We are investigating catalytic gasification of coal char using biomass-derived potassium salts. Alkali metal salts, especially those containing potassium, are excellent promoters of gasification reactions but are generally considered too expensive for commercial use. Fast-growing biomass, which contains large quantities of potassium, may prove to be an excellent source of inexpensive gasification catalyst. A series of CO2-char gasification tests were performed in a thermogravimetric analyzer (TGA) to evaluate the catalytic activity of alkali-rich biomass-derived materials. Both switchgrass char and switchgrass ash displayed catalytic activity in mixtures with coal char produced from Illinois No. 6 coal. The results obtained with switchgrass ash were especially impressive, with an almost eight-fold increase in coal char gasification rate at 895°C in a 10:90 mixture of coal char and switchgrass ash. These results give encouragement that biomass could be the source of inexpensive, coal gasification catalysts.

Catalytic effects observed during the co-gasification of coal and switchgrass

High-yield hydrogen production by catalytic gasification of coal or biomass

Gasification of a lignite char with either CO 2 or H 2 O at atmospheric pressure was studied in a lab-scale fluidized bed apparatus at different bed temperatures (775–900 °C) and gas concentrations. CO 2 concentrations in the range 20–100% and H 2 O concentrations in the range 10–70% were used in the batch experiments. The carbon conversion rate was measured by following the outlet CO and CO 2 concentrations with time. A predictive kinetic model for both CO 2 and H 2 O gasification of the lignite char was developed from the experimental results, that was able to correctly predict the evolution of carbon conversion versus time. Both gasification reactions kinetics followed a Langmuir–Hinshelwood (L–H)-type equation. The activation energy of the CO 2 gasification reaction was larger than that of steam gasification, indicating a larger reactivity of the lignite char towards H 2 O in the investigated temperature range, as expected. Interestingly, the structure-related parameters of the kinetic expressions of the two gasification reactions were the same, suggesting that CO 2 and H 2 O are likely to attack the same carbon surface sites on this char.

Fluidized bed gasification of lignite char with CO2 and H2O: A kinetic study

CFD simulation of fuel reactor for chemical looping combustion of Indian coal

https://journals.sagepub.com/doi/pdf/10.1177/014459879901700603

Gasification of Coal

A comprehensive bench-scale study to determine and compare char reactivities and properties of three lignites, a subbituminous coal, and two bituminous coals in uncatalyzed, alkali-catalyzed, and demineralized forms was carried out. The catalytic effect of laboratory-grade K 2 CO 3 and ferrous ammonium sulfate (FAS) and the natural minerals trona, limestone, and taconite on the reactivities of the chars were studied. Trona, limestone, and taconite improved gasification rates of the chars by 2-10 times over the rates of the uncatalyzed reactions. Reactivities were shown to correlate reasonably well with measured active sites

Ronald C. Timpe

Papers

Hydrogen from low-rank coals: char properties and reactivity of gasification feedstocks