BE683319A - - Google Patents

Description

  

   <Desc / Clms Page number 1>
 



  '' 'Hydrogen production process'.



   The present invention relates to the production of hydrogen. In one of its aspects, the invention relates to the production of hydrogen by the well-known steam gas reforming process. On the other hand, in a second aspect, the invention provides an improvement to the gas-to-water reaction conversion stages of the steam gas reforming process making it possible to manufacture hydrogen. .



   The main process implemented nowadays for the production of gas containing hydrogen, such as, for example, synthesis gases which can be used for the production of ammonia, methanol, oxo alcohols, or as a stream of substantial hydrogen for hydrogenation processes, is that applying the reaction of water vapor with hydrocarbons in the form of

 <Desc / Clms Page number 2>

 steam, especially methane. The entire hydrogen synthesis process includes components for removing, as far as possible, impurities or by-products from the hydrogen-containing gas after reforming.



   The following main reactions occur simultaneously during the reformaget.
 EMI2.1
   The first reaction is strongly endothermic, while the second reaction, i.e. the carbon monoxide reaction conversion reaction, is moderately exothermic.



  As can be seen, the products of the reforming reaction are hydrogen, carbon monoxide and carbon dioxide, as well as a quantity of water vapor and untransformed methane. The purity of a hydrogen gas stream generally depends on the amount of methane it contains, both as unreacted methane passing through the reformer and as the methane produced by the reaction. residual carbon monoxide with hydrogen in a methanizer. The hydrogen gas stream also contains larger or smaller amounts of inert gases, such as nitrogen, depending on the nitrogen content of the hydrocarbon source and the use of the end product. ,

     that is, whether hydrogen or ammonia synthesis gas has been produced. During the production of ammonia synthesis gas, air is burnt in a secondary reforming zone to obtain nitrogen for the synthesis of ammonia. The amount of air thus burnt is such that the nitrogen-to-hydrogen volume ratio is one to three in the ammonia synthesis gas produced. Small amounts of other inert gases are also generally present.



   Since the methane leak, i.e. unreacted methane from a reformer, is controllable

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 in a hydrogen production unit depending on the conditions applied in the reformer, the purity of the hydrogen gas stream depends largely on the treatment of the gas leaving the reformer. Water vapor and carbon dioxide can be easily removed. However, carbon monoxide, ethane and inert materials cannot be removed economically; Methane and inerts are not critical, but carbon monoxide is ordinarily harmful, due to its toxic nature, in processes where hydrogen is to be used.

   Therefore, the treatment of by-products is mainly concerned with carbon monoxide. The hydrogen gas stream from a reformer goes through a reaction conversion stage of carbon monoxide to convert the latter, to the greatest extent possible, into carbon dioxide which can be washed out. .



  The residual carbon monoxide is transformed into methane by a catalytic reaction with hydrogen.



   The present invention relates to the treatment of by-products, that is to say more especially the transformation of carbon monoxide into carbon dioxide and is described in detail below with the aid of the accompanying drawings, in which :
FIG. 1 represents a process for the production of hydrogen using a single stage of conversion of carbon monoxide and then using a methanizer and a scrubber removing carbon dioxide;
FIG. 2 is a similar process, but implements two stages of transformation of carbon monoxide, each followed by washing removing carbon dioxide;
FIG. 3 shows a process in accordance with the present invention comprising two reaction converters in series, separated only by a heat exchanger;

   
FIG. 4 is a different form of the method according to the invention;

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Figure 5 depicts another embodiment of the present invention.



   . Referring to the processes shown in Figures 1 and 2, a catalyst, for example a nickel oxide or chromium oxide catalyst supported on a refractory silicate or aluminate base, is used as a catalyst. reforming in furnace 4, and a reaction catalyst, such as for example an iron-ohromic reaction catalyst, is employed in converter 10. Referring to the drawings, it can be seen that in each case a hydroarbon gaseous or natural gas is desulfurized by activated carbon or by a metal oxide, either permanganate or potassium carbonate placed in an absorber or in an adsorber 2, depending on the circumstances.

     The deaulfurized hydrocarbon then reacts with steam in the reforming furnace 4. containing tubas ¯6 filled with catalyst.



  The reforming tower is set in motion so that the reforming temperature, i.e. the temperature inside the tubes, is 1200 to 1700 F (649 to 927 C).



