HX
Direct-contact heat exchange
Hot flue gas is bubbled directly through liquid, avoiding the thermal resistance of a solid heat exchanger wall.
System concept
How Bubble Pipe technology works
A bubble pipe system routes exhaust through a liquid column, creating large gas-liquid contact area for direct-contact heat exchange, condensation, impaction, diffusion, and chemical absorption.
CD
Condensing scrubber action
Cooling below the 45-65°C dew point captures latent heat, adding roughly 2.26 GJ per ton of condensed water.
AQ
Multi-mechanism capture
Particles and gases are removed by impaction, diffusion, and chemical absorption into the scrubbing liquid.
System components
Bubble column reactor
Primary gas-liquid contacting vessel.
Gas distribution sparger
Creates uniform small bubbles.
Heat recovery exchanger
Transfers heat to useful sinks.
Demister
Prevents liquid carryover.
Liquid recirculation
Controls pH, chemistry and flow.
Automated control unit
Monitors pressure, temperature and bypass.
Process flow
The process, step by step
From furnace to useful heat: follow the flue gas through the bubble column to thermal recovery and cleaner exhaust.
1Hot flue gas exits the industrial furnace or process at
200-800°C.
2Optional pre-cooling lowers gas to 150-200°C for controlled
entry.
3Gas enters the bubble column reactor through a sparger at the
base.
4Bubbles rise through 1-5 m of scrubbing liquid, maximizing
contact area.
5Gas cools to 40-60°C while pollutants transfer into the
liquid.
6Water vapor condenses below dew point and releases latent
heat.
7Cleaned gas exits through a demister with reduced visible
plume.
8Heated liquid circulates through a heat recovery
exchanger.
9Recovered heat serves district heating, process water or space
heating.
10Scrubbing liquid is treated, pH-adjusted and
recirculated.
Heat recovery
Heat mechanisms and efficiency
Direct gas-liquid contact captures both sensible heat from cooling and latent heat from condensation, including energy usually lost up the chimney.
%
10-15%
Overall efficiency gain when latent heat is captured.
MW
50-90%
Waste heat recovery rate depending on return-water temperature.
FL
20-50%
Fuel energy otherwise lost in flue gas.
H2O
2.26 GJ/t
Latent heat yield per ton of condensed water.
Sensible heat recovery
Thermal energy is captured as flue gas cools from inlet temperature toward the liquid or outlet target.
40-60% contributionLatent heat recovery
Water vapor releases additional thermal energy when cooled below its dew point, a key advantage of condensing systems.
40-60% contributionAir cleaning
Pollutant removal performance
Impaction, diffusion and chemical absorption remove particulates, acid gases and metals in a single wet stage.
Removal efficiency by pollutant
Advantages over dry systems
- Simultaneous heat recovery and pollutant removal in one unit.
- No bag-filter fire risk in high-temperature applications.
- Effective for both gaseous and particulate pollutants.
- Handles high-moisture and high-temperature exhaust streams.
- Lower outlet temperature reduces visible white plume.
Technical data
Specifications and performance ranges
Typical parameters for custom-engineered systems across foundries, steel plants, biomass facilities, cement, glass and chemical process industries.
| Parameter | Range | Design note |
|---|---|---|
| Gas flow capacity | 170-297,000 m3/h | Modular columns in parallel. |
| Inlