High PDS Catalyst Consumption in Wet Desulfurization Causes & Catalyst Selection

High PDS consumption is not just a chemical cost problem. In coke oven gas desulfurization, it often appears together with unstable H₂S removal, weak regeneration, thin sulfur foam, high suspended sulfur or rising tower pressure drop.

Operating conditions should be checked first. But if the wet desulfurization loop is running within its normal range and PDS make-up remains high, the catalyst itself deserves a closer look.

Catalytic activity, active-component content and product consistency can all affect how much fresh material is needed to keep the unit stable.

When High PDS Consumption Is a Process Problem

Before changing catalyst, check whether the sulfur duty has changed.

Higher gas flow or inlet H₂S means more sulfur entering the unit. The catalyst requirement should therefore be considered against the actual H₂S load rather than kilograms added per day.

Regeneration is another common cause.

Low or unstable aeration can leave the circulating solution under-regenerated. Excessive air can create different problems, including poor sulfur flotation and unwanted oxidation.

The liquor also needs to stay within the proper operating window. HONREL specifies pH 8–9, regeneration efficiency ≥80%, suspended sulfur ≤1.5 g/L and by-salts ≤250 g/L for the listed PDS-HY process conditions.

If these values are already off target, simply changing PDS may not solve the problem.

When the PDS Catalyst Should Be Checked

The situation is different when the process remains reasonably stable but fresh catalyst demand keeps increasing.

This is where catalyst quality becomes important.

Two products sold as “PDS catalyst” do not necessarily provide the same catalytic input.

HONREL PDS-HY is available in three grades:

Especificación	Superior	First-Class	Calificado
Catalytic activity	≥0.040 min⁻¹	≥0.030 min⁻¹	≥0.020 min⁻¹
Cobalt content	≥3.0%	≥2.70%	≥2.50%
Active component	≥70.0%	≥65.0%	≥60.0%
Insoluble substance	≤5.0%	≤8.0%	≤10.0%

These are meaningful differences.

If one material has lower catalytic activity or less active component, comparing it with another product only by dosage or purchase price gives an incomplete picture.

For plants trying to reduce PDS make-up, start with the specification of the material currently being dosed.

Do Not Judge PDS by Concentration Alone

A laboratory result showing the expected PDS concentration does not always mean the circulating solution has the expected catalytic performance.

The grade matters.

So do solution contamination, HS⁻ loading and the condition of the circulating liquor.

This becomes particularly relevant when a plant changes PDS suppliers and then sees higher daily make-up, unstable H₂S outlet or poorer sulfur flotation.

Compare the old and new material by:

catalytic activity → active component → cobalt content → insoluble matter

not simply:

kg of PDS added

For replacement sourcing, HONREL can compare an existing PDS specification with its available PDS-HY grades.

Sulfur Foam Can Reveal a Catalyst Problem

Good H₂S removal is only part of the job.

The sulfur formed during wet oxidation must produce particles that can be separated from the circulating liquor.

Poor sulfur formation can result in thin foam, high water carryover and more suspended sulfur returning to the system. This increases the load on sulfur recovery and can contribute to deposits elsewhere in the loop.

HONREL PDS-HY is designed to promote relatively large sulfur particles for easier separation and lower suspended sulfur.

This matters in coke oven gas plants where poor sulfur flotation can eventually show up as higher tower resistance and more frequent cleaning.

If a replacement catalyst maintains H₂S removal but makes sulfur handling worse, it has not solved the plant problem.

High Tower Resistance May Point Back to the Desulfurization Liquor

Rising tower differential pressure is often treated as an equipment issue.

In PDS wet desulfurization, chemistry can be part of the cause.

High suspended sulfur can deposit in packing and mist-elimination sections. High by-salts can also contribute to deposits and unstable liquor conditions.

HONREL PDS-HY is formulated to reduce suspended sulfur and inhibit sulfur blockage, helping keep the circulating system cleaner.