   In the process of Figure 1, the reformed gas from furnace 4 is cooled by heat exchangers 8 to a temperature of 650 to 800 P (343 to 427 C). The reformed gas is then treated to convert the carbon monoxide in the gas to carbon dioxide and hydrogen.



   In Fig. 1, only a reaction conversion step 10 is used, which is followed by the scrubber 4 removing carbon dioxide. By this method, it is not possible to effect a conversion of the carbon monoxide of the gas leaving the reformer to less than about 1.3%. Reducing the carbon monoxide of the outgoing gas to 0.3% requires approximately five to six times as much catalyst and water vapor time.

   Therefore, the reason why a large amount of catalyst or a high gas-to-water vapor ratio is required in the process of Fig. 1

 <Desc / Clms Page number 5>

 to reduce the carbon monoxide of the outgoing gas to 0.3%, it is necessary that in the reaction conversion the equilibrium is unfavorable for
 EMI5.1
 oleeaic reaction catalysts, such as, for example, the chromium-iron reaction cazilizer, at their operating temperatures, when the reaction rates are in the order of convenience. The greater amount of steam or catalyst required for this conversion renders the process impractical.



     Economically, there must be a balance in the reaction conversion system between the gas-to-water vapor ratio and the energy this vapor provides to regenerate the carbon dioxide removal solution. When converting resulting in 0.3% carbon monoxide content, it is necessary in the reaction conversion process at a stage, such as that of Fig. 1, an amount of vapor d water two and a half times higher than that required to supply the regenerative heat to the carbon dioxide absorber. This is another reason why a smaller amount of water vapor is used in the one stage process of Figure 1. Therefore, the carbon monoxide of the gas leaving the reaction converter is not. less than about 1.3%.

   A disadvantage of the process of FIG. 1 lies in the quantity of hydrogen used when a high level of carbon monoxide to be converted into methane is present, since for each mole of methanised carbon monoxide, three soles of hydrogen are consumed. Additionally, the greater amount of carbon monoxide present increases the amount of inert gas dancing.



   Since an excessive amount of water vapor is required to bring the gases leaving the reformer to a low content of residual carbon monoxide, two reaction conversion stages 15 and 17 are used, as shown in Figure 2, if a lower carbon monoxide content is desired. In the process of figure 2, a stage of elimination

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   he or. 18 carbon dioxide follows each reaction conversion stage. Removal of most of the carbon dioxide before the second reaction conversion results in a more favorable equilibrium state in the second reaction conversion stage at temperatures where the reaction rates are favorable for the chromium-iron catalyst. used.

   The gas, which passes through the second reaction converter 17 and a second carbon dioxide converter 18, flows to the methanizer 20
In this methanizer, the remaining toxic carbon oxides and traces of carbon dioxide react with hydrogen on a catalyst, such as cobalt or nickel on alumina and the like, to form methane. In the process of Figure 2, where two reaction conversion stages are used, each followed by a carbon dioxide-removing scrubber, the carbon monoxide of the gas, from the second carbon dioxide-removing scrubber, ordinarily present a content of the order of 0.6 to 0.3%. However, considerably more equipment is required, which increases the size of the initial production unit and the manufacturing costs.



   Therefore, the present invention provides a process for the production of hydrogen, in which the member for removing carbon dioxide is removed between the two stages of the reaction conversion, but where a gas stream of hydrogen is still. obtained, which contains less than 0.6% (mole) of residual carbon monoxide to be methanized. The process can be carried out to form less than 0.3% of residual carbon monoxide. One of the unique features of the present invention is its carbon monoxide reaction converter. Accordingly, the present invention contemplates the use of high and low temperature carbon oxide reaction conversion zones.

   In accordance with

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 In the invention, a gaseous stream of hydrogen produced by the reformation of hydrocarbons with water vapor passes through two catalytic reaction conversion zones, the first of which is activated at an elevated temperature and the first second at a low temperature, the two zones being arranged in series and separated only by a member to lower the temperature of the gas as it passes between the zones. The high temperature zone operates at 650 F (343 C) or higher, while the low temperature zone is performed at less than 600 F (316 C).



   The process according to the invention, comprising a low temperature conversion, linked to a prior conversion at higher conventional temperatures, eliminates the drawbacks of the processes of Figures 1 and 2. When the high and low reaction catalysts low temperature are used in accordance with the invention, the weight ratio of the high temperature reaction catalyst to the low temperature reaction catalyst is in the range of 1: 1 to 1: 2. The process according to the invention is shown in FIG. 3. The hydrocarbons are desulphurized in the drum and then react with water vapor in the tubes 1 of the remoulding furnace 4.

