Biogas Desulphurisation: Which Technology is Best for ...

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With the increasing need for sustainable energy, biogas has greatly gained interest in the last few years. Originating from the process of anaerobic fermentation, biogas can be used to numerous applications to reduce green house gas emissions and produce clean sustainable energy [1].

Biogas is typically composed of methane (CH4) and carbon dioxide (CO2), but also contains traces of additional gases, such as hydrogen sulphide (H₂S), ammonia (NH3), hydrogen (H2) and other impurities.

Due to its highly corrosive nature, H₂S needs to be stripped off with upgrading technologies in order to preserve expensive biogas processing equipment. Even with low H₂S concentration, metal corrosion will be slower, but will still occur due to the presence of carbon dioxide [2].

Source: Membrane Gas Separation Technologies for Biogas Upgrading, X. Chen
et al., 2015

Here is an introductory video on gas desulphurization from DMT, featuring their own solution: the Sulfurex®.

Selecting the Best Technology for your System

What are the factors for selecting technologies for H₂S removal? When it comes to evaluating a potential H₂S removal technology, you need to consider three important variables: your site’s conditions, the product gas requirements and the economics [4].

Sites Conditions

Every installation is different. Whether for inlet gas flow or operating parameters, your biogas facility has its own specific conditions. The amount of H₂S processed per day, temperature, pressure, oxygen concentration, carbon dioxyde and water content of your system should and will directly influence your decision.

Product Gas Requirements

According to the gas utility you are doing business with, each structure has unique pipeline injection specifications. What are the environmental air permitting regulations? How will SO₂ be released? Make sure to answer these questions before settling in on a solution.

Economical Benefits

Last but not least, economical benefits. How do I get the most of my investment? Ultimately, it comes down to CAPEX against OPEX tradeoff. A more expansive technology may require less operating and maintenance fees, whereas a cheaper solution could lead to bigger ongoing expenses.

Based on your site parameters, here is a table below to help you select an economical H₂S abatement technology for your application.

SCFM: Standard cubic feet per minute of biogas
ppmV H₂S : parts per million by volume of H₂S

Source: Michael Knapke, MK. (2022, September). Technologies for Hydrogen Sulfide Removal [Selection of a potential H2S Removal Technologies]. RNG Works 2022, Guild Associates.

As every single biogas upgrading installation requires an H₂S removal solution, there are a great number of technologies available on the market worldwide. Here you will find the best solutions from various BiogasWorld members.

Biogas Desulphurisation Systems Available on the Market

DMT’s Sulfurex® BR, CR & BF

DMT has developed a vast amount of biogas treatment technologies. For the key biogas contaminants, DMT can offer one or a combination of technologies to economically manage them. A technology selection is made by analyzing the mixture of contaminants, the gas flow, the pollution load and the application. By not pushing one technology, DMT can provide the customer with the best solution for that specific project.

The basic principle of the technologies DMT offers to desulfurize gas, is the absorption of H₂S to a liquid. An oxidation process converts the H₂S to elemental sulfur or sulfate. DMT offers a pure chemical process Sulfurex®CR (Chemical Reaction), a biological process Sulfurex®BF (Biotrickling Filter), and a biochemical process Sulfurex®BR (Biological Regeneration) with integrates a bioreactor for the biological regeneration of the solvent.

For more information Sulfurex® technologies, click here.

Benefits

• Flexible desulphurization technology
• Low hydrogen sulfide outlet concentrations
• Low operational expenses
• Suitable for high loads of sulfur
• Reduction in OPEX compensates the higher initial investment cost

Paques THIOPAQ® – Biogas desulfurization

Highly Efficient H2S Removal from biogas and landfill gas at high uptime enables industries to consistently meet stringent gas quality requirements.

The THIOPAQ® was developed by Paques, in cooperation with universities, research institutes and customers. It can be applied to a wide range of biogas streams containing H₂S and can be combined with all biological anaerobic systems. The ‘caustic’ solution in the THIOPAQ® scrubber is continuously biologically regenerated. In the scrubber, the gas containing
H₂S is brought into contact with the washing water in counter currently. Absorption of H₂S under slightly alkaline conditions (pH 8-9) enables a chemical reaction with hydroxide ions.

