The silver-catalysed formaldehyde process

The silver-catalysed process produces formaldehyde by reaction of methanol vapour
and air on a silver catalyst. Oxidation and dehydrogenation of methanol are the
basic mechanism of the silver-catalysed route.

Methanol is vaporised in an evaporator and the vapours mixed with air will go through
the reactor containing a bed of pure silver in a granular crystalline form.

The reactor is supported above a steam boiler so that the reaction products pass
through the boiler tubes before passing to further cooling stages and produce steam
(heating transfer between the reacted gases and water).

The reacted gases containing formaldehyde, methanol and water are condensed 
and cooled in passing to a circulating absorber column followed by a first methanol 
scrubbing system and in a second step a water scrubbing system for the effluent 
gases. 

The aqueous formaldehyde-methanol is removed from the absorber to a distillation
column to separate methanol and aqueous formaldehyde. The methanol is returned
to the process as reaction feed and the aqueous formaldehyde up to 55% 
formaldehyde with 1 % or less of methanol is stored into tanks.

The process vent gas (after scrubbing) which contains approximately 20 % hydrogen
and small amounts of methanol, formaldehyde, and methyl formiate are burned in
a boiler to produce steam.

We developed a 10~80kt/a formaldehyde equipment is characterized by its advanced
technological process (recycled exhaust), advanced automation (DCS control system),
high safety and reliable, low consumption in raw material and energy, reasonable
structure (new structural oxidizing equipment) long performance life, high
efficiency and other options. All the technical indexes have reached the advanced
levels at home and abroad.

It is also used in other parts. The material is carbon steel.

Specifications: 
1) Concentration of formaldehyde: 37 ~ 50%
2) Content of formaldehyde: ≤ 0.8%
3) Content of formic acid: ≤ 0.005% 
4) Raw material consumption: ≤ 0.445T/T
5) Energy consumption: ≤ 25kWh/T
6) Volume: 0.5 ~ 63