Status: Delivered · Region: Southeast Asia · Ref. D-041
Client, site and contract details are withheld under our client-confidentiality policy. Capacity is shown as a capacity class (design value rounded up to the next step of 5); the calculations below start from the class value, ~50 m³/min ≈ 3,000 m³/h.
What We Delivered
Client: a waste-management operator in Southeast Asia; identity withheld.
We delivered a pulse-jet bag filter system for incinerator off-gas: ~50 m³/min class, 900 °C at the inlet, continuous duty. The client's design basis allowed the gas to be cooled if the filter required it, and selecting the filter media was part of our scope.
No filter medium in commercial production survives 900 °C, so the engineering question was never which bag to buy. It was how the gas gets from 900 °C to a filterable temperature, and what that cooling method does to the size and cost of everything downstream. The gas-cleaning train was designed around an evaporative quench to about 180 °C ahead of the filter, with PTFE-membrane glass-fibre media and a filter sized at about 29 m² on the cooled gas volume at a 0.8 m/min air-to-cloth ratio.
Equipment delivered: Pulse-jet bag dust collector — the filtration stage.
Delivery Record
| Stage | What it covered on this project | Record on file |
|---|---|---|
| 1. Design basis confirmation | Gas flow ~50 m³/min class (≈ 3,000 m³/h at gas conditions), 900 °C inlet, continuous operation, particulate removal duty; cooling ahead of the filter permitted; filter media selection included in our scope. | Design basis sheet |
| 2. Process & mechanical design | Cooling method selected (evaporative quench over dilution air and heat recovery); operating temperature set at ~180 °C, between the acid dew point and the 200–400 °C dioxin re-formation band; filter sized on the cooled gas volume at 0.8 m/min (≈ 29 m²); PTFE-membrane glass-fibre media specified. | Process calculation sheet; P&ID and general-arrangement (GA) drawings; media specification |
| 3. Manufacturing & quality control | Collector casing, hopper and pulse-jet cleaning system fabricated; filter bags supplied in the specified media. | Material certificates and QC inspection records |
| 4. Factory acceptance test (FAT) | Pulse-jet cleaning sequence function-tested; installed filter area checked against the design value. | FAT record |
| 5. Packing & dispatch | Collector sections, filter bags and cleaning components packed for export shipment and checked against the packing list. | Packing list |
| 6. Installation | Per contract scope: collector set in place and connected into the gas-cleaning train downstream of the cooling stage. | Installation record (per contract scope) |
| 7. Commissioning | Collector start-up with the filter-inlet temperature confirmed within the ~180 °C design window; pulse-jet cleaning cycle set. | Commissioning log |
| 8. Performance verification | Operation checked against the design basis: gas flow class, filter-inlet temperature within the design window, air-to-cloth ratio at design flow. | Performance test record against the design values |
| 9. Training, handover & after-sales | Operator training on the temperature window, pulse-jet cleaning, and bag inspection and replacement; after-sales support per contract. | O&M manual; training and handover record |
Delivery records for this project are on file and can be reviewed by qualified buyers under a confidentiality agreement.
Designed For
Designed for: 900 °C inlet gas that no filter medium can take directly; continuous operation; fast cooling through the 200–400 °C dioxin re-formation band; an operating temperature held a clear margin above the acid dew point set by HCl and SO₃; sticky, acidic incinerator dust.
| Parameter | Design value |
|---|---|
| Application | Incinerator flue gas cleaning |
| Blower flow rate | ~50 m³/min class ≈ 3,000 m³/h (at gas conditions) |
| Inlet gas temperature | 900 °C |
| Operation | Continuous |
| Duty | Particulate removal from incinerator gases |
| Filter operating temperature | ~180 °C |
| Air-to-cloth ratio | 0.8 m/min (pulse-jet, incineration duty) |
| Filter area | ≈ 29 m² (sizing calculation below) |
| Filter media | PTFE-membrane glass fibre |
Source: project design basis and design calculation (design values).
Why 900 °C Cannot Reach the Bags
Continuous service limits for the media used in this duty:
| Filter medium | Continuous limit | Notes |
|---|---|---|
| PTFE-membrane glass fibre | ≈ 260 °C | High acid resistance; the usual choice for incineration duty |
| P84 (polyimide) | ≈ 240 °C | Good filtration efficiency, sensitive to hydrolysis |
| PPS (polyphenylene sulphide) | ≈ 190 °C | Degrades under high O₂ with acid gases |
| Polyester | ≈ 150 °C | Not applicable to this duty |
The gap between 900 °C and 260 °C is not a safety margin question. It is a design requirement for a dedicated cooling stage.
Source: standard published continuous-service limits for these media.
Choosing the Cooling Method — This Decides the Project Cost
Option A — Dilution with ambient air (rejected)
Mixing in cool ambient air is the simplest method and an expensive one to live with. A heat balance from 900 °C to 180 °C with ambient air at 30 °C shows that the mixed stream to be filtered comes to several times the quench-cooled volume. Because the baghouse is sized on volumetric flow, the filter, fan, ducting and building all grow with it. Dilution suits small intermittent sources, not continuous incineration duty.
