How does a reboiler work?

Asked by: Garth Bogisich
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Reboilers are heat exchangers typically used to provide heat to the bottom of industrial distillation columns. They boil the liquid from the bottom of a distillation column to generate vapors which are returned to the column to drive the distillation separation.

How does kettle reboiler work?

A kettle reboiler is designed to allow a heating fluid to pass through tubes that are covered in the liquid you want to be distilled. As the liquid heats up and boils, it is sent to the distillation column and condensed by cooling liquid.

What is the purpose of Reboiling in a distillation system?

The purpose of the reboiler is to produce the vapour stream in the distillation column, called the reboiled vapour or the boil-up vapour. Reboilers can be both external or internal (stab-in). Steam reboilers or fired reboilers can be used. Fired reboilers typically uses fuel gas or fuel oil or combination of both.

What is the difference between reboiler and condenser?

Condensers are responsible for removing heat from vapor so it can be converted to liquid. ... For instance, process condensers relocate heat from process streams into utility-based streams, while utility condensers move it in the opposite direction. The former carry more importance operationally.

32 related questions found

What is reboiler used for?

A reboiler is a heat exchanger that is used to generate the vapor supplied to the bottom tray of a distillation column. The liquid from the bottom of the column is partially vaporized in the exchanger, which is usually of the shell-and-tube type.

What is the purpose of condenser?

The function of the condenser in a refrigeration system is to transfer heat from the refrigerant to another medium, such as air and/or water. By rejecting heat, the gaseous refrigerant condenses to liquid inside the condenser. The major types of condensers used are (1) water-cooled, (2) air-cooled, and (3) evaporative.

What is a good distillation rate?

An appropriate rate of distillation is approximately 20 drops per minute. Distillation must occur slowly enough that all the vapors condense to liquid in the condenser.

Is a distillation column hotter at the top or bottom?

The basic temperature profile of a distillation column is hotter at the bottom and cooler at the top. For a simple two component distillation the temperature at the bottom is just lower than the boiling point of the heavier component.

What is the minimum reflux ratio?

The minimum reflux ratio Rm is the limiting reflux where the operating line either touches the equilibrium curve or intersects the equilibrium curve at the q-line. The minimum reflux ratio will require an infinite number of trays to attain the specified separation of xD and xB.

Why is a kettle reboiler an ideal stage?

Because the vapor is directly generated by boiling on the surfaces of heated tubes, a kettle reboiler is a very close approximation to a theoretical stage.

What is thermosyphon effect?

Thermosiphon (or thermosyphon) is a method of passive heat exchange, based on natural convection, which circulates a fluid without the necessity of a mechanical pump. ... Its purpose is to simplify the transfer of liquid or gas while avoiding the cost and complexity of a conventional pump.

Why must the tubes in a kettle reboiler always be submerged by liquid?

Heat transfer suffers as the heat transfer coefficient is lower in vapour than in liquid. It will also lead to higher temperature on the exposed tubes, leading to metal over-heating. It is important to ensure that the tubes are always flooded by liquid set by the overflow weir.

What are the two types of heat exchangers?

There are two main types of regenerative heat exchangers—static heat exchangers and dynamic heat exchangers.

What is a total reboiler?

The reboiler is total. The last stage in the McCabe-Thiele construction corresponds now to a physical plate of the column and not anymore to the reboiler. In case of total reboiler, the entire liquid stream coming out from the last stage of the column is entirely vaporized.

What is total reflux?

A condition in which all the overhead product from a distillation column is returned back to the column as reflux.

What is bottom of distillation column?

The vapour raised in the reboiler is re-introduced into the unit at the bottom of the column. The liquid removed from the reboiler is known as the bottoms product or simply, bottoms. The vapour moves up the column, and as it exits the top of the unit, it is cooled by a condenser.

Where is the fractionating column the hottest?

Fractional distillation

This uses a fractionating column that is hotter at the bottom, and cooler at the top. The different liquids are collected from different parts of the column.

Where in a distillation column is the temperature the lowest?

Where in a distillation column is the temperature the lowest? At the bottom of the column, because the heat rises to the top due to natural convection of the hot gas flow.

Why is rapid distillation bad?

Things to Watch Out For In Distillations:

(2) Distillation is too rapid due to excessive heating - this leads to a poor separation. ... (3) Not enough heating - this leads to reflux (a condition in which the vapors condense and return to the distilling flask) instead of distillation.

What can go wrong with distillation?

The distillation result is poor: the fractions obtained are not of acceptable purity. Typical problems: Distillation too fast. The components require time to separate. We need many evaporation-condensation cycles for good separation, and pseudo-equilibrium between vapor and liquid throughout the system.

When should you not use simple distillation?

A simple distillation is incapable of significant purification if the boiling points of the components are too close. When the difference in boiling points is less than 100 ˚C, a modification is necessary, namely insertion of a fractionating column between the distilling flask and three-way adapter.

What is the difference between a compressor and condenser?

The compressor “squeezes” the gas. ... It actually changes the gas refrigerant into a liquid, which is used throughout the A/C system to eventually produce cold air. The condenser is responsible for taking the pressurized gas from the compressor and changing it into a liquid vapor.

Is refrigerant a liquid or gas?

The refrigerant, a chemical compound that changes easily from liquid to a gas. When the refrigerant is pushed into the compressor, it is a low pressure gas.

Which one of the following best describes the function of condenser?

1. Which one of the following best describes the function of a condenser? Explanation: Condensers use the property of condensation which is a convective heat transfer process that is associated with a change in the phase of a fluid from the gas to a liquid phase.