Top Most Chemical Interview Questions Part – 4
How Can Separation Of Chiral Chemicals Affect The Chemical And/or Pharmaceutical Industries?
This enantiomers (left [S] or right [R] oriented) versions of the same compound can have very different properties; this development has been significant particularly in the pharmaceutical industry. For example, the drug Seldane is a racemic mixture of both S and R versions of the drug’s molecules.
Through chiral separation technology, Hoechst was able to bring the drug Allegra to market in only 3 years (far less time than is usually necessary). Hoechst was able to bypass toxicity testing because Allegra is a single chiral form of its molecule. By chiral separation, the most of the side effects of Seldane were avoided in Allegra.
Can Asphalt Be Recycled To Form A Useful Product?
Asphalt can be ground into small pieces and emulsified to form a 70% oil/30% water mixture. This fuel can be used to power boilers. It has a heating value of 6,600 kcal/kg and is said to be stable for about 6 months.
What Is A Surfactant?
A surfactant is a chemical that reduces the surface tension of pure liquid or a mixture of liquids.
What Is A Good Source Of Surfactant Information On The Internet?
Check out the Surfactant Virtual Library at the link below.
What Is The Wet Bulb Globe Temperature (wbgt)?
The sultriness of the ambient environment is more than a comfort factor. For workers, soldiers and athletes, high levels of sultriness may result in heat stress that could very well be life threaten. To determine the actual degree of sultriness in a quantifiable manner, the Wet Bulb Globe Temperature (WBGT) index is used.
It includes the effects of humidity, air speed, air temperature and the radiant heating factor (from the sun). This index was developed by the U.S. Military in the 1950’s and has become widely accepted for industrial temperature measurements to protect employees.
It combines three temperature readings: the wet bulb temperature; the ordinary dry bulb temperature and a black bulb globe temperature. There are also instruments available, which measure WBGT index directly, combining the three factors and their appropriate weighting values.
How Can Metals Be Removed From Aqueous Waste Streams?
Precipitation is widely used to remove metals from waste streams. The soluble heavy-metal salts can be converted to insoluble salts that will precipitate and can then be removed by clarification, filtration, or settling.
What Are Some Common Precipitating Agents Used To Remove Metals From Aqueous Waste Streams?
Perhaps the most common agents used are:
Metal hydroxides
Lime or caustic soda
Metal sulfides
Alum or ferric salts
Phosphate or carbonate ions
What Types Of Metals Are Typically Removed Via Chemical Precipitation?
Some of the more common metals or other substances removed via precipitation include:
Aluminum
Arsenic
Barium
Cadmium
Calcium
Trivalent chromium
Hexavelent chromium
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Selenium
Zinc
How Can Hexavalent Chromium Be Removed From Aqueous Waste Streams?
One option is to use ferrous sulfate to reduce the hexavalent chromium to a less toxic, trivalent chromium form that wills precipitate out of the solution. Trivalent chromium can then be reduced by sodium hydroxide.
How Can Arsenic Be Removed From Aqueous Waste Streams?
Often times, ferric chloride is added to such a stream. The ferric chloride aids in the formation of floc to agglomerate fine arsenic particles that can then be removed by mechanical means.
How Can I Treat A Waste Stream Containing Both Hexavalent Chromium And Arsenic?
Waste streams that contain these types of mixtures are often treated in two or more reducing tanks. Strong reducing agents such as sodium metabisulfite, sulfur dioxide, and sodium bisulfite are often used.
How Many Grams Per Liter Would There Be In A 0.35 N (normality) Citric Acid Solution?
The normality of a solution is the number of gram-equivalent weights of the dissolved substance per liter of solution. The gram-equivalent weight of the dissolved substance is the molecular weight of the dissolved substance divided by the hydrogen equivalent of the dissolved substance.
Citric acid has a molecular weight of 192.12 and it contains three hydrogen equivalents (i.e., three COOH groups). Thus, the gram equivalent weight of the citric acid dissolved in water is 192.12/3 = 64.04 grams. Therefore 0.35 Normal citric acid would have (0.35)(64.4) = 22.41 grams of citric acid per liter of solution.
