Gas boilers exhibit thermal inefficiency and unsatisfying pollutant emissions. In this study, numerical simulations were conducted to examine the effect of humidified oxygen-enriched air on methane combustion in a furnace and the effects of different premixed ratios of air on the temperature field inside the furnace, intermediate product OH groups, component concentration distribution, and pollutants. Although humidification of ambient air effectively reduced the flame center temperature and mass concentration of the NOx generated during combustion in the furnace, the highest growth rate of CO concentration at the furnace outlet was 18.6%. Humidification of oxygen-enriched air increased the center temperature and outlet NO concentration of the furnace compared with those during no oxygen enrichment, but the outlet CO concentration showed a decreasing trend, with the highest decrease rate of 34.6%. This study determined an optimal CO–air premix ratio with a moisture concentration of 50 g/kg dry air and an oxygen concentration of 23%. The air humidification and oxygen enrichment technology proposed in this article provides a technical reference for low nitrogen transformation of existing gas boilers.

The adsorption thermodynamics and kinetics of CO₂ and six combustion products (H₂O, SO₂, N₂, O₂, NO and NO₂) of two most commonly used commercial zeolites (13X and 5A) were studied based on validated molecular simulations. Adsorption isotherms at wide range of temperatures (253–333 K) were fitted by a Langmuir model, obtaining equilibrium parameters including the adsorption capacity, strength, heterogeneity and CO₂ selectivity from the mixture. The diffusion coefficients, isosteric adsorption heats and distributions of potential energy were simulated for further explanation. The comprehensive evaluation results suggest that, in actual combustion product mixtures, the presence of H₂O in combustion products has a significant impact on CO₂ capture efficiency. Under the influence of water, the adsorption capacity of CO₂ was reduced by over 80%.

Rapid-cycle pressure swing adsorption (PSA) with small adsorbents particles is intended to improve mass transfer rate and productivity. However, the mass transfer mechanisms are changed with reduction of particle size during rapid-cycle adsorption process. A heat and mass transfer model of rapid-cycle PSA air separation process employing small LiLSX zeolite particles is developed and experimentally validated to numerically analyze the effects of mass transfer resistances on the characteristics of cyclic adsorption process. Multicomponent Langmuir model and linear driving force model are employed for characterizing the adsorption equilibrium and kinetic. The results of numerical analysis demonstrate that the dominant mass transfer resistance of small adsorbents particles is a combination of film resistance, axial dispersion effect and macropore diffusion resistance. The oxygen purity, recovery and productivity of the product are overestimated by ~2–4% when the effect of axial dispersion on mass transfer is ignored. As particle size decreases, the front of nitrogen-adsorbed concentration and gas temperature become sharp, which effectively improves the performance. However, the adverse effect of axial dispersion on the mass transfer becomes significant at very small particles conditions. It is nearly identical shapes of nitrogen concentration and gas temperature profiles after adsorption and desorption steps. The profiles are pushed forward near the production end with an increase in bed porosities. The optimal oxygen recovery and productivity are achieved with a particle diameter of 0.45 mm and bed porosity of 0.39 during the PSA process.

People who live and work in air-conditioned rooms with micro-hypoxia are prone to sick building syndrome (SBS). Enriching oxygen into an air-conditioned room to increase the oxygen concentration can improve indoor air quality (IAQ) and reduce ventilation to save building energy consumption. In the present paper, the number and diameter of the oxygen supply vents, the oxygen supply flow rate, the oxygen supply method and the air flow organization form were comparatively studied using a numerical model. The results were compared with the experiments results in un-air-conditioned rooms, which showed that this model can give a favorable prediction. The results show that the maximum axial velocity decreases with the increase of the axial distance under air-conditioned conditions. The relationship between the oxygen-enriched area and the oxygen flow rate is obtained by fitting. The diameter of the oxygen supply pipe is 0.006 m, and when oxygen supply methods 1# and 4# are adopted, the oxygen-enriched area is F = 0.4 + 0.383 Q and F = 0.237 + 0.8 Q, respectively.

Computational fluid dynamics (CFD) was adopted to investigate the influence of the three-section opening strategy in the Z type centripetal radial flow reactor on the uniformity of the gas flow, which aimed to optimize the opening rate of the reactor. The simulation results showed that as the pore-opening ratio of are 10%, 16% and 29% for three sections from top to bottom of the central channel, the opening rate of the circular channel perforated plate is 10–12%, 21–25% and 30–40% from top to bottom, respectively; the uniformity of the reactor was then achieved. Through the simulation results, it was also found that the change in the opening rate at the center pipe perforated plate had a greater contribution to the gas flow mal-distribution inside the reactor. The contribution of the change in the opening rate of the annular channel perforated plate to the uniformity of the gas flow inside the reactor was smaller than that of the center pipe. Annular channel width should not be smaller, such that gas flow malfunction inside the reactor could be avoided, although high-speed velocity cases were encountered.

In this work, a molecular simulation method was used to study the adsorption of seven combustion products (CO₂, H₂O, SO₂, N₂, O₂, NO and NO₂) on three zeolites with different topological structures (4A, MIF and MOR). Adsorption isotherms of pure components and mixtures at a wide range of temperatures (253–333 K) were calculated using the Monte Carlo method, obtaining equilibrium parameters including the adsorption capacity, adsorption heat and energy distribution. The calculation results indicated that 4A zeolite with more micropores has a stronger adsorption performance for CO₂. The presence of water significantly reduced the CO₂ capture efficiency of the three zeolites, and the CO₂ adsorption amount decreased by more than 80%. Adsorption kinetics was studied using the molecular dynamic (MD) method, MFI and MOR, with channel-type pore structures exhibiting stronger gas diffusion performance, though their separation efficiency was not high. A 4A zeolite has the potential for kinetic separation of CO₂.