Hydrogen Production

Coal gasification

Hydrogen is produced from coal through the process of gasification, or converting coal to a gaseous form. This is one of the principles of IGCC technology. Depending on the amount of steam used, syngas contains either carbon monoxide (CO) or carbon dioxide (CO₂). Hydrogen is the other byproduct, as demonstrated below.

Steam Reformation

Today most hydrogen is produced from natural gas. During this process, steam (H₂O) at high temperatures (1,300-2,000 °F) reacts with methane (CH₄) to produce synthetic gas, or syngas (fig 1). Additional hydrogen can be recovered from carbon monoxide using a water-gas shift reaction. At 265 °F, oxygen is stripped from the water molecules (steam) then rejoined with carbon monoxide (CO) to form carbon dioxide (CO₂). (fig 2)

Electrolysis

This process separates water into hydrogen and oxygen using an electric current. Electrolysis was first demonstrated by scientists in 1800. Two electrodes, usually made of platinum or stainless steel, are placed in the water. Hydrogen appears at the cathode, or negatively charged end. Oxygen will form at the positive end, or anode Electrolysis produces no harmful byproducts. However, it is currently an inefficient process, since the electricity used to produce hydrogen is considered more valuable than the hydrogen itself.

High-temperature electrolysis (HTE)

This process combines electrolysis with extremely high temperatures, resulting in higher efficiency. Experts believe this could only be achieved using nuclear reactors. These “Generation IV” reactors being tested for HTE operate between 1,560-1,830 °F, which is considerably higher than current nuclear reactors. Generation IV reactors are expected to go online around 2030.

Thermochemical production

This process is considered more efficient than high-temperature electrolysis. Thermochemical production requires no electricity, just heat. Three chemical reactions occur to produce hydrogen. This process is called the sulfur-iodine cycle. This process has been demonstrated in a laboratory, but not yet on a commercial scale. Though it is a fairly clean technology, this process tends to corrode equipment fairly quickly.

Biological hydrogen production

Hydrogen has been successfully produced using various organisms, creating Biohydrogen. If algae are deprived of sulfur they will begin producing hydrogen instead of oxygen, as they would in a normal photosynthesis reaction. Another process involves bacteria feeding on waste stock in a bioreactor. Bacteria feed on these hydrocarbons, then exhale hydrogen and CO₂.

Though these processes show promise, they are not yet feasible on a commercial scale.