Note: Descriptions are shown in the official language in which they were submitted.
1 33653 1
T 5763
APPARATUS AND PROCESS SUITABLE FOR
PRODUCING HYDROGEN
The invention relates to an apparatus suitable for producing
hydrogen and to a process for producing a hydrogen-containing gas.
It is well known to prepare a hydrogen-containing gas such as
synthesis gas (which mainly consists of hydrogen and carbon monoxide,
and in addition carbon dioxide, nitrogen and (unconverted) hydro-
carbons and steam) by means of endothermic steam reforming of a
hydrocarbonaceous feed in an apparatus in which heat is exchanged
between flue gas and product gas in order to recover heat which is
required to maintain an adequate reaction temperature. However, the
heat is not recovered in such an apparatus where it is needed most
i.e. in the reaction section wherein a usually highly endothermic
reaction is to be carried out.
It is furthermore known to make use of the heat-content of
product gas emanating from a reaction zone by employing a reaction
section comprising two concentrical tubes forming an annular space
which contains catalyst particles and removing product gas through
the central tube, thus exchanging heat directly between the hot
product gas and the catalyst.
A major problem associated with the use of a reaction section
comprising concentrical tubes is the degree of heat exchange which
can be attained therewith, in particular when product gas with a
temperature of 800 C or even 1000 C is to be cooled.
Surprisingly, it has now been found that helically wound tubes
arranged inside catalyst containers provide excellent heat transfer
between hot product gas removed via said tubes and surrounding
catalyst particles which are further heated by convective heat
exchange.
The invention therefore relates to an apparatus suitable for
producing hydrogen which comprises
,~., ~
1 33653 1
2 63293-2911
(i) a housing containing a convection section having inlet- and
outlet means for a heating medium, and
(ii) a reaction section having inlet- and outlet means for process
fluid, which reaction section comprises (a) catalyst container(s)
extending into the convection section and each catalyst container
comprising a plurality of helically wound open-ended tubes
wherein the process fluid inlet means are in communication with
the catalyst container(s) and wherein the process fluid outlet
means are in communication with the upper end parts of the tubes.
The invention further relates to a process for producing
a hydrogen-containing gas which comprises contacting a
hydrocarbonaceous feed in the presence of steam at elevated
temperature and pressure with a reforming catalyst which is heated
by means of convective heat transfer and removing hydrogen-
containing product gas through helically wound tubes extending in
the reforming catalyst.
The apparatus and process according to the invention
will be elucidated hereinafter with the use of the Figures in
which various preferred embodiments have been incorporated without
having the intent of limiting the invention to those particular
embodiments as depicted in the Figures. Reference numerals
relating to corresponding parts are the same for Figures 1-3.
Figure 1 relates to a longitudinal section of an
apparatus according to the invention.
In Figure 2 a cross section is shown at AA' of the
apparatus depicted in Figure 1.
Figure 3 represents a longitudinal section of an
apparatus which contains additional heat exchange means, compared
_ 2a 1 3 3 6 5 31 63293-2911
with the apparatus depicted in Figure 1.
The apparatus depicted in Figure 1 comprises a housing
(1) containing a convection section (2) having inlet means (3) for
a heating medium e.g. a hot liquid or gas or even particulate
solids, preferably combustion gas, and outlet means (4) therefor.
The housing furthermore contains a reaction section
comprising one or more catalyst containers (8) and a distribution
section (5)
1 33653 t
-- 3 --
having inlet means (6) for process fluid such as a feed mixture of
steam and a hydrocarbons-containing gas (preferably natural gas or
methane) and outlet means (7) for process fluid such as a mixture
of hydrogen-containing product gas and unconverted feed gas.
The catalyst containers (8) are preferably tubular shaped and
enclose at least the major part of a plurality of at least partly
helically wound open-ended tubes (9).
Preferably, a plurality of tubular catalyst containers (8),
which are suitably arranged in one (as depicted in Figure 2) or
more (concentrical) circular patterns in the housing (1), extend
downwardly into the convection section (2).
