Process and apparatus for preparing methanal with low transformational cycle method

Abstract

The invention relates to the field of production process of formaldehyde, in particular to a process for preparing formaldehyde by low-transformation cycle method which reduces negative reaction instead of yield and a device thereof, characterized in that formaldehyde and air are mixed and heated for removing fog drops, saturated vapor gas mixture is added for heating and fire retardant filtration, and fed in a reactor having a catalyst of silver for reaction to generate formaldehyde gas, the formaldehyde gas and other gases are quenched and absorbed to carry out aldehyde-alcohol separation on the absorbed finished products, aldehyde is used as a finished product for storage, alcohol kept in the system is used for cycle reaction and fed in the binary mixture of methanol and air after being processed, the left is subject to secondary absorption, thin aldehyde liquid after absorption is recycled and the tail gas which is not absorbed is processed. The device comprises an evaporator, an overheater, a fire retardant filter, a reactor, a combined absorption tower and a cycle pump, wherein the combined absorption tower is a distillation absorption tower and a two-stage absorption tower. The invention has the advantages of low transformation, less negative reaction and low material consumption.

Description

technical field [0001] The invention relates to the field of formaldehyde production technology, in particular to a formaldehyde low-conversion circulation method preparation process and device that reduce negative reactions without reducing yield. Background technique [0002] At present, after more than 50 years of ups and downs in the production of silver-based formaldehyde in China, great achievements have been made in all aspects. The energy consumption has changed from the gas consumption type to the external gas supply type, and the material consumption has changed from 500kg methanol / T 37% formaldehyde to the current 445kg methanol / T T37% formaldehyde, the production capacity has grown from hundreds of thousands of tons to more than 20 million tons today, and the production capacity and technology of silver method have been in the leading position in the world. Formaldehyde production has developed from extensive to refined production, from simple to professional dev...

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Problems solved by technology

[0004] At present, methanol is controlled at 0.5 or no methanol in the products produced, and the conversion rate is increased in some periods of time when the unit consumption is reduced, and there are few negative reactions. 2 , but in the process of increasing the oxygen-alcohol ratio conversion rate, the negative reaction also increases simultaneously, and the tail gas circulation process is more obvious. With the extension of the start-up production cycle, the oxygen temperature increases and the tail gas contains CO+CO 2 The more obvious the increase

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