Title of Invention

METHOD FOR REMOVING AMMONIA AND DUST FROM AN EXHAUST GAS EMITTED DURING THE MANUFACTURE OF FERTILISERS

Abstract A method for removing ammonia and dust from an exhaust gas emitted during the manufacture of fertilisers, especially urea, in which the exhaust gas is introduced into a first washer and a cooling gas is introduced into a second washer and additional water is introduced into one washer and a watery solution is introduced into the other washer, whereby the exhaust gas as well as the cooling gas pass through at least one demister before coming out of the respective washer, is supposed to be further developed in such a way that the exhaust gas load can be significantly reduced. This is achieved, in that the additional water is initially introduced into a fine washing zone of the first washer bordered on the upper side by the demister and on the lower side by a fluid-impermeable separating floor, and sprayed on to the at least one demister and the resulting water solution in the fine water zone is subsequently guided into the second washer.
Full Text Method for Removing Ammonia and Dust from an Exhaust Gas Emitted
During the Manufacture of Fertilisers
The invention relates to a method for removing ammonia and dust from an exhaust gas
emitted during the manufacture of fertilisers, mainly urea, in which the exhaust gas is
introduced into a first washer and a cooling gas is introduced into a second washer, and
additional water is introduced into one washer and a watery solution into the other washer,
whereby the exhaust gas as well as the cooling gas passes through at least one demister
before exiting out of the respective washer.
During manufacture of ammonia-containing fertilisers or in fertilisers that can split ammonia,
e.g. fertilisers containing urea, during the different process stages exhaust gas-flows
containing ammonia and dust get emitted, which have to be purified before discharging into
the atmosphere or recycling into the process. Such exhaust gases occur mainly during
granulation and cooling.
For removing dust from the exhaust gas exiting from the granulation and from the granulated
cooling gas, we know of a generic method of the applicant. For conducting this method, two
washers are foreseen, which are equipped respectively in the upper region with at least one
demister. The exhaust gas stemming from the granulation is introduced into the first washer,
while cooling gas is introduced into the second washer. For purification, additional water
preferably purified or non-purified process water, is introduced into the washer below the
demister in a counter-flow to the cooling gas. The watery solution coming out of the second
washer is subsequently introduced into the first washer, similarly in a counter-flow to the
purifying exhaust gas.
It has been seen in practice that this known method still has scope for improvement. As the
watery solution coming out of the first washer has to be further processed or further used,
there is this endeavour to set the urea concentration in the watery solution as high as possible,
in order to keep the energy consumption for evaporation the exiting watery solution as low as
possible. In the hitherto process however, limits are set for this maximum concentration. The
hitherto maximum value of urea concentration in the watery solution in the first washer is
approximately 30% to 45%; higher concentrations are not possible, as in spite of the demister


it cannot be completely avoided that urea-laden drops remain in the exiting exhaust gas and
cause a corresponding high urea concentration in it.
Therefore, it is the task of this invention to further develop a generic method in such a way
that the exhaust gas load can be considerably reduced.
This task is fulfilled with the help of the invention by a method of the kind mentioned above,
in that the additional water is initially introduced into a fine washing zone of the first washer
bordered on the upper side by the demister and on the lower side by a fluid-impermeable
separating floor, and is sprayed on to the at least one demister, and the watery solution
resulting in the fine washing zone is subsequently guided into the second washer.
Thus, in deviation from the known method, the additional water is initially completely
introduced into the additional fine washing zone provided in the first washer, into which the
drops-laden exhaust gas enters before passing through the demister. On account of the
additional water, a strong dilution takes place in the fine washing zone, so that the urea
concentration of the drops gets significantly reduced. At the same time, there additionally
follows the cleaning of the demister. On account of the strong dilution of the drops it is
possible to significantly increase the urea concentration of the watery solution in the actual
main washing zone of the washer, so that the energy consumption for the subsequent
evaporation of the watery solution can be highly reduced. Besides, by means of conducting
the method in this way it can be achieved that the dust load in the exhaust gas gets reduced
from the hitherto attainable values of 50 mg/m3 to 20 mg/m3.
The watery solution coming out the second washer is guided into the first washer in a known
method, and obviously into the main washing zone of the first washer foreseen below the
separating floor, into which also the exhaust gas enters.
For separating the fine washing zone and the main washing zone of the first washer a bubble
tray is used. Basically, also other separating floors can be used that are fluid-impermeable but
gas-permeable.


