CS252538B1 - Method of exchangers' cleaning during urea-formaldehyde and phenolformaldehyde condensates production - Google Patents

Description

The object of the invention is a method of cleaning heat exchangers used in the production of formaldehyde condensates which are used as binders, adhesives, molding materials and the like.

In the production of formaldehyde condensates, in particular urea-formaldehyde condensates, relatively rapid contamination of the heat exchange surfaces and the formation of a solid adhesive layer on the surface of the tubes occur. Cleaning by a conventional method mechanically is very difficult or impossible, as a layer of condensates is very tough. Impurities on the surface of the tubes are not soluble in water or other solutions. Clogging of heat exchangers in the production of formaldehyde condensates is a difficult problem to solve and substantially reduces heat transfer.

The essence of the proposed method of cleaning consists in thermally disrupting the deposited polycondensates by heating the steam and by interacting with or with or without the addition of alkali. Heating of the exchanger for cleaning can be carried out conventionally by connection to steam from 0.3 to 1.5 MPa. The heat exchanger is heated at a temperature of 150 to 300 ° C. During heating, the exchanger is watered with or without the addition of alkali so as to soak the deposited impurities. The effect of heat causes further glowing reactions, which are characterized by the coloring of the deposited impurities in the rye until red-brown. This results in water-miscible compounds and after such a heat exchanger preparation, pressure water cleaning is performed, preferably using a high pressure pump.

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SUBJECT

Claims (1)

SUBJECT Process for the purification of heat exchangers used in the production of urea-formaldehyde, phenol-formaldehyde and other formaldehyde condensates characterized in that the cleaned exchanger is heated with steam at a pressure of 0.3 to 1.5 MPa to a temperature of 130 to 300 ° C, periodically in 1 to 3 days. it is possible to clean the exchanger up to the metal material. It is also possible to clean the exchanger with old deposits. Regular cleaning results in faster deposition of deposits and cleaning of the exchanger. Preferably, one or more resp. clean more heat exchangers into reserve and then plug them into the production process. Cleaning does not damage the pipes and heat exchange surface. Preferably, a higher vapor pressure and a higher decomposition temperature are used with respect to the maximum permissible pressure for the exchanger vapor space. The four-pass, horizontal, tubular, 40/36 mm tube diameter was deposited after 5 months of operation with deposits of urea-formaldehyde condensate 5-10 mm thick inside the tubes, some tubes being clogged completely. The number of pipes in one section is 70, the pipe length is 4000 mm. The exchanger was connected to a steam of 0.35 MPa brought into the water space, after about 3 days it was moistened with water on the side of the adhesive (sediment). After a further three days, the glue deposit began to colour into the rye. After water was re-poured, deposits were washed out and after the vapor was carefully released, the impurities were blown out of the water out of the pipes. After the steam was shut down, the exchanger was cleaned with a Woma high-pressure pump, which was sprayed with dirt. During steam heating, precautions were taken against scalding of the operator or accidental extrusion of dirt from the pipes. rinses with water containing 0 to 3% alkali, preferably NaOH, until the decomposition of the deposits is manifested by the coloring of the condensate deposits into rye to reddish-brown, resulting in decomposable or decomposable decomposition products. water soluble and the exchanger is cleaned by spraying with pressurized water.