   The reformed gas, cooled in the heat exchanger 8, then passes through two stages of catalytic conversion, that is to say a first stage 22 at high temperature and a second stage 24 at low temperature, arranged in series and separated only by a member 23 eliminating heat.



  In the high temperature stage 22, a catalyst active at a temperature of 650 F (343 C) or higher is used. This catalyst is a conventional iron-chromium catalyst of the type described above.



  This catalyst is preferably used in stage 22 at a temperature of 650 to 8500P (343 45400), the system pressure being 30 to 3000 peig (2.10 to 210.9 kg / cm2), which is usually atmospheric pressure. of 700 psig (49.21 kg / cm2).



   The gas from stage 22 ae cools in

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 the heat exchanger 23 for the second stage of the reaction conversion, which is a low temperature conversion zone 24.



  A catalyst active at a temperature of 600 F (316 C) or less, preferably 350 to 500 F (177 to 260 C), is used in second stage converter 24. A catalyst of this nature is a reduced zinc oxide-copper oxide catalyst disclosed in Patent Application No. 330,542, filed December 16, 1963. This catalyst, whose ratio of. zinc copper is 2 to 1, contains less than 0.2% sodium. Another low temperature reaction catalyst, which can also be used, is described in US Pat. No. 1,797,426.



   One of the advantages offered by the process according to the invention consists in that a balance can be obtained between the gas-water vapor ratio used during the conversion of carbon monoxide and the vapor requirements for the regeneration. of the carbon dioxide removal solution. Many known methods are available for the removal of carbon dioxide after the stages of carbon monoxide transformation. Almost all procedures use a liquid absorbent.



  The oldest absorbents which have been used are water, caustic soda and ethanolamines, such as, for example, monoethanolamine and diethanolamine. Newer absorbents for this use are hot potassium carbonate, Giammaroo Vetrocoke (hot potassium carbonate containing arsenates) and Shell Sulfinol, in which Sulfolane (1-thiooyclopentane dioxide) is used.



   In a practical way, the gas-to-water vapor ratio, used for the conversion of carbon monoxide, must be balanced against the vapor requirement for the regeneration of the absorbent, in order to obtain a process. implemented with a minimum of water vapor. This concept is further explained in the following text.

   If we assume that the process diagram

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 production of hydrogen intended for the manufacture of synthesis gas ammaniac is a conventional reforming process of hydrocarbon with steam (consisting of a primary and secondary reformer, auivi a conversion of the carbon monoxide, - ..

   elimination of carbon dioxide and methanization of ... residual carbon monoxide) and that the acceptable level of residual carbon monoxide to be methanized is not more than 0.3 mole%, the steam requirements of water to achieve this degree of conversion in a single stage of carbon monoxide transformation, including the usual cooling between stages, is 3.5 moles of steam per mole of dry feed gas when chromium oxide-iron oxide catalyst is used.



  However, for this same conversion, if two stages of carbon monoxide conversion are used with the removal of carbon dioxide after each stage, as shown in Figure 2, the total water vapor requirement is 1, 4 mole of water vapor per mole of dry gas leaving the reformer. When a process, combining the transformation of carbon monoxide at high temperature and low temperature, is used, as shown in Figure 4, a ratio of 0.7 water vapor to dry gas is the level. of water vapor required to achieve a carbon monoxide level of 0.3% in the feed gas to the methanizer.

   The practical water vapor levels required in the gas to supply the energy requirements for the regeneration of an ethanolamine solution for the removal of carbon dioxide are 1.4 0. A level of water vapor, required in the gas to supply the energy requirements for regenerating a sulfinol solution used for carbon dioxide removal, is 0.70. Thus, the process of Figure 2 can be balanced with a need for regenerative steam for older carbon dioxide absorbents, while the process of Figures 3 and 4 can be balanced with a need for regenerative steam. water

 <Desc / Clms Page number 10>

 
 EMI10.1
 regeneration for carbon ab8oants ?:: &: -yda.



  Figure 4 shows the 'açor 1; 7' ''; . > rJc ± .ié in accordance with the invention is used for the grLd; tion of ca, ammonia synthesis. The method and that of Figure 2 include secondary reformers 5. However, there is shown in Figure 4, separate converters 24 at high and low temperature. In addition, the methanisers, shown in Fig.- res 1 and 2, have been removed from Figures 3, 4 and 5. They are of course used.



