The OHD Process

OHD Reactor System

Oxidative Hydrothermal Dissolution (OHD) works by reacting macromolecular organic solids such as coal or lignocellulosic biomass (among others) with small amounts of oxygen (O2) in liquid water at elevated temperatures and pressures. This results in oxidative cleavage of reactive structures within the macromolecular structure, producing a suite of low molecular weight, water soluble organic products. Conversion is readily taken to completion in reasonable reaction times with approximately 70 to 90% recovery of the initial carbon as water soluble products that can be refined into a variety of useful low molecular weight products. OHD has been extensively tested and proven at the laboratory scale for a variety of coals spanning the entire rank range and also on a range of different types of biomass.

Coal, an enormously abundant resource, can be generally described as a macromolecular organic solid. Its structural characteristics vary with rank and maceral composition, but it can be generally described as consisting of aromatic clusters (consisting of variable numbers of aromatic rings) linked together with aliphatic and ether bridges, within which is occluded variable amounts of low molecular weight (MW) materials. In most cases coal also includes variable amounts of inorganic materials present as either discrete mineral phases or as exchanged cations. Because of its nature it cannot easily be refined and is primarily used as a solid fuel for energy production. The value of coal as a resource could be considerably increased if methods to disrupt its macromolecular structure could be developed.

Various strategies, including pyrolysis, gasification and direct liquefaction, have been attempted with the goal of breaking up the macromolecular structure of coal to produce low MW products that can be refined into various types of higher value products, including liquid fuels and chemicals. OHD is a novel and highly effective approach to achieving this goal. The fully continuous OHD reactor used to develop and refine the OHD process is illustrated in Figure 1.

Sponsored research is now being performed on specific types of both coal and biomass for commercial development using identical equipment and general methods to those described here.

Schematic of continuous OHD micro reactor system built and operated at Southern Illinois University-Carbonale.
Figure 1 Schematic of continuous OHD micro reactor system built and operated at Southern Illinois University-Carbondale.