What Is An Additive?
An additive is anything that is added to a process that is not a basic raw material. It is usually present in such small quantities that it does not interfere with final product quality. It is usually added to act as an enhancer or to prevent some unwanted reaction. For instance, anti-foam additives are added to columns, evaporators, reactors, etc.
to prevent foaming. Inhibitors are added to Styrene systems to prevent polymerization. A well-known additive is a detergent added to motor oils and gasoline to keep your engine clean.
What Chemical Is Used To Expand Air Bags In Such A Short Amount Of Time?
That chemical is sodium azide (NaN3) which is a solid propellant that can be electrically ignited to form nitrogen gas almost instantly.
What Steps Can Be Taken To Avoid Stress Corrosion Cracking (scc) In Steel Vessels Used For Storing Anhydrous Ammonia?
The U.S. National Board of Pressure Vessel Inspectors recommends the following in one of their classic articles:
Pressure vessels should be fully stress relieved or fabricated with heads that are hot-formed or stress relieved.
Extreme care should be used to eliminate air from the ammonia systems; new vessels must be thoroughly purged to eliminate air contamination.
Ammonia should contain at least 0.2 percent water to inhibit SCC. Source: National Board of Pressure Vessel Inspectors
How Can Wet Carbon Dioxide Be Responsible For A Corrosion Problem In Iron-containing Metals?
Carbon dioxide reacts with water according to the following equation: CO2 + H2O –> HCO3- + H+ As the concentration of CO2 increases, so does the concentration of the H+ ion.
This ion can then react with Fe in metals as follows: Fe + 2H+ –> 2H (atom) + Fe2+ As corrosion proceeds, the ferrous ions produced can react with the bicarbonate ions to form ferrous carbonate, which precipitates as a scale.
Is It Possible To Compare The Resistance To Chloride Attack Of Several Materials Of Construction?
The Pitting Resistance Equivalent Index (PRE) can be used for such a comparison if the chemical make-up of each material is known. The formula for the PRE is PRE = % Cr + (3.3 x % Mo) + (30 x % N).
What Is The Angle Of Repose And What Are Its Applications In The Chemical Industry?
The dictionary defines “angle of repose” as “the inclination of a plane at which a body placed on the plane would remain at rest, or if in motion would roll or slide down with uniform velocity; the angle at which the various kinds of earth will stand when abandoned to them”.
Applications to the chemical industry…think about the design of the conical section of a storage bin. The material would not fall out the bottom, as we may want. This concept is also important in the design of system designed to move bulk solids…for the same reasons.
How Is Waste Heat Boilers Categorized?
Chemical plants -(hydrogen, nitrogen, sulfuric acid, sulfur recovery) Incineration plants-(fumes, chemicals, municipal solid waste) Refineries-(cat cracker, CO off gases) Cogeneration, combined cycle plants-(gas turbine, diesel engine exhaust) Furnaces, kilns-(exhaust gases) See a complete table at the link below.
How Do You Design A Vapor-liquid Separator Or A Flash Drum?
The size of a vapor-liquid separator should be dictated by the anticipated flow rate of vapor and liquid from the vessel. The following sizing methodology is based on the assumption that those flow rates are known.
Use a vertical pressure vessel with a length-to-diameter ratio of about 3 to 4, and size the vessel to provide about 5 minutes of liquid inventory between the normal liquid level and the bottom of the vessel (with the normal liquid level being at about the vessel’s half-full level).
At the vapor outlet, provide a de-entraining mesh section within the vessel such that the vapor must pass through that mesh before it can leave the vessel. Depending upon how much liquid flow you expect, the liquid outlet line should probably have a level control valve.
How Can Viscosity Affect The Design Of A Mixer?
For Newtonian fluids, which will have a constant viscosity at all impeller speeds, most design correlations will perform satisfactorily for viscosities up to 5,000 cP. Above 5,000 cP, estimating errors from 20% to 50% can result in the sizing of the agitator.
What Information Is Needed To Specify A Mixer?