In order to reduce the ammonia concentration in the exhaust gas, in another advantageous
extension it is foreseen that an acid is introduced into the fine washing zone of the first
washer. For example, sulphuric acid or nitric acid can be used. Such an acid treatment is
basically known, e.g. from EP 0 440 932 Bl.
In order to energy-wise optimise further processing of the watery solution coming out of the
first washer, it is foreseen that in the main washing zone of the first washer a urea
concentration of 40 - 60 %, preferably 55%, is set. In this way, the energy consumption for
the evaporation can be clearly reduced without this very high urea concentration in the
watery solution leading to problems during purification of the exhaust gas, because, as
already mentioned earlier, in the fine washing zone a strong dilution of the drops entering
into this zone takes place.
The invention is described in details below on the basis of the drawing. The following are
shown:
Fig. 1 A principle scheme for conducting the method; and
Fig.2 A detail of fig. 1 in a special extension.
A plant for conducting the method first has a first washer 1 and a second washer 2. A
preliminary purifying stage 3 is connected before the first washer 1. In the upper region of
the first washer 1 a demister 4 is arranged, just like the demister 5 in the second washer 2.
The first washer 1 is divided into two washing zones, whereby below the demister 4 a fluid-
impermeable but gas-permeable separating floor 12 (e.g. bubble tray) forming a fine washing
zone 14, as well as an outlet 11 are arranged. Below the separating floor 12 the main washing
zone 21 of the first washer 1 is situated.
The above-mentioned plant parts are components of a plant for manufacturing fertilizers,
especially urea, and are connected to a granulator and a cooler that are not shown. Exhaust
gas laden with ammonia and dust is guided out of the not shown granulator, first into the
preliminary purifying stage 3, as indicated by an arrow 6. The exhaust gas passes through the
preliminary purifying stage 3 and is introduced into the main washing zone 21 of the first


washer 1. Similarly, laden cooling gas is directly fed into the second washer, as indicated by
an arrow 7.
Additional water, preferably purified or non-purified process water, is fed directly to the fine
washing zone of the first washer 1, where the water feed line is indicated by
arrows 8, 9. The water feed line enters within the washer 1 below the demister 4 into
spraying heads 10 directed upwards in such a way that the additional water gets sprayed
against the demister and thus cleans it. The additional water gets mixed with the drops
passing through the separating floor 12 and leads to a strong dilution in urea concentration of
the drops, so that the drops reveal a urea concentration of only 1 to 4 %, even when the urea
concentration in the main washing zone 21 lies between 55 to 60 %. In this way, the
additional water gets enriched and comes out as watery solution through the outlet 11, to
which a pipe 13 is connected that enters into the second washer 2, whereby the watery
solution is guided into the second washer 2.
After passing through the preliminary purifying stage 3, the exhaust gas to be purified thus
first enters into the main washing zone 21 of the first washer 1, in which perforated bases 22
or something similar are arranged, and then passes through the separating floor 12 into the
fine washing zone 14, in which on account of mixing with the additional water a strong
dilution and reduction of drops adhering to the exhaust gas takes place. The exhaust gas
subsequently passes through the demister 4 and then comes out purified at the head of the
first washer 1 (arrow 15).
The cooling gas to be purified enters in the lower region (arrow 7) into the second washer 2,
in which similarly perforated bases 23 are arranged, in order to pass in counter-flow through
the introduced watery solution and subsequently through the demister and come out purified
at the head of the second washer (arrow 16).
The respective sump/bottom product in both washers 1 and 2 is circulated in the usual way as
indicated by the corresponding cycles 17 or 18. From the cycle 18 the watery solution is
branched off and fed to the preliminary purifying stage 3 through a pipe 19. From the
preliminary purifying stage 3 watery solution and exhaust gas thus enter into the main
washing zone 21 of the first washer 1.


Due to the significant dilution and purification effect in the fine washing zone 14 it is
possible to set a urea concentration in the watery solution of approximately 60% in the main
washing zone 21 of the first washer 1, i.e. the watery solution coming out of the washer 1
(pipe 24) then has a urea concentration of 60%, so that when compared to the state-of-the-art
technology this watery solution can be evaporated with much lesser energy consumption for
the purpose of further utilisation. In spite of this high urea concentration in the main washing
zone 21, on account of conducting the method with introduction of additional water into the
fine washing zone 14 it is possible to even achieve urea concentrations to the tune of 1 to 4%
in the fine washing zone 14. The urea concentration in the second washer 2 is approximately
10%.
As shown in fig.2, it is additionally foreseen that an acid is introduced into the fine washing
zone 14 for reducing the ammonia load in the exhaust gas, as indicated by an arrow 20. For
this, a portion of the watery solution coming out of the outlet 11 of the first washer 1 is
recycled out of the pipe 13 in the cycle through a pump 25 for introducing the acid into the
fine washing zone 14. As acid, sulphuric acid or nitric acid can be used. Such an acid
treatment is basically known, e.g. from EP 0 440 932 Bl. Addition of acid (flow 20) takes
place in a corrosion-resistant, self-suctioning nozzle after the pump (e.g. blast nozzle) whose
influx is regulated. The pressure line of the pump can be wholly or partly used as drive jet
flow.
This method is basically suitable also alternatively for a washer in which several demisters
are vertically arranged. The additional water is then guided in a suitable manner first into a
fine washing zone of the washer for the exhaust gas coming out of the granulation.


