Amine Scrubbing System Overview

July 23rd, 2021

In the oil and gas industry, amine scrubbing is a necessary process. It is used in natural gas processing plants to ensure the quality of the gas before selling or further processing.

We will also have a look at amine scrubbing pumps and how to select the right one.

Amine Pump

In this article, we’re going to have an overview of the amine scrubbing system:

  • What amine scrubbing is
  • Why it is important
  • Which amines are used in gas sweetening
  • The amine scrubbing system

What is Amine Scrubbing?

Amine Scrubbing

Amine scrubbing, also called amine gas treating, gas sweetening, or acid gas removal, is the process of removing hydrogen sulfide (H2S) or carbon dioxide (CO 2) from gasses. 

The gas starts the process as “sour gas” and exits as “sweet gas.” It is called “sweetening” since the odor of the gas is improved without the presence of H2S.

Why Carbon Dioxide and Hydrogen Sulfide Needs to Be Removed From Natural Gas

Natural gas is “sour,” meaning it contains high levels of H2S or CO 2. These chemical compounds must be removed from the gas before the gas can be sold.

That is why even though hydrogen sulfide and carbon dioxide removal can cost significant amounts, it is an essential step in natural gas processing.

What are Amines?

In natural gas processing, an “amine” is an aqueous solution containing several alkylamines.

A variety of amines are used in the sweetening of acid gases. Which amine solution is used depends on several factors.

The most common amine aqueous solutions include:

Diethanolamine (DEA)
Monoethanolamine (MEA)
Methyldiethanolamine (MDEA)
Diisopropanolamine (DIPA)
Aminoethoxyethanol (Diglycolamine) (DGA)

These liquid amines come together with the sour gas and absorb the H2S and CO 2 in them.

Amine Scrubbing System

In order to get rid of the H2S and CO 2 in gas and prepare it for sale or further processing, the gas must go through the amine scrubbing system.

Most amine scrubbing systems have two essential processes: absorption and stripping.

Let’s have a closer look at each one.

Absorption

Before the gas can go through the amine scrubbing process, all solids and liquids must be removed first. That is why the first step is for the sour gas to go through an inlet separator which eliminates both of these using baffles and mist extractors.

From there, the gas then enters into the primary separator.

The most common design for the main separator is the contactor column.

In this design, the column is separated by trays. Bubble caps on these trays allow gas to rise from tray to tray without the dropping of the liquid. These columns also contain weirs on the sides to allow the fluids to flow downwards through the trays.

You may see how this system works in this video:

The sour gas enters the column through an inlet at the bottom, while the liquid amine solution enters from the top.

The inlet gas rises through the bubble caps and makes contact with the amines on the trays. This is when the H2S and CO 2 capture happens. As the gas stream moves upwards through the trays, more and more of the excess carbon dioxide and hydrogen sulfide are caught in the amines.

By the time the gas gets to the top of the column, it goes through a mist extractor to remove any liquids. It is now sweet gas and is ready for sale or further processing.

It is important to note that the pressure within the column must be high, while the temperature is kept low. Low pressure and high temperature may increase the flow rate of the amines, making them less efficient for H2S and CO 2 capture.

As the gas enters from the bottom of the column, lean amine is pumped into the column from the top. These flow over the bubble caps, capture the H2S and CO 2 and then flow downwards to the next trays until they reach the bottom.

Here, the now rich amine is pumped towards the stripping column, where it is treated before being pumped back into the separator column as lean amine.

Stripping

Once the amine leaves the separator column, it is rich with absorbed acid gases. This rich solvent is then pumped into a stripping column, where the H2S and CO 2 are stripped, and the amine can flow back into the separator column.

Advanced technologies like this are timely solutions to cut capital costs for gas processing plants. In this type of system, the amines never leave the system. They simply flow back and forth between the absorption column and the stripping column.

The temperature is kept high inside the stripping column. This helps to separate the carbon dioxide and hydrogen sulfides from the liquid amines.

In the stripping column, vapors (H2S and CO 2) rise to the top, pass through a condenser and are released as flue gas.

Meanwhile, the liquid amine flows to the bottom of the column, where it is transferred to a reboiler. The reboiler removes any remaining H2S and CO 2 from the liquid before it is finally pumped back into the separator column.

Amine Scrubbing Pumps

One of the most vital components in the amine scrubbing system is the amine pump. Since amine scrubbing happens in a closed-loop system, centrifugal circulating pumps are the right choice for this operation.

How to Choose an Amine Scrubbing Pump

Because of the high pressure within the amine scrubbing system, a high-pressure multistage ring section pump is perhaps one of the best types of pumps for the job.

With the high pressures these pumps provide, the number of trays inside the column separator can be reduced while still maintaining the same total head required. A pump like this can provide energy-efficient solutions, cut costs, and reduce footprint.

Getting a pump from a manufacturer that is known for its quality is also critical. The cost of maintenance and repair can rack up. That is why selecting a low-quality pump to cut costs can cost you more in the long run.

A pump from a reliable manufacturer ensures that the entire process is effective, has low energy consumption, and can run for extended time periods without constant repairs.

Carver Pump RS – The Best Amine Solution Pump

Your best option for pumping amine solutions is the Carver Pump RS.

RS

This multistage, ring-section pump can pump flows up to 2,000 US GPM, and heads up to 3,400 ft.

With it, the footprint in your chemical engineering, gas processing, or power plants will be far less. Plus, the interstage diffusers minimize radical loads for longer seal and bearing life while carefully controlling fluid flow for smooth and quiet operation.

You may learn more about the RS here, or download its brochure here.

RS Chart

About Carver Pump

The RS is manufactured by Carver Pump, a leading company known for its high-quality centrifugal pumps.

Certified by Intertek to conform to ISO 9001:2015, all Carver Pump pumps are guaranteed to meet the highest engineering standards in the world.

Based in Muscatine, Iowa, all Carver Pump pumps are proudly American-made. Carver Pump provides world-class pumps, R&D, customer service, and continuous improvement in everything they do.

When it comes to robust technology, nobody does it better than Carver Pump. That is why for all your oil and gas applications, trust only Carver Pump!

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