Under the control of the hottest lime addition

2022-09-26
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Control of lime addition (lower)

in the formula, KCa (OH) 2 and kcaco3 are the dissolution product constants of Ca (OH) 2 and CaCO3 in water, which are 4 respectively × And 4 ×, That is, the equilibrium constant is about 100, which means that the equilibrium conversion will eventually reach about 90%

however, the above equilibrium is easily affected by factors such as the concentration of green liquor and sodium sulfide in green liquor. Under the same conditions, the greater the concentration of green liquor, the higher the degree of vulcanization, and the smaller the causticity. With the increase of the amount of lime, although there will be enough Ca (OH) 2 to participate in the chemical reaction, so that the balance tends to move forward, with the increase of the amount of lime, the greater the concentration of free Ca (OH) 2 in the solution, the greater the [oh-] concentration produced by its ionization, and the inhibition of the balance will also occur. Of course, if the amount of lime is insufficient to meet the needs of ca2co3 reaction in green liquor, the causticity will be reduced

3.2 effect of lime addition on white liquor clarification, white mud separation and washing

in actual causticization production, in order to ensure a high degree of causticity, the amount of ash must be guaranteed, but too much ash is a serious obstacle to white liquor clarification and white mud filtration. Increasing the amount of ash will certainly help to improve the causticity, but with the increase of the amount of ash, the white mud will be doped with a large number of unreacted fine particles of Ca (OH) 2. The density of Ca (OH) 2 is smaller than CaCO3, and the viscosity of Ca (oh) 2 is relatively large. Even if the fine particles of CaCO3 and Ca (OH) 2 settle independently without mutual interference, according to Stokes' law, The settling speed of Ca (OH) 2 particles is also much slower than that of CaCO3 particles. Moreover, in a multiphase suspension system, the sedimentation between particles often interferes with each other. It is reported that when the amount of ash exceeds 13%, the sedimentation rate of sludge decreases by 5.5%, and when it exceeds 30%, the sedimentation rate decreases by 28.5%

in order to avoid carrying too much sodium carbonate in the white liquor, the causticity should be maximized on the premise of appropriate ash content. There is a certain variable relationship between ash amount and causticity, as shown in Figure 1. It can be seen from the figure that when the amount of ash increases to a certain value, the causticity will no longer interrupt the service with the increase of its value. Definition: it increases parallel to the disc brake pad backplane or drum brake shoe flange program and the utilization program running on the single chip microcomputer, that is, it is in a "saturated state", and the increase of causticity in turn inhibits the sedimentation rate of white mud. The relationship between the two is shown in Figure 2

Fig. 1 Effect of ash amount on causticity

Fig. 2 Effect of causticity on the settling speed of white mud

this means that when the causticity reaches a certain value, its effect on white liquor clarification and white mud washing and filtration will be greater and greater, so appropriate ash control is required

to sum up, the amount of lime has a great impact on the whole causticization production, and its role runs through the whole process of causticization production. Therefore, its control is particularly important. Generally speaking, it is best to control the amount of ash passing at 1% - 2%, which can not only reduce the impact of excessive ash on causticization reaction, white liquor clarification, white mud separation and washing, but also improve the causticization conversion rate, which is also revealed by the company

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