Section two Working Principle and Technical Specification of Main Equipment
I. Seawater Booster Pump:
The seawater booster pump selects Dalian Acid-resistant Pump, LH vertical type single-stage and single-suction submergible pump, 3 sets. The model: LH50—400; the flow rate: 34m3/h; the pressure: 0.35 MPa; the axial length: 4.5m; the axle, axle sleeve and impeller of the seawater booster pump are all made of 316L stainless steel form abroad. The bearing of vertical long-axle submerged pump is an inlet one; the motor speed is 1450r/min.
II．Automatic Backwashing Filter:
1．Working Principle:
Automatic backwashing filter utilizes the pressure difference of system to implement backwashing without any influence on flowing of seawater and no special cleaning fluid is required during the cleaning process. In the normal operation, crude seawater runs into sieve through the inlet of filter, all impurities with diameter larger than 0.5mm will be retained on the sieve. This process carries on until the impurities accumulate to a certain degree, which causes the increase of pressure difference, when the pressure differential controller achieves the preset value（0.035Mpa）, automatic backwashing starts up. Sliding seal plate connected to the backwashing outlet will clean each part of sieve effectively. The internal pressure in the filter shell is higher than that of backwashing outlet pipe, thus some seawater flows in an opposite direction through sieve and cleans all accumulated impurities effectively, discharging them into trench through the blowdown valve.
The whole process is carried out by the differential pressure controller automatically. After all sieves of filters were cleaned, the automatic backwash cycle stops, and filters restore to the normal mode till next action of the pressure controller takes place, washing repeatedly.
2．Characteristics of Equipment:
- It is unnecessary to shut down during backwashing and the water consumption for backwashing is quite low.
Backwashing adopts small and light motor with low power for convenience of maintenance.
● The lid of filter shall be easily disassembled for maintenance of the sieve,
● Unique structure of sieve prevents from being blocked by impurities with strong anti-mechanical wear and anti-scour abilities.
● The possibility of damage is eliminated due to the separation of sieve and backwashing components.
● The import 316L stainless steel has strong anti-corrosion ability to seawater and longer service life.
● The low inertia of backwashing components ensures the minimum power consumption.
● The blowdown valve adopts an electric ball valve, which opens automatically during backwashing and closes after it.
3．Equipment Specification:
ZHG56-LA Automatic Backwashing Filter, water treatment capacity is 68m3/h.
III．Sodium Hypochlorite Generator:
1．Working Principle:
The seawater that passes through the electrolytic cell shall be electrolyzed at both anode and cathode with chemical reactions as below:
Anodic reaction： 2Cl—2e→Cl2 （1）
Cathodic reaction： 2H2O+2e→2OH-+H2↑ （2）
Reaction between electrodes of electrolytic cell: Cl2+ 2NaOH→2NaClO+H2↑ （3）
Hypochlorous acid and hypochlorous acid ion are all called effective chlorine, and prevention of sea biological defile is realized by using effective chlorine which is generated from electrolyzing seawater.
2．Characteristics of Equipment:
Lid of electrolytic cell: the lid is made of UV-resistant organic glass which is transparent so that the operator is able to directly observe chemical reactions in the cell through the lit during operation which is helpful for operators to judge and master maintenance of electrolytic cell and time of acid rinsing well.
Shell of electrolytic cell: the shell is made of PVC with perfect corrosion resistance to the sodium hypochlorite. This material possesses features of high strength, anti-aging and corrosion resistance compared with other materials with higher safety and stability, eliminating the leakage of liquid.
