Summary Of Hydrogen Production Methods [

If hydrogen production processes are compared, the interdependence of efficiency, capital investment and value of the byproduct has to be taken into account. From the reaction equations, it can be derived that an essential part of the hydrogen is gained from water, e.g. 50% in the case of steam reforming of natural gas plus CO conversion. On the other hand, all carbon in the raw materials is finally converted to CO2 and released into the atmosphere. The least unfavourable process is steam reforming with a CO2 to H2 ratio of 0.25, and the worst in coal gasification with a respective ratio of 1. The use of heavier raw materials is connected with a loss of efficiency since a larger mass of C-carriers and water need to be heated up to reaction temperature.

Table B-2 Characteristics of splitting process for hydrogen production from ^ [46]

Splitting process

Energy required [kWh/Nm3 of H2]

Status

Efficiency (%)

Cost relative to SMR

Fraction of production [%]

in theory

in practice

Steam methan reforming (SMR)

0,78

2-2.5

mature

70 - 80

1

48

Partial oxidation of heavy oil

0,94

4,9

mature

70

1,8

30

Naphta reforming

mature

Coal gasification

1,01

8,6

mature

60

1.4 - 2.6

18

Partial oxidation of coal

mature

55

Chloralkali electrolysis

mature

byproduct

4

Water electrolysis

3,54

4,9

R&D -mature

27

5-10

Thermochemical cycles

R&D

35-45

6

Biomass conversion

R&D

2-2.4

-

Photolysis

R&D

< 10

Reforming of natural gas and partial oxidation of heavy oils are presently the least expensive and most frequently applied methods of hydrogen production (see Table B-2). Meanwhile, electrolysis is the most expensive process unless cheap electricity is available. Production of hydrogen from coal gasification is not an ideal alternative in term of the necessary reduction of CO2 emissions in the future, because the reduction is no higher than 20-30% compared with the coal feed. In this respect, gasification of CO2-neutral biomass would be better alternative, although non-CO2 gases with a global warning potential are emitted with its combustion [96].

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