   The advantages provided by the two-stage reaction conversion process in accordance with the invention and shown in Figures 3 and 4 are clearly apparent from the table below. In this table, a comparison of the design features of ammonia synthesis gas manufacturing processes is given.



  The process of Figure 4 is represented by Case I. Case II is a single stage process similar to that of Figure 1, but modified for the synthesis of ammonia by incorporating a secondary reformer, as shown in Figure 4. The reformer pressure level is in all cases 300 psig (21.09 kg / cm2) at the outlet of the reformer tubes. The catalyst used in the process of Case I is, in the first zone, a chromium-iron catalyst, and in the second zone, a zinc-copper catalyst. The chromium-iron catalyst is made by the oopreoipitation of carbonates and / or hydroxides of iron and chromium to form 9-11% Cr203 and 77-81% Fe2O3 which are mixed with 3-4% graphite.

   The zino-copper catalyst is described in example 1 of patent application n330,542. The chromium-iron catalyst, used in Case I, is also employed in the process of Case II comprising a single stage converter and operated with higher amounts of inert in the synthesis gas loop. Case III is a

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 process similar to that shown in Fig. 2, in which amine removal of carbon dioxide is provided after each stage of carbon monoxide conversion. with a view to obtaining greater conversion of last oe.



   Table 1
 EMI11.1
 
<tb> Case <SEP> I <SEP> Case <SEP> 11 <SEP> Case <SEP> 111
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> -CO <SEP> in <SEP> the <SEP> converter <SEP> of <SEP> 0.2 <SEP> mole <SEP>%, <SEP> 1.1 <SEP> mole <SEP> 0 , 5 <SEP> mole <SEP>%,
<tb>
<tb>
<tb> reaction <SEP> dry <SEP> base <SEP> dry <SEP> base <SEP> baee <SEP> dry
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Gas <SEP> outgoing <SEP> (@)
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> -Inertes <SEP> and <SEP> CH4 <SEP> to <SEP> the <SEP> output <SEP> 29.89 <SEP> 70.85 <SEP> 38.30
<tb>
<tb>
<tb>
<tb>
<tb> of the <SEP> methanizer, <SEP> in <SEP> moles / h <SEP> (0.96 <SEP> mole <SEP>% X2,1 <SEP> mole <SEP>%) <SEP> ( 1.21 <SEP> mole%)

  
<tb>
<tb>
<tb>
<tb>
<tb> -Gas <SEP> of <SEP> synthesis <SEP> necessity
<tb>
<tb>
<tb>
<tb> for <SEP> 300 <SEP> T / D <SEP> NH3
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> moles / hour <SEP> 3114.98 <SEP> 3361.01 <SEP> 3165.46
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Relative <SEP> quantity <SEP> 100% <SEP> 107.9% <SEP> 101.6%
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> -Hydrocarbons, <SEP> moles / hour
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> <SEP> requirements of process <SEP> 702.44 <SEP> 788.11 <SEP> 720.68
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> <SEP> fuel requirements <SEP> 205.63 <SEP> 331.68 <SEP> 451.77
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> total <SEP> needs <SEP> 998.07 <SEP> 1119.79 <SEP> 1172.45 <SEP> '<SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> quantity <SEP> relative <SEP> 100% <SEP> 112.2% <SEP> 117,

  47%
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> -Air, <SEP> moles / hour
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> <SEP> requirements <SEP> process <SEP> 988.47 <SEP> 1054.25 <SEP> 1001.99
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> <SEP> fuel requirements <SEP> 2957.70 <SEP> 3318.42 <SEP> 4510.74
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> total <SEP> needs <SEP> 3946.17 <SEP> 4372.67 <SEP> 5521.73
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> quantity <SEP> relative <SEP> 100% <SEP> 110.81% <SEP> 139.93%
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> -Water <SEP> requirements <SEP> steam <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> total, <SEP> pounds / hour <SEP> 69.570 <SEP> 75.200 <SEP> 114.350
<tb>
<tb>
<tb>
<tb>
<tb> (31.55 <SEP> T) <SEP> (34.86 <SEP> T) <SEP> (50.02 <SEP> T)
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> quantity <SEP> relative <SEP> 100% <SEP> 108,

  1% <SEP> 164.4%
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> -Dimension <SEP> relative <SEP> of the
<tb>
<tb>
<tb>
<tb> reformer <SEP> 100 <SEP> 112.9 <SEP> 103.0.
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>



  -Dimension <SEP> relative <SEP> of
<tb>
<tb>
<tb>
<tb> <SEP> converter <SEP> reaction <SEP> 100 <SEP> 125.1 <SEP> 194.6
<tb>
 

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 (*) Practical level of carbon monoxide in the gas leaving the reaction converter using the water vapor requirements of the carbon dioxide regeneration system to achieve full efficiency in the reaction converter.



