Process Systems & Pilot Plants

Distillation Towers

We are a turnkey provider of custom distillation tower design & build services. Our team of distillation experts has over 25 years of experience creating optimized distillation column designs for fractional, steam, azeotropic, or any other kind of distillation system. Our team provides:

  • Optimized design & distillation simulation services
  • 2D & 3D model development, including advanced Aspen HYSYS column modeling
  • Proper column sizing and equipment selection
  • Peer reviewed design basis documents including: mass & energy balances, P&ID’s and all other design documentation
  • Off-site modular fabrication (for qualifying projects) or on-site fabrication & assembly services
  • Factory Acceptance Testing & full in-house quality reviews
  • Turnkey project management services from design through startup
  • Full punch-list resolution, on-site training, and on-going support after tower startup

Learn more about our distillation tower capabilities and experience below or call us at 314-845-0077 for more information.

Distillation towers typically have three main components:

  • Column: The column is the main part of the tower and it is where the separation of liquids take place.
  • Condenser: The condenser is where the lighter materials that separate during the distillation process rise to. It is located at the top of the column, and it condenses these gaseous molecules back into liquid.
  • Reboiler: The opposite of the condenser, the reboiler captures the heaviest materials that fall to the bottom of the column and heat them back up to recirculate them in the column.

Most of the expense for a distillation tower design project is in designing and building the column. Condensers and reboilers are widely available commercial units that simply need to specified for your application, purchased, and integrated to work with the column.

Most of the variability in project cost will come from column design, which is not as straight forward. An engineer will need to look at your particular application and probably complete a basic system design before giving a price.

However, there are some factors we know drive costs higher. These include:

  • Size– towers vary in size depending on the number of required stages for separation, how many products you are separating, and so on. Generally speaking, the larger the required tower, the more expensive your system will be. More materials will be required and it will take longer to construct the system.
  • Materials of construction – The materials you work with vary greatly depending on the type of distillation tower, the feed composition, and the operating pressure. Highly volatile or corrosive solutions may require special, more expensive materials of construction, as do hygienic applications.
  • Feed composition – mixtures with similar boiling points or that contain azeotropes or chlorides are harder to separate and may result in a more expensive system because they required more stages or larger recirculation systems, or occasionally, multiple distillation steps. Sensitive feed material (like organics) may also require the column to operate under vacuum or special extraction distillation methods, which can drive prices up as well.
  • Operating pressures and temperatures – operating pressures vary depending on the feed composition of the system, your reflux ratio, and other system requirements. Generally speaking, the larger the operating pressure range, or the higher the required operating pressure, the more expensive the system will become. Narrow ranges require less robust designs, and lower pressures less demanding equipment capabilities.

Distillation towers are complex systems, and no two are alike. Talk to an EPIC expert today about your specific needs: 314-845-0077.


How do distillation towers work?

Distillation towers separate two or more components from each other. Heat is used to evaporate the mixture, and substances with lower boiling points rise to the top of the tower where there are collected and removed. Heavier particles with higher boiling points remain at the bottom of the column, and in this way “bottoms” and “tops” are separated.

Towers themselves are constructed with the basic elements of a main column, with a heating source at the bottom and usually a collection condenser at the top. Distillation towers are designed to have a particular number of stages. Lighter molecules rise & heavier ones fall in a column. At each stage, a certain number of particles will rise or fall. As the substances progress through stages, they gradually separate.

The number of required stages depends on the mixture properties and the desired purity of the end distillate. High individual component volatility or a large difference in boiling points between components both result in less required stages.

The two types of column internals generally used are plates (or trays) or loose packing. Liquid can enter the tower one or points, and will fall towards the bottom of the column as vapor rises. For trayed columns, liquid flows over the trays and along the walls, while vapor bubbles up through the liquid via holes in the trays. In packed columns, liquid flows over the surface of the packing and vapor rises in the air spaces between. All distillation towers are designed to maximize contact between falling liquid and rising vapor to facilitate maximum separation.

