Esdras P. Carvalho

Reduced gradient method combined with augmented Lagrangian and barrier for the optimal power flow problem

A new approach for solving the optimal power flow (OPF) problem is established by combining the reduced gradient method and the augmented Lagrangian method with barriers and exploring specific characteristics of the relations between the variables of the OPF problem. Computer simulations on IEEE 14-bus and IEEE 30-bus test systems illustrate the method.

Multi-objective Heat Exchanger Networks Synthesis Considering Economic and Environmental Optimization

Abstract In the present paper it is presented a model for the synthesis of HEN considering both economic and environmental features. The model presents a multi-objective mixed-integer non-linear programming (MINLP) formulation. The optimization problem aims to find the optimal HEN considering the total cost as well as the environmental impact minimization. Environmental aspects are incorporated to the objective function by considering Life Cycle Assessment (LCA), using SIMAPRO software. ReCiPe methodology is used and 18 impact categories from midpoint to endpoint are evaluated. An algorithm based on Particle Swarm Optimization (PSO) was developed to solve the model and a superstructure that considers the number of stages as an optimization variable is proposed. A literature case was chosen to test the model applicability. Results are better than the previously published ones, even considering environmental impacts. Furthermore, not all impact metrics are in conflict with the cost function.

Modeling and optimization of an ammonia reactor using a penalty-like method

Abstract Ammonia is one of the most important chemicals produced in the world. Due to its broad applicability, modeling and simulation of process of ammonia has received considerable attention among the industrial processes. Ammonia is produced from the reaction of hydrogen and nitrogen at high temperature and high pressure along with a catalyst. Its production depends on temperature of feed gas at the top of the reactor, the partial pressures of the reactants and the reactor length. The optimal design problem requires obtaining the optimal reactor length with maximum economic return subject to a number of equality constraints involving solution of coupled nonlinear differential equations. A more efficient algorithm for the solution of optimization-constrained differential equations is proposed by coupling numerical techniques (barrier function with a direct search method) with Runge–Kutta method. The global convergence of the proposed algorithm is established under some usual conditions. Numerical results showed that the resulting algorithm, based only on function values, is highly competitive with other global optimization methods.