Prevent Electrostatic Precipitator and Baghouse Hopper Blockage with Hopper Heaters

Coal-fired power plants in the U.S. require the use of electrostatic precipitators or bag houses to filter out very fine fly ash particles incorporated into flow gas. The ash is collected while the flue gas passes through filter bags or large electrodes and then falls into hoppers. As the hot fly ash cools, it may condense on the hopper walls. The mixture of dry, sulfur-rich fly ash and water is very problematic, so it is very important that there is no condensation in the collection hoppers.

The mixture of water and fly ash can cause the hopper to block up (or "pluggage "), and most importantly, residual sulfur in the flue gas will combine with condensate to form sulfuric acid. The sulfuric acid attacks the inside of the hopper walls, causing corrosion, weakening walls and generating significant (and costly) maintenance problems over time.

Efficient and continuous removal of fly ash is essential for all coal-fired power plants. Collection hoppers are an integral part of the removal process. Plugging or inoperable hoppers are a known problem for engineers and maintenance crews. Constant maintenance and excess downtime seriously prevent a plant's ability to manage the production rate of fly ash. Slower fly ash production means a reduction in energy production and efficiency. The power generation of a power station is directly proportional to its rate of combustion of coal, which in turn directly affects the production of fly ash. The maintenance personnel usually attempt to remedy ash system failures in real time by disabling the affected hopper, while continually generating electricity and ash. In some situations (to prevent shutdowns of boilers), ash will be dumped on the floor, requiring costly cleaning.

Evacuation and management of fly ash is much easier if the ash is kept warm. One of the most common ways of maintaining high fly ash and hopper temperatures is by connecting electric hopper heaters to the outside hopper walls. Hopper heaters play a very important role in removing the fly ash from precipitators and bag filter walls by keeping the hopper temperatures over the flue gas acid dew point. The only function of the hopper heater is to preheat the hopper and the internal environment to prevent the formation of moisture, fly ash clumping and the development of sulphuric acid.

Hopper heaters are designed for a dirty, high-vibration power plant environment. They provide the optimum watt density for proper thermal transfer through the hopper wall and uniform heating. They are available in square, rectangular and trapezoidal shapes for any hopper design. For poke tubes, man-ways and cylindrical throats, ancillary flexible heating cloths are available. The use of electric hopper heaters in electrostatic precipitator and bag house fly ash collection systems is an effective time-tested way to prevent condensation and the resulting clumping and corrosive acids in hopper products, thus providing better opportunities for continuous production of fly ash.

Eliminate Costly Hopper Pluggage with Electric Hopper Heaters

Modular, metal-clad hopper heaters
installed on large hopper.

Fly ash is a by-product of coal fired and waste-to-energy fired electrical generating facilities. Fly ash is a combination of dust and fine particles produced during combustion. Environmental laws require fly ash to be collected and not released in to the atmosphere. Large collectors called electrostatic precipitators combined with a system of filters extract fly ash from the flue gas and dispense the fly ash in large steel hoppers prior to being dumped in to containers and transported.

Due to the temperature differential between the hot internal temperature of the hopper and the cooler exterior, condensation forms on the internal wall surfaces, The condensation, combined with the fly ash, creates a concrete-like material that bonds to the hopper walls. The accumulation of this material eventually clogs the hopper to the extent it cannot be emptied. At this point, the only way to free the clogged material is with sledge hammers and pneumatic tools and long periods of downtime and the related expense.

To prevent the fly ash and condensate mixture from forming,

electric heaters are bonded or clamped to the exterior walls and throat of the hopper. Because the environment is normally very dirty with high vibration, “hopper heaters” are designed to withstand to meet these mechanical and environmental stresses.

Hopper heaters come in a variety of physical sizes, voltages, and wattages. Most often, hopper heaters come in pre-engineered sets that have been specified and configured by an applications engineer.

For more information on any hopper heating application, contact Hotfoil-EHS for a free consultation. Visit http://www.hotfoilehs.com or call 609.588.0900.

