METHOD FOR REDUCING AEROSOL EMISSIONS IN A UREA GRANULATION PLANT
1 Assignment
0 Petitions
Accused Products
Abstract
The invention relates to a process for the granulation of a concentrated urea solution whereas the granulation produces a urea granulate and a dust laden air, which is then fed into a dust scrubber which removes the coarser dust with a less concentrated urea solution and which releases a residual air comprising air with ammonia, carbon dioxide water and an aerosol comprising mainly ammonium isocyanate and a part of very fine urea sublimate, whereas the aerosol is then separated off and fed into a isomerisation unit which comprises a stripping where the ammonium isocyanate reacts with steam to form urea which is then redirected into the dust scrubber as a less concentrated urea solution, and the residual air is directed into an acidic scrubber which releases clean air into the atmosphere which finally leads to a recycling of the aerosol of ammonium isocyanate into urea. The invention also relates to a device for carrying out the related process.
-
Citations
26 Claims
-
1-13. -13. (canceled)
-
14. A method for reducing aerosol emissions from a urea granulation plant with the treatment of the resulting scrubber bleeds, comprising:
-
producing urea with a granulator from a concentrated urea solution and an evaporation of the included water, giving urea granulates and an exhaust of dust, ammonia and ammonium isocyanate; subsequently scrubbing or removing the dust; and releasing a first stream of an exhaust of air and ammonia, and a second stream of ammonium isocyanate and water in a following aerosol stage with a specially designed spray and collection pads;
whereinthe second stream of ammonium isocyanate and water is fed into a isomerisation unit where the fraction of ammonium isocyanate is isomerised back to urea, whereas the isomerisation of ammonium isocyanate to urea is carried out in a stripping column with the feeding of low pressure steam to the bottom of the column; and the resulting urea in the stripping column is fed into a liquid phase, and the remaining ammonia and carbon dioxide are released to the head of the column.
-
- 15. The method for reducing aerosol emissions from a urea granulation plant with a recovery of the resulting scrubber bleeds according to claim 15, wherein the liquid phase with the urea from the stripping column is concentrated in a concentration step.
-
23. A device for producing urea granulates comprising:
-
a granulator for the granulation of urea solution; a following scrubber for the removal of dust; and a following aerosol stage for the removal of aerosol with a designed spray systems and collection pads;
whereinthe separated aerosol which consists essentially of ammonium isocyanate is feedable into a isomerisation unit; and the isomerisation unit consists of a stripping column with an off-take for gases at the head of the column and an off-take for a liquid at the bottom of the column. - View Dependent Claims (24, 25, 26)
-
Specification