Definitions of Words and Phrases Used in Separation Equipment

Coalescing: The process or mechanism of merging small droplets or aerosols and creating larger droplets that can easily be removed by gravity. It also refers to the joining of liquid droplets dispersed in another immiscible liquid e.g. water drops in oil.

Gas coalescing filter: A separator containing changeable elements that is capable of the removal of sub-micron aerosols and solids. This coalescing and filtering occurs as the gas flows from the inside of the filter/coalescing element to the outside of this element in the vertical filter-coalescer. Properly designed, this coalescing stage will remove solids and fine aerosols down to 0.3 micron and larger. 

Electrostatic coalescer: A device used to remove dispersed water from oil by using a high voltage field to polarize and/or charge dispersed water droplets.

Emulsion: A stable dispersion of one immiscible liquid in another liquid. 

Entrainment: Fluid in the form of a mist, fog, droplets or bubbles carried along with the continuous phase.

Filter: A device used to separate solids from liquid or gas flow. Most filters utilize removable elements. 

Filter separators: A device to remove solids and entrained liquids from a gas stream. It usually has two compartments. The first compartment contains filter coalescing elements. As the gas flows through the elements, the liquid particles coalesce into larger droplets and when the droplets reach sufficient size, the gas flow causes them to flow out of the filter elements into the center core. The particles are then carried into the second compartment of the vessel where the larger droplets are removed. A lower barrel or boot may be used for surge or storage of the removed liquid.

Flash drum: A vessel used to separate liquids, generated due to pressure reduction and/or increase in temperature of a liquid stream, from the gas phase or two phase fluid. 

Gas-oil ratio (GOR): The ratio of gas to hydrocarbon at a defined condition, typically expressed as Sm³/m³. 

Heater-treater: A device used to process hydrocarbon, by warming and coalescence, in order to remove small quantities of residual water so as to meet transportation or product specifications. 

Line drop: A boot or underground vessel, used on a pipeline, to provide a place for free liquids to separate and accumulate. It is used in pipelines with very high gas-to-liquid ratios to remove only free liquid from a gas stream. It will remove bulk liquid, but not necessarily all the liquid. 

Knock out drum: Generic term used to describe vessels for gas-liquid separation. Separation can be either for high, or low, gas-to-liquid ratio streams.

Liquid coalescer: A vessel internal used for increasing the droplet size of immiscible liquids, so that they can be removed by gravity separation. Typical coalescing elements are stacked plates, vanes, wire or plastic mesh, or cartridge type elements. 

Liquid-liquid separators: A vessel where two liquid phases are separated. 

Mist eliminator: A fixed device used to enhance removal of smaller liquid droplets from a gas above which is not normally possible by gravity separation. Typical mist eliminator designs include knitted wire mesh, vane type, and cyclonic.

Production separator: A vessel typically used as the first separation device that the fluid encounters in the wellhead to processing plant production network (sometimes is called Wellhead Separator, when physically located at the well site). 

Retention time: For gas-liquid separation, the average time a flowing fluid remains within the liquid section of a separator at the design feed rate. For three phase separation, the retention time can be the time the total fluid remains in the separation section at the design feed rate, or if defined as phase retention time, the time the phase remains in the separation section. 

Scrubber: A category of separator used for high gas-to-liquid ratios. Scrubbers are used as the primary separator in systems where small amounts of liquid are produced, to ‘polish’ an already-separated gas stream by removing residual contaminants more completely, or as a backup in case of an operational upset upstream.

Separator: A generic term for a device which separates gas-liquid, gas-liquid-liquid, gas–solids, liquid-solids or gas-liquid- solids. 

Slug catcher: A particular separator design which is able to absorb sustained in-flow of large liquid volumes at irregular intervals. Usually found on gas gathering systems or other two-phase pipeline systems at the terminus of the pipeline. A slug catcher may be a single large vessel or a manifolded system of pipes. 

Surge drum: A vessel used to provide appropriate time for flow control and dampening during process variations and upsets. The capacity of the surge drum provides the ability to accept liquids from the upstream process, or provide liquids to down stream equipment without upsets. 

Surge time: The time it takes to fill a specified fraction of a vessel, defined as the volume between a specified level range in a vessel divided by the design feed flow rate. 

Test separator: A separator vessel used near the wellhead, which separates the phases for well test metering. 

Three phase separator: A vessel used to separate gas and two liquids of different densities (e.g. gas, water, and oil) into three distinct streams.

Short Notes #5

Avogadro’s Number

The Avogadro Number is the proportionality factor that relates the number of constituent particles (molecules, atoms or ions) contained in one mole of a substance. Its SI unit is the reciprocal mole, and is exactly 6.02×10²³ mol⁻¹.

