What are the factors that affect the evaporation and gasification of raw materials in the Formaldehyde Production Proces

Formaldehyde, colorless and irritating gas, chemical formula HCHO or CH₂O, molecular weight 30.00, also known as antaldehyde. Colorless, irritating to human eyes and nose. The relative density of gas is 1.067 (air = 1), and the density of liquid is 0.815g / cm³ (-20 ° C). Melting point -92 ° C, boiling point -19.5 ° C. Soluble in water and ethanol. The concentration of the aqueous solution can reach up to 55%, usually 40%. It is called formaldehyde and is commonly known as formalin.

Formaldehyde Equipment

It has reducing ability, especially in alkaline solution. It can burn, vapor and air form an explosive mixture, and the explosion limit is 7% -73% (volume). The ignition point is about 300 ° C.

It can be produced by methanol dehydrogenation or oxidation under the catalysis of silver, copper and other metals in Formaldehyde Equipment, and it can also be separated from the oxidation products of hydrocarbons. Can be used as raw materials for phenolic resin, urea resin, vinylon, urotropine, pentaerythritol, dyes, pesticides and disinfectants.

Industrial formaldehyde solution generally contains 37% formaldehyde and 15% methanol as a polymerization inhibitor with a boiling point of 101 ° C.

Why the raw methanol evaporates

Formaldehyde Production Process is a gas-solid phase reaction process;

The control of the mixing ratio of the methanol-air mixture is completed in the gasification process.

Factors affecting evaporation

1 evaporator structure

The structure and state of the evaporator determine the efficiency of evaporation. The heat supply coefficient α on the condensation side of the heating steam is relatively large, while the heat supply coefficient α on the methanol side is relatively small. In order to achieve better heat transfer efficiency, the heat supply coefficient on the methanol side must be strengthened in the structural design. Therefore, at the time of design, the circulation rate of the raw material methanol must be high to improve the heat transfer and enhance the evaporation.

2 evaporation temperature

It is common knowledge that liquids are heated to evaporate and vaporize, and it is certain that increasing the temperature is beneficial to the evaporation of methanol. However, when the liquid temperature is lower than the boiling point temperature during the operation, the liquid can only be vaporized on the surface, the evaporation rate is slow, and the production efficiency is low. In actual production, air is bubbled in the methanol liquid layer, and the gas phase methanol in the liquid layer is continuously taken away by the air. In order to establish a new gas-liquid equilibrium, methanol must be evaporated quickly, so that it still evaporates quickly even below the boiling point temperature. Meet production requirements.

3 evaporation level

Under normal circumstances, the level of the evaporation level affects the heated area and circulation speed of this methanol. According to the evaporative heat transfer rate equation, within the optimal heating height range, the higher the evaporation level, the greater the evaporation amount.

4 Methanol concentration and the equilibrium concentration of methanol

When the water content in the raw material methanol is high, the evaporation amount will decrease. In order to maintain the evaporation amount, the evaporation temperature must be increased accordingly.

In the production process, the liquid methanol concentration in the evaporator is commonly referred to as the "equilibrium concentration", which is related to the methanol concentration in the feed, air temperature, humidity, flow rate, and the degree of heating of the evaporator.

5Air velocity

In the production of formaldehyde, air is bubbled in a methanol solution to accelerate the evaporation of methanol, and the evaporation amount of methanol will increase significantly with the increase of air flow. Therefore, in the design of the evaporator, the method of air distribution also affects the evaporation of methanol.

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