Auxiliary Systems - Functions & KPIs
Four auxiliary systems in a depolymerisation plant — utilities, nitrogen skid, ETP (Effluent Treatment Plant), and vacuum skid — with the primary function and critical KPI that determines each system's operational health.
System | Primary Function | Critical KPI |
Utilities | Energy & Cooling supply | Downtime per 1000 hours |
Nitrogen Skid | Explosion prevention | O2 concentration (<1%) |
ETP | Water recycling | Chemical Oxygen Demand (COD) levels |
Vacuum Skid | Refining support | Absolute pressure (mbar) |
Beyond definitions
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How to read this table
- Each row is one auxiliary system; the columns show what it does and how to tell if it is working.
- Critical KPI is the single number that operators monitor in real time — if it drifts outside the target range, the main process must be adjusted or stopped.
- All four systems are mandatory — they are not optional efficiency upgrades but legally and operationally required infrastructure for a depolymerisation plant.
About this table
A depolymerisation plant cannot operate on its core reaction equipment alone — four auxiliary systems run in parallel to keep the main process running safely and within regulatory limits. These are not optional add-ons; each performs a function that, if it fails, will either shut down the plant or cause a regulatory breach. This table maps each auxiliary system to its primary function and the Key Performance Indicator (KPI) that tells operators whether it is working correctly.
The Utilities System — which includes the steam boiler, cooling tower, chiller, compressed air system, and electrical switchgear — is the energy and cooling backbone of the plant. Without reliable cooling, the distillation column cannot operate; without steam, the reactor cannot be heated to reaction temperature. The critical KPI is system downtime per 1,000 operating hours — a measure of utility reliability that directly determines plant availability and annual throughput. The Nitrogen Skid maintains an inert atmosphere inside the reactor and associated equipment to prevent explosive oxidation reactions. Molten polymer and organic solvents at elevated temperatures are flammable — even small oxygen leaks into the reaction zone create explosion risk. The critical KPI is oxygen concentration: the target is below 1% O₂ in all reactor and solvent handling areas. This is monitored continuously by fixed-point oxygen sensors.
The Effluent Treatment Plant (ETP) processes the process wastewater from washing and cooling operations before discharge or reuse. In a depolymerisation plant, this wastewater contains organic compounds (glycol carryover, solvent traces) that must be treated to meet SPCB discharge standards. The critical KPI is COD (Chemical Oxygen Demand) — the standard measure of organic contamination in industrial wastewater. The Vacuum Skid maintains the sub-atmospheric pressure required for vacuum distillation of the monomer purification column. Lower operating pressure means lower operating temperature, which protects thermally sensitive monomers from degradation during distillation. The critical KPI is absolute pressure in millibar — maintaining the target vacuum determines product quality and separation efficiency.
Key insights
- Nitrogen inerting (oxygen below 1%) is a safety requirement, not an efficiency preference — organic solvents at reaction temperatures are flammable, and an oxygen excursion in the reactor is a fire and explosion hazard.
- ETP COD compliance is a continuous SPCB obligation — a single exceedance creates a violation record that can affect consent renewal and EPR certification.
- Utility system downtime per 1,000 hours is the most predictive metric for annual plant throughput — a 2% downtime rate means 175 hours of lost production per year on a 24/7 plant.
- Vacuum skid performance directly determines monomer quality — if absolute pressure rises above target, the distillation column temperature must increase to compensate, risking thermal degradation of the product.
Methodology & sources
KPIs and system functions described are based on standard chemical plant auxiliary system design for depolymerisation plants as of 2024. Specific KPI target ranges depend on plant design, technology licensor specifications, and SPCB consent conditions for the specific plant location. Oxygen concentration limits for inerting are typically specified by the Petroleum and Explosives Safety Organisation (PESO) for hazardous area classification.
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