Effect of fuel composition on greenhouse gas emissions – Hydrogen technology solutions

Effect of fuel composition on greenhouse gas emissions

Effect of fuel composition on greenhouse gas emissionsSavitenko M. A.
Rybakov B. A.

Article 7, paragraph 1. Draft Law No. 1116605-7 of the Federal Law “On Limiting Greenhouse Gas Emissions” states:

“The classification of legal entities and individual entrepreneurs as regulated organizations is carried out on the basis of the criteria established by the Government of the Russian Federation in relation to economic or other activities accompanied by greenhouse gas emissions, the mass of which is equivalent to 150 thousand tons of carbon dioxide per year or more for the period up to 2024 and 50 thousand tons of carbon dioxide per year or more after 2024. The Government of the Russian Federation approves lists of economic activities accompanied by greenhouse gas emissions and indicators of such activities.»

This article provides an estimate of specific carbon dioxide emissions for some fuels.

Consider four types of fuel:

  1. Hydrogen, lowest calorific value-120 MJ / kg = 33.33 kWh/kg;
  2. Methane, lowest heat of combustion-50 MJ / kg = 13.89 kWh/kg;
  3. Natural gas, lowest calorific value-46.8 MJ / kg = 13.00 kWh / kg;
  4. Carbon, lowest heat of combustion – 34 MJ/kg = 9.44 kWh/kg.

When burning hydrogen, no carbon dioxide is produced, but water vapor is formed.

When burning 1 kg of hydrogen, 9 kg of water vapor is formed.

Burning 1 kg of methane produces 2.75 kg of carbon dioxide and 2.25 kg of water vapor.

When burning 1 kg of natural (pipeline) gas, 2.64 kg of carbon dioxide and 2.09 kg of water vapor are formed.

The composition of natural gas (GHG) is shown in table 1:

Component Mol. mass % Mol.  С,

%  mass.

 

С/(С+Н)

kg of CO2 per kg of GHG kg of H2O per kg of GHG
O2 32 0,007
N2 28,016 2,482
CO2 44,011 0,281
H2 2,016 0,001
CH4 16,042 93,333 65,46 0,75 2,40 1,964
C2H6 30,068 2,852 4,00 0,8 0,15 0,090
C3H8 44,094 0,706 1,48 0,82 0,05 0,030
C4H10 58,12 0,23 0,64 0,83 0,02 0,011
C4H10 58,12 0,07 0,20 0,83 0,01 0,000
C5H12 72,146 0,01 0,04 0,83 0,00 0,000
C5H12 72,146 0,007 0,02 0,83 0,00 0,000
C6H14 86,172 0,006 0,03 0,84 0,00 0,000
4,003 0,015
Average value  

 

 

71,87

 

0,755

 

2,64

 

2,09

Burning 1 kg of carbon produces 3.67 kg of carbon dioxide.

The ratio of the mass fraction of carbon to the total mass fraction of carbon and hydrogen for different fuels is shown in Table 2:

Fuel Hydrogen Methane gas Natural gas Carbon
С/(С+Н) 0 0,75 0,755 1

Since the fuels listed above have different values of calorific value, we will use the lowest calorific value of hydrogen as a base for comparing specific greenhouse gas emissions. In this case, to produce 120 MJ = 33.33 kWh of thermal energy, 1 kg of hydrogen, 2.4 kg of methane, 2.57 kg of natural gas and 3.53 kg of carbon will be required.

Burning 2.4 kg of methane produces 6.6 kg of carbon dioxide and 5.4 kg of water vapor.

Burning 2.7 kg of natural gas produces 6.8 kg of carbon dioxide and 5.64 kg of water vapor.

When burning 3.67 kg of carbon, 12.95 kg of carbon dioxide is produced.

Let’s summarize these values in Table 3:

Fuel type Fuel consumption,

kg

CO2 emissions,

kg

H2O emissions,

kg

Hydrogen 1 0 9
Methane gas 2,4 6,6 5,4
Natural gas 2,7 6,8 5,64
Carbon 3,67 12,95 0

 

A number of foreign publications note that greenhouse gas No. 1 is water vapor, not carbon dioxide.