Option B — Evaporative quench (selected)
Water sprayed into a quench chamber absorbs heat as it evaporates. Volume still rises, but far less than with dilution because the cooling comes from latent heat rather than mass dilution. For a continuous ~3,000 m³/h incinerator stream this is the conventional choice, and it is the method this project was designed around.
Option C — Heat exchanger / waste-heat recovery (not selected)
Technically efficient, and it returns useful energy, but it carries the highest capital cost of the three options and needs a use for the recovered heat. At this flow rate the payback rarely justifies it unless a heat sink already exists on site.
Two Temperature Limits That Bracket the Design
Upper bracket — dioxin re-formation
Chlorinated organics re-form in the 200–400 °C window through de novo synthesis as flue gas cools. The design intent is therefore to pass through that band quickly. A slow cooling profile — an oversized duct run, an undersized quench — increases residence time in exactly the temperature range you least want it.
Lower bracket — acid dew point
Incinerator gas carries HCl and SOₓ, which raise the acid dew point well above the water dew point. Operate below it and condensing acid attacks the bags, the casing and the hopper, while wet dust blinds the fabric. Operating temperature must sit a clear margin above the acid dew point.
These two limits leave a working window, and 180 °C sits inside it: below dioxin re-formation, comfortably above acid dew point, and inside the continuous rating of PTFE-membrane glass fibre.
Source: standard incineration flue-gas treatment engineering practice.
Sizing the Baghouse at 180 °C
| Step | Calculation | Result |
|---|---|---|
| Gas volume at 900 °C | Design basis (~50 m³/min class) | ≈ 3,000 m³/h |
| Volume after cooling to 180 °C | 3,000 × (453 K ÷ 1,173 K) | ≈ 1,160 m³/h |
| Plus quench water vapour | + ~20% (allowance; depends on the quench design) | ≈ 1,390 m³/h |
| Air-to-cloth ratio (pulse-jet, incineration duty) | Conservative 0.8 m/min | — |
| Filter area required | (1,390 ÷ 60) ÷ 0.8 | ≈ 29 m² |
Note what cooling did: the gas contracts to roughly 40% of its 900 °C volume (453 ÷ 1,173 ≈ 0.39) simply by cooling, before any other consideration. Sized on the uncooled volume, (3,000 ÷ 60) ÷ 0.8 = 62.5 m², the filter would be more than twice as large; sized on the dilution-cooled volume, several times as large.
Source: project design calculation, restated at the capacity-class flow. The air-to-cloth ratio is deliberately conservative for incineration duty; vapour addition depends on the final quench design.
Media Selection
PTFE-membrane glass fibre was specified for this duty. Glass fibre carries the temperature, and the PTFE membrane provides surface filtration — dust releases from the membrane rather than embedding in the fabric, which matters when the dust is sticky and acidic. The membrane also holds emission performance stable over the bag's life instead of relying on a dust cake that repeatedly builds and is cleaned away.
For Similar Projects
- Size the filter on the cooled gas volume — never on the uncooled or dilution-cooled volume.
- For continuous duty, start from an evaporative quench. Dilution air suits small intermittent sources; heat recovery pays back only where a heat sink already exists on site.
- Establish the acid dew point from a gas analysis (HCl, SO₃ and moisture) before fixing the operating temperature.
- Size the vapour addition from the quench heat balance; it depends on how much water the quench evaporates.
- Confirm media temperature and acid ratings against the datasheet of the media you select.
- Where measured HCl/SOₓ requires acid-gas removal, add a flue gas desulfurization scrubber ahead of or after the filter.
The choice between fabric filtration and electrostatic precipitation for this class of duty is examined in our baghouse vs electrostatic precipitator comparison, and pulse-jet cleaning optimisation in our pulse-jet dust collector guide.
Frequently Asked Questions
Can any filter bag handle 900 °C flue gas?
No. The highest continuous rating among media used in this duty is around 260 °C (PTFE-membrane glass fibre). Gas at 900 °C must be cooled before filtration — the cooling stage is part of the system, not an optional extra.
Should I cool incinerator gas with dilution air or a quench?
For continuous duty, a quench. Cooling 900 °C gas to 180 °C with ambient air brings the mixed stream to several times the quench-cooled volume. Because filter size follows volumetric flow, the baghouse, fan and ducting grow accordingly. Dilution suits small intermittent sources only.
What temperature should an incinerator baghouse operate at?
In the window between the acid dew point (below which condensing acid corrodes and blinds the bags) and the 200–400 °C dioxin re-formation band. Around 180 °C typically satisfies both, but the actual acid dew point depends on measured HCl, SO₃ and moisture and should be confirmed by gas analysis.
How much filter area does ~50 m³/min of incinerator gas need?
About 29 m² — but only after cooling. At 900 °C the stream is ~3,000 m³/h; cooled to 180 °C it contracts to roughly 1,160 m³/h, about 1,390 m³/h with the quench-vapour allowance. At a conservative 0.8 m/min air-to-cloth ratio that gives ≈ 29 m². Sizing on the uncooled volume would more than double the filter.
Why PTFE membrane rather than plain fabric?
Surface filtration. Dust releases from the membrane instead of embedding in the fabric, which matters with sticky, acidic incinerator dust, and emission performance stays stable over the bag's life rather than depending on a dust cake that is repeatedly built and cleaned off.
