Chemical Engineering interview questions and answers - part 4

          

Chemical Engineering interview questions and answers - part 4


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18. 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.

19. 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.

20. 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.

21. 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.

22. 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.

23. 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.

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