Three types of distillation methods and their applications in refining

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Three distillation methods that introduced in lesson 4 are True Boiling Point Distillation (TBP), ASTM Distillation (ASTM) and Equilibrium Flash Vaporization (EFV). Since the method of each distillation is different, each of them has their own utility, application in refining and separation performance.

The best possible separation is achieved in True Boiling Point Distillation (TBP). True Boiling Point Distillation (TBP) used more than 100 theoretical plates and a high reflux ratio (R/P) of 100 in the separation process. Since it has such outcome, it is usually used to characterize crude oils and constitute a significant component of crude essay.

Compare to True Boiling Point Distillation (TBP), ASTM distillation (ASTM) also used batch operation. However, the operation incorporates exclude contact plate and a reflux ration of 0. A slight reflux may involve due to the condensation of vapor on the tube. In petroleum refining, the method is used to refine products, calculate properties and correlate distill fractions.

Equilibrium Flash Vaporization (EFV) probably provides the lowest degree of separation among the three distillation methods. It contains a heater to heat a flowing feed. In the flash drum, the separation of liquid and vapor take place. In refinery, Equilibrium Flash Vaporization (EFV) always provides clear and useful data for flashing operation for us to interpret.

Vacuum Distillation and Finding It’s Ideal Temperature

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Before the crude can enter the vacuum distillation unit (VDU), it must first be introduced into the Crude Distillation Unit (CDU) flash zone in order to be separated into vapor and liquid streams. Separation of light and heavy crudes is achieved through Atmospheric Distillation (CDU). Vapor fractions rise to the top of the column while the liquid fraction can be sent to VDU after it is introduced to stripping by steam, in order to recover the components dissolved in the heavier liquid that has settled at the bottom of the CDU. This vacuum chamber is vital since there must be a pressure drop which ultimately results in a decrease in temperature. High temperatures are unwanted since this would bring about cracking and inevitably coking on the column’s metal surfaces, interfering with fractionation.

To control the risk of coking, the ideal vacuum distillation temperature in the vacuum distillation column can be found using the Watson Characterization Factor (Kw). This will calculate the upper bound temperature limit for vacuum distillation to avoid coking. Below this range of temperatures, coking risk would be considered negligible while the upper bound represents uncertainty of the probability of coking. To be sure, the distillation temperature would be set lower than this temperature band. One should also take into account the hydrocarbon composition of the crude as paraffinic crudes are more susceptible to coking.

Distillation Methods Utilized by Oil Refineries

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There are three different distillation methods that are used in crude oil refineries, and those are True Boiling Point Distillation (TBP), ASTM Distillation (ASTM), and Equilibrium Flash Vaporization (EFV). Each of these processes vary in the way distillation is achieved, so some methods are more effective than others.

True Boiling Point Distillation (TBP) is the most ideal process. It is a batch distillation operation which utilizes over 100 theoretical plates and a high reflux ratio of 100. This high number of plates along with a high reflux ratio allows for the best possible separation in distillation processes. These parameters also yield a pure compound since the temperature remains constant during evaporation of the unwanted compound.

The next method is ASTM Distillation. This process also uses a batch operation, but it does not include contact plates and it therefore has a reflux ratio of 0. Reflux inside the fractionation column flows downwards and cools vapors flowing upwards. The more reflux provided for a given number of plates results in more effective distillation, which is why this process is not as good as TBP.

The third distillation method is Equilibrium Flash Vaporization (EFV). This method is known yield the lowest degree of separation out of the three. EFV involves separation of the liquid and vapor in a flash drum after heating the flowing feedstock.

Temperature Effects on Vacuum Distillation and Watson K Factors

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Vacuum Distillation Units process the fuel’s heavy distillates after settling on the bottom of the Atmospheric Distillation Unit and not vaporizing like the lighter fractions. Atmospheric Distillation is used for separation of light and heavy crudes. The heavy distillates require a vacuum because of how temperature and pressure affect molecules. Creating a vacuum chamber will greatly lower the pressure and uses Ideal Gas Law, one can use the correlation with a pressure drop then the required temperature will drop as well. This is desired because high temperatures will cause vibrations and allow for thermal cracking or destruction of bonds within a given molecule carbon chain.  Cracking the molecules would lead to coking on the metal surface of the distillation column and interfere with fractionation in distillation.

