85–95 %
Stage collection efficiency
Technology · Proprietary hybrid pre-collector
Electrocyclone
The Electrocyclone is a proprietary hybrid particulate pre-collector developed by Arrow Energy Co., Ltd. (Thailand) that combines cyclonic separation with electrostatic augmentation. It collects 85–95 % of boiler fly ash per stage — 50–80 mg/Nm³ @ 6 % O₂ dry outlet standalone — at gas temperatures up to 400 °C, drawing 120–140 kW, in 60–65 % of an equivalent-duty ESP's footprint.
50–80 mg/Nm³ @ 6 % O₂ dry
Standalone outlet
≤ 400 °C
Service temperature
120–140 kW
Absorbed power
01 — Definition
What the Electrocyclone is, and the problem it exists to solve
One casing, two collection mechanisms, no compromise between them.
The Electrocyclone is a hybrid particulate collector: a high-efficiency cyclone body with a high-voltage DC discharge electrode system built into it. Flue gas enters tangentially and spins, exactly as in a conventional cyclone; centrifugal acceleration drives the coarse particles — broadly everything above about 20 µm — to the grounded wall, where they lose momentum in the boundary layer and spiral down to the hopper. What is different is what happens to the particles that a cyclone cannot catch. A discharge electrode held at negative DC potential along the axis of the swirl generates a corona that charges the fine fraction; the resulting electrostatic force adds a radial migration velocity toward the same grounded wall. Two independent forces, one collecting surface, one ash discharge.
It matters because the two mechanisms fail in opposite directions. Centrifugal separation weakens rapidly below about 20 µm, where Stokes drag overwhelms particle inertia; electrostatic migration is strongest precisely on those fine, easily charged particles. The hybrid therefore collects the 5–20 µm fraction that passes straight through a mechanical multicyclone, and it is this fraction that dominates the residual load on bagasse and biomass fly ash. The result is 85–95 % collection per stage — against a realistic 65–85 % for a multicyclone on the same dust — with an outlet of 50–80 mg/Nm³ at 6 % O₂ dry when operated standalone.
The Electrocyclone is a proprietary development of Arrow Energy Co., Ltd. (Thailand) and sits in the company's gas-cleaning technology range alongside the electrostatic precipitator and bag filter, most often as the first stage of a two-stage train. No third-party equivalent exists under this name; the performance envelope below is Arrow's own, from technical note AE-TN-EC-ESP-01.
02 — Mechanism
Why electrostatic augmentation changes cyclone physics
Adding a second radial force where the first one runs out.
In a cyclone, the radial force on a particle scales with particle mass — with the cube of diameter. Halve the particle size and the separating force drops by a factor of eight, while the drag opposing radial motion drops only linearly. That is why every mechanical cyclone has a cut diameter, a d₅₀ below which collection collapses, and why pushing the cut finer by tightening tube diameter or raising velocity buys efficiency only at the price of steeply rising pressure drop and erosive wear.
Electrostatic force obeys different arithmetic. Field charging saturates in proportion to particle surface area (diameter squared), and for the finest particles diffusion charging takes over, so the electrostatic migration velocity degrades far more gently with size than centrifugal separation does. By superimposing a corona field on the swirl, the Electrocyclone gives the 5–20 µm fraction a second, size-tolerant path to the wall — without shrinking the tube, without raising gas velocity, and therefore without the pressure-drop and wear penalties a finer-cutting mechanical design would demand. The swirl, in turn, continuously scours collected dust down toward the hopper, which relieves the rapping and re-entrainment problems of a plate-type precipitator.
How does an Electrocyclone differ from a multicyclone?
A multicyclone separates by centrifugal force alone and realistically collects 65–85 % of biomass fly ash, missing most of the 5–20 µm fraction. The Electrocyclone adds DC corona charging inside the cyclone body, so fine particles migrate electrostatically to the wall as well, lifting stage collection to 85–95 % and cutting the outlet to 50–80 mg/Nm³.
The distinction shows up hardest at the fine end. On a typical bagasse fly ash with substantial char carryover, the mass that penetrates a multicyclone is almost entirely below 20 µm — the fraction downstream equipment must then be sized for. The Electrocyclone removes most of that fraction at the first stage, which is why it changes the economics of everything behind it (Section 04). Maintenance profiles also diverge: a multicyclone erodes at its tubes and vanes and plugs at its hoppers, while the Electrocyclone has near-zero moving-part maintenance — the items that need periodic attention are the high-voltage supply and discharge electrode alignment, inspected on normal outage cadence.
