Page 68 - Vol.44
P. 68

Tech
                                                                                                    Notes
                                                                                                    技術專文


                                                  TSMC / FACILITY PUBLISHED
           VOL.44
                                                   廠務季刊


                                                     URL.http://nfjournal/



           節水好時機-Cooling Tower液位控制自動化

           It's Good Time to Save Water! Automation of Cooling Tower Level Control




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                                                                         文│江典剛  夏瑋念  黃冠諭 │ 台南廠務處  亞太廠務處│
           摘要 / Abstract
              冷卻水塔(Cooling Tower)一直是各廠回收水(RCW)使用量最大的單元，其使用量(即蒸發量)與當下環境的溫度、濕度皆有
           關，而環境溫濕度又與季節(長期)、日夜(每天)有關，以現況Cooling tower固定液位補水之控制模式會有日間因溫度較高蒸發
           量大補水量不足需須補充工業用水(ICW)，而夜間溫度較低蒸發量小補水量過剩導致原本可回收的水因需求量不足而切往放流
           的現象，並無法隨日夜環境變化達到水資源利用之最佳化。為解決上述問題，本文提出Cooling Tower水資源管理最佳化之控制
           模式，利用分散式控制系統(DCS)既有之功能將Cooling tower液位隨蒸發量即時自動調整，夜間可將過剩之RCW蓄積於Cooling
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           tower內供給日間蒸發量較大時使用。效益評估：節水量約~80m /天，節省自來水用量與廢水排放約14,400m /年；節能部分，
           藉單台pump VFD持續追減載即可維持Basin液位，改善後於2020夏~2021春相較2019夏~2020春約降低250,438度/年(約28%)；
           操作改善部分，減少值班人員手動操作Loading與MO可能性，約減少1.25次/天手動操作，全年約減少456次手動操作。

           關鍵詞 / 冷卻水塔、回收水、工業用水、分散式控制系統

              Cooling Towers(CT) always are the most significant Reuse City Water(RCW) using unit of TSMC FABs, the amount of daily
           usage is mostly related to temperature and humidity, again the two factors are related to what the season and daytime or
           nighttime it is.
              Currently, The control mode of CT water level is to fill or stop by the fixed level setpoint, and it leads to the problem that
           when daytime RCW is short due to the significant evaporation, so RCW need to be supplied by Industrial City Water(ICW)
           to meet the demand ; but when it is nighttime, RCW is excess also due to the evaporation, and the excess water finally be
           discharged as wastewater.
              To solve this problem, this article proposed a new control mode of cooling tower water management, that is, Using the grate
           PID processor function of Distributed Control System(DCS) to make the water level of CT could be dynamically fitted to the current
           evaporation, so that saved the excess water of nighttime to meet the demand of daytime. The effectiveness is : ①Save 14,400m 3
           water per year；②Save 250,4387 KWH per year；③For work load reduction : reducing 456 times of manual operation per year.

           Keywords / Cooling Tower, Reused City Water, Industrial City Water, Distributed Control System



           1.  前言

              冷卻水塔(Cooling Tower)一直是各廠回收水(RCW)使用量                  F14P6水系統架構如 圖1所示，Cooling Tower之冷卻水
           最大的單元，其使用量(即蒸發量)與當下環境的溫度、濕度皆                      以循環方式冷卻冰機(機械系統Scope)產生之熱，利用灑水蒸
           有關，而環境溫濕度又與季節(長期)、日夜(短期)有關。蒸發                     發散熱，補充水源為RCW，當RCW不足時以ICW補充之，當
           損失往往佔冷卻水塔總耗水量的最大部分，在一般大樓約佔                        Cooling Tower水槽離子濃度過高時會排放至廢水，藉由補充
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           60至90％不等，連續運轉之廠房則普遍在90％以上 。                       新的RCW降低離子濃度。
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