Evaluation of a tetramine-appended MOF for post-combustion CO2 capture from natural gas combined cycle flue gas by steam-assisted temperature swing adsorption

Abstract

A novel tetraamine-appended metal-organic framework (MOF), exhibiting double- stepped isotherm was explored in a 3-step steam-assisted temperature swing adsorption process (SA-TSA) for CO2 removal from dry flue gas emitted from natural gas-fired power plants (NGCC). The reported material exhibited properties highly suited for CO2 capture from dilute sources. Extensive numerical simulations were performed to comprehend the impact of isotherm shape, heat transfer coefficient, feed temperature and heat capacity of solid on adsorption and desorption dynamics in a fixed bed. A multi-objective optimization was performed to identify operating conditions that achieve low steam consumption and high productivity while maintaining high purity (>=95%) and high recovery (>=90%). It was found that high purity and high recovery are obtained only when the process is isothermal. Thermal fronts propagating through the column impact the process performance. We show that the process cannot achieve recovery targets, i.e., >=90%, unless heat is removed from the system rapidly. The lowest achievable specific steam consumption is ≈45 kg steam/kg CO2 cap and highest achievable productivity is ≈ 0.1 mol CO2/m3 ads/s in an isothermal scenario.

Fitting Adsorption Isotherms with Symbolic Regression

“…However, SR was able to identify functional forms that fit these data well. Figure 6a shows several functional forms created with SR alongside the original experimental data from Kim et al Figure 6b similarly shows a model fit for this dataset originally proposed by Bharath and Rajendran 34 (eq 4 in Table 5) as well as a fit using a "dual-site" adaptation of the Bingel-Walton isotherm (eq 5 in Table 5).…”

“…For this example, a complexity of 99 gives a relatively simple expression that gives a good, but not perfect, fit to the experimental data. Table 5 lists an expression used by Bharath and Rajendran 34 to fit this dataset as well as an adaptation of the Bingel−Walton isotherm to fit this two-step isotherm form.…”