Specific Gravity
Fluid Viscosity
Phase to be dispersed
Solid-liquid systems
The settling velocities of the 10, 50, and 90 percent weight fractions of the particle size distribution should be available. 5. For gas systems, the standard and actual flow rates will be needed.
Is There Any Way To Slow Coke Formation In Ethylene Furnaces?
Westaim Corporation has a commercial process for applying a special coating to the tubes used in ethylene furnaces. Westaim claims that coke buildup is reduced to one-forth to one-tenth of the normal rate.
The coating consists of a combination of metal, ceramic powder, and a polymer. Once the coating is applied, the tubes are then heat-treated and reacted with an unspecified gas. Welds cannot be coated with this process.
What Are Some Typical Applications For Glass-lined Reactors?
Glass-lined equipment gives superior protection to all mineral acids at all concentration and temperatures. One exception is hydrofluoric acid. They are also used is high-purity processes where cleanliness is very important. Using glass-lined equipment help eliminate the possibility of metal contamination.
A third application is in polymerization. Metallic vessels sometimes tend to allow the polymer to stick to the walls of the vessels while glass-lined vessels have good anti-stick properties.
At What Temperature Is Glass Fused To Steel In The Making Of Glass-lined Equipment?
The borosilicate glass is typically fused to carbon steel at a temperature of about 800 0C.
How Are Vessel Lined With Glass Or How Are They Coated?
First, the glass mixture is smelted for form the proper recipe based on temperature and pressure requirements of the vessel. Then the glass is ground into tiny particles and suspended in a liquid medium called a slip. This mixture is then spayed onto the surface to be coated.
The vessel is then heated to 800 0C to bond the glass to the steel (usually carbon steel). The vessel is then slowly cooled.
Are There Any General Rules That Should Be Considered When Designing A Slurry Piping System?
The following are items to consider when designing a piping system that will transport slurries:
Whenever possible, piping should be designed to be self-draining
Manual draining should be installed to drain sections of the piping when self-draining is not possible
Blow-out or rod-out connections should be provided to clear lines in places where plugging is likely or could occur
Access flanges should be provided at T-connections
Manifolds should have flanged rather than capped connections to allow for easy access
Clean-out connections should be provided on BOTH sides of main line valves so that flushing can take place in either direction
Break flanges should be provided every 20 feet of horizontal pipe or after every two changes in direction
What Is The Method Of Determining Maximum Differential Pressure During Hydro Testing Of Shell And Tube Heat Exchangers?
Mr. Richard Lee of Plumlee International Consulting usually heat exchangers have two sets of test pressures per side, one for strength tests, and the other for “operating” or “leak” tests. The strength tests are set by the design code and if you have the original design data sheets for your equipment then the information should be shown on these.
If you do not then you will have to do the calculations yourself, the exact method will depend upon which design code you use, the most common one being TEMA (which uses the ANSI/ASME pressure vessel code for reference in this area).
Most shell and tube exchangers are designed such that each side of the unit will withstand the full design pressure, with only atmospheric pressure on the other side.
In order to save money, some larger units will have the tube-sheets especially designed to withstand only a much lower differential pressure (requiring both sides to be tested simultaneously). This important information should be shall quite clearly on the design sheets and on the vessel nameplate (assuming that either are available).
If the only need is to check that a gasket has been properly installed then it can be permissible to perform a lower pressure test based on the operating pressure. The acceptability of this lower pressure test will often depend upon the consequences of a leak.
What Is A Good Source Of Information For The Design Of Pressure Vessels?
Pressure Vessel Handbook Author = Eugene F. Megyesy Publisher = Pressure Vessel Handbook Publ., Inc. P.O. Box 35365 Tulsa, OK 74153 Page 18 tells you how to calculate a pressure vessel’s wall thickness; page 176 tells how to calculate an API Std. 650 Storage tank wall thickness.
The rest of the book is a goldmine for young engineers – especially CHE’s involved in vessel design. It also gives all the information you require for supports, nozzles, head design, piping, ladders, platforms, etc.