化工程序设计仪器装置设计与选择.PPT

化工程序設計儀器裝置設計與選擇 台大化工系 陳延平 化工程序裝置的設計與選擇 選擇可解決問題之技術與設備 經濟上可行及省錢 合乎環保要求 易於操作及合乎安全規範 易於購置且有可信的供應廠商 Examples and solutions Removal of acid gases (CO2 and H2S) May choose a gas scrubber What is the proper solvent? Henry’s law is applicable for solvent selection Examples and solutions Consider a large-size compressor Should we used a steam turbine-driven or motor-driven compressor? The answer is a steam turbine-driven compressor The reason is for lower noise pollution Rules of Thumb（經驗規則） Fans are used to raise pressure about 3%. Blowers raise to less than 40 psig. Compressors to higher pressures. Heat transfer coefficients (Btu/(hr)(sqft)(F) for estimating purposes: water to liquid, 150. liquid to liquid, 50. liquid to gas, 5. condenser, 150. reboiler, 200. Rules of Thumb Batch reactions are conducted in stirred tanks for small daily production rates. Tubular reactors are suitable to high production rates at short residence times and when substantial heat transfer is needed. Equipments for Transportation To transport materials from one equipment to the next To supply energy in the form of pressure Select a device for air flow rate of 103dm3/s and a pressure raise of 1000 kPa? Check the previous Figure for the general selection purpose A centrifugal compressor, or a 2- or 3-stage reciprocating compressor is appropriate Selection of a pump-First consideration is the viscosity Selection of a pump for a fluid with viscosity of 100 mPa s, flow rate of 20 L/s (or 0.02 m3/s), and a head of 30 m From the above Figure, a single-stage centrifugal radial flow pump is appropriate The Net Positive Suction Head (NPSH) The NPSH is the pressure or head, required at the inlet or suction flange in excess of the vapor pressure of the liquid at the temperature of the pumping condition. NPSH = (The pressure supplied at the flange) – (The vapor pressure of the liquid at the pumping temperature) Example and solution For pumping a liquid, we have the following conditions Vapor pres