48 Tons KOH Carbon for WWTP Biogas H₂S Removal

If you run an anaerobic digester and your gas engine supplier keeps warning you about H₂S, this is the media that solves it. Below is what we shipped, why this grade, and the field numbers behind it.

Shipment Summary

Why 2 Containers for 48 Tons

A 40HC is rated at 28,600 kg payload. But 48 tons of pelletized carbon at a bulk density of 0.45–0.55 g/cm³ hits the volume limit long before the weight limit — about 24 tons per container is the practical load for jumbo bags on pallets. So 48 tons ships as 2×40HC, not one. Anyone quoting you 48 tons in a single container is either mis-stating the packaging or shipping loose bulk.

Why Jumbo Bags for KOH Carbon

KOH is hygroscopic. It pulls moisture straight out of the air, and moisture taken up in a warehouse is capacity you no longer have in the vessel. That is the whole reason our jumbo bags carry a heat-sealed PE inner liner rather than a plain woven bag.

• Jumbo bags (FIBC) — one bag per vessel charge on most 600 L to 2 m³ systems, so the operator opens one liner and loads it. Less exposure than tipping twenty 25 kg sacks.
• Palletized and stretch-wrapped — pallets keep bags off the container floor away from condensation, and wrapping plus strapping stops shifting on a 30-day ocean leg.
• Keep bags sealed until load-in. This is the single most common field mistake we see. A bag opened and left standing for a week loses working capacity before it ever meets a gas stream.

For buyers comparing packaging options across grades, our packaging and storage guide covers 25 kg sacks versus FIBC and the moisture-barrier reasoning in more detail.

Field Performance: 500 m³/hr WWTP Biogas

This grade is in service on municipal digester gas. A representative installation at a plant treating 50,000 m³/day of sewage produces roughly 500 m³/hr of biogas carrying 2,000–4,500 ppm H₂S.

Two 600-litre vessels filled with 8% KOH-impregnated 4 mm pellets held the outlet below 5 ppm continuously for 14 months before the first media change-out.

What makes that number worth reading twice is what it replaced. The same operator previously ran a liquid scrubber, which meant daily chemical dosing, a dosing pump to maintain, and caustic to store and handle on site. Switching to a dry carbon bed cut total cost of ownership by 40% per year — not because the media is cheap, but because nobody has to touch it for a year at a time.

Recommended Product & Specifications

KOH Impregnated Activated Carbon — HojeeDesulf K-Series

Three of those lines do the real work in a digester-gas application:

1. H₂S working capacity 0.15–0.30 g/cm³ — this is the number that sets your change-out interval, and it is volumetric, so it maps directly onto vessel size. Capacity quoted per kilogram instead of per cubic centimetre tells you nothing about how long a fixed bed lasts.
2. Impregnation rate 8–15% — the WWTP case above runs the 8% grade. Higher loading buys more capacity but costs some base-carbon pore volume, so we match the rate to your inlet concentration rather than defaulting to the highest number.
3. Hardness > 90% — extruded pellets that crumble create fines, fines create pressure drop, and pressure drop shows up as a blower cost you did not budget for. This matters more on tall beds.

Bulk density also feeds straight back into logistics: at 0.45–0.55 g/cm³ your container is volume-limited, which is exactly why 48 tons became 2×40HC.

Where This Grade Fits

KOH-impregnated pellets are a chemisorption media, not a general-purpose adsorbent. They are the right call when:

• Digester and landfill gas — H₂S in the hundreds-to-thousands ppm range ahead of a CHP engine or upgrading skid.
• WWTP odour and pump-station ventilation — same chemistry, lower concentration, larger air volume.
• Acid-gas polishing — where an alkaline surface is needed rather than plain physical adsorption.

They are the wrong call for pure hydrocarbon or solvent capture, where you want unimpregnated carbon selected on CTC activity instead. The selection logic across both, including siloxane removal, is laid out in our biogas purification guide.

One point we state plainly because it affects your budget: KOH carbon is not regenerable. Once the impregnant reacts with H₂S it forms elemental sulfur and potassium salts that plug the pore structure, so thermal reactivation is neither practical nor economical. Spent media is replaced. That is normal for chemisorption desulfurization and it is why we design for maximum single-pass working capacity rather than selling you a regeneration story. If your stream is a candidate for reuse, reactivated carbon is a different conversation and a different product.

Working capacity on this grade is assessed against ASTM D6646, the standard test method for alkaline adsorptive capacity of activated carbon against H₂S. Ask any supplier which protocol their capacity figure comes from — if there is no method behind the number, the number is decoration.

Frequently Asked Questions

Related Reading

• Impregnated Activated Carbon Guide — how to pick the right impregnant
• 112 Tons Pellet Carbon Shipped to Norway for Biogas — larger KOH order, European delivery