Liquid Distributor Selection Guide

There are two main categories of liquid distributors:

• Gravity distributors: These are capable of handling large liquid flow rates and have a high turndown ratio. Although efficient, they are sensitive to internal liquid hydraulics and contain a limited number of drip points, depending on the application and liquid load. They can be further divided into orifice plate distributors and trough–type distributors.
• Pressure distributors: Less expensive than gravity distributors, pressure distributors feature more room for vapor flow and require smaller lead-up piping. However, given that the quality of distribution is lower and there is a greater potential for corrosion, their operating costs prove ultimately higher than those of gravity distributors. Pressure distributors can be further divided into spray–nozzle and ladder-type distributors.

An orifice-type/pan liquid distributor — the most conventional type — allows gas to pass through the plate through risers while liquid flows through openings in the floor. The standard design has a turndown ratio of 2:1, and the pressure drop in water is typically 0.2 – 0.6 psi. If higher turndown ratios are required, taller risers can be used. This type of liquid distributor isn’t recommended for fouling applications.

Drip-tube liquid distributors are similar to orifice-pan liquid distributors, except that drip-tubes are used in place of some or all of the plate orifices. This modification allows drip-tube distributors to accommodate fouling applications. When used for fouling applications, the solids settle on the deck, and the liquid flows through the tubes. Turndown ratios of 10:1 are realistic.

Commonly used in stripper and scrubber services with moderate to high liquid rates, a ladder-type distributor or lateral pipe distributor can be used for a variety of applications, including conditions with limited space availability and high vapor velocities. It’s a pressure-driven liquid distributor in which the branch pipes serve to deliver the liquid through metering orifices. Generally, the pressure drop is 1-5 psi. Due to the potential for plugging of the orifices, a ladder-type distributor isn’t recommended for fouling systems — nor for systems with suspended solids or low liquid rates.

A spray nozzle distributor, or spray-type, can be designed for low liquid rates — sometimes as low as ½ GPM/ft² of tower area. Generally, the turndown is 2:1 at a pressure drop across nozzles of 10-15 psi. A spray nozzle distributor is predominantly used for refinery and heat transfer applications, and it’s important when short bed heights demand a uniform distribution pattern. They are not recommended for most distillation applications.

While you may need only one liquid distributor per tower, the type of liquid distributor will depend on the application.

MACH Engineering has more than 25 years of experience designing liquid distributors for a variety of industries that require liquid dispersion in packed towers. During our years in business, we have built a reputation for innovation and excellence, leading us to be one of the industry’s trusted leaders for many types of liquid distributors.

When you partner with us, we will work with you to determine the appropriate type of liquid distributor for your application. Once we have the exact specifications, we design your liquid distributor and run process simulations using Aspen Plus, both before and after selecting the tower internals. These simulations and designs optimize processes, navigate bottlenecks and improve treatment. Whenever you have an issue to resolve, our full-service company can guide you through the entire process and find an effective solution.

If your organization requires custom liquid distributors and tower internals that meet specific needs, we’re here to help. Please contact us online or call us at 346-202-3748 for more information.