Process Heat Application Technology MVR Used in Dryness & Concentration Processes 製程熱能應用技術實例

1. Process Heat Application Technology MVR Used in Dryness & Concentration Processes 製程熱能應用技術實例 MVR應用於乾燥 & 濃縮製程 Chi-I Tuan 段紀義 Nov.1.2013

2. Energy utilization : Optimum 2. Reuse

3. Fig. Triple Effect Evaporator

4. 機械蒸氣再壓縮技術, MVR (Mechanical Vapor Recompression)

5. 機械蒸氣再壓縮技術, MVR • 機械蒸氣再壓縮(MVR)技術是開放式的改良熱泵，直接吸收製程排出低溫蒸氣，壓縮使蒸氣升溫後直接回收再利用。 • 不用冷媒，無熱交換器及膨脹閥，壓損小；壓縮機比傳統熱泵小，電力需求大幅下降。 • 這些機器在壓縮比1：1.2到1：2範圍內其體積流量較高(壓縮比π是最終壓力P2與吸入壓力P1的比值)。 • 能源效率亦用COP值判斷。

6. 機械蒸氣再壓縮技術, MVR • MVR技術一般均與真空蒸發器或蒸餾塔結合使用。 • 理論上MVR可重複利用蒸氣潛熱，理論熱能效率可超過100效蒸發器；甚至可完全停用外部鍋爐蒸氣。但因壓縮機及馬達的實際操作能源轉換限制及系統信號傳遞延遲，使熱效率無法達到此目標值(APV, 2008) • 國際能源總署(IEA, 2010)公布：封閉式傳統電力熱泵 COP值是3.0-8.0，而開放式具有MVR技術改良熱泵COP值可達到10-40。

7. 機械蒸氣再壓縮技術, MVR • The compression ratio is influenced by: • 1. The boiling point elevation of the liquid to be evaporated. Higher the boiling point rise higher is the compression ratio required. • 2. Minimum differential temperature gradient required for effective heat transfer. Indirect condensers require a minimum temperature gradient across the fluids exchanging heat. The condensers should be designed for least ΔT operation. • 3. Total system pressure drop in the piping and valves. Enough size of piping and valve selection should be done for minimum pressure drop during transfer of fluid through them.

8. (Everest Transmission, 2010)

9. 機械蒸氣再壓縮技術, MVR • Case Study: • Taking a practical installation at one of the chemical units where Mechanical Compressor is installed to compress 1800 kg/hr (1.6729 m3/kg @ 100℃) of steam. • The inlet design pressure P1 is 101.3 kPa, Vapor temperature T1 is 102ºC and the compression ratio is 1.5 ( P2 = P1 x 1.5 = 152 kPa) • Ideal Specific Input work, • Ws = (152 – 101.3) x 1.6729 = 84.8 kJ/kg. • Taking compressor overall efficiency 65% • Specific Energy input = Ws / 0.65 • Specific Energy input = 130 kJ/kg ..… (1)

10. Latent heat of evaporation of Water at 100ºC and 1 bar (as per steam tables) is 2257 kJ/kg. • It implies so by compressing the vapors through electrical input energy of 130 kJ/kg, the process is able to recover 2257 kJ/kg of energy. • Heat energy recovered on condensation: 2257 kJ/kg ...(2) • Performance Ratio = 2257 / 130 = 17.36 (COP) • This ratio of 17.36 indicates that the process of Mechanical Vapor Recompression is similar to a 17 stage evaporator, making it highly energy efficient.

11. (APV, 2008)

12. (APV, 2008)

13. (PG&E, 2007)

14. (EPCON, 2011)

15. Advantages of Mechanical Vapor Compression (Everest Transmission, 2010): 1. Low specific energy consumption 2. Higher Performance co-efficient 3. Gentle evaporation of the product due to low temperature differences 4. Reduced load on cooling towers since no residual vapor 5. Simplicity of process, operation & maintenance.

16. MVR應用範圍 蒸發濃縮 / 蒸發結晶 / 低溫蒸發(ZNTECH, 2013) • 飲料工業(蔬/果菜汁、牛奶、乳清、糖溶液的蒸發濃縮) • 食品及添加劑工業(牛/雞肉汁、蛋粉、麥芽糊精、檸檬酸、味精、大豆、蛋白質乳液的蒸發濃縮) • 製藥及生物工程(中藥、維生素、氨基酸等) • 化學工業(蒸發濃縮、結晶、提純) • 廢水處理(造紙廢液、食品廢液、含鹽廢水、含重金屬廢水、其他有毒有害廢水) • 其他(海水淡化、空調製冷及熱、電力工業等)

