In this plant formaldehyde is produced with the oxidation of Methanol with oxygen on a catalyst Fe-MO supported by ceramic.
The oxygen is fed by using a blower (VV 701) that is taking partly fresh air and partly exhaust gases from the outlet of the absorbtion column (C 701) in order to reach the oxygen concentration of the methanol LEL. The concentration is detected continuously by an oxygen analyzer on line.
The gas is fed in the methanol evaporator (E 701) where liquid methanol is added through spray nozzles and evaporated using the heat of the solution taken from a section of the column.
The reaction mixture is fed in F 701 where it is heated up by gases coming out from the reactors, and then goes in the reactors form bottom to top.
The reaction is exothermic and the heat is removed using diathermic oil circulated in each of the seven reactors
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The gas out from the reactors is composed by formaldehyde, oxygen, nitrogen and methanol and goes to the absorbtion column from bottom to top.
The column is divided in three main sections where the solution is circulated by pumps and in the third section is cooled with a plate heat exchanger (F 703).
From the bottom of the column the formaldehyde solution 36-37 % is sent to the storage tank.
The heat of the diathermic oil is removed in a boiler (H 701) which produces steam at 17 bar-g.
The water to produced steam is feed by pump.
To start up the plant before feeding the gas to the reactors, the reactors have to be heated until the temperature of reaction, this is done circulating the oil in a burner (B 701) working with natural gas.