Cracker ammoniac NH3, générateur d'hydrogène pour la génération d'hydrogène H2, formant le gaz H2/N2

Ammonia Cracker
Crystec Technology Trading GmbH

Ammonia Cracker for the Generation of Forming Gas.

An ammonia cracker, NH3-Cracker or hydrogen generator is used for the production of forming gas. Hydrogen and Nitrogen are generated in a cost effective way in a volume ratio of 3 : 1 or in a weight ratio of 14 : 3. Capacities from 5m3/h to 250m3/h are available. The nitrogen in the forming gas can optionally be removed.

The NH3 is coming from bottles or from an ammonia tank. The ammonia gas is pre-heated in a heat exchanger and vaporizer and then cracked in the main furnace unit. The furnace is electrically heated.

ammonia cracker, graphic

The dissociation of ammonia gas NH3 takes place at a temperature of 800°C in the presence of a special nickel catalyst in an electrically heated furnace.
2 NH3 arrow N2 + 3 H2
The heat exchanger is used for better energy efficiency. While the hot cracked gas is cooled down, the ammonia gas is preheated using the countercurrent principle.

Gas Generator (SinceGas)
  • Stable gas generation: The electrical heater can generate a kontinous gas flow.
  • Siemens programmable logic controller (PLC)
  • Safety feature: Excess temperature protection, over pressure, thermocouple burnt alarm, etc. can maintain the system safe.
  • Small footprint, easy operation: Operation switch installed on front panel.
  • The cracker is characterized by its low power consumption and operating costs.
  • Implementation and design can be adapted within certain limits according to customer requirements
  • Full CE Certification

Wasserstoffgenerator, Formiergasgenerator

As a result of complete dissociation into hydrogen and nitrogen, very little undissociated ammonia remains and the dew point temperature of the resulting gas is very low (well below -10°C).

Gas Purifier

As an option and in order to reduce the dew point of the generated forming gas further, a special forming gas purifier is available. Using molecular sieve technology, the dew point of the generated gas can be reduced to -70°C. Two adsorber units are working in parallel, one for adsorbing moisture and un-cracked ammonia from the forming gas and the other one is heated for regeneration. Gas flow is changed regularly and automatically.


Gas Properties

The gas generated by the dissociation of ammonia is forming gas. It consists of 75 Vol% hydrogen and 25 Vol% nitrogen.

Description Ammonia NH3 Hydrogen H2 Nitrogen N2
Molecular Weight

17,03

2,0158

28,0134

Boiling Point (BP) in °C

-33,35

-252,87

-195,8

Liquid Density at BP in kg/m3

682,1

70,0

804,0

Vapor Density at BP in kg/m3

0,8906

1,329

4,613

Density at RT in kg/m3

0,7710

0,0899

1,2506

Heat of Vaporization in kJ/kg

1368,2

451,9

199,2

Solubility in cold water in g/100ml

89,9

-

-

Cp in kJ/kg (1 atm, RT)

2,188

14,2

1,038

Cp/Cv (1 atm, RT)

1,31

1,41

1,40

Product types

The ammonia crackers are available in several sizes; the information relates to standard pressure and standard temperature. Please note that the amount of gas doubles during the process. This means that 1 m3/h of ammonia produces 2 m3/h of forming gas. Therefore it is important to specify whether the gas flow is desired inlet gas flow(NH3) or outlet gas flow (N2; H2). The ammonia consumption and hydrogen generation are listed in the following conversion table. Our cracker models are named after the amount of forming gas generated(gas output).

Model

Ammonia consumption
(m3/h NH3)

Ammonia consumption
(kg/h NH3)

Forming gas production
(m3/h N2;H2)

Hydrogen production
(m3/h H2)

Hydrogen production
kg/h H2)

5 N m3/h

2,5

1,9

5

3,8

0,3

10 N m3/h

5

3,9

10

7,5

0,7

20 N m3/h

10

7,7

20

15

1,3

30 N m3/h

15

11,6

30

22,5

2

50 N m3/h

25

19,3

50

37,5

3,3

60 N m3/h

30

23,1

60

45

4

70 N m3/h

35

27

70

52,5

4,7

80 N m3/h

40

30,8

80

60

5,3

90 N m3/h

45

34,7

90

67,5

6

100 N m3/h

50

38,5

100

75

6,7

110 N m3/h

55

42,4

110

82,5

7,3

120 N m3/h

60

46,2

120

90

8

130 N m3/h

65

50,1

130

97,5

8,7

140 N m3/h

70

53,9

140

105

9,3

150 N m3/h

75

57,8

150

112,5

10

160 N m3/h

80

61,6

160

120

10,7

170 N m3/h

85

65,5

170

127,5

11,3

180 N m3/h

90

69,3

180

135

12

190 N m3/h

95

73,2

190

142,5

12,7

200 N m3/h

100

77

200

150

13,4

210 N m3/h

105

80,9

210

157,5

14

220 N m3/h

110

84,7

220

165

14,7

230 N m3/h

115

88,6

230

172,5

15,4

240 N m3/h

120

92,4

240

180

16

250 N m3/h

125

96,3

250

187,5

16,7

The conversion of the ammonia to hydrogen and nitrogen (volume ratio 3: 1) in the cracker is almost complete. Only small amounts (<30ppm) of ammonia gas remain in the cracked gas.
For the production of larger amounts of forming gas, several units can be installed in parallel.

