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重 慶 理 工 大 學(xué)
文 獻(xiàn) 翻 譯
二級(jí)學(xué)院 機(jī)械學(xué)院
班 級(jí) 機(jī)械設(shè)計(jì)制造及其自動(dòng)化第二專(zhuān)業(yè)
學(xué)生姓名 謝 兵 學(xué) 號(hào) 10905020133
時(shí) 間 2013年3月16日
譯 文 要 求
1、譯文內(nèi)容必須與課題（或?qū)I(yè)）內(nèi)容相關(guān)，并需注明詳細(xì)出處。
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譯 文 評(píng) 閱
導(dǎo)師評(píng)語(yǔ)（應(yīng)根據(jù)學(xué)?！白g文要求”，對(duì)學(xué)生外文翻譯的準(zhǔn)確性、翻譯數(shù)量以及譯文的文字表述情況等作具體的評(píng)價(jià)）
指導(dǎo)教師：
年 月 日
設(shè)計(jì)程序的混凝和絮凝
對(duì)混凝攪拌罐的設(shè)計(jì)，設(shè)計(jì)師應(yīng)首先知道快速混合用于凝血和緩慢攪拌絮凝?；旌?
利用機(jī)械設(shè)備經(jīng)常進(jìn)行。圖1顯示了典型的混合葉輪。
有機(jī)械混合，可以發(fā)現(xiàn)在標(biāo)準(zhǔn)的典型設(shè)計(jì)標(biāo)準(zhǔn)在水/廢水處理教材。表1的數(shù)據(jù)，2是從metcaff與渦流污水工程和其他來(lái)源。
凝聚和絮凝攪拌罐設(shè)計(jì)的步驟是什么？“常用的設(shè)計(jì)方法的基礎(chǔ)上的速度梯度（G）的概念。基于設(shè)計(jì)者的經(jīng)驗(yàn)，他選擇的混合時(shí)間（t），G值，和一個(gè)混合葉輪?；谒x噸，G，和葉輪，設(shè)計(jì)師使用他的工程知識(shí)計(jì)算設(shè)計(jì)參數(shù)如下：
·混合罐的體積和尺寸
·理論的電力需求
·葉輪的直徑和轉(zhuǎn)速
表3示出了選擇的設(shè)計(jì)參數(shù)和作者計(jì)算出的數(shù)據(jù)。
設(shè)計(jì)流程總結(jié)如下：
假設(shè)設(shè)計(jì)案例
我現(xiàn)在就用一個(gè)假設(shè)的例子來(lái)說(shuō)明如何設(shè)計(jì)攪拌罐凝固和絮凝。南通項(xiàng)目的基礎(chǔ)上，我們有假設(shè)的情況下，流程配置：快速混合凝固后3個(gè)階段的慢組合進(jìn)行絮凝。
設(shè)計(jì)流量：Q= 5000立方米
溫度：15°C（冬季），35°C（夏季）
1． 快速混合罐凝血設(shè)計(jì)
從表1中，推薦的混合時(shí)間為20 - 60秒。我們選擇最大的混合
·計(jì)算容積：
·計(jì)算快速混合罐尺寸：
選擇一個(gè)方形的槽的深度與寬度之比為1.5。
快速混合罐的尺寸是：
寬度=1.33米;長(zhǎng)度=1.33米;深度= 2米
·計(jì)算電源要求：
速度梯度的概念中使用的設(shè)計(jì)和操作的坦克機(jī)械攪拌裝置：
其中，G =平均速度梯度（S-1）
P=功耗（W）
μ=動(dòng)態(tài)粘度（NSM-2）
V=罐容積（m3）。
重新排列上述方程，我們得到：
μ=15°時(shí) C=1.14×10-3 NSM-2，
μ=35°時(shí) C=0.76×10-3 NSM-2。
我們選擇μ在15°C，以確保在冬季提供充足的電力。
從表1，推薦G是500 - 2,500 S-1。我們選擇G值為1000 S-1。
