Steam reforming is a process in which hydrocarbon feedstocks are converted into synthesis gas that contains hydrogen and carbon monoxide. The steam reforming process works by reacting high temperature steam with a hydrocarbon. Natural gas is commonly used as the feedstock for the production of hydrogen but fossil fuels, such as naphtha, liquid gas, or refinery off-gas, can also be used.
Natural gas steam reforming, also known as steam methane reforming (SMR) is the most prevalent process for hydrogen generation. Natural gas contains methane, which, in the presence of a catalyst, reacts with steam that has been heated to 700°C – 1,000°C to produce synthesis gas (predominantly comprised of hydrogen and carbon monoxide). These reactions take place in what are aptly referred to as steam reformers.
A steam reformer is made up of several sections that house the different reactions. The process begins in a furnace where the feedstock is mixed with high temperature steam. The steam and natural gas mixture then moves into heated reformer tubes that contain a catalyst.
The first reaction occurs as the mixture flows through the reformer tubes. In this stage of the process, methane and steam react to produce hydrogen and carbon monoxide.
The next stage in the process is the water-gas shift reaction. Here, the carbon monoxide produced in the first stage and steam are reacted with a catalyst which creates additional hydrogen and carbon dioxide.
The final stage occurs in the pressure swing adsorber. This is where any last bits of carbon dioxide and methane are removed from the process to produce clean hydrogen.
As previously mentioned, reformer tubes are the components of steam reformers where the initial reactions take place between the steam and hydrocarbons. A typical reformer can contain 200 to 400 vertically hanging tubes that are heated externally by gas burners.
The service life of reformer tubes tends to be very limited. This is most often due to the intense stresses that reformers are put through as a part of their day to day operation. They undergo alternating thermal and mechanical stresses, carburization, and oxidation, both on the inside and outside. Reformer tubes also tend to be particularly vulnerable to creep, which can also lower their life expectancy.
Is this definition incomplete? You can help by contributing to it.
|
November/December 2014 Inspectioneering Journal
By Kelsey Hevner at Quest Integrity Group
Steam reformers are critical assets for the successful operation of hydrogen, ammonia, and methanol plants. The steam reformer is also one of the most expensive assets in these facilities. Catalyst tubes inside the reformer are one of the most important and costly components. |
|
March/April 2013 Inspectioneering Journal
By Thomas Fortinberry at Quest Integrity Group, and James R. Widrig at Quest Integrity
Steam reformers are critical assets to many refining and chemical manufacturing plants and facilities, and it is well known that the reformer is one of the most challenging assets to maintain and operate. Common problems in reformer operations include burner firing, flue gas distribution, and catalyst damage. |
|
May/June 2005 Inspectioneering Journal
By John Reynolds at Intertek
Carbon dioxide (CO2) corrosion is most typically found in boiler condensate return systems that are not adequately treated with corrosion inhibitors (typically amines). Dissolved CO2 in condensate forms carbonic acid (H2CO3) which corrodes steels and low alloys to form a iron carbonate scale. |
|
May/June 1997 Inspectioneering Journal
By John Brear at ERA Technology Ltd., John Williamson at ERA Technology Ltd., and Bobby Wright, P.E. at Stress Engineering Services
Reformer catalyst tubes are commonly manufactured from high strength, creep and corrosion resistant alloys. They are relatively thick walled and are usually produced by centrifugal casting. Their lives are limited by creep, driven by a combination of internal pressure and through-wall thermal stresses generated by operational transients. The typical composition for alloys for reforming service is 25/20 Cr/Ni with the generic reference HK40. |
