Modeling and control of a pulp mill process

This work presents the first complete benchmark problem of a pulping process including the derivation of the nonlinear dynamic model with all the operating conditions, and a complete plantwide control study comparing classical decentralized control with model predictive control (MPC).; An introduction to the theory of MPC is provided using state-space models and step response coefficient models to derive the predictive equations for MPC. Linear programming (LP) and quadratic programming (QP) formulations of MPC are presented to study their qualitative behavior and performance with an application to the Shell control problem.; A control study of the fiberline section of the pulp mill process is presented. Decentralized control is compared with centralized model predictive control (MPC) and a hybrid control strategy with MPC for the digester and decentralized control for the rest of the process. The main drawback of such control study is that the control of the fiberline was considered in isolation from the chemical recovery loop, therefore a benchmark of the complete process (fiberline and chemical recovery) is considered.; The complete details of the pulp mill benchmark are provided, including the different operating modes, control objectives, input and output constraints, costs of chemicals and utilities, selling price of products, and process measurements. A heuristic is presented to determine the best possible plantwide control strategy among multiple alternatives by studying their ability to minimize the total error and increase the operating profits. The heuristic is applied to compare the performance between decentralized control and unit-based model predictive control of the process.; The dynamic mathematical model of the pulp mill process is derived. Each of the major unit operations is described in detail including: digester, bleach towers, black liquor evaporators, recovery boiler, recausticizing, and lime kiln. Models for secondary units like washers, heaters, storage tanks, etc. are also included.; The details of the benchmark problem as well as the source/binary code for all the unit operations, and all the data files will be made freely available for download from the Internet.