P = mVG2 = (1.14 x 10-3 )(3.5)(1,000)2 = 4,000 W = 4 kW
假設(shè)齒輪箱的效率為90％，功率要求變得
·計(jì)算葉輪的直徑和轉(zhuǎn)速
我們選擇45°尖銳的刀片有4個(gè)葉片的渦輪。從表1中，推薦的比例葉輪直徑（D），以等效的罐直徑為0.25 - 0.4。我們選擇0.3。
葉輪的旋轉(zhuǎn)速度（n）可以從以下估計(jì)數(shù)學(xué)關(guān)系：
上面的方程適用于，如果雷諾數(shù)是在湍流的范圍內(nèi)（NR>10000）。的功率數(shù)Np是由于在圖1和水密度r在15（℃）=999kgm3。
·檢查雷諾數(shù)：
·檢查葉輪葉尖速度：
·檢查營(yíng)數(shù)：
凝固用快速混合罐的設(shè)計(jì)是完整的。選定的設(shè)計(jì)參數(shù)和計(jì)算，如在表3中示出在表4中被再現(xiàn)。
表4中設(shè)計(jì)參數(shù)，并計(jì)算混凝池。
2． 緩慢混合罐設(shè)計(jì)第1進(jìn)行絮凝
從表2中，推薦的混合時(shí)間是20 - 60分鐘。我們選擇了一個(gè)總的混合時(shí)間30分鐘。因?yàn)槲覀冇?絮凝池，每個(gè)罐將有10分鐘的混合時(shí)間。
·計(jì)算容積：
·絮凝池的尺寸計(jì)算：
選擇一個(gè)方形水箱與寬度比1.13width深度。
絮凝池的尺寸是：寬度= 3.14米，長(zhǎng)度= 3.14米，深度=3.5
·計(jì)算功率要求
從表2中，推薦使用的G是20 - 80 s-1的。我們選擇G值為80 s-1的。
假設(shè)變速箱的效率為90％，功率要求變?yōu)椋?
·計(jì)算葉輪的直徑和轉(zhuǎn)速：
我們選擇45°尖銳的刀片有4個(gè)葉片的渦輪。從表2中，推薦的比例
葉輪直徑（D），以等效的罐直徑為0.35 - 0.45。我們選擇0.3，稍
的最低值以下。
·檢查雷諾數(shù)：
·檢查葉輪葉尖速度：
·檢查營(yíng)數(shù)：
3． 緩慢混合罐設(shè)計(jì)第2進(jìn)行絮凝
從表2中，推薦的混合時(shí)間是20 - 60分鐘。我們選擇了一個(gè)總的混合時(shí)間
30分鐘。因?yàn)槲覀冇?絮凝池，每個(gè)罐將有10分鐘的混合時(shí)間。
·計(jì)算容積：
·絮凝池的尺寸計(jì)算：
選擇一個(gè)方形水箱與寬度比1.13width深度。
絮凝池的尺寸是：
寬度= 3.14米，長(zhǎng)度= 3.14米，深度=3.55米
·計(jì)算電源要求：
從表2中，推薦使用的G是20 - 80 s-1的。我們選擇G值為60 s-1的。
假設(shè)變速箱的效率為90％，功率要求變?yōu)椋?
·計(jì)算葉輪的直徑和轉(zhuǎn)速：
我們選擇45°尖銳的刀片有4個(gè)葉片的渦輪。從表2中，推薦的比例
葉輪直徑（D），以等效的罐直徑為0.35 - 0.45。我們選擇0.3，稍
的最低值以下。
·檢查雷諾數(shù)：
·檢查葉輪葉尖速度：
·檢查營(yíng)數(shù)：
4． 緩慢混合罐設(shè)計(jì)第3進(jìn)行絮凝
從表2中，推薦的混合時(shí)間是20 - 60分鐘。我們選擇了一個(gè)總的混合時(shí)間30分鐘。因?yàn)槲覀冇?絮凝池，每個(gè)罐將有10分鐘的混合時(shí)間。
·計(jì)算容積：
·絮凝池的尺寸計(jì)算：
選擇一個(gè)方形水箱與寬度比1.13width深度。
絮凝池的尺寸是：寬度= 3.14米，長(zhǎng)度= 3.14米，深度=3.55米
·計(jì)算電源要求：
從表2中，推薦使用的G是20 - 80 s-1的。我們選擇G值為40 s-1的。
假設(shè)變速箱的效率為90％，功率要求變?yōu)椋?
