U.S. patent application number 16/540241 was filed with the patent office on 2019-12-05 for method and device for removing contaminants arising during the production of aliphatic nitrate esters.
This patent application is currently assigned to Josef Meissner GmbH & Co. KG. The applicant listed for this patent is Josef Meissner GmbH & Co. KG. Invention is credited to Jurgen Gebauer, Mirko Handel, Heinrich Hermann, Jurgen Pohlmann.
Application Number | 20190367441 16/540241 |
Document ID | / |
Family ID | 52430154 |
Filed Date | 2019-12-05 |
United States Patent
Application |
20190367441 |
Kind Code |
A1 |
Pohlmann; Jurgen ; et
al. |
December 5, 2019 |
METHOD AND DEVICE FOR REMOVING CONTAMINANTS ARISING DURING THE
PRODUCTION OF ALIPHATIC NITRATE ESTERS
Abstract
The invention relates to a method and to a device for removing
contaminants arising during the production of aliphatic or
alicyclic nitric acid esters, in particular for removing
contaminants from nitrated crude nitric acid esters, which nitrated
crude nitric acid esters arise during the nitration of monovalent
or multivalent aliphatic or alicyclic alcohols capable of
nitration, after the separation of the final nitrating acid, and to
a production system for nitrating monovalent or multivalent
aliphatic alcohols capable of nitration with subsequent
purification of the nitrated nitric acid esters.
Inventors: |
Pohlmann; Jurgen; (Koln,
DE) ; Hermann; Heinrich; (Koln, DE) ; Handel;
Mirko; (Neunkirchen-Seelscheid, DE) ; Gebauer;
Jurgen; (Troisdorf, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Josef Meissner GmbH & Co. KG |
Koln |
|
DE |
|
|
Assignee: |
Josef Meissner GmbH & Co.
KG
Koln
DE
|
Family ID: |
52430154 |
Appl. No.: |
16/540241 |
Filed: |
August 14, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15926406 |
Mar 20, 2018 |
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16540241 |
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14912387 |
Feb 16, 2016 |
10266480 |
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PCT/EP2014/063334 |
Jun 25, 2014 |
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15926406 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 11/0473 20130101;
C07C 201/02 20130101; C07C 203/04 20130101; C07C 203/04 20130101;
B01J 19/1812 20130101; C07C 201/02 20130101 |
International
Class: |
C07C 201/02 20060101
C07C201/02; B01J 19/18 20060101 B01J019/18; B01D 11/04 20060101
B01D011/04; C07C 203/04 20060101 C07C203/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 15, 2013 |
DE |
102013013474.9 |
Oct 2, 2013 |
DE |
102013110952.7 |
Claims
1. A method for removing impurities including residual nitrating
acid from a crude nitric ester obtained in the nitration of
nitratable monohydric or polyhydric aliphatic or cycloaliphatic
alcohols, the method comprising: removing the residual nitrating
acid from the crude nitric ester, via treatment with at least one
first washing medium; introducing the crude nitric ester and at
least one second washing medium into and through at least one
dispersing device for contacting and forming an emulsion of the
crude nitric ester to be purified; introducing the emulsion into
and through a device arranged downstream of the dispersing device,
the device comprising a tube reactor, wherein the tube reactor is
equipped with mixing elements for introducing additional mixing
energy, so the impurities initially present in the crude nitric
ester are at least partially removed during passage of the emulsion
through the tube reactor and are at least partly transferred into
the washing medium and neutralized thereby during passage of the
emulsion through the tube reactor; and separating the nitric ester
from the impurities downstream of the tube reactor, in a separation
device for separating the nitrated products from the washing medium
containing the impurities.
2. The method of claim 1, wherein the mixing elements for
introducing additional mixing energy are static mixing elements
configured as metal plates, as impingement plates, as deflection
plates, as orifice plates, as static mixers or as flow dividers;
wherein the mixing elements are fixed to the inside of the tube
reactor; wherein the pressure drop per mixing element is from 0.2
bar to 3.0 bar; wherein the dispersing device for forming an
emulsion is configured as jet mixer or pump; and wherein the
dispersing device is integrated into the tube reactor or is a
constituent of the tube reactor.
3. A method for the preparation of a nitric ester of a monohydric,
a polyhydric aliphatic, or a cycloaliphatic alcohol via nitration
of the monohydric, the polyhydric aliphatic, or the cycloaliphatic
alcohol to form a crude nitrated product and subsequent
purification of the crude nitrated product formed in the nitration,
wherein the method comprises the steps of: (a) nitrating the
monohydric, the polyhydric aliphatic, or the cycloaliphatic alcohol
utilizing a nitrating acid in a nitration unit including one or
more reaction vessels configured for carrying out a nitration
reaction to form a crude nitrated product; (b) removing the
residual nitrating acid from the crude nitrated product in a first
separation device arranged downstream from the nitration unit and
configured for the removal of the residual nitrating acid to form a
crude nitric ester; (c) washing the crude nitric ester with a
washing medium in a production line arranged downstream of the
first separation device, the production line including a washing
facility for carrying out the washing of the crude nitric ester
including impurities, wherein the washing facility comprises: at
least one dispersing device for contacting and emulsifying the
crude nitric ester to be purified and a washing medium, to provide
an emulsion comprising the crude nitric ester and the washing
medium; and, a tube reactor for introducing the emulsion comprising
the crude nitric ester to be purified and the washing medium and
produced in the dispersing device, wherein the tube reactor is
arranged downstream of the dispersing device and is equipped with
mixing elements for introducing additional mixing energy, so that
the impurities initially present in the crude nitric ester are at
least partially removed during passage of the emulsion through the
tube reactor and the impurities initially present in the crude
nitric ester are at least partly transferred into the washing
medium and neutralized thereby during passage of the emulsion
through the tube reactor; and (d) separating the nitric ester from
the washing medium containing the impurities, in a second
separation device arranged in the production line downstream of the
washing unit.
4. The method of claim 3, wherein washing the crude nitrated
products is carried out in a tube reactor including static mixing
elements comprising metal plates, selected from the group
consisting of impingement plates, deflection plates, orifice
plates, static mixers and flow dividers.
5. The method of claim 3, wherein washing the crude nitrated
products is carried out in a tube reactor having mixing elements
fixed to the inside of the tube reactor.
6. The method of claim 3, wherein washing the crude nitrated
products is carried out in a tube reactor having mixing elements
configured as push-in elements, with the push-in elements inserted
as required according to number and position in the tube
reactor.
7. The method of claim 3, wherein washing the crude nitrated
products is carried out in a tube reactor having mixing elements
configured to introduce a volume-based mixing energy of from 20 to
1000 joule/liter in the tube reactor.
8. The method of claim 3, wherein the washing of the crude nitrated
products is carried out in a tube reactor providing a pressure drop
per mixing element of from 0.2 bar to 3.0 bar.
9. The method of claim 3, wherein the dispersing device included in
the washing facility utilized in washing the crude nitrated
products is configured as jet mixer or pump.
10. The method of claim 3, wherein the dispersing device included
in the washing facility utilized in washing the crude nitrated
products is configured such that it produces a central driving jet
and an annular jet surrounding the driving jet.
11. The method of claim 3, wherein the dispersing device included
in the washing facility utilized in washing the crude nitrated
products is located upstream of the reactor, with the dispersing
device going over into the tube reactor.
12. A method for the preparation of a nitric ester of a monohydric,
a polyhydric aliphatic, or a cycloaliphatic alcohol via nitration
of the monohydric, the polyhydric aliphatic, or the cycloaliphatic
alcohol to form a crude nitrated product and subsequent
purification of the crude nitrated product formed in the nitration,
wherein the method comprises the steps of: (a) nitrating the
monohydric, the polyhydric aliphatic, or the cycloaliphatic alcohol
utilizing a nitrating acid in a nitration unit including one or
more reaction vessels configured for carrying out a nitration
reaction to form a crude nitrated product; (b) removing the
residual nitrating acid from the crude nitrated product in a first
separation device arranged downstream from the nitration unit and
configured for the removal of the residual nitrating acid to form a
crude nitric ester; (c) washing the crude nitric ester with a
washing medium in a production line arranged downstream of the
first separation device, the production line including a washing
facility for carrying out the washing of the crude nitric ester
including impurities, wherein the washing facility comprises: at
least one dispersing device for contacting and emulsifying the
crude nitric ester to be purified and a washing medium, to provide
an emulsion comprising the crude nitric ester and the washing
medium; and, a tube reactor for introducing the emulsion comprising
the crude nitric ester to be purified and the washing medium and
produced in the dispersing device, wherein the tube reactor is
arranged downstream of the dispersing device and is equipped with
mixing elements for introducing additional mixing energy, so that
the impurities initially present in the crude nitric ester are at
least partially removed during passage of the emulsion through the
tube reactor and the impurities initially present in the crude
nitric ester are at least partly transferred into the washing
medium and neutralized thereby during passage of the emulsion
through the tube reactor; (d) introducing the crude nitric ester,
and the washing medium into a stirred vessel downstream of the
washing facility to increase the contact and residence time between
the crude nitric ester and the washing medium; and (e) separating
the nitric ester from the washing medium containing the impurities,
in a second separation device arranged in the production line
downstream of the stirred vessel.
13. The method of claim 12, wherein washing the crude nitrated
products is carried out in a tube reactor including static mixing
elements comprising metal plates, selected from the group
consisting of impingement plates, deflection plates, orifice
plates, static mixers and flow dividers.
