All projects

  • experimental
  • combustion

Steam-Catalytic Downdraft Gasification

M.Tech thesis — steam and catalyst effects on lignite gasification in a pilot-scale downdraft gasifier

9 images · 3 min read

Explore in StudioJump to gallery
Steam-Catalytic Downdraft Gasification

datasheet // gasification

images
9
videos
0
formats
png
text
475 words · 3 min read
studio
/molecules?preset=12
source
previous site
topics
  • headline ×3
  • rigor ×3
  • experiment ×3

Problem

Steam gasification of low-rank lignite coal, with and without a catalyst, was studied to understand how steam-to-biomass ratio (SBR) and a magnesium-carbonate catalyst affect syngas quality — but the resulting hydrogen yield behaved in a way no simple model predicted.

Approach

A pilot-scale downdraft fixed-bed gasifier (525 mm ID, 2.165 m tall, mild steel) was instrumented with four K-type thermocouples across the drying/pyrolysis/combustion/reduction zones and a gas chromatograph for H2, CO, CO2, CH4, N2. Fourteen runs spanned seven steam-to-biomass ratios (0–0.47 kg/kg) with and without a 7 wt% MgCO3 catalyst.

Results

Published, Upadhyay et al. (2020), Upadhyay et al. (2019), Sakhiya et al. (2019), Upadhyay et al. (2018).

The catalyst raised hydrogen yield from 24.1–32.6% to 23.2–34.7%, cold-gas efficiency from 62.2–75.2% to 68.1–86.9%, and lower heating value from 4.48–5.19 to 4.67–6.65 MJ/Nm3. The headline finding was a non-monotonic hydrogen response: with the catalyst, H2 climbed to a 34.7% peak around SBR ≈ 0.26 and then collapsed to 23.2% by SBR ≈ 0.47 — falling below the no-catalyst case — moving in lockstep with cold-gas efficiency and heating value.

A later re-analysis (2026) found the mechanism: combustion-zone temperature is itself non-monotonic across the same SBR sweep, and hydrogen yield tracks that temperature (Pearson r = 0.80 pooled, r = 0.96 in the catalytic case) far more closely than it tracks SBR directly (r = 0.10). This re-analysis is ongoing exploratory work, reported here qualitatively; the original 2018 experimental results and their equilibrium-model comparison are the validated, published record.

Validation

Mass-balance closure between 0.920 and 0.995 across all fourteen runs.

My contribution

Experimental design, rig operation, and primary analysis, under the supervision of Prof. D. S. Upadhyay and Prof. R. N. Patel at Nirma University. Awarded the ISTE National Award for Best M.Tech Thesis 2018 (First Prize).

Publications

  • Upadhyay, D. S.; Panchal, Krunal R.; Sakhiya, A. K. V.; Patel, R. N. (2020). Air-Steam gasification of lignite in a fixed bed gasifier: Influence of steam to lignite ratio on performance of downdraft gasifier. Energy 211, 118187. doi:10.1016/j.energy.2020.118187
  • Upadhyay, D. S.; Sakhiya, A. K.; Panchal, Krunal; Patel, A. H.; Patel, R. N. (2019). Effect of equivalence ratio on the performance of the downdraft gasifier – An experimental and modelling approach. Energy 168, 833–846. doi:10.1016/j.energy.2018.11.133
  • Sakhiya, A. K.; Chaturvedi, A.; Barasara, V.; Panchal, Krunal; Upadhyay, D. S.; Patel, R. N. (2019). Elemental and heat loss analysis of different feedstock in downdraft gasifier. Journal of Energy and Environmental Sustainability 7, 10–16. doi:10.47469/jees.2019.v07.100070
  • Upadhyay, D. S.; Sakhiya, A. K. V.; Panchal, Krunal R.; Patel, R. N. (2018). Thermodynamic analysis of lignite gasification in the downdraft gasifier. Journal of Energy and Environmental Sustainability 5, 58–64. doi:10.47469/jees.2018.v05.100058

Where this is going

A rare downdraft-gasification dataset where the “obvious” steam-ratio-controls-hydrogen story turns out to be incomplete — and a reminder that a null or reversing trend is often more informative than a monotonic one.

H2 yield vs steam-to-biomass ratio (non-monotonic finding)Hydrogen yield (vol%, dry basis) vs. steam-to-biomass ratio, with and without the MgCO3 catalyst — the catalytic curve climbs to a peak around SBR~0.26 and then collapses by SBR~0.47, falling below the no-catalyst case. This non-monotonic shape is the thesis's headline experimental finding. Explain Thermal and process engineering
Cold-gas efficiency vs steam-to-biomass ratioCold-gas efficiency vs. steam-to-biomass ratio, catalytic and non-catalytic — moves in lockstep with the hydrogen-yield curve, rising then falling at the same steam ratio, reinforcing that both are driven by the same underlying mechanism. Explain Thermal and process engineering
Mass-balance Sankey diagramA Sankey diagram tracing feedstock mass through the gasifier into product gas, tar, char and losses — the visual account behind the reported 0.920-0.995 mass-balance closure across all 14 runs. Explain Thermal and process engineering
Operating map across all 14 runsAll fourteen experimental runs (seven steam ratios x two catalyst conditions) plotted on one operating map — the complete design-of-experiments coverage behind every other result in this project. Explain Thermal and process engineering
Combustion-zone temperature explains the H2 non-monotonicityCombustion-zone temperature vs. steam-to-biomass ratio, from a 2026 re-analysis — also non-monotonic, and it correlates with hydrogen yield (Pearson r=0.80 pooled, r=0.96 catalytic) far more strongly than steam ratio does directly (r=0.10). This is the mechanism behind the headline finding, not just a restatement of it. Explain Thermal and process engineering
Equilibrium-model vs measured parityPredicted (thermodynamic equilibrium model) vs. measured product-gas composition — points off the diagonal show exactly where a simple equilibrium assumption fails to explain the real gasifier behavior, motivating the deeper kinetic re-analysis. Explain Thermal and process engineering
Producer-gas flame from the rigThe producer-gas flame at the rig's outlet during an experimental run — direct visual evidence the gasifier was producing combustible syngas, not just a numerical result. Explain Experiments and measurement
Downdraft gasifier rig, campaign runThe pilot-scale downdraft fixed-bed gasifier rig (525mm ID, 2.165m tall) during a data-collection campaign in May 2018. Explain Experiments and measurement
Gas chromatography setupThe gas chromatography instrument used to measure product-gas composition (H2, CO, CO2, CH4, N2) for every run in the experimental campaign. Experiments and measurement