In the article “Rising Levels of Human-Caused Water Vapor in the Troposphere will Intensify Climate Change Projections”, written by Rick Pantaleo in 2014, it is reported that scientists consider water vapor, which is the most important ingredient for maintaining life on Earth, a key driver of global warming.

Research conducted by scientists from the University of Miami Rosenstiel School of Marine and Atmospheric Science, confirmed that the increase in water vapor in the troposphere – a layer of the atmosphere extending at an altitude of 5 to 20 km from the earth’s surface – will play an increasing role in climate change in the coming years.

Researchers from Florida have demonstrated that the increasing amount of water vapor in the atmosphere is caused by human activity.

Scientists decided to find out what caused the 30-year trend of increasing water vapor in the upper layers of the troposphere.

They collected data from satellites of the US National Oceanic and Atmospheric Administration and compared it with climate models that predicted the circulation of water between the ocean and the atmosphere.

This allowed the researchers to determine whether or not the observed changes in the amount of water vapor in the atmosphere were caused by natural causes or the result of human activity.

Experiments have found that natural causes, such as volcanic activity or changes in solar activity, cannot explain the increase in water vapor in the upper troposphere.

Therefore, they assumed that these changes are the result of human activity.

The article “The Importance and Nature of the Water Vapor Budget in Nature and Models”, Lindzen, Climate Sensitivity to Radioactive Perturbations: Physical Mechanisms and Their Validation (1996) provides quantitative data on the effect of water vapor and carbon dioxide concentrations on the greenhouse effect.

The author of this article reports that in a clear sky, the contribution of water vapor in the reflection of long-wave radiation is 75 W / m2, while the contribution of carbon dioxide is only 32 W/m2.

That is, the contribution of water vapor to the greenhouse effect exceeds the contribution of carbon dioxide to the greenhouse effect by 2.34 times.

Russian researchers in their publications also claim that water vapor is an important greenhouse gas.

In the article “Spectroscopy of the greenhouse effect” (Sorovsky Educational Journal, volume 7, No. 10, 2001), Tonkov M. V. writes “The main absorbing gases in the Earth’s atmosphere are water vapor and carbon dioxide”.

Ptashnik I. V. in his dissertation on the topic “Continuous absorption of water vapor in the centers of near-infrared bands” (2007) reports that “water vapor, despite its relatively small partial content in the Earth’s atmosphere, is the most important component that determines its radiation balance. The water vapor absorption bands and the areas between them (the” wings “of the bands), called the” transparency windows ” of the atmosphere, absorb up to 70-80% of the solar radiation falling on the atmosphere. Water vapor is also one of the most important greenhouse gases in the atmosphere.”

“Scientific Russia” (2013) reports that ” water is one of the most important atmospheric molecules. Making up only about 0.33% of the mass of the atmosphere, water is responsible for about 70% of the radiation absorbed by the planet. The amount of absorption strongly depends on how the total amount of water is distributed in its many forms(individual molecules, clusters, drops, snowflakes).”

In his dissertation for the degree of Doctor of Physical and Mathematical Sciences “Experimental study of the induced and continuous absorption of IR radiation by the main atmospheric gases” (Obninsk 2014), Baranov Yu. V. concludes that “the binary absorption coefficients for a mixture of carbon dioxide with water vapor are approximately an order of magnitude higher than the values for pure CO2”.

“Scientific Russia” (2018) in the article “Nizhny Novgorod physicists have understood the reason for the excessive absorption of energy by water vapor reports that” Water vapor strongly absorbs electromagnetic waves in the range from radio to ultraviolet. This makes it the main greenhouse gas of the atmosphere, and therefore a factor that has a significant impact on the Earth’s climate.”

Despite the large number of publications in our country and abroad, no official document refers to water vapor as a greenhouse gas.

According to the authors of this article, when developing new power plants and boiler units and modernizing existing power plants, it is necessary to use the condensation of water vapor from flue gases, which will both increase the fuel heat utilization factor (KITT) and reduce greenhouse gas emissions into the atmosphere.

In addition, the resulting condensate after its treatment can be used as make-up water, as well as for the production of hydrogen.