Chemical Composition Determination at the Bottom Region of a Recovery Boiler Furnace by Direct Minimization of Gibbs Free Energy

Abstract

An optimization strategy has been applied to describe the chemical composition at the furnace bottom in the Kraft recovery boiler of a pulp production process. The concentrations of each involved chemical species were calculated through an optimization approach, minimizing the Gibbs free energy of the system. Various systems were proposed and tested, assuming different chemical species and phases number. Because serious initialization problems were found at this stage for some of the proposed systems, an optimization heuristic method (PSO) was used for the first approach to the problem. Once the appropriate phases number and chemical species in the system were determined, the initialization problems disappeared and the use of a deterministic optimization method (SQP) became viable. The proposed approach has shown to be satisfactory to reproduce industrial data and also data reported in the open scientific literature.

Reduction efficiency prediction of CENIBRA's recovery boiler by direct minimization of gibbs free energy

“…Table 6 (test 1 to 7). The model reproduces the behavior reported in literature and that is expected for the system (Costa et al, 2005;Adams, 1997;Grace, 1992). Na 2 CO 3 and Na 2 S are the principal chemical species of the obtained smelt (condensed phase) as reported by Adams (1997) and Grace (1992).…”

“…Grace (1992) affirms that the furnace bottom of the recovery boiler is poor in oxygen and this information is shown in Table 6. Costa et al (2005) studied a different recovery boiler and reported that the increase of black liquor feed promotes an increase of the reduction efficiency since the oxygen concentration is fixed. This behavior is observed in Table 6.…”

“…; 7) N 2 is inert. Costa et al (2005), Costa et al (2004) and Costa et al (2003) report that the oxidation and reduction reactions take place simultaneously in the solid phase. Then, the chemical species only melt, forming the smelt, after the chemical equilibrium has been reached.…”

Proposta de emprego de conceitos de equilíbrio químico na descrição matemática da câmara de combustão de caldeira siderúrgica

“…Na literatura diversas pesquisas usam esta metodologia para predizer a composição de sistemas com muitas espécies e diversas fases em equilíbrio químico [9][10][11][12][13][14]. A energia de Gibbs total de um sistema fechado, à temperatura e a pressão constantes, diminui durante um processo irreversível e a condição de equilíbrio é atingida quando a energia de Gibbs alcança seu valor mínimo [15].…”

Investigação do comportamento viscoelástico de amostras de licor negro oriundas do processo de polpação Kraft da Cenibra-MG à 25 oc

“…[18][19][20][21][22] Diante dessas informações, o presente trabalho teve como objetivo a investigação do comportamento viscoelástico de amostras de licor negro de madeira de eucalipto (hardwood), resultantes do processo Kraft na Celulose Nipo Brasileira -CENIBRA, localizada no município de Belo Oriente-MG. As amostras foram coletadas nos seguintes estágios do processo Kraft: 1) após a estação de evaporação 2 de múltiplos efeitos -EVA2 (licor negro sem cinzas -LNSC), e 2) após tanques de reciclagem de cinzas de caldeira, nas vizinhanças da caldeira de recuperação 3 -RB3 (denominada licor negro com cinzas -LNCC); ambos com concentrações de sólidos da ordem de 70%, comum para amostras de LN. 23,24 Tais amostras foram escolhidas afim de se realizar um estudo comparativo.…”