Potassium hydroxide is a strong base, which can be widely used in electroplating or chemical raw materials. However, when we use it, we will find that the color of some products turns black. This is because there are some mistakes in the process of production. Let's have a detailed understanding of the reasons why the color of products turns black.

1、開(kāi)車(chē)投料后需要使用氮?dú)饷芊庠O(shè)備

1. Nitrogen sealing equipment is needed after start-up

當(dāng)設(shè)備處于微正壓狀態(tài)的時(shí)候，可以有效的避免空氣進(jìn)入到系統(tǒng)當(dāng)中。所以制作的時(shí)候開(kāi)車(chē)投料后用氮?dú)饷芊庠O(shè)備，保持通入的氮?dú)馓幯b置始終處于高溫強(qiáng)堿狀態(tài)，氧氣進(jìn)入從而會(huì)加劇鎳材腐蝕，進(jìn)而增加其中的鎳含量，從而導(dǎo)致顏色發(fā)黑。

When the equipment is in micro positive pressure state, it can effectively avoid air entering the system. Therefore, during the production, the equipment is sealed with nitrogen after feeding, and the device at the nitrogen inlet is always in a high temperature and strong alkali state. Oxygen entering will aggravate the corrosion of nickel material, and then increase the nickel content, resulting in black color.

2、能力控制

2. Ability control

能力需要控制在額定產(chǎn)量的60%~100%的范圍內(nèi)。在蒸發(fā)器中，如果進(jìn)料量太小，蒸發(fā)器中液膜就會(huì)因?yàn)樘∫灾聰嗔?，從而出現(xiàn)干壁區(qū)，這樣就會(huì)使管子承受更大的的熱應(yīng)力，從而加劇應(yīng)力腐蝕。當(dāng)液體的進(jìn)料量太大時(shí)，液體就無(wú)法正常成膜或者膜太厚，在升溫過(guò)程中，液體經(jīng)常不能得以充分的熱量傳遞，從而達(dá)不到沸騰所需要的溫度，因此不能全部的進(jìn)行蒸發(fā)，就會(huì)導(dǎo)致濃縮過(guò)程不能很好地進(jìn)行，甚會(huì)發(fā)生無(wú)法進(jìn)行的情況。流量太大或太小都會(huì)損壞設(shè)備，腐蝕鎳材，這樣就會(huì)增加氫氧化鉀中的鎳含量，使其發(fā)黑。

The capacity should be controlled in the range of 60% ~ 100% of the rated output. In the evaporator, if the feed rate is too small, the liquid film in the evaporator will be too thin to break, resulting in dry wall area, which will make the pipe bear greater thermal stress, thus aggravating stress corrosion. When the liquid feed volume is too large, the liquid can not form a normal film or the film is too thick. In the heating process, the liquid often can not be fully heat transfer, so it can not reach the temperature required for boiling, so it can not be fully evaporated, which will lead to the concentration process can not be well carried out, or even can not be carried out. If the flow rate is too large or too small, the equipment will be damaged and the nickel material will be corroded, which will increase the nickel content in potassium hydroxide and make it black.

3、減少開(kāi)、停車(chē)次數(shù)

3. Reduce the times of starting and stopping

盡量減少設(shè)備開(kāi)停車(chē)的次數(shù)，因?yàn)槊恳淮伍_(kāi)車(chē)，進(jìn)料堿液都會(huì)沖掉一層鎳材表面起保護(hù)作用的氧化鎳層，然后繼續(xù)沖刷腐蝕下層鎳材，所以開(kāi)車(chē)過(guò)程中難免產(chǎn)生黑堿?？梢赃M(jìn)行延長(zhǎng)蒸氣吹掃系統(tǒng)的時(shí)間等措施，盡量的降低開(kāi)車(chē)黑堿量。

Try to reduce the number of start-up and shut-down of the equipment, because each start-up, the feed alkali will wash away a layer of nickel oxide layer which plays a protective role on the surface of nickel material, and then continue to wash and corrode the lower layer of nickel material, so it is inevitable to produce black alkali in the process of start-up. Measures such as extending the time of steam purging system can be taken to reduce the amount of black alkali during start-up as much as possible.

4、開(kāi)車(chē)前用蒸氣吹掃設(shè)備

4. Purge the equipment with steam before start-up

開(kāi)車(chē)前用蒸氣吹掃干凈系統(tǒng)，保證有足夠的壓力和吹掃時(shí)間。吹掃既可以預(yù)熱設(shè)備，降低投料時(shí)的熱應(yīng)力，又能在吹掃過(guò)程中把管路中的殘留堿吹掃干凈；還可以通過(guò)吹掃把系統(tǒng)中的空氣排出，盡量減少氧氣含量；同時(shí)可以減少投料時(shí)對(duì)鎳材設(shè)備的沖刷和腐蝕，降低其中的鎳含量，防止發(fā)黑。

Clean the system with steam before start-up to ensure sufficient pressure and purging time. Purging can not only preheat the equipment and reduce the thermal stress during feeding, but also purge the residual alkali in the pipeline during purging; it can also exhaust the air in the system through purging to reduce the oxygen content as far as possible; at the same time, it can reduce the erosion and corrosion of nickel equipment during feeding, reduce the nickel content and prevent blackening.

上面介紹的就是氫氧化鉀在制作時(shí)顏色發(fā)黑的原因，主要是因?yàn)橹谱鲿r(shí)候的產(chǎn)量的控制不好，以及設(shè)備可以沒(méi)有清理干凈，導(dǎo)致的產(chǎn)品在制作時(shí)顏色發(fā)黑。

The above is the reason why the color of potassium hydroxide turns black when it is made. The main reason is that the output of potassium hydroxide is not well controlled when it is made, and the equipment can not be cleaned up, resulting in the color of the product turns black when it is made.