   The comparison of the hydrocarbon requirements of the systems in Table 1 shows that the implementation of a high and low temperature process in accordance with the present invention allows the synthesis gas section of a manufacturing facility to be reduced by 'approximately 12% with respect to its size.



    - The advantages of the invention are better defined by the relative values. The relative amount of gas or the relative size of a reformer or converter is determined by the base
100 for the process according to the invention. It should be noted that cases II and III of an earlier type show that the relative quantities or dimensions are considerably larger. Thus, by determining by the base 100 the dimension of the reaction converter used in the process according to the invention, the dimension of the reaction converter for the process of case II is 125.1, while the dimension of the converter in the method of case III is 194.6. Other relative figures are given in Table 1.

   As can be seen, the invention results in improvement during the entire process.



   In order to better understand the invention, the reaction converter 24 of FIG. 3 is filled with the same ohromium-iron catalyst used in the converter 22 of FIG. 3. The table below gives a comparison of this. process with the process according to the invention, in which converter 24 contains a low temperature reaction catalyst. ;

   

 <Desc / Clms Page number 13>

 Table 2.
 EMI13.1
 
<tb> Case <SEP> IV <SEP> Case <SEP> V
<tb>
 
 EMI13.2
 31i-V 5up6- Lower bed Upper bed- 'Internal bed: 1r
 EMI13.3
 
<tb> laughter¯¯¯¯¯ <SEP> laughter
<tb>
 
 EMI13.4
 -type of cat-
 EMI13.5
 
<tb> lyser <SEP> high <SEP> high <SEP> high <SEP> low
<tb> temperature <SEP> '<SEP> temperature <SEP> temperature <SEP> temperature
<tb>
<tb> -Dimension <SEP> 1/4 "<SEP> T <SEP> 1/4" <SEP> T <SEP> 1/4 "<SEP> T <SEP> 1/4" <SEP> T
<tb>
 
 EMI13.6
  '. f6.35mm) (6.35mm) (6.35mm) (6.35mm)
 EMI13.7
 
<tb> -Quantity,
<tb>
<tb> cubic <SEP> feet <SEP> 160 <SEP> 160 <SEP> 160 <SEP> 160
<tb>
<tb>
<tb> (48m3) <SEP> (48m3) <SEP> (48m3) <SEP> (48m3)
<tb>
<tb>
<tb>
<tb> -Total <SEP> cost
<tb>
<tb>
<tb>
<tb> -Rate <SEP> to <SEP> en-
<tb>
<tb> trée, <SEP> 281.650 <SEP> 312.

   <SEP> 209 <SEP> 281.650 <SEP> 313.871
<tb>
 
 EMI13.8
 dry base SCPH (? 886.2m3) (8741.85m ') (7886.2m3) (8788.33)
 EMI13.9
 
<tb> -Input <SEP> report <SEP> 1.40 <SEP> 1.362 <SEP> 1.4 <SEP> 0 <SEP> 1.30
<tb>
<tb> Steam <SEP> of gas water
<tb>
 
 EMI13.10
 -Temperature 700 P 690 9 700 9 soo P
 EMI13.11
 
Input <tb> <SEP> 700 F <SEP> 690 F <SEP> 7000P <SEP> 500 F
<tb>
<tb> (3710C) <SEP> (366 C) <SEP> (371 C) <SEP> (271 C)
<tb>
<tb>
<tb>
<tb> -Cool down-
<tb>
<tb> ment <SEP> expected <SEP> 0.062 <SEP> ----
<tb>
<tb>
<tb>
<tb> -Temperature
<tb>
<tb> from <SEP> exit <SEP> 770 F <SEP> 7000P <SEP> 770 F <SEP> 520 F
<tb>
 
 EMI13.12
 (400oc) (571 C) (4000C) (251 C)