Through continuous development Paques is able to provide every customer with a tailor-made gas treatment solution that enables the customer to produce biogas with a very low hydrogen sulfide content at a low O&M cost and to fuel local gas-fired microgrids, or upgrade the gas to biomethane. Additionally, the elemental sulfur produced by the THIOPAQ® can be used as a high-quality fertilizer.

For more information on THIOPAQ® , click here.

Benefits

• Proven technology > 30 years operational experience
• > 325 THIOPAQ® references worldwide
• Continuous innovation
• In-house manufacturing and quality control
• Deep H₂S removal (to < 25 ppm)
• High uptime and reliable process
• Low total costs of ownership
• No air input in biogas
• Production of high-quality fertilizer
• No hazardous byproducts

Prodeval’s VALOPACK

After a first pretreatment process, the VALOPACK filtration unit is designed to extract pollutants (H₂S, siloxanes, VOCs) from Biogas before continuing with the upgrading process, using two activated carbon filter tanks.

There is also a 3 µm dust filter located after the activated carbon filters, preventing dust from spreading after load changes.

The type of activated carbon is chosen based on the concentration of each pollutant in the Biogas (dealing specifically with H₂S or VOCs).

For more information on VALOPACK, click here.

Benefits

• Lead-lag assembly: Possibility of reversing the direction of gas flow in the filters to improve the quantity of pollutants retained by the activated carbons and to optimize the loading rate
• Optimal filtration and continuous operation
• H₂S measurements between filters: Continuous monitoring of loading rates and anticipation of activated carbon renewal

Pyro Green-Gas Desulfurization System

Pyro Green-Gas offers two desulfurization processes. The Ferrachel II® Iron chelate process for high gas flows and high inlet hydrogen sulfide concentrations. Dry scrubbing catalyst for low inlet hydrogen sulfide concentrations. In cases where hydrogen sulfide concentrations of less than 100 ppmv are required, a dry scrubbing catalyst stage is required.

Pyro Green-Gas (previously Air Science Technologies) offers many desulfurization processes tailored to balance CAPEX and OPEX for specific gas flows and conditions. Broadly there is dry desulfurization; either via a catalytic redox reaction onto media or adsorption, and there is absorption where the gas contacts a curated absorbing liquor where chelated iron interacts with and removes hydrogen sulfide from the gas. The latter is particularly well suited for large flows and highly sour gas.

For more information Pyro Green-Gas desulfurization systems, click here.

Ferrachel II® Iron Chelate Process

The process operates continuously and only requires a periodical inspection and cleaning of some internal components to ensure optimum efficiency and performance.

For outlet requirements of less than 100 ppmv, the Iron Chelate desulfurization process can be followed by a dry desulfurization step which can bring hydrogen sulfide concentration down to ≤ 4 ppmv.

Dry Scrubbing Catalyst (DSC) Process

The process consists in passing the hydrogen sulfide charged gas through a tower filled with the required amount of active media for the required hydrogen sulfide outlet concentration over the design life of the media.

Generally, two towers are installed with inter connecting piping and valves to operate each tower in a lead or lag mode. This feature allows for the optimal use of the desulfurization media and minimizes the operating cost of the desulfurization process. 

UGN Gas Desulphurisation Systems – BEKOM H

The untreated, warm and humid biogas flows through the filter module that is filled with UgnCleanPellets®. The hydrogen sulphide is targeted and completely removed from the raw gas and transformed to elemental sulphur.

Atmospheric oxygen is fed in to allow the filtering material to self-regenerate, while the desulphurisation process is running at the same time. This ensures that the desulphurising capacity of the material is maintained for a long time. When the pellets reach their maximum take-up capacity, the hydrogen sulphide content in the clean gas increases gradually.

For more information on BEKOM H, click here.

