DE1717162C3 - Process for the preparation of a cyanic acid-ammonia mixture from molten urea - Google Patents

Description

already known per se. However, it is essential to be at a reasonable temperature.

that in each case the evaporation of the urea is the subject of the invention thus a process

succeeds quickly and without leaving any residue, since otherwise the end-stage for the production of a cyanic acid-NHa gas mixture

duct not only in lower yield and greatly reduced by the introduction of molten urea m

uncleaned, but also due to cyanuric acid vaporized form using an inert gas as a bubble gas

Formation of a gradual sticking of the fluidized bed from below into one heated to at least 330 C.

Particle takes place, which in the large-scale permanent fluidized bed made of inert material, with the urea

operated to an inability of the entire 35 extremely quickly to temperatures between 300 and

Plant leads. 480 ⁰ C is heated, characterized in that the

For example, US Pat. No. 2,712,491 describes urea through a central tube and the blowing gas

Process for the production of ammonium cyanate and by a concentrically arranged in

in this context contains both the note, same height or just below the central tube

that solid and liquid urea for this purpose 40 ending jacket pipe with a gas outlet speed

the fastest possible pyrolysis should be subjected to a speed of 40 to 100 or 20 to 100 m / sec.

should, as well as information on the conditions of the Konbar be introduced into the fluidized bed,

dcnsation for the purpose of separating solid ammonia. The implementation of the method according to the invention

cyanate from the reaction gases. More detailed information about rens is given in an obvious way so that in

the type of urea input is absent. But it is 45 a heated fluidized bed reactor of the melted

as a major problem of urea pyrolysis in the zene urea from below by means of a two-substance nozzle

Austrian patent specification 257 621 of the same in the we-

Applicant described. Belschicht is introduced.

How these difficulties can be overcome in the introduction of aluminum blowing gas for the atomization of the liquid urea solid urea is described in 50 substances and as a carrier gas for maintaining the Austrian patent specification 258 881. Fluidized bed is preferably used in ammonia - there is used in connection with the production of sets. However, nitrogen, carbonic acid and cyanic acid have also been proposed to use urea in the form of other gases, crystals or prills with a diameter of 1 to 4 mm, which are inert towards the reactants. Blasegae as well as carrier gas must use anhydrous in order to introduce the primary formation of cyanuric acid 55, since water is known to immediately prevent the urea decomposition. This cyanic acid with the formation of carbonic acid and ammo process is advantageous if the urea would decompose niac.

anyway in the form of crystals or prills for the atomization of the liquid urea coincidence, d. H. not only for the purpose of cyan, to ensure that the exiting beam of acid production through complex measures, such as liquid urea is always surrounded by a jacket of bubble crystallization, sieving and sifting into this form of gas. Occurs because * Blaiegas exactly around which must be applied. In addition, the urine stole can be melted, so a higher gas level urea is required more easily and with a lower temperature of the blasting gas in order to feed in a temperature difference compared to the hot fluidized bed in smooth operation of the urea decomposition. As in those cases in which the outlet but with this type of introduction of the urea is before that of the urea, melt agglomeration occurs in continuous operation. If they exit at the same time, the Fluid bed particles. Gas velocities between 40 and 100 m / sec,

while in the case of the earlier exit of the Blasegjses between 20 and 100 m / sec. The ashing of blowing gas and liquid urea can be done after leaving the nozzle.

A suitable device for carrying out the driving consists of a fluidized bed reactor with eggs with holes in the bottom plate and with c iicr feed of the reactants from below. I> -rch a hole in the base plate leads a two Tf nozzle with central liquid inlet. The nozzle> · - consists of a central pipe for the supply of the i I. '. substance melt and a concentric to the center ;. ' (! pipe arranged jacket pipe, where the central ri'.r at the end in the reaction space

. which ends at the same height as the jacket tube ι; . but surmounts the latter by a few millimeters, This creates a mixture within the nozzle

I ₁ (J contact with the nozzle wall is impossible. The following examples are intended to explain the subject matter of the invention in more detail

Examples

An externally heated fluidized bed reactor with a diameter of 2 (X) mm and a height of 500 mm is filled 185 mm with sand with a diameter of 0.1 to 0.3 mm. 8 (XK) l / h of ammonia at a temperature of 20 ° C. are blown in as a carrier gas through a frit at the bottom of the reactor. Through a central bore in the frit of the type defined below is 2 introduced kg / h urea melt with a temperature of 135 "C and the indicated in Table 1, the amount of ammonia as uasegas with a temperature of 140 ⁰ C from below through a nozzle.

The temperature of the Wirbelsch.cht is maintained at 350-370 ⁰ C.

The two-substance nozzles used with a central liquid inlet have the following dimensions:

Diameter of the jacket pipe:

inner diameter: 4.4mm,

outer diameter: 7.3 mm;
Diameter of the central tube:

inner diameter: 1.85mm,

outer diameter: 3.3 mm;
Nozzle I: central tube 2 mm longer than that

Jacket pipe;
Nozzle 2: central tube and jacket tube of the same length.

Table 1

jet
No. Bladegus Gas speed
age Remarks [l / hl [m / sec] 1 500 about 21 In continuous operation on working wall-free 1000 about 42 the same 1500 about 63 the same 2 500 about 21 After 40 'of incrustation of solid particles the fluidized bed 1000 about 42 In continuous operation on working wall-free 1500 about 63 the same

If the nozzles described are operated in the dismantled state, one can see that the outer jacket pipe in the case of nozzle 1 in none of the three attempts, in the case of nozzle 2 however in an operation with 500 l / h ammonia gas was wetted at its tip with molten urea.

Claims (1)

This is based on the aforementioned Austrian r. ι kar, Pat ^ nurhrift 257 621 concerning the catalytic Claim: see Patentsrnriii <£ -> / "^ trntnlvcatnrfi-n_ 'Production of melamine in a catalyst fi.eß- V experience for the production of a cyanic acid bed directly from urea overcome that N ^ gas mixture by introducing molten urea together with a S uh ^ molten urea in atomized form by means of gas at least at the speed of sound into the H, Q- an inert gas is blown into a bed from below as a bubble gas, vyooei for this purpose z: i! U- The fluidized bed heated to at least 330 C. ! nertmaterial, the urea extremely rapidly _auc h various forms of spray nozzles anwendnar are heated to temperatures between 300 and 480 ° C. The disadvantage of this process, however, is that is, characterized in that by the high gas velocity in the permanent fix the urea through a central tube and the considerable abrasion of the solid catalyst Bubble gas occurs through a particle arranged concentrically around it in the fluidized bed, which is next to the netes, at the same level or just below the Zen catalytic converter wear, also leads to the undesired \ cr- Tralrohr ending jacket tube with a gas 15 impurity de end product leads (^ speed from 40 to 100 or 20 to It has been found that in the case of urea 100 m / sec directly in the fluidized bed to cyanic acid and ammonia soft im leads to be. other due to the different thermo- dynamic relationships with melamine formation 20 roughly in accordance with the aforementioned Austria Patent 275 621 is not comparable, even with Cias velocities are worked below the speed of sound and so the disadvantageous abrasion in the The pyrolysis of solid or liquid urea in inert particles existing fluidized bed avoided Fluidized beds made of inert or catalytically active as can be, if one considers the gasification of liquid seed solids for the purpose of producing urea so that the urea does not melt Cyanic acid, its ammonium salt or melamine comes into contact with surfaces that are under the reaction