6 replies to this topic

[Has2riasat]

Can somebody provide me with a process flow diagram for the metal oxide process when making formaldehyde ?

[Pilesar]

simple formaldehyde process pfd here: https://ibb.co/d01KKRf

From the formaldehyde entry in the Kirk-Othmer Encyclopedia.

Description:

All of the formaldehyde is made by the exothermic reaction at essentially atmospheric pressure and at 300- 400 C. By proper temperature control, a methanol conversion greater than 99% can be maintained. By-products are carbon monoxide and dimethyl ether, in addition to small amounts of carbon dioxide and formic acid. Overall plant yields are 88-92%. 

Vaporized methanol is mixed with air and optionally recycled tail gas and passed through catalyst-filled tubes in a heat-exchanger reactor. Heat released by the exothermic reaction is removed by vaporization of a high boiling heat-transfer fluid on the outside of the tubes. Steam is normally produced by condensing the heat-transfer fluid. A typical reactor has short tubes of 1.0 to 1.5 m and a large shell diameter of 2.5 m or more. Product leaving the bottom of the reactor is cooled and passed to the base of an absorber. Formaldehyde concentration in the product is adjusted by controlling the amount of water added to the top of the absorber. A product up to 55% formaldehyde and less than 1% methanol can be made. Formic acid is removed by ion exchange. The air-methanol feed mixture must be on the methanol lean side of a flammable mixture. If the oxygen in the total reactor feed is reduced to about 10 mol% by partially replacing air with recycled tail gas, then the methanol in the feed can be increased somewhat without the danger of forming an explosive mixture, and for a given quantity of production, gas flow (air plus recycle) can be reduced by 17 to 37%. Even with gas recycle, the metal oxide process must handle a substantial volume of gas. A typical metal oxide catalyst has an effective life of 12 to 18 months. There is little economic justification to incinerate the metal oxide plant tail gas for the purpose of generating steam. The tail gas is essentially nitrogen and oxygen with combustible components (dimethyl ether, carbon monoxide, formaldehyde, methanol) representing only a few percent of the total. However, increasing environmental pressures make vent incineration more desirable. With the addition of auxiliary fuel, the vent can be oxidized by thermal incineration at temperatures of 700 to 900 C. As an alternative, the stream can be oxidized at 450 to 550 C in a catalytic incinerator which can be thermally self-sufficient with supplemental fuel required only for startup or abnormal operating conditions.

Edited by Pilesar, 07 November 2022 - 02:15 PM.

[Has2riasat]

Thank you so much 

it wasn't that i was unable to find diagrams it was because there were many variations so i was unsure what to base my drawing off. I have to combine this process with the production of novolacs.

Instead of phenol i decided it would be better to use cresol and the formaldehyde. Im aware that there is a  batch resin reactor and batch distillation equipment but i haven’t found any clear pfds for it. Maybe i am wording it incorrectly when I search it up but coul i have some help?
 

[breizh]

Hi,

You should give Pilesar a like (green arrow instead of red) .

Breizh 

[Pilesar]

Thanks, Breizh. Arrow is no problem. I web-searched "cresol formaldehyde novolac resin" and found lots of results. Academic papers are usually pretty good since they contain material balances. Patents are an okay resource, but I don't think as useful as academic papers. The process design patents I usually find are only patents because they are 'different' which is not what you are looking for. Sometimes patents describe the usual way of doing things before describing the new idea but still I prefer to read someone's master's dissertation. You just have to do the research.

[shvet1]

 Im aware that there is a  batch resin reactor and batch distillation equipment but i haven’t found any clear pfds for it. Maybe i am wording it incorrectly when I search it up but coul i have some help?

This situation is subject to what is named Process Design and Process Licensing. Be informed that final cost of both options can become surprisingly high.

 

Instead of phenol i decided it would be better to use cresol and the formaldehyde. 

Note that price of cresols is much higher than that of phenol so a resin should have superior properties to justify resources and time spent to a new product&process design or cost of a royalty to a Licensor.

Attached Files

•  US average prices.pdf   232.03KB   6 downloads

Edited by shvet1, 08 November 2022 - 11:29 PM.

[latexman]

My experience, a long time ago, in phenolic resins was the regulations, operability, and cost of vent and waste water treatment was a major hurdle to profitability.