Wasserstoff Aufreinigung

So-called Pressure Swing Adsorption (PSA) is used to remove nitrogen and therefore purify hydrogen (H2). This is based on a physical process that makes use of the different adsorption properties of different gases in order to separate them. Depending on the implementation, it is also possible to separate other gases such as oxygen or carbon dioxide.
To separate nitrogen from hydrogen and to generate high-purity hydrogen, porous materials such as molecular sieves or zeolite are used. At a certain pressure, the gas mixture flows through the molecular sieve designed for this application. Due to the stronger interaction of hydrogen with the molecular sieve, hydrogen is collected on the surface of the molecular sieve. The second gas (nitrogen), on the other hand, is not adsorbed. After the molecular sieve has reached its capacity limit, the gas flow is diverted to another molecular sieve. Due to a pressure reduction and the associated significantly weaker interaction between molecular sieve and hydrogen, the now purified hydrogen can be released from the first molecular sieve. After that, the first molecular sieve is available for purification again. The system is controlled by a program logic control (PLC). This allows continuous purification to be achieved.

PSA Hydrogen Purification (SinceGas)
  • Our PSA systems can be customized for different pressures, gas flows and purities.
  • A gas flow of up to 600 m3/h per system is possible
  • The PLC controlled system ensures stable gas generation
  • A purity between 99% and 99,999% is possible
  • The system is fully automated
  • The molecular sieves are compactly filled and have a long life expectancy
  • Full CE Certification

Wasserstoff Aufreinigung

Applications for dissociated ammonia

Annealing furnace

The forming gas is used in conveyer furnaces and in tube furnaces for anneal processes in a reducing atmosphere, brazing, sintering, deoxidation, and nitrization. You will find more details about these furnaces in our Koyo Thermo Systems product overview.

Further application for forming gas
  • Brazing
  • Sintering
  • Deoxidization
  • Nitrization
  Metal anneal:
  • Stainless steel wire anneal
  • Metal powder anneal
  • Bimetal products anneal
  • Hydrogenation of organic compounds
  • Galvanization
  • Production of Forming Gas

Fuel Cell

Hydrogen is also required for fuel cells. The storage of hydrogen as ammonia has clear advantages. In addition to an increased energy density, ammonia only needs to be liquefied at -33° C instead of -253° C for hydrogen and can be stored at moderate pressures. Ammonia thus offers an elegant solution for transporting hydrogen and an environmentally friendly alternative to fossil fuels. The above-mentioned hydrogen purification can also provide high-purity green hydrogen via ammonia. For this application you need an ammonia cracker and a PSA purifier. In the following table you will find the most popular fuel cells that use hydrogen.

Name Type Electrolyte Charge carrier Fuel gas (Anode) Oxidizing agent (Cathode) Temperature (°C) Efficiency Application
Polymer electrolyte membrane fuel cell
for hydrogen (PEMFC)
Acidic low temperature oxyhydrogen gas cell Proton-conducting polymer membrane
(PEM)
Hydronium ion (H3O+) Hydrogen (H2) Oxygen (O2) or air; humidified 60-70 Cell: 50-68 Production vehicles, thermal power stations,
Supplies for electronic
Solid oxide fuel cell (SOFC) High temperature oxyhydrogen gas cell Oxide ceramic electrolyte
(ZrO2 + Y2O3)
Oxide ion (O2-) Hydrogen (H2) Atmospheric oxygen (O2) 800-1000 Cell: 60-65 Thermal power stations (up to 250kW)
Galvanic fuel cell
with alkaline electrolyte e.g. (AFC)
Alkaline low temperature oxyhydrogen gas cell e.g. Potassium hydroxide solution, 30% Hydroxide ion (OH-) Pure hydrogen (H2) Pure oxygen (O2) 20-90 Cell: 60-70 Small plants (bis 150kW); Submarine drive
Galvanic fuel cell
with acidic electrolyte e.g. (PAFC)
Acidic low temperature oxyhydrogen gas cell e.g. Concentrated phosphoric acid Hydronium ion (H3O+) Hydrogen (H2)
Atmospheric oxygen (O2) 150-220 Cell: 55 Stationary cogenerations of power and heat

Crystec will be pleased to engineer a cost effective system to satisfy your most demanding and exacting requirements.