HEAT TRANSFER
A GUIDE TO ADVANCED ELECTRIC BOILER TECHNOLOGY
Del Williams, a technical writer for Acme Engineering, explains how industry professionals can take advantage of high voltage electrode boilers’ virtually 100% efficient, zero-emission capabilities
or consulting engineers tasked with planning, designing, and supervising construction projects for a wide range of industries, advanced electric boilers – particularly high voltage electrode boilers – offer numerous advantages over traditional fossil fuel burning boilers. Due to advances in technology, these boilers can match the capacity (up to 65 MW) and output (270,000 pounds of steam per hour) of traditional gas or oil-fired boilers in a much smaller footprint while converting almost all the energy to heat. These zero-emission, high voltage electrode boilers are used in diverse environments for applications such as centralised heating, power plants, nuclear stations, solar/wind energy consumption, and fuel boiler replacement.
F
To bridge the knowledge gap, Presser explains what consulting engineers most need to understand about electric boiler technology, including its selection, implementation, and benefits.
Today, there is growing interest in utilising a new generation of these boilers as an environmentally friendly decarbonisation solution. Companies across the globe are considering using electric boilers to become carbon neutral in alignment with COP26 UN Climate Change Conference targets. Electric boilers are emerging as more environmentally friendly solutions compared with traditional gas-fired units that emit greenhouse gasses and also dangerous nitrogen oxides (NOx), carbon monoxide (CO), and nitrous oxide (N2O), as well as volatile organic compounds (VOCs), sulphur dioxide (SO2), and particulate matter (PM). “Communities and businesses appreciate the eco-friendly nature of ultra-efficient, electric boilers. Without combustion, these boilers are safe, clean, and emission free,” said Robert Presser, Vice President of Acme Engineering.
However, the challenge for consulting engineers is that many have experience with gas-fired boilers but are less familiar with the selection and implementation of advanced electric boilers, especially the high voltage, high-capacity alternatives available today.
Types of electric boilers The first factor to consider in selecting an electric boiler is how much capacity will be required by the user, business, or community. Lower voltage (480KV) electric resistance heating element boilers are economical, compact, reliable sources to produce steam or hot water for industrial use. The units are well suited to supply these resources at lower capacities, from 9 to 3,600kW.
However, there are design limitations when heating element boilers exceed 4MW in capacity, as numerous flanges, elements, contactors, and fuses are typically necessary to function properly. The considerable amperage involved also requires expensive bars for distribution, step-down transformers, and large switch gear.
To avoid these complications at capacities of 4MW or higher, high voltage jet type and immersed electrode boilers were developed. High Voltage Electrode Boilers In the high voltage category, electrode boilers consist of two basic types: immersion and water jet.
In resistance element type boilers, current
flows through a resistance wire, which generates heat. The heat is transferred
20 DECEMBER 2024/JANUARY 2025 | PROCESS & CONTROL
through the element’s sheaf and into the water by conduction to produce hot water or steam.
“With the immersed electrode design, electric current is passed through the water from the electrodes to the counter electrodes [grounded via the vessel’s shell]. The more direct the exposure between counter electrode shield and the electrode, the greater the current draw [amperage] and the more power is produced in hot water or steam,” explains Presser.
Modern jet type electrode boilers utilise the conductive and resistive properties of water to carry electric current and generate steam. An AC current from the grounded central column to a minimum of one electrode box per phase, using the water as a conductor. Since the water has electrical resistance, the current flow generates heat directly in the water itself. “The more current [amps] that flows, the more heat [BTUs] is generated, and the more steam is produced,” says Presser. High voltage jet or immersed electrode boilers directly connect to high voltage supply lines from 4.16KV - 25KV. Hot water boilers are filled with treated water to create a closed loop system.
The maximum capacity of the boiler can be adjusted by varying the conductivity, which is determined by the temperature and boiler capacity. Typically, a conductivity monitor is installed in the piping and any adjustments are automatically made with chemical treatment.
When it comes to installation, consulting engineers need to consider whether there is sufficient high voltage power, and if a new transformer will be required.
“For these high voltage electrode boilers, the incoming voltage typically required by code is a 4-Wire, three-phase wye wiring configuration, and the phases must be balanced,” said Presser.
In addition, it is necessary to ensure that there is sufficient available space to bring in and install the electrode boilers. This includes determining that there is adequate access into buildings and elevators as well as enough clearance through hallways and doors. When space is limited, Acme’s Slim Series resistance boilers units are designed to produce ample hot water while easing conversion and installation with an ability to “squeeze through” narrow passageways and fit into smaller spaces without costly demolition. The Benefits of Electric Boilers For consulting engineers considering the use of electric boilers, there are numerous advantages over gas fired units. These include very high energy efficiency and output control, along with increased safety and other benefits.
“With an electrode boiler, you get out of it what you put into it. Basically, you don’t have a
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48
