Residue Treatment
Grate for riddlings
Grate for Riddlings infographic

Introduction

The incinerator bottom ash (IBA) produced by Waste to Energy (WtE) plants are a source of valuable non-ferrous metals, including aluminium, copper, silver and gold. The majority (around 70%) of these metals are typically found in the fine fraction of the IBA. As part of the X2conmat™ process, the Kanadevia Inova Grate for Riddlings (GfR) is a useful modification designed to improve metal recovery in WtE plants with conventional wet IBA discharge.

Our Grate for Riddlings (GfR) upgrades IBA wet-discharge plants, extracting valuable dry fines (0–10 mm) on the grate and enabling higher NF (nonferrous) recovery and improved downstream separation. Retrofit options are available for our Kanadevia Inova grates and other 3rd-party grates.

Description

Advanced metal recovery is achieved by introducing a screening grate element with slits of a defined width into the final combustion grate zone. This enables the valuable fine IBA fraction, which accounts for around 40 wt% of the total IBA, to be extracted in a dry state. Separation is assisted by the mechanical sieving movement of the grate superimposed on the feed and by special “deflectors” on the grate. Dust-tight, dry discharge of the separated fine fraction for further processing ensures high metal recovery rates and high-quality recovered metals.

The remaining bottom ash is discharged using the conventional wet extraction method. GfR optimises both the quantity and quality of the recovered metals. Reducing the metal and water content in the remaining residue also lowers transport costs and landfill gate fees.

Grate for Riddlings
Advantages

  • Fully enclosed equipment means no dust emissions

  • More efficient metal recovery with high precious metal content

  • Preserves metal quality

  • Reduces transport costs and landfill gate fees

  • Provides environmental benefits and supports the circular economy because recycling of recovered materials improves the CO₂ footprint

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Further related technologies

Grate Combustion systems

The combustion system is the best-proven thermal waste treatment technology for mixed municipal, industrial or hazardous waste, and the heart of any modern, state-of-the-art Waste to Energy (WtE) plant.

Flue gas treatment

Incinerating waste produces exhaust gases laden with diverse pollutants. Different processes are used to remove these pollutants before the purified flue gas leaves the plant safely through the stack.

Carbon capture

Capturing carbon dioxide (CO2) from the flue gas produced in hard-to-abate industries and properly storing it (a process called carbon capture and storage or CCS) is a key component of most governments’ net-zero strategies.

Energy recovery

Recovering the energy content of waste is a key component of WtE technology. Since the process is largely renewable and involves only a low level of emissions, it also helps significantly reduce greenhouse gases.

Residue treatment

Thermal waste treatment produces residues which can be either reused or landfilled. The principal components are slags and ashes, consisting mostly of non-combustible waste constituents such as glass, minerals or scrap metals.

EcoFlex™ WtE plant solution

The new pre-engineered EcoFlex™ solution provides a modern waste infrastructure based on proven in-house technologies, allowing a cost-optimised design of single-line Waste to Energy plant construction and operation.