The Watson Characterization Factor gives refineries an idea of the range of temperatures for vacuum distillation to help avoid coking. A graph is comprised of temperature vs. Watson K factor and a band is used for plotting this range on the graph. In most cases, the refineries will operate below the lower end temperature to avoid as much accumulation of carbonaceous material as possible.  Higher K factors are at lower temperatures (paraffins), which makes sense because paraffins are easily cracked. In comparison to aromatics, such as benzene, which are stabilized molecules and require higher temperatures to dissociate the molecules bonds.

Petroleum Refinery’s Utilization of Distillation Methods

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There are multiple distillation methods used in the industrial processes of refining crude oil. Three notable processes of distillation are True Boiling Point, ASTM Distillation, and Equilibrium Flash Vaporization. The best process in petroleum refining for distillation is determined by three factors, the number of plates, the reflux ratio, and the steam-to-feed ratio. These parameters are what dictates why the order of the distillation methods previously mentioned are in descending order of best separation methods.

True Boiling point Distillation (TBP) uses a distillation operation that utilizes more than 100 theoretical plates and a high reflux ratio. This is used in petroleum refining not only as the idealized method for best possible separation in distillation but also is used to characterize crude oils and create a significant component of crude essay.

ASTM Distillation is not as good of a separation method as TBP but is usually used for refinery products and property calculations and correlations for distillate fractions. This method does not operate in the presence of contacts plates and has a reflux ratio of 0. This method works in contrast with the TBP Distillation method.

Equilibrium Flash Vaporization has a heater that heats a flowing feed.  The heated feed then is deposited into a flash drum and involves the separation of the liquid and vapor. Equilibrium Flash Vaporization is useful for obtaining data for flashing operations within a refinery.

Supply of petroleum fuels by Russell Hedrick

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Oil production in the United States is a very important industry. The demand for oil for power production as well as transportation is a driving factor for the amount of oil produced. Approximately 50% of all oil production goes towards transportation. In the past few decades oil production has gone through many ups and downs. The fear of a dwindling supply as well as when the oil production will peak has led to many conflicts all over the world. This has been especially true in the area labeled as the Middle East.

Oil production has been increasing greatly over the past few decades. This has been even more prevalent over the last few years. This has been especially true over the past few years in field production in the United States. The annual field production went from 6,783 thousand barrels of oil per day in 2008 to 10,000 thousand barrels of oil per day in 2013. This is very good news from an economic and political stand point but may not be good from an environmental standpoint. This increase in domestic production has led to a decrease in the imports of oil as well as increase in exports. This is a good step in the right direction of becoming a more energy independent country.

In 2008 the United States imported 12,915 thousand of barrels of oil per day. That is almost twice the amount that was produced domestically. Also in 2008 we exported roughly 1,802 thousand of barrels of oil per day. The reason we exported oil, even though we are importing more then we are producing, is because there are other markets around the world where it could be sold at higher prices. The number of imports dramatically changed from 2008 to 2013. In 2013 the United States imported 9,794 thousand barrels of oil per day. That is roughly a 32 percent decrease in total imports per day. Also in 2013 the United States exported roughly 3,594 thousand of barrels of oil per day. This is roughly a 200 percent increase over the number of exports in 2008.

This is a pretty drastic increase in just five years. These increases in field production and exports are due to an increase in oil wells discovered and utilized, although this could have a negative impact on the environment. The more oil wells that are being pump the more potential there is for accidents. This can be seen in the more recent disaster of the BP oil spill in the Gulf of Mexico. This oil spill devastated the region and the effects of it still can be felt today.

The decrease in imports also has a positive environmental impact here in the United States. Imports from the Middle East as well as Mexico are more sour crude, meaning there sulfur content can higher. There sulfur content is roughly 3% more then WTI and LLC sweet crude here in the United States. The higher the sulfur content the more refining and distillation that is required to meet the standards set forth. Less importing of these sour crudes is a good thing for the environment and oil refining here in the United States.

The refining process is crucial for production of gasoline for internal combustion engines. 50 percent of crude oil production goes towards producing gasoline. A steady supply needs to be maintained so there are no surpluses or shortages in the supply chain.

