Northshore GCD2673: Synergistic inhibition in styrene distillation

The complex operated a four-column styrene distillation train fed with approximately 15.5 m³/h of dehydrogenation liquid. Its existing program used a commercial retarder alone, with a target residual of about 1,400 ppm in the primary-column bottoms.

In 2018, the unit consumed 878 tonnes of retarder at a reported cost of RMB 16.6 million. The plant wanted to reduce chemical expenditure while maintaining polymerization control, operating stability and styrene quality.

Cestoil proposed combining the polymerization inhibitor Northshore GCD2673 with the plant’s incumbent retarder. The trial retained the retarder as part of the protection program while evaluating whether GCD2673 could support a lower retarder residual.

Following technical reviews with Cestoil and the retarder supplier, the plant’s research department and olefins unit developed a stepwise trial. The team checked bottoms gum and polymer, retarder residual, column conditions, tar and product quality daily before making further adjustments.

The trial ran from 28 June to 28 July 2019. GCD2673 entered the primary-column feed line through an existing closed sampling loop; the retarder continued at its usual injection point near the column top.

Retarder reductions took place between 1 and 19 July, with each step held for two to four days and checked by daily bottoms analysis. GCD2673 feed dose and retarder concentration in column bottoms are different measurements.

At the approximately 150 ppm GCD2673 setting, the reported injection rate was 35 mL/min, equivalent to approximately 2.1 kg/h in the plant report. Total use over the 31-day trial was approximately 1.7 tonnes of GCD2673 and 60.7 tonnes of retarder.

The plant judged the inhibition achieved with GCD2673 at approximately 150 ppm and retarder residual in the 800–1,000 ppm range to be equivalent to its prior retarder-only program at 1,400 ppm. Measured retarder residual moved from approximately 1,340 ppm toward 900 ppm, with a reported minimum of 792 ppm on 19 July.

The approximately 35% reduction refers to measured gum, a fouling precursor. The report does not quantify a corresponding percentage reduction in equipment fouling.

The plant reported an estimated net chemical-cost saving of approximately RMB 250,000 per month, after accounting for GCD2673 cost.

Retarder use during the trial was 60.7 tonnes, compared with a 2018 monthly average of approximately 73.2 tonnes — about 17% lower. This trial total included the initial baseline and step-down period. The 36% headline reduction describes the column-bottoms retarder target, rather than the reduction in monthly retarder consumption.

The monthly saving is the plant’s estimate; the supplied case summary does not provide a complete cost reconciliation. Feed quality, operating conditions, chemical prices and the final treatment program affect the economics of another application.

This trial combined product performance with technical service: introducing the inhibitor before lowering the retarder target, reviewing daily laboratory results and holding each adjustment long enough for the plant team to assess operating response.

A comparable evaluation should define sampling methods and baselines, review the inhibitor–retarder combination and establish site-specific operating and protection requirements with the plant’s technical team before adjusting treatment.