Section 127 Acids and Bases (3)

Safety production is Ji Siwei's biggest headache. Chemical plant accidents are no worse than in ordinary companies: worker casualties are not counted, equipment is damaged, and the terrible consequences of chemical leakage are even more difficult to predict. He was overwhelmed by the laid-back attitude of these former peasants towards dangerous goods -- he was given several safety education sessions and reprimanded several guys who did not follow the regulations in wearing protective clothing

A few unlucky people stood dejectedly and were scolded by him for half an hour. In terms of the climate conditions of Lingao, it is indeed torture to stand by the stove with full body protection - - work. Fiberglass trousers, rubber aprons, long-arm gloves, and tall boots are all breathless things that make you sweat profusely even after a few minutes of at the stove.

"Do you want to be like him?!" Ji Siwei took out a medical atlas - he had obtained it from a large book, and the photos in it were all photos of patients with chemical burns.

But the effect of the photo was so terrifying that it was counterproductive. Several native workers came to him and begged him that they didn't want to do the work anymore. made Ji Si retreat into a fuss.

After some pacification, wishing and hinting, he sent the labor camp to taste the intimidation of the legendary whip of Fu Youdi, and finally calmed the hearts of the people in the sulfuric acid workshop, and production was normal. Ji Siwei took out and rushed to the caustic soda workshop. Outside the workshop, there are already large and small water tanks, as well as a large amount of salt. Ice Wind is leading the way to install equipment.

"Salt, running water and tanks are available. The project is not yet finished, so let's prepare saturated salt water first. Bai Yu, who volunteered to bring students to help, said. Although he became a teacher, he was also a chemistry enthusiast.

"This salt doesn't work." Xu Yingjie shook his head, "Coarse salt!" There are too many impurities. ”

Electrolysis of salt to make caustic soda is very simple in principle, directly electrolyze saturated salt water to decompose sodium hydroxide - the so-called caustic soda, and at the same time decompose chlorine and hydrogen. However, the salt sent by Yanchang Village is unrefined coarse salt, which contains not only sodium salt, but also potassium salt, magnesium salt, sulfate and other impurities, which will affect the decomposition efficiency in production and damage the valuable electrode.

Therefore, before electrolysis, the coarse salt must first be processed and refined to remove impurities and make it a pure sodium chloride saturated solution - before it can be put into production. Modern time and space have a highly developed industrial system with a highly developed division of labor, and the caustic soda industry can fully purchase refined sodium chloride products. Here, you have to do everything yourself. The more backward and primitive the industry, the more self-supporting things there are.

Ji Siwei first did an analysis of the salt sent, and the salt in Yanchang Village was of high quality, and the sulfate components that had the greatest impact on electrolysis were very small. This was good news for him: the removal of sulfate was done with barium chloride in the industrial way - which he did not have, and barium chloride was a highly toxic chemical, and he did not want to do it even if it could be synthesized. As for the content of calcium salt and magnesium salt, it is not high, and it is very ideal industrial salt.

He asked people to pour baskets of coarse salt into the sedimentation tank, and after adding water to a saturated state, Bai Yu, who was responsible for refining the electrolyte-liquid-brought soda ash and caustic soda, and added them in proportion according to the test brine composition, so that the calcium salt and magnesium salt in it reacted with it to form calcium chloride and magnesium hydroxide and precipitate out. The above clarification - liquid - is the saturated sodium chloride solution - used for electrolysis. Because caustic soda and soda ash are added, a small amount of dilute hydrochloric acid is used for neutralization.

The electrolysis of table salt in the production is a continuous process, and saturated sodium chloride solution must be continuously replenished to the electrolyzer. Therefore, the refining of brine is carried out continuously throughout the electrolysis process.

The intermittent refining method of one cylinder by cylinder is simple, and the equipment is simple, but the labor intensity is too large and the manpower is consumed too much. Generally, the method of continuous refining is used in industry. Although Ji Siwei made it a local method, he still decided to make the production as automated as possible.

According to his own conditions, which were supplied with running water, Ji Siwei decided to use continuous operation in the salt stage during the official production. Water flows from the bottom of a specialized salt tank, passes through the salt layer inside the tank, and overflows from the upper outlet of the tank. Salt is added intermittently by hand to maintain a certain salt layer. The brine is saturated brine, which is introduced into the sedimentation tank from the salt tank and then neutralized.

In order to reduce the labor intensity, the position of the brine tank is made into a stepped shape, one higher than the other, so that the brine can be transported by using the position difference and siphon principle...... From low to high, it is the salt tank-sedimentation tank-neutralization tank. Zuihou dissolves the saturated sodium chloride that flows from the neutralization tank and then feeds it into the heating tank.

The system is simpler than industrial use and does not require any mechanical assistance. A small amount of manpower is sufficient.

"To make caustic soda, you still have to put caustic soda!" Bai Yu, who took the students to deal with the salt water, said.