14. The method of claim 12, wherein washing the crude nitrated
products is carried out in a tube reactor having mixing elements
fixed to the inside of the tube reactor.
15. The method of claim 12, wherein washing the crude nitrated
products is carried out in a tube reactor having mixing elements
configured as push-in elements, with the push-in elements inserted
as required according to number and position in the tube
reactor.
16. The method of claim 12, wherein washing the crude nitrated
products is carried out in a tube reactor having mixing elements
configured to introduce a volume-based mixing energy of from 20 to
1000 joule/liter in the tube reactor.
17. The method of claim 12, wherein the washing of the crude
nitrated products is carried out in a tube reactor providing a
pressure drop per mixing element of from 0.2 bar to 3.0 bar.
18. The method of claim 12, wherein the dispersing device included
in the washing facility utilized in washing the crude nitrated
products is configured as jet mixer or pump.
19. The method of claim 12, wherein the dispersing device included
in the washing facility utilized in washing the crude nitrated
products is configured such that it produces a central driving jet
and an annular jet surrounding the driving jet.
20. The method of claim 12, wherein the dispersing device included
in the washing facility utilized in washing the crude nitrated
products is located upstream of the reactor, with the dispersing
device going over into the tube reactor.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This patent application is a continuation of U.S.
application Ser. No. 15/926,406 entitled "METHOD AND DEVICE FOR
REMOVING CONTAMINANTS ARISING DURING THE PRODUCTION OF ALIPHATIC
NITRATE ESTERS" filed on Mar. 20, 2018, which is a continuation of
U.S. application Ser. No. 14/912,387, filed on Feb. 6, 2016, which
issued as U.S. Pat. No. 10,266,480 on Apr. 23, 2019, and which is a
National Stage filing of International Application PCT/EP
2014/063334, filed Jun. 25, 2014, claiming priority to DE 10 2013
013 474.9 filed Aug. 15, 2013, and to DE 10 2013 110 952.7 filed
Oct. 2, 2013. The subject application claims priority to U.S.
patent application Ser. No. 15/926,406, patent application Ser. No.
14/912,387 issued as U.S. Pat. No. 10,266,480, PCT/EP 2014/063334,
DE 10 2013 013 474.9 and DE 10 2013 110 952.7 and incorporates all
by reference herein, in their entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the technical field of the
preparation of nitric esters (also referred to synonymously as
nitroesters or nitrate esters) of monohydric or polyhydric
(cyclo)aliphatic alcohols (i.e. in other words, the nitration of
monohydric or polyhydric aliphatic or cycloaliphatic alcohols to
form the corresponding nitric esters), in particular the
purification of the crude nitrated nitric esters obtained after
removal of the residual nitrating acid.
[0003] The present invention relates in particular to a process for
removing impurities (in particular unreacted starting materials,
reaction by-products, nitrating acid and reaction products thereof,
e.g. nitrogen oxides or nitrous acid, etc.) obtained in the
preparation of aliphatic or cycloaliphatic nitric esters, in
particular a process for removing impurities from crude nitrated
nitric esters obtained in the nitration of nitratable monohydric or
polyhydric aliphatic or cycloaliphatic alcohols after removal of
the residual nitrating acid.
[0004] Furthermore, the present invention relates to an apparatus
or plant for removing impurities obtained in the preparation of
aliphatic or cycloaliphatic nitric esters, in particular an
apparatus or plant for removing impurities from crude nitrated
nitric esters obtained in the nitration of nitratable monohydric or
polyhydric aliphatic or cycloaliphatic alcohols after removal of
the residual nitrating acid.
[0005] Finally, the present invention relates to a production plant
for the nitration of nitratable aliphatic or cycloaliphatic
alcohols with subsequent purification of the crude nitrated
products (i.e. with subsequent purification of the resulting crude
nitric esters) or a production plant for the preparation of nitric
esters of monohydric or polyhydric aliphatic or cycloaliphatic
alcohols with subsequent purification of the crude nitrated
products.
[0006] Aliphatic nitroesters (also referred to synonymously as
aliphatic nitric esters, aliphatic nitrate esters or the like),
e.g. pentaerythrityl tetranitrate (PETN), glyceryl trinitrate
(NGL), ethylene glycol dinitrate (EGDN), ethylhexyl nitrate (EHN),
etc., are generally prepared in a continuously operated plant (e.g.
in the case of NGL, EGDN or mixtures thereof by the process of
Schmid-Meissner or Biazzi, by the injector process or by the N.A.B.
process of Nielsen and Brunnberg or in the case of EHN by a
modified process as described in EP 1 792 891 A1) by reaction of
the corresponding alcohol (e.g. pentaerythritol, glycerol, ethylene
glycol, ethylhexylethanol, etc.) with nitric acid either directly
and alone or else in the presence of sulfuric acid as catalyst and
water-binding agent. The nitration of the alcohols (i.e. the
reaction thereof to form nitric esters) is generally carried out in
the liquid phase, either as pure substance or else as a mixture or
else in solution in inert, water-immiscible solvents.
[0007] The resulting crude nitroesters (hereinafter also referred
to synonymously as crude nitric esters, crude nitrate esters, crude
nitrated products or the like) have to be subjected before further
processing thereof to multistage washing and additional
purification steps in order to remove impurities which are still
dissolved or suspended in the crude nitroesters, e.g. sulfuric
acid, nitric acid, nitrous gases, etc., and by-products from the
oxidative degradation of the starting alcohols, and thus improve
the stability of the nitroesters, which are largely highly
sensitive explosive materials.
[0008] The washing of the crude nitroesters in order to remove the
dissolved and suspended acids of the nitration mixture and other
acidic impurities or impurities which can be extracted in another
way by the washing medium usually consists of three steps (see, for
example, T. Urbanski, Vol. 2, pages 97 ff., in particular figures
43, 44, 59 and 60, Pergamon Press, Reprint 1985). Water is usually
employed as washing medium for this purpose. Washing is generally
carried out as a liquid/liquid wash using the nitroester which is
liquid at the washing temperature or as a solution of the
nitroester in a suitable solvent.
[0009] This three-stage wash of the crude nitrated products (i.e.
the crude nitroesters or nitric esters) usually comprises the
following steps: [0010] 1. an acid wash ("acid wash") with water to
remove the dissolved and suspended mineral acids, e.g. sulfuric
acid, nitric acid and nitrous gases; [0011] 2. a basic or alkali
wash ("basic wash" or "alkali wash") in the presence of a base,
e.g. sodium carbonate (soda), sodium bicarbonate, ammonia, sodium
hydroxide, potassium hydroxide, etc., in particular for removing
the mineral acids still present in the nitrate ester after the
first wash and residues of nitrous gases and other weakly acidic
impurities from oxidative decomposition of the alcohol used or
other aliphatic or cyclic hydrocarbons which were present as traces
in the starting alcohol; [0012] 3. a wash with water ("neutral
wash") for removing the residual traces of alkali and for further
in traces in the product.
[0013] However, washing of the crude nitrate esters directly with
soda solution, i.e. with omission of the "acid wash" stage, is
sometimes also practiced and is prior art (see, for example, T.
Urbanski, Vol. 2, Biazzi process, pages 107 ff., in particular FIG.
48, Pergamon Press, Reprint 1985; T. Urbanski, Vol. 4, page 328,
Pergamon Press 1984; B. Brunnberg, Industrial and Laboratory
Nitration, ACS Symposium Series No. 22 (Editors: L. F. Albright and
H. J. T. Hanson), page 341, Washington DC, 1976).
[0014] The objective of these washing steps is to obtain not only a
pure product having high stability but also very little wastewater
per metric ton of product; the washed-out impurities and the
nitrate ester (traces) still present as a function of their
solubility should be present in the wastewater in such amounts that
they can be disposed of inexpensively.
[0015] To minimize the amount of water required for this wash and
to recover the acids dissolved in the crude nitrate esters in
appreciable amounts, specially nitric acid, the wash can, as
described, for example, in DE-C 505 424 and DE-C 546 718, be
carried out using a reduced amount of washing water in the first
washing step ("acid wash") in such a way that a washing acid having
a content of nitric acid of from 20 to 60% strength or of from 35
to 55% and a content of sulfuric acid of up to 15% is obtained.
This washing acid can be worked up directly or together with the
residual nitrating acid.
[0016] Furthermore, washing can, for example, be carried out in
countercurrent by feeding the washing water from the third washing
step ("neutral wash") either directly or after addition of bases to
the washing of the nitrate ester in the second washing step
("alkali wash") and introducing this washing water from the second
washing step (i.e. the alkaline washing stage) into the first
washing step (i.e. the acid wash) (cf. DE-C 505 424 and DE-B 1 135
876).
[0017] It is usual, for reasons of safety, to give preference to
using injectors (jet pumps) as conveyors using the washing medium
as driving medium between the individual washing steps in these
three washing steps and carrying out the actual wash in
air-operated washing columns. After washing is complete, the
purified nitrate ester is transported as emulsion with water into a
storage facility or to further processing.
[0018] DE-C 710 826 describes a process in which the three-stage
washing of nitrate esters of polyhydric alcohols is carried out in
countercurrent in washing columns stirred by means of air, with the
nitrate esters being premixed with the washing liquid in injectors
and this premixed emulsion being fed by means of air injectors into
the washing column. At the end of the wash, the washed nitrate
ester is, after phase separation by means of injectors which are
operated using circulated driving water, transported to the storage
facility. In the washing processes documented in T. Urbanski, Vol.
