Are you dealing with 4 ppm of H₂S, or trying to reach sub-ppm or even ppb levels?
If they are not removed properly, pipeline corrosion is just the beginning. LNG heat exchanger cracking, catalyst poisoning, and even full plant shutdowns are the real troubles.
Natural gas from different fields varies a lot in composition. But basically, they all contain H₂S, mercury, and organic sulfur. The question is not whether they exist, but how to remove them.
Quick Answer
For natural gas purification, pelletized impregnated activated carbon is widely used for H₂S and mercury removal.
- Alkali-impregnated carbon for H₂S removal
- Impregnated carbon for mercury control
- Pellet form ensures low pressure drop and high strength
If you already have gas data, you can skip to the design section or contact us for quick selection.
Pelletized impregnated activated carbon is nothing new in natural gas purification. But when it comes to H₂S and mercury removal, it is still one of the most commonly used core materials. The same type of carbon can make a difference of months in performance.
Xingsen activated carbon has two advantages:
- First, the pore structure is optimized for gas diffusion.
- Second, the impregnation chemicals are fully absorbed.
When H₂S and mercury enter the pores, they are adsorbed or react and stay there. Downstream heat exchangers and catalysts remain safe, and the operating cycle lasts longer.
Key Pollutants in Natural Gas Purification
Hydrogen Sulfide (H₂S)
In natural gas purification, hydrogen sulfide is a toxic and highly corrosive gas. Its concentration in natural gas varies widely, from trace amounts to several percent, depending on the gas field. It corrodes carbon steel, shortens equipment life, and poses serious health risks to operators.
Many pipeline and fuel specifications limit H₂S to very low ppm or even ppb levels. That’s why many projects now add an activated carbon bed after the main absorption tower to perform fine desulfurization.
If properly selected and designed, a pelletized impregnated activated carbon bed can serve as a reliable H₂S polishing unit downstream of bulk removal processes, ensuring that residual H₂S Stays below required specifications.
In practical engineering, pelletized impregnated activated carbon is commonly used as a fine desulfurization unit in natural gas purification systems.
Mercury
In natural gas purification systems, trace amounts of elemental and organic mercury are often found in natural gas, especially in gas fields with associated condensate and liquid hydrocarbons. Even at very low concentrations, mercury can cause cracking and catastrophic failure of aluminum heat exchangers in LNG plants, and can also damage catalysts and instruments.
Sulfur-impregnated activated carbon is widely used as a non-regenerable protective layer in natural gas purification to capture mercury before it reaches sensitive equipment.
With regular carbon, mercury might break through in two or three months. With sulfur-impregnated carbon, it can last for a year, and the outlet concentration can fall below 0.01 μg/m³.
In natural gas purification systems, pelletized impregnated activated carbon is one of the most commonly used materials for mercury control.
Other Impurities
Natural gas may also contain carbon dioxide, water vapor, heavy hydrocarbons, mercaptans, and other volatile organic compounds (VOCs). These affect heating value, corrosivity, and odor.
Amine units, glycol, or molecular sieves are usually used to remove CO₂ and water. Activated carbon is mainly used for polishing and removal of sulfides, mercury, and trace organics.
In many gas processing facilities, a well-designed activated carbon purification stage installed upstream of critical equipment can significantly improve reliability and reduce fouling caused by trace organic impurities.
The Role of Activated Carbon in Natural Gas Purification
Physical Adsorption on Pelletized Activated Carbon
In natural gas purification, pelletized activated carbon mainly removes pollutants through physical adsorption.
The cylindrical shape gives it a low pressure drop and high mechanical strength in fixed bed operation, which is critical for high-pressure natural gas systems.
When natural gas enters the activated carbon bed, the first step is that pollutants get trapped by the “pores.” The extruded pellets have many pores and a high surface area. Gas molecules go in and can’t get out. H₂S and VOCs are first captured by physical adsorption. The advantage of pellets is high strength and low dust generation. In high-pressure systems, the pressure drop stays stable even after a year of operation.
