Progressive inhibition of C+H2O reaction in wood char packed bed by in-situ evolving H2: Experimental insights and theoretical analysis.

Previous research on Char reactions with gas phase compounds under micro-thermogravimetry systems shows that hydrogen inhibits heterogeneous char reactions. However, its impact on larger gasification systems with evolving hydrogen profiles remains largely unexplored. This study examines a macro-scale wood char bed to understand the influence of in situ evolving hydrogen on char reactions. When subjected to a specific steam flux, carbon conversion and pore morphology changes are mainly confined to the bed's upstream, with the downstream char retaining its original characteristics. Numerical investigations reveal over 75 % of species production and consumption occurs within the initial 20 % of bed height. Fourier-transform infrared spectroscopy confirms hydrogen-induced inhibition in downstream segments, showing a shift from C-OH to C-H bonds. Particle-scale analysis indicates significantly higher rates of hydrogen diffusion and adsorption compared to H2O, impeding downstream C+H2O reactions. Increased temperature, higher reactant concentrations, or reduced residence time can overcome this inhibition, enhancing conversion rates. These findings are critical for optimizing steam-to-biomass ratios in oxy-steam gasification systems for generating hydrogen-rich syngas.

Investigations into the performance of single chamber sanitary napkin incinerators with emphasis on CO and CO2 emissions.

This paper investigates the performance of two commercially available sanitary napkin incinerators. On detailed preliminary investigations both the incinerators were found to have shortcomings to meet emission norms as per Indian standards for MSW incinerators. Parameters for the comparison were combustion efficiency and emissions, basically CO and CO2, to assess the quality of combustion. Carefully designed experiments, to improve the performance, revealed the need to evaluate the stochiometric air flow requirement and a need to modify. To enable better combustion inside the combustion chamber, it was established that airflow distribution, and mixing was necessary. The paper analyses the performance of the incinerators towards optimizing the air flow location and the air flow rate in the combustion chamber. Based on these studies it was evident that the commercially available designs are not suitable for five-napkin batches, as claimed by the manufacturers. A higher starting temperature (>600 °C) is essential for quick heating, and optimum an air supply (~10 LPM) is necessary for reducing environmentally sensitive emissions. Results indicated higher combustion efficiency, and a need for meeting the emissions norms as per Indian standards for MSW incinerators. Based on the performance of the devices and arriving at an optimal specification for the design, an alternative method of incineration using LPG gas torch retrofitted over the grate, was tested. The paper also discusses the preliminary results from the new design. The conducive environment in the combustion chamber resulted in higher combustion efficiencies and emissions which conform to Indian emission standards.

Emission reduction potentials of improved cookstoves and their issues in adoption: An Indian outlook.

Biomass as a fuel for cooking is a common practice in rural India, and about 700 million people use traditional stoves to meet their energy demand. However, the thermal and the combustion efficiencies of these stoves are very low, leading to an inefficient use of biomass, and also, resulting in significant indoor air pollution. Research development has however led to the development of some improved stoves viz., natural draft and forced draft for both domestic as well as large scale cooking applications and government is trying to promote them. Forced draft stoves using processed biomass fuels (pellets) have received more prominence due to their superior performance, however, higher initial cost and limited fuel distribution networks have remained the key challenges. Improved natural draft stoves too have gained attention for being relatively inexpensive, and they are more likely to hit the rural households. In this paper, we have examined the environmental benefits obtained by the use of improved stoves for two important scenarios: traditional stoves are replaced by (i)improved natural draft stoves and, (ii) by improved natural draft as well as forced draft stoves. In the best case scenario (case ii), i.e., by shifting 111 million households who currently use wood to the forced draft stoves, and another 45 million households who are dependent on dung cake and agro residues to the improved natural draft stoves, the emission reduction that can be achieved are as follows: particulate matter (PM) 875 kT, black carbon (BC) 229 kT, organic carbon (OC) 525 kT, methane (CH4)1178 kT and non methane hydrocarbon (NMHC) of 564 kT. With the promotion of only natural draft improved stoves, the total reductions would be ∼12% lower than the combinational promotion. The CO2 equivalent reduction is estimated to be ∼70-80 MT per year.