English
Integrated DOC-DPF-SCR Exhaust Aftertreatment System for 5 MW Railway Power Generation
Created on Today
Integrated DOC-DPF-SCR Exhaust Aftertreatment System for 5 MW Railway Power Generation
Project Overview
Client | Confidential Railway Infrastructure & Power Supply Contractor |
Application | 5 MW Diesel Generator Set — Railway Station Backup Power |
Product | Custom-Engineered Integrated DOC + DPF + SCR System |
Location | Confidential Railway Project |
Commissioning | 2026 |
The Challenge
A major railway infrastructure project required a 5 MW diesel generator set to serve as the primary backup power source for a high-speed railway station complex. Operating at full load, the generator produces a substantial exhaust gas volume of approximately 45,000 m³/h with high concentrations of NOx, particulate matter (PM), and carbon monoxide (CO).
The project faced three critical constraints:
· Strict Emission Limits — The local environmental authority required the system to meet EU Stage V equivalent emission levels for stationary engines, demanding NOx reduction of ≥95%, PM filtration efficiency of ≥95%, and CO oxidation of ≥90%.
· Space Limitation — The equipment room allocated for exhaust treatment was only 12m × 6m × 4.5m, making it impossible to install three separate treatment units with conventional ducting transitions.
· Railway Operational Reliability — As backup power for signaling and station systems, the generator must start and reach full load within 15 seconds. The aftertreatment system could not introduce excessive backpressure that would compromise engine response or power output.
Our Solution
Our engineering team designed a fully integrated, skid-mounted DOC + DPF + SCR system packaged as a single compact unit. The system was engineered around the specific exhaust profile of the 5 MW engine, with computational fluid dynamics (CFD) optimization at every stage.
System Architecture
Engine Exhaust → DOC Module → DPF Module → SCR Module (with Urea Injection) → Stack
All three treatment stages are housed within a single 304 stainless steel enclosure mounted on a heavy-duty carbon steel skid, eliminating the need for intermediate ductwork and reducing the overall footprint by 40% compared to modular separate units.
Key Engineering Features
1. DOC (Diesel Oxidation Catalyst) Module
· High-cell-density metallic substrate with Pt-Pd washcoat
· Converts CO and HC to CO₂ and H₂O with ≥95% efficiency
· Raises exhaust gas temperature to support DPF regeneration and SCR light-off
2. DPF (Diesel Particulate Filter) Module
· Silicon carbide (SiC) wall-flow filter elements with ≥99% filtration efficiency
· Integrated compressed-air pulse cleaning system with 12 solenoid valves for active soot removal without shutdown
· Differential pressure monitoring for real-time soot loading status
3. SCR (Selective Catalytic Reduction) Module
· Vanadium-titanium catalyst optimized for 250–450°C operating window
· Multi-point urea injection grid with CFD-optimized mixing chamber
· Perforated stainless steel flow distributor ensuring uniform velocity distribution across the catalyst face — NH₃ slip < 10 ppm
4. Integrated Design Advantages
· Single skid footprint: 6.5m × 2.2m × 2.8m
· Flanged inlet/outlet: DN800, matching engine exhaust piping directly
· Bolted access doors on both DPF and SCR compartments for catalyst inspection and replacement
· All stainless steel wetted surfaces for corrosion resistance in outdoor/industrial environments
· Pre-wired sensor harnesses and junction box for plug-and-play commissioning
Technical Specifications
Parameter | Value |
Rated Engine Power | 5,000 kW |
Exhaust Gas Flow Rate | ~45,000 m³/h (at full load) |
Inlet Gas Temperature | 350–480 °C |
System Backpressure | ≤ 2.5 kPa (at full load, clean condition) |
NOx Reduction Efficiency | ≥ 95% |
PM Filtration Efficiency | ≥ 95% |
CO Conversion Efficiency | ≥ 90% |
NH₃ Slip | < 10 ppm |
Housing Material | SUS304 Stainless Steel |
Skid Material | Carbon Steel (epoxy painted) |
Overall Dimensions (L×W×H) | 6,500 × 2,200 × 2,800 mm |
Approximate Weight | ~8,500 kg |
Project Execution Timeline
Phase | Duration | Key Milestone |
Engineering & Design | 2 weeks | CFD simulation report & GA drawing approval |
Manufacturing | 4 weeks | Material procurement, fabrication, catalyst loading |
Factory Acceptance Test (FAT) | 1 week | Pressure test, leak test, functional test |
Shipping & Installation | 1 week | On-site positioning, ducting connection, wiring |
Commissioning | 1 week | Load bank test, emission verification, handover |
Total Lead Time | ~9 weeks |
Results & Performance
After commissioning, the system underwent a 72-hour full-load endurance test with continuous emission monitoring. The results exceeded the project's contractual requirements:
· NOx at stack: 180 mg/Nm³ (limit: 400 mg/Nm³) — 55% margin
· PM at stack: Below detection limit (< 5 mg/Nm³)
· CO at stack: 120 mg/Nm³ (limit: 500 mg/Nm³)
· Backpressure at full load: 2.1 kPa — well within the engine manufacturer's 3.0 kPa limit
· Generator start-to-full-load time: 12 seconds — no impact from aftertreatment system
· DPF regeneration interval: > 500 operating hours under typical load profile
"The integrated design saved us critical floor space in the equipment room, and the plug-and-play skid reduced our on-site installation time by nearly half. Emission test passed on the first attempt." — Client Project Manager
Why It Matters
This project demonstrates our capability to deliver custom-engineered, high-capacity exhaust aftertreatment solutions for demanding infrastructure applications. By integrating DOC, DPF, and SCR into a single skid-mounted unit, we achieved:
· Space savings of 40% vs. separate modular systems
· Lower installation cost through pre-assembled, pre-tested delivery
· Proven emission performance meeting the strictest stationary engine standards
· Operational reliability validated under real railway backup power conditions
Ready to discuss your exhaust treatment project? Contact our engineering team for a customized solution tailored to your engine specifications and emission requirements.
WhatsApp