第二節(jié) 汽、水分析方法
一． pH的測(cè)定（pH電極法）
1 ． 概要
當(dāng)氫離子選擇性電極—pH電級(jí)與甘汞參比電極同時(shí)浸入水溶液后，即組成測(cè)量電池。其中pH電極的電位隨溶液中氫離子的活度而變化。用一臺(tái)高輸入阻抗的毫伏計(jì)測(cè)量，即可獲得同水溶液中氫離子活度相對(duì)應(yīng)的電極電位，以pH值表示。即
pH = -lga[H+]
2 ． 測(cè)定
（１）儀器校正：儀器開(kāi)啟半小時(shí)后，按儀器說(shuō)明書(shū)的規(guī)定，進(jìn)行調(diào)零、溫度補(bǔ)償以及滿刻度校正等手續(xù)。
（２）pH定位：定位用的標(biāo)準(zhǔn)緩沖溶液應(yīng)選用一種其pH值與被測(cè)溶液相近的。在定位前，先用蒸餾水沖洗電極及測(cè)試燒杯2次以上，然后用干凈濾紙將電極底部殘留的水滴輕輕吸干。將定位溶液倒入測(cè)試燒杯內(nèi)，浸入電極，調(diào)整儀器的零點(diǎn)、溫度補(bǔ)償及滿刻度校正。最后根據(jù)所用定位緩沖液的pH值將pH計(jì)定位。重復(fù)1~2次，直至誤差在允許范圍內(nèi)。定位溶液可保留下次再用。但如有污染或使用數(shù)次后，應(yīng)當(dāng)更換新鮮緩沖溶液。
（３）復(fù)定位：復(fù)定位就是將上述定位后的pH計(jì)對(duì)另一pH值的標(biāo)準(zhǔn)緩沖溶液進(jìn)行測(cè)定，如所測(cè)結(jié)果與復(fù)定位緩沖溶液的pH值相差±0.05pH以內(nèi)時(shí)，即可認(rèn)為儀器和電極均屬正常，可以進(jìn)行pH測(cè)定。復(fù)定位溶液的處理，應(yīng)按定位溶液的規(guī)定進(jìn)行。
（３）水樣的測(cè)定：將復(fù)定位后的電極和測(cè)試燒杯，反復(fù)用蒸餾水沖洗2次以上，再用被測(cè)水樣沖洗2次以上。然后將電極浸入被測(cè)溶液，即可讀取儀表指示的pH值。測(cè)定完畢后，應(yīng)將電極用蒸餾水反復(fù)沖洗干凈，最后將pH電極浸泡在蒸餾水中備用。
３．注釋：
（１）新電極或長(zhǎng)時(shí)間干燥保存的電極在使用前，應(yīng)將電極在蒸餾水中浸泡過(guò)夜，使其不對(duì)稱電位趨于穩(wěn)定。如有急用，則可將上述電極浸泡在0.1M鹽酸中至少1h，然后用蒸餾水反復(fù)沖洗干凈后才能使用。
（2）對(duì)污染的電極，可用蘸有四氯化碳或乙醚的棉花輕輕擦凈
電極的頭部。如發(fā)現(xiàn)敏感泡外壁有微銹，可將電極浸泡在5~10%的鹽酸中，待銹消除后再用，但絕不可浸泡在濃酸中，以防敏感薄膜嚴(yán)重脫
（3）進(jìn)行pH測(cè)定時(shí)，還必須考慮到玻璃電極的“鈉差”問(wèn)題，即被測(cè)水樣中鈉離子的濃度對(duì)氫離子測(cè)定的干擾。特別是對(duì)pH>10.5的高pH測(cè)定，必須選用優(yōu)質(zhì)的高堿pH電極，以減少“鈉差”的影響。
（4）溫度對(duì)pH值測(cè)定的準(zhǔn)確性影響較大。對(duì)于pH大于8.3的水樣，在相同的酚酞堿度下，出現(xiàn)實(shí)測(cè)pH值隨水溫升高而直線下降的現(xiàn)象。其原因是由于溫度變化，引起了眾多影響pH值的因素改變，儀器上的溫度補(bǔ)償僅能消除一個(gè)因素的影響。為了消除溫度影響，水樣可采取水浴升溫或降溫的措施，使pH的測(cè)定在25℃時(shí)進(jìn)行。當(dāng)采用記錄溫度并進(jìn)行溫度校正的方式測(cè)定堿性水的pH值時(shí)，那么實(shí)測(cè)酚酞堿度計(jì)算出的pH值與溫度校正后的pH值，兩者相差小于±0.1pH，測(cè)定的pH值才符合要求。
（5）要保證玻璃電極中的飽和KCL不能缺，如缺少應(yīng)及時(shí)加滿。