Industrial production methods of formaldehyde

Formaldehyde is a colorless gas with a special irritating odor, which has a stimulating effect on the eyes, nose, and other parts of the body. It is easily soluble in water and ethanol. The concentration of the aqueous solution can reach up to 55%, usually at 40%, known as formaldehyde solution, commonly referred to as formalin, which is a colorless liquid with an irritating odor. The main harm of formaldehyde is its irritating effect on skin and mucous membranes. When formaldehyde reaches a certain concentration indoors, people may feel discomfort. A concentration greater than 0.08m3 can cause redness, itching of the eyes, discomfort or pain in the throat, hoarseness, sneezing, chest tightness, wheezing, and dermatitis. Newly renovated rooms tend to have higher formaldehyde levels, which are a major trigger for many diseases.

Industrial production methods

A production method that is stable, low in consumption, and simultaneously produces concentrated formaldehyde and industrial formaldehyde.

The invention is implemented as follows: First, according to existing technology, raw gas that can produce 45-55% (weight) concentration formaldehyde is fed into the reactor. At 600-700°C, a chemical reaction occurs under the action of a silver catalyst. The converted reaction gas is rapidly cooled to 90-95°C, generating high-concentration formaldehyde gas and simultaneously producing a condensate with a concentration of 25-35% (weight). Existing technology sends these two products together to an absorption tower. This invention has three absorption towers in the process after the reactor, where the high-concentration formaldehyde gas and condensate generated in the reactor enter the first and second absorption towers through pipelines, respectively. The first absorption tower has a high-concentration formaldehyde liquid outlet, a gas-phase formaldehyde outlet, and a high-concentration gas-phase formaldehyde inlet, with its gas-phase formaldehyde outlet connected to the gas-phase inlet of the second absorption tower. The second absorption tower also has an industrial formaldehyde outlet, a gas-phase formaldehyde outlet, and an olefin release formaldehyde inlet, with its gas-phase formaldehyde outlet connected to the gas-phase inlet of the third absorption tower. The third absorption tower has a recovery liquid outlet, a tail gas outlet, and a water inlet, with the recovery liquid outlet connected to the condensate outlet of the reactor through a pipeline and also connected to the dilution formaldehyde inlet of the second absorption tower. The high-concentration formaldehyde liquid outlet of the first absorption tower can be connected to the dilution formaldehyde inlet of the second absorption tower through pipelines and valves. By equipping the above devices and adding technical operations, the goal of simultaneously producing concentrated formaldehyde and industrial formaldehyde can be achieved. The process flow is as follows: First, according to existing technology, the formaldehyde conversion gas controlled under the production conditions of 45-55% concentration is sent to the reactor. At a reaction temperature of 600-700°C, a chemical reaction occurs under the action of a silver catalyst. The converted reaction gas is rapidly cooled to 90-95°C, generating high-concentration formaldehyde gas and simultaneously producing a condensate with a concentration of 25-35% (weight). The high-concentration formaldehyde gas is sent through pipelines and the high-concentration gas-phase formaldehyde inlet to the first absorption tower. By operating according to existing technology, a formaldehyde liquid with a concentration greater than or equal to 52% (weight) can be obtained and extracted from the high-concentration formaldehyde liquid outlet. At this time, the temperature of the high-concentration formaldehyde liquid is controlled above 60°C to prevent formaldehyde from solidifying and blocking the pipelines, with the temperature controlled between 60-65°C. In the first absorption tower, not all high-concentration formaldehyde gas can be liquefied, and there remains a portion of gas-phase formaldehyde. Due to the main absorption becoming liquid formaldehyde, the concentration of the remaining gas-phase formaldehyde decreases. This portion of gas-phase formaldehyde will enter the second absorption tower for secondary absorption through the gas-phase formaldehyde outlet of the first absorption tower, pipelines, and the gas-phase inlet of the second absorption tower, generating industrial formaldehyde with a concentration of 37% (weight), which is extracted from the industrial formaldehyde outlet. The temperature of this industrial formaldehyde is controlled above 35°C, preferably between 35-40°C. The concentration of gas-phase formaldehyde that has not been absorbed in the second absorption tower is further reduced, with a concentration of about 10%. It enters the third absorption tower through the gas-phase formaldehyde outlet of the second absorption tower, pipelines, and the gas-phase inlet of the third absorption tower. The third absorption tower does not have the formaldehyde absorption liquid of existing processes; the liquid that guides the gas-phase formaldehyde to liquefy is water. By supplying water through the water inlet, the third absorption tower can absorb the gas-phase formaldehyde discharged from the second absorption tower again, generating a very low concentration formaldehyde recovery liquid. The remaining unabsorbed gas, which is tail gas, is discharged from the tail gas outlet to outside the system. The formaldehyde recovery liquid from the third absorption tower will be sent to the second absorption tower together with the condensate generated by the reactor, serving as the liquid that guides the gas-phase formaldehyde to liquefy. If this liquid's concentration is too low to guide the generation of 37% (weight) concentration formaldehyde, the high-concentration liquid formaldehyde from the first absorption tower can be introduced to increase its concentration. In this way, the second absorption tower can produce industrial formaldehyde with a concentration of 37%. Thus, by utilizing existing technical equipment and following the above methods and device configurations, formaldehyde conversion gas is fully utilized without generating wastewater, while simultaneously producing high-concentration formaldehyde and industrial formaldehyde. The production is stable, the process is simple, and the consumption is low.