2, pages 97 ff., in particular FIGS. 59 and 60, Pergamon Press,
Reprint 1985, too, the washing process described in DE-C 710 826 is
used in combination with the injector process.
[0019] To remove a material from a mixture of materials by
extraction/washing in a material which is immiscible with this
mixture of materials, as in the present case of the mixture of
liquid nitrate esters/impurities with water, it is necessary, in
order to achieve successful extraction of the impurities from the
mixture of materials, to disperse the two immiscible phases in one
another, whether as oil-in-water emulsion (O/W emulsion) or as
water-in-oil emulsion (W/O emulsion), in such a way that there is a
sufficiently large exchange area between the immiscible phases over
a sufficiently long time for the partition equilibrium for the
materials to be extracted to be reached and the extracted material
in the extract phase to be able to be altered by means of
subsequent reactions in such a way that backextraction is no longer
possible.
[0020] It is known that injectors or jet pumps are suitable for
mixing miscible liquids but that injectors are unsuitable as
dispersing device for dispersing two immiscible liquids in one
another. The droplet sizes generated in the injector are not small
enough for good washing. The stability of the emulsion produced is
too low and the exchange area required for optimal mass transfer
is, in combination with the short residence time in the mixture
tube of the injector (about 1 second), therefore too small.
[0021] The relatively unstable nitrate ester emulsions in water
which are produced using injectors therefore tend to undergo quick
phase separation. This is particularly problematical for transport
of such emulsions over relatively long distances. As DE-C 973 718
appears to describe, if an emulsion is conveyed alone, separation
into explosive oil and water easily takes place in the long
transport pipes having a small inclination. It is possible for a
contiguous explosive oil layer to be formed, and this makes
detonation throughout possible.
[0022] To prevent coalescence of the nitrate esters after leaving
the injector and especially to prevent detonation throughout of
explosive oil which has separated out during transport of the
emulsion, methods which allow the emulsion of the nitrate ester in
water to be stabilized and the formation of liquid threads of
nitrate esters which have separated out, which are capable of
detonation throughout, to be prevented have been reported, for
example as described in U.S. Pat. No. 2,140,897 A, DE-C 820 575,
DE-C 973 718, DE-B 1 058 093, DE-A 1 571 221 or DE-A 2 055 093.
This is preferably brought about by mixing in of air or by
re-emulsification using air or else by interrupting the emulsion
stream with water or air.
[0023] However, it is known that gas bubbles in the liquid nitrate
ester can not only significantly increase its shock sensitivity,
caused by adiabatic compression (cf. DE-A 1 571 221), but that the
two-phase mixtures comprising additionally drawn-in air, as
previously described in DE-B 1 058 039, can lead to such stable
emulsions that phase separation is possible only by use of
centrifugal separators.
[0024] This risk of air inclusion in the liquid nitrate ester can
be prevented by the measures described in DE-A 1 571 221 and DE-A 2
055 093. Interruption of the homogeneous emulsion column in the
transport conduit by a nitrate ester-free water column effectively
prevents formation of an explosive thread capable of detonation
throughout by rapid coalescence of the nitrate ester emulsified in
the injector.
[0025] The relatively unstable dispersions of nitrate ester in
washing water or vice-versa which are produced by the injector with
its relatively low dispersing power and the resulting nonoptimal
exchange area for effective washing (additionally in combination
with the very short residence times in the mixing region of the
injector) allow only incomplete removal of the impurities in the
nitrate ester to be purified. In order to achieve the desired
purities, the injectors are therefore coupled with residence
vessels with active dispersing.
[0026] For this reason, air-operated washing columns (DE-C 710 826)
in combination with injectors as transport means or cascades of
stirred vessels in combination with injectors (T. Urbanski, Vol. 4,
page 328, in particular FIG. 46, Pergamon Press 1984) are usually
used as washing apparatuses for washing the nitroesters to be
purified in the individual washing stages. The use of the
air-stirred washing columns is complicated and expensive and is no
longer in accordance with present-day safety standards according to
which the presence of air bubbles in the nitrate ester should be
avoided (DE-A 1 571 221). Multistage cascades of stirred vessels
are also complicated and expensive.
[0027] The use of injectors alone, i.e. without residence vessel,
as proposed in DE-B 1 039 049 is also complicated and expensive. In
order to achieve optimal purification by means of injectors without
residence vessel and additional dispersing devices, each washing
step has to be carried out in a plurality of stages in order to be
able to obtain the desired purity and stability for further
processing of the nitrate ester.
[0028] The emulsion transport of nitrate esters, as described in
DE-A 1 571 221 and in DE-A 2 055 093, is relatively unsuitable as
additional washing stage because it has only at most a polishing
effect in order to remove traces of washing medium which have been
carried as microemulsion from the preceding washing stages because
of its relatively unstable emulsion with relatively large droplets
produced by an injector.
[0029] Overall, the processes and plants for purifying nitrate
esters which are known from the prior art either do not operate
with high efficiency or else they are no longer satisfactory from
the point of view of modern safety standards.
BRIEF SUMMARY OF THE INVENTION
[0030] It is therefore an object of the present invention to
provide a process and an apparatus for removing impurities obtained
in the preparation of aliphatic nitrate esters, in particular for
removing impurities from crude nitrated nitrate esters obtained in
the nitration of nitratable monohydric or polyhydric aliphatic
alcohols after removal of the residual nitrating acid, and also a
(production) plant for the nitration of nitratable monohydric or
polyhydric aliphatic alcohols with subsequent purification of the
nitrated nitric esters, with the abovementioned problems and
disadvantages occurring in connection with the prior art being at
least largely avoided.
[0031] In particular, it is an object of the present invention to
provide a process and an apparatus or plant suitable for carrying
out this process, by means of which efficient purification of the
nitrate esters as are obtained from the nitration of monohydric or
polyhydric alcohols after removal of the residual nitrating acids
can be made possible.
[0032] A further object of the present invention is to carry out
the washing of the crude nitrate esters which result after removal
of the residual nitrating acid or solutions thereof in inert
solvents, in which significant amounts of impurities, for example
entrained nitrating acid, dissolved sulfuric acid, nitric acid,
nitrous gases, degradation products from the oxidative degradation
of the starting alcohols, etc., can be present, in one stage in
each washing step in such a way that the washed nitrate esters are
free of acids and water-soluble and acidic residues from the
oxidative degradation of the starting alcohol to be nitrated and/or
of the product, so that the product which has been treated in this
way meets the respective requirements in terms of its stability,
other safety-related requirements and further product
specifications and safety in the plant thus increases as a result
of a further reduction in the amounts of nitrate esters in the
plant and, finally, the complication and costs associated therewith
are thus considerably lower than in the previously utilized
processes and apparatuses of the prior art.
[0033] The objects indicated above are achieved according to the
invention by a process as claimed herein; further, advantageous
further developments and embodiments of the process of the
invention are subject matter of the dependent claims relating
thereto.
[0034] The present invention further provides an apparatus or a
plant as claimed in the relevant independent claim (secondary
claim); further advantageous developments and embodiments of this
aspect of the invention are subject matter of the dependent claims
relating thereto.
[0035] In addition, the present invention provides a production
plant as claimed in the relevant independent claim (secondary
claim); further advantageous developments and embodiments of this
aspect of the invention are subject matter of the dependent claims
relating thereto.
[0036] It goes without saying that embodiments, variants,
advantages or the like which are indicated below for only one
aspect of the invention in order to avoid unnecessary repetition
also apply analogously to the other aspects of the invention.
[0037] Furthermore, it goes without saying that when values,
numbers and ranges are given, the respective values, numbers and
ranges indicated do not constitute a restriction; in addition, it
will be obvious to a person skilled in the art that, depending on
an individual case or depending on the use, the ranges or figures
indicated can be deviated from without going outside the scope of
the present invention.
[0038] In addition, all values and parameters or the like indicated
below can in principle be measured or determined using standardized
or explicitly indicated methods of determination or else by the
methods of determination with which a person skilled in this field
will be familiar per se.
