DOUBLE-STAGE AMMONIA CONVERTER WITH AT LEAST ONE CATALYST BED AND A CENTRAL HEAT EXCHANGER

CONVERTISSEUR D'AMMONIAQUE A DEUX ETAPES COMPOSE D'AU MOINS UN LIT DE CATALYSEUR ET D'UN ECHANGEUR DE CHALEUR CENTRAL

English Abstract

A b s t r a c t :
"Double-stage ammonia converter with at least one catalyst bed
and a central heat exchanger
The invention relates to a double-stage ammonia converter with at
least one catalyst bed of annular-type arrangement and a central
heat exchanger being passed by a reaction gas. The object of the
present invention is to provide for a solution which allows an ex-
pedient routing of the heat exchanger tubes, an independence of the
heat exchanger length from the catalyst bed height, and a favour-
able heat transfer to be obtained with a relatively simple struc-
tural design The problem is solved, as per this invention, by the
fact that the heat exchanger (5) is designed to have a single tube-
sheet (7) with U-shaped tubes (6), the U-tube inlets being located
in the tubesheet centre and the U-tube outlets at the periphery.
RVPP11001Q71287

Claims

27046-12
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Double-stage ammonia converter with at least one
catalyst bed of annular-type arrangement and a central heat
exchanger being passed by a reaction gas, wherein the heat
exchanger is designed to have a single tubesheet with U-shaped
tubes, the U-tube inlets being located in the tubesheet centre and
the U-tube outlets at the periphery.
2. Double-stage ammonia converter according to claim 1,
wherein the tubesheet is located on the upper side of the heat
exchanger and equipped with a central fresh gas supply line and a
distribution dome.
3. Double-stage ammonia converter according to claim 1
wherein the U-shaped tubes are provided with baffles for guiding
the heat exchanging gas leaving the first catalyst bed.
4. Double-stage ammonia converter according to any one of
claims 1 to 3 wherein at least one quench gas admission line with
variable inlet opening is installed within the U-shaped tubes of
the heat exchanger.

Description

` 129896
"Double-stage ammonia converter wi-th at least one catalyst bed
ar.d a central heat eY~changer"
_ _ . _ _ _ _ _ _ _ _ _ _ _ _ _
The nvention relates to a ~ouble-stage ammonia converter Wl _h at
least one catalyst bed of annular-type arrangement and a central
heat exshanger being passed by a reactlon gas.
Such oouble-stage ammonia converters available in diffArent ae-
signs, as, for example, referred to in DE-GS 27 10 247 or DE-OS 31
46 778, are well knowr.. The solutions oftered have in common th~t
the gas is introduced via a _oncentric pipe in the heat -xchanger
and is fed, via the respective backflow rubes, to the iniet of the
f:rst catalyst bed or preheating prior to passing through the cat-
alyst bed and dissipating the hea~ at least partially ln the --ol-
lowing heat exchanger.
It has become evident that, depending upon the structural design
and the gas flow path, the central pipe which has a large cross
section does not permit optimum results.
The object of the invention is to provide for a solution which al-
lows an expedient routing of the heat exchanger tubes and a favour-
able heat transfer to be obtained with a relatively simple struc-
tural design.
Referring to a double-stage ammonia converter as described above,
the problem is solved, as per the present invention, by the fac.
that the heat exchanger is designed to have a simple tubesheet with
U-shaped tubes and that, contrary to the us~lal design, the U-tube
inlets are located in the tubesheet centre tand the U-tube outlets
at the periphery.
U-shaped heat exchanyer tubes are, of course, known. In the dou-
ble-stage ammonia converters referred to above they offer the ad-
vantage that already the inner downward tube sections can be used
for heat exchange. Moreover, the single tubesheet generally allows
to realize a simple type of construction because the entire heat
RVPPllOOlQ71287

~ 3 - 1298~
exchanger can, for lnstance, be inserted and mounte(1 in the _on-
verter from above. On ~he other hand, lt can easily be cilsmc,unted
or replaced w-thout particular di'ficul~ies. Furthermore, the
length of the heat exchanger need not recessarily coincide with the
length of ~he catalyst bed, i.e. it may also be shorler.
An embodiment of the invention provides for the tubesneet being lo-
cated on the upper side of the heat exchanger and equipDed wl-.h a
central fresh gas supply line and distribution dome.
It may be expedient ;f the U-shaped tubes are provided with baffles
for guiding the heat-e~changing gas leavi~g the first catalyst bed.
It may also be advanta~eous if at least one quench gas admisc.ion
line with variable inlet opening ls installed within the heat ex--
chancer tube bundle. This device would si:nplify the start of the
reaction as well as exercise a certain control function.
The invention may be described more detailed as follows, w-th due
reference to the attached drawing which, in simplified form, shows
a cross-sectional view c,f a double-stage ammonia conver~er as per
the present invention.
The converter 1 consists of a pressure housing 2 and a cover 3. The
pressure vessel is e~uipped with two catalyst beds 4 the special
structural design of which is, however, of no concern to this in-
vention.
The cylindrical firs' catalyst bed a being of special -nterest in
this case is ec~uipped, in its interior, with a single-tu~esheet
heat exchanger 5, the U-shaped tubes 6 being arranged in a common
tubesheet 7.
The inlets of the U-shaped heat exchanger tubes 6 are connected to
the synthesis gas supply line 9 via a distribution dome 8. The tube
outlets face a gas dome 10 from which the gas flows radially
through the first catalyst bed 4.
RVPPllOOlQ71287

~ 4 ~ ~298962
The heat exchanger 5 is equipped internally wlth baffles 11 for ob-
taining optimum flow conditions. Provision has also been made for a
quench gas admission line 12 wlth varlable immersior de?th as
marked by double arrow 13. After flowing radially through the sec-
ond catalyst bed 4 the process gas lea~es the conver er via outlet
nozzle 14.
RVPPllOOlQ71287

Representative Drawing