Vacuum Distillation and the Use of the Watson Characterization Factor

Posted on June 15, 2014 by Kenton John Klobusnik

Vacuum distillation is needed when the temperatures required for atmospheric distillation of the heavier crude oils are so high that thermal coking would be possible. Thermal coking in a distillation column has the negative effects of loss of product, plugging of the furnace pipes with coke, and other equipment damage. In order to prevent this problem, the mixture is distilled under a vacuum since the boiling point temperature decreases with the decrease of the pressure in the process. The absolute pressure in the column is set from 25 to 40 mmHg. In order to increase vaporization, steam is added to lower the pressure to less than 10 mmHg. Steam addition also benefits the process by increasing the tube velocity in the furnace, which minimizes the formation of coke and also decreases the partial pressure of the mixture in the column. In order to minimize the pressure difference between the top and bottom of the column, packing is added to increase the contact between the liquid and vapor so that more fractionation occurs.

The Watson Characterization factor (Kw) can be used to determine whether vacuum distillation is needed and at what temperatures it should be implemented at in order to control thermal coking in the process. Kw is calculated using the physical properties of the crude oil. This factor could determine the temperatures for which above them a significant amount of coking production would occur. The Watson Characterization factor also can determine if the mixture is paraffinic, naphthenic, or aromatic, which also gives insight into what temperatures will need to be used. This allows the operators to know what temperatures they need the run the column at to prevent harmful thermal coking.

References

1.) Gary, James H., Handwerk, Glenn E., Kaiser, Mark J. Petroleum Refining Technology and Economics. Taylor and Francis Group. Florida. 2007. Print.

Distillation Methods Used for Oil Refineries

Posted on June 15, 2014 by Kenton John Klobusnik

The three common distillation methods that are tested than can be implemented at an oil refinery are True Boiling Point Distillation (TBP), ASTM Distillation (ASTM), and Equilibrium Flash Vaporization (EFV). They all have their advantages and disadvantages and specific uses at the oil refinery. True Boiling Point Distillation uses a batch distillation operation that uses more than 100 theoretical plates and a high reflux ratio of 100. These conditions are used mainly for crude oils and not petroleum products, and the distillation conditions allow for the lower boiling component to be distilled off without any contamination of the other components in the mixture. ASTM distillation also uses a batch process but does not include any theoretical plates or reflux in the operation. However there still might be some unavoidable reflux due to condensation of the vapor on the sides of the distillation column. This still allows for the different components in the column to be separated based upon their boiling points. This method is used for refinery products and property calculations and correlations for distillate fractions. The last method used is that of Equilibrium Flash Vaporization in which a flash drum is used to separate the liquid and vapor components of a mixture that is being heated while the mixture is at equilibrium. This used for obtaining data for flashing operations in the refinery. TBP distillation achieves the highest degree of separation of the mixture due to the plates and reflux being used. ASTM distillation does not have as good of separation that TBP distillation does, but it is better than EFV. Therefore depending on what information you need to obtain, you can choose the necessary method.

Petroleum Refining in the United States and its Economical and Environmental Concerns

Posted on May 25, 2014 by Kenton John Klobusnik

Ever since the first oil well was drilled in 1859, there has been an increased demand in petroleum in the United States.¹ This is because petroleum was found to have many different uses since it could have different properties depending on what temperatures the petroleum was distilled at. In order to do this process, oil refineries were built in order to get useful products while removing the harmful side products of the process. The first refinery in the United States was opened in 1861.¹ This shows that people saw the importance of processing the petroleum and moved quickly to build a refinery to do so. With the invention of the internal combustion engine the demand for gasoline has grown dramatically over the years.

In 2013 the United States had a total oil production of 12.316 million barrels.² Even though this is a large amount that was produced, it was still less than the consumption of 18.49 million barrels in 2013.² Therefore the United States needed to import oil in order to meet this demand. Data from 2012 shows that approximately 40% of the petroleum consumed was from exports.³ Surprisingly a little over 50% of the imports came from the Western Hemisphere with Canada being the largest crude oil supplier to the United States.³ This shows that there is less of a demand in the political unrest in the Middle Eastern region. Since 2005 the demand for imported oil has declined. After the recession in 2008 the consumption of oil was lesser and there was a focus on increasing the efficiency as well as the increase in the use of biofuels such as ethanol and biodiesel.³ The discovery of the Marcellus and Utica Shale formations in Pennsylvania has led to the finding of tight oil that adds to the total oil reserves in the United States, which makes it possible for the United States to import less.⁶

In 2012 37% of energy in the United States came from the consumption of petroleum.⁴ Even though renewable fuels and natural gas are having a greater impact, petroleum is still the largest energy source. This means that oil refineries have a large job to fulfill. The refineries have the capacity to process large amounts of crude oil, but also must take into consideration the environmental impact that the refineries have. Refineries consume a large amount themselves as they are distilling the crude oil to form the final products. There are restrictions on the CO₂ emissions as well as on the hazardous byproducts of the process. When petroleum products are burned in an internal combustion engine several harmful products are created. These include carbon dioxide, which is a greenhouse gas, carbon monoxide, sulfur dioxide, which contributes to acid rain, nitrogen oxides, volatile organic compounds, and particulate matter.⁵ All of these negatively impact the environment and human health. Therefore the government strictly enforcing regulations on refineries and how they process the crude oil in order to limit the harmful byproducts. It does not mean there will be a large decrease in the consumption of petroleum fuels in internal combustion engines, but that refineries will be forces to formulate the fuels in a way that limit the environmental and health concerns.

References

1.) Gary, James H., Handwerk, Glenn E., Kaiser, Mark J. Petroleum Refining Technology and Economics. Taylor and Francis Group. Florida. 2007. Print.

2.) http://www.eia.gov/countries/country-data.cfm?fips=US

3.) http://www.eia.gov/energy_in_brief/article/foreign_oil_dependence.cfm

4.) http://www.eia.gov/forecasts/aeo/er/early_fuel.cfm

5.) http://www.eia.gov/energyexplained/index.cfm?page=oil_environment

6.) http://www.eia.gov/tools/faqs/faq.cfm?id=847&t=6