17. MVR技術參數 (周，2011) • 蒸發一噸水需要耗電為23-70度電； • 可以實現蒸發溫度17- 40℃的低溫蒸發（無需冷凍水系統） (陳, 2012) • 純水(沸點提升0℃)能耗為20~30kW。 • 當物料沸點提升 5℃時，能耗為35~45kW。(約三效蒸發的18%) • 當物料沸點提升10℃時，能耗為50~60kW。 • 當物料沸點提升15℃時，能耗為65~70kW。

18. Cases Study Ⅰ for JT combining Three Effect fouling film Evaporator with Mechanical Vapor Recompression

20. MVR安裝前鍋爐蒸氣用量

21. TVR 700 (2765-727)/3 =679 2765 727

22. MVR

23. 1 mbar = 100 Pa = 0.1 kPa

24. Design data: • P1 = 199.19 mbar = 19.919 kPa = 0.199 bar = 0.197 atm • T1 = 60 ℃ = 333 K • P2 = 250.08 mbar = 25.008 kPa • T2 = 65 ℃ = 338 K • F = 1900 kg/h • PS = 32.5 kW Cal.: = P2 / P1 = 25.008 / 19.919 = 1.25 VS = n × R × T / P n = 1900 / 18 = 105.56 kgmole VS = 105.56 × 0.082 × 333 / 0.197 = 14631 m3/h = 4.06 m3/s N = ( P2 - P1 ) × VS × f = ( 25.008 - 19.919 ) × 4.06 × 1.5 = 30.99 kW

25. Amp T2 P1 P2 Fin T1 Fout

26. Actual data: • P1 = 0.13 bar = 13 kPa = 0.129 atm • T1 = 47.4 ℃ = 320.4 K • P2 = 0.17 bar = 17 kPa • T2 = 53 ℃ = 326 K • F = 1172 kg/h • A = 35.8 amp Cal.: = P2 / P1 = 17 / 13 = 1.31 VS = n × R × T / P n = 1172 / 18 = 65.11 kgmole VS = 65.11 × 0.082 × 320.4 / 0.129 = 13260.6 m3/h = 3.69 m3/s N = ( P2 - P1 ) × VS × f = ( 17 - 13 ) × 3.69 × 1.5= 22.14 kW PS = 1.732 × 440 × 35.8 × 0.8 / 1000 = 21.83 kW

27. The yearly working time is 8000 hours. 1USD=30NTD Benefit assessment

28. Cases Study Ⅱ for MVR used to recover Boiler Blow-down water (段, 2012)

29. 蒸氣鍋爐洩放水及廢熱同時回收再利用效益評估蒸氣鍋爐洩放水及廢熱同時回收再利用效益評估 圖7-1標準鍋爐洩放水系統

30. 蒸氣鍋爐洩放水及廢熱同時回收再利用效益評估蒸氣鍋爐洩放水及廢熱同時回收再利用效益評估 圖7-3使用MVR設備的鍋爐洩放水熱交換系統

31. 成本效益分析 • 淨現值法(net present value, NPV) (駱和蕭，2007)：指在未來一段時間內，考量貨幣的時間價值，將未來價值還原成現在價值；比較各期效益折現後的淨現值流入及所有成本現值流出分別加總後的差異。 • 回收期間法(payback period, PP) (徐，2002)：指各年度現金流入與回收該投資案原先所投入的現金支出進行比較，由回收期限的快慢來決定是否接受該投資案。

32. 設備投資回收效益快。 a CHP為傳統熱泵、HE為熱交換器、EV為真空蒸發器、MVR為機械蒸氣再壓縮設備

33. References: 周正全，2011, MVR的原理及應用範圍, 江蘇樂科熱力有限公司，中國 段紀義，2011，狹點結合熱泵探討工業能源再利用，學位論文，台灣 徐燕山，2002，財務管理，第六版，東華書局，台北。 陳俠，2012，單級高速離心式蒸汽壓縮機在MVR系統中的應用，浙江中能輕工機械有限公司，中國 駱尚廉、蕭代基，2007，環境經濟分析，曉園出版社，台北。 APV, 2008, Evaporator Handbook, APV, An SPX Brand, N.Y. Everest Transmission, 2010, Vapor Recompression to Recover Low Pressure Waste Steam, Everest Transmission, New Delhi, India. EPCON,2011, Falling Film MVR Evaporators, EPCON Evaporation Technology AS, Norway. IEA, Heat Pump Centre, 2010, “Heat pump performance,” International Energy Agency (IEA) Heat Pump Centre, Available at: www.heatpumpcentre. org, Accessed 22 November 2010. PGE, 2007, Performance Study of a Mechanical Vapor Recompression (MVR) Evaporation System, Pacific Gas and Electric Company, California, U.A.

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