These pelletized activated carbon grades are widely used as guard beds to protect amine, glycol, and molecular sieve units, and to remove VOCs and organic sulfur from natural gas streams.
Chemical Adsorption with Impregnated Activated Carbon Grades
For deep removal of H₂S and mercury in natural gas purification, impregnated activated carbon is used to achieve high removal efficiency and long breakthrough time.
- For H₂S, alkali-impregnated activated carbon promotes the chemical reaction between H₂S and the impregnant, converting the gas into stable reaction products and increasing overall sulfur capacity.
- For mercury, sulfur-impregnated or metal-modified activated carbon forms stable HgS or other compounds on the carbon surface, significantly improving mercury uptake compared to untreated carbon.
By combining an optimized base carbon with the right impregnation chemicals, a single fixed bed of extruded and impregnated activated carbon can reliably protect downstream assets in natural gas purification plants over long operating cycles.
Pelletized impregnated activated carbon for natural gas purification
Typical Process Flow for Natural Gas Treatment with Activated Carbon
In natural gas purification systems, treatment with activated carbon typically follows this process:
1. Pretreatment
Raw gas is filtered to remove solid particles and often dehydrated using glycol or molecular sieves to reduce moisture. This protects the activated carbon bed from liquid water and excessive fouling, and prepares the gas for efficient H₂S and mercury removal.
The gas first goes through filtration and dehydration. This step can’t be skipped – too much water, and the carbon will absorb water instead of H₂S.
2. Fixed Bed Activated Carbon Reactor
Gas flows through one or more vertical fixed-bed vessels filled with pelletized or impregnated activated carbon. Bed design depends on flow rate, operating pressure, inlet pollutant concentration, and desired run length. For many plants, this activated carbon bed is the core step for removing H₂S and mercury in natural gas purification.
Gas passes through the bed, and H₂S and mercury are captured. How deep the bed should be and what gas velocity to use depends on the gas conditions and how long you want the bed to last.
3. Online Monitoring and Bed Switching
H₂S and mercury analyzers at the outlet monitor breakthrough. When the outlet concentration approaches the specified limit, flow is switched to a new or standby vessel, and the saturated bed is replaced or regenerated as needed. This method ensures stable and predictable natural gas purification performance.
Install online analyzers at the outlet to monitor H₂S and mercury. When the data starts to rise, it’s time to switch the vessel.
4. Disposal or Regeneration
Non-regenerable mercury beds are typically removed and disposed of as hazardous waste. Some H₂S polishing beds can be thermally regenerated depending on the impregnation type and process design. Proper disposal of sulfur and mercury-laden activated carbon is an important part of safe gas purification procedures.
Mercury-saturated carbon must be handled as hazardous waste. H₂S-saturated carbon can sometimes be regenerated; sometimes it’s one-time use – it depends on what impregnation chemical was used.
If you have specific gas conditions (flow rate, pressure, H₂S/mercury levels), we can help you select the right pelletized impregnated activated carbon and estimate bed size.
Pelletized and Impregnated Activated Carbon Grades for Natural Gas Purification
Pelletized Activated Carbon Pellets for Natural Gas Purification
Our pelletized activated carbon pellets are manufactured with high-quality raw materials and binders. They have high hardness, low dust, and a pore structure optimized for natural gas applications. They are suitable for:
- Guard beds upstream of the amine and glycol units
- Polishing VOCs and organic sulfur in natural gas
- Protecting downstream catalysts, membranes, and low-temperature equipment
Due to their high mechanical strength and stable pressure drop, these pelletized activated carbon grades are ideal for long-term operation in high-pressure natural gas purification systems.
