The influence of calcium lignosulphonate addition on non-isothermal pyrolysis and gasification of demineralised bituminous coal fines

Abstract

• Coal fines were demineralised using acid de-ashing treatment. • CaLS added to the coal fines and demineralised coal in different proportion showed an increase in compressive strength. • CaLS blended samples showed higher reactivity when compared to the demineralised coal and coal fines. • 5% CaLS addition did not influence coal gasification rate significantly. • An increase in CaLS blends correlates with an increase in reactivities. Amorphous calcium lignosulphonate (CaLS), a by-product of the paper industry, was evaluated as an adhesive to bind demineralised bituminous coal fines in various weight percentage ratios. Sequential acid (HCl, HF, HCl) leaching was used to reduce mineral matter content in the coal fines. The pyrolysis and gasification of the samples were investigated in laboratory-scale experiments to determine the effect of the CaLS addition on the pyrolysis and gasification reactivities. Coal-CaLS blends consisting of 5, 10, and 15% calcium lignosulphonate were prepared, compressed into pellets, and characterised using proximate, X-ray diffraction, and X-ray fluorescence analyses. An increase in binder concentration increases the mechanical strength of the pellets due to the increased interparticle contact area. The relative coal gasification reaction reactivity (1/T max and 0.5/T 50 ), which was determined from the derivative thermogravimetry curves, increases with CaLS addition. The experimental results revealed that these wastes (coal fines and calcium lignosulphonate) could be utilised in thermochemical processes. Utilising these wastes will reduce the environmentally unfriendly volumes of amorphous calcium lignosulphonate and coal fines particles.