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Evaporators Used in
Brewing & Beverage Industries

During the brewing process, it is often desirable to eliminate a portion of the water from the beer in order to thicken the beer and increase the alcohol percentage. This can be done by heating up the large brew kettles to a high enough temperature to evaporate some of the water. This is typically a very long process, requiring large amounts of utility energy.

A more efficient way to perform this evaporation it to recirculate the beer through an external vertical heat exchanger, often called an external calandria. This exchanger will typically have steam running through the shell of the unit, and the beer is fed upward through the tubes. As the steam heats the beer in the tubes, some of the water in the beer flashes off as steam and exits the top of the exchanger to be condensed, while the remaining liquid beer is piped back over to the brew kettle. This recirculation through the exchanger continues until the desired amount of water has been removed (typically 6%). Compared to heating the entire kettle, a calandria boils the beer in a fraction of the time.

Evaporators and Reboilers Used in
the Cannabis Industry

After oil extraction using ethanol or hydrocarbons, there is a need to vaporize and recover the solvents from the product.  An efficient way to perform this evaporation it to feed the product stream up through a vertical shell and tube heat exchanger, often called an external calandria or reboiler. This exchanger will typically have steam or hot thermal oil running through the shell of the unit, and the oil and solvent mix is fed upward through the tubes. As the steam or thermal oil heats the solution in the tubes, the solvents in the product flash off as vapor and exit the top of the exchanger to be condensed, while the remaining product is piped to the next step in the process.

Another type of evaporator used for this type of separation is a falling film evaporator, where the product mix flows down through the tubes instead of upward.  Heating medium is provided in the shell side of the exchanger, and the vapors flash off as the product drips down the inside of the tubes.

Since oil and solvent mix, and their thermal properties can vary from case to case, design of evaporators is often performed by OEM’s that specialize in evaporation.  Many of them have R&D test centers where products can be tested and thermal performance confirmed, in order to properly size the shell and tube exchanger used as the evaporator.  Evaporators and reboilers are not easily scalable, and can have performance issues when flow is turned down, or if flow exceeds the tested rate.  Because of this, it may be necessary to have multiple evaporators sized for different flow rates on different production lines.

Evaporators and reboilers used to remove solvents from product should have product contact surfaces polished to at least food grade 32Ra levels.  Better finishes like those found in pharmaceutical applications can also be provided, typically 20Ra and electropolished.  Because of these finish considerations, it is best to keep the product in the tube side of the exchanger, and utilize the shell side for utility streams.

Evaporators and Reboilers Used in
the Chemical Industry

Most reboilers are made with shell and tube heat exchangers and are typically used in distillation processes. Boiling liquid from of the bottom of industrial distillation columns, reboilers generate vapors that are returned to the columns, driving distillation separation. The same heat from the reboiler at the bottom of the column is removed by the condenser at the top.

The most common types of shell and tube reboilers are kettle reboilers, forced circulation reboilers and thermosyphon reboilers.  A kettle reboiler is a horizontally mounted exchanger with a removable U-tube insertion bundle that contains the heating medium, like steam or hot thermal oils.  The product enters the shell of the exchanger, and floods over the hot bundle, evaporating in the process.  The shell typically has a larger diameter than the bundle in order to provide some head space for the vapors prior to them leaving through the top of the shell.  A forced circulation reboiler is typically a vertically mounted exchanger, with the product entering the tube side of the unit through the bottom head.  Steam or hot oil is used on the shell side of the reboiler to heat the product as it rises up through the tubes.  Separate ports in the top head allow for the separation of the vapors from residual liquids in cases where the reboiler is being used as a calandria or partial evaporator for separating or thickening product.  A thermosyphon reboiler is similar in construction and orientation to the forced circulation reboiler, but relies on the pressure differential caused by the evaporation taking place to pull the product up through the tubes.  Often this process is started with the assistance of a pump, and once evaporation begins, the pump can be turned off as the thermosyphon effect begins.

This distilling process is regularly used in industries that refine oil, desalinate water, create liquor, beer and wine, and produce many chemical products used in homes and factories.

While reboilers separate materials based on weight, evaporators are used to separate materials based on their boiling temperatures. Evaporators, as shell and tube heat exchangers, transfer heat between the outer shell and product in the inner tubes.  Evaporators are often linked together in trains for multi-effect distillation.  In this scenario, each evaporator heats the product to a specific temperature to remove a component of the product at a predetermined boiling point.  The remaining product slurry is then sent to another evaporator set at another predetermined boiling point to remove another specific product component and so on.  The evaporated components are often used on the shell side of the next evaporator in line to heat the product in the tubes.  The boiling point in each evaporator is controlled by the vacuum or pressure level of the product at each stage.

In a rising film evaporator, the liquid being evaporated is fed into long tubes and heated with steam on the outside of the tube (from the shell side). This produces steam and vapor within the tubes and brings the liquid in the tubes to a boil. The vapor produced creates a thin film that rises.

Evaporators and Reboilers Used in
the Refining & Renewable Energy Industry

Most reboilers are made with shell and tube heat exchangers and are typically used in distillation processes. Boiling liquid from of the bottom of industrial distillation columns, reboilers generate vapors that are returned to the columns, driving distillation separation. The same heat from the reboiler at the bottom of the column is removed by the condenser at the top.

The most common types of shell and tube reboilers are kettle reboilers, forced circulation reboilers and thermosyphon reboilers.

A kettle reboiler is a horizontally mounted exchanger with a removable U-tube insertion bundle that contains the heating medium, like steam or hot thermal oils. The product enters the shell of the exchanger, and floods over the hot bundle, evaporating in the process. The shell typically has a larger diameter than the bundle in order to provide some head space for the vapors prior to them leaving through the top of the shell.

A forced circulation reboiler is typically a vertically mounted exchanger, with the product entering the tube side of the unit through the bottom head. Steam or hot oil is used on the shell side of the reboiler to heat the product as it rises up through the tubes. Separate ports in the top head allow for the separation of the vapors from residual liquids in cases where the reboiler is being used as a calandria or partial evaporator for separating or thickening product.  An example of a forced circulation reboiler used in refining is a LNG vaporizer.  These are often enhanced by the addition of twisted tape turbulators that are inserted into the tubes to enhance the vapor flow and keep the gas in suspension once it vaporizes.

A thermosyphon reboiler is similar in construction and orientation to the forced circulation reboiler, but relies on the pressure differential caused by the evaporation taking place to pull the product up through the tubes. Often these are started up with the assistance of a pump, and once evaporation begins, the pump can be turned off when the thermosyphon affect begins.

This application of reboilers in the distilling process is regularly used in industries that refine oil, desalinate water, create liquor, beer and wine, and produce many chemical products used in homes and factories.

While reboilers separate materials based on weight, evaporators are used to separate materials based on their boiling temperatures. Evaporators, as shell and tube heat exchangers, transfer heat between the outer shell and product in the inner tubes. Evaporators are often linked together in trains for multi-effect distillation. In this scenario, each evaporator heats the product to a specific temperature to remove a component of the product at a predetermined boiling point. The remaining product slurry is then sent to another evaporator set at another higher predetermined boiling point to remove another specific product component and so on. The evaporated components are often used on the shell side of the next evaporator in line to heat the product in the tubes. The boiling point in each evaporator is controlled by the vacuum or pressure level of the product at each stage.

In a rising film evaporator, the liquid being evaporated is fed into long tubes and heated with steam on the outside of the tube (from the shell side). This produces steam and vapor within the tubes and brings the liquid in the tubes to a boil. The vapor produced creates a thin film that rises.

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