蒸汽輸送系統的動態及控制分析

Dynamic and Control Analysis of Steam Distribution Systems

鄭向玹(Hsiang-Hsuan Cheng)

指導教授 ： 陳誠亮

國立臺灣大學/工學院/化學工程學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201902300

摘要

此論文目標在研究大型煉油廠的蒸汽公用系統對於可能的運作干擾的動態響應。藉由使用商業軟體DynSim，建立並模擬了全廠蒸汽公用系統。本研究之範例蒸汽公用系統主要分為4個壓力等級的蒸汽，包括超高壓蒸汽(HHS)、高壓蒸汽(HS)、中壓蒸汽(MS)和超低壓蒸汽(LLS)。鍋爐和熱回收蒸汽產生器用於產生超高壓蒸汽，然後此蒸汽通過渦輪機與去過熱器輸送給不同類別的用戶。其中渦輪機用於發電並且藉由使用超高壓蒸汽來提供驅動功率。各種渦輪機的輸出可以是高壓、中壓或超低壓蒸汽，為程序單元提供熱量。為了增進蒸汽需求和供應之間的可變平衡，成對的減壓閥也按順序地安裝於這4個壓力等級之間，並針對各個壓力等級，針對渦輪機以及減壓閥，建立常態、漸次、凌駕等蒸汽壓力控制策略。
首先在正常操作下，建立通用穩定狀態以進行後續分析，在模擬時，並監測壓力以確保不會超過安全操作的上限。論文中針對幾種重要操作異常情境來探討異常操作情況下蒸汽公用系統的動態響應與控制。針對更嚴重的情境，也就是中間渦輪機故障，並探討不同的控制器參數和設定點的操作方法的影響。藉由模擬不同的異常操作情境，這些控制架構與分析數據將有助於大幅提升大型煉油廠的蒸汽公用系統的操作效益。

關鍵字

蒸汽公用系統 ； 動態響應 ； 程序控制 ； 凌駕控制

並列摘要

This research aims at investigating the dynamic response of the steam utility supply system to some possible operational disturbances in a large refinery. By using the commercial software DynSim, a plant-wide steam utility supply system is established and simulated. The illustrative plant-wide steam supply system is mainly divided into 4 pressure levels of steam, including the high-high pressure steam (HHS), the high pressure steam (HS), the medium pressure steam (MS) and the low-low pressure steam (LLS). Some boilers and heat recover steam generators (HRSG) are used to generate HHS, and then the HHS passes through turbines and desuperheaters for delivery to different class of users. Therein, turbines are used to generate electricity and to supply driving power by using the HHS. Outputs of various turbines can be HS, MS, or LLS to supply thermal heat to process units. Paired letdown valves are also applied between these 4 steam levels in sequence to enhance the variable balance between the steam demand and supply; and for each pressure level, establish steam pressure control strategies such as normal, sequential, and override control for the turbines and letdown valves.
A general steady state is made at first under normal operation in order to execute subsequent analyses. While running the simulation, pressure is monitored to make sure not exceeding the upper limit of safety operation. Several abnormal operation scenarios are proposed to discuss the dynamic response and control structure of the steam utility. Different controller parameters and setpoints are introduced for the more severe scenarios that intermediate turbines need to be restarted. These control structure and analytical works will be helpful to significantly increase the operational benefits of steam utilities in large refineries.

並列關鍵字

Steam Utility ； Process Dynamic ； Process Control ； Override Control

參考文獻

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