An Experimental Modeling for Dense Phase Pneumatic Conveying Capability using Multiple Hole Orifice in Air Supply Line for Dry Ash
Authors:   Research Scholar, RTM Nagpur University, Nagpur & Addl. Executive Engineer, MAHAGAMS, Nagpur, India, Dharaskar P. M. , Choudhary Dr. S.K. ,   Professor, Mechanical Engineering, KDK College of Engineering, Nagpur, India, Askhedkar Dr. R. D. ,   Ex Professor Mechanical Engineering VNIT, Retd. Principal, KDK College of Engineering, Nagpur, India.
Published: September 2019

Optimization of dry ash flow is an important aspect in the field of dry ash conveying system in power plant. Material pickup and conveying to desired distance at desired rate with minimum conveying medium (air) is a primarily requirement of any pneumatic conveying dry ash system. Though it looks simple task to determine parameters of conveying medium i.e. air flow but significant challenges poses while designing air parameters at Material pickup point and to maintain to convey desired throughput to conveying distance. In today’s prevalent designs / technology for pneumatic dry ash conveying system, it uses valve as controlling device in air supply system. But such system of using valve as controlling device has certain drawbacks like a) Malfunctioning of valve due to moisture & ash accumulation leading to system failure. b) Unstable operation due to high vibration and temperature Compressed air is used for instruments control purpose as well as a conveying medium. Air is a compressible gas which makes controlling difficult when specific parameters needed at certain location depending on the ash collection rate & accordingly distribution piping layout. At such locations, we need a device i.e orifice in place of valve for the same in order to achieve the desired result. In general most of system designed for two stages 1) Air storage to maintain desired air parameters passing through system. 2) In 2nd phase of pneumatic conveying air supply lines, we require fine controlling of air parameters for air supply to multiple points / ash hoppers (108 Nos). Air required in system operation is controlled by valves in prevalent designs but due to drawbacks of valve (malfunction, high initial cost and high maintenance cost of valves), orifice is one of the most commonly used element in flow regulation because of its simple structure, construction, easy installation and reliable performance (as no moving part) the orifice is increasingly adopted in air supply lines of dry ash pneumatic conveying system. The work present experimental investigation of dry ash pneumatic conveying system using multiple hole orifice in conveying air supply line to enhance flow uniformity and mass distribution downstream of manifolds or at pickup point of material as a distributors at Koradi Thermal Power Plant and result where compare with previous data and the study is extended for different parameters like conveying pressure and fluidizing pressure mean in particle size of dry ash, orifice numbers, thickness of orifice and place of orifice mounting along with corresponding loading ratio. A new approach of modeling on similar pipe line configuration since scaling is not required, it has provided better accuracy and approximation when the result was compared with experimental data. This method of online experimentation is aimed to address the partial filling of pipe's cross section by the dune of dry ash which requires high volume conveying air, or sometimes chocking of section occurs due to large volume of dry fly ash. To handle these problems, online experimentation has proved to be a better method than test conducted on test rig setup for representation of the optimum flow conditions, especially such complex mode of dense-phase pneumatic conveying of fine powders like dry fly ash materials.