·計(jì)算葉輪的直徑和轉(zhuǎn)速：
我們選擇45°尖銳的刀片有4個(gè)葉片的渦輪。從表2中，推薦的比例葉輪直徑（D），以等效的罐直徑為0.35 - 0.45。我們選擇0.3，稍的最低值以下。
·檢查雷諾數(shù)：
·檢查葉輪葉尖速度：
·檢查營(yíng)數(shù)：
進(jìn)行絮凝3慢速混合罐的設(shè)計(jì)是完整的。選定的設(shè)計(jì)參數(shù)如在表3中示出計(jì)算出的被再現(xiàn)于表5-7中
表5中。設(shè)計(jì)參數(shù)選擇和絮凝池＃1計(jì)算。
表6中。設(shè)計(jì)參數(shù)選擇和計(jì)算絮凝池＃2。
表7中。選擇的設(shè)計(jì)參數(shù)，和為絮凝池＃3計(jì)算。
至于我可以告訴葉強(qiáng)和天津的設(shè)計(jì)，設(shè)計(jì)過(guò)程通過(guò)研究所沒(méi)有考慮速度梯度的概念。在本次會(huì)議在新加坡檢討南通設(shè)計(jì)，我問(wèn)葉七盎的設(shè)計(jì)是否凝血和絮凝池G值的概念的基礎(chǔ)上。葉強(qiáng)證實(shí)他知道的速度梯度的概念。但最近，葉強(qiáng)說(shuō)，有沒(méi)有文檔/計(jì)算，以證明該設(shè)計(jì)確實(shí)是基于速度梯度。
天津設(shè)計(jì)院提供的信息是基于葉強(qiáng)的個(gè)人經(jīng)驗(yàn)。葉強(qiáng)轉(zhuǎn)交了一份由設(shè)計(jì)院完成的計(jì)算，對(duì)我來(lái)說(shuō)，看到附加的文檔。但沒(méi)有提到在文檔中，它的速度梯度的設(shè)計(jì)過(guò)程似乎是反向的上述設(shè)計(jì)過(guò)程。葉輪直徑和轉(zhuǎn)速是任意選定的。這些選定的值，然后用于計(jì)算功率要求，參見(jiàn)下圖。這是顯而易見(jiàn)的，該程序是正好相反的是什么通常使用的設(shè)計(jì)師的凝聚和絮凝流程。
通過(guò)葉強(qiáng)和天津設(shè)計(jì)院設(shè)計(jì)過(guò)程在概念上不正確的。不過(guò)，這并不意味著擬建的規(guī)?；炷托跄趯?shí)踐過(guò)程將失敗。的原因是，已經(jīng)廣泛的速度梯度在文獻(xiàn)中提出了混凝，絮凝設(shè)計(jì)。因此，安全邊際巨大的。不過(guò)，葉嶈作為一個(gè)過(guò)程的設(shè)計(jì)人員應(yīng)該學(xué)習(xí)的正確方法廢水處理工藝設(shè)計(jì)。設(shè)計(jì)程序和適當(dāng)?shù)奈募?jì)算是必須的。
我決定用一個(gè)假設(shè)的例子來(lái)說(shuō)明凝固在設(shè)計(jì)所涉及的步驟絮凝過(guò)程的一個(gè)原因。我想葉期骯遵循給定的設(shè)計(jì)實(shí)例上述重新計(jì)算凝聚和絮凝的設(shè)計(jì)參數(shù)為南通項(xiàng)目并檢查設(shè)計(jì)參數(shù)是否導(dǎo)致速度梯度值的范圍內(nèi)可接受的范圍內(nèi)。
Design Procedure for Coagulation and Flocculation
To design mixing tanks for coagulation and flocculation, the first thing the designer should know is that rapid mixing is used for coagulation and slow mixing for flocculation. Mixing is often carried out by using mechanical devices. Figure 1 shows typical mixing impellers and their power numbers.