   
 EMI13.13
 
<tb> -Composition <SEP> of
<tb>
<tb>
<tb> gas <SEP> to <SEP> the input <SEP> to <SEP> the <SEP> output <SEP> to <SEP> the input <SEP> to <SEP> the <SEP> output
<tb>
<tb>
<tb>
<tb>
<tb>% <SEP> of <SEP>! vials
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> CO2 <SEP> 8.95 <SEP> 17.86 <SEP> 8.95 <SEP> 18.30
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> CO <SEP> 11.68 <SEP> 0.75 <SEP> 11.68 <SEP> 0.22
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> H2 <SEP> 57, ce <SEP> 61.28 <SEP> 57.08 <SEP> 61.48
<tb>
<tb>
<tb>
<tb>
<tb> .Inertes <SEP> 22,29 <SEP> 20,11 <SEP> 22,29 <SEP> 20,

  00
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> -Speed <SEP> spa-
<tb>
<tb>
<tb>
<tb> tiale <SEP> of the <SEP> gas
<tb>
<tb>
<tb> seo <SEP> to <SEP> entry <SEP> 1760 <SEP> 1760 <SEP> 1760 <SEP> 1760
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> -Pressure <SEP> opera-
<tb>
<tb>
<tb> toire <SEP> 262 <SEP> - <SEP> 262--
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> in <SEP> paig <SEP> (18.41 <SEP> kg / om2) <SEP> (18.41 <SEP> kg / om2)
<tb>
 

 <Desc / Clms Page number 14>

 
Various advantages of the invention emerge from Table 2. The hydrocarbons travel the same cycle length for a flow rate of 5% higher. A reformer operates at a 5% higher flow rate and with 5% less fuel or this reformer operates at 10% higher flow rate and with the same amount of fuel.

   The secondary reformer easily handles the additional flow. The use of the low temperature reaction catalyst according to the invention allows operation with a greater air-hydrocarbon ratio. The methaniser treats a flow rate 8 to 10% higher and the effective capacity of the compressors is increased by about 5%. By bypassing the compressors, the installation can easily produce 10% more ammonia. -
Another modification of the process according to the invention is shown in Fig. 5. In this process, a high temperature reaction conversion zone 36 is followed by two low temperature reaction conversion stages 38 and 50. The other units of the process, such as reformer 4, for example, have been described above.

   Through the process, a hydrogen purity of 99% is obtained at 1500 F (816 C), along with a pressure of 185 psig (13.03 kg / cm2) and a gas-to-water vapor ratio of 8. to 1; An additional 1.2 parts water to one part by volume reformer feed gas is added to the reaction converter to give a gas to water vapor ratio of 0.3 to 1 in this converter 50. The Water vapor is prepared in a waste heat recovery boiler 30 and results in a ratio of 3.5 to 1.

   The line for the gas-water vapor mixture (point 32) establishes the ratio 6.5 to 1 and the remainder, at least 1.5, is added to point 34, When the reaction converter 36 at high temperature is operating at 700 F, (371 C), low temperature converter 38 operates at 500 F (260 C) and low temperature converter 50 operates at 400 F (240 C). The feed gas is heated at the points 40, 42 and 44 and the gas, coming from the scrubber 46 removing the carbon dioxide,

 <Desc / Clms Page number 15>

   is heated to point 48 before being admitted to a second low temperature reaction converter, i.e. the third stage 50.

   After this third conversion in stage 50, the carbon dioxide is again removed, the scrubber giving the following gas:
Composition
CO 0.07
CO2 0.03
H2 99.80
CH4 0.10 Due to the use of a low temperature reaction system, only 1.2 parts of water vapor per part of hydrocarbon Introduced into the reformer is required at point 50 for purity of the hydrogen obtained., and this in addition to the gas-water vapor ratio 8: 1 provided for in points 30, and. However, if 38 and 50 were high temperature reaction converters, about 5 parts of steam, instead of 0.3, would be required, or an additional 4.7 parts. Fig. 5 thus shows that more than one low temperature reaction conversion stage can be used.

   Other modifications will be apparent to those skilled in the art. These modifications, as well as other changes, are within the scope of the present invention.



   CLAIMS.