Benefits

• Maximum efficiency due to conditioning
• No upstream gas cooling and drying necessary
• Low investment and running costs
• Minimum maintenance
• Reliability and high system availability
• Long service life of filter/filtering material
• Filter made of corrosion resistant material
• Very easy installation, effective immediately
• Carbon neutral filtering material

Veolia’s SULFOTHANE™

The Sulfothane™ process consists of two steps. First it resembles a chemical alkaline scrubber for H₂S . Second the alkaline solution is continuously regenerated in a biological process using aerobic sulphur bacteria.

Sulfothane™ uses a widely applied and well proven technology to treat gas streams containing up to 50,000 ppm H₂S . The scrubber column is operated in counter current mode, which results in very high removal efficiency of H₂S. Even lower than 25 ppm H₂S is possible, exceeding 99%. The process reduces the odour, toxicity and corrosiveness of the biogas, without dilution with air due to a strict separation of biogas and aeration steps.

For more information on SULFOTHANE™ , click here.

CHIDA supply professional and honest service.

See also:
Where to buy high-quality carbide bars?

Benefits

• Deep H₂S removal efficiency
• No addition of air (N2, CO2 and O2) to biogas stream, therefore very suitable for further biogas upgrading without changing clean biogas flow and composition
• Small footprint
• Most reliable and robust
  H₂S removal process, applicable to high turn down ratios and S-load fluctuations.
• Very fast and stable start-up procedure with small biomass inoculum
• Significant chemical savings (caustic, active carbon, iron ore) leading to much lower operating cost.
• No risk of clogging in the scrubber column

BGasTech’s BTS-MPdry

Biogas conditioning/cleaning technology (BTS-MPdry) from Biogas & Gases Technologies (BGasTech) is a range of technologies applied for biogas cleaning. It includes: the BTS-Siloxa technology for the removal of siloxanes and the BTS-Sulfure technology for the removal of H2S in biogas. Both are based on dry removal methods.

As a cleaning technology it is based on a combination of removal techniques and has two basic stages.

Stage 1: Coarse. Cooling-condensation.

Stage 2: Fine. Adsorption on activated carbon.

For this purpose, it has a set of interconnected equipment that allows the elimination of moisture content and siloxanes by physical means (thermal and adsorption), halogenated compounds and H2S, as well as reducing the gas temperature to permissible values for engine intake.

For more information on BTS-MPdry, click here.

Benefits

• Less space requirement it’s mounting
• Better removal of the condensates
• Less probability of tube freezing when working at low temperatures
• Better heat transfer coefficients
• Greater effectiveness in removing moisture and other contaminants

Koch BGPUR™

The BgPur system is a proven solution for biogas treatment from anaerobic digesters and landfill. The system reduces hydrogen sulfide (H₂S) concentrations and converts it to solid elemental sulfur for resale. The system uses a liquid chemical catalyst, compact gas/liquid contactor, and solids removal system and does not consume the chemical catalyst driving the conversion of H₂S to sulfur, minimizing chemical make-up requirements. As a result, operating costs are significantly lower than typical solid sorption processes and the system promotes a stable and predictable H₂S removal process.

For more information BGPUR™, click here.

Benefits

• Lower energy requirements
• Simple installation and operation
  
• Fully automated
• Scalable
• Consistent performance with over 99% H₂S removal
• Smaller footprint

Iron Oxides for H₂S Removal

UgnCleanPellets®

UGN Umwelttechnik Ltd offers a natural desulphurization adsorbent which is engineered and produced in Germany and already utilized in hundreds Biogas sites worldwide (reference in US available). The adsorbent UgnCleanPellets® is applied in external desulphurization processes and has the property making raw and fine purification process in one step. It is possible, reducing H₂S loads in one purification reactor from ~ 5000 ppm below < 5, depending on gas conditions, composition, and flow.

For more information on UgnCleanPellets®, click here.