References:
1. http://www.eia.gov/todayinenergy/detail.cfm?id=7110
2. http://www.eia.gov/dnav/pet/pet_sum_snd_d_nus_mbblpd_a_cur.htm

Supply of Petroleum Fuels

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Michael H Bufalini, May 1st, 2014

The US Energy Information Association is the most notable source for our countries energy supply and demand. Using the most recent data of supply and disposition the determination of our major fuel sources and import and export business can be analyzed. The Petroleum and Other Liquids data sheet illustrates the break down how the produced crude oil and petroleum products are used for energy consumption per thousand barrels of distillate liquid.

According to the supply data the US produces approximately 11,000 barrels of crude oil and petroleum products per day while importing 9,240 barrels per day. This data table also involves the net production based on these two values while subtracting the production from renewable fuel sources and oxygenate plant production such as Fuel Ethanol. The production value is 75% crude oil production with the other 25% being natural gas liquids and liquefied refinery gases. The crude oil production is expected to have a higher value because it supplies the majority of the vehicles on the road with our combustible fuel, gasoline. Although not a major contribution, natural gas still holds a high percentage because of the growing use of electricity generation, some use for transportation and in home heating.

The finished petroleum use about 50% of the products for the internal combustion engine in vehicles around the country. Another large percent of the finished petroleum products are used for distillate oils. Approximately 4,800 barrels per day are produced of distillate fuel oils for the use of diesel fuel, domestic heating, and in some cases outdoor portable stoves and heaters.

While we are importing 9,240 barrels a day of crude and petroleum we are also exporting about 40% of that amount of the same products. The majority of the US export business is finished petroleum products in the distillate fuel oil category. This is an expected leader of export because outside of the United States, countries use larger transportation methods and more vehicles run on diesel fuel. The largest distillate fuel export is also 15ppm sulfur content or lower which shows a greater reduction of harmful SOx emissions.  Petroleum Coke is also a high exported fuel source of the finished petroleum products. This is most likely used for a source of fuel for other countries power plants.

The refining process follows regulations with how much a certain fuel needs to be refined for permissible amounts of emissions. Certain fuels need more refining to reduce the carbon, sulfur, and nitrogen emissions. The majority of our distillate fuel oil is refined to be under 15ppm of sulfur and our gasoline is blended with additives such as ethanol and other oxygenates to boost octane and meet air quality requirements. With ethanol being in the fuel it ensures higher percentage of carbon dioxide in the emissions rather than carbon monoxide. Ethanol is being produced by hydrolysis from ethylene, which is manufactured in cracker plants from natural gas liquids.

The Economics of Crude Oil

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Week 1 Blog Post:

Blog 1: Please go to the eia.gov website(link is external) and find the most recent data about the supply of petroleum fuels. Once you have a good understanding of the data, write a blog post to review the most recent supply of petroleum fuels from the data given at eia.gov and comment on how petroleum refining addresses environmental concerns from combustion of petroleum fuels in internal combustion engines. Your post should be 1-2 pages long or between 500-600 words.

 

As our nation’s population increases so does our demand for energy. In the U.S. with petroleum currently being used as the number one source for energy generation, it is in very high demand. The petroleum field is growing which can have both positive and negative effects. It creates jobs and lowers (even though it isn’t doing so much currently) the price of gasoline, which is our nations #1 consumed bi-product of crude oil. The number of barrels produced per day is consistently growing. It is currently at its highest peak since back in October of 1973. Also with a higher production of crude oil we are also increasing our exports which is good for our economy. However, it is not so good in the aspect of its rising price and also harmful emissions and bi-products.

From eia.gov’s most recent spreadsheet of supply and disposition based off of March 2014, the U.S. is currently producing on average 18,526 thousand barrels a day of crude oil and petroleum products. 3,858 of which are exports being almost 21% of our overall produced in the field. There is also 2,378 thousand barrels a day of NGPL’s and LPG’s produced with only 415 (17%) being exports. It should be noticed too however that we are currently importing roughly 50% of what we are producing. In my own opinion, I believe that we should take the money that we are spending on imports and use it to create renewable power plants. Slowly cut it back until our imports hit zero. Purchasing sources of energy from other countries is doing nothing but hurting our nation’s economy by putting us further into debt. We can fully supply our nation’s energy from within our own borders with the technology that has come about.

I did see however, that crude oils have different quality characteristics. Dependent upon where they come from the crude oils have different density (API gravity) and sulfur contents, which range from about 0-3.5%. Density ranges from light to heavy and sulfur content ranges from sweet to sour. Light and sweet crude oils are priced higher than heavy and sour crude oils. This is because both gasoline and diesel fuel, which are two of the primary bi-products, are more easily refined from light and sweet crude. It appears that the best quality crude oil comes from Algeria and Malaysia.  Maybe this explains why we import crude oil, because we are importing a more desirable crude than what we are exporting.