Robert Millikan, an American Physicist, was the first to measure the charge on an electron which helped determine the Avogadro’s Number. The electron charge is measured as 1.6021765 x 10^-19 coulombs per electron. The Faraday is the charge on a mole of electrons and is estimated as 96,485.34 coulombs per mole of electron. The Avogadro’s Number is then obtained by dividing the charge on a mole of electrons by the charge on a single electron i.e.,

Avogadro’s Number = (charge on a mole of electrons / charge on a single electron)

                                  = (96,485.34) / 1.6021765 x 10^-19)

                                  = 6.02 x 10²³ particles per mole

Introduction into Chemical Engineering

Chemical Engineering is a field of science that combines chemistry, biology, physics and mathematics to create new technology and create solutions in problems facing current technology.

The American Institute of Chemical Engineers (AIChE) defines chemical engineering as a profession that uses science and mathematics, especially chemistry, biochemistry, applied mathematics and engineering principles, to take laboratory or conceptual ideas and turn them into value added products in a cost effective, safe and cutting-edge process. From the development of smaller, faster computer chips to innovations in recycling, treating diseases, cleaning water and generating energy, the processes and products that chemical engineers have helped create touch every aspect of our lives [1].

Fundamental Topics in Chemical Engineering

These are the most important topics for any chemical engineering study [2]:

Material Balance: It shows how materials move in and out of a system to help us determine how much of the material is required to produce the desired products in addition to the amount of other materials (desired and undesired products) leaving the system. Undesirable products may be byproducts or pollutants

Heat Transfer: This shows how heat is transferred to aid in the designing of apparatus like heat exchangers to produce the heating and cooling of chemical materials to control a desired chemical reaction. This also helps to recover energy resulting from high temperature processes.

Mass Transfer: This describes how molecules move in relation to one another to help design systems to enable mixing and separation of chemical species through processes like:

• Absorption (Gas-Liquid Transfer) – The transfer of a substance from a gas mixture to a liquid through the contact of the gas and a liquid in which the desired substance dissolves.

• Distillation – Boiling a mixture of chemical species in order to separate them using their different boiling points.

• Drying – Removing of liquid content in a material through evaporation.

• Evaporation – Removing a material from a mixture through vaporization.

• Extraction (Liquid-Liquid Transfer) – The transfer of a substance from a liquid mixture to another liquid both of which are immiscible (don’t dissolve in one another) by contacting them.

• Filtration – Using a filter to separate solid materials from a liquid or gas.

·   

      Fluid Mechanics: This branch of chemical engineering deals with the movement of fluids (gasses and liquids) in order to help in the designing of systems to produce such movements e.g. pumps.

Reaction Engineering: Explains how fast a chemical reaction occurs to help design of systems like reactors to produce the desired amount of a material through a chemical reaction.

Process Control: Explains how the output of a complex system can respond to changes in the input conditions to help design and optimize systems in order to hold a products quality within the desired specifications to lower operating costs.

Materials: Shows how materials like metals, polymers and ceramics respond to mechanical and chemical stress in order to select and manufacture materials with the suitable properties for desired products and processing equipment.

Economics: Shows the variables that have an effect on the cost of a chemical process in order to predict the cost of designs and operating options.

References

[1] “What exactly does a chemical engineer do?” Retrieved March 17, 2011 from http://www.aiche.org/CareersEducation/QuickFacts/index.aspx.

[2]  Solen K.A, Harb J.N (2011): Introduction to Chemical Engineering: Tools for Today and Tomorrow, 5^th ed., 

Basic Units and Conversion Factors

Conversion Factors

Source: Solen K.A, Harb J.N (2011): Introduction to Chemical Engineering: Tools for Today and Tomorrow, 5^th ed.,

 

Defined Units

1 dyne = 1 g*cm/s²

1 erg = 1 dyne*cm = 1 g*cm²/s²

1 J = 1 N*m = 1 kg*m²/s²

1 lbf = 32.174 lbm*ft/s²

1 N = 1 kg*m/s² = 1 Pa

1 Poise = 1 g/cm*s

1 slug = 1 lbf*s²/ft

1 W = 1 J/s

 

Prefixes

Prefix	Meaning	Abbreviation	Example
nano	10-9	n	nanometer (nm)
micro	10-6	μ	micrometer (μg)
milli	10-3	m	millimeter (mm)
centi	10-2	c	centimeter (cm)
kilo	103	k	kilometer (km)
mega	106	M	MP (megapixel)
giga	109	G	GB (gigabyte)
tera	1012	T	TB (terabyte)

 

           Periodic Table

  

Values of Universal Gas Constant, R

0.08206 atm L/gmol K

8.314 J/gmol K

8314.5 J/kgmol K

8.3145 kPa m³/kgmol K

8.3145 x 10⁷ g cm² /s² gmol K

62.37 mmHg L/gmol K

1.987 cal/gmol K

1.987 Btu/lbmol °R

0.730 atm ft³ /lbmol °R

10.73 psia ft³ /lbmol °R

1.3145 atm ft³ /lbmol °R

1545 ft lbf/lbmol °R