Recently Updated Chemical Interview Questions Part – 2
What Is The Use Of Gear Pumps In Motor?
Gear pumps uses meshing gears that allow the pump fluid to be displaced by the method of displacement. They are used for hydraulic fluid power applications. They are one of the key factors involved in chemical installation having a certain viscosity to pump fluid. This type of pumps uses positive displacement pump having high pressure and low capacities.
This includes the ability to handle wide range of viscosities, and allow easy to build and maintain the pumps. The gear pumps are controlled through the motor speed. Gear pumps can’t handle high tolerances and the fluids that are free of abrasives.
What Are The Factors Involved In Considering The Choice Of Dry Screw Compressor?
Screw compressors are made up of a pair of meshing helical screws that is used to compress the gases. The dry screw compressors are used to have a flow range of 85-170 m/h and the discharge pressure is of 2070-2760 kPa. The dry screw compressor consists of timing gears that is maintained aligned with the rotors.
The effectiveness is dependent on the clearances that exist between the helical rotors and between the chambers used for sealing the compression cavities. They are compact and smooth having the limited vibration and require spring suspension as well.
What Is The Process Of Including Heat Exchangers In Ammonia Refrigeration System?
The heat exchangers are used in ammonia refrigeration system from a very long time. The heat exchanger used is having smaller sizes and they are equivalent to the tubular exchanger can. This process works best for flooded system that require a separate liquid from the vapor. The system that is explained consists of a vessel, a drum, and accumulator and header tank with the heat exchanger.
It works like this:
Liquid ammonia moves from vessel to exchanger
Vapor is returned to middle of drum
Vapor is removed from the drum and liquid enters through exchanger as it has lower density than others entering at the same rate in the system
What Is The Method Adopted To Minimize Shell Side Pressure Drop In A Shell?
The method of protecting the shell from the pressure drop is very essential as it is very critical stage, where if not taken care properly the shell has to be replaced due to its degradation. In this rods or tube protectors are used instead of plates in top rows. The use of these rods puts less pressure drop and provides better distribution of the pressure on the plate.
The plate that is used causes an abrupt of 90 degree turn of shell stream and an extra pressure drop on the whole shell. Use of the tube protectors will allow the shell to be saved from this and maintains its longevity.
What Are The Strategies Acquired To Cure Tube Vibration And Exchangers In A Shell?
The strategies that can be followed are as follows:
To cure the tube vibration uses the tubes that doesn’t allow passing of the flow-induced vibrations through them and are longer in height than others. Usually the tubes supported
Are of 3-4 inch. To make the bundle stiff insert metal slats and rods between the tubes that is used in the process.
Add a shell nozzle opposite of the inlet to cut the flow of the velocity of the fluid in half. This solution works for non-removable bundles that can easily be solved also by adding a distributor belt on the shell. This might be expensive solution to adopt as it requires more man power and use of more tubes.
What Are The Factors Involved In Designing Kettle Type Reboiler?
To design the kettle type reboiler the requirements that needed to be present are as follows:
The size of the kettle has to be determined.
Provide the space to slow down the vapor velocity of all the liquid droplets.
Deciding the destination where the vapor would be deposited.
Handling a distillation tower with the following property: large space, high efficiency and high reflux rate.
The height of the vapor space should be kept such that the differences in the temperature won’t affect the kettle. There should be high heat flux for the kettles that run on higher temperatures.
What Are The Steps Taken To Operate A Tank-blanketing Valve?
The steps taken are as follows:
Tank blanketing valves provide a way to prevent and control the fires in the flammable liquid storage tanks.
The vapors that are produced cannot be ignited if there is no supply of oxygen present at that time.
The oxygen in most of the cases being provided by the air that is drawn into tank from the atmosphere when the empty process is taking place.
Install tank blanketing valves with inlet connected to the inert gas that is kept under the pressure. And the tanks outlet is being placed in vapor space.
The pressure drop is happening in the tank at predetermined level where the blanketing valve allows the transfer of gas into vapor space.
What Are The Steps Required To Design A Vapor-liquid Separator Or Flash Drum?
The steps that are required are as follows:
The size of the vapor-liquid separator depends on the flow rate of vapor and the liquid that is coming out of the vessel.
Assumed from the flow rates that if they are known then the size can be found out.
Use vertical pressure vessel to set it up or install it at given location.
The length to diameter ratio will be taken to provide liquid inventory between the level of liquid and the bottom of the vessel.
Provide a blockage mesh section at the vapor outlet to let the vapor pass through the mesh that is taken and can successfully leave the vessel.
Let liquid flow control the level of the valve.
Why Does Catalytic Converter Used In An Automobile?
The catalytic converter is a device that converts harmful compounds in harmless compounds.
The compounds harmful in nature are as follows:
Hydrocarbons- this is in the form of unburned gasoline that creates pollution and is more harmful.
Carbon monoxide is very harmful gas formed by the combustion of gasoline and used mainly for fuels.
Nitrogen oxides is also one of the gases that is poisonous in nature and produced by the release of heat from the engines. The release of nitrogen from the engine gets mixed with the oxygen in the air.
