Fly ash is the residual product that rises with flue gases during combustion. Millions of tons of fly ash are produced in the U.S. every year.

Once a material is pulverized, it is blown with air into the boiler’s combustion chamber, where it ignites, generates heat and creates a molten mineral residue. Boiler tubes extract heat from the boiler, cooling the flue gas and causing the residue to harden into ash.

About 10% of the particles are coarse ash – also known as bottom ash or slag – that falls to the bottom of the combustion chamber.

The remaining 90% are tiny particles that remain suspended in the flue gas. These become the fly ash. If the particles are not collected, they are blown out with the flue exhaust. To help reduce the emission of fly ash, plants will often use particulate emission control devices such as baghouses, scrubbers or electrostatic precipitators to collect them. These methods typically succeed in catching most but not all of the ash.

Why Remaining Fly Ash Is a Problem

Fly ash can take many physical and chemical forms depending on the type of fuel burned and the handling methods. Typical fly ash also is extremely fine, with most particles being smaller than 100 microns.

The particles that escape combustion-chamber collection can become a potential hazard, as some can contain acidic, toxic and radioactive material that can contaminate air, soil and groundwater. The EPA has found that exposure to polluted particles over long periods can increase the risk of developing cancer, respiratory diseases and cognitive defects.

Fly ash’s properties make it hard to handle for transport as well. Nearly half of fly ash is repurposed for uses such as producing concrete, grouts and asphalt for highways. A percentage of fly ash also is taken to landfills for disposal. Because the particles are so fine, fly ash is prone to release and escape while in transit.

For these reasons, without proper fly ash dust control and suppression, bulk material handlers confront a growing threat to safety, compliance and productivity. More operators are now looking for solutions and answers for how to better prevent fugitive fly ash.

Case in Point: How Benetech Resolves a Fly Ash Challenge

Fly ash has been on the rise within the pulp and paper industry because of its biomass combustion processes. Consequently, the industry is seeking energy-efficient mechanisms and management for the better ecological and economical use of fly ash.

Before and after fly ash control treatment

A pulp and paper facility in the Western U.S. was running into dusting issues during its ash-conditioning process. Its current fly ash handling system had been using a series of screw conveyors to move the ash to a discharge point at a rate of 12 tons per hour.

The discharge’s 10-foot vertical drop to the receiving trucks was producing extreme amounts of fugitive dust. The system required modification to both reduce the transfer dust and improve operational safety.

The facility consulted Benetech for a much-needed solution. We responded with a fly ash dust suppression system with a target of 1.5% total moisture addition.

To control fly ash dust during discharge, we installed spray-injection ports in the screw conveyor. This allowed for proper mixing before the fly ash was released to the receiving truck. The fly ash dust suppression system used our BT-210W chemical to improve the wetting and mid-term residual dust control during loading. We also assigned a Benetech Field Technician to support the customer before, during and after system installation.

Since implementing our fly ash dust suppression, the facility has drastically reduced its dust levels while establishing a safer and more-efficient work environment.

Finish Off Fly Ash Dust Starting Today

Benetech knows your desire to stop dust from interfering with your mission. That’s why we leave no speck out of your aim. If you have a fly ash dust challenge, let’s discuss how you can control and prevent it. Contact us at (630) 844-1300 to speak with a Benetech specialist.

Posted in Dust Control, Flow Control Chutes, and Fugitive Dust Emissions