Study On The Design And Retrofit Of Steam Power System Considering Equipment Failure

The steam power system normally is designed to have higher efficiency for steam and power generation to achieve economic performance and emission reduction. In actual, equipment failure is inevitable and uncertain, and causes unstable system operation, and even system shut down, leading the steam and power generation fluctuates. Therefore, reliability analysis should be involved in the system design.In this work, the boiler system design is studied considering both the uncertainty of process steam demand and equipment failure based on mathematical programming method. The probability distribution is utilized for fluctuation of process steam demand and the Markov model is applied to deal with the boiler failure to express the uncertain parameter with probability. The approach of two-stage stochastic programming is to compensate the constraint violations caused by uncertain steam demand and boiler failure to reduce the effect on the optimization and constraints. A mixed integer linear programming model (MILP) is formulated with the objective of the minimum annual cost to design of system configuration, equipment modes and operation of compensating under flexible steam demand and equipment failure.Boilers are critical units for steam and power generation in the utility system. System retrofit might be carried out for various reasons such as the enlargement or adjustment of products of production process, leading to modification of the process steam demands. The existing boiler system is initially analyzed to assess steam generation at different retrofit conditions, in particular considering cases involving equipment failure and variation of the system demands. Retrofit measures are proposed including operation adjustments of modifying boiler operating load and switching boiler operating modes, and the introduction of extra equipment to add redundancy to the system with spare capacity. A mixed integer linear programming (MILP) model is formulated with the aim to achieve the minimum retrofit costs considering system penalty costs in the model to account for steam deficit due to boiler failures and steam demand fluctuating. A case study for a boiler system retrofit illustrates the proposed retrofit methodology.Steam and power systems should be designed with high reliability and flexibility to satisfy process energy and power demands and reduce penalty costs due to equipment failures and steam and power demand variations. Uncertainties of equipment failure and flexible process steam and power demands have different impacts on system reliability, steam and power generation, individual equipment operation performance, and process production loss due to utility deficits. This paper has proposed a procedure of the system design based on simultaneously modelling and optimizing of the structure and operation with system reliability analysis, and a mixed-integer linear programming (MILP) model is formulated associated with compensation costs and penalty costs to obtain both system configuration with spare equipment (in hot or cold standby) and spare capacities, and operating scheduling specification to account for equipment failures and process steam and power demand fluctuations. In this optimization, the effect of equipment failures on system operation performance and costs is analyzed by system reliability, and uncertain steam and power demands are formulated by a multi-period stochastic programming. Measures adopted to respond to uncertainties implementation include compensation options of equipment operating load sharing, equipment start-up, and equipment (in failure) repair, and penalties both of electricity import from the grid and production loss. A case study shows the application and effectiveness of the proposed methodology.