Using greenhouse gases in the synthesis gas production processes: Thermodynamic conditions

The work concerns the thermodynamic analysis of CH₄ reforming with various oxidants (CO₂, H₂O, O₂) in the technological variants DRM (Dry Reforming of Methane) and TRM (Tri-reforming of Methane) technological variants. Both processes of synthesis gas production (raw material for the production of value-added products) are problematic in terms of environmental protection. In the process, two components of greenhouse gases are used as a substrate: CO₂ and CH₄. The influence of temperature, pressure, and the molar ratio of oxidants to methane on the efficiency of both processes was analyzed using the deterministic method: raw material conversion, product efficiency and selectivity - H₂ and CO, and the value of the H₂/CO ratio characterizing the suitability of the synthesis gas for various syntheses. The problem of carbon deposition tendency in DRM was minimized through the selection of operational process conditions, and in the case of TRM, it was fully reduced. The deterministic method of non-linear programming by defining the objective function with constraints helped formulate allowed one the values of TRM parameters: complete reduction of the coking problem, maintaining the H₂/CO ratio at the desired level - 2 and CO₂ conversion equal to 90%, led to a hydrogen efficiency of over 90%. This efficiency can be obtained at the process temperature T = 273 K, with a pressure of 1 atm, and the molar ratios of oxidants to methane: CH₄/CO₂/H₂O/O₂ = 1/0.36/0.77/0.01.

Experimental and simulation assessment to mitigate the emission of sulfide toxic gases and removing main impurities from Zn + Pb + Cu recovery plants

An integrated novel approach employing the Taguchi method and Aspen Plus software has been applied to evaluate a new configuration for the industrial process of Zn + Pb + Cu recovery from sphalerite ore, in order to minimize the toxic gas emission. The optimum operating condition achieved by the Taguchi method has been used as initial data for the process simulation. The impact of operating parameters on the process performance is considered. The optimum condition for the conversion of sulfide toxic gases to H2SO4 have been found to be: acid concentration of 0.867 mol/L, reaction temperature of 120 °C, stirring speed of 400 rpm, leaching time of 120 min, sulfide ore particle size of 0.01 mm; solid-to-liquid ratio of 30 wt%, additives amount of 50 kg/ton and oxygen pressure of 200 psi. Under optimum condition, H2SO4 production from sulfide toxic gases is 99%, the removal percentage of Fe, Co, Mn, Ni and Cd impurities is 99% and the recovery percentage of Zn + Pd + Cu is more than 97%.