The base of the distillation column contains a large volume of liquid consisting mostly of the liquid with higher boiling point. This is sometimes referred to as bottoms. It is a common practice to pull liquid off the bottom of the column and recirculate it back through at a higher point, called “boil up.”

For more information on how distillation columns work, try these resources:

What is a distillation tower?

A distillation tower is a type of process system that separates liquid mixtures by using heat to take advantage of differences in boiling points among mixture elements. For example, ethanol can be separated from water in a distillation tower because ethanol vapors (boils) at 176 degree Fahrenheit and water remains liquid until 212 degrees F.

There are many types of distillation towers. The most common is a fractionating tower, used in the refining industry to pull many by-products of crude oil out of a single distillation column. There are also vacuum distillation towers, steam distillation towers, azeotropic distillation towers, and more.

How are Distillation Towers Designed?

The starting point of all distillation tower design is to determine the relative volatility of the key substances to be separated. Using a mass and energy balance simulation program the physical and chemical properties of the substances you are trying to separate are modeled and the following ratios are applied to determine final column design:

  1. Fs Vapor – Vapor factor ratio. This is used as a starting point for column sizing and adjusted with the other ratios.
  2. GPM/FT2 Liquid – liquid gallons per minute divided by the column area. This is used for preliminary equipment sizing.
  3. Entrainment or Reflux Ratio – measurement of the amount of liquid that passes from tray-to-tray or stage-to-stage up the column.
  4. Flood Ratios, including Downcomer Flood and Jet Flood ratios – These measure the accumulation rate of liquid in the column and help determine tray spacing, placement and hole size.
  5. Weeping Point/Dump Point or Turndown Ratio – This is the point at which liquid starts falling back through the column from each stage or tray. It helps determine ideal column pressure.
  6. Column Efficiency (for trayed columns) – this is usually a measurement of vapor rate vs. weeping and entrainment rates. It can effect column sizing and stage/tray spacing.
  7. HETP – Height Equivalent pf a Theoretical Plate (for packed columns) – based on the McCabe-Thiele diagram theory, this helps you determine how many required stages will be needed to achieve separation in a packed column and affects column sizing.

Once these ratios have been determined, adjustments in column performance and design tradeoffs can be explored in simulation to come up with a final optimized version. It is recommended that you use a experienced distillation column design build firm, like EPIC systems (314) 858-8839 to complete distillation system design. These process experts can help you run accurate simulations to find optimal column design, material balances, and navigate operating tradeoffs.

What information do I need to provide to get a distillation tower quote?

You can have very little information to start, but a final quote will require the information below. We can help you determine this information if you do not have it already, so please don’t hesitate to contact us (314) 845-0077:

  • Feed vapor-liquid equilibrium
  • Column operating objectives
  • Operating pressure range
  • Minimum reflux ratio (R/Dmin)
  • Minimum number of ideal separation stages (Nmin)
  • Diameter and height of the column
  • Final mass & energy balances

EPIC follows a front end engineering (FEE) budgeting technique that develops system requirements, a detailed execution strategy, and an accurate budget with a realistic time-frame right from the beginning. FEE accounts for all costs and potential challenges to give you a highly accurate budget estimate that will allow you to properly plan for the entire distillation tower engineering process.

How long does the entire process take?

The process of designing, engineering and installing a distillation tower varies based on the specificity of each project. However, you can expect to see the following steps when going through the process with EPIC:

  1. Step 1: Create a basic design, budget and execution strategy
  2. Step 2: Completed advanced simulation & design (using Aspen Hysys software)
  3. Step 3: Begin building and assembling the customer tower, and developing any automation or controls
  4. Step 4: Full Factory Acceptance Testing & QA checks are completed
  5. Step 5: Shipping and Installation (if modular)
  6. Step 6: Startup, commissioning and employee training

Typical projects take 6-8 months from basic design to final startup, but that could vary widely depending on your project particulars. An off-site modular design can shave 3-4 months off the schedule for projects of appropriate sizes.

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EPIC Modular Process Systems
4134 Meramec Bottom Rd
St. Louis, MO 63129, US
(314) 845-0077

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