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A unique pressurized spray test facility for optimization of black liquor gasification
2006 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The work presented in this report was done in order to design a pressurized test facility for droplet analysis with a laser measurement technique, Phase Doppler Anemometry. The test facility was a development work within Chemrec's pressurized black liquor gasification (BLG) project. BLG is a complex process where black liquor is atomized and sprayed into a reactor and gasified using pure oxygen. In the process it is crucial that all organic material is consumed to produce combustible gases using three stages of conversion: drying, pyrolysis and char gasification. In the end of the conversion, only an inorganic smelt is supposed to remain (ideally). For the gasification process, it is important to be fully aware of the spray characteristics created by the nozzle that yields an ideal conversion. Therefore a pressurized spray test facility with optical access windows for measurements was developed. Parameters that are important and interesting to study are droplet size and their velocity. The purpose of the facility is to gain quantitative information to optimize the black liquor gasification (BLG) process. For measuring droplets, a non-intrusive laser measurements system is used called Phase Doppler Anemometry (PDA). PDA is the most advantageous technique for measuring droplet velocity and size distribution. The first stage in the work of developing this spray test facility was a brief feasibility study of other pressurized spray testing facilities using PDA, to get information of different concepts. Concepts and configurations of the different parts for the pressurized test facility have been analyzed and investigated with a variety of engineering tools. Because measurements with PDA are very depending on certain receiving angles a deep review of PDA was performed, all to achieve correct placement of the transmitting and receiving optical access windows. The final design resulted in a standing pressure vessel with height 5600 mm and a diameter of 500 mm. The test facility was tested and is approved for a working pressure of 15 bar. To prevent corrosion due to the future application of black liquor atomization, it was made of stainless steel (SS2343). Four optical access side ports were placed approximately 500 mm from the top of the vessel. The side port for the transmitter probe is located at 0 degrees and the three receiving side ports at 106.3, 120 and 270 degrees. These angles were chosen to fulfill the requirements and demands essential for PDA. Simulations using CFD have contributed with useful information for the flow behavior inside the vessel and how droplets are affected by it. These simulations gave information about the flow near the optical access side ports and the necessity of optical clearance. The simulations show that recirculated flow carries droplets from the spray that reaches the glass windows, which is not preferable as it may interfere during laser measurements. Initial test runs and experiments confirm the results obtained from the simulations. The outcome of this study became a development of a purging air wall to prevent droplets reaching the glass windows. Fine polished fused quartz glass, especially suitable for laser measurements is used for the glass windows. These glasses are free from inclusions and are distinguished from other glasses by good transmission in UV- and the visible spectral range. A solid mechanic calculation of the glass specimen was performed to determine the thickness of the glass in order to withstand a maximum pressure of 15 bar. An evacuation port was placed in the middle of the vessel to perform evacuation of gas. The evacuation is used for both atmospheric and pressurized conditions. During pressurized runs, a flange lid with a pressure control valve can be attached to this side port to regulate the pressure. Connections for adding a fluid level gauge were placed on the vessel side. On the top of the vessel a unique designed spray lance traversing system were attached on a flange lid. With this arrangement the spray can be rotated and traversed up and down through the top lid. This device enables measurements in a large part of the spray. The test facility has been installed and initial test runs performed. Measuring and optimization of the facility will continue. When optimized, the results of the measurements from this facility will be applied in the BLG project.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Sprays, test facility, droplets, optical access, fluid mechanics, purged windows, spray traverse, black, liquor, gasification, atomization, phase doppler anemometry, PDA, CFD
Keyword [sv]
URN: urn:nbn:se:ltu:diva-44959ISRN: LTU-EX--06/091--SELocal ID: 2b39630a-7246-4a38-8d6c-9dbb2e1b468eOAI: diva2:1018238
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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