(56a) Cavitation Refining of Junk Oil

The PHCR Process includes pressure, heating, cavitation and reaction.  Inputs include junk oil for enhancement and recovery.  (knickle).  The process involves breaking of bonds.  The input depends upon the junk oil but typically might involve transport ships bottoms.  The bottoms can then be blended with a lighter hydrocarbon such as diesel oil and with water.  Experimental results have indicated this mixture can create an equivalent to number two fuel oil.  The degree of cracking would add an important analysis to this process.

When a chemical reaction occurs, molecular bonds are broken and other bonds are formed to make different molecules. Bonds of two water molecules are broken to form hydrogen and oxygen. 

2H 2 O→2H 2 +O 2  

Bonds do not break and form spontaneously but require an energy change is required. Bond energy is the energy input required to break a bond. The shorter the bond length, the greater the bond energy.

Although each molecule has its own characteristic bond energies, some generalizations are possible. For example, although the exact value of a C–H bond energy depends on the particular molecule, all C–H bonds have a bond energy of roughly the same value because they are all C–H bonds. It takes roughly 100 kcal of energy to break 1 mol of C–H bonds, so we speak of the bond energy of a C–H bond as being about 100 kcal/mol. A C–C bond has an approximate bond energy of 80 kcal/mol, while a C=C has a bond energy of about 145 kcal/mol.

In a chemical reaction the atoms in the reactants rearrange their chemical bonds to make products. The new arrangement of bonds does not have the same total energy as the bonds in the reactants. Therefore, when chemical reactions occur, there will always be an accompanying energy change.

For an endothermic chemical reaction, energy is absorbed as reactants are converted to products. A procedure would be to first look at the molecules determine what bonds exist and then examine the new molecules to determine the bond breakage located in the reactant side. Then we can find the net change of the reaction.  Energy is required to break bonds. For this question simply look at the number you calculated as your enthalpy of reaction. Is it positive or negative? It is positive so this means that it is in fact endothermic. It requires energy in order to create bonds.

Bond Energies

Molecules have different C-C bond energies but usually they are similar and the enthalpy change for breaking bonds is positive. We can calculate a pseudo Ea in the Arrhenius Equation to determine temperature dependence. By knowing bond energy at two different temperatures and using the Arrhenius equation. C-C and H-C and H-O in hydrocarbons are covalent bonds. Covalent bonds share electrons.to form a molecule – covalent bonding. Bond Dissociation Energy (Bond Energy) is the energy need to break one mole of bonds. Bond energy is a measure of the amount of energy needed to break apart one mole of covalently bonded gases. The SI units used to describe bond energy is kiloJoules per mole of bonds (kJ/mol).

Organic Reactions and Cracking

Cracking is the process whereby complex organic molecules such as kerogens or other heavy hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the   breaking of carbon-carbon bonds in the precursors. The rate of cracking and the products are strongly dependent on temperature and presence of catalysts. Cracking is the breakdown of large alkanes into smaller, more useful alkanes and alkenes. Simply put, hydrocarbon cracking is the process of breaking a long-chain of hydrocarbons into short ones.

Bitumen is an oil-based substance. It is a semi-solid hydrocarbon product produced by removing the lighter fractions (such as liquid petroleum gas, petrol and diesel) from heavy crude oil during the refining process.  (Refined bitumen) At ambient temperatures, bitumen is a stable, semi-solid substance.   Bitumen is created according to the requirements of its end use specification. This is achieved either by the refining process or by blending.

Bitumen is too viscous to pump at room temperature. It must be kept hot or blended and heated.
Bitumen can either be cracked or diluted to reduce viscosity. The bitumen can be diluted with light ends such as diesel.(up to 20% diluent). This will be referred to as diluted bitumen.

Cavitation

There are two primary types of cavitation including 1.    Vaporization Cavitation; and
2.    Internal Recirculation Cavitation

According to Bachus, vaporization cavitation accounts for nearly 70 percent of all cavitation cases, with internal recirculation cavitation accounting for 15 percent of cases

In chemistry, a radical (more precisely, a free radical is an atom, molecule, or ion that has unpaired valence electrons. With some exceptions, these unpaired electrons make free radicals highly chemically reactive towards other substances, or even towards themselves: their molecules will often spontaneously dimerize or polymerize if they contact each other. Most radicals are reasonably stable only at very low concentrations in inert media or in a vacuum.

A notable example of a free radical is the hydroxyl radical (HO•), a molecule that has one unpaired electron on the oxygen atom.  In contrast, the hydroxyl ion (HO−) is not a radical, since the unpaired electron is resolved by the addition of an electron.

Creation of free radicals occur in a number of ways, including synthesis with very dilute or rarefied reagents, reactions at very low temperatures, or breakup of larger molecules.  Any process that puts enough energy into the parent molecule can affect a large hydrocarbon molecule.  Input energy can include ionizing radiation, heat, electrical discharges, electrolysis, pump energy and chemical reactions. Indeed, radicals are intermediate stages in many chemical reactions.

Following recent nomenclature revisions, a part of a larger molecule is now called a functional group and "radical" now implies "free". However, the old nomenclature may still occur in the literature.

A familiar free-radical reaction is combustion. Combustion consists of various radical chain reactions that the singlet radical can initiate. The flammability of a given material strongly depends on the concentration of free radicals that must be obtained before initiation and propagation reactions dominate leading to combustion of the material. Once the combustible material is consumed, termination reactions again dominate and the flame dies out. When a hydrocarbon is burned, a large number of different oxygen radicals are involved.

The dimensionless Cavitation number (Ca) is used to characterize the relationship between the difference of a local absolute pressure from the vapor pressure and the kinetic energy per volume, and is used to characterize the potential of the flow to cavitate.

Where

1.     is the density of the fluid.

2.     is the local pressure.

3.     is the vapor pressure of the fluid.

4.     is a characteristic velocity of the flow.

Experimental Analysis

Analysis of beginning and final samples of the process can be made by application of GC-VUV technology, vacuum ultraviolet (VUV) detector for gas chromatography (GC).  The percentage cracking of the process can then be obtained.

References

1.      Knickle, H. et al “Innovative Hydrocavitation Technology Process to Create Composite Fuels” AIChE Spring Meeting, Session 141, Houston TX (2012)

2.      Petrucci, Ralph H., Harwood, William S., Herring, F. G., and Madura Jeffrey D. General Chemistry: Principles and Modern Applications. 9th ed. Upper Saddle River: Pearson Education, Inc., 2007.

3.        Carruth, Gorton, Ehrlich, Eugene. "Bond Energies." Volume Library. Ed. Carruth, Gorton. Vol 1. Tennessee: Southwestern, 2002."Bond Lengths and Energies."

4.        UWaterloo, Nov 2010. http://www.science.uwaterloo.ca/~cch...20/bondel.html

5.      Anal. Chem., 2014, 86 (16), pp 8329–8335, DOI: 10.1021/ac5018343, July 31, 2014