites. The provider site prodtices the raw and intermediate materials for the consumer site. Suppose that the consumer site produces Styrene-based chemicals such as Polystyrene and Styrene-Butadiene rubber. Raw materials for Styrene production are Benzene and Ethylene. Among others, a steam cracker provides Ethylene and Pygas, which is subsequently refined to Benzene. It is assumed that the capacities of these plants are unbalanced such that the deficit of Pygas and Benzene has to be imported. Additionally, the cracker feed, Naphtha, has to be imported. 

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Figure 3.6 Illustration of interface calculation in batch pipeline systems.

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