A system and method for graded recovery and utilization of dilute formaldehyde in the production of paraformaldehyde

Abstract

The invention relates to the technical field of chemical industry production, and in particular relates to a classified recycling system and method of dilute formaldehyde in paraformaldehyde production. The system is characterized in that a formaldehyde solution storage tank is connected with an evaporator through a pipeline; the evaporator is connected with a distillation still through the pipeline; the distillation still is connected with a dryer through the pipeline; the dryer is connected with an absorption tower through the pipeline; the absorption tower is connected with a precipitation tank through the pipeline; a turbid solution outlet of the precipitation tank is respectively connected with the evaporator and a urotropin workshop through the pipeline; and a clear solution outlet of the precipitation tank is connected with a formaldehyde production workshop through the pipeline. The mixed solution containing dilute formaldehyde and dust in the absorption tower are precipitated, filtered and separated through the precipitation tank, and the upper clear solution is returned to the formaldehyde workshop to be recycled as soft water; and the lower turbid solution is returned to the urotropin workshop to produce urotropin, or to continuously produce paraformaldehyde at a paraformaldehyde poly-concentration section. Through the adoption of the system and method provided by the invention, the yield of formaldehyde is increased, and the economic loss of the urotropin workshop is reduced.

Description

technical field [0001] The invention relates to the technical field of chemical production, in particular to a system and method for graded recovery and utilization of dilute formaldehyde in the production of paraformaldehyde. Background technique [0002] In the production process of paraformaldehyde, the concentration of formaldehyde entering the scraper dryer is about 47%, and it is concentrated to 70% by the scraper dryer and enters the concentration kettle. The evaporated formaldehyde-containing waste gas is sent to the formaldehyde workshop for recycling ; After reaching 2.5m³, enter the rake dryer through vacuum, increase the concentration ≥ 96% to get the finished product, evaporate the formaldehyde-containing waste gas and enter the absorption tower through the condenser, and the waste water contains about 26% of dilute formaldehyde and paraformaldehyde powder, which is in a turbid state , cannot be reused, and the conventional treatment is to send it to the urotrop...

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Problems solved by technology

[0003] In the production process of formaldehyde, the concentration of formaldehyde is adjusted by increasing or decreasing the amount of soft water added to adjust the concentration of formaldehyde solution. When the concentration of formaldehyde is not added with soft water, the concentration is generally 58%-60%. The concentration is high, which is easy to cause tower blockage and pipe blockage. And it is not suitable for the production process requirements, so soft water needs to be added to adjust the concentration of formaldehyde to 48%-50%

[0004] The paraformaldehyde production process is to evaporate excess water by means of steam heating to increase the content of paraformaldehyde, and a large amount of dilute formaldehyde produced by the process is an intermediate product that we urgently need to deal with; in the current production , the dilute formaldehyde produced by the scraper dryer to concentrate formaldehyde can be used for formaldehyde production (instead of soft water), but because the dust generated by the rake dryer during the drying process is also mixed in the dilute formaldehyde produced by the rake dryer, The dilute formaldehyde is turbid and cannot be used for formaldehyde recovery, so it can only be sent to the urotropine workshop to produce urotropine. However, since the profit of urotropine is negative at this stage, the dilute formaldehyde produced by the rake dryer is only used as The raw materials for the production of urotropine are no longer suitable for the development requirements of the enterprise at the present stage, and it is urgent to find another technical means to deal with the dilute formaldehyde produced by the rake dryer

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