03 — Envelope
Performance envelope
Indicative figures from Arrow technical note AE-TN-EC-ESP-01.
| Parameter | Value | Remark |
|---|---|---|
| Stage collection efficiency | 85–95 % | Dust- and design-dependent |
| Outlet concentration, standalone | 50–80 mg/Nm³ | Single stage, no downstream collector |
| Service temperature | ≤ 400 °C | vs ≤ 200 °C for a dry ESP |
| Absorbed power | 120–140 kW | Mid-size unit; ESP order 250 kW |
| Plot footprint | 60–65 % | Of an equivalent-duty ESP |
| Pressure drop | CONFIRM: Electrocyclone pressure drop range, mmWC | Basis: design gas velocity |
| Moving-part maintenance | Near zero | No rappers, no bags, no rotating parts in the gas path |
What outlet dust concentration can an Electrocyclone achieve?
The design envelope is 50–80 mg/Nm³ at 6 % O₂ dry as a standalone stage, with stage collection of 85–95 % — the achievable figure on a given duty depends on inlet load and particle-size distribution and is stated per project. On heavy raw-gas loads it is applied as a first stage: in the two-stage design basis, 6,000 mg/Nm³ falls to 720 mg/Nm³ and a four-field ESP finishes at 24 mg/Nm³.
Guaranteed figures are stated per project after the technical assessment, on a stated basis — mg/Nm³, reference O₂, dry or wet, and load range. The values above are the design envelope, not a guarantee. The 400 °C service temperature deserves emphasis: it allows the Electrocyclone to sit upstream of economizer and air-preheater surfaces, taking out the coarse, abrasive, silica-rich fraction of bagasse ash before it reaches the tube banks, and it removes any dependence on flue-gas conditioning that a temperature-limited collector would impose on plant layout.
04 — System role
First stage of a two-stage train: the worked numbers
Removing ~90 % of the load ahead of the final collector re-sizes everything behind it.
DESIGN BASIS — ILLUSTRATIVE CALCULATION, NOT A GUARANTEE · all concentrations @ 6 % O₂ dry
- Boiler
- 60 t/h bagasse-fired
- Raw dust at train inlet
- 6,000 mg/Nm³
- Electrocyclone stage, 88 %
- 720 mg/Nm³ at ESP inlet
- Four-field ESP, 96.67 % on remaining load
- 24 mg/Nm³ at stack
- Train total
- 99.60 %
- One ESP field out of service (n−1)
- 57 mg/Nm³
- ESP for this duty
- SCA 75.7 s/m · 3,888 m² collecting area · inlet d₅₀ 21 µm · 177 kW absorbed
Read the numbers backwards to see what the pre-collector buys. Without it, an ESP alone would have to collect 99.60 % of a 6,000 mg/Nm³ load to reach 24 mg/Nm³. With the Electrocyclone removing 88 %, the ESP's required collection falls to 96.67 %. Under the Matts-Öhnfeldt relation used for real polydisperse dust (k ≈ 0.5), required SCA scales with [ln(1/P)]², where P is penetration — so relaxing the target from 99.60 % to 96.67 % cuts the required specific collecting area by roughly 60 % on this illustrative basis. That is the difference between a five- or six-field precipitator and the compact four-field unit at 75.7 s/m in the design basis, with the capital, plot length and absorbed power that follow.
Ahead of a bag filter the arithmetic changes form but not direction. Cutting inlet load from 6,000 to 720 mg/Nm³ cuts the dust-cake mass deposited per filtration cycle by the same ~88 %, so pulse-cleaning frequency drops, baseline pressure drop sits lower in its 100–150 mmWC band for longer, and bag life extends because both flex-cleaning cycles and abrasive inlet impingement fall together. On biomass duty the Electrocyclone also acts as an ember knock-out: glowing char particles are captured and quenched at the first stage rather than landing on filter media.
There is also an ash-handling argument. Two stages split the ash: the coarse, char- and silica-rich fraction reports to the Electrocyclone hopper, while the fine fraction reports to the ESP or baghouse hoppers. The streams can then be handled on their own merits — the coarse char-bearing catch considered for reinjection or separate disposal, the fine ash kept clean of coarse grit — and roughly 90 % of the total mass is removed at the first, simplest, most wear-tolerant piece of equipment in the train. In sugar & bagasse plants, where fly-ash silica content is high and abrasive, that is where you want it removed.
Where does an Electrocyclone fit in a gas-cleaning train?
It installs between the boiler outlet and the final collector, tolerating gas up to 400 °C, and removes roughly 90 % of the particulate load. The downstream ESP then needs about 60 % less specific collecting area for the same 24 mg/Nm³ target on the design basis, or a downstream bag filter sees an ~88 % lighter dust cake per cycle.
Retrofit is the most common entry point: an existing train whose multicyclone no longer gets a plant under its permit, or an ESP that has run out of margin as fuel or load changed. Replacing the mechanical stage with an Electrocyclone in a comparable plot space — the unit needs only 60–65 % of an equivalent-duty ESP footprint — restores headroom without rebuilding the final collector. The multicyclone page treats the upgrade case in detail from the other side.