WE CLAIM:
1. Method for removing ammonia and dust from an exhaust gas emitted during
manufacture of fertilizers, especially urea, in which the exhaust gas is introduced into a
first washer (1) and a cooling gas is introduced into a second washer ((2), and additional
water (8,9) is introduced into one washer and watery solution is introduced into the other
washer, whereby the exhaust gas as well as the cooling gas pass through at least one
demister (4,5) before coming out of the respective washer,
characterized in that
the additional water is initially introduced into a fine washing zone (14) of the first
washer bordered on the upper side by the demister and the lower side a fluid-
impermeable separating floor (12) and is sprayed on to the at least one demister (4,5) and
the resulting watery solution in the fine washing zone is subsequently guided into the
second washer.
2. Method as claimed in claim 1, wherein the watery solution coming out of the second
washer is introduced into the main washing zone of the first washer provided below the
separating floor, into which the exhaust gas also enters.

3. Method as claimed in claim 1 or 2, wherein a bubble tray is used as separating floor.
4. Method as claimed in claim 1 or one of the following claims wherein an acid is
introduced into the fine washing zone of the first washer.
5. Method as claimed in claim 1 or one of the following claims wherein in the main
washing zone of the first washer an urea concentration of 40-60%, preferably 55%, is set.


A method for removing ammonia and dust from an exhaust gas emitted during the
manufacture of fertilisers, especially urea, in which the exhaust gas is introduced into a first
washer and a cooling gas is introduced into a second washer and additional water is
introduced into one washer and a watery solution is introduced into the other washer,
whereby the exhaust gas as well as the cooling gas pass through at least one demister before
coming out of the respective washer, is supposed to be further developed in such a way that
the exhaust gas load can be significantly reduced.
This is achieved, in that the additional water is initially introduced into a fine washing zone
of the first washer bordered on the upper side by the demister and on the lower side by a
fluid-impermeable separating floor, and sprayed on to the at least one demister and the
resulting water solution in the fine water zone is subsequently guided into the second washer.

Documents:

01025-kolnp-2006 abstract.pdf

01025-kolnp-2006 assignment.pdf

01025-kolnp-2006 claims.pdf

01025-kolnp-2006 correspondence others.pdf

01025-kolnp-2006 description(complete).pdf

01025-kolnp-2006 drawings.pdf

01025-kolnp-2006 form-1.pdf

01025-kolnp-2006 form-2.pdf

01025-kolnp-2006 form-3.pdf

01025-kolnp-2006 form-5.pdf

01025-kolnp-2006 international publication.pdf

01025-kolnp-2006 international search authority.pdf

01025-kolnp-2006 pct form.pdf

01025-kolnp-2006-abstract-1.1.pdf

01025-kolnp-2006-claims-1.1.pdf

01025-kolnp-2006-correspondence others-1.1.pdf

01025-kolnp-2006-description(complete)-1.1.pdf

01025-kolnp-2006-priority document.pdf

1025-KOLNP-2006-CORRESPONDENCE.pdf

1025-KOLNP-2006-EXAMINATION REPORT.pdf

1025-KOLNP-2006-FORM 18.pdf

1025-KOLNP-2006-FORM 3.pdf

1025-KOLNP-2006-FORM 5.pdf

1025-KOLNP-2006-FORM-27.pdf

1025-KOLNP-2006-GPA.pdf

1025-KOLNP-2006-GRANTED-ABSTRACT.pdf

1025-KOLNP-2006-GRANTED-CLAIMS.pdf

1025-KOLNP-2006-GRANTED-DESCRIPTION (COMPLETE).pdf

1025-KOLNP-2006-GRANTED-DRAWINGS.pdf

1025-KOLNP-2006-GRANTED-FORM 1.pdf

1025-KOLNP-2006-GRANTED-FORM 2.pdf

1025-KOLNP-2006-GRANTED-SPECIFICATION.pdf

1025-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf

1025-KOLNP-2006-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

abstract-01025-kolnp-2006.jpg


Patent Number 249748
Indian Patent Application Number 1025/KOLNP/2006
PG Journal Number 45/2011
Publication Date 11-Nov-2011
Grant Date 08-Nov-2011
Date of Filing 21-Apr-2006
Name of Patentee UHDE GMBH
Applicant Address FRIEDRICH-UHDE-STRASSE 15, 44141 DORTMUND
Inventors:
# Inventor's Name Inventor's Address
1 NIEHUES PAUL KNOSPENWEG 11, 44265 DORTMUND
2 FRANZRAHE, HARALD BODLECKSTRASSE 57, 44289 DORTMUND
PCT International Classification Number B01D 53/58
PCT International Application Number PCT/EP2004/009886
PCT International Filing date 2004-09-04
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 103 46 519.7 2003-10-02 Germany