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Why is this process becoming an even greater necessity in the petroleum refining industry? One reason is that there is a greater demand for high-quality low-sulfur fuel products. This demand is much the result of a greater understanding of the harmful effects on the environment of burning sulfur. As a result, environmental regulations have increased the restrictions on the amount of sulfur content allowed in the fuels sold to market. Also, there is a diminished availability of conventional crude oil. Therefore, there is a tendency to use lower grade feedstocks with higher sulfur content. Hydrotreating is the solution!
Hydrotreaters contribute significantly to high-quality end-products; they also remove contaminants that can damage the refinery processing equipment. If left unchecked, nitrogen, sulfur, oxygen, and metals in petroleum fractions can damage downstream equipment.
Hydrotreaters operate under various operating parameters depending on the feedstock and required quality of the end-product. Pressure, temperature, cycle time, and type of catalyst can all change depending on the application. The strict use of the term hydrotreating is primarily referring to the removal of unwanted impurities. In comparison, hydrocracking is referring more specifically to the process of breaking down complex hydrocarbon molecules into simpler ones. Hydrotreating is used more commonly for lighter feedstocks, such as naphtha. Heavier, low-value oils more commonly require the addition of the intensive hydrocracking process.
Hydrocracking involves three fundamental processes: (1) preliminary desulfurization, (2) feedstock pretreatment for cracking, (3) hydrocracking. While hydrocracking can be considered a hydrotreating process, it is much more demanding. It usually requires a higher temperature, higher pressure, greater hydrogen consumption, and more time spent in the hydrocracker reactor. One of the great products of a hydrocracker is ultra-low sulfur diesel (ULSD), which is growing in popularity!
Didion Vessel can fabricate and manufacture both hydrocrackers and hydrotreaters, covering all of your needs.
The high pressure and temperatures in the presence of hydrogen in a hydrotreating unit require a skilled team of engineers and fabricators to manufacture. Here at Didion Vessel, we have a wealth of knowledge building ASME code pressure vessels using various alloys, including those meeting the latest NACE specifications. We also specialize in clad or weld overlay, a cost-effective way to save your unit from damaging corrosion.
In the hydrotreater process, it is essential to separate the gas from the liquid after the stream leaves the hydrotreater. The hydrogen-rich gasses are recycled and remixed with the feedstock. Also, before you can reuse the hydrogen, it needs to be cleaned of H2S. An amine scrubber accomplishes this. Our company designs and manufactures the custom separators and scrubbers required for this process.
The stream is cooled after leaving the hydrotreater or hydrocracker before entering the separator. Then it is heated back up again before it enters the distillation column. Whether you need to heat up it up or cool it down, Didion Vessel has years of experience designing and fabricating custom, TEMA compliant, and ASME stamped Shell and Tube Heat Exchangers. Didion Vessel also holds the R-Stamp, so we are qualified to make repairs to your existing Heat Exchanger or recertify it with the NBBI.
Hydrotreating for sulfur removal is called hydrodesulfurization (HDS) or hydrodenitrogenation (HDN). Below are the basic steps of this process:
There are a variety of hydrotreating processes, depending on different projects. Many refineries have more than one hydrotreater or hydrocracker unit.
In recent years, the world of hydrotreaters has come to include more than just distillate fuels. It’s also been extended to atmospheric resids. Below is a list of a few types of hydrotreater feeds: