01 temperature characteristics and relationship of different materials

Temperature characteristics of ferrous sulfate

Ferrous sulfate is the main raw material for the production of polymerized ferric sulfate. No matter how you get it, you should pay attention to the temperature characteristics of ferrous sulfate when it exceeds the critical temperature.

We usually use ferrous sulfate containing seven crystal water (some also use ferrous Monohydrate). If the temperature is too high, the crystal water will be lost or even hydrolyzed. Usually, ferrous sulfate is irreversible after hydrolysis, which will cause material turbidity and seriously affect product appearance.

Temperature characteristics of metatitanic acid

Now the production of polymeric ferric sulfate is not only using ferrous sulfate as raw material, but also starting to contact with a large number of iron containing dilute acids in other industries. Such as acid pickling waste acid in iron and steel industry, acid pickling waste acid in electroplating industry, and etching waste liquid in electronic industry. Especially in recent years, many manufacturers have adopted iron containing dilute acid which is separated from solid and liquid before washing in titanium dioxide industry. In addition to sulfuric acid and ferrous, this kind of dilute acid also has titanium oxide, which exists in the form of metatitanic acid in dilute acid.

For many years, scientific experiments have proved that titanium dioxide has a unique photochemical effect in the process of water treatment. Therefore, a small amount of titanium dioxide is contained in the materials and products, which is beneficial to the water treatment application of poly iron. However, metatitanic acid will hydrolyze rapidly to titanium dioxide when it exceeds the critical temperature, and the colouring ability and covering ability of titanium dioxide make the appearance of the product turbid.

1. Temperature characteristics of PFS

The temperature in the production process is related to the product quality and application effect. There are a lot of hydroxyl groups in PFS. When the temperature is too high, PFS will hydrolyze and become muddy. The structure of PFS depends on the synthesis temperature. The amorphous structure is synthesized at low temperature, while the crystal structure is synthesized at high temperature.

2. The relationship between reaction temperature and reaction time

In practice, it is found that the temperature in the production process goes through three temperature stages. The whole reaction process is also accompanied by the process of temperature change. The three temperature segments are material configuration temperature, early rapid reaction temperature and late stable reaction temperature, and the three temperature segments are in ascending ladder shape. Can effectively adjust and control the temperature, can effectively control the reaction time.

The reaction time is determined by three aspects

Material temperature rise stage control

Configuration of equipment and devices

Operation technology and experience

3. The relationship between reaction temperature and pressure

The preparation process of PFS usually includes normal temperature and normal pressure, normal temperature sealing, heating and normal pressure, heating and sealing, heating and pressurizing, etc. now the common methods are normal temperature sealing and heating and sealing.

As the reaction process of PFS is exothermic, the reaction heat will gradually increase the temperature of materials in a closed reactor. The rise of material temperature causes the gas expansion in the gas chamber (the expansion coefficient of gas is far greater than that of liquid) to form the pressure in the kettle. If the pressure of the gas chamber in the kettle is too high, the pressure difference with the feeding will be reduced, which will affect the feeding speed in the pipeline and reduce the injection amount of oxidation gas, thus affecting the oxidation speed.

Because the reactor bears a certain pressure, it involves the safety of pressure vessels. Therefore, when controlling the reactor, it is necessary to provide the technical parameters including the pressure to the manufacturer, and require the manufacturer to provide the safety performance supervision and testing certificate of the pressure vessel.

4. Relationship between oxygen supply mode and oxidation rate

There are two ways of oxygen supply: constant current and constant pressure oxygen supply and constant pressure variable current oxygen supply.

As the reaction process is always accompanied by temperature changes, there will be two peaks of violent reaction, which is manifested in the rapid consumption of oxygen. The two intense reaction periods are endothermic reaction, and the pressure in the kettle will decrease. If the two reaction periods are missed, the reaction time will be prolonged.

There are two ways of constant current and constant pressure, one is low pressure and constant current, which is usually used in the process of producing PFS at normal temperature and pressure; the other is high pressure and constant current, which is usually used in the process of producing PFS at high temperature and high pressure. The difference of oxygen supply mode and oxygen injection position will directly affect the oxidation efficiency.