Phenomena related to wall friction and lubrication of coal compaction in a cylindrical mold were investigated. It was found that the product of friction coefficient and the Janssen constant is not constant but varies with the compaction force. However, at high compaction force levels, this product becomes constant. Lubrication of the mold with calcium stearate or molybdenum disulfide dry film showed a significant increase of the axial stress transmitted to the bottom piston. Based on the compaction response diagram, coal particles can be classified as hard and brittle materials. The volume of a coal log during compaction decreases linearly with the logarithm of the compaction pressure. The ejection force with or without wall lubrication can be estimated from a simple formula derived in this paper.