Md. Saiful Alam

Optimized combustion of biomass volatiles by varying O2 and CO2 levels: A numerical simulation using a highly detailed soot formation reaction mechanism

To increase syngas production and minimize soot, polycyclic aromatic hydrocarbon (PAH), and CO(2) emissions resulting from biomass combustion, the evolution of biomass volatiles during O(2)/CO(2) gasification was simulated. A highly detailed soot formation reaction mechanism flowing through the reactor, involving 276 species, 2158 conventional gas phase reactions and 1635 surface phase reactions, was modeled as a plug flow reactor (PFR). The reaction temperature and pressure were varied in the range 1073-1873K and 0.1-2MPa. The effect of temperature on product concentration was more emphasized than that of pressure. The effect of O(2)/CO(2) input on product concentration was investigated. O(2) concentration was important in reducing PAHs at low temperature. Below 1473K, an increase in the O(2) concentration decreased PAH and soot production. However, if the target of CO(2) concentration was higher than 0.22 in mass fraction terms, temperatures above 1473K reduced PAHs and increased CO.

Electrochemical and spectroscopic insights of interactions between alizarin red S and arsenite ions

Interferences of arsenite ions on electrocatalytic oxidation of alizarin red S (ARS) was studied using Pt and ITO electrodes. A Pt electrode can oxidize both arsenite ions and ARS molecules simultaneously. The oxidation wave of ARS exceeds that of arsenite until the [AsO2−]/[ARS] ratio surpasses 0.07. Meanwhile, an ITO electrode can oxidize only ARS molecules. It was seen that the diffusion coefficient of ARS molecules decreased from 4.3 × 10−6 cm2 s−1 to 1.68 × 10−7 cm2 s−1 in the presence of arsenite ions. The electrokinetic investigation shows that ARS oxidation was a two-electron transfer consecutive process. The EIS studies showed that charge transfer resistance was increased in the presence of arsenite ions during ARS oxidation.

Sensitivity analysis of coal gasification in two-stage entrainedflow Gasifier: Syngas and carbon conversion prediction

The energy production from coal-fired power plant is increasing day by day, which result in increased CO 2 emission from the existing power plant. However, CO 2 emission from coal gasification can be reduced if an efficient CO 2 /O 2 /N 2 coal gasification is implemented in IGCC system. Numerical simulations of coal gasification under CO 2 /O 2 /N 2 gasification condition are carried out with the aim of describing the effects of model parameters, char reaction rates, operating conditions and heat losses to increase the syngas heating value and carbon conversion in a two stage entrained flow coal gasification process. The Eulerian–Lagrangian approach is applied to solve the Navier–Stokes equation and the particle dynamics. Finite rate/eddy dissipation model is used to calculate the rate of nine homogeneous gas-to-gas phase reactions. While only finite rate is used for the heterogeneous solid-to-gas phase reactions. It is found that the carbon conversions of combustor coal lie in the ranges from 97 wt% to 99 wt% for most of the calculated conditions. On the other hand, the carbon conversion of reductor coals varies from 45 wt% to 57 wt%. A noticeable change is obtained when the gasification occurs under a high-temperature condition. Remarkable outlet results of about 32 wt% CO, 0.58 wt% H 2 and 89 wt% overall carbon conversion are predicted if a high temperature of 1673K is maintained in the reductor. On the other hand, a reduced soot concentration is predicted if the O 2 concentration and/or the reductor gas temperature increase(s) in the gasifier.

Syngas Production from Coal Gasification with CO2 Rich Gas Mixtures

Coal gasification with CO2 rich gas mixture is one of several promising new technologies associated with CO2 reduction in the atmosphere. Coal gasification with high CO2 concentration is suitable for producing large amount of syngas. However, an increase in CO2 concentration will result in lower gas temperature in the reactor. In this paper, a similar gas temperature profile in CO2/O2 mixtures to that of coal gasification in air is predicted by observing the effects of CO2 concentration. The coal gasification model considered in this calculation is composed of devolatilization model, char gasification model and gas phase reaction model. Reaction rate equation of n-th order type with the Random Pore Model is applied to the char gasification reaction. Influence of inlet particles size is also studied. It is found that 20 μm particles in 21% O2/79% O2 and 100 μm particles in air (21% O2/79% N2) result in a similar gas temperature profile during coal gasification. The outlet gas mixture with the same calorific value as from air blown coal gasification can be obtained if air is replaced by 50% CO2/29% N2/21% O2 mixtures