Benefits

• Cost benefits – reasonable cheaper than activated carbon / other adsorbents
• Comfortable handling – less technical parts results in smooth desulphurization operation
• Low asset costs – no raw gas conditioning such as cooling / condensation required necessary
• Low operational costs – reduced pressure loss results in lower electricity demand
• Fewer emissions – replacing activated carbon by UgnCleanPellets® safes hundreds of tons of CO2 emissions
• Long operation period – same or even higher H₂S /Sulphur loading like activated carbon
• No waste – loaded material can be recycled in compost factory (depends on regional law)
• Valuable by-product – valuable fertilizer as waste product for fertilizer companies

AxTrap™ 4000 Series Sulfur Removal Adsorbents for Biogas

Axens offers the AxTrap™ 4000 Series of dry, granular media scavengers to safely and effectively remove these common sulfur contaminants. 

AxTrap™ 4000 Series products are based on patented, proprietary mixtures of iron oxides and/or mixed metal oxides – on an inert, inorganic carrier. The result is a particularly robust, granular material in which the metal oxide matrix provides a firmly bound active phase which is non-toxic, non-hazardous, non-pyrophoric and environmentally safe in both fresh and spent condition.

Benefits

• Exceptional Value – The lowest adsorbent price vs. sulfur trapping capacity on the market, delivering unbeatable value and saving you money.
• Simple – Fixed bed technology with no moving parts and extreme robustness to variable feed conditions. There is no simpler way to remove sulfur from process streams.
• Safe – Non-toxic, non-hazardous, non-pyrophoric and environmentally safe in both fresh and spent condition.
• Reliable – Consistent sulfur removal performance and short lead times means solutions are available where you need it, when you need it.

For more information on AxTrap™ 4000 Series, click here.

Promindsa’s MICRONOX BIOX

MICRONOX ON16 is a mixture of iron oxides-hydroxides and other functional oxides specially developed to be added directly into the fermentation reactor This product has been the object of extensive preliminary studies, with successful application in biogas plants. It reacts with hydrogen sulfide to generate iron sulfide and sulfur. Both elements are common components of fertilizers leading to improved properties.

Benefits

• It avoids toxicity and physical risks: MICRONOX ON16 is a product that is not harmful to people, equipment or the environment.
• Absence of risk of explosive mixtures: It makes the injection of oxygen unnecessary.
• It minimizes corrosion damage: It reduces equipment maintenance costs.
• Safe and clean handling: It can be added simply, without the need for complicated dosing systems.
• Cheaper and more efficient desulfurization: Not only is it an effective method of capturing H₂S, but it also improves reactor productivity.
• It improves compost characteristics: The use of MICRONOX ON 16 does not generate any toxic by-products, and produces iron sulfide and sulfur, which are components that improve the properties of fertilizers.

For more information on MICRONOX BIOX, click here.

Notes & Sources

[ ] Cong Xiao et al. (2017, December). Review of desulfurization process for biogas purification. School of Environmental Science and Engineering, Qilu University of Technology, Jinan, Shandong, China.
https://www.researchgate.net/publication/321897416_Review_of_desulfurization_process_for_biogas_purification

[ ] Ibid.

[ ] Daniel Waineo, DW. (2019, February). H2S Removal from Biogas for RNG and Electricity Projects [H2S Safety Issues]. American Biogas Council. https://americanbiogascouncil.org/wp-content/uploads/2019/03/H2S-removal.pdf

[ ] Michael Knapke, MK. (2022, September). Technologies for Hydrogen Sulfide Removal [Selection of a potential H2 S Removal Technologies]. RNG Works 2022, Guild Associates.

[5] Xiao Yuan Chan et al. (2015, February). Membrane gas separation technologies for biogas upgrading. Laval University and Ho Chi Minh City University of Technology and Education. https://www.researchgate.net/publication/272423302_Membrane_gas_separation_technologies_for_biogas_upgrading

[6] BGasTech (March, 2022). Desulfuration of Biogas. Biogas & Gases Technologies. https://bgastech.com/en/desulfuration-of-biogas/

[7] Joaquín Reina Hernández. (2022). Origin, Effect and Treatments. [Biogas cleaning. Hydrogen sulfide removal]. BGasTech.