Impregnated Activated Carbon for H₂S Removal
For deep H₂S removal, we offer alkali-impregnated activated carbon specifically designed for fixed-bed natural gas purification applications. These products combine high surface area with plenty of active sites, offering:
- High H₂S removal capacity at low outlet concentrations
- Stable performance under various gas flow rates and operating conditions
- Compatibility with typical natural gas humidity levels within specification limits
Using impregnated activated carbon for H₂S removal allows operators to meet strict sulfur requirements without major changes to existing process configurations.
Sulfur-Impregnated Activated Carbon for Mercury Removal
Xingsen’s sulfur-impregnated pelletized activated carbon is specifically designed for mercury removal from natural gas and associated gas. Sulfur is evenly distributed as a thin layer throughout the pore structure, achieving:
- Very high mercury uptake compared to non-impregnated activated carbon
- Outlet mercury levels are below strict environmental and equipment protection limits
- Excellent mechanical strength and low pressure drop in high-pressure vessels
For critical natural gas purification tasks in LNG and gas processing plants, sulfur-impregnated activated carbon beds are a reliable solution for long-term mercury control.
The following section is intended for engineers and technical teams involved in system design. If you are mainly looking for product selection, you can skip this part.
Key Points for Activated Carbon Bed Design
Pelletized impregnated activated carbon, with its high strength and low pressure drop, is well-suited for fixed-bed design in natural gas purification.
How you design the activated carbon bed directly affects how long it will last and how stable the performance will be. When we work with design institutes or engineering companies on projects, we usually consider the following dimensions.
What Data is Needed for Design
To calculate how big the bed should be and how much carbon is needed, you need these numbers:
- Gas parameters: flow rate, pressure, temperature
- Pollutant data: inlet H₂S and mercury concentrations, target outlet specifications
- Operating requirements: desired run length, available pressure drop
Send these to us, and we’ll help you calculate which carbon to use, how deep the bed should be, and how long it will run. No need to look up manuals for space velocity.
Bed Depth and Contact Time
How deep the bed should be is not decided by guessing.
If it’s too shallow, the gas passes through before being fully treated, and the outlet may exceed the limit. If it’s too deep, pressure drop is high and vessel costs go up, and the carbon might need to be replaced before it’s fully utilized.
We usually calculate based on gas residence time and mass transfer zone length, and add a safety margin – so if a high concentration spike comes in, it won’t break through the same day. Pelletized carbon has high strength and doesn’t generate dust, making it suitable for deep beds with stable flow distribution over long-term operation.
How to Control Pressure Drop
What’s the biggest concern in high-pressure systems? Pressure drop is rising too fast.
If you choose larger pellets, pressure drop is lower, but adsorption is slower, and bed utilization suffers. If you choose smaller pellets, adsorption is faster but pressure drop is higher, and it might not last until the end of the year.
Flow distribution also matters – if distribution is poor, local breakthrough happens early, and the whole bed needs replacement before it’s fully used. When we design, we balance these factors: pellet diameter, bed depth, flow distribution – to keep pressure drop stable and use the carbon efficiently.
How to Configure Vessels
For critical applications, running a single vessel alone is not recommended. If a breakthrough happens, there’s no room to switch.
Common configurations include:
- Two vessels in parallel: one in operation, one on standby. When vessel A breaks through, switch to vessel B without affecting production.
- Two vessels in series: the first vessel captures most pollutants, the second acts as a guard bed for final polishing. Suitable for applications with very strict requirements.
- Install online analyzers at the outlet to monitor H₂S and mercury. When the data starts to rise, it’s time to switch vessels.
Safety Considerations
Several things need to be considered during design:
- How to inert and vent during carbon change-out – avoid creating explosive mixtures
- H₂S and mercury reactions release heat. For high-load applications, evaluate hotspot risks
- Mercury-saturated carbon is hazardous waste. Disposal must comply with regulations
We go through these with the engineering team during the design phase, not after the equipment is installed and problems are found.
Need Help Calculating Your Bed?