[0039] This having been said, the present invention will be
described in more detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 provides a schematic depiction of a single-stage wash
for crude nitrate esters according to the process of the invention
or using the apparatus of the invention;
[0041] FIG. 2A provides a detailed depiction of the mixing device
SMn,1 of the apparatus illustrated in the schematic depiction of
the process of the invention in FIG. 1, where the mixing device is
a jet pump;
[0042] FIG. 2B provides a detailed depiction of the mixing device
SMn,1 of the apparatus as per the schematic depiction of the
process of the invention in FIG. 1, where the mixing device is a
jet mixer;
[0043] FIG. 2C provides a detailed depiction of an arrangement of a
series of static mixing elements, Mn,2, Mn,3, Mn,4, Mn,m--1, Mn,m
and Mn,m+1 distributed over the total length of the tube reactor
illustrated in FIG. 1;
[0044] FIG. 3 provides a schematic depiction of a process flow of
the process of the invention or a schematic depiction of the
apparatus or plant of the invention as per a preferred working
example of the invention for the usual three washing stages for
washing nitrate esters;
[0045] FIG. 4 provides a schematic depiction of a production plant
according to the invention for the nitration of nitratable
monohydric and polyhydric alcohols with subsequent washing of the
resulting nitrate esters as per a preferred working example of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0046] The present invention therefore provides, according to a
first aspect of the present invention, a process for removing
impurities obtained in the preparation of aliphatic or
cycloaliphatic nitric esters (nitrate esters or nitroesters), in
particular a process for removing impurities from crude nitric
esters obtained in the nitration of nitratable monohydric or
polyhydric aliphatic or cycloaliphatic alcohols after removal of
the residual nitrating acid, by treatment with at least one washing
medium, wherein the process comprises the following process steps:
[0047] (a) the crude nitric esters (i.e. the crude nitrated
products obtained after removal of the residual nitrating acid) are
firstly brought into contact with a washing medium, with the crude
nitric esters and the washing medium being dispersed in one another
in such a way that an emulsion results (i.e. in other words, an
emulsion or dispersion of firstly crude nitrated products and
secondly washing medium is produced in this first process step
(a)); and [0048] (b) the resulting emulsion is subsequently fed
into a tube reactor which is equipped with mixing elements, in
particular for introducing additional mixing energy, so that the
impurities initially present in the crude nitric esters are at
least partly removed during passage of the emulsion through the
tube reactor and/or so that the impurities initially present in the
crude nitric esters are at least partly transferred into the
washing medium and/or neutralized thereby during passage of the
emulsion through the tube reactor.
[0049] The process of the invention is thus outstandingly suitable
for purifying crude nitrated products obtained in the nitration of
nitratable monohydric or polyhydric aliphatic alcohols after
removal of the residual nitrating acid (i.e. in other words, for
purifying the resulting crude nitric esters).
[0050] The principle of the process of the invention is, inter
alia, that the crude nitrate esters which come from the nitration
and still contain significant amounts of impurities are, after
removal of the residual nitrating acid (e.g. in a separator), are
firstly brought into contact with a washing medium and the mixture
of nitrate ester to be purified and washing medium is converted
into an emulsion or dispersion and the resulting emulsion or
dispersion is subsequently fed into a tube reactor so that the
impurities initially present in the nitrate esters to be purified
are transferred into the washing medium or neutralized thereby and
a purified nitrate ester is formed in this way.
[0051] Typical impurities to be removed encompass, for example,
unreacted starting materials (i.e. in particular, unreacted
monohydric or polyhydric aliphatic or cycloaliphatic starting
alcohols and unreacted starting mineral acids, especially nitric
acid and possibly sulfuric acid, if used as starting material) and
reaction by-products (in particular reaction products of nitric
acid, e.g. nitrous acid, nitrous gases, etc., and reaction
by-products of the starting alcohols, e.g. oxidation products such
as carboxylic acids, aldehydes, ketones, degradation or
dissociation products, carbon dioxide, etc.).
[0052] As the applicant has discovered in a completely surprising
way, the use of a tube reactor with additional mixing elements, in
combination with an upstream dispersing or emulsifying device,
leads to particularly good mixing and particularly intimate and
fine dispersion of firstly washing medium and secondly nitrate
esters to be purified or solutions thereof being able to be
achieved, so that the impurities can be removed completely or at
least essentially completely in this way in a single process step
(namely during the treatment in the tube reactor).
[0053] In contrast to the prior art, further complex process steps
for purifying the crude nitroester are thus avoided in an efficient
way without impairment of quality having to be accepted in the
purification of the crude nitrate ester. The required safety
standards are also ensured by the process of the invention.
[0054] The tube reactor with additional mixing elements used with
the washing medium according to the invention for the treatment of
the crude nitrate ester surprisingly ensures, in combination with
the upstream dispersing device for producing the starting emulsion
of washing medium and crude nitroester, such intimate and fine
dispersion of firstly crude nitroester and secondly washing medium
that all or at least essentially all impurities are transferred
into the washing medium or neutralized thereby during the tube
reactor treatment as per process step (b), so that they can
subsequently (i.e. after conclusion of process step (b)) be
separated off together with the washing medium from the then
purified nitrate ester.
[0055] It has surprisingly been found that it is possible within
the framework of the present invention to successfully carry out
washing of nitrate esters in virtually one stage, even at a high
loading with impurities such as nitrating acid, nitric acid, etc.,
and by means of a simple and inexpensive combination of jet pumps
(injectors) or jet mixers (jet mixing devices), or else other
dispersing devices, in combination with additional devices such as
static mixers, orifice plates, etc., in the downstream tube
reactor, which makes it possible not only to introduce a precisely
defined quantity of mixing energy into the mixture of the
immiscible phases but also ensure a residence time which allows
even slow subsequent reactions to proceed virtually quantitatively.
The emulsions of the organic phase to be purified in the washing
medium (O/W type) or of the washing medium in the organic phase
(W/O type) which can be produced thereby provide the interfacial
area between the nitrate ester to be washed and washing medium
which is required for effective and optimal mass transfer.
[0056] A further special feature of the present invention is that
the tube reactor is equipped with mixing elements, in particular
static mixing elements, for introducing additional mixing energy
(where the mixing elements can, for example, be configured as
plates, in particular impingement or deflection plates, as orifice
plates, as static mixers or as flow dividers). This leads to the
original droplet size distribution not only being maintained but
also being set in such a way that the impurities initially present
in the crude nitrated products are completely transferred into the
washing medium and/or neutralized thereby during passage of the
emulsion through the tube reactor.
[0057] As regards the aliphatic nitric ester (nitrate ester) to be
purified, this can be selected from among any nitric esters of
monohydric or polyhydric aliphatic alcohols. In particular, the
nitric ester to be purified can be selected from among (i) nitric
esters of aliphatic or cycloaliphatic monoalcohols, in particular
of linear or branched aliphatic or cycloaliphatic monoalcohols, in
particular of hexanols, heptanols, octanols, ethylhexyl alcohol and
cyclohexanol; (ii) nitric esters of dihydric aliphatic alcohols, in
particular of ethylene glycol and propylene glycol and oligomers
and polymers thereof, e.g. ethylene diglycol or propylene diglycol,
ethylene triglycol or propylene triglycol and polyethylene glycol
or polypropylene glycol; (iii) nitric esters of trihydric aliphatic
alcohols, in particular of trimethylolethane and glycerol; (iv)
nitric esters of tetrahydric or polyhydric aliphatic alcohols, in
particular of pentaerythritol and dipentaerythritol.
[0058] As indicated above, the tube reactor used in process step
(b) is equipped with mixing elements for introducing additional
mixing energy. In this way, the original droplet size distribution
can not only be maintained but can be set in such a way that the
impurities initially present in the crude nitrated products are
transferred into the washing medium or neutralized thereby during
passage of the emulsion through the tube reactor.
[0059] In particular, the mixing elements present in the tube
reactor are static elements, i.e., in particular, the mixing
elements are configured as static mixing elements.
[0060] In a particular embodiment, the mixing elements, in
particular the static mixing elements, can be fixed to the inside
of the tube reactor, in particular be joined to the interior walls
of the tube reactor, preferably permanently or else releasably.
[0061] In a further particular, alternative embodiment, the mixing
elements can be configured as push-in elements.
[0062] Here, the push-in elements can, if necessary as a function
of the number and/or position, be inserted into the tube reactor or
be positioned in the tube reactor.
[0063] In particular, the mixing elements can be configured as
plates, in particular impingement or deflection plates, as orifice
plates, as static mixers or as flow dividers.
[0064] In a further embodiment, from 1 to 15 mixing elements, in
particular from 2 to 15 mixing elements, preferably from 2 to 10
mixing elements, particularly preferably from 2 to 5 mixing
elements, are arranged in the tube reactor. This leads to
particularly good emulsification of crude products to be purified
and washing medium.
[0065] In this context, it is also advantageous for sufficient
mixing energy for mixing crude products and washing medium to be
provided by the mixing elements in the tube reactor. In this
context, it is particularly advantageous for a total mixing energy
(i.e. volume-based mixing energy) of from 20 to 1000 joule/liter,
preferably from 25 to 500 joule/liter, particularly preferably from
30 to 200 joule/liter, to be introduced in the tube reactor.
[0066] In this context, the pressure drop per mixing element should
be from 0.2 bar to 3.0 bar, preferably from 0.3 to 1.5 bar,
particularly preferably from 0.3 to 0.8 bar.
[0067] Particularly suitable mixing elements are static mixing
elements, especially in the form of static mixers. These are
devices for the mixing of fluids, in which the flow motion alone
brings about mixing and which do not have moving elements. They
consist of flow-influencing elements in a tube; these alternately
divide the stream of material and then combine it again, as a
result of which mixing is achieved.
[0068] According to the invention, it is thus provided for the tube
reactor for carrying out process step (b) to be equipped with
mixing elements, in particular for introducing additional mixing
energy, in order to prevent coalescence of the washing emulsion
after a short time and thus incomplete extraction of the impurities
to be removed from the nitrate ester to be purified; in this way,
particularly good purification results can be obtained since
further improved, particularly intimate dispersion of firstly
washing medium and secondly nitrate ester to be purified can be
achieved and maintained over the entire length of the tube reactor
by means of the additional mixing elements. The additional mixing
elements, preferably distributed over the tube reactor, can be, in
particular, metal plates, in particular impingement or deflection
plates, orifice plates, static mixers, flow dividers or the like,
in order to maintain the emulsion of the O/W or W/O type. According
to the invention, preference is given to from 1 to 15 mixing
elements, in particular from 2 to 15 mixing elements, preferably
from 2 to 10 mixing elements, particularly preferably from 2 to 5
mixing elements, being present in the tube reactor; these mixing
elements can be distributed over the entire length of the tube
reactor. The mixing elements can preferably be inserted according
to requirements as push-in elements into the tube reactor.
