Blog Post 10: 

Discuss how the Second World War affected the development of petroleum refinery processes.

Evolution of a refinery is based on the demand in which the consumers have for the products. When the automobile industry came about it sparked a huge demand for gasoline and other lubricants which in turn made the industry grow. This extreme growth in demand lead to the creation of the thermal refinery. In the Second World War just using heat within a refinery was not enough to meet the demand for high performance fuels. Even with the rapid introduction of various thermal cracking processes, only 20% of the gasoline produced in the U.S. came from thermal processes. The catalytic refinery was then brought about which continued after the war.

The Catalytic Refinery arrived at a very important time for the making of high performance gasoline and other petroleum fuels in the period leading to and during the World War II. Developing catalytic processes had completely re-worked the chemistry of petroleum refining.  World War II was the backbone for urgently developing catalytic technologies. A catalytic refinery closely resembles the refineries today with a focus on making high yields of gasoline.  Through catalytic processes with the introduction of hydrotreating, catalytic cracking, reforming, alkylation, and polymerization the way of making high octane number gasoline has been built.

A catalytic refinery incorporated new thermal and separation processes such as delayed coking, visbreaking, and deasphalting.  The catalytic refinery produced large quantities of LPG and witnessed the increasing demand for kerosene jet fuel. During World War II there was a major increase for the development of refining processes.  The concerns for environmental pollution by the combustion of petroleum fuels, however, has brought emphasis on more effective finishing processes.  Because of this the modern refineries focus more on processing the heavy ends of petroleum and making cleaner fuels.

Blog Post 9

Post your response to the blog discussing why refinery wastewater cannot be treated in municipal wastewater treatment plants.

Water and steam are used for treatment in huge quantities in petroleum refining. Of course a refinery thus generates a lot of waste water. The waste water faces many different levels of contamination based upon its usage within the refinery. The steam or water that comes into direct contact with the hydrocarbons or crude oil is the most highly contaminated and should be treated separately on its own. In order to have the best and most efficient water treatment process the key is segregation of the waste streams. This is because of the different forms of contamination. For example, desalting you don’t really need to use fresh water, you can use waste water that is contaminated with hydrocarbons but doesn’t contain salt to remove salt from crude oil as the very first process before undergoing distillation. Process water contaminated with hydrocarbons can be used effectively for desalting instead of fresh water. Different wastewater streams have different levels and different kinds of contaminants.  Combining them would increase the load on wastewater treatment facilities.

The units within a refinery that generate the largest amount of wastewater are desalting, distillation, cracking processes, coking, heat exchangers, and storage tanks The four types of refinery wastewater include cooling water, process water and steam, storm water, and sanitary sewage water. Storm water may be contaminated because of incidental exposure to pollutant sources on refinery surfaces and other accidental spills such as oil from automobiles.  Pollutants found in the wastewater streams include hydrocarbons that have a particular concern for toxic aromatic compounds, heteroatom compounds, dissolved gases, acids, and suspended or dissolved solids.  Cooling water and sanitary sewage water are forms that may not require much treatment before they are sent to public water treatment facilities due to their contamination levels. The most important thing to keep in mind is to avoid mixing different types of wastewater streams to reduce the load on the treatment units.

Blog 8

Write a blog post discussing the objectives of catalytic reforming and limits on catalytic reforming capacity in the U.S. refineries.

Alkylation, polymerization, catalytic reforming, and isomerization are all catalytic conversion processes performed to produce a high octane number gasoline. This is essential for obtaining high performance and high power. Catalytic reforming developed during the Second World War with a feed stock coming from the Light Ends Unit. The heaviest product of this, the heavy naphtha is used. This is heavy because it has a lot of naphthenes or cycloalkanes in its composition. Catalytic reforming’s objective is to convert these naphthenes or cycloalkanes into aromatics with very high octane numbers. Dehydrogenation of naphthenes using precious metal catalysts is straight forward for a clean heavy naphtha feedstock. However, if sulfur is associated it must have pre hydro treatment to avoid poisoning from occurring with platinum.

After the crude has been distilled and the heavy naphtha has been obtained and treated, if necessary, it is separated in a naphtha fractionator. The light naphtha will be withdrawn and sent to the gasoline pool while the true heavy naphtha will go through a catalytic reformer which will then produce the high octane number reformate and a byproduct of hydrogen gas.  The most important reactions of interest within this process are converting naphthenes to aromatics and the isomerization of n-paraffins to i-paraffins. Reforming a heavy naphtha that contains a higher n-paraffin content requires more severe conditions within the reactor. The desired catalytic reforming reactions within catalytic reforming are dehydrogenation, dehydroisomerization, dehydrocyclization, and isomerization. High temperature, low hydrogen pressure, low space velocity, and a low H2/HC ratio all strongly promote the occurrence of these chemical reactions.

Up until the 1990s catalytic reforming was one of the most popular processes in the refinery for producing high number gasoline. With the introduction of the Clean Air Act amendments the amount of benzene aromatics became limited. This made catalytic reforming undesirable. However, the valuable byproduct of hydrogen gas has become very essential since it is needed in the hydro treating and hydro cracking processes. This being said, catalytic reforming became the cheapest way of obtaining hydrogen.

