Hydromethanation

Hydromethanation, [hahy-droh- meth-uh-ney-shuhn] is the process by which methane (the main constituent of natural gas) is produced through the combination of steam, carbonaceous solids and a catalyst in a fluidized bed reactor. The process, developed over the past 60 years by multiple research groups, enables the highly efficient conversion of coal, petroleum coke and biomass (e.g. switchgrass or wood waste) into clean, pipeline quality methane.

The chemistry of catalytic hydromethanation involves reacting steam and carbon to produce methane and carbon dioxide, according to the following reaction:

2C + 2H₂O -> CH₄ + CO₂

The process utilizes a specially designed reactor and depends upon a proprietary metal catalyst to promote chemical conversion at the low temperatures where the water gas shift reaction and methanation take place.

When a feedstock treated with the catalyst is introduced into this reactor and mixed with steam, three reactions occur that efficiently convert the feedstock into methane.

C + H₂O -> CO + H₂

CO + H₂O -> H₂ + CO₂

2H₂ + C -> CH₄

The combination of carbon (C) from the carbon feedstock, water (H₂O) from steam, and the catalyst, produces pure methane and a pure stream of carbon dioxide (CO₂) which is 100% captured in the system and available for sequestration. The overall reaction is thermally neutral, requiring no addition or removal of heat, making it highly efficient.

The development of hydromethanation is an example of process intensification, where several operations are combined into a single step to improve overall efficiency, reduce maintenance and equipment requirements, and lower capital costs.

In addition to methane, hydromethanation produces a high-purity stream of carbon dioxide (CO₂), an odorless, colorless greenhouse gas. This CO₂ stream is fully captured in the process and can be prevented from entering the atmosphere using a process called sequestration. The CO₂ can be injected into underground oil reserves, through a process called enhanced oil recovery (“EOR”), or geologically sequestered.

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