Mathematical Modeling of Hydrogen Production Process by Pressure Swing Adsorption Method

Abstract

A mathematical model of the dynamics of pressure swing adsorption (PSA) process during separating multicomponent gas mixtures to produce hydrogen has been developed. The model includes the equations of mass-and heat transfer processes which occur during adsorption (desorption) of the components (H 2 , CO 2 и CO) of gas mixture by granular zeolite adsorbents СаА, NaХ, LiLSX; the equation of the kinetics of mixed-diffusive transport of adsorbate (H 2 , CO 2 и CO); the LangmuirFreundlich isotherm equation for multicomponent gas mixtures; the Ergun equation for calculating the pressure and velocity of gas mixture in the adsorber, and allows calculating the profiles of component concentrations (H 2 , CO 2 и CO) and temperature in the gas and solid phases, pressure and velocity of the gas mixture along the height of the adsorbent depending on time. As a result of computational experiments, the effect of changes in the temperature, composition, and pressure of the initial gas mixture on the purity, recovery, and production hydrogen temperature at multiple duration periods of the adsorption stage was determined. The dynamics of the adsorption process of gas mixture components and the character of sorption and thermal fronts motion along the height of the adsorbent bed in the adsorber, as well as the relationship between the output of the 4-column PSA unit and the purity of the produced hydrogen have been studied.

Optimization of Adsorption Processes with Cyclic Variable Pressure in Gas Mixture Separation

“…-calculation of the current optimum adsorption pressure ˆ; ads P -calculation and formation of control actions on valve drives [1].…”

“…The analysis of the adsorption separation of gas mixture and hydrogen production in a 4-adsorption pressure swing adsorption (PSA) plant as a control object conducted in [1,2] made it possible to determine ( Mathematical modules for the hydrogen production process in the 4-adsorption PSA plant…”

“…A mathematical description of the dynamics of the adsorption process in the PSA plant adsorbers for hydrogen production [1] can be given in the form of a block diagram of the "Adsorber" mathematical module (Fig. 2).…”

“…However, the numerical values of the parameters obtained from these equations are recommended to be used as initial approximations for solving the inverse coefficient problem using the equations of the mathematical model [3]: The state of the valve is described by the components of the vector σ that are Boolean variables taking the values 0 or 1. The specific form of the function σ σ( ) t = is determined using the valve switching cycle of the PSA plant [1,2]. A mathematical description of the operating mode of the valve system of the 4-adsorption PSA plant for hydrogen production can be presented in the form of a block diagram of the mathematical module "Valve system" (Fig.…”

Optimizing cycles of adsorption separation of gas mixtures

“…One of the urgent problems in the field of adsorption separation is the production of hydrogen from hydrogencontaining process flows (gases of conversion and oxidation of hydrocarbons, refinery gases, synthesis gas, etc.) [2,4] and air oxygenation in medical concentrators and onboard oxygen production units [5,6]. Typical substances that accompany hydrogen are nitrogen, carbon oxide and dioxide, methane; oxygen is usually accompanied by nitrogen and argon.…”