Amine Plant 101 - How to optimize your existing infrastructure

Have you ever wondered if you’re getting the most out of your natural gas processing? Natural gas often contains impurities such as carbon dioxide (CO2) and hydrogen sulfide (H2S) that need to be removed before it can be used. An amine plant is a key part of this process which primarily involves the use of aqueous solutions of various alkanolamines, hence the name “amine plant.” At Q2 Technologies, we understand the fundamental need to treat large quantities of acid gases at scale, and we recognize that these amine plants can be challenged in getting full utilization rates on a consistent basis. That’s where our experts can assist in ensuring that H2S, mercaptans, and total Sulfur content is further optimized. 

 

Where are amine units found? 

Amine units are typically found at downstream locations such as Natural Gas Processing Plants, Fractionators, or at LNG facilities. However, amine headers can also be found further upstream at compressor stations.  

 

The Amine Plant 101 

Now that we have established what an amine plant is and where we can find it, let’s dive into how they work. We will go step by step using a gas processing plant as our main example:  

1. Gas Inlet 

Raw or untreated natural gas, which contains acid gases like CO2 and H2S, enters a facility via a pipeline. In its unprocessed state, the acid gas may contain other impurities, so oftentimes the amine plant is at the front end of these types of facilities. Again, being in a raw state, this gas stream is typically saturated with water vapor. 

2. Chemical Reaction 

In the absorption tower, the gas comes into contact with a solution of amine-based absorbent, commonly monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA). These amines selectively react with acidic gases, forming stable compounds and removing them from the gas stream. The acidic gases react with the amine solution to form soluble compounds, and because of this relation, choosing the right amine concentration is important. Due to the stoichiometric balancing during these reactions, the CO2 reaction, as it is the stronger acid of the two, the amine process is not 100% effective in stripping out all of the H2S, remaining CO2, and light mercaptans can pass unabated. In sum, amine units are moderately effective for H2S streams that have low CO2, but for weaker acids such as mercaptans, they are not a catchall and so a polisher system should be considered for final mercaptan adsorption. 

3. Sweet Gas Outlet 

The treated gas, now largely free of acidic gases, exits the top of the absorption tower as “sweet” or purified natural gas, ready for further processing or distribution. 

4. Regeneration 

The amine solution, now rich in absorbed acidic gases, flows to a regeneration unit. Here, heat is applied to release the absorbed gases. The regenerated amine solution, now depleted of acidic gases, is recycled back to the absorption tower for reuse. 

5. Recovery and Disposal 

The released acidic gases, along with any excess water vapor, are separated from the amine solution in the regeneration unit. These gases can be further processed or treated to meet environmental standards before disposal. 

amine plant process

Source: https://www.sciencedirect.com/topics/engineering/amine-system 

Here are the basic components of the Amine unit. Start with the Sour Gas and follow the arrows to Sweet Gas.

The Regenerator aspect of the unit is in a constant sequence of turning Rich Amine to Lean Amine. 

 

Additional considerations… 

 

Heat Integration: Many modern amine plants incorporate heat integration techniques to optimize energy efficiency. This involves exchanging heat between the hot regenerated amine solution and the incoming rich amine solution or between the hot gas stream and the reboiler. 

Monitoring and Control: Throughout the process, various parameters such as temperature, pressure, flow rates, and concentrations are continuously monitored and controlled to ensure efficient operation and adherence to safety and environmental regulations. 

Amine plants play a vital role in natural gas processing by removing the bulk of acid gases through the amine gas sweetening process, also known as natural gas sweetening process or sour gas sweetening, to meet product specifications, environmental regulations, and pipeline transmission requirements, but even with these steps, the resulting “sweet” streams may not be enough to meet commercial specifications. Remember that resulting mercaptan component after the stream had been treated? Unfortunately, mercaptans are challenging molecules to render, fortunately there are solutions. 

Q2 Technologies has developed a process that takes the resulting “sweet” stream and purifies it a step further. Our Pro3® Nano and our suite of mixed metal catalysts act as a next level polisher to ensure specs are met consistently. These robust units can take swings of H2S, mercaptans, and remaining Sulfur compounds in a combined reaction and absorption process. If your amine unit is at capacity, these polishers are excellent ways to scrub out any remaining Sulfur contaminants. 

With a better working framework of how an amine plant operates, we hope this helps explain how an amine unit works. If you have any questions or would like to learn how our advanced solutions can effectively remove H2S, mercaptans, and total Sulfur, please contact us. 


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