Method for reducing formic acid in formaldehyde recovery system

Abstract

The invention discloses a method for reducing formic acid in a formaldehyde recovery system. The method comprises the following steps: mixing alkali liquor with wastewater in a wastewater storage tank to obtain dilute alkali liquor; the method comprises the following steps: mixing dilute alkali liquor with formaldehyde-containing wastewater through an online static mixer, feeding the mixture into a feeding tank of a formaldehyde recovery tower, neutralizing formic acid in the formaldehyde-containing wastewater by using the dilute alkali liquor, and controlling the pH value to be 6.5-7; the deacidified formaldehyde-containing wastewater is preheated by a preheater and then enters a formaldehyde recovery tower to be rectified; adding alkali liquor into the tower kettle of the formaldehyde recovery tower, and neutralizing formic acid in tower kettle liquid by using the alkali liquor; cooling the top gas of the formaldehyde recovery tower, feeding the cooled top gas into a reflux tank, feeding one part of the top gas into the top of the formaldehyde recovery tower to serve as reflux liquid and feeding the other part of the top gas into a crude formaldehyde storage tank according to a reflux ratio of 1.4: 1 after sampling analysis is qualified; one part of tower bottoms of the formaldehyde recovery tower is heated and then circularly reflows, and the other part of the tower bottoms of the formaldehyde recovery tower exchanges heat with the deacidified formaldehyde-containing wastewater and then enters a wastewater tank. The invention can effectively reduce the formic acid content in the formaldehyde recovery system, reduce the corrosion of equipment and pipelines, prolong the service life and improve the quality of recovered formaldehyde.

Description

technical field [0001] The present invention relates to a kind of method for reducing formic acid, more particularly, to a kind of method for reducing formic acid in formaldehyde recovery system. Background technique [0002] The formaldehyde recovery system in the polyoxymethylene production unit is mainly used to recover formaldehyde in the formaldehyde-containing wastewater in each section. The recovered formaldehyde solution with a concentration of about 35% is stored in the crude aldehyde storage tank, and then enters the trioxymethylene and dioxane process to participate. reaction. Due to side reactions and formaldehyde oxidation, the formic acid content in the formaldehyde-containing wastewater is relatively high, about 2%. The operating temperatures at the bottom and top of the formaldehyde recovery tower are 162.5°C and 147-153°C, respectively. Because the boiling point of formic acid is 100.6°C, which is close to water, most of the formic acid contained in the for...

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Problems solved by technology

Excessively high formic acid in the light components escaping from the top of the formaldehyde recovery tower and the heavy components discharged from the tower not only causes severe corrosion of the equipment and pipelines in the formaldehyde recovery system, shortens the service life, but also reduces the quality of recovered formaldehyde. Subsequent participation in production has adverse effects

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