The UK’s University of Bradford researchers are proposing a method for increasing the yield of the middle distillates, gasoline, jet fuel, and diesel fuel at the refinery by applying catalytic hydrotreating (HDT) to raw crude oil. Current technology uses HDT on the fuels after they’re drawn from the crude by distillation, the process of heating the crude so the various products “boil off”. The result from the study shows that there’s a net product increase to hydro treat the crude prior to the distillation.
UK Bradford Block Diagram Process Comparison.
A caution comes up right away. Not all crude oils are the same. The researchers used Iraqi crude oil as the test subject. The research is showing that the crude residue, the non-fuel portion remaining after the fuel segment is drawn off to be less, meaning a higher portion of the crude went to fuel product. It looks worth pursuing.
Today there is increasing demand for high-quality middle distillates worldwide. At the same time the demand for low-value oil products, such as heavy oils and residues, is decreasing. That makes maximizing the production of more liquid distillate fuels of very high quality very important to refiners and consumers.
But hydro treating crude oil is one of the most challenging tasks in the petroleum refining industry, nor are crude treatment efforts reported widely in the literature stacking up ideas on how to extend the crude oil supply.
HDT is a process that uses hydrogen at high reaction temperatures and pressures, along with a high-activity hydrotreating catalyst. The compounds (the large long molecules) that have high molecular weight in the crude oil feedstock will be cracked apart and saturated with H2 to yield distillate fractions with increased hydrogen/carbon (H/C) ratio and decreased impurities. In simple terms, HDT increases the quality and quantity of the distillate fractions. Using hydrotreating processes on the separated oil fractions as is now common in refining is fairly easy.
But at the raw crude level there are other not so friendly things. Crude oil contains several compounds and complex structures including multiple phases and the presence of the asphaltenes (Asphalt) containing a varying and sometimes large amount of sulfur and metals. Those elements can close the active sites of the catalyst shutting down the process.
UK Bradford Crude Hydrotreating Result.
For the new research the team used multiple reactions carried out in a continuous flow isothermal trickle-bed reactor using the Iraqi crude oil as a feedstock and commercial cobalt-molybdenum on alumina (Co-Mo/?-Al2O3) as a catalyst for a range of reactor temperatures, hydrogen pressures, and liquid hourly space velocities, with a constant hydrogen to oil ratio. The crude oil hydrotreated at the best operating conditions was then distilled into light naphtha (LN), heavy naphtha (HN), heavy kerosene (HK), light gas oil (LGO), and reduced crude residue (RCR) to compare the yield and properties of these derivatives to the same fractions produced by conventional methods.
The team is attributing the yield fractions percent of increase due to their method of converting of heavy compounds and long molecules that are concentrated in heavy fractions (such as RCR) to light compounds as a result of the hydrotreating of crude oil before the distillation process. When conventional processes are carried out for each fraction separately, the heavy compounds and long molecules are deposited at the bottom of the atmospheric and vacuum distillation column. The team notes hydrotreating those using normal operations and conditions is difficult.
Refining crude oil is an ever-changing job of processing various crude oils to achieve the market demands for the various fuels with the desired properties. An increase in middle distillate quantities can improve the refinery economics substantially as a result of transportation fuel demand. The University of Bradford researchers can show HDT has the ability to increase the yield of distillate fractions and simultaneously reduce the contents of impurities improving the overall refinery gain.
It looks like the graphic shows there might be from 1% to 3% more gain, which is no small number when applied across the whole crude oil run per day in the industry.
It looks like a little, but every little bit helps. Successfully developed and adopted widely the research could be worth more than a million barrels a day worth of crude oil. Doesn’t sound so little anymore.
By. Brian Westenhaus
Source: More Fuel from Less Oil