Blog 7

Write a blog post comparing catalytic cracking and catalytic hydrocracking processes with respect to feedstocks, process objectives, and products.

After all of the various physical separations have occurred to a crude oil, such as distillation, deasphalting, and dewaxing, there is a need to now change the composition of the crude oil using chemistry, breaking and creating bonds. The yields of this product after just undergoing the physical changes does not meet the demand required so further chemical separations must be pursued. The earliest discovered method for chemical separation is known as thermal cracking which uses brutal heat, heating the temperatures until the compounds crack and the chemical bonds are broken.

However the thermal cracking processes could not meet the demand for quality. This process delivered gasoline with a low octane number which was only acceptable for automobiles back in the day. Engines now have higher compression ratios and require a higher octane number in gasoline. They need a gasoline that does not ignite spontaneously with pressure when pressurized with air. This lead to the introduction of catalytic cracking.

Most catalytic conversion processes were developed right before and during Second World War for making higher quantities of better fuels with higher octane numbers. In catalytic cracking the reactive species are carbo cations that are produced on catalyst surfaces. Carbo cations go through isomerization reactions very quickly providing the opportunity to create isoparrafins. Almost all gasoline production in the U.S. is done through catalytic means.

There are a few different forms of catalytic cracking such as Houdry catalytic cracking, Thermafor catalytic cracking (TCC), and fluid catalytic cracking (FCC), however they are not all equally efficient. Fluid catalytic cracking is the most popular process and is the heart of the refinery. Catalytic cracking had a very flexible range of feedstocks that can be used from the gas oil boiling range all the way up to light vacuum gas oil. Cracking products after being fractionated can be separated into products such as gas, gasoline, light cycle oil (LCO) and heavy cycle oil (HCO).

For heavier aromatic feedstock materials such as heavy vacuum gas oil or vacuum distillation residue hydrogen must be introduced so that we can convert these heavy fractions without rejecting large quantities of Carbon. This is known as hydro cracking, which has the principal objective of upgrading products by decreasing the molecular weight and boiling point of heavy oils to produce products of saturated hydrocarbons, such as diesel and jet fuel. The hydrocracking process has two dimensions: Hydrogenation of aromatic rings and cracking of aliphatic compounds. Hydrocracking provides high yields of valuable distillates without producing low-grade byproducts such as heavy oils, gas, or coke, as experienced in carbon rejection processes such as coking. This method is less flexible with its feedstock range and also more costly than catalytic cracking.

Blog 6

Write a post reviewing the significance of thermal cracking in petroleum refining in the past and present.

After all of the various physical separations have occurred to a crude oil, such as distillation, deasphalting, and dewaxing, there is a need to now change the composition of the crude oil using chemistry, breaking and creating bonds. The yields of this product after just undergoing the physical changes does not meet the demand required so further chemical separations must be pursued. The earliest discovered method for chemical separation is known as thermal cracking where the chemical bonds are broken through changing temperature.

In the past the large demand for gasoline as a product from crude oil started with the mass produced model T automobile back in the 1920’s. Thermal cracking was the first chemical process introduced to convert heavier hydrocarbons with longer chain paraffins to lighter distillates. Thermal cracking produces shorter straight chain alkanes from longer straight chains. This was the number one method used to obtain gasoline from crude oil back in the day. It does so by using brutal heat, heating the temperatures until the compounds crack and the chemical bonds are broken. This process then delivered the gasoline, with a low octane rating, needed for automobiles at that time.

Thermal cracking proceeds through neutral reactor species called free radicals.  Another use for thermal cracking is to convert the bottom of the barrel into usable products such as fuel oils. Presently thermal cracking is not a significant process in a refinery within the United States because the gasoline that is produced from it would work properly in current automobiles. This is because the current automobiles require a fuel with a higher octane rating. This lead to the introduction of catalytic cracking.

Blog 4

Write a post explaining how solvent fractionation works and review the parameters to describe the solvent power for non-polar solvents.

Through the process of deasphalting, a solvent is used to fractionate various feedstocks. Deasphalting performs its fractionations based upon the components of solubility and insolubility of feedstocks where distillation uses the boiling point temperatures to make fractionations. Vacuum distillation residue, known as VDR, is completely dissolved in aromatic solvents such as toluene and benzene.  VDR is typically in the form of a solid at room temperature so then the aromatic solvents are used to create a liquid mixture where a light paraffin solvent is mixed with the feedstock mixture to precipitate the VDR asphaltene. Depending upon solubility the asphaltene is then separated from the mixture.The VDR component that is soluble in this light paraffin is referred to as a maltene and is considered a one phase material solution. Through the gradient solubility model it is explained that asphaltene molecules can dissolve and give a single phase solution. Through solvent extraction and VDR the asphaltene can be removed from the solution.

