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.
We are Formaldehyde Production Plant, welcome to
consult.
