Biogas Purification

Iron Chelated H2S Scrubbing Technology

Our liquid redox solution for removing hydrogen sulphide from raw biogas, before CO₂ removal and compression into fuel-grade CBG.

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H2S Scrubbing Technology

Biogas Purification

Why Biogas Needs Purification

Raw biogas from an anaerobic digester is roughly 55–65% methane (CH₄), 35–45% carbon dioxide (CO₂), 100–10,000+ ppm hydrogen sulphide (H₂S), plus moisture, ammonia and trace inert gases. Before this raw gas can be compressed into fuel-grade CBG/Bio-CNG, H₂S must be scrubbed out.

H₂S is toxic and corrosive — it forms sulphuric acid with moisture and damages pipelines, compressors and engines. Under IS 16087:2025, GAIL India currently publishes an H₂S limit of 3.7 mg/m³ for CBG/bio-methane. This page covers our H₂S scrubbing solution; CO₂ removal is covered on our CO2 Removal Technology page.

Our Technology

Iron Chelated H2S Removal

The Iron Chelated Liquid Redox process removes H₂S through absorption and chemical oxidation. H₂S is absorbed into an iron-chelated solution, where ferric iron (Fe³⁺) oxidises sulphide to elemental sulphur while being reduced to ferrous iron (Fe²⁺). The solution is continuously regenerated using controlled oxidation, allowing the iron-chelated solution to be recirculated with low chemical make-up requirements.

Iron Chelated H2S scrubbing skid: raw biogas into the H2S Absorption Tower, scrubbing solution cycling through the Solution Recirculation Tank and Iron Chelated Regeneration Reactor, elemental sulphur to the Sulphur Collection Section, and purified biogas out

5.8

Chemical Consumption (Rs/Kg CBG)

4.25

Electricity Consumption (Rs/Kg CBG)

40–68

Sulphur Recovery (Kg/day)

Compact

Footprint — Requires Smaller Area

Indicative values based on defined design and operating conditions. Actual consumption varies with raw biogas flow, inlet H₂S concentration, operating pressure, CBG production, chemical cost and site conditions — ₹/kg CBG figures may vary depending on inlet gas parameters.

Our Iron Chelated H2S Removal Solution

Deep, Consistent Removal

Designed to achieve H₂S ≤3.7 mg/m³, subject to inlet gas conditions and operating parameters, in line with the values GAIL India currently publishes against IS 16087:2025.
Responsive to Feedstock Variability

The liquid redox process can respond rapidly to changes in H₂S loading, subject to system design and operating conditions.
Minimized Air Carry-Over

The regeneration system is designed to minimize N₂/O₂ carry-over into the product gas.
High Efficiency, Compact Footprint

A compact, skid-mounted design that requires limited space and electricity to operate.
Sulphur Recovery

Recovers 40–68 kg/day of elemental sulphur as a saleable by-product, giving the system an additional revenue stream. Indicative recovery is based on specified inlet H₂S loading and plant operating conditions; actual recovery varies with H₂S concentration, gas flow and operating hours.
Operational Simplicity

A largely chemical/mechanical process that's easy to automate, monitor and hand over to plant operators.

Process Flow

How Our Technology Works

Raw Biogas

H2S Absorption

Iron Chelated Reaction

Elemental Sulphur Formation

Solution Regeneration

Recycled Scrubbing Solution

The Iron Chemistry Cycle

Fe³⁺

Oxidises H2S

Fe²⁺

Reduced Form

↻

Regeneration

Fe³⁺

Recirculated

Continuous regeneration reduces chemical make-up requirements and enables stable operation.

Why Us

Why Bharat Bioenergy & Renewable

We design, build and operate CBG purification systems end-to-end — from digester integration through gas purification, compression and GAIL/CGD interface, backed by ongoing commissioning and O&M support.

CBG EPC & project execution

Biogas purification solutions

H2S removal

CO2 removal / membrane purification

Digester integration

Gas compression & CBG systems

GAIL/CGD interface support

Project commissioning & O&M support

Summary

Iron Chelated Technology, End to End

Iron Chelated Technology

Our H₂S scrubbing solution — a compact, high-efficiency system that recovers elemental sulphur, runs on low chemical and electricity consumption (5.8 Rs/kg CBG and 4.25 Rs/kg CBG respectively), and is designed to achieve H₂S ≤3.7 mg/m³ in line with the values GAIL India publishes against IS 16087:2025, subject to inlet gas conditions and operating parameters.
Bharat Bioenergy & Renewable

Delivers this technology end-to-end — from EPC and digester integration through to GAIL/CGD interface support and ongoing project commissioning & O&M.

Previous CO2 Removal Technology

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