Electrostatic Precipitator and Bag House Hopper Heaters Prevent Fly Ash Production Problems

Coal fired power plants must manage fly ash properly.

Coal fired power plants in the United States require the use of electrostatic precipitators or bag houses to filter out very fine fly ash particulate incorporated in the flue gas. The ash is collected as the flue gas passes through filter bags or by large electrodes, and then falls into collection hoppers.

As the hot fly ash cools, condensate on the hopper walls can form. The mixture of dry, sulfur rich fly ash and water is very problematic, so it's very important to keep condensation from forming in the collection hoppers. The mixture of water and fly ash can cause clogging (or “pluggage”) in the throat of the hopper,  and more importantly, the residual sulphur in the flue gas will combine with the condensate to form sulphuric acid. The suluric acid attacks the hopper walls from the inside causing corrosion, weakening the walls and creating significant (and costly) maintenance issues over time.

Fly ash hopper with heaters.

Efficient and continuous fly ash removal is critical for all coal fired power plants. Collection hoppers are an integral part of the removal process. Pluggage or inoperable hoppers are a known issue to engineers and maintenance crews. The constant maintenance and excess of down time seriously hinder a plant’s ability to manage the fly ash production rate. Slower fly ash production means limiting energy production and efficiency. A power plant’s electricity production is directly proportional with its coal combustion rate which, in turn, directly effects the fly ash production rate. Plant maintenance personnel usually attempt to remedy ash system failures in real time by deactivating the affected hopper while continuing to generate power and ash. In some situations (to prevent boilers shutdowns) ash will be dumped on the floor, requiring costly clean up.

The evacuation and management of fly ash is much easier when the ash is kept hot. One of the most common ways to maintain elevated fly ash and hopper temperature are electric hopper heaters attached to the external hopper walls. Hopper heaters play a very important role in the removal of fly ash from precipitators and bag filter hoppers by keeping the hopper temperatures operating above the flue gas acid dew point. The hopper heater’s sole function is to preheat the hopper and the internal environment to prevent the formation of moisture and the resulting clumping of fly ash and development of sulphuric acid.

Flexible heating element used on hopper throat.

Hopper heaters are designed for the dirty, high vibration environment of a power plant. They provide the optimum watt density for proper conduction through the hopper wall and for uniform heating. The are available in square, rectangular, and trapezoidal shapes to accommodate any hopper design. Ancillary flexible heating blankets are available for poke tubes, man-ways, and cylindrical throats.

The use of electric hopper heaters on electrostatic precipitator and bag house fly ash collection systems is a time proven, effective way to prevent condensate formation and the resulting clumping and corrosive acids in hoppers, thus facilitating a better opportunity for uninterrupted fly ash production.

For more information, contact:

Hotfoil-EHS, Inc.
2960 East State Street Ext.
Hamilton, NJ 08619
Phone # 609.588.0900
Fax # 609.588.8333

Email: dap@hotfoilehs.com

www.hotfoilehs.com

Electric Heating Systems for Power Generation Baghouse and Precipitator Hoppers

Pluggage of flyash collection hoppers due to flue condensation is an expensive and unnecessary problem. Type HB Heating Module systems are specifically designed to eliminate the maintenance nightmare of hopper pluggage.

The HB Heating Module system is designed to provide low watt density heat spread over the maximum surface area available for heating. Uniform heating is essential to avoid cold spots, especially near the hopper throat where fly ash pluggage is most prevalent and problematic. To obtain maximum heater coverage, both rectangular and trapezoidal heaters are available to provide the most effective and efficient application of heat.

Most flyash hoppers are designed with poke tubes, manways, and cylindrical throats. As supplemental equipment we can include custom built flexible heating blankets for these problem areas which become integrated with the HB Module system to provide the ultimate in uniform heat distribution.

Electric Heating Systems for Power Industry Baghouse and Precipitator Hoppers from Hotfoil EHS, Inc.