In the international transboundary trade of waste-derived commodities, a strict boundary exists between commercial Refuse-Derived Fuel (RDF) and Solid Recovered Fuel (SRF). While RDF remains a broadly defined, largely localized waste fraction, SRF is a highly standardized alternative fuel governed by international compliance protocols.
For engineering, procurement, and construction (EPC) contractors, municipal solid waste (MSW) asset managers, and cement plant co-processing directors, compliance with European Standard EN 15359 (now integrated into ISO 21640) is the baseline requirement for market acceptance.
EN 15359 establishes a strict classification system that transforms processed solid waste into a predictable, tradeable energy commodity. This technical whitepaper analyzes the 3-tier classification matrix of EN 15359 and details the mechanical processing infrastructure required to meet high-tier specifications consistently.
1. The EN 15359 Classification Matrix Defined
The EN 15359 standard classifies SRF using a three-digit classification code. Each digit represents a specific class performance tier (from Class 1, the highest premium tier, to Class 5, the lowest acceptable tier) across three critical fuel vectors: Economic, Technical, and Environmental.
[EN 15359 Classification Code: E - T - Env]
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┌────────────────┼────────────────┐
▼ ▼ ▼
1st Digit: 2nd Digit: 3rd Digit:
Net Calorific Chlorine Content Mercury Content
Value (NCV) (Cl) (Hg)
[Economic Base] [Technical Risk] [Environmental Base]
The 1st Digit: Net Calorific Value () — The Economic Parameter
The economic tier is determined by the mean Net Calorific Value on an as-received basis (). It dictates the direct substitution rate of fossil fuels (coal or petroleum coke) within the calciner or boiler.
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Requirement: Class 1 compliance requires an (), whereas Class 3 mandates .
The 2nd Digit: Chlorine Content () — The Technical Parameter
Chlorine is the most critical technical constraint in co-processing. At high temperatures inside cement kilns or waste-to-energy boilers, chlorine volatilizes and forms volatile alkali chlorides (, ), causing severe high-temperature corrosion on heat exchanger tubes and causing preheater cyclone blockages due to material sticking.
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Requirement: The value is calculated as the arithmetic mean on a dry basis (). Class 1 enforces a strict threshold of , while Class 3 allows up to .
The 3rd Digit: Mercury Content () — The Environmental Parameter
Mercury is highly volatile and cannot be easily captured by standard alkaline flue gas cleaning systems (such as semi-dry scrubbers). Control must happen at the feedstock stage.
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Requirement: Unlike and , which rely on mean values, EN 15359 determines the mercury class using both the median value and the 80th percentile value. This statistical approach accounts for sudden mercury spikes in the waste stream. Class 1 restricts mercury to , while Class 3 permits .
2. EN 15359 Limit Value Specifications
The table below outlines the formal threshold metrics defined by the EN 15359 standard framework.
| Classification Code / Digit | Property 1: (Mean, As-Received) | Property 2: Chlorine (Mean, Dry Basis) | Property 3: Mercury (Median / 80th Percentile) |
|---|---|---|---|
| Class 1 | |||
| Class 2 | |||
| Class 3 | |||
| Class 4 | |||
| Class 5 |
Commercial Example: An alternative fuel labeled as SRF Class 3-2-2 indicates a fuel with an , Total Chlorine , and an 80th percentile Mercury level .
3. Mechanical Feedstock Engineering for High-Tier SRF Production
To upgrade unsegregated municipal solid waste or industrial fractions into a premium EN 15359 compliant fuel, processing facilities must systematically isolate specific material streams.
[Raw Pre-Sorted Waste Input]
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├──► High-Gradient Air Classification ──► Discharges High-Ash Inerts (Lowers Hg Risk)
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├──► Near-Infrared (NIR) Spectroscopy ──► Ejects PVC Fractions (Downshifts Cl to Class 1/2)
│
└──► Multi-Stage Secondary Sizing ──► Produces Optimized <35mm Premium SRF
De-Ashing and Density Separation for Mercury Reduction
Mercury in municipal waste streams is primarily concentrated in the fine fraction (batteries, contaminated soils, electronic components) and heavy 3D fractions.
- Mechanical Solution: Processing lines utilize high-gradient kinetic air separators. By establishing a balanced positive-pressure air fluidization bed paired with negative-pressure vacuum extraction, the light, flexible 2D combustible fractions (paper, clean polymers, textiles) are separated from the heavy 3D fraction. This reduces the 80th percentile mercury spike risk and safely shifts the fuel into Class 1 or Class 2 environmental boundaries.
Automated Sensor-Based Sorting for Chlorine Control
Chlorine in solid waste occurs in two forms: inorganic chlorine (salts like in organic food waste) and organic chlorine (primarily Polyvinyl Chloride, or PVC plastics). While inorganic chlorine can be reduced by removing fine organic fractions via sizing screens, organic PVC contains approximately chlorine by weight, making it the primary cause of technical parameter failures.
- Mechanical Solution: Facilities deploy automated Near-Infrared (NIR) Spectroscopy Sorters directly after primary air classification. The NIR sensors detect the specific hydrocarbon spectral signature of PVC polymers and trigger a synchronized high-speed compressed air valve matrix to eject PVC particles from the conveyor. This sensor-based extraction loop is essential for maintaining total chlorine levels below the critical threshold required for Class 2 compliance.
4. FAQ
Why does EN 15359 utilize the 80th percentile for Mercury () classification instead of a standard arithmetic mean?
Unlike carbon or hydrogen, which are evenly distributed across polymer matrices, mercury enters municipal waste streams in erratic, highly concentrated spikes (e.g., a discarded button-cell battery or a legacy fluorescent tube fragment). If an engineering design relied solely on a standard arithmetic mean, a single mercury spike could distort the fuel’s analytical profile, concealing operational risks. The 80th percentile ensures that the alternative fuel remains statistically stable and safe for continuous combustion without causing sudden emission violations.
Can a processing plant achieve Class 1 NCV status without thermal drying infrastructure?
Yes, through precise mechanical mass-balance engineering. Attempting to hit Class 1 () by thermally drying mixed wet waste is rarely cost-effective. Instead, processing lines use high-amplitude flip-flow screening matrices to divert low-energy, high-moisture organic fractions () early in the process. Maximizing the concentration of high-calorific 2D polymers (such as Polyethylene and Polypropylene) in the final output naturally raises the fuel’s NCV to premium levels without the high OpEx of thermal drying systems.
Complete Turnkey EPC Production Systems and Infrastructure
Producing alternative fuels that comply with the EN 15359 standard requires robust mechanical separation capabilities and a deep understanding of material thermodynamics. Henan Guoxin Machinery Manufacturing Co., Ltd. (Guoxin Group) designs and builds high-capacity, automated solid waste processing configurations engineered to deliver predictable alternative fuels that satisfy strict international standards.
From initial material mass-balance modeling and 3D plant spatial engineering to the deployment of industrial shredding, air separation, and automated sensor systems, our global engineering division ensures your production facility meets its strict contractual performance targets.
Seeking a detailed engineering layout or an equipment configuration proposal for an EN 15359/ISO 21640 compliant processing facility? Contact our Senior Project Engineering Team: Eve@guoxinmachinery.com