There are typical design criteria for mechanical mixing that can be found in standard text books on water/wastewater treatment. The data in Tables 1 and 2 are taken from Metcaff& Eddy Wastewater Engineering and other sources.
What are the steps involved in designing mixing tanks for coagulation and flocculation? The commonly used design approach is based on the concept of velocity gradient (G). Based on the designer’s experience, he selects a mixing time (t), a G value, and a mixing impeller. Based on the selected t, G, and impeller, the designer uses his engineering knowledge to calculate the following design parameters:
· Mixing tank volume and dimensions
· Theoretical power requirement
· Impeller diameter and rotational speed
Table 3 shows the design parameters selected and the design parameters calculated by thedesigner.
Table3. Design parameters selected and calculated by the designer.
Hypothetical Design Case
I will now use a hypothetical case to illustrate how to design mixing tanks for coagulation and flocculation. The hypothetical case is based on the Nantong project where we have the following process configuration: a rapid mix for coagulation followed by 3 stages of slow mix for flocculation.
Design flow rate: Q = 5,000 m3/day
Temperature: 15 °C (winter), 35 °C (summer)
1. Design of a rapid mix tank for coagulation
From Table 1, recommended mixing time is 20 – 60 s. We select the maximum mixing time of 60 s.
· Calculate tank volume:
· Calculate dimensions of rapid mix tank:
Select a square tank with a depth to width ratio of 1.5.
Dimensions of rapid mix tank are:
Width = 1.33 m; Length = 1.33 m; Depth = 2 m
· Calculate power requirement:
The concept of velocity gradient is used in the design and operation of tanks with mechanical mixing devices:
where G = average velocity gradient (s-1), P = power requirement (W), μ = dynamic viscosity (Nsm-2), and V = tank volume (m3). Rearranging the above equation we get:
μ at 15 °C = 1.14 x 10-3 Nsm-2, μ at 35 °C = 0.76 x 10-3 Nsm-2. We select μ at 15 °C to ensure adequate power is provided during winter.
From Table 1, recommended G is 500 – 2,500 s-1. We select a G value of 1,000 s-1.
Assuming the gearbox efficiency is 90%, the power requirement becomes:
· Calculate impeller diameter and rotational speed:
We select 45° pitched-blade turbine with 4 blades. From Table 1, the recommended ratio of impeller diameter (D) to equivalent tank diameter is 0.25 – 0.4. We select 0.3.
The rotational speed of the impeller (n) can be estimated from the following
Mathematical relationship:
The above equation applies if the Reynolds number is in the turbulent range (NR > 10,000). The power number Np is given in Figure 1 and water density r at 15 °C = 999 kgm3.
· Check Reynolds number:
· Check impeller tip speed:
· Check Camp number:
The design of a rapid mix tank for coagulation is complete. The design parameters selected and calculated as shown in Table 3 are reproduced in Table 4.
2. Design of slow mix tank #1 for flocculation
From Table 2, recommended mixing time is 20 – 60 min. We select a total mixing time of 30 min. Since we have 3 flocculation tanks, each tank will have a mixing time of 10 min.
· Calculate tank volume:
· Calculate dimensions of flocculation tank:
Select a square tank with a depth to width ratio of 1.13width.
Dimensions of flocculation tank are:
Width = 3.14 m; Length = 3.14 m; Depth = 3.55 m
· Calculate power requirement:
From Table 2, recommended G is 20 – 80 s-1. We select a G value of 80 s-1.
Assuming the gearbox efficiency is 90%, the power requirement becomes
· Calculate impeller diameter and rotational speed
We select 45° pitched-blade turbine with 4 blades. From Table 2, the recommended ratio of impeller diameter (D) to equivalent tank diameter is 0.35 – 0.45. We select 0.3, slightly below the minimum value.
· Check Reynolds number:
· Check impeller tip speed:
· Check Camp number:
3. Design of slow mix tank #2 for flocculation
From Table 2, recommended mixing time is 20 – 60 min. We select a total mixing time of 30 min. Since we have 3 flocculation tanks, each tank will have a mixing time of 10 min.
