Page 67 - Industrial Plant 2020

ydrogen (H ) is the most abundant Properties of Hydrogen as fuel
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element in nature and its use in The most common gaseous fuel used in industrial
industrial fired boilers for steam boilers is natural gas. The design criteria for boilers
generation can play an important role using this gas are well consolidated. However, respect
in the decarbonisation process. to natural gas, hydrogen has different characteristics
HHydrogen combustion produces that impacts boiler design. It has a higher energy
only water vapour and hence its use in co-firing with content, wide flammability range and high flame speed
natural gas or standalone firing contributes to reduce (ten times higher than natural gas) Table 1.
carbon dioxide emission.
Hydrogen like fuel is not a new fact; since many years
industrial fired boilers, especially for refineries complex, Macchi industrial boiler types
have been operated with fuels containing quantity of There are two fundamental types of boilers: fire tubes
hydrogen in the range of 20% - 40% volume. In this and water tubes. In this paper, only water tube boilers
paper, state of art of boiler design features with higher are analysed since generally used in Oil & Gas and
quantity of hydrogen is discussed. petrochemical plants. Steam production range for
Many topics of boiler design are affected by its use and above industries are within 50 t/h up to 450 t/h with
specifically focus on burners, combustion chambers steam pressure variable from 10 barg up to 120 barg
and control are considered hereinafter. Finally, an and temperature up to 530 °C. Even if there are many
outlook about the application as standalone firing is type of boilers to respond high degree of customization
evaluated. and flexibility required by End User, the three most
common are shown in the Table 2.

Properties Natural gas Hydrogen (H ) Impact on boiler design
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Lower heat calorific value MJ /Nmc 35-36 Approx. 10,8 Different fuel flow to boiler, control system, burners
Normal Density kg/Nmc Approx. 0,72 0,09 Burner design
Theoretical combustion air, kg/Nmc 12,0-13,0 Approx. 3,0 Combustion, furnace and control system
Flammability limit %vol 5-15 4-75 Burner design and furnace
Flame speed cm/s Approx. 40 cm/s Approx. 300 cm/s Burner design
Ignition Energy (mJ) 0.28 0.01 Burner design
Flame temperature K Approx. 2200 Approx. 2400 Furnace design

Table 1- Properties of natural gas and hydrogen

Bi-drum horizontal path boiler with frontal Bi-drum vertical path boiler with frontal Single drum vertical path boiler with frontal
firing. Macchi model TITAN-M firing. Macchi model MVF firing-Macchi Boiler MRD type
Steam production : 10 t/h – 350 t/h Steam production:100 t/h–500 t/h Steam production: 100 t/h–500 t/h
Steam temperature up to 525 °C Steam temperature up to 525 °C Steam temperature up to 540 °C
Pressure up to 130 barg Pressure up to 130 barg Pressure up to 150 barg
Fuels: All gaseous and liquid fuels. Fuels: All gaseous and liquid fuels. Fuels: All gaseous and liquid fuels.

Table 2

IndustrIal Plants - May 2020
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