How fuel Reformers Work

Reforming Methanol

The molecular formula for methanol is CH3OH. The goal of the reformer is to remove as much of the hydrogen (H) as possible from this molecule, while minimizing the emission of pollutants such as carbon monoxide (CO).
The process starts with the

• vaporization of liquid methanol and water
• Heat produced in the reforming process is used to accomplish this.
• This mixture of methanol and water vapor is passed through a heated chamber that contains a catalyst.
• As the methanol molecules hit the catalyst, they split into carbon monoxide (CO) and hydrogen gas (H2):
  CH3OH => CO + 2H2
• The water vapor splits into hydrogen gas and oxygen;
• this oxygen combines with the CO to form CO2.

In this way, very little CO is released, as most of it is converted to CO2.

H2O + CO => CO2 + H2

Reforming Natural Gas

Natural gas, which is composed mostly of methane (CH4), is processed using a similar reaction.

The methane in the natural gas reacts with water vapor to form carbon monoxide and hydrogen gases.
CH4 + H2O => CO + 3H2

Just as it does when reforming methanol, the water vapor splits into hydrogen gas and oxygen, the oxygen combining with the CO to form CO2.

H2O + CO => CO2 + H2

• Neither of these reactions are perfect; some methanol or natural gas and carbon monoxide make it through without reacting.
• These are burned in the presence of a catalyst, with a little air to supply oxygen.
• This converts most of the remaining CO to CO2, and the remaining methanol to CO2 and water.

Various other devices may be used to clean up any other pollutants, such as sulfur, that may be in the exhaust stream.

It is important to eliminate the carbon monoxide from the exhaust stream for two reasons:

• First, if the CO passes through the fuel cell, the performance and life of the fuel cell are reduced;
• second, it is a regulated pollutant, so cars are only allowed to produce small amounts of it.

How the Fuel Processor and Fuel Cell Work Together

In order to create power, several systems must work together to provide the required electrical output. A typical system would consist of an electrical load (such as a house, or an electric motor), a fuel cell and a fuel processor.

Let's take the case of a fuel-cell-powered car. When you step on the gas (hydrogen) pedal, several things happen at about the same time:

• The electric motor controller starts supplying more current to the electric motor, and the electric motor generates more torque.
• In the fuel cell, more hydrogen is reacted, producing more electrons, which make their way through the electric motor and controller, keeping up with the increased power demand.
• The fuel processor starts pumping more methanol though its system, which creates more hydrogen.
• Another pump increases the flow of hydrogen going to the fuel cell.

The Downside of Fuel Processors

Fuel processors also have drawbacks, including pollution and overall fuel efficiency.

Pollution

Although fuel processors can provide hydrogen gas to a fuel cell while producing much less pollution than an internal combustion engine, they still produce a significant amount of carbon dioxide (CO2). Although this gas is not a regulated pollutant, it is suspected of contributing to global warming.

If pure hydrogen is used in a fuel cell, the only byproduct is water (in the form of steam). No CO2 or any other gas is emitted.

But because fuel-cell-powered cars that use fuel processors emit small amounts of regulated pollutants, such as carbon monoxide, they will not qualify as zero emissions vehicles (ZEVs) under California's emissions laws.

Right now, the main technologies that qualify as ZEVs are the battery-powered electric car and the hydrogen-powered fuel-cell car.

Instead of trying to improve fuel processors to the point where they will emit no regulated pollutants, some companies are working on novel ways to store or produce hydrogen on the vehicle.

• Ovonic is developing a metal hydride storage device that absorbs hydrogen somewhat like a sponge absorbs water.
• This eliminates the need for high-pressure storage tanks, and can increase the amount of hydrogen that can be stored on a vehicle.

Another downside of the fuel processor is that it decreases the overall efficiency of the fuel-cell car. The fuel processor uses heat and pressure to aid the reactions that split out the hydrogen.

• Depending on the types of fuel used, and the efficiency of the fuel cell and fuel processor, the efficiency improvement over conventional gasoline-powered cars can be fairly small.

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