** ATTENTION ** end of DESC field can contain start of CLMS **.

 

Claims (1)

1.-A process for producing hydrogen by reforming the gas with water vapor, followed by a reaction conversion of the gas, characterized in that it consists in increasing the quantity of hydrogen produced and comprises the passage, through two catalytic reaction zones @ of a gaseous stream of hydrogen obtained by reforming the hydrocarbons with water vapor, the first zone of the reaction conversion being carried out at a high temperature and the second zone at a low temperature, said zones being <Desc / Clms Page number 16> arranged in series and separated only by members for lowering the temperature between said sonea. 2. - Process for the production of hydrogen by reforming the gas with steam, followed by a reaction conversion of the formed gas, characterized in that it consists in increasing the flow rate of the reformer and comprises the passage, by two oatalytic reaction conversion zones of a gaseous stream of hydrogen obtained by. . the reforming of the hydrocarbons with steam, the first reaction conversion zone being carried out at a high temperature and the second zone at a low temperature, said zones being arranged in series and separated only by members for lowering the temperature between said zones, the high temperature zone being stressed at a temperature greater than 650 F (343 C), while the low temperature zone is carried out at a temperature lower than 600 F (316 C). 3. - Process according to claim 1, characterized in that the high temperature catalyst is an iron reaction catalyst active at 650-900 F (343-482 C) and in that the low temperature catalyst is an iron catalyst. copper-zinc at 350-600 P '(177-316 C) o containing zinc and copper in a ratio of 2 to 1 and less than 0.2% sodium. 4.- Process according to revendioation 2, characterized in that the high temperature stage is carried out at 650-800 F (343-427 C) using a catalyst oontaining 9 to 11% of Cr2O3 and 77 to 81% of Fe2O3, and in that the second stage is carried out at 350-500 F (177 to 260 C) using a catalyst containing zinc and copper in a ratio of 2 to 1 and less than 0.1 by weight of sodium. 5. - Process for producing hydrogen by steam reforming the hydrocarbons of a natural gas, followed by a reaction conversion resulting in carbon oxides, by washing the gas to remove carbon dioxide and by methanization <Desc / Clms Page number 17> of this gas resulting in carbon oxides, characterized in that the reformed gas mass by two stages of catalytic incubation! -on consisting of a first stage at high temperature and a second stage at low temperature, arranged in series and separated only by a heat removal stage, in that the high temperature stage is a stage using an active catalyst at a temperature of at least 650 F (343 C) and the low temperature stage is a stage using an active catalyst at a temperature below 600 F (316 C), and in that the conditions dU! reforming and conversion are such that the product gas contains less than 0.6 mole% of methanized waste carbon monoxide. 6. - Process according to claim 5, characterized in that the high temperature oatalyst is an iron reaction catalyst active at 650-900 F (343-482 C) and in that the low temperature catalyst is an iron catalyst. zinc-copper active at 350-600 F (177-316 C) containing zinc and drunk in a 2 to 1 weight ratio and less than 0.2% by weight sodium. 7. A process according to claim 5, characterized in that the high temperature stage is carried out at 650-800 F (343- 427 C) using a catalyst containing 9 to 11% of Cr2O3 and 77 to 81% of Fe2O3, and in that the second stage is carried out at 350-500 F (177-260 C) using a catalyst containing zinc and copper in a ratio of 2 to 1 and less than 0.1 by weight of sodium. 8. A process according to claim 5, characterized in that the reformed gas, originating from the low-temperature reaction conversion, goes through a stage of removing carbon dioxide and at least through an additional reaction conversion stage. at low temperature, followed by removal of carbon dioxide. 9. - Process for the production of hydrogen, during which <Desc / Clms Page number 18> natural gas reacts with water vapor in a reforming zone where the resulting carbon monoxide reacts with water vapor in a reaction conversion zone to form carbon dioxide which is removed by an absorbent solution, characterized in that the process comprises, under pressure and temperature conditions which are applied in the conversion and reforming zones and which produce a gas stream of hydrogen containing less than 0.6% of mole of residual carbon monoxide, and under a water vapor level of 0.7 mole of water vapor per mole of dry gas, an amount required to provide the energy necessary for the regeneration of a solution. of potassium carbonate absorbing carbon dioxide, passing the reformed gas first through a high temperature reaction conversion zone and then secondly through a low temperature reaction conversion zone, these zones being separated only by a heat removal stage, the high temperature zone being carried out at a temperature of about 650 F (343 C) and the low temperature zone at less than 600 F (316 C). 10. - The method of claim 9, characterized in that there is produced a gaseous stream of hydrogen containing less than 0.3 mol% of residual carbon monoxide.