Chem. Pharm. Bull. 55(11) 1545—1550 (2007)

prove the dissolution property and oral bioavailability of poorly water-soluble drugs, solid dispersion methods have been extensively used and numerous approaches have been reported such as fusion, solvent evaporation, and spray-drying methods. However, these methods involve various problems. Solid dispersions prepared by fusion usually have the shortcoming of being tacky and unstable, and solvent evaporation requires a large amount of organic solvent, which leads to environmental pollution, a high cost, and health concerns. So, it is a matter of some urgency to find new methods to solve the problems which are associated with the above-mentioned methods. A pulse combustion dryer system, HYPULCON, is a newly developed drying machine using shock wave apparatus. Shock wave drying is one of the applications utilizing the power of shock waves in air. The pulse combustion dryer system has been recognized as a technology of the future since it provides an advantageous superposition of unsteady gas flow and high-intensity sound waves. Such a combination results in enhanced momentum and heat/mass transfer rates in industrial processes such as the field of drying food, inorganic and agricultural products, and heat-sensitive biomaterials such as antibiotics, vitamins, biopesticides, and the like. Figure 1 shows a schematic diagram of HYPULCON. The system is composed of a pulse combustor and an associated combustion chamber with a pulsating flow of hot gases. A tail pipe is connected to the outlet of the combustion chamber for receiving the pulsating flow of hot gases and a material introduction chamber is connected at the outlet of the tail pipe. A drying chamber is connected at the outlet of the material introduction chamber. Air for combustion and gaseous fuel are drawn into the pulse combustion chamber and form a fuel–air mixture, which is ignited by a pilot and explodes, creating hot and high pressure gases. The hot pulse combustion exhaust gases are cooled to control the temperature of the gases issuing from the outlet of the tail pipe and entering the material introduction chamber. A separate diluent air stream may be employed for contacting with material issuing from the introduction chamber and passing into the drying chamber. This combustion cycle repeats itself at a frequency of about 50 to 1000 Hz to produce consecutive high temperature shock waves. Next, the introduced material is sprayed by the atomizer with high-speed combustor exhaust gases produced by the pulse engine and is dried by the actions of shock waves. Traditional spray-drying is separate for the atomization and application of heat functions in space and time, and the heat transfer rate is lower, so the drying time is longer and the costs are higher. However, the pulse combustion dryer system can offer important advantages over traditional spraydrying such as instantaneous drying (within 1/100 s), low temperature drying (below 80 °C), high thermal efficiency (40% up to traditional spray drying), and low cost. Furthermore, products have good qualities such as superior particle Preparation and Evaluation of Ibuprofen Solid Dispersion Systems with Kollidon Particles Using a Pulse Combustion Dryer System