Raymond® Imp™ Mill for Biomass
Pulverize wood waste and other fibrous materials
The Raymond® Imp™ Mill is a versatile and dependable high speed air-swept swing hammer impact mill designed for fine and medium grinding of soft non-metallic minerals, coals, various chemical compounds, food product and biomass.
With the cost of conventional fuels increasing, many manufacturers are exploring alternative fuels for firing kilns, boilers, dryers and furnaces either directly or from pellets. As a result, biomass sources such as wood chips, sawdust, bark and other fibrous materials are being developed as primary fuels.
Three basic systems utilizing the capabilities of the Raymond® Imp™ Mill with flash drying have been developed. These systems can pulverize sawdust, bark, wood chips, pelletized wood waste, and rice and seed hulls to fineness up to 50% passing 100 mesh (50% retained on 150 micron) with capacities up to 20 tph.
Typical arrangements for firing biomass fuels
- Direct fired system
When direct firing is required, the pulverized material is conveyed with the spent drying gas by an exhauster into a burner pipe, and then to the burning zone of the kiln or furnace. In those cases where hot drying gases from the kiln or furnace may contain abrasive materials, a dust trap is provided to reduce ware on mill parts (also available for indirect fired systems).
- Indirect fired system – fine grind
An indirect fired system using biomass fuels operates similarly. The major difference is that the fuel is carried from the mill to a storage bin for later distribution to a firing system or pelletizing process. Some spent gases from the cyclone are recirculated back to the mill for temperature control of entering hot gas. The reduced material passes through a classifier which separates the fines and returns oversize particles to the mill to be reground. Adjustable vanes on the classifier allow for a wide variety of fineness.
- Indirect fired system – coarse grind
When coarsely ground biomass material is required, an external screen is used in closed circuit with the mill in place of the double cone classifier. Properly sized product passes into product bins, and oversized particles are returned to the mill for further reduction.