In the blog post on fuel cells I have explained the way hydrogen and oxygen react to produce electricity with water as a by-product. There also some disadvantages with this method. The problems include the improper storing and distribution of hydrogen.
What is a fuel processor?
When comparing a hydrogen fuel cell to that of a gasoline fuel, the density of hydrogen is lesser. Meaning, it has a very less energy/unit volume compared to gasoline. This makes it practically impossible to store enough hydrogen and process it and hence make it drive a car to a maximum distance. Though this problem can be solved by using liquid hydrogen, which has a density more than normal hydrogen it has problems regarding its storing temperature. The storing temperature of liquid hydrogen is extremely low and also needs a high pressure. This problem makes the cost of production higher and also a difficulty in the mode of transportation.
Another important note about hydrogen is that its molecular structure is present in all natural gases like methanol, ethanol, and gasoline and so on. If these molecular structures could be easily removed from these natural fuels and thus used for making a fuel cell, all the above said problems could be solved.
Thus, a fuel processor, commonly known as a steam reformer is used to produce hydrogen from natural fuels. This is carried out by a device called reformer. This device is used to react the natural fuel along with steam at very high temperatures.
Need for Fuel Processors
We speak about using fuel cells because they do not create pollution in any way. They are also highly efficient. So, if the hydrogen is readily available for the fuel cells, it will turn out to be one of the biggest innovations of this century. So, the fuel processor is needed to provide pure hydrogen to make it practically applicable in fuel cells. By making the fuel processor possible, the transportation and storage will also become easier.
For this, the fuel processors should be highly efficient. Otherwise there will be no profit in replacing gasoline fuel with fuel cells.
Other than hydrogen experiments with methanol is also been carried out. Since methanol can be stored as a liquid fuel, it is easy to store in cars. It clearly replaces large tanks that are used for carrying gasoline.
The natural fuel called propane is also applicable for use in homes. Nowadays many houses have direct pipelines coming from propane tanks.
Working of a Fuel Processor / Steam Reformer
Steam reformers are mainly of two types. They are
1. Methanol Reformer
In a methanol reformer, methanol [CH3OH] is mixed with water at a very high temperature such that they vaporize. This vaporized mixture is later sent to a high temperature chamber and mixed with a catalyst. This process is carried out so as to extract as much hydrogen as possible and at the same time reduce the emission of pollutants like carbon monoxide [CO] as much as possible.
Both the hydrogen and carbon monoxide are produced in the heated chamber. Out of this the carbon monoxide is reacts with oxygen to form carbon-dioxide. Oxygen is formed by splitting water vapour into hydrogen and oxygen.
The chemical equation of the entire reaction is shown below.
CH3OH – CO + 2H2
H2O + CO – CO2 + H2
Methanol – CH3OH
Hydrogen – H2
Carbon Monoxide – CO
Water – H2O
2. Methane Reformer
Natural gases contain molecules of methane. This methane is extracted and then a similar process like a methane reformer is carried out. The methane present in the natural gas is extracted and then reacted with water vapour to get carbon monoxide and hydrogen. Then the carbon monoxide is converted to carbon dioxide like the methanol reformer. The reactions taking place in the process is shown below.
CH4 + H2O – CO + 3H2
H2O + CO – CO2 + H2
Methane – CH4
Water – H2O
Carbon Monoxide – CO
Hydrogen – H2
Combination of fuel cells and fuel processors
As the fuel cells have to provide the electricity constantly, the fuel processors have to work in parallel with it.
Suppose you want to drive a car that is powered with fuel cells. When the accelerator is pressed, the controller of the motor supplies current to the electric motor. This helps the electric motor in generating more torque. For the controller to supply power, the fuel call has to work in order to make electricity. When the amount of hydrogen becomes less, the fuel processor starts its mechanism and extracts the hydrogen from methanol. Though such a system has never been adapted properly, we can expect this to happen soon.
Drawbacks of Fuel Processors
Though the amount of carbon dioxide is not emitted as much as other technologies, it is still considered a threat to global warming. As fuel processors are used to provide the hydrogen, the emission of CO2 is sure. If the pure hydrogen could be used this disadvantage would not have happened.
Though the efficiency of the fuel processor is less, the overall efficiency when connected to a fuel cell is very less. Most of the energy is wasted in the form of heat and high pressure.
PS: Here is a good resource to learn about the working of fuel cells.
TAKE A LOOK : WORKING OF FUEL CELLS
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