In the internal combustion engines petroleum refining addresses environmental concerns because the more and more it gets refined, the less harmful to the environment it becomes. It contains fewer C-C bonds and becomes easier to break apart or even combust. Because of this, these fuel sources when burned will have a fewer amount of emissions that could possibly harm the environment.

Info from: http://www.eia.gov/dnav/pet/pet_sum_snd_d_nus_mbblpd_m_cur.htm

http://www.eia.gov/todayinenergy/detail.cfm?id=7110

Major Products of a Barrel of Crude Oil and Environmental Concerns Facing Refineries

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According to the EIA.gov website, the total weekly product of oil supplied was used to create seven major products. ~49% of the 18,855 thousand barrels of crude oil supplied on the 16th of May 2014 was used to make motor gasoline. This is by far the most produced product from crude oil. 8% of the supplied crude oil on this day was used to make jet fuel. 20% was used to make diesel fuel.

Crude oil inherently contains toxic compounds which must be removed in the refining process to meet safe standards when burned. Benzene, sulfur, and organometallics are some of these compounds. Because benzene is a carcinogen, only a limited amount can be found in gasoline or fuel oil.  Heavy crude oils can contain organometallic compounds like nickel and vanadium. These are toxic and corrosive in nature and are removed in the refinery. Environmental standards for sulfur requires gasoline, jet fuel, diesel, and fuel oil to be limited in the refinery.

Importance of Environmental Impacts of the Refining Process

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The process of oil refining is a way to improve the overall value of the petroleum. It is done in many ways as alluded to in the lesson. The overall objective is, “to add value to a crude oil feed through production of marketable fuels and materials at the lowest possible cost, in accordance with product specifications and environmental regulations.”

One of the many claims to fame of the process is the production of high-performance fuels for internal combustion engines. The process also addresses the environmental concerns of the emissions produced in the combustion of theses fuels in such engines. This will be the topic of this blog post.

In reading the most recent data provided by the environmental protection agency for the week ending May, 16 2014, the United States crude oil refinery inputs were approximately 15.9 million barrels per day. The refineries operated at 88.7% capacity, with gasoline production coming out to 9.6 million barrels per day. As for the products supplied, the last four week period saw an average of 18.9 million barrels per day. Of the 18.9 million barrels, gasoline products were responsible for 8.9 million barrels. The number of gasoline products supplied is up 5.3% from last this time last year. This type of an increase is a direct correlation of the importance of oil refining for the gasoline provided for internal combustion engines.

The refining process uses many tools to improve on the environmental emissions produced by the gasoline burned in an internal combustion engine. The government has set strict and imperative environmental regulations on the oil these processes produce which causes the importance of improving these stages of utmost importance to oil companies.

During the refining process, the petroleum undergoes many stages to improve the emission contents of such liquid. The separation process separates the physical constituents within the oil, removing wax, solids and other impurities. While the conversion process is more for the purpose of adjusting the chemical composition, the finishing process plays a large role in the environmental improvement as well. It is here that hydro treating takes place with the intent to remove the main culprits of pollution from emissions, and that is the sulfur and nitrogen components of the oil. As we know, these elements are what create NOx and SOx, both of which are strictly controlled in government regulations.

These processes described above will become more and more imperative to be improved as the demand for high performance fuels increases along with the number of cars that are on the road. As the weather gets warmer in these coming months, we can also expect to see a rise in cars on the roads. This increase in travel is only adding to the need that is always prevalent in the oil refining industry. As the US looks to become an exporter of oil rather than its norm of being an importer the need to produce a quality oil becomes even more important with competing markets.

References:

  1. Lesson 1: Introduction to Petroleum Refining and Crude Oil Composition: https://cms.psu.edu/section/content/default.asp?WCI=pgDisplay&WCU=CRSCNT&ENTRY_ID=F20C6357261A4AE2A750C141B721E8C1
  2. This Week in Petrolium: http://www.eia.gov/oog/info/twip/twip.asp
  3. http://www.eia.gov/oog/info/twip/twip_gasoline.html
  4. Weekly Petroleum Status Report Highlights: http://www.eia.gov/petroleum/supply/weekly/