[8] BioEnergy Consult (May, 2022). Methods for Hydrogen Sulphide Removal from Biogas. https://www.bioenergyconsult.com/hydrogen-sulphide-removal-from-biogas/

1. What are industrial non-hazardous secondary materials?

Industrial non-hazardous secondary materials (secondary materials) are any materials that are not the primary products from manufacturing and other industrial sectors. These materials can include scrap and residuals from production processes and products that have been recovered at the end of their useful life.

2. What is beneficial use?

Beneficial use (BU) involves the substitution of an industrial non-hazardous secondary material, either as is or following additional processing, for some or all of the virgin materials in a natural or commercial product in a way that: provides a functional benefit, meets product specifications, and does not pose concerns to human health or the environment. Examples include coal fly ash used as a replacement for portland cement in concrete, flue gas desulfurization gypsum as a substitute for mined gypsum in wallboard, and spent foundry sands used in soil-related applications, such as manufactured soil and road subbase.

3. How is the beneficial use of industrial non-hazardous secondary materials currently regulated?

In general, state environmental agencies manage the beneficial use of industrial non-hazardous secondary materials (secondary materials). Prior to beneficially using secondary materials in any projects, interested individuals or organizations should talk to the relevant state environmental agency to ensure proposed uses are consistent with state requirements. The Beneficial Use State Program Locatoris a useful tool to identify individual state rules and programs related to beneficial use of secondary materials.

For coal combustion residuals (CCR), the Agency’s April 2015 CCR Disposal Final Rule promulgated a definition for beneficial use (40 CFR 257.53). This definition identifies four criteria that distinguish beneficial use from disposal (21349 FR 80). Those parties who propose a beneficial use for CCR should consult both this definition and the relevant state authorities to identify all the requirements that would apply.

4. How does this BU Methodology relate to the unencapsulated framework mentioned in the April 2015 CCR Disposal Rule?

During the development of the framework to address the risks associated with the beneficial use of unencapsulated materials, the Agency determined that the principles outlined in the 2013 Methodology for Evaluating Encapsulated Beneficial Uses of Coal Combustion Residuals are also applicable and relevant to unencapsulated uses. Therefore, EPA combined the discussion of encapsulated and unencapsulated uses into a single document and renamed it the Methodology for Evaluating Beneficial Uses of Industrial Non-Hazardous Secondary Materials to reflect the broader scope.

In addition, EPA has completed the Beneficial Use Compendium: A Collection of Resources and Tools to Support Beneficial Use Evaluations (BU Compendium). The BU Compendium is a companion document to the BU Methodology. It provides a more detailed discussion of the specific considerations that may arise in particular evaluations, as well as a list of tools and other resources (e.g., existing fate and transport models or screening benchmarks) that might be relied upon in these evaluations.

5. How does the BU Methodology address unencapsulated uses?

The BU Methodology and BU Compendium are applicable to both encapsulated and unencapsulated beneficial uses of industrial non-hazardous secondary materials. EPA recognizes that there is a higher potential for certain types of releases and exposures from unencapsulated uses (e.g., windblown dust). Therefore, the Agency designed the BU Methodology to be inclusive to address releases, whether the source is from an encapsulated or unencapsulated beneficial use. EPA focused the discussion in these two documents on the considerations that will have the greatest impact in the design of the evaluation (e.g., the geographic area over which a beneficial use may be placed). Such considerations will determine the amount of data and the types of analyses required to adequately characterize a proposed encapsulated or unencapsulated beneficial use.

6. How does the BU Methodology relate to EPA’s previous encapsulated beneficial use methodology?

The BU Methodology builds on the principles first outlined in the 2013 Methodology for Evaluating Encapsulated Beneficial Uses of Coal Combustion Residuals. The BU Methodology provides further clarification on the analytical steps to ensure relevance for the widest range of industrial non-hazardous secondary materials used in both encapsulated and unencapsulated beneficial uses. The BU Methodology is divided into three phases: planning and scoping, impact analysis, and final characterization. Each beneficial use evaluation conducted using the BU Methodology will progress through these three phases, but there is flexibility in how each is applied.