The VDR compounds solubility, which effects the extraction, depends on the strength of the solvent which is measured for non-polar solvents by the Hildebrand Solubility Parameters, also known as HSP. There are two different Hildebrand solubility parameters that affect this solubility. The first parameter measures the relationship between surface tension and the cube root of molar volume. These happen to have an inverse relationship where surface tension increases with decreasing molar volume. Solubility also increases with surface tension. The second parameter measures solubility based upon the relationship between the heat energy required for vaporization and the molar volume. This is typically calculated under constant volume. Solubility increases in this case with an increase in the amount of energy for vaporization.

Blog 5

Write a post comparing the solvent dewaxing and catalytic dewaxing processes.

Dewaxing is a process used to remove waxes from oil refinery feed stocks. Once the wax is removed it can be sold as a bi-product for things such as candles and other forms of waxes. The feedstock after being dewaxed can be used as various lubricating oils and other distillate fuels such as gasoline. Dewaxing is performed on a feedstock through two different processes. One is a physical process that uses a solvent and is known as solvent dewaxing. The other is a chemical process and uses catalytic cracking and is known as catalytic dewaxing.

In solvent dewaxing a solvent is added to the feedstock and the mixture is then chilled to a desirable temperature and then proceeds through a rotary filter which separates the solid wax from the feedstock. This is because of the components varying freezing temperatures which allows for seperation to occur. Solvent dewaxing primarily uses two types of solvents being propane and methyl ethyl ketone, also known as MEK. MEK is more commonly used as a solvent due to its minor variance in filtration and pour point temperatures along with its chilling rate characteristics.

Catalytic dewaxing involves the breaking and creation of bonds. It is known as a conversion process of n-paraffins.  This form of dewaxing is able to break apart and actually remove long chain n-paraffins. Catalytic dewaxing uses sieve catalysts to filter with a pore opening size very small so that i-paraffins can be captured and filtered out and only n-paraffins shall be able to pass through. This can also help to lower the feedstock’s pour point value.  Catalytic dewaxing will produce a lube base stock with a lower pour point and a higher yield than that of a feedstock that underwent solvent dewaxing. Catalytic dewaxing is a less expensive form of dewaxing, but both processes have their pros and cons.

Write a post explaining the need for vacuum distillation and discuss the utility of Watson Characterization for selecting the vacuum distillation temperature.

Vacuum distillation is essential in petroleum refining. Through this method the distillates can be separated into light vacuum oils, heavy vacuum oils, and vacuum residue. The lighter components of the crude can then be removed out of the top of the distillation column so that the heavier non-volatile compounds remain on the bottom. A vacuum is needed for this method in order have properly met temperatures and pressures within the distillation column. It also is needed in order to avoid thermal cracking.

The heaviest and most contaminated portion of the crude oil is known as the vacuum distillation residue, found on the very bottom. This residue is actually able to be upgraded into a usable fuel source through various processes such as deasphalting, visbreaking, and coking. Deasphalting requires hydrotreating whereas both visbreaking and coking require thermal cracking with coking being more severe.

In catastrophic instances a distillation unit is shut down. This puts a refinery in a very bad position. Very major coking cases can actually block the path of flow in a distillation column and force it to be shut down. Because of this reason it is very important to select the proper temperature in a vacuum distillation column. Doing so will control the risk of coking within the column. The Watson Factor, known as Kw, is used to estimate the upper temperature limit for vacuum distillation to avoid coking and ensure that the process within the distillation column occurs smoothly without any clogging. This is essential to keep a refinery up and running and not have to stop for maintenance.

Write a blog post that reviews the utility of different distillation methods and their applications in petroleum refining.

There are three common different distillation methods. These methods are very important because they allow us the opportunity to obtain a better perspective of crude oil. Using these methods crude oil can be distilled into different oils which have varying characteristics. Each method is a different level of separation. These three methods are:

True Boiling Point Distillation (TBP): In this batch distillation method only one distillation occurs based upon boiling point. This method allows for the most efficient separation. It uses a large number of stages for liquid to vapor contact in the distillation column with a very high reflux ratio while raising the temperature. When a certain boiling point is hit that only applies to a specific portion of the crude, that specific portion will begin to evaporate. Once the portion of the crude with this boiling point changes phases through vaporization it can then be extracted, thus in total now having two different oils. This form of distillation has no standard test methods.

ASTM Distillation: This method is also a batch operation but it does not use contact plates and has a reflux ratio of zero. This method uses a heater and cooling water and instead of distilling after hitting one certain temperature it gradually distills over time. It has much more of an exponential distillation curve for a binary mixture where for TBP distillation it was completely linear with one jump in the graph. This is the standard test method used for refinery products to determine property calculations and correlations.

Equilibrium Flash Vaporization (EFV): This distillation method uses a heater to heat up the liquid and then a flash drum to separate the liquid and vapor phases. This provides data that is useful for determining proper flashing operations in a refinery. By looking at the distillation curve for this method it can be noted that this gives the lowest degree of separation.

The boiling point reached for separation to occur decreases from TBP to ASTM to EFV. The degree of separation also decreases for the same order. Each distillation method is very important and has its own application in petroleum refining.