Xu Yingjie said: "These are two different things. What you make is refined brine, and you can't beat the caustic soda production. ”

Bai Yu said: "Fortunately, we also brought a lot of chemical products, otherwise without them as a 'primer', wouldn't we be able to start work?" ”

"Not really." Ji Siwei said while paying attention to the reaction in the tank, "It's just a lot of damage to the electrodes." It is not impossible to engage in physical refining of sodium chloride alone. However, it is necessary to make a large investment, and it is necessary to start with the direct transformation of the salt industry equipment in Yanchang Village. ”

"The salt industry equipment in Yanchang Village has changed a lot."

"Wang Gong's renovation project is mainly aimed at improving output, and his windmill is brine and drenched to shorten the concentration time of brine." Because of business relations, Ji Siwei has been to Yanchang Village several times.

"When it comes to refining, it's definitely not possible to do without a boiler." Ji Siwei continued, "The Planning Commission originally said that it would build a refined salt plant in Bopu, and as soon as our caustic soda workshop is put into operation, this project will have to be launched. ”

"The construction of the chemical industry is high-tide-ah!" Xu Yingjie said with emotion.

"It's also the turn of the chemical industry. Think about it: pesticides, fertilizers, explosives, medicines. As soon as these four ** treasures come out, they will not dominate the world! Bai Yu was in high spirits.

"It's still far away, don't think about becoming fat in one bite." Ji Siwei said, "There are still many facilities and equipment that need to be used in the chemical industry. Practical problems in production have to be solved slowly. Let's talk about the first batch of sulfuric acid made by the sulfuric acid plant. The impurity content is very high, which can be dangerous in some chemical productions. But there are a lot of conditions that need to be met to improve purity. ”

"It's like a puzzle." After making the three acids and two alkalis, we have just found the four corners of the puzzle and see hope, but it will take a long time to really put together the complete pattern. ”

Xu Yingjie commented: "It's like someone wants to use glycerin made by saponification to mix nitroglycerin, the theory is correct, and in fact it will kill you." ”

The whole reaction precipitation process of brine should last for 24 hours. Ji Siwei took people to the lime kiln by himself. Here quicklime is already ready. Based on the data in the process manual, he measured how much chlorine would be produced in the next 72 hours of continuous production and how much slaked lime would be needed to absorb it. Weigh enough quicklime and slowly spray water on the xiangshang noodles to digest it slowly. After digestion, the workers sieve the slaked lime and transport it to the caustic soda workshop in baskets.

Ji Si asked Xu Yingjie to measure the moisture content of the slaked lime, about 3%, which is a little too high, so he asked people to pile the slaked lime in the shed and store it for a few days, and there is still some quicklime in the slaked lime, so that the moisture will continue to digest the lime, so that the moisture will drop to below the appropriate 1% after a few days.

After everything was ready, a large amount of white-color-precipitate had been deposited in the brine refining tank the next day, and the surface of the clarification-liquid-test results above was extracted, which already met the requirements of electrolysis. Bai Yu used the siphon principle to pump the clarified sodium chloride saturated solution to the heating tank, and Ji Siwei set up a firewood under the heating tank to heat the brine to 70 °C. Heating is done to remove carbon dioxide from it.

The white-colour-precipitate in the sedimentation tank is collected, the main components of which are calcium chloride and magnesium hydroxide. Both are useful chemicals that should not be easily discarded. In particular, calcium chloride can be used in pharmaceutical factories to manufacture calcium chloride injection-injection-liquid and tablets to treat various diseases caused by low calcium. It can be used as a commonly used desiccant in industry, an antifreeze in the construction industry, a refrigeration liquid for refrigeration equipment, and a deinking of waste paper...... Zuihou can also be used to order tofu.

They are separated by the difference in their solubility in water - calcium chloride is easily soluble, while magnesium hydroxide is insoluble in water. Add water to dissolve the calcium chloride and pour it out for another treatment. The insoluble part is magnesium hydroxide. Although magnesium hydroxide is not so versatile, as an alkali salt, it can replace caustic soda and lime as a neutralizer for acid-containing wastewater; used as oil additives, playing the role of anti-corrosion and desulfurization; It is used as a thermal insulation material and as a flame retardant for construction. It is also an extremely haode desulfurizer, which is needed in the exhaust duct of Ji Sihui's sulfuric acid workshop, which can effectively purify the polluting gas in the acid production process.

After heating, the sodium chloride is easily pumped into the electrolyzer and filled. Ji Siwei pulled down the switch, and the whole electrolysis process began automatically. He wore a set of anti-electric labor protection clothing, and also wore anti-electric rubber-soled shoes, and used a voltage detector to measure the surroundings of the electrolytic cell and the floor of the workshop - there was no leakage.

The outlet begins to flow out of the electrolyte-liquid. The color-color is clear, and there is no terrible black-color-liquid-body. He waited silently for five minutes to calculate whether the electrolyte-liquid-flow was normal, and he measured the temperature and voltage in the tank - everything was normal. The temperature and voltage are normal or not, which determines the electrolysis efficiency in the tank.

"What comes out is caustic soda solution." Bai Yu asked.