6. Factors affecting the settlement of titanium liquid
1. Colloid In theory, the content of colloid in titanium liquid is high, which can be solved by adding AMPAM flocculant, but often it is not effective to add more flocculant. Sometimes the titanium liquid colloid suddenly increases. Because there is no instrument monitoring, the amount of AMPAM cannot be increased in time. The result is very poor, and it needs to be increased again to solve the problem. Sometimes even the addition of the settling agent is still ineffective, so I have to add the titanium liquid to the next few batches of titanium solution for further treatment. Because multiple hard settling colloid solution of titanium, titanium dioxide plant so some of the titanium iron ore into the plant magnetic separation once again, to a non-titanium impurities as much as possible, both to reduce consumption of sulfuric acid, but also reduce the impurities in the colloidal solution of titanium The content is favorable for the sedimentation of the titanium liquid.
2. Density of titanium liquid The density of titanium liquid is determined by the content of the substance in the titanium liquid. Under the premise that other conditions are unchanged, as the density increases, the sedimentation effect deteriorates. This is because the density of the titanium liquid increases, the density difference between the flocculated gel and the liquid phase decreases, and the sedimentation speed of the particles becomes slow. The concentration of titanium liquid is proportional to the density, and the density of titanium liquid rises, indicating that the concentration of titanium liquid increases, the viscosity of titanium liquid increases, and the colloid is not easy to settle (see Figure 2). 5-1. 55之间。 Titanium liquid relative density is small, favorable to settling, but will increase the difficulty of concentration of the titanium liquid, generally controlled between 1. 5-1.
3. Temperature The temperature rises and the viscosity of the titanium liquid decreases, which is beneficial to the sedimentation of the particles. However, for the titanium liquid, when the temperature rises above 60 ° C, the stability of the titanium liquid decreases, the molecular thermal motion accelerates, and the ability to flocculate the bridge into the net and capture the colloidal particles decreases, so that the sedimentation effect is significantly reduced. It is hot in summer and difficult to settle; it is cold in winter and easy to settle. This is the truth. However, if the temperature of the titanium liquid is too low, the viscosity of the titanium liquid and the viscosity of the flocculant are both increased, which also reduces the sedimentation effect. Therefore, it is necessary to take corresponding insulation measures. The general control temperature is (60 ± 5) °C. The temperature is difficult to settle outside the range of 49-65 °C.
4. Trivalent Titanium Content As the content of trivalent titanium in the titanium liquid increases, the coagulation effect is enhanced, and the sedimentation effect can be improved. However, if the concentration of trivalent titanium is too high, the viscosity of the titanium liquid will increase, which is not conducive to sedimentation. At the same time, the trivalent titanium content is too high, due to excessive reduction, the effective acid of the titanium liquid is reduced, according to the calculation of titanium dioxide per pot of 12m 3 , for each increase of lg / L trivalent titanium, it will consume 14. 7kg of sulfuric acid, if added 5g /L trivalent titanium, the whole pot will consume 73.5kg of sulfuric acid. The more trivalent titanium is added, the more sulfuric acid is consumed, the less effective acid in the titanium liquid, the worse the stability of the titanium liquid, and the more difficult the sedimentation of the residue. At the same time, the trivalent titanium is too high, and because it does not undergo thermal hydrolysis, it does not form metatitanic acid precipitation, but directly affects the hydrolysis rate, resulting in a decrease in the recovery rate of titanium. Generally, the pressurized hydrolysis method controls the trivalent titanium content to be 2-5 g/L; and the atmospheric pressure hydrolysis method controls 1.5-3.Og/L. [next]
5. F value and stability F value is high, the free acid in titanium liquid is more, can inhibit the early hydrolysis of titanium liquid, the titanic acid colloid in titanium liquid is reduced, which is conducive to sedimentation. It is important to increase the F value appropriately, increase the free acid of the titanium liquid, improve the stability of the titanium liquid, inhibit the early hydrolysis of the titanium liquid, and avoid excessive generation of metatitanic acid colloidal particles. However, in the atmospheric hydrolysis method, the F value is greater than 1.95, which has an adverse effect on the late hydrolysis and the color reduction of the product. The sedimentation curves of different F-value titanium liquids are shown in Fig. 3.
6. Quality and concentration of the settling agent The activity of the modified AMPAM settling agent is large, and the sedimentation effect is particularly remarkable. However, the storage time is too long, the colloid has become agglomerate, the activity is poor, and the sedimentation effect will also be deteriorated. Therefore, the newly prepared AMPAM is the best.
When the concentration of the polymer settling agent is low, the dispersion is uniform, the viscosity is small, the contact surface with the titanium liquid is large, and the flocculation sedimentation effect is good. If the concentration is too high, the polar group of the polymer is curled inwardly in a spherical shape, and the viscosity is large, and it is difficult to disperse in the titanium liquid, and a floc is easily formed on the surface of the titanium liquid, and the flocculation ability is lost.