[0069] As regards the production of the emulsion or dispersion in
process step (a), this is generally effected by means of a suitable
dispersing or emulsifying device, in particular by means of a
suitable mixing device.
[0070] For the purposes of the present invention, it is possible to
use, for example, a jet mixer or a pump, in particular a jet pump
(injector), as dispersing or emulsifying device, in particular as
mixing device.
[0071] A jet pump (injector) is a pump in which the pumping action
is produced by a liquid jet ("driving medium") which draws in,
accelerates and compresses/transports another medium ("suction
medium") by momentum exchange, as long as it is under sufficient
pressure. The term injector usually refers to a jet pump which
generates a superatmospheric pressure which thus has a
predominantly compressing action.
[0072] For the purposes of the present invention, the dispersing or
emulsifying device, in particular the mixing device, can produce,
in particular, a driving jet (central jet) and an annular jet
surrounding the driving jet. Here, preference is given to the
driving jet being formed by the washing medium and the annular jet
being formed by the crude nitric ester to be purified.
[0073] In a particular embodiment, a jet mixer or a jet pump
(injector) is used as dispersing or emulsifying device, in
particular as mixing device. In particular, the jet mixer or the
jet pump can produce a preferably central driving jet and a medium
surrounding the driving jet, in particular in the form of an
annular jet, with the driving jet preferably being formed by the
washing medium and the annular jet preferably being formed by the
crude nitric esters to be purified (with the converse mode of
operation also being possible in principle, i.e. the crude nitric
ester to be purified as driving jet and washing medium as annular
jet, although this embodiment is less preferred).
[0074] As jet mixers or jet pumps, it is in principle possible to
use all types of jet mixers or jet pumps which allow the nitrate
ester to be washed or the washing medium to be injected with high
relative velocity by means of the central driving jet as free jet,
which can in principle consist of either the washing medium or the
nitrate ester to be washed, in such a way that either the nitrate
ester to be washed is dispersed in the washing medium or the
washing medium is dispersed in the nitrate ester to be washed as
emulsion with high interfacial area. Apparatuses of this type are
described, for example, in Ullmann's Encyclopedia of Industrial
Chemistry, 2003, 5th Ed., Vol. B4, pages 87/88 and 565 to 571, or
else in Perry's Chemical Engineers' Handbook, McGraw-Hill Book
Company, 1984, 6th edition, pages 5-21 to 5-23, or else in the
German patent document DE-A 2 151 206.
[0075] As indicated above, the (central) driving jet in the jet
mixer can be the washing medium and the surrounding medium can be
the crude nitrate ester to be purified; however, as an alternative,
the (central) driving jet can also be formed by the crude nitrated
product to be purified and the medium surrounding the (central)
driving jet can be formed by the washing medium. Both alternative
embodiments lead to the desired result. However, preference is
given according to the invention to the (central) driving jet in
the jet mixer being the washing medium and the surrounding medium
being the crude nitrate ester to be purified.
[0076] Particularly good results in respect of the purification of
the crude products to be purified are obtained when the dispersing
or emulsifying device, in particular the mixing device, produces a
driving jet (central jet) and an annular jet surrounding the
driving jet (where the driving jet is preferably formed by the
washing medium and the annular jet is preferably formed by the
crude nitric esters to be purified), where the ratio of the
velocities between the driving jet and the annular jet surrounding
the driving jet is set in the range from 1:6 to 35:1, preferably in
the range from 1:2 to 25:1, particularly preferably in the range
from 1:1 to 12:1. In this way, particularly intimate and fine
dispersion of firstly washing medium and secondly crude product to
be purified and consequently particularly efficient purification
are achieved.
[0077] The flow velocity of the emulsion or dispersion composed of
washing medium and crude products in the tube reactor (i.e.
downstream of the dispersing device) should be set in the range
from 0.1 to 15.0 m/s, preferably from 0.5 to 10 m/s.
[0078] In an embodiment of the present invention, it can be
provided for the dispersing or emulsifying device, in particular
the mixing device, used in process step (a) to be installed
upstream, in particular immediately upstream, of the tube reactor.
In a particular variant of this embodiment, it can be provided for
the dispersing or emulsifying device, in particular the mixing
device, to go over into the tube reactor.
[0079] However, it is equally possible for the dispersing or
emulsifying device, in particular the mixing device, to be
integrated into the tube reactor or be a constituent of the tube
reactor. For this purpose, the dispersing or emulsifying device
can, for example, be arranged in the upper or upstream part of the
tube reactor. Such an embodiment is, in particular, possible when
the dispersing device, in particular the mixing device, is
configured as jet mixer or as jet pump (injector).
[0080] As regards the residence time of the emulsion of firstly
washing medium and secondly crude nitrate ester in the tube reactor
(washing apparatus) during process step (b), this can vary within a
wide range. Particular preference is given to the residence time in
the tube reactor being from 0.05 to 130 seconds, preferably from
0.1 to 70 seconds, particularly preferably from 1 to 35 seconds.
Particularly good washing results are achieved in this way, since
firstly a sufficient minimum residence time and secondly also an
economical throughput are ensured.
[0081] In the purification, the mass and phase ratios between crude
nitrated products to be purified and washing medium are also of
importance, and can vary within a wide range.
[0082] Particularly good results are obtained when the mass ratio
between crude nitric esters to be purified and washing medium, in
particular freshly added washing medium, is set in the range from
250:1 to 1:20, preferably in the range from 120:1 to 1:8,
particularly preferably in the range from 12:1 to 1:3.
[0083] Likewise, particularly good results are obtained when the
mass ratio between crude nitric esters to be purified and washing
medium in the tube reactor and/or washing apparatus is set in the
range from 30:1 to 1:6, preferably in the range from 15:1 to 1:5,
particularly preferably in the range from 6:1 to 1:3.
[0084] Setting of the mass or phase ratio is achieved by
circulation of the washing medium after phase separation. This
ensures firstly an optimal exchange area between organic phase and
washing medium and secondly a very short time for phase separation
in the phase separation apparatus.
[0085] The washing of the crude nitrate esters can usually be
carried out as a liquid/liquid wash in pure form, or else in
admixture with an additional inert solvent. These additional
solvents can either be separated off before further use or be used
further directly as mixture of solvent/nitrate ester.
[0086] The washing medium used according to the invention is liquid
under process conditions, in particular at temperatures above
5.degree. C., preferably at temperatures above 25.degree. C., and
atmospheric pressure. Preference is given according to the
invention to the washing medium being water-based, preferably being
water.
[0087] Depending on the mass or phase ratio within the tube reactor
(washing apparatus), the nitrate ester to be washed is dispersed in
the washing medium as oil-in-water emulsion (O/W emulsion) or else
the washing medium is dispersed in the nitrate ester to be washed
as water-in-oil emulsion (W/O emulsion).
[0088] In a preferred embodiment, the process of the invention can
be carried out continuously (although a discontinuous mode of
operation is also possible in principle). When the process is
carried out industrially, preference is in every case given to the
process being carried out continuously.
[0089] The process of the invention can in principle be used for
carrying out an acid wash and/or a basic wash and/or a neutral wash
of the crude nitric esters to be purified.
[0090] In other words, the process of the invention is in principle
suitable for carrying out the acid wash and/or the basic wash
and/or the neutral wash of the crude nitrated products or the crude
nitric esters. The process of the invention can thus be employed in
all three abovementioned washing steps. However, it is likewise
also possible for the process of the invention to be used for only
one or two washing stages, for example only for the acid wash or
only for the basic wash or only for the neutral wash. Thus, for
example, the emulsion transport of nitrate esters between the
individual process stages of a production plant and/or for further
processing after washing which is typical of nitrate esters can be
configured in accordance with the process of the invention. In this
respect, the process of the invention can be used flexibly.
[0091] In a particular embodiment of the present invention, the
process of the invention, in particular process steps (a) and (b),
can be carried out repeatedly or be performed a number of times. In
this case, the (partially) purified crude nitric esters which
result after each pass through the process are again fed to the
subsequent pass through the process.
[0092] In this particular embodiment, it can be provided for at
least one pass through the process to be carried out as a basic
wash and/or to be carried out using a basic washing medium and at
least one subsequent pass through the process to be carried out as
a neutral wash and/or carried out using a neutral washing
medium.
[0093] As an alternative, it can also be provided for two,
preferably three, sequential passes through the process to be
carried out, optionally comprising a first wash with an acidic
washing medium ("acid wash"), followed by a second wash with a
basic washing medium ("basic wash") and again after this a third
wash with a neutral washing medium ("neutral wash").
[0094] The efficiency of the washing medium can be increased
further by at least one base, as described below, being added to
the washing medium.
[0095] In other words, the invention can provide for at least one
base to be added to the washing medium, in particular for carrying
out a basic wash. This base can, in particular, be selected from
the group consisting of inorganic hydroxides, carbonates,
hydrogencarbonates and ammonia and also mixtures or combinations
thereof.
