Advanced Dryer for High-Diffusion Rate Biomass

Biomass drying is a core unit operation at most biomass suppliers, aggregator depots, pellet mills, biorefineries, and bioproducts firms. The need to reduce energy consumption, minimize capital, and improve feedstock quality is driving a change in how biomass is milled and dried. A shift from energy-intensive hammermills and grinders to lower energy knife and rotary shear mills is reorganizing the pre-processing system to milling raw biomass and wood chips before drying when dry feedstocks are needed. This shift changes the biophysics of drying, alters the mechanical systems design requirements for dryers, and drives a need for new types of dryers optimized for small particles that are no longer diffusion limited. Prior and ongoing research at Forest Concepts found that optimal drying of wood chips in conventional dryers takes approximately 20 minutes, while optimal drying of these new small biomass particles can be accomplished in as little as 3-5 minutes, and at a lower temperature. Lower temperatures directly result in lower emissions of volatile organic compounds. Lower operating temperatures, lower emissions, and shorter residence times will lead to dryers that have lower capital and operating costs. Thus, a new class of dryers is envisioned that can rapidly dry small biomass feedstocks while reducing emissions from drying operations.This project will develop a new type of dryer designed specifically for emerging bioenergy feedstock materials, taking advantage of their high diffusion rates. The project builds upon nearly ten years of engineering research at Forest Concepts related to biomass material drying properties, optimization of existing dryer performance, and advanced model-predictive dryer controls. Two novel concepts for dryers that should achieve higher performance, lower energy consumption, and lower capital cost with small high-diffusion-rate biomass particles have been advanced to the point of plausibility, and are the subject of provisional patent applications. The SBIR Phase I effort will further refine the engineering designs, develop detailed mathematical models, and use simulation to determine the technical feasibility of the innovative dryer concepts in comparison with existing Forest Concepts models and simulations of conventional dryers. Operational scenario analyses and simulations will help estimate operational feasibility. At the end of Phase I, an optimal dryer configuration and technical specification will support Phase II development and validation testing with a prototype new-concept biomass dryer.Commercial deployment of advanced dryers will be through strategic alliances and co-branding with one or more existing biomass dryer manufacturers, most of which are located in rural communities. This business model is proving successful for other biomass pre-processing technologies and equipment developed by Forest Concepts. Current market estimates suggest that at least 34 million tons per year of high-moisture biomass is likely to be milled to final size before drying within the next ten years. At an average annual capacity of 100,000 tons per dryer per year, the prospective market size is more than 300 dryers of this type. Replacement of some existing dryers and application to other biomaterial feedstocks is likely to increase the revenue potential to more than $300 million as the market matures. Additional jobs and revenues will accrue from parts and servicing of systems. Firms installing low-energy comminution systems followed by advanced dryers are likely to reduce their energy consumption by up to 30% for preprocessing operations.