KOH Regeneration

Veolia Water Build, Own & Operate the regeneration of KOH unit (on-site or off-site), and generate savings for his customer.

Depending on the fuel needs of a specific geography, refineries may include a process for increasing the Octane Rating of many of their refined fuel products. This process, referred to as Alkylation, is the reverse of catalytic cracking in that it makes small molecules (butylenes, propylene, iso-butane) into large ones: Alkylates. Alkylates have many positive features such as low vapor pressure, no sulfur, no olefins, no benzene and a high Octane number - a blender's dream.

Our clients require the use of a liquid acid catalyst in the alkylation process. The acid is either sulfuric (H2SO4) or hydrofluoric (HF). Both behave in very similar manners and both have severe safety consequences, if mishandled. When using HF, the acid catalyst is separated from the product after the reaction and returned to the reactor. However, the product still contains low concentrations of the HF acid which are removed by a caustic (KOH) wash. This generates a potassium fluoride (KF) waste stream in addition to some other impurities.

The main challenges are eliminating the waste stream requiring treatment prior to discharge and avoiding the cost of new caustic by recovering the spent KOH.

Veolia Water North America (VWNA) possesses a worldwide exclusive patent from DuPont for its High Aspect Ratio Draft Tube Agitated Crystallizer (HARDTAC®). This proprietary technology and process allows VWNA to recover KF alkylation's waste stream as useful by-products: KOH reusable for neutralization. In addition, the recovery process generates a pure by-product CaF2with a large crystal size, relative to the conventional crystallization process. VWNA produces a mean particle size of ~ 45µ compared to the conventional mean particle size of ~ 2µ.

The VWNA process offers the following performance benefits:

promotes growth on existing crystals
solids concentration 5 - 10 wt% (by weight)
high solids concentration recycle

Process overview

The KOH regeneration application of HARDTAC®involves collecting the feedstock KF material in tanks.

From the tanks, the KF is pumped into the HARDTAC®reactor where it is mixed and reacted with hydrated lime slurry according the following equation:
2KF + Ca(OH)2<-> CaF2+ 2 KOH
Conditions in the reactor are controlled (vessel turnover 6 - 8 times per minute) to maximize reagent usage and particle size.
From the HARDTAC®unit, the resultant KOH and calcium fluoride (CaF2) slurry is separated in a clarifier and filter press arrangement. Typical solids concentrations from dewatering are 75% to 80% by weight, allowing the recovery of 90% of the KOH value in the slurry solution.
The product KOH is collected in tanks, adjusted for concentration if required, and returned to our clients meeting our contractual obligations for concentration and recovery.

The benefits of this process include the recovery of 90% of the KOH value and therefore a large reduction in fresh KOH requirements. In addition, the KF stream from the Alkylation unit is handled as a feedstock in the HARDTAC®process and therefore is removed from the refinery's waste list. Lastly, eliminating the KF from the refinery's WWTP influent reduces concerns with toxic fluorides during wastewater treatment.

KOH Regeneration

Process overview

Case studies

At Laemchabang Industrial Estate - Thailand