Utility system optimization

Optimal process synthesis Two problems (a) chemical process optimization for maximization of net present value (NPV) while minimizing uncertainty in the future demand of two products, and (b) utility system optimization for minimization of both total annual cost and CO2 emission. Multi-Criteria Branch and Bound (MCBB) Algorithm The existing MCBB algorithm was modified to increase speed, reliability and suitahility for a wide range of applications. Mavrotas and Diakoulaki (2005)... 

In the Example Problem given below we adopted a MILP formulation for the utility system optimization. 

Once the highest steam level is set, then intermediate levels must be established. This involves having certain turbines exhaust at intermediate pressures required of lower pressure steam users. These decisions and balances should be done by in-house or contractor personnel having extensive utility experience. People experienced in this work can perform the balances more expeditiously than people with primarily process experience. Utility specialists are experienced in working with boiler manufacturers on the one hand and turbine manufacturers on the other. They have the contacts as well as knowledge of standard procedures and equipment size plateaus to provide commercially workable and optimum systems. At least one company uses a linear program as an aid in steam system optimization. 

Large and complex utility systems often have significant scope for optimization, even without changing the utility configuration. Consider now the optimization of a fixed utility configuration. First, the degrees of freedom that can be optimized in utility systems need to be identified. 

Figure 23.53 Optimized operating conditions for a site utility system (flows in t h j. (From Varbanov PS, Doyle S and Smith R, 2004, Trans IChemE, 82A 561, reproduced by permission of the Institution of Chemical Engineers.)...

Table 23.7 The performance of the optimized utility system in Figure 23.539.

The only way to reconcile the true cost implications of a reduction in steam demand created by an energy reduction project is to use the optimization techniques described in the previous section. An optimization model of the existing utility system must first be set up. Starting with the steam load on the main with the most expensive steam (generally the highest pressure), this is gradually reduced and the utility system reoptimized at each setting of the steam load. The steam load can only be reduced to the point where the flowrate constraints are not violated. 

Majozi, T., Zhu, X., 2001. A novel continuous-time MILP formulation for multipurpose batch plants.l. Short-term scheduling. Ind. Eng. Chem. Res., 40(23) 5935-5949 Quesada, I., Grossmann, I.E., 1995. Global optimization of bilinear process networks with multicomponent flows. Comput. Chem. Eng., 19 1219-1242 Savelski, M., Bagajewicz, M., 2000. On the optimality conditions of water utilization systems in process plants with single contaminants. Chem. Eng. Sci. 55 5035-5048... 

Denholm, P. and Short, W. (2006). An Evaluation of Utility System Impacts and Benefits of Optimally Dispatched Plug-in Hybrid Electric Vehicles. Technical Report NREL/TP-620-40293, National Renewable Energy Laboratory (NREL), Colorado. 

The cell and stacks that compose the power section have been discussed extensively in the previous sections of this handbook. Section 9.1 addresses system processes such as fuel processors, rejected heat utilization, the power conditioner, and equipment performance guidelines. System optimization issues are addressed in Section 9.2. System design examples for present day and future applications are presented in Sections 9.3 and 9.4 respectively. Section 9.5 discusses research and development areas that are required for the future system designs to be developed. Section 9.5 presents some advanced fuel cell network designs, and Section 9.6 introduces hybrid systems that combine fuel cells with other generating technologies in integrated systems. 

Other utility systems offer cost swings in optimization but on a reduced I... 

Papoulias, S., A.. and Grossmann, I. E. A Structural Optimization Approach in Process Synthesis. Part I. Utility Systems. Comput. Chem. Eng. 7, 695 (1983a). 

M. Bagajewicz, M. Rivas and M. Savelski, 2000, A robust method to obtain optimal and sub-optimal design and retrofit solutions of water utilization systems with multiple contaminants in process plants, Computers and Chemical Engineering, 24, 1461-1466. 

Description Suspension crystallization of PX in the xylene isomer mixture is used to produce PX crystals. The technology utilizes an optimized arrangement of equipment to obtain the required recovery and product purity. Washing the paraxylene crystal with the final product in a high-efficiency pusher-centrifuge system produces the paraxylene product. 

The system under investigation is identical to the system established in S ection 7.2.1. As a result, the AR for the batch system will be constructed in the same space and feed point (Cf = [CAf, CBf, Cof] = [1,0, 0] mol/L). We are also able to utilize the optimal reactor structures, developed in Section 7.2.1, and convert them to batch structures without the need to perform additional analysis. The critical a policy for the DSR, given in Section 7.2.1.5, will be used for the F/V policies in the batch system. 

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