[0096] The amount of alkali used in an alkaline wash should be
sufficient for not only all acids to be able to be converted
quantitatively into their salts but there should also be an excess
of base so that the pH in the washing liquor is sufficiently high
for even weak acids to be able to be quantitatively washed out. In
this context, it is particularly advantageous for the content of
base in the washing medium to be from 0.01 to 0.4 mol/l, preferably
from 0.02 to 0.2 mol/l. In particular, the content of base in the
washing medium should be at least twice the amount of alkali
required for neutralization of all materials which are present as
impurities and form salts with bases.
[0097] As indicated above, the crude nitric esters to be purified
are liquid under process conditions. The crude nitric esters to be
purified can optionally be present as a solution in an inert
solvent, e.g. in halogen-containing hydrocarbons, in particular
methylene chloride, dichloroethane, etc., or in other solvents
which do not interfere in further processing or are used during
further processing.
[0098] Process step (b) can then be followed by separation of the
nitric esters which have been freed of impurities from the washing
medium, preferably in a phase separation apparatus (separator).
[0099] As phase separation device or phase separation apparatus, it
is possible to use all types of static separators, and also dynamic
separators such as centrifugal separators. The separation time of
the emulsion of nitrate ester/washing medium depends not only on
the density difference between the two phases, the type of emulsion
(W/O or O/W) and the mixing energy introduced but also on the
excess of base in the washing medium which is not required for
neutralization. When the same mixing energy is introduced, the
separation time decreases significantly with increasing
concentration of base in the washing medium. However,
surface-active agents or mechanical separation aids, e.g. packings,
separation plates, etc., can also be used for accelerating phase
separation. The phase separation can also be accelerated by means
of a spacing between the individual mixing elements which is
matched to the nitrate ester and the type of emulsion.
[0100] In an advantageous embodiment of the process of the
invention, the washing medium is, especially after separation of
the nitrated nitric esters which have been freed of the impurities
from the washing medium, recycled. In this way, efficient washing
is made possible and the amount of washing medium is reduced to a
minimum.
[0101] To remove impurities having high partition coefficients in
favor of the nitrate ester to be washed, high mass transfer
resistances in the organic phase and slow further reaction of the
extracted impurities in the washing medium, e.g. nitrous gases or
nitrogen dioxide, the residence time in the subsequent reactor
should be matched to these circumstances. In a particular
embodiment of the process of the invention, this can, for example,
be achieved by means of a combination of the above-described
devices for producing an optimal washing emulsion, e.g. by means of
stirred vessels, in order to ensure the necessary residence time
for phase transfer and the subsequent reaction.
[0102] The dispersion/emulsion present at the end of the mixing
section can be separated again into the individual phases in a
phase separation apparatus (separator or settler). The washing
medium together with the impurities present therein can either be
passed as wastewater to wastewater treatment or be introduced in
countercurrent into the preceding washing stage.
[0103] The washed nitrate ester can either be fed to the next
washing stage or at the end of washing be transferred directly to
further processing or to an intermediate storage facility.
[0104] After washing or after the washing medium has been separated
off (e.g. after separation of the washing emulsion in a static
separator or by means of a centrifugal separator), traces of
suspended and dissolved water may optionally be removed from the
purified nitrate ester by means of additional drying, if
desired.
[0105] As indicated above, the process of the invention is
associated with many advantages and special features, of which some
advantages and special features will be indicated below, but not
conclusively and not in a restrictive manner.
[0106] In particular, the process of the invention allows efficient
purification of crude nitrated products obtained in the nitration
of nitratable monohydric and polyhydric (cyclo)aliphatic alcohols
after removal of the residual nitrating acid with only a low degree
of complexity and good process economics such as process
efficiency.
[0107] The tube reactor employed according to the invention for
purifying the crude nitration products makes it possible to produce
large exchange areas for a two-phase mixture of washing medium and
crude nitrate ester, so that effective mass transfer and rapid
transfer of the impurities into the washing medium or, in the case
of acidic compounds, rapid neutralization is ensured in this
way.
[0108] The process of the invention allows rapid and at the same
time efficient removal of the impurities originating from the
nitration from the crude nitrated products, with the washing medium
being able to be readily recycled or circulated after treatment of
the nitrate esters.
[0109] Furthermore, the general safety when handling the highly
sensitive multiply nitrated nitrate esters such as NGL or EGDN,
etc., is improved further by the consistent use of the process of
the invention. The amount of explosive substances present in the
plant are reduced further.
[0110] The tube reactor with additional mixing elements which is
used according to the invention not only allows efficient and
intimate dispersion of washing medium and nitrated (cyclo)aliphatic
alcohol in one another, but targeted setting of a defined
dispersion of the nitrate ester to be washed in the washing medium
over the entire length of the tube reactor reliably prevents, when
the permissible tube cross sections are observed, partial
coalescence of the dispersed nitrate ester in the tube reactor and
thus prevents the formation of liquid threads of separated-out
nitrate ester which could result in detonation.
[0111] The process of the invention is suitable for carrying out
the acid wash and/or the basic wash and/or the neutral wash of the
crude nitrated products. The process on the invention can thus be
used in all three abovementioned washing steps. However, it is
likewise possible to use the process of the invention for only one
or two washing stages, for example only for the acid wash or only
for the basic wash or only for the neutral wash. In this way, the
emulsion transport of, for example, nitrate esters between the
individual process stages of a production plant and/or to further
processing after washing which is typical of nitrate esters can be
configured according to the process of the invention. In this
respect, the process of the invention can be used flexibly.
[0112] The present invention further provides, according to a
second aspect of the present invention, an apparatus (plant) for
removing impurities obtained in the preparation of aliphatic or
cycloaliphatic nitric esters (nitrate esters), in particular for
removing impurities from crude nitric esters obtained in the
nitration of nitratable monohydric or polyhydric aliphatic or
cycloaliphatic alcohols after removal of the residual nitrating
acid, by treatment with at least one washing medium, where the
apparatus of the invention is particularly suitable for carrying
out a process as indicated above,
[0113] wherein the apparatus comprises the following devices:
[0114] (a) at least one dispersing device, in particular at least
one mixing device, for contacting and emulsifying crude nitric
esters to be purified and washing medium; and, [0115] (b) arranged
downstream of the dispersing device, a tube reactor for
introduction of the emulsion of crude nitric esters to be purified
and washing medium produced in the dispersing device, where the
tube reactor is equipped with mixing elements, in particular for
introduction of additional mixing energy, so that the impurities
initially present in the crude nitric esters are at least partially
removed during passage of the emulsion through the tube reactor
and/or so that the impurities initially present in the crude nitric
esters are at least partly transferred into the washing medium
and/or neutralized thereby during passage of the emulsion through
the tube reactor.
[0116] As indicated above in connection with the process of the
invention, the dispersing device, in particular the mixing device,
can be configured as jet mixer or pump, in particular jet pump
(injector).
[0117] As has likewise been described above in the context of the
process of the invention, the dispersing device, in particular the
mixing device, can be configured in such a way that it produces a
driving jet (central jet) and an annular jet surrounding the
driving jet.
[0118] As has likewise been indicated in connection with the
process of the invention, the dispersing device, in particular the
mixing device, can be configured as jet mixer or jet pump
(injector). Here, the jet mixer or the jet pump can, in particular,
be configured so that a preferably central driving jet and a medium
surrounding the driving jet, in particular in the form of an
annular jet, can be produced.
[0119] As stated above in connection with the process of the
invention, the dispersing device, in particular the mixing device,
can be installed upstream, in particular directly upstream, of the
reactor, with, in a particular embodiment, the dispersing device,
in particular the mixing device, being able to go over into the
tube reactor.
[0120] In an alternative embodiment, the dispersing device, in
particular the mixing device, can be integrated into the tube
reactor and/or be a constituent of the tube reactor. In this
respect, reference may be made to what has been said above in
connection with the process of the invention.
[0121] As explained above in the description of the process of the
invention, the tube reactor is equipped with mixing elements, in
particular for introducing additional mixing energy. As regards
further details, reference may be made to the process of the
invention.
[0122] A one-, two- or three-stage wash of the crude nitration
product (i.e. acid wash and/or basic wash and/or neutral wash) can
be carried out in the apparatus of the invention.
[0123] Furthermore, it can be provided, according to the invention,
for a separation device, in particular a separator, for separating
the nitrated products which have been freed of the impurities from
the washing medium to be arranged downstream of the tube
reactor.
[0124] Furthermore, it is possible in the apparatus of the
invention for a stirred vessel and or a stirred reactor to be
arranged downstream of the tube reactor and upstream of the
separation device (i.e., in other words, between tube reactor and
separation device). In particular, the contact and/or residence
time between nitrated products (nitric esters) and the washing
medium is prolonged in this way.
[0125] For further details regarding the apparatus or plant of the
invention, reference may be made, in order to avoid unnecessary
repetition, to what has been said above in respect of the process
of the invention, which applies analogously to the apparatus or
plant of the invention.