The catalyst converter takes these harmful gases and uses the catalyst that is coated on the ceramic honeycomb or beads and attached to the exhaust pipe. This converts the carbon monoxide in carbon dioxide and makes it easy for the nature to consume it. The hydrocarbon gets converted in carbon dioxide and water. Same way the nitrogen oxides also gets converted in nitrogen and oxygen.
What Are The Different Ways In Which Solids Can Be Blended?
There are various ways in which solids can be blended, some of the common methods are:
Convective mixing:
In this type of mixing the group of particles of a solid is transferred from one place to another, vigorous repositioning takes place in this method. This type of mixing is prevalent in the Trough mixer.
Diffusion mixing:
In this type of mixing a new interface is formed over which the particles of a solid are distributed. A good example of diffusion mixing is in the traditional barrel mixer, where a new interface is formed.
Shear Mixing:
In this type of mixing slipping planes are created over which the group of particles of a solid are mixed.
What Are The Different Types Of Equipments For The Conveyance Of Solids?
The various types of equipments available for the conveyance of solids are as follows:
Gravity Chutes:
This equipment relies on gravity for the solids to fall under.
Air Slides:
In this equipment the particles are suspended in air, and flow at an angle to the horizontal.
Belt Conveyors:
This equipments use a belt to transfer the solids.
Screw Conveyors:
The solids are moved using a rotating helical impeller.
Bucket elevators:
The solids are moved using buckets which are attached to a belt in motion.
Vibrating Conveyors:
The solid particles are subjected to vibrations and travel over to a table in a series of steps.
Pneumatic/ Hydraulic Installations:
The particles are transported over a stream of air or water.
What Are The Reasons Of Removal Of Particles From Effluent Gas?
The main reasons for the removal of particles from effluent gas are:
In order to protect and maintain the health of the workers and operators in the plant. It is also done to protect the surrounding population. The primary danger is due to the inhaling of the dust particles which can cause health issues.
It is also done to minimize the chances of explosions. Many carbonaceous materials remain suspended in air and when mixed with finely powdered metals can form a highly combustible mixture.
Particles are also removed to reduce the loss of valuable materials.
It can also be used to recycle the gas for ex in case of blast furnaces the gas is used to fire the stoves.
In A Crusher Where Is The Energy Provided To It Is Used Up For?
The energy fed to a crusher is utilized for the following purposes:
To produce the elastic deformation of the particles prior to the fracture of the particles.
In order to produce inelastic deformation this causes the particles to reduce in size.
The energy is also used to cause the equipments elastic distortion.
In the friction of the particles between themselves and between the machine.
The energy also gets used up in the form of heat, noise and vibration in the plant.
The energy also get used up in the friction losses in the plant. Most of the energy is lost and only some of it is properly utilized. Nowadays it is of prime importance to reduce the energy losses.
On What Basis Are Materials To Be Crushed Evaluated Apart From Size?
The choice of the crusher machine to be employed to crush the materials depends on the following properties apart from the size of it:
Hardness:
The hardness affects the power consumption and the wearing of the machine. With hard materials it is necessary to use a low speed machine along with pressure lubrication.
Structure:
Normal granular materials can be crushed by using compression and impact methods. On the other hand for fiber like materials compression and impact methods don’t work instead a tearing action is required.
Moisture content:
The moisture content in the materials can greatly affect the choice of machines. In case of excess moisture the materials flow gets hindered and it is essential to prevent them from caking together and form balls.
Crushing Strength:
The amount of power that is required to crush a material can be derived directly from the crushing strength of the material.
Friability:
This property indicates the tendency of a material to fracture.
Stickiness:
As the name suggests this property is used to evaluate how sticky a material is as a very high sticky material can clog the machinery.
What Are The Advantages Of Using A Ball Mill Over Other Conventional Methods Of Crushing?
The advantages of using a ball mill over other conventional methods are as follows:
The mill can be used in multiple modes. It can be used in both wet and dry modes. The wet mode helps in the removal of the product.
The installation cost and the power consumption of the mill is low.
Since the mill can be used in an inert atmosphere hence it could be used for the crushing of explosive materials.
It can be used for any type of hardness materials and also the grinding medium is cheap.
It can also be used for continuous and batch operations.
The ball mill supports two types of grinding:
Open circuit grinding > Closed circuit grinding
Mention Some Of The Specialized Grinding And Crushing Methods?
Some of the specially developed grinding and crushing methods are as follows:
Electrohydraulic crushing: In this method an underwater discharge is created from a high capacity capacitor.
Ultrasonic Grinding: This type of grinding the material id placed between a drive roll and plate both of which are ultrasonically activated. This process is used for grinding micro sized materials.
Cryogenic grinding: For certain materials effective grinding is not possible by conventional means such as rubber, textiles etc. In order to cope with this problem the material is frozen to ultra low temperatures using liquid nitrogen. Once the material is frozen it is grounded as per requirements.
Explosive Shattering: This type of shattering is still on experimental basis, it involves energy to be transmitted to the particles in the form of shockwaves from an explosion chamber.