CrystaSulf ®

CrystaSulf's patented technology, which utilizes a modified liquid-phase Claus reaction, provides a unique treating option for the medium-scale sulfur removal market (0.1 to 25 long tons per day - LTPD).  CrystaSulf provides a one-step, direct treatment of any gas stream containing hydrogen sulfide (H2S). Using a proprietary hydrocarbon-based solution, gaseous H2S is converted to solid elemental sulfur crystals, which may be used as a soil amendment for agricultural use, blended with other sulfur streams, or disposed as a low-volume non-hazardous waste. CrystaSulf avoids the chronic problems of plugging, foaming, and high chemical costs seen in conventional aqueous liquid redox and other water-based processes. CrystaSulf has eliminated sulfur solids in the main circulation loop, therefore providing reliable operation at high pressure. CrystaSulf easily handles gas contaminants such as heavy hydrocarbons, carbon dioxide (CO2), oxygen (O2), ammonia (NH3), and sulfur dioxide (SO2); has an excellent turndown ratio; and is able to easily follow fluctuations in the H2S load.  CrystaSulf is an especially good choice for streams with high CO2-to-H2S ratios since CO2 has no impact on the process.

Fields of Use

Applications well suited for CrystaSulf include the following:

  • Sour high-pressure natural gas (including shale gas);
  • Hydrogen recycle streams in refinery HDS units;
  • Refinery fuel gas;
  • Claus tail gas streams;
  • Gasification syngas;
  • Off-gas from heavy oil upgrading; and
  • Gas associated with in-situ oil sands operations.

Technology Overview

Recovering sulfur from gas streams that contain 0.2 to 25 LTPD of sulfur has historically been problematic.  In this size range, the operating costs of throw-away H2S scavenging chemicals are high, and traditional amine/Claus units are unwieldy with prohibitive capital cost.  CrystaSulf, a breakthrough sulfur recovery technology, can remove sulfur economically without the operating issues of aqueous-iron systems and with significantly lower pumping cost than regenerable caustic systems.

Using SO2 as an oxidant, CrystaSulf converts inlet H2S to elemental sulfur through a modified liquid-phase Claus reaction. Elemental sulfur is soluble in CrystaSulf solution which eliminates circulating solids in high-pressure equipment.  The sulfur is crystallized and separated from the process using equipment designed to handle solids, while the rest of the process remains solids-free.

Meeting pipeline H2S specifications of less than 4 ppmv is achievable at pressure above 150 psig, and CO2 has been shown to have no effect on the CrystaSulf process.

CrystaSulf Process Flow


Lower cost

  • Lower overall treatment cost, especially in high-CO2 applications
  • Lower maintenance and clean-out cost
  • Greater on-stream factor

Direct Treatment

Directly treat high-pressure streams

  • Solids-free solution is easy to pump
  • Low circulation rate

Nonaqueous solvent has high solubility for elemental sulfur

  • No sulfur settling additives or surfactants
  • No foaming and plugging problems associated with the aqueous systems

Common industrial equipment

  • Equipment does not require special design for slurry handling
  • No sulfur solids in circulating solution

Produces large sulfur particles

  • Sulfur handles, separates, and purifies easily
  • Drier sulfur means less disposal cost associated with water

Easy control of H2S removal

  • Solution has buffering capacity (changes happen slowly)
  • Easily monitored compound correlates directly with H2S removal

Compare with other processes for high-pressure applications.

Direct Treatment

Direct Treatment


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