So when evaluating a replacement PDS catalyst, look beyond H₂S removal.

Catalyst make-up, sulfur flotation, suspended sulfur and tower ΔP are all useful plant indicators.

Match PDS Grade to the Actual Sulfur Load

Not every plant needs to purchase catalyst on the same specification.

A stable unit with moderate sulfur duty and a coke oven gas plant dealing with high or fluctuating H₂S are different service conditions.

HONREL offers three PDS-HY grades with different specified catalytic activities and active-component contents. This allows the material to be selected against the actual desulfurization requirement rather than treating every PDS purchase as the same commodity.

For the listed coke oven gas and semi-water gas duties, HONREL specifies a PDS-HY concentration of ≥30 ppm.

The product is soluble in ammonia water and alkaline solutions and can be used with both ammonia-based and sodium-carbonate wet desulfurization systems.

The complete specification is available on the HONREL PDS-HY Phthalocyanine Cobalt Desulfurization Catalyst Página del producto.

Replacing a PDS Catalyst with HONREL PDS-HY

If your current PDS make-up is high, HONREL does not need only the quantity you want to buy.

Existing operating data can help determine whether the issue is related to sulfur load, process conditions or the catalyst currently in use.

The most useful information is:

Existing Plant Data	Why It Matters
Current PDS specification	Allows product comparison
Daily PDS make-up	Shows actual consumption
Gas flow	Defines treatment load
Inlet/outlet H₂S	Shows sulfur duty and removal performance
pH de la solución	Checks liquor condition
Regeneration air	Checks oxidation conditions
Suspended sulfur	Shows sulfur separation
By-salts	Shows liquor condition

If available, send the current catalyst datasheet as well.

HONREL can compare the existing specification with the available PDS-HY grades and recommend a suitable supply specification for further plant evaluation.

PDS-HY Supply for Coke Oven Gas Desulfurization

HONREL supplies phthalocyanine cobalt desulfurization catalyst for coke oven gas, semi-water gas, synthesis gas and other industrial wet oxidation systems.

PDS-HY provides specified catalytic activity up to ≥0.040 min⁻¹, cobalt content up to ≥3.0% and active-component content up to ≥70.0%, depending on grade.

For plants dealing with high catalyst consumption, unstable H₂S removal or poor sulfur separation, the first step is to compare the current PDS specification and operating conditions.

Send HONREL your current catalyst datasheet and recent operating data for a replacement review.

You can also explore other HONREL catalizadores industriales or browse the full product range for related chemical raw materials.

For current PDS-HY pricing, replacement supply or bulk requirements, contact HONREL with the required quantity and destination.

Preguntas frecuentes

Can changing PDS catalyst reduce make-up consumption?

It can when high consumption is related to catalyst activity, active-component content or product consistency. If the main cause is poor regeneration, incorrect pH or excessive sulfur loading, those process conditions also need to be corrected.

What should I compare when replacing my current PDS catalyst?

Compare catalytic activity, cobalt content, active-component content and insoluble matter. Current PDS consumption and H₂S performance are also useful when reviewing an alternative.

Which HONREL PDS-HY grade has the highest catalytic activity?

The Superior grade is specified at ≥0.040 min⁻¹, with cobalt content ≥3.0% and active component ≥70.0%.

Is HONREL PDS-HY suitable for coke oven gas?

Yes. Coke oven gas desulfurization is one of the specified uses, with operating conditions provided for PDS concentration, pH, absorption, regeneration and liquid-to-gas ratio.

Can HONREL replace the PDS catalyst we currently use?

HONREL can compare your existing product specification and operating requirements against its PDS-HY grades. Send the current datasheet, consumption data and basic desulfurization conditions for review.

What should I send when requesting PDS-HY?

For a straightforward purchase, send the required grade, quantity and destination. If the goal is to replace an existing PDS because consumption is high, also send the current catalyst specification, daily make-up and inlet/outlet H₂S data.