7. How does this BU Methodology relate to the Agency’s Identification of Non-Hazardous Secondary Materials regulations?

EPA’s non-hazardous secondary material (NHSM) regulations, under the Resource Conservation and Recovery Act, identify which NHSMs are, or are not, solid wastes when burned in combustion units as ingredients or fuels. These regulations help combustion facilities in the determination of applicable emission standards for combustion units. Use of the Agency’s BU Methodology does not substitute for existing laws and regulations that address the combustion of solid wastes on either a federal or state level.

The BU Methodology presents EPA’s methodology for evaluating the potential for adverse impacts to human health and the environment associated with the beneficial use of a wide range of industrial non-hazardous secondary materials (secondary materials). However, the BU Methodology does not determine when these secondary materials are, or are not, solid wastes when beneficially used. Many states have beneficial use programs, and they should be consulted to determine whether a beneficial use of a secondary material is allowed and when the secondary material ceases to be a solid waste. The NHSM regulations should be consulted for solid waste determinations specific to use as fuels or ingredients in combustion units.

8. How can the BU Methodology and BU Compendium be helpful?

Together, the BU Methodology and BU Compendium are intended to help improve the consistency and quality of beneficial use evaluations. However, neither document is intended to be a detailed, step-by-step guide on how to conduct the evaluation for any particular beneficial use of an industrial non-hazardous secondary material (secondary material). Rather, these documents identify key questions to ask when designing or reviewing evaluations, as well as a list of tools and other resources that might be helpful. State environmental agencies oversee the beneficial use of secondary materials. These two documents can help states and others conduct beneficial use evaluations of secondary materials.

9. What conclusions can be drawn from an evaluation using the BU Methodology?

The Agency’s BU Methodology can be used to determine whether a beneficial use poses concerns to human health or the environment. What constitutes a concern will be defined by the risk management criteria that are built into the specific evaluation. These risk management criteria may incorporate a range of relevant risk-based, political, social, economic, legal, and technological considerations, but all criteria are based around an acceptable level of risk. Individuals and organizations who use the BU Methodology should coordinate with appropriate regulatory bodies to ensure that the risk management criteria incorporated into the evaluation are consistent with all applicable federal, state, and local government requirements.

10. What is EPA’s role in evaluating beneficial uses of industrial non-hazardous secondary materials? Who is responsible for conducting evaluations of other secondary material beneficial uses?

EPA has completed evaluations of coal fly ash used as a replacement for portland cement in concrete, flue gas desulfurization (FGD) gypsum used as a replacement for mined gypsum in wallboard, and silica-based spent foundry sands used in soil-related applications. EPA currently has an evaluation underway assessing the use of FGD gypsum as an agricultural amendment. Once this evaluation is completed, EPA has no further plans to evaluate additional beneficial uses of industrial non-hazardous secondary materials.

EPA is making the BU Methodology available to assist others with the design and review of beneficial use evaluations. Individuals or organizations who use the BU Methodology to conduct beneficial use evaluations should consult with the relevant states to determine whether the planned application of the BU Methodology is consistent with all applicable state requirements. EPA has no role in reviewing or approving the evaluations conducted by others, but can assist with questions about how to apply the BU Methodology in a manner that is consistent with existing Agency regulations and guidance.

11. Will evaluations of the beneficial use of industrial non-hazardous secondary materials conducted by organizations other than EPA be available to the public?

EPA encourages any individuals or organizations that use the BU Methodology to make their assessments publicly available. Thorough and transparent documentation of all the data, assumptions, analyses, and interpretations incorporated into the evaluation will provide greater confidence in the conclusions and better inform the regulators who will ultimately decide whether to allow a proposed beneficial use.

For more information, please visit Desulfurizer.