中油高壓天然氣超音波計量之規劃與應用實務

High-Pressure Natural Gas Measured by Ultrasonic Meter

胡文富(Wen-Fu Hu)

《石油季刊》 47卷2期 (2011/06) Pp. 55-68

https://doi.org/10.30128/JP.201106.0004

摘要

國內目前燃氣電廠之天然氣使用量已超過瓦斯公司，以往燃氣電廠發電用之天然氣大都以孔流板式氣量計計量，由於孔流板式氣量計的流率範圍比(Turn Down Ratio)約為1:8，亦即當流率變化超過此範圍時，將造成計量的誤差增加，同時，其可動元件較繁雜（包含上游直管段、本體、孔板、下游直管段，以及差壓、靜壓、溫度等類比式傳送器、導管、針閥、接頭…等），任一元件些微偏差，均可能為計量誤差來源，影響交易計量之公正性。隨著時代的進步，科技技術的提昇，很多天然氣交易計量已使用性能優異的渦輪式氣量計或超音波氣量計，其精確的流率量測提昇了工業用戶對天然氣交易計量的信心。台灣目前每年天然氣的交易額已超過1,500億元，則每1.0%之氣量計器差即代表15億元，為降低計量誤差，提昇交易公平性，中油公司（以下簡稱本公司）於供應台電大潭電廠之大潭計量站首次使用超音波氣量計作交易計量，該站的經驗與其他型式氣量計比較，使用超音波氣量計優點包括：流率範圍比大、可自我診斷、無可動元件、結構簡單等。本文將就本公司燃氣電廠天然氣計量改採由超音波氣量計之規劃過程與應用實務作一論述，並將心得與建議作分享。

關鍵字

天然氣 ； 孔流板式氣量計 ； 超音波氣量計 ； 整流器 ； 絕對壓力計 ； 溫度計

並列摘要

The total consumption of major gas fired power plants have replaced gas companies as major customers of natural gas in Taiwan. The orifice meter has been used as a measure of transaction devices by major gas fired power plants across the island over the years. As the flow rate range of orifice meter (Turn Down Ratio) is about 1:8, when gas flow rate over this range, it will increasingly cause measurement error and while its moved parts are become more complicated, including upstream straight pipe, metering body, orifice plate, the downstream straight pipe, differential pressure transmitter, static pressure transmitter and temperature transmitter, catheter, needle, connector, etc., any small deviation in measurement error sources is likely to affect the measurement accuracy and fairness of trade significantly.As time goes by and modern technology advances, gas turbine meter or ultrasonic meter design have been used for natural gas transactions in the market to improve the performance of measurement. The accurate flow measurements for many industrial applications are very important. Taiwan's current natural gas annual sales amount is about NT$150 billions and the average difference of meter of the device is 1.0%. If the instrumental error is not adjusted, the differences of annual transaction will then be up to NT$1.5 billions. As CPC's Ta Tan gas station is the first one to use ultrasonic meter in natural gas trade and by comparison with other types of gas meter, ultrasonic meter has shown some advantages, such as: higher flow rate range, self-diagnosis, no moved parts, simple structure, etc. In this paper the planning process of this natural gas measurement by ultrasonic meter and the application practices on the gas fired power plant were investigated.

並列關鍵字

Nature Gas ； Orifice Meter ； Ultrasonic Meter ； Rectifier ； Absolute Pressure Gauge ； Temperature Gauge