Jan. 7, 2003 -- As stack emission standards continue to become more stringent and power plant budgets grow ever tighter, there is a growing trend toward enhancement of existing pollution control devices in lieu of extensive upgrades and replacements.
Operators of electrostatic precipitators (ESPs) are seeing an increasing number of new products aimed at boosting the performance of existing systems, often with surprisingly low capital requirements.
A common approach is to improve input and flow of electricity to ESPs, thereby enhancing collection efficiency. One such product that does both is the JuiceCan, a high voltage filter for electrostatic precipitators. Developed by BHA Group, Inc., the product claims to significantly increase secondary current and average voltage. This can lead to higher collection efficiency and lowered stack opacity.
It is economically priced, easy to install, works with all types of precipitators, and requires no special controls. Developers say you simply install it and immediately see results.
The JuiceCan smoothes out the DC pulses from the transformer/rectifier to narrow the gap between peak and minimum voltage. In many cases, the DC voltage from a typical T/R set can be highly rippled, with peak voltage exceeding average voltage by 40 percent or more. The high peak voltage can lead to sparking in the precipitator field at a low average voltage, which robs the field of its collection efficiency.
JuiceCan developers realized that if peak, average, and minimum voltage could be equalized, the precipitator field could operate at maximum power with minimum sparking.
Installed between the T/R set and the precipitator, the JuiceCan is basically a capacitor, but a very special type of capacitor. It is "spiral wound," which provides very high internal inductance. It therefore can be thought of as two components in one: a capacitor and an inductor. While the capacitance increases average voltage into the precipitator, the inductance limits high frequency spark currents so as not to increase spark intensity.
DC voltage filtering is not new. Filters are used on many types of DC power supply applications. There have been numerous attempts to put filters and snubbers on precipitators, with limited results. "Most filters could not withstand the precipitator's high voltage environment," says Terry Farmer, Manager-Electrical Products for BHA, "and eventually everyone gave up on the idea. But our engineers, who have expertise with high voltage applications and precipitator operations, made the breakthrough."
Farmer says his company began researching ideas in late 2001, testing a variety of designs. "We discovered there is significant science and technology involved in making this type of filter. It is a difficult application, and we now know why others gave up trying. " The product is patent pending.
Farmer reports that initial interest in the JuiceCan is higher than any new precipitator product his company has ever developed. "The response has been overwhelming. We have customers lined up at trade shows to talk about it. We are conducting 5 to 7 web conferences per week about it. Even people who are typically skeptical about new technology are asking a lot of questions."
According to Farmer, the reason for the interest is mostly due to the simplicity of the product - and the price. "Many customers are surprised to discover how economical the product is. For a modest investment, they can test three or four JuiceCans on their worst precipitator to see the improvement. It seems that most high technology comes at a high price. We try hard to manufacture products that solve problems without breaking your budget."
Developers claim that testing has gone well, and that the product has been installed in several applications in the U.S. and Europe. The company's website reports one test site in which the JuiceCan improved KV average by 20.5 percent and improved milliamps more than 120 percent. The product comes in a small size that weighs about 75 pounds and a larger size that weighs about 165 pounds. Typically, the product is installed in a bus duct or enclosure.
Farmer says initial customers are pleased, with some reporting "significant" reductions in stack opacity. "As we continue to install JuiceCans in various applications, we'll continue to learn about what it can do. But we think this is a breakthrough technology that has an incredible payback. We're having fun selling it, and we're hearing that customers are enjoying the benefits."
Editor's note: This article is a preview from the upcoming January 2003 issue of Power Engineering magazine.