The distribution section (5) is preferably separated from the
convection section (2) by means of a tube sheet (10) in order to
avoid contamination of product gas emanating through outlet means
(11) with heating gas. Moreover, by suspending the tubular catalyst
containers by means of tube sheet (10) the containers can expand
freely during start up of the apparatus according to the invention,
without causing problems such as cracking of the tubes or tube
connections which can easily occur when the tubes are connected at
both ends to in- or outlets means.
In order to ensure as uniform heating of the catalyst containers
as possible, the convection section preferably contains means (12)
for preventing radiant heat transfer, such as the disc-shaped
insulation means e.g. containing refractory material depicted in
Figures 1 and 3.
Process feed gas can enter a catalyst container only through
inlet opening (13) in the upper end part thereof and proceeds
downwardly through the particulate catalyst which is preferably
used in order to be able to operate at a relatively low temperature
from 400 to 1200 C at a pressure from 2 to 200 bar in the reaction
section (5).
Preferably, the catalyst containers (8) are provided with
catalyst support means (14) in their closed lower end parts in
order to avoid entrainment of catalyst particles into the open
lower end parts (15) of the two helical coil tubes which are
- 1 336531
-- 4 --
preferably present in each catalyst container. The catalyst support
means (14) may additionally serve as positioning means for said
lower end parts (15) of the helical coil tubes.
During operation hot process gas centers tubes (9) through end
parts (15) as depicted in Figures 1 and 3 and flows upwardly, thus
ensuring optimal heat exchange with the surrounding catalyst.
Heat exchanged process gas (which still may have a temperature
of e.g. 500-1000 C) enters the annular-shaped channel (16) present
in the upper end part (29) of catalyst container (8) and communi-
cating with a pair of helically wound tubes. The annular channels(16) are in open communication with product outlet means (7) via
manifold tubes (17).
In the above-described manner the upper parts of each pair of
helically wound tubes (9) are connected to a single outlet manifold
(7) for process fluid arranged substantially centrally in the upper
part of the housing (1). Such an arrangement is very advantageous
from a constructional point of view because the use of a plurality
of individual outlet means for each catalyst tube, with the associated
sealing and expansion problems, can thus be avoided; moreover, the
pressure in all manifold tubes (17) will be substantially equal,
thus ensuring optimal distribution of process gas over all catalyst
containers.
In the bottom section (18) of housing (1) one or more combustor
outlet means may be present as depicted in Figures 1 and 3 which
function as inlet means (3) for heating medium. In a preferred
embodiment of the apparatus according to the invention a plurality
(e.g. three) of combustor outlet means are (e.g. tangentially)
arranged in the housing in a rotation-symmetrical manner (not
depicted in the Figures) in order to ensure optimal distribution of
combustion gas throughout the combustion section (2).
The combustion means depicted in Figures 1 and 3 comprise
inlet means (19) for (e.g. oxygen-enriched) air, inlet means (20)
for a combustible fluid (e.g. hydrocarbonaceous gas, llquid and/or
coal) and, optionally, inlet means (21) for recycled gas such as
_ 5 _ 1 33653 1
carbon monoxide-containing gas separated off from hydrogen- and
carbon monoxide containing product gas e.g. by means of pressure
swing adsorption (not shown in the Figures), or recycled flue gas.
In Figure 3 a more complex, even more heat-efficient embodiment
of the apparatus according to the invention is depicted wherein the
outlet manifold (7) comprises a plurality of concentrically arranged
tubes forming at least one annular space (22) which is in open
communication with inlet means (23) and outlet means (24) for heat
exchange fluid (e.g. relatively cold expanded and/or heat-exchanged
flue gas) extending outside the housing (1).
Product outlet means (7) now comprise a tubular housing (24)
extending through tube sheet (10) into convection zone (2). The
closed bottom end part (25) of housing (24) is connected to heat
exchange fluid inlet means (23), preferably by means of expansion
bellows (not shown in Figure 3). Product manifold tubes (17) are in
open communication with tubular heat exchange means (26) having a
closed lower end part (27) in order to reverse the downward flow of
product gas during operation through the annular space (28) into
the open-ended tubular product outlet means (11) which extend
through manifold (17) into said tubular means (26).
With the above-described product outlet means a substantial
part of the thermal energy still present in the product gas emanating
from manifold tubes (17) can be recovered.
