Abstract: An apparatus for carbonizing an agricultural product utilizes a horizontally rotatable cylindrical vessel in which a pair of helical barriers are used to cause hot gases and combustion air to turbulate in a vortex about a central support member to cause various volatile constituents and organic matter of the agricultural product to evolve leaving the carbon constituents remaining on the skeletal silica through controlled burning at a temperature below the fusion point of the skeletal silica of the agricultural product.

Abstract: A process for treating an agricultural product having a high silica content utilizes the steps of supplying hot gases and combustion air to a combustion zone, dispersing the agricultural product in the hot gases and combustion air for controlled burning thereof and then arresting the combustion process after evolution of the volatile constituents and organic matter and prior to oxidation of the carbon constituents remaining in the agricultural product.