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Syngas

Explore synthesis gas, the primary product of FastOx gasification, its uses, and the specific type seen in the FastOx process.

What is Syngas?

Syngas, short for “synthesis gas”, is a term used to describe a gas consisting primarily of carbon monoxide (CO) and hydrogen (H2). This energy-dense gas is similar in application to natural gas in that it can be processed in a variety of ways to make useful end products and commodities. The most common applications for syngas are production of heat, electricity, diesel, hydrogen gas and chemicals.
Natural gas is typically used to produce these products in large volumes; however, the production of natural gas from fossil fuels requires capital intensive operations, such as fracking, treatment, or reformation of crude oil. The CO2 emitted during the production of commodity products has the net effect of increasing the background levels of CO2 in the atmosphere, which is strongly-linked to the global climate change crisis.
The compositions of syngas vary according to its source. For example, syngas produced using air (as in low-temperature gasification of solid, liquids and gaseous feedstocks) will contain significant quantities of nitrogen (N2), as the air injected into the process contains about 80% N2 by volume. FastOx® gasification, which inject oxygen as opposed to nitrogen-rich air, reduces the amount of nitrogen present in the system.

 

 

Syngas from FastOx Gasification

Sierra Energy anticipates that syngas produced from FastOx gasification will have the following range of compositions (% by volume or % by mole) after cleaning and before end product conversion:

CO 48-66%
H2 18-32%
CO2 5-15%
CH4 0.5-12%
Ethane <2%
Propane <2%
Nitrogen 0.5-3%
Oxygen <1%
Argon 0.5-2.5%

 

The exact composition and volume flow rate (SCFM or Nm3/hr) will depend on the exact feedstock (material being gasified), the configuration of the plant and the goals/priorities of the project developer. The typical energy content of this dry, clean syngas will be in the range of 7 to 14 MJ/kg, or 172.2 to 344.3 BTU/scf.
Syngas typically comes out of the gasifier at approximately 300°C (570°F), before it enters the polisher module, where it will convert any condensable hydrocarbons and other compounds into simple gaseous compounds (CO, CO2, H2, H2O and N2). This polishing process ensures enduring and stable operation of the FastOx system by recovering the maximum amount of energy from the original feedstock.

 

 

Recoverable Syngas Constituents

No gasification system is perfect. Of the materials that enter, some is irrecoverable. They may be driven off prematurely or constitute undesirable components not suitable for back end processes. Any undesirable compound will be filtered out during the gas cleaning and conditioning stage. These filtered-out materials are referred to as secondary byproducts.
While most of these secondary byproducts can be injected back into the gasifier vessel to fully drive them to their desirable destinations (either suitable syngas or inert stone), some constituents can be syphoned off in large enough quantities to be sold as commodities.
The following are examples of components present in syngas from FastOx gasification that can be recovered as secondary byproducts.

Particulate Matter (Ash, Salts, fixed carbon/soot)

Particulate matter becomes present in the syngas due to its “loose binding” with surrounding elemental neighbors. This loosely bonded nature results in these (mostly) inorganic materials being driven off as they enter the gasifier instead of being captured in the vitrified, inert stone.
These materials can be recovered from the syngas in a number of plant configurations, such as cyclonic removal, scrubbing removal, or filter removal. The removed particulates can be re-injected into the FastOx gasifier vessel to produce additional syngas or captured within the slag. This practice is similar to what is commonly done in the power and steel industries.

Sulfur

In large enough quantities, sulfur can be recovered from the syngas using a continuous process, as in Merichem’s LO-CAT equipment. A Claus reaction can then be used to produce purified elemental sulfur from hydrogen sulfide (H2S). The practice of producing sulfur as a byproduct is common in the petroleum industry (refineries and other hydrocarbon processing plants) and typically constitutes the vast majority of sulfur produced worldwide. Capturing sulfur in sufficient volumes enables the manufacturing and production of sulfuric acid, medicine, cosmetics, fertilizers, and rubber products, as well as some pesticides.

Spent Catalysts

The majority of catalysts that could potentially be found in FastOx gasification systems are typically made out of specific transition metals such as copper, cobalt, iron, titanium, and ruthenium. Given the nature of these metals, it is possible to recover them through their collection in inert stone. However, the exact nature of this recovery will depend on the nature of the catalyst beds used in the process. It is possible some catalysts will be completely consumed in the process.