· Calculate tank volume:
· Calculate dimensions of flocculation tank:
Select a square tank with a depth to width ratio of 1.13width.
Dimensions of flocculation tank are:
Width = 3.14 m; Length = 3.14 m; Depth = 3.55 m
· Calculate power requirement:
From Table 2, recommended G is 20 – 80 s-1. We select a G value of 60 s-1.
P = mVG2 = (1.14 x 10-3 )(35)(60)2 = 144 W = 0.14 kW
Assuming the gearbox efficiency is 90%, the power requirement becomes:
· Calculate impeller diameter and rotational speed:
We select 45° pitched-blade turbine with 4 blades. From Table 2, the recommended ratio of impeller diameter (D) to equivalent tank diameter is 0.35 – 0.45. We select 0.3, slightly below the minimum value.
· Check Reynolds number:
· Check impeller tip speed:
· Check Camp number:
4. Design of slow mix tank #3 for flocculation
From Table 2, recommended mixing time is 20 – 60 min. We select a total mixing time of 30 min. Since we have 3 flocculation tanks, each tank will have a mixing time of 10 min.
· Calculate tank volume:
· Calculate dimensions of flocculation tank:
Select a square tank with a depth to width ratio of 1.13width.
Dimensions of flocculation tank are:
Width = 3.14 m; Length = 3.14 m; Depth = 3.55 m
· Calculate power requirement:
P = mVG2
From Table 2, recommended G is 20 – 80 s-1. We select a G value of 40 s-1.
P = mVG2 = (1.14 x 10-3)(35)(40)2 = 64W = 0.064 kW
Assuming the gearbox efficiency is 90%, the power requirement becomes:
· Calculate impeller diameter and rotational speed:
We select 45° pitched-blade turbine with 4 blades. From Table 2, the recommended ratio of impeller diameter (D) to equivalent tank diameter is 0.35 – 0.45. We select 0.3, slightly below the minimum value.
· Check Reynolds number:
· Check impeller tip speed:
TS =pnD =p (0.32)(1.06) = 1.1 ms-1 1.8 < TS < 2.4 ms-1 (Table 2), Not OK
· Check Camp number:
Gt = (40)(600) = 24,000 20,000 < Gt < 200,000 (Table 2), OK
The design of 3 slow mix tanks for flocculation is complete. The design parameters selected and calculated as shown in Table 3 are reproduced in Tables 5-7.
Table 5. Design parameters selected and calculated for flocculation tank #1.
As far as I can tell, the design procedure adopted by Ye Qiang and the Tianjin Design Institute did not consider the concept of velocity gradient. During our meeting in Singapore to review the Nantong design, I asked Ye Qiang whether the design of coagulation and flocculation tanks was based on the concept of G value. Ye Qiang confirmed that he was aware of the velocity gradient concept. But recently, Ye Qiang stated that there is no documentation/calculation to demonstrate that the design is indeed based on velocity gradient.
The information supplied to the Tianjin Design Institute was based on Ye Qiang’s personal experience. Ye Qiang forwarded a copy of calculations done by the Design Institute to me, see document attached. There is no mention of velocity gradient in the document and it seems that the design procedure is the reverse of the above design procedure. The impeller diameter and rotational speed are arbitrarily selected. These selected values are then used to calculate the power requirement, see diagram below. It is obvious that the procedure is the exact opposite of what is normally used by designers of coagulation and flocculation
processes.
The design procedure adopted by Ye Qiang and the Tianjin Design Institute is conceptually incorrect. But it does not mean that the proposed full-scale coagulation and flocculation processes will fail in practice. The reason is that a wide range of velocity gradient has been proposed for coagulation and flocculation design in the literature. So the safety margin is huge. Nevertheless, Ye Qiang as a process designer should learn the proper way of designing wastewater treatment processes. Proper documentation of design procedure and calculation is a must.
I decided to use a hypothetical case to illustrate the steps involved in designing coagulation and flocculation processes for a reason. I want Ye Qiang to follow the design example given above to re-calculate coagulation and flocculation design parameters for the Nantong project and to check whether the design parameters lead to velocity gradient values that fall within the acceptable range.