Pelletization of fine coals. Technical progress report, March 1, 1992--May 31, 1992

The first step consisted of producing a batch of seed pellets (in the size range {minus}4.75+4.00 mm) by pelletizing of 200 g of ground coal with desired additives (surface active agents and binders) and moisture content for 800 revolutions. The seed pellets are obtained by sieving the output from the batch drum. The second step involved the production of finished size pellets by layering the seed pellets with stepwise addition of moist feed which is again produced with desired additives and moisture content. Specifically, 25 g of the {minus}4.75+4.00 mm seed pellets are placed in the drum and 20 g of moist fluffy feed is added every 80 revolutions for five times. After 400 revolutions the pellets are sieved on the 4.75 mm screen and the screen undersize which corresponds to new seeds generated during the layering cycles is discarded. Now, 30 g of moist fluffy feed is added every 50 revolutions for five more cycles. These layered pellets are sieved again and the {minus}9.5+8.00 mm pellets. Coal agglomerates produced by the above described technique are nice and spherical. With our past experience with iron ore pelletization we learnt that as long as sufficient fluffy feed is available for themore » consumption by the seed pellets, they generally grow by forming layers consuming the feed rather than grow by coalescence. This is found to be true in the case of coal also. Growth by coalescence of coal pellets is found to yield raspberry type uneven agglomerates. After ascertaining the possibility of producing nice spherical pellets, several experiments have been conducted to develop the above standard procedure for making pellets in a reproducible way and testing them for their quality.« less