Combustion and gasification of coal and straw under pressurized conditions. Task 1: Preparation and characterization of fuels

The work in the present report is part of an experimental programme regarding pressurized combustion and gasification of coal and biomass. The report gives a description of the preparation and characterization of the fuels used in the experimental work where a Cerrejon coal and a wheat straw were tested in a pressurized thermogravimetric analyzer and pressurized entrained flow reactor in order to determine kinetic parameters and burnout times under oxidizing and reducing conditions.

Cerrejon coal and wheat straw were produced in fine and coarse size fractions. The coarse size straw fractions comprised nodes, internode pieces and whole grains. The fine straw fraction consisted of pulverized straw. The fine coal fraction consisted of 45-90 #mu#m particles and the coarse fraction of 150-180 #mu#m particles.

Both fuels were subjected to proximate and ultimate analyses, where it was seen that the carbon content was much higher in coal than in straw and grains. As a consequence the higher heating value of straw and grain (water-free basis) was only about two-thirds of the higher heating value of coal. Also a great difference in the content of volatiles were observed; 35.7 % in coal, 77.3 % in straw and 83.2 % in grain.

The most significant differences between coal and straw ash were noted in the content of Al, Ca, K and Cl. The content of Ca, K and Cl was much higher in straw than in coal. The high content of potassium in straw ash explains the low fusion temperatures found for straw ash compared to coal ash. The grain ash was characterized by a low content of Si and high content of Mg, K and P. (au).