7. The amount of settler The amount of settler is the key to ensuring the sedimentation effect. The amount should be equal to the total negative charge carried by the flocculant and the positive charge of the suspended solid particles in the titanium solution. Thus, the entire titanium liquid is electrically neutral and has the best flocculation effect. The sedimentation effect of the sedimentation agent is even better. If the dosage is not used properly, the good sedimentation effect will not be obtained. Insufficient dosage, not enough to neutralize all positive charges, sedimentation is not complete; adding excess sedimentation agent, all neutralizing the positive charge in the titanium liquid, there is still a surplus of negatively charged settler colloid, so that the particles re- It carries a negative charge and tends to be stable and difficult to settle (see Figure 4). A suitable amount of the settling agent is Im 3 titanium solution, and 1% of AMPAM 3-7L is added. [next]
8. Settlement operation and type of settler Stirring is a necessary condition for obtaining an ideal settling effect, and the settling agent can only exhibit its cohesive ability when it is uniformly dispersed. However, excessively strong or prolonged agitation will cause the large agglomerated flocs to disperse into small agglomerates and deteriorate the sedimentation effect. The stirring time is too short and the sedimentation rate is too fast, the sedimentation agent concentration is too high, and the sedimentation effect is poor.
Different types of sedimentation agents have different sedimentation effects. In addition to the AMPAM described above, there are many different types of settlers with different slag removal effects. The former Soviet Union used 33 different settlers for testing. As a result, sodium cellulose sulfate and sodium alkylbenzene sulfonate were the best.
Seven, the solution to the difficult settlement of debris
According to the different conditions of the difficult liquid deposition of the titanium liquid, the corresponding method can be selected to effectively settle the residue.
1. Add more sulfuric acid during acid hydrolysis or add more waste acid during leaching to improve the stability of the titanium solution and facilitate the sedimentation of the residue.
2. If the stability of the titanium liquid is good and it is difficult to settle, it is because the titanium-titanium contains too much non-titanium material such as sediment, and the solution is to increase the magnetic separation once to remove the non-titanium impurities.
3. When the seasonality is affected and the clarity is deteriorated, or the colloid is greatly increased due to excessive titanium oxide non-titanium impurities or acid hydrolysis, improper leaching operation, etc., and the sedimentation effect is poor, the AMCAM may be appropriately increased. Flocculant, or both coagulant (Sb 2 0 3 dissolved in concentrated hydrochloric acid, then added to the titanium solution, and then add a Na 2 S solution from the bottom with a hose or stainless steel tube), plus AMPAM flocculant Solve it.
4. If the stability of the titanium liquid is good, the ilmenite is selected and still difficult to settle, which is due to poor control of the sedimentation factors, such as improper addition of AMPAM, or too high leaching temperature. The solution is to improve the operating conditions.
Eight, the inspection of titanium liquid slag removal
Determining the clarity of the titanium liquid is one method of controlling the degree of purification of insoluble impurities in the titanium liquid. The measuring step is to use a plastic tube with a length of about lm, block one end with a thumb, insert the other end into the titanium liquid, and then release the thumb, the middle layer of titanium liquid is sucked into the sampling tube, and then used. Put the thumb on the plastic tube, take out the measuring cup, measure 80mL sample, add a Buchner funnel with a diameter of 7cm and double-layer industrial filter paper, vacuum filter, filter and add about 8mL of water to rinse the filter paper. After blotting, remove the filter paper and check the color depth and clarity of the residue on the filter paper to determine whether the clarity is acceptable. The filtrate settled in the settling tank requires a small amount of black mechanical impurities in the first layer of the double-layer filter paper, and the second layer is colorless or substantially colorless.
It can also be tested by light transmittance. First, the blue black of trivalent titanium is oxidized to the colorless of tetravalent titanium with hydrogen peroxide, and then measured by a spectrophotometer. The higher the light transmittance, the better the sedimentation effect. The sedimentation effect can also be checked by visual inspection of titanium liquid. That is to use a number of glass measuring cylinders to take the turbid titanium liquid to be tested, and then add different concentrations or different amounts of the settling agent, stir evenly, and let stand for a period of time, respectively, using a pipette to absorb 30% of H 2 O 2 Hydrogen peroxide, reach the bottom of the measuring cylinder, relax and slowly lift the pipette, let the hydrogen peroxide flow out, completely oxidize the trivalent titanium in the titanium liquid to become a transparent liquid, and then observe with the naked eye the presence or absence of colloid or colloid. The settlement is good or bad.
The measurement of the size of the colloidal particles in the titanium solution can be carried out using an electron microscope or the like.