[0126] Finally, the present invention further provides, according
to a third aspect of the present invention, a production plant for
the preparation of nitric esters of monohydric or polyhydric
aliphatic or cycloaliphatic alcohols and/or for the nitration of
monohydric or
[0127] polyhydric aliphatic or cycloaliphatic alcohols with
subsequent purification of the crude nitrated products formed in
the nitration, wherein the production plant comprises the following
units: [0128] (a) a nitration unit for the preparation of nitric
esters of monohydric or polyhydric aliphatic or cycloaliphatic
alcohols and/or for the nitration of monohydric or polyhydric
aliphatic or cycloaliphatic alcohols, in particular with one or
more appropriate reaction vessels for carrying out the nitration
reaction(s); [0129] (b) optionally, arranged downstream of the
nitration unit in the production line, a separation device, in
particular a separator, in particular for the removal of the
residual nitrating acid from the nitrated crude products (crude
nitric esters); [0130] (c) arranged downstream of the nitration
unit and any separation device present in the production line, a
washing facility for carrying out washing of the crude nitrated
products, where the washing facility comprises: [0131] at least one
dispersing device, in particular at least one mixing device, for
contacting and emulsifying crude nitric esters to be purified and
washing medium; and, [0132] arranged downstream of the dispersing
device, a tube reactor for introduction of the emulsion of crude
nitric esters to be purified and washing medium which has been
produced in the dispersing device, where the tube reactor is
equipped with mixing elements, in particular for introducing
additional mixing energy, so that the impurities initially present
in the crude nitric esters are at least partially removed during
passage of the emulsion through the tube reactor and/or so that the
impurities initially present in the crude nitric esters are at
least partly transferred into the washing medium and/or neutralized
thereby during passage of the emulsion through the tube reactor;
[0133] (d) optionally, arranged downstream of the washing facility
in the production line, a stirred vessel, in particular for
increasing the contact and/or residence time between nitric esters
and washing medium; [0134] (e) arranged downstream of the washing
unit and any stirred vessel present in the production line, a
separation device, in particular a separator, in particular for
separating the nitric esters which have been freed of the
impurities from the washing medium.
[0135] In other words, the above-described apparatus or plant for
purification, i.e. for the removal of impurities, is a constituent,
namely in the form of the washing unit or washing facility (c), of
the production plant of the invention.
[0136] As indicated above, the mixing elements in the tube reactor
can be static mixing elements or be configured as static mixing
elements.
[0137] In a particular embodiment, the mixing elements, in
particular the static mixing elements, can be fixed to the inside
in the tube reactor, in particular be joined permanently or
releasably to the interior walls of the tube reactor.
[0138] As an alternative, the mixing elements can also be
configured as push-in elements. Here, the push-in elements can be
inserted as required according to number and/or position into the
tube reactor or positioned in the tube reactor.
[0139] As indicated above, the mixing elements can be configured as
metal plates, in particular impingement or deflection plates, as
orifice plates, as static mixers or as flow dividers.
[0140] In particular, from 1 to 15 mixing elements, in particular
from 2 to 15 mixing elements, preferably from 2 to 10 mixing
elements, particularly preferably from 2 to 5 mixing elements, can
be arranged in the tube reactor.
[0141] As indicated above, it is advantageous for a mixing energy
(i.e. volume-based mixing energy) of from 20 to 1000 joule/liter,
preferably from 25 to 500 joule/liter, particularly preferably from
30 to 200 joule/liter, to be introduced by the mixing elements in
the tube reactor and/or for the pressure drop per mixing element to
be from 0.2 bar to 3.0 bar, preferably from 0.3 to 1.5 bar,
particularly preferably from 0.3 to 0.8 bar.
[0142] As indicated above in connection with the process of the
invention and the apparatus or plant of the invention, the
dispersing device, in particular the mixing device, can be
configured as jet mixer or pump, in particular jet pump
(injector).
[0143] Furthermore, the dispersing device, in particular the mixing
device, can be configured so that it produces a driving jet
(central jet) and an annular jet surrounding the driving jet.
[0144] In a particular embodiment, the dispersing device, in
particular the mixing device, can be configured as jet mixer or jet
pump (injector). Here, the jet mixer or the jet pump can be
configured so that a preferably central driving jet and a medium
surrounding the driving jet, in particular in the form of an
annular jet, can be produced.
[0145] As indicated above, the dispersing device, in particular the
mixing device, can be upstream, in particular directly upstream, of
the reactor. In this embodiment, the dispersing device, in
particular the mixing device, can go over into the tube
reactor.
[0146] In an alternative embodiment, the dispersing device, in
particular the mixing device, can also be integrated into the tube
reactor or be a constituent of the tube reactor.
[0147] For further details regarding the production plant of the
invention, reference may be made to what has been said above in
respect of the process of the invention and the apparatus or plant
of the invention, which applies analogously to the production plant
of the invention.
[0148] The process of the invention and the apparatus or plant of
the invention for purification and also the production plant of the
invention for nitration are illustrated by way of example and in a
nonrestrictive way in the attached figures.
[0149] Further advantages, properties, aspects and features of the
present invention may be derived from the following description of
embodiments which are preferred according to the invention and are
depicted in the drawings. The drawings show:
[0150] FIG. 1 a schematic depiction of a single-stage wash for
crude nitrate esters according to the process of the invention or
using the apparatus of the invention;
[0151] FIG. 2 a detailed depiction of individual parts of the
apparatus as per the schematic depiction of the process of the
invention in FIG. 1;
[0152] FIG. 3 a schematic depiction of a process flow of the
process of the invention or a schematic depiction of the apparatus
or plant of the invention as per a preferred working example of the
invention for the usual three washing stages for washing nitrate
esters;
[0153] FIG. 4 a schematic depiction of a production plant according
to the invention for the nitration of nitratable monohydric and
polyhydric alcohols with subsequent washing of the resulting
nitrate esters as per a preferred working example of the
invention.
[0154] FIG. 1 shows, in a schematic depiction, an embodiment of a
washing stage according to the process of the invention or using
the apparatus or plant of the invention for washing crude nitrate
esters with the washing medium as driving jet.
[0155] The crude nitrate ester NE1(n-1) where n=1-3 to be washed
is, after removal of the residual nitrating acid, introduced into a
wash WW1(n-1) where n=1-3, i.e. into an acid wash WS where n=1 or,
after removal of all other weakly acidic materials from the
oxidative degradation of impurities in the presence of bases which
are still dissolved in the nitrate ester, into an alkaline wash WA
where n=2 or into a neutral wash WN where n=3, combined with the
washing medium WW10 (fresh water) or WW1n where n=1-3, which in the
case depicted serves as driving jet, in a mixing device SMn,1 where
n=1-3, preferably in a jet pump (injector) or a jet mixer, and
introduced directly into a tube reactor C which contains the
additional mixing elements Mn,m+1 where n=1-3 and where m=1-15.
[0156] The washing emulsion from the tube reactor is, either
directly or, if necessary, after a prolonged residence time in a
residence vessel (e.g. in a stirred vessel R, etc.), separated into
the phases in a separation apparatus Sn where n=1-3.
[0157] The washed nitrate ester NE1n where n=1-3 is either fed to
the subsequent washing stage or passed as fully washed product NE13
to further processing. The loaded washing medium WW1n where n=1-3
is either directly discharged as wastewater or else recirculated as
substream for setting a defined phase ratio between nitrate ester
and washing medium. This recirculated substream can be directly
fed, either together with the freshly added washing water as
driving jet or as circulating stream, into the tube reactor.
[0158] The depictions of FIGS. 2a-2c show the mixing devices SMn,1
where n=1-3 schematically depicted in FIG. 1, as jet pump (FIG. 2a)
and as jet mixer (FIG. 2b), where V1 denotes the driving jet
(preferably washing medium) and V2 denotes the nitrate ester. A
possible arrangement of the static mixing elements Mn,2, Mn,3,
Mn,4, Mn,m-1, Mn,m and Mn,m+1 in the tube reactor, distributed over
the total length of the tube reactor, is additionally depicted in
FIG. 2c.
[0159] FIG. 3 shows an example of the process of the invention in
three steps for the separate removal of the mineral acids by means
of an acid wash (WS), for the removal of all weakly acidic
materials from the oxidative degradation of impurities which are
still present in the presence of bases in the alkaline range by
means of an alkaline wash (WA) and for the removal of traces of
entrained alkaline washing liquor by means of a neutral wash (WN):
[0160] a) In step 1, the sulfuric and nitric acid suspended and
dissolved in the crude nitrate ester NE 10 is removed by washing
with fresh water WW 10 in a single-stage acid wash WS. The washing
water WW 10 and recirculated washing water WW 11 as driving jet are
fed directly by means of pump P together with the nitrate ester NE
10 to be washed using a jet pump (injector) or via a jet mixer into
a tube reactor which contains additional mixing elements M1,m+1.
