CS254040B1 - Drying method of the crystalline hexamethylenetetramine - Google Patents

Abstract

The solution is to reduce material complexity of the Crystalline production process hexamethylenetetramine and decrease in production waste leader from process. That purpose is achieved by being a scrubbing medium and / or as a component thereof in a wet process separation of the dust particles of hexamethylenetetramine drifting media using juicy condensates from the evaporation process aqueous solutions of hexamethylenetetramine, in an amount of 0.1 to 2 kg per 1 kg crystalline hexamethylenetetramine, as follows composition: more than 90 wt. water, 0.001 to 1 wt. ammonia, 0 to 4% wt. methanol and 0.005 to 7 wt. hexamethylenetetramine.

Description

The invention relates to a process for drying crystalline hexamethylenetetramine.

Hexamethylenetetramine is formed by the condensation reaction of formaldehyde and ammonia. It is used mainly in the production of plastics, pharmaceutical products, explosives and the like.

Most often, the condensation reaction is carried out by reacting aqueous solutions of formaldehyde and ammonia. Since the condensation reaction of ammonia with formaldehyde is an exothermic colored process, this is used in each technology to reduce the energy consumption of the entire process.

To obtain a suspension of crystalline hexamethylenetetramine in aqueous mother liquors, crystallization evaporation of aqueous hexamethylenetetramine solutions formed in the condensation process is used. In order to minimize the heat excrement excrements of hexamethylenetetramine, evaporation takes place at low temperatures of - 50 to -5 ° C and reduced pressure. In the evaporation condensation system, succulent condensates are formed which, in addition to water, also contain ammonia and hexamethylenetetramine, entrained in the sprays from the evaporator. Together with other waste waters, these condensates are disposed of in a wastewater treatment plant, which is also one of the drawbacks of the hexamethylenetetramine production process thus conducted.

To obtain a solid phase from the suspension, crystalline hexamethylenetetramine is obtained, most commonly using centrifugation, whereby a moisture content of 2 to 4% by weight is obtained.

Washing options and its effect on crystalline hexamethylenetetramine are described in more detail in the description of the invention to AO 250 012, which addresses the use of suction condensates from the process of evaporating aqueous hexamethylenetetramine solutions in the solid phase separation process from the cake wash suspension.

Further reducing undesirable moisture below 0.5 wt. in the crystalline product, it is carried out in driers of various construction, in particular fluid, drum, vibration and the like.

Another important factor, apart from the design of the drying device itself, is the separation of fine dust fractions from the drying medium, not only in economic but also environmental terms. Cyclone separators have proven inadequate in these conditions, so further separation of fine particles of hexamethylenetetramine is necessary, either by means of fabric (sleeve) filters or substantially more efficient and safer so-called. wet separators. Spraying, usually of water, of different quality parameters yields an aqueous solution of hexamethylenetetramine, which is recycled to the evaporation process. Wet separators can be sprinkled eg. well or process water, which are disadvantageous, however, as they result in an increased concentration of calcium and magnesium in the product and a deterioration in its appearance, thereby limiting its use.

These disadvantages can be solved by the use of steam condensate, but this entails an increase in the cost of producing crystalline hexamethylenetetramine.

In the study of these problems, it has been shown that the solution to the bulk of the disadvantages resulting from the scrubbing media used hitherto in the drying of crystalline hexamethylenetetramine, as well as the reduction of waste water pollution from this production can be achieved by the process of the present invention.

SUMMARY OF THE INVENTION The present invention provides a process for drying crystalline hexamethylenetetramine separated from a suspension obtained by crystallization concentration of aqueous hexamethylenetetramine solutions prepared by the condensation reaction of formalin solutions and ammonia.

Downstream of the crystalline hexamethylenetetramine drying plant is wet scrubbing of entrained hexamethylenetetramine dusts, where suction condensates are formed which are formed by the condensation of vapors from the evaporation process of aqueous hexamethylenetetramine solutions at a temperature of 50 to 65 ° C.

An essential component of the suction condensates is water, more than 90% by weight, but also contain 0.001 to 1% by weight. % ammonia, 0 to 4 wt. % methanol and 0.005 to 7 wt. hexamethylenetetramine.

Depending on the efficiency of the cyclone separators as well as the wet scrubbing alone, 0.1 to 2 kg of suction condensates are consumed to produce 1 kg of hexamethylenetetramine, and the aqueous hexamethylenetetramine aqueous solution formed is recycled to the process.

The process according to the invention has a number of technical-economic advantages. In particular, the costs of disposal of suction condensates at the wastewater treatment plant will be reduced, the material costs of production and / or production will be reduced. loss of hexamethylenetetramine, since the steam condensate was replaced by waste suction condensate from the evaporation of aqueous hexamethylenetetramine solutions.

The following examples illustrate the most important advantages:

Example 1 (comparative)

For the condensation reaction in the production of crystalline hexamethylenetetramine, 4 750 kg of 37% formalin and 637 kg of 100 percent ammonia are charged. 5 387 kg of an aqueous solution having a concentration of 25% by weight are obtained. hexamethylenetetramine, which is subjected to crystallization thickening, whereby a 75% suspension is obtained, with 2125 kg of sucrose condensates containing 1.3. 10 ^-3 kg ammonia / kg, 5.5. 10 ~ ³ kg hexamethylenetet254040 ramine / kg showing chemical oxygen demand 21. 10 ^-3 kg oz / kg of waste leaving the Vedas and then passes through the cleaning of wastewater, in which the cost of the purified 1,4 CSK / kg Chemical Oxygen.

After centrifugation, 1275 kg of hexamethylenetetramine having a moisture content of 2% by weight are obtained. After drying to a moisture content of 0.3 wt. 1,250 kg of crystalline hexa methylenetetramine are obtained, with 550 kg of steam condensate being consumed in wet scrubbers mounted on a fluid-bed dryer and cyclone.

Example 2

Under the analogous conditions to Example 1, a suspension of hexamethylenetetramine is prepared which, after centrifugation of the solid phase, is dried under the analogous conditions to Example 1, but using 550 kg of suction condensates obtained by evaporation of aqueous hexamethylenetetramine solutions characterized by and the quantitative aspect of Example 1. 1,254 kg of crystalline hexamethylenetetramine of analogous quality parameters to Example 1 were obtained.

Claims (2)

A method of drying crystalline hexamethylenetetramine separated from a suspension obtained by crystallizing the concentration of aqueous hexamethylenetetramine solutions prepared by the condensation reaction of formalin solutions and ammonia, wherein wet separation of entrained dust fractions of hexamethylenetetramine is included as a drying medium, its component in the process of wet separation of hexamethylenetetramine working portions is used to invent the succulent condensate from the evaporation of aqueous hexamethylenetetramine solutions. 2. The process according to claim 1, characterized in that 0.1 to 2 kilograms of suction condensates containing more than 90% by weight are consumed per kg of crystalline hexamethylenetetramine in the wet scrubbing process. water, 0.001 to 1 washes. wt. % ammonia, 0 to 4 wt. % methanol and 0.005 to 7 wt. hexamethylenetetramine.