(1)鍋爐化學(xué)清洗酸洗劑
(1) Acid cleaning agent for chemical cleaning of boiler
檸檬酸酸洗是在鍋爐大型化，鹽酸酸洗引起奧氏體(不銹)鋼應(yīng)力腐蝕破裂的情況下發(fā)展起來的二種酸洗劑。由于檸檬酸不含氯離子，不會(huì)引起奧氏體的應(yīng)力腐蝕破裂。所以適用于結(jié)構(gòu)復(fù)雜和系統(tǒng)很復(fù)雜的高參數(shù)、大容量鍋爐，特別適用于奧氏體鋼和蛇形管的清洗。清洗時(shí)，清洗液濃度一般應(yīng)控制在3％～4％之間，溫度為90～98％，pH值在3．5～4．0之間，清洗流速為O．3～2．Om／s，清洗時(shí)問控制在3～5h。檸檬酸清洗存在的問題為檸檬酸廢液處理較復(fù)雜，它無溶解硅酸鹽垢的能力，機(jī)組啟動(dòng)時(shí)還應(yīng)有洗硅措施，藥品昂貴，操作不當(dāng)時(shí)還會(huì)產(chǎn)生檸檬酸鐵沉淀.使用檸檬酸做 清洗劑時(shí)應(yīng)注意：
Citric acid pickling is a kind of pickling agent developed under the condition that the boiler is large-scale and hydrochloric acid pickling causes stress corrosion cracking of austenitic (stainless) steel. Because citric acid does not contain chloride ions, it will not cause stress corrosion cracking of austenite. Therefore, it is applicable to high-parameter and large-capacity boilers with complex structures and systems, especially to the cleaning of austenitic steel and coils. During cleaning, the concentration of cleaning solution should be controlled between 3% and 4%, the temperature should be 90~98%, the pH value should be 3.5~4.0, the cleaning flow rate should be 0.3~2. Om/s, and the cleaning time should be controlled between 3~5h. The problem of citric acid cleaning is that the treatment of citric acid waste liquor is complex, and it has no ability to dissolve silicate scale. When the unit is started, silicon cleaning measures should also be taken. Drugs are expensive, and iron citrate precipitation will occur when the operation is improper. When using citric acid as cleaning agent, attention should be paid to:
①在專用的溶液箱中將緩蝕劑攪拌溶解,用除鹽水溶解檸檬酸,并加氨水調(diào)整清洗液pH為3.5～4.0.用蒸汽將配制好的清洗液加熱90℃以上。
① Stir and dissolve the corrosion inhibitor in a special solution tank, dissolve the citric acid with demineralized water, and add ammonia to adjust the pH of the cleaning solution to 3.5~4.0. Heat the prepared cleaning solution to above 90 ℃ with steam.
②確認(rèn)清洗系統(tǒng)無漏泄時(shí)，用清洗泵將檸檬酸送被清洗的鍋爐中。
② When confirming that there is no leakage in the cleaning system, use the cleaning pump to send the citric acid to the cleaned boiler.
③在清洗過程中，每30min采樣化驗(yàn)一次清洗液中檸檬酸濃度、Fe2+濃度及pH值。在整個(gè)清洗過程中應(yīng)保持清洗液pH始終在3．5～4．0之間(用氨水調(diào)節(jié))。
③ During the cleaning process, the citric acid concentration, Fe2+concentration and pH value in the cleaning solution shall be sampled and tested every 30min. During the whole cleaning process, the pH of the cleaning solution should be kept between 3.5 and 4.0 (adjusted with ammonia water).
④當(dāng)酸洗既定時(shí)間后或清洗液中Fe2+含量基本穩(wěn)定后，結(jié)束酸洗。 ⑤酸洗結(jié)束后，用熱的除鹽水(90℃以上)排擠檸檬酸液并進(jìn)行沖洗。為提高沖洗效果，盡量提高沖洗流速，直到排出水pH為5～6，含鐵量小于20～30mg／L時(shí)為止。
④ When the pickling reaches the set time or the content of Fe2+in the cleaning solution is basically stable, the pickling is finished. ⑤ After pickling, use hot demineralized water (above 90 ℃) to squeeze out the citric acid solution and wash it. To improve the flushing effect, try to increase the flushing flow rate until the pH of the discharged water is 5~6 and the iron content is less than 20~30mg/L.
(2)鍋爐化學(xué)清洗漂洗劑
(2) Chemical cleaning and rinsing agent for boiler
當(dāng)用鹽酸或檸檬酸作酸洗劑時(shí)，在酸洗結(jié)束并用除鹽水(或軟化水)沖洗后，一般要再用稀檸檬酸溶液進(jìn)行一次沖洗，通常稱為漂洗，是利用檸檬酸有絡(luò)合鐵離子的能力，除去酸洗和水沖洗后殘留在清洗系統(tǒng)內(nèi)的鐵離子，以及水沖洗時(shí)可能在金屬表面產(chǎn)生的鐵銹。采用0.2％～0.4％的稀檸檬酸溶液(含有0．05％的緩蝕劑)，pH值為3．5～4．0，溫度60～90℃，時(shí)間2～3h。在漂洗中應(yīng)注意以下問題：
When hydrochloric acid or citric acid is used as pickling agent, after pickling and rinsing with demineralized water (or softened water), dilute citric acid solution is generally used for rinsing, which is usually called rinsing. It is to use the ability of citric acid to complexe iron ions to remove the iron ions left in the cleaning system after pickling and water washing, as well as the rust that may occur on the metal surface during water washing. Use 0.2%~0.4% dilute citric acid solution (containing 0.05% corrosion inhibitor), pH value 3.5~4.0, temperature 60~90 ℃, time 2~3h. Pay attention to the following problems during rinsing:
①漂洗液應(yīng)用除鹽水(或軟化水)配制。
① The rinse solution shall be prepared with demineralized water (or softened water).
②配制方法采用邊循環(huán)邊加藥的方法進(jìn)行，即先用清洗泵使漂洗水在清洗系統(tǒng)中進(jìn)行循環(huán)，并在循環(huán)的同時(shí)將水加熱60～90℃，然后連續(xù)地向漂洗水中加入已事先配制好的濃藥品，加藥順序?yàn)槠磩?、緩蝕劑，并用氨水調(diào)解pH為3．5～4．0。
② The preparation method adopts the method of adding chemicals while circulating, that is, first use the washing pump to circulate the rinsing water in the washing system, and then heat the water to 60~90 ℃ while circulating, and then continuously add the prepared concentrated drugs to the rinsing water. The dosing sequence is bleaching agent, corrosion inhibitor, and adjust the pH to 3.5~4.0 with ammonia.
③在漂洗過程中應(yīng)經(jīng)常測(cè)定漂洗液溫度及pH值。
③ In the process of rinsing, the temperature and pH value of rinsing solution should be measured frequently.
④漂洗結(jié)束后，用除鹽水(或軟化水)沖洗干凈系統(tǒng)后轉(zhuǎn)入下道工序。
④ After rinsing, rinse the system with demineralized water (or softened water) and then proceed to the next process.
