Pasadena refinery has initial success with on-site amine-purification system

The AmiPur system at the Crown Central Petroleum Corp. refinery sits with the caustic tank. The blue cylinder is the regenerant reservoir. The resin column sits behind the control panel (Fig. 1).

The Crown Central Petroleum Corp., Pasadena, Tex., refinery successfully commissioned an ion-exchange unit for its amine gas-treating plant in October.

The refinery's amine system absorbs hydrogen sulfide from sulfur-containing streams.

High heat-stable salt (HSS) concentrations in amine solution contribute to corrosion and foaming. High levels of HSSs increase the need for corrosion-related maintenance and filter replacements. Eventually, HSSs are removed by either discarding a portion of the amine or by an amine treatment, both expensive alternatives.

The new amine system, called AmiPur and supplied by Canadian-based company Eco-Tec Inc., continuously removes HSSs from amine solutions. AmiPur is based on Eco-Tec's patented Recoflo technology.

Ion-exchange process

Each operating cycle of Eco-Tec's ion-exchange process consists of amine loading, water wash, and caustic regeneration. AmiPur repeats this cycle every 15-20 min.

Lean-amine solution is pumped at high flow rates through a cartridge filter and into the resin column. Recoflo uses small columns packed with fine mesh ion-exchange resin. The ion-exchange resin removes the HSSs, and the purified amine solution is directed to the flash tank or returned to the amine batch.

Dilute caustic soda is used to regenerate the resin column. The unit draws concentrated caustic from customer-supplied tanks or drums and automatically dilutes it to the proper strength.

The AmiPur system is designed as a standard skid-mounted system and controlled by its own programmable logic controller (PLC). The skid-mounted system includes a resin column and regenerant reservoir. All components are pretested in the factory to facilitate installation and start-up.

Crown's unit was ordered in August and shipped and installed in mid-October. Installation, start-up, and commissioning took 5 days.

The AmiPur Model AM6, installed at Crown, has a footprint of 40 in. x 36 in. and continuously processes a 0.4 gpm slip stream. Fig. 1 shows the installation at the refinery.

Lower HSS and decreased corrosion

AmiPur continuously maintains the HSS concentration at the Crown Pasadena refinery below 2 wt %. At start-up, the new amine-purification system was removing 930-1,080 g/hr of HSSs from the lean amine, which contained 2.2-2.6 wt % HSSs.

Fig. 2 [36,889 bytes] shows the performance of the new system during the first month of operation. The percentage of HSSs in amines decreased from 2.4% at the beginning of the installation to 1.75%. After Nov. 23, the HSS concentration increased because high HSS material was brought into the unit to take advantage of the reclaiming operation.

Fig. 3 [38,628 bytes] shows the corrosion rate of a carbon-steel corrosion probe that was placed in the flow of the amine system. After 38 days on-line, the corrosion rate, which used to be about 30 mils/year (mpy), is about 10 mpy. A decrease in filter plugging has also been realized.

These results are preliminary because the unit has run for only 2 months.