05 — Comparison
Electrocyclone vs mechanical multicyclone
Same slot in the train; different physics, different outlet.
| Parameter | Multicyclone | Electrocyclone |
|---|---|---|
| Separation mechanism | Centrifugal only | Centrifugal + electrostatic augmentation |
| Overall collection, biomass fly ash | 65–85 % | 85–95 % |
| Collection at ~20 µm and above | ≈ 90 % and higher | ≈ 95 % and higher |
| Collection, 5–20 µm fraction | Weak — below the effective cut, largely passes | Strong — electrostatic migration dominates here |
| Collection, sub-5 µm fraction | Minimal | Partial, via diffusion charging |
| Typical outlet, standalone | Set by inlet load; commonly ≥ 1,000 mg/Nm³ at 6,000 mg/Nm³ inlet | 50–80 mg/Nm³ @ 6 % O₂ dry |
| Pressure drop | 80–120 mmWC | CONFIRM: Electrocyclone pressure drop range, mmWC |
| Electrical absorbed power | ≈ 0 kW (fan power carries the whole duty) | 120–140 kW |
| Service temperature | Refractory/material-limited, typically ≥ 400 °C | ≤ 400 °C |
| Wear behaviour on silica-rich ash | Tube and vane erosion at high internal velocity | Lower internal velocity for the same duty; wear correspondingly reduced |
| Maintenance profile | Tube replacement, hopper plug clearing | Near-zero moving parts; HV supply and electrode checks at outages |
The honest way to read this table: a multicyclone is cheaper and consumes no electrical power, and where the duty is pure coarse-ash knock-out at modest efficiency it remains a defensible choice. The Electrocyclone earns its power draw when the 5–20 µm fraction matters — which, for a plant trying to reach a stack limit in the tens of mg/Nm³, it always does. The fan-power arithmetic behind the pressure-drop row is worked through on the multicyclone page.
06 — Track record
Where Electrocyclones run today
Reference classes, stated without names.
Arrow Energy supplies Electrocyclones as new-build first stages and as retrofits into existing trains. Anonymised reference classes include a 170 t/h bagasse-fired sugar mill in Thailand, a 250 t/h biomass power plant in Thailand, and a 230 t/h sugar mill in Colombia — duties spanning the bagasse and mixed-biomass fuels for which the technology was developed, with their characteristic high char carryover and abrasive, silica-rich fly ash. Fleet status: CONFIRM: Electrocyclone fleet count and cumulative t/h. Project summaries on a comparable anonymised basis are collected under references.
Every application starts from the same three questions: the particle-size distribution and char content of the actual fly ash, the temperature window available at the intended insertion point, and the stack limit with its stated reference conditions. From those, the stage efficiency is set inside the 85–95 % envelope and the downstream collector — electrostatic precipitator or bag filter — is sized against the pre-collected load. Guaranteed figures are stated per project after that assessment, on a stated basis: mg/Nm³, reference O₂, dry or wet, and load range.
FAQ
Engineering questions, answered
What is an Electrocyclone?
An Electrocyclone is a proprietary hybrid particulate pre-collector developed by Arrow Energy Co., Ltd. (Thailand). It combines cyclonic separation with electrostatic augmentation in a single casing, collecting 85–95 % of fly ash per stage with a standalone outlet of 50–80 mg/Nm³ at 6 % O₂ dry, at gas temperatures up to 400 °C.
How efficient is an Electrocyclone compared with a multicyclone?
An Electrocyclone collects 85–95 % of inlet particulate per stage; a mechanical multicyclone typically achieves 65–85 % on biomass fly ash. The difference sits in the 5–20 µm fraction, where the DC corona field adds an electrostatic migration velocity that centrifugal force alone cannot provide at practical pressure drops.
What temperature can an Electrocyclone operate at?
The Electrocyclone is rated for continuous service up to 400 °C, roughly twice the 200 °C ceiling of a conventional dry electrostatic precipitator. This allows installation upstream of heat-recovery surfaces such as economizers and air preheaters, where it also protects those tube banks from abrasive silica-rich fly ash.
Can an Electrocyclone replace an ESP or bag filter?
Usually it works ahead of one, not instead of one. Standalone outlet is 50–80 mg/Nm³ at 6 % O₂ dry, which suits some permits; where tens of mg/Nm³ or below is required, the Electrocyclone removes roughly 90 % of the load and a smaller ESP or bag filter finishes the job.
How much power does an Electrocyclone consume?
Absorbed electrical power is 120–140 kW for a mid-size unit, against an order of 250 kW for a mid-size four-field ESP. The high-voltage DC supply drives corona charging only; separation work is shared with the cyclonic swirl, which is why the electrical demand stays comparatively low.
Who developed the Electrocyclone?
The Electrocyclone is a proprietary technology of Arrow Energy Co., Ltd., a Thai–US industrial engineering group headquartered in Bangkok with its factory and R&D centre in Samut Sakhon, Thailand. Units are applied on bagasse, biomass and process boilers, typically as an 85–95 % efficient first stage ahead of an ESP or bag filter.
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