After passage through the tube reactor, the emulsion formed is
separated in a separator S1. After phase separation, the washing
medium is either discharged directly as wastewater WW 11 or, as an
alternative, a substream is additionally circulated in order to set
a prescribed phase ratio and thus a defined type of emulsion. The
nitrate ester NA 11 which has been freed of mineral acids is fed
into washing stage 2, viz. the alkaline wash WA. [0161] b) In step
2, all remaining dissolved mineral acids and other acidic materials
from the oxidative degradation of impurities are removed in a
single-stage alkaline wash WA. The washing water WW 13 from the
neutral wash and recirculated washing water WW12 as driving jet are
fed directly with addition of a base by means of pump P together
with the nitrate ester NE 11 to be washed from the acidic wash WS
using a jet pump (injector) or via a jet mixer into a tube reactor
which contains additional mixing elements M2,m+1. After passage
through the tube reactor, the emulsion formed is separated in a
separator S2. The wastewater WW 12 having a pH of greater than 7.5
is either discharged directly or, as an alternative, a part thereof
can be circulated in order to set a prescribed phase ratio and thus
a defined type of emulsion. The nitrate ester NA 12 which has been
freed of all mineral acids and other acidic materials from the
oxidative degradation of impurities is fed into the washing stage
3, viz. the neutral wash WN. [0162] c) In step 3, the entrained
traces of washing medium from the alkaline wash are removed in a
single-stage neutral wash WN. The washing water WW 10 and
recirculated washing water WW 13 as driving jet are fed directly by
means of pump P together with the nitrate ester NE 12 to be washed
using a jet pump (injector) or via a jet mixer into a tube reactor
which contains additional mixing elements M3,n+1. After passage
through the tube reactor, the emulsion formed is separated in a
separator S3. The washing medium which contains the residual traces
of alkali and impurities is either introduced directly as
wastewater WW 13 into the second washing stage WA or, as an
alternative, a part thereof can be additionally circulated in order
to set a prescribed phase ratio and thus a defined type of
emulsion. The nitrate ester NE 13 which has been freed of mineral
acids and other acidic materials from the oxidative degradation of
impurities and residual traces of alkali is passed directly to
further processing or, after removal of any inert solvents present,
to an intermediate storage facility.
[0163] FIG. 4 shows an example of a production plant according to
the invention for the preparation of nitrate esters with integrated
washing according to the invention of the crude nitrate esters from
an isothermal or adiabatic nitration. The crude nitrate ester NE 10
formed in the nitration unit N by reaction of the alcohol to be
nitrated with nitric acid in the presence of sulfuric acid is,
after removal of the nitrating acid in the separator S, washed in
the acid wash WS using water WW 10 in the manner according to the
invention. After phase separation, the resulting wastewater WW 11
which contains all washed-out sulfuric and nitric acid is fed
together with the nitric acid WNA obtained from the offgas
treatment of the nitration plant in an absorber plant A either
directly or after concentration in an SAC plant SAC together with
the residual acid AS from the nitration back into the nitration or
is discharged as wastewater to be treated.
[0164] The nitrate ester NE 11 which has been freed of the mineral
acids is washed in one stage in the washing stage (i.e. alkaline
wash WA) in the presence of bases according to the process of the
invention. After phase
[0165] separation, the wastewater WW12 which originates from the
alkaline wash and has a pH in the range from 7.5 to 13 and still
contains all other acidic materials from the oxidative degradation
of impurities is fed to additional treatment before discharge into
a main outfall drain. The nitrate ester NA 12 from the alkaline
wash WA is fed into the neutral wash WN and washed in one stage
with water WW 10 according to the process of the invention. After
phase separation, the wastewater WW 13 coming from the neutral wash
WN is fed together with base into the alkaline washing stage 2
(WA). The washed nitrate ester NA 13 is passed directly to further
processing or introduced into an intermediate storage facility.
[0166] Further embodiments, modifications, variations of the
present invention will be able to be readily recognized and
realized by a person skilled in the art on reading the description,
without going outside the scope of the present invention.
[0167] The present invention is illustrated by the following
working examples, but without the present invention being
restricted thereto.
Working Examples
Washing of Ethylhexyl Nitrate (EHN)
[0168] In the following working examples, the washing of a crude,
i.e. still unwashed and contaminated with by-products originating
from the nitration and unreacted starting chemicals, ethylhexyl
nitrate coming from the nitration is described. The objective is,
inter alia, to obtain a total acid content of less than 30 ppm,
calculated as nitric acid (normal commercial product
specification).
[0169] Even though the process of the invention or the apparatus of
the invention is illustrated using ethylhexyl nitrate (EHN) as
nitrate ester to be purified in the following working examples, the
process and the apparatus of the present invention are not
restricted thereto but are applicable to any other nitrate esters,
e.g. nitrate esters from the nitration of glycerol,
trimethylolpropane, propanediol, ethylene glycol, diethylene glycol
and triethylene glycol, etc., and can be carried out using any
other bases instead of sodium hydroxide for the alkaline wash.
Example 1: Three-Stage Washing of EHN (According to the
Invention)
Example 1.1: Single-Stage Acid Wash
[0170] Unwashed ethylhexyl nitrate (EHN) (134.7 g/min) from a
continuous nitration of ethylhexanol as per EP 1 792 891 A1 having
a residual content of sulfuric acid (0.13%), nitric acid (0.84%)
and ethylhexanol (about 0.4%) was fed together with 67 g/min of
demineralized water and circulated washing acid in a ratio of 1:1
by means of a jet mixer (injector) using the washing medium as
central jet at room temperature (about 21.degree. C.) into a tube
reactor which additionally contained three static mixing elements.
The relative velocity between central jets and EHN to be washed was
about 8:1. The residence time in the tube reactor was not more than
5 seconds. The pressure drop over the total length of the tube
reactor was about 0.9 bar (corresponding to a mixing energy of
about 90 joule/l). After phase separation, the EHN still contained
about 2700 ppm of acid (reported as nitric acid); the washing water
contained about 0.25% of sulfuric acid and about 1.65% of nitric
acid.
Example 1.2: Single-Stage Alkaline Wash
[0171] The ethylhexyl nitrate (EHN) originating from the acid wash
as per example 1.1 (133.3 g/min) having a residual content of acid
of about 2700 ppm (reported as nitric acid) was fed together with
67 g/min of an aqueous solution containing ammonia (0.16%, i.e. 10%
excess) and circulated washing liquor in a ratio of 1:1 by means of
a jet mixer (injector) using the washing medium as central jet at
room temperature (about 21.degree. C.) into a tube reactor which
additionally contained three static mixing elements. The relative
velocity between central jet and EHN to be washed was about 8:1.
The residence time in the tube reactor was not more than 5 seconds.
The pressure drop over the total length of the tube reactor was
about 0.9 bar (corresponding to a mixing energy of about 90
joule/l). After phase separation, the EHN still contained about 29
ppm of acid (reported as nitric acid).
Example 1.3: Single-Stage Neutral Wash
[0172] The ethylhexyl nitrate (EHN) (133 g/min) originating from
the alkaline wash as per example 1.2 having a residual content of
acid of about 29 ppm (reported as nitric acid) was fed together
with 67 g/ of demineralized water and circulated washing water in a
ratio of 1:1 by means of a jet mixer (injector) using the washing
medium as central jet at room temperature (about 21.degree. C.)
into a tube reactor which additionally contained three static
mixing elements. The relative velocity between central jet and EHN
to be washed was about 8:1. The residence time in the tube reactor
was not more than 5 seconds. The pressure drop over the total
length of the tube reactor was about 0.9 bar (corresponding to a
mixing energy of about 90 joule/l). After phase separation, the EHN
still contained about 0.1 ppm of acid (reported as nitric
acid).
Example 2: Washing of EHN (Comparison)
Example 2.1: Single-Stage Alkaline Wash
[0173] Ethylhexyl nitrate (EHN) (133.3 g/min) from an acid wash, as
described in example 1.1, having a residual content of acid of
about 2700 ppm (reported as nitric acid) was fed together with 67
g/min of an aqueous solution containing ammonia (0.16%, i.e. 10%
excess) and circulated washing liquor in a ratio of 1:1 by means of
a jet mixer (injector) using the washing medium as central jet at
room temperature (about 21.degree. C.) into a tube reactor which,
however, did not contain any static mixing elements. The relative
velocity between central jet and EHN to be washed was about 8:1.
The residence time in the tube reactor was not more than 5 seconds.
The pressure drop over the total length of the tube reactor was
about 0.10 bar (corresponding to a mixing energy of about 10
joule/l). After phase separation, the EHN still contained about
1200 ppm of acid (reported as nitric acid).
Example 2.2: Single-Stage Neutral Wash
[0174] The ethylhexyl nitrate (EHN) (133.3 g/min) originating from
the alkaline wash as per example 2.1 having a residual content of
acid of about 1200 ppm (reported as nitric acid) was fed together
with 67 g/min of demineralized water and circulated washing water
in a ratio of 1:1 by means of a jet mixer (injector) using the
washing medium as central jet at room temperature (about 21.degree.
C.) into a tube reactor which did not contain any static mixing
elements. The relative velocity between central jet and EHN to be
washed was about 8:1. The residence time in the tube reactor was
not more than 5 seconds. The pressure drop over the total length of
the tube reactor was about 0.10 bar (corresponding to a mixing
energy of about 10 joule/l). After phase separation, the EHN still
contained about 456 ppm of acid (reported as nitric acid).
Example 3: Single-Stage Wash of EHN (According to the
Invention)
[0175] Unwashed ethylhexyl nitrate (EHN) (134.7 g/min) from a
continuous nitration of ethylhexanol as per EP 1 792 891 A1 having
a residual content of sulfuric acid (0.13%), nitric acid (0.84%)
and ethylhexanol (about 0.4%) was fed together with 67 g/min of an
aqueous solution containing ammonia (0.6%) and circulated washing
liquor in a ratio of 1:1 by means of a jet mixer (injector) using
the washing medium as central jet at room temperature (about
21.degree. C.) into a tube reactor which additionally contained six
static mixing elements. The relative velocity between central jet
and EHN to be washed was about 8:1. The residence time in the tube
reactor was not more than 5 seconds. The pressure drop over the
total length of the tube reactor was about 1.8 bar (corresponding
to a mixing energy of about 180 joule/l). After phase separation,
the EHN still contained about 26 ppm of acid (reported as nitric
acid)..
* * * * *