Overview of the Methodology for CO, Integration

1 CO2 stream source and demand selection and data extraction 

Process Systems Engineering Tools for Biomass Polygeneration Systems 233 

The purity and flow rate constraints imposed by the CO demand streams are captured by formulating a material balance on the total streams and a material balance on CO. The total flow rate of CO -containing streams available from the sources must be in excess or equal to the total flow rate of CO -containing streams required by the demands as the first necessary condition for the exchange network to be feasible. This is established from the overall mass balance of the network as shown in Equation 9.9  

The surplus diagram captures the purity constraints in the network. If the cumulative net COj is negative at any purity level (i.e. surplus curve crosses y-axis), then the network is not receiving the required amount of CO at the adequate purity. In that case, at least one of the constraints imposed by the demands cannot be satisfied by the sources, rendering the network unfeasible. To make the network feasible, a purified CO stream is required. Then, the options are (i) to import a high-purity stream or (ii) introduce a purification unit to increase the purity of a low-purity stream. Therefore, the second necessary condition for network feasibility is that the balance of CO in the overall system (i.e. the cumulative net CO flow rate) must always be positive. This means that the entire CO surplus curve must lie at or above zero flow rate for the network to be feasible. 

If both the first and second necessary conditions are met, then the CO integration problem has at least one feasible solution. One possible solution is when the system is, at some point, constrained in CO supply, that is, there is no surplus or deficit. This condition sets the initial 

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