Send us your gas conditions (flow rate, pressure, H₂S and mercury concentrations, target specifications), and we’ll help you with product recommendations and bed design. Contact our technical team
Engineering technical schematic diagram of activated carbon fixed-bed adsorber
Application Examples of Activated Carbon in Natural Gas Purification
The following examples show how pelletized impregnated activated carbon is used for H₂S and mercury control in real natural gas purification projects.
Case 1 — H₂S Polishing Upstream of a Gas Turbine
A gas-fired power plant received pipeline natural gas that still contained trace amounts of H₂S and organic sulfur. To protect a precision gas turbine and meet strict emission standards, the plant needed to further reduce sulfur content.
A fixed-bed reactor filled with alkali-impregnated pelletized activated carbon was installed upstream of the turbine as a final natural gas purification step. The reactor was designed to handle the plant’s maximum gas flow rate and was expected to run continuously for months between change-outs. Continuous monitoring of H₂S at the outlet confirmed that the polishing bed kept sulfur content well below the specified limit, improving turbine reliability and reducing maintenance downtime.
Case 2 — Mercury Removal at a Gas Processing Plant
A gas processing plant treating natural gas from a mercury-bearing field needed to protect downstream aluminum plate-fin heat exchangers and catalysts. Feed gas analysis showed low but non-negligible concentrations of elemental mercury.
The plant installed a dedicated mercury removal unit (MRU) using sulfur-impregnated pelletized activated carbon in vertical fixed bed reactors. Two reactors in series were used to maximize mercury capture and form a fine guard bed in the natural gas purification section. Throughout the operating cycle, outlet mercury levels remained below the detection limit of the installed analyzers, and no mercury-related damage was observed in the cold section. Spent carbon from the primary reactor was regularly replaced and disposed of as hazardous waste in accordance with environmental regulations.
Case 3 — Amine and Glycol Solvent Purification
An existing natural gas desulfurization plant using amine and glycol units experienced gradual solvent degradation and fouling due to trace hydrocarbons and their degradation products. This led to increased foaming, higher energy consumption, and more frequent equipment cleaning.
A pelletized activated carbon guard bed was added to the solvent circulation loop to adsorb high-boiling hydrocarbons and degradation byproducts. After implementation, solvent color and quality improved, foaming was significantly reduced, and solvent replacement intervals were extended. Plant operating costs decreased, and the performance of the amine and glycol systems became more stable, resulting in more consistent overall natural gas purification.
For engineers working on amine-based natural gas desulfurization plants, we also offer technical documentation on MDEA amine solvent filtration using activated carbon. You can download it here: Natural-gas-desulfurization-MEDA
Why Choose Our Pelletized and Impregnated Activated Carbon for Natural Gas Purification
Xingsen activated carbon combines high-quality pelletized activated carbon with advanced impregnation technology, designed to meet the demanding requirements of natural gas purification, H₂S removal, and mercury removal applications. We offer:
- Pelletized and impregnated activated carbon grades tailored to different natural gas purification needs
- Technical support for bed design, sizing, and optimization
- Reliable quality, mechanical strength, and long service life in fixed bed systems
If you are designing or upgrading a natural gas purification plant and need reliable activated carbon for H₂S and mercury removal, our pelletized and impregnated activated carbon products can meet your requirements. Contact our technical team for product selection, bed design support, and customized solutions for your specific natural gas purification project.
FAQ about Natural Gas Purification with Activated Carbon
What is activated carbon used for in natural gas purification?
Activated carbon is used to remove H₂S, mercury, and trace impurities to protect equipment and improve gas quality.
How does activated carbon remove H₂S?
Alkali-impregnated activated carbon reacts with H₂S and converts it into stable compounds for effective removal.
What carbon is used for mercury removal?
Impregnated activated carbon is commonly used to capture mercury and achieve very low outlet levels.
Where is activated carbon used in the system?
It is typically installed in fixed-bed reactors as a polishing step after primary treatment units.
How to choose the right activated carbon?
It depends on gas composition, flow rate, pressure, and required outlet specs. These data are needed for proper selection.
