Volcan White Paper0 pages

White Paper: Gaining control of ESP’s fly ash hoppers
Abstract
Managing the fly ash inside ESP hoppers presents significant challenges. While
avoiding the risk of pollution is extremely important, operation and maintenance costs
must also be managed. The lack of decision support information is one of the reasons
making this situation so hard. This paper will highlight the source of the problem,
review available solutions with their strengths and shortcomings and then present a
breakthrough development that offers a significant improvement for day to day
management of these hoppers.
The Problem
ESP’s are used to clean flue gas of air polluting particles by using an electrostatic
charge. The particles, known as Fly Ash, collect in hoppers below the ESP and are
then removed for transportation or long term storage. Fly ash can be very sticky and
tends to build up. Fly ash build up inside the hopper can lead to ESP malfunctions
which may result in air pollution, causing severe financial implications. The
implications of incorrect or missing level information are measured in the $10,000s,
be it maintenance costs, repair of damage to the ESP equipment, lost production
capacity or fines for air pollution. Many facilities protect themselves from exceeding
the top level by using time based emptying of the hopper. This means the hopper will
be emptied even if it is not yet full. These practices significantly increases energy
expenditure and puts much more strain on the conveying system, resulting in faster
wear and tear. Therefore knowing and tracking the actual behavior of the material
inside these hoppers can reduce both costs and risk, both of which are of significant
importance to the facility management.
Tracking the fly ash inside the ESP hopper presents quite a few challenges as the
material is very hot, sticky and abrasive. It carries a static charge, has low and
variable density and low dielectric constant that changes over time. There is also a lot
of suspended dust in the hopper. These properties have made many reliable levelmeasuring technologies fail when applied to ESP hoppers.
Additional challenges arise from the ESP’s structure and characteristics, such as the
moving parts above the hopper and the high temperature. Some level solutions,
prevalent in other applications, are rendered unusable in ESP applications by these
characteristics. These solutions include manual observation and tape measure, plunge
bobs, ultrasonic sensors and laser sensors.