Pipeline transport is the major means for large-scale and long-distance CO 2 transport in a CO 2 capture and sequestration (CCS) project. But optimal design of the pipeline network remains a challenging problem, especially when considering allocation of intermediate sites, like pump stations, and selection of pipeline routes. A superstructure-based mixed-integer programming approach for optimal design of the pipeline network, targeting on minimizing the overall cost in a CCS project is presented. A decomposition algorithm to solve the computational difficulty caused by the large size and nonlinear nature of a real-life design problem is also presented. To illustrate the capability of our models. A real-life case study in North China, with 45 emissions sources and four storage sinks, is provided. The result shows that our model and decomposition algorithm is a practical and cost-effective method for pipeline networks design.
In this paper, the flow behavior of gas−solid flow in the standpipe of a circulating fluidized bed (CFB) and its influence on the system pressure balance and hydrodynamic performance have been studied. A CFB apparatus with a square riser of 0.1 × 0.1 m in cross-section and 4.5 m in height and a standpipe of 3.0 m in height and 0.08 m in diameter were established. The standpipe connected the riser to a loop seal on one end and connected to the cyclone on the other end. The experimental results showed that the flow behavior in the standpipe is not only strongly related to the particle holdup, the structure, and the aeration flow rate of the standpipe and loop seal but also strongly coupled with the pressure drops of the rest of the parts of the CFB system. At fixed-bed inventory M
t and fluidizing gas velocity in the riser U
g, the solid circulating rate G
S increases with the flow rate of aeration air Q in the loop seal. With an increasing GS, the pressure drop of the loop seal decreases, while both the pressure drops of the riser and cyclone increase. The flow pattern of the gas−solid two-phase flow in the standpipe and the gas−solid slip velocity change when the pressure drops of the rest of the parts of the system change. Normally, the gas−solid flow can be categorized into transient packed-bed flow (TPBF). With an increasing Q, the flow rate of downward-moving gas flow entrained by the circulating solid increases at first to a maximum value and then decreases because of the presence of bubbles in the loop seal and the bottom of the standpipe. Beyond the critical value of Q, the flow state in the standpipe becomes bubbling fluidization. The calculation results based on the TPBF agree well with the experimental data and the prediction of the transition of the flow state in the standpipe.
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