Best Chemical Interview Questions Part – 8
What Are Some Common Problems Associated With Dilute Phase Pneumatic Conveying?
Probably the most common problem encountered in dilute phase pneumatic conveying is the wearing of the rotary valve that serves as an air lock where the product is introduced into the system. If excess air is allowed to pass by the rotary valve, this can cause bridging of the material the flow can be slowed or stopped.
What Are Some Common Problems Associated With Dense Phase Pneumatic Conveying?
Dense phase pneumatic conveying, typically experiences one common problem from system to system: plugging in the line due to a malfunctioning booster valve. Dense phase systems require these booster systems to introduce new, pressurized air. These boosters are nearly always accompanied by a check valve. If the check valve becomes stuck, the product is allowed to plug the line.
What Is The Most Common Carrier Gas Used In Pneumatic Conveying?
While many applications utilize air as a carrier gas, others are not suited for using air. For example, if the substance being conveyed reactions with moisture in the air or if there is a threat of dust explosions, nitrogen is likely choice.
What Types Of Pneumatic Conveying Systems Are Typically Used?
Essentially, there are two types of pneumatic conveying systems. In dilute phase systems, the solids are suspended in the carrier gas and transported to their destination. In dense phase systems, the solids-to-gas ratio is much higher. The gas in these systems acts more like a piston to push the product to its final destination.
Dilute phase systems are more typical than dense phase systems because they can employ positive pressure displacement or a vacuum system. Dense phase conveying is useful if the product degrades easily (works at lower velocities) or is particularly abrasive.
What Is Pneumatic Conveying?
Pneumatic conveying is a method of moving bulk solids from one place to another with the help of a carrier gas. A differential pressure is applied inside a conveying line. The flow always moves from a region of higher to lower pressure.
What Is The Practical Particle Size Limit For Pneumatic Conveying?
As a rule, pneumatic conveying will work for particles up to 2 inches in diameter with a typical density. By “typical density”, we mean that a 2 inch particle of a polymer resin can be moved via pneumatic conveying, but a 2 inch lead ball would not.
What Can Cause Bulk Solids To Stop Flowing From A Bin?
Causes of such problems can fall into one of two categories: Material strength or Bin Geometry: Factors that can affect material strength include. Moisture is especially with particles, which fuse together with moisture.
We Wanted To Know How To Impart Various Colors To Copper Wire By Simply Dipping Them Into Various Chemicals, Formulations, Etc.
This Copper Wire Is To Be Used By Us For Our Hobby Of Making Various Art Objects From Copper Wire.
Changing the color of copper by means of chemical reactions is a dangerous Endeavour that I really do not recommend. However, there is something you can do to get a green color, if fact if you are familiar with the Statue of Liberty here in America, this would explain why it is green.
You see, the outside of the statue is coated with copper and being in New York City, it is subjected to acid rain. This causes the formation of another chemical that coats the copper and gives the statue its green color.
The two acids that you can use are nitric acid (which works best) or sulfuric acid (which will probably require some gentle heating along with the acid). I am not sure if there were a good way to get nitric acid out of something you may have around the house, you would probably have to buy it.
Sulfuric acid can be obtained from car batteries (the liquid inside). You will want to boil the mixture (to concentrate it by evaporating the water), until you see white fumes (which are very dangerous). Then put your copper is while the acid is hot and leave it there until you get the color you would like.
If you are going to do this, please do it outside or in a well ventilated area and make sure you have some baking soda handy is case you get some of the acid on your skin. If you are looking for a different color or more colors…
What Does The Catalytic Converter On An Automobile Really Do?
A catalytic converter is a device that uses a catalyst to convert three harmful compounds in automobile exhaust gas into harmless compounds.
The three harmful compounds are:
Hydrocarbons (in the form of unburned gasoline)
Carbon monoxide (formed by the combustion of gasoline)
Nitrogen oxides (created when the heat in the engine forces nitrogen in the air to combine with oxygen).
Carbon monoxide is a poison for any air-breathing animal. Nitrogen oxides lead to smog and acid rain, and hydrocarbons produce smog.
In a catalytic converter, the catalyst (in the form of platinum and palladium) is coated onto a ceramic honeycomb or ceramic beads that are housed in a muffler-like package attached to the exhaust pipe. The catalyst helps to convert carbon monoxide into carbon dioxide.
It converts the hydrocarbons into carbon dioxide and water. It also converts the nitrogen oxides back into nitrogen and oxygen.
What Are Pcbs?
PCB is a commonly used acronym for “PolyChlorinated Biphenyls”. These compounds are famous for the disposal problems that they pose to the chemical industry.
Why Is Post-weld Heat Treatment (stress Relieving) Sometimes Necessary For Welded Vessels?
During the welding process, the two metal pieces being joined are subject to extreme temperatures and can cause the crystalline structure of the metal to pass through various metallurgical phases. As a result, hardening (and embrittlement) of the metal can occur to varying degrees (usually dependent on carbon content).
Heat treatment is designed to reduce the hardness in the heat-affected zone of the metals and increase ductility in these sections. Various pressure vessel codes contain the specifics regarding the procedures for post-weld heat treatment. Heat is usually held for one hour per inch of thickness of the metal.
The temperature used is based on the “P-number” of the metals. P-numbers are assigned based on the chemical composition of the metals. Holding temperatures can range from 1100-1350 °F (593-732 °C).
I Would Like To Know How To Size A Partial Combustion Reactor Processing Methane And Oxygen, As A Function Of The Flowrate And Of The Pressure.
In your case, you essentially have two reactions: CH4 + 3/2 O2 —> CO + 2 H2O (incomplete combustion) CH4 + 2 O2 —> CO2 + 2 H2O (complete combustion) each of these reactions has a specific rate at which it occurs. If you wanted to design a reactor properly, you would need to determine the conversion of methane in each of the above reactions.
The upper limit of your flow rate is bound by the rate of reaction. If the flow rate is too high, the reaction simply will not take place (i.e. the flame will burn out). I am not sure that there is a simple relationship between pressure and flow rate in this case.
The gases need to spend a certain amount of time in the reactor in order for the combustion to take place (residence time). Once you know the residence time, you could design a reactor for your specific flow rate.