Unconcentrated dilute titanium liquid can not produce pigment-grade titanium dioxide, because the metatitanic acid particles hydrolyzed by the dilute titanium solution are coarse, the color reduction of the product, the color of the bottom layer is poor, the oil absorption is high, and the hydrolysis process is different. In order to control a certain hydrolysis rate, it is also necessary to concentrate the titanium liquid to a certain concentration and use it.
Titanium is the solute titanyl sulfate, titanium sulfate, ferrous sulfate and the like, and the solvent is primarily water, usually by heating to evaporate the water and concentrated. However, the boiling point of titanium liquid is about 104~114 °C at normal temperature, and the titanium liquid itself is hydrolyzed above 80 °C. In order to avoid early hydrolysis, the concentration of titanium liquid must be evaporated and concentrated under vacuum, and different concentrations of titanium liquid are in See Table 3-9 for boiling points under different vacuum degrees.
Table 1 Boiling point/°C of vacuum of different concentrations of titanium solution under vacuum
TiO 2 concentration / g / L | -0.092MPa | -0.086 MPa | -0.079 MPa | -0.072 MPa | -0.066 MPa |
220 190 160 | 52.5 51 48.5 | 62 59.5 58 | 69.5 67 64.5 | 75.5 72 70 | 79.5 76.5 74 |
It can be seen from the data in Table 1 that the higher the vacuum degree of the titanium liquid of different concentrations, the lower the boiling point, so the maximum temperature of the titanium liquid should be no more than 70, and the vacuum should be maintained at at least -0.08~0.088MPa. In order to obtain high quality concentrated titanium solution. If the degree of vacuum is low and the concentration temperature is too high, not only the stability of the concentrated titanium liquid is poor, but also the solid phase titanium oxysulfate crystals block the evaporator tube due to local overheating, and the titanium oxysulfate crystal dispersed in the titanium liquid will Like seed crystals, it grows and deposits, causing unnecessary losses to production.
Industrial production of titanium usually concentrates upflow film concentrator, the concentrator evaporation chamber, the separation chamber, a heating tube, the feed chamber and the like are generally used corrosion-resistant metal titanium, the steam heating chamber enclosure available plain carbon steel . The material to be concentrated enters the feeding chamber from the bottom, passes through the distribution plate and uniformly enters the titanium tube of the heating chamber, and heats the steam through the tube wall for heat exchange. The molten iron is rapidly evaporated under heat, and the vaporized vapor is entrained. The concentrated titanium liquid rapidly grows into the evaporation chamber along the wall of the tube at a speed of 20~30m/s. In the evaporation chamber, the flow rate is slowed due to the volume expansion, and the vapor-liquid separation device is carried out through the gas-liquid separation device at the top of the evaporation chamber. Separation, the titanium liquid is left in the evaporation chamber and the concentrated liquid overflow pipe enters the concentrated titanium liquid collection tank. The evaporated secondary steam is cooled and condensed with water in a mixing condenser, and discharged through a pneumatic tube (atmospheric leg) of a gas pressure condenser into a water sealing tank. In order to allow the condensed water after cooling to be automatically overflowed from the bottom of the air pressure pipe to prevent the cooling water and the condensed water from flowing into the titanium liquid, the air pressure pipe under the condenser must be kept at a certain height to maintain a certain liquid level in the pipe. The pressure head generated by the liquid column corresponds to the difference between the atmospheric pressure outside the tube and the air pressure in the condenser, and the height of the air tube should be at least 10 m under vacuum. The picture below shows the titanium liquid concentrator.
In order to reduce the energy consumption during the concentration of titanium liquid, the conditional factory should use double-effect series operation to preheat the titanium liquid with the secondary steam generated by the second effect or as the steam of the first effect heating chamber, thus reducing the concentration during the concentration. Steam usage.
The concentration of TiO 2 in the titanium liquid after concentration is generally controlled at about 200-230 g/L when the seed crystal hydrolysis process is used, and is generally controlled at about 230-260 g/L when the hydrolysis process of the seed crystal dilution method is adopted.
Heat Exchanger
A heat exchanger is a device used to transfer heat, usually to transfer heat from one fluid to another without them mixing. A heat exchanger usually consists of a number of parallel pipes in which one fluid flows through the pipe and another fluid flows through the outside of the pipe. In this way, heat can be transferred from one fluid to another for heating or cooling purposes. Heat exchangers are widely used in many industries, such as chemical, pharmaceutical, food processing, air conditioning and heating systems, etc.
Heat exchanger usually consists of the following components:
1. Heat exchange pipe: Pipe used to transfer heat, usually made of metal materials, such as copper, stainless steel, etc.
2. Heat exchange surface: A surface used to transfer heat, usually consisting of metal sheets or pipes. The greater the surface area, the higher the heat transfer efficiency.
3. Housing: Housing, usually made of metal or plastic, used to secure heat exchange pipes and surfaces.
4. Seals: Seals used to prevent media leakage, usually made of rubber or silicone rubber.
5. Support: A support used to support a heat exchanger, usually made of steel or cast iron.
6. Import and export pipes: pipes used for medium entry and exit, usually made of metal or plastic.
7. Cleaning hole: A hole used to clean the inside of the heat exchanger, usually located on the upper or side of the heat exchanger.
8. Insulation layer: Insulation layer used to keep the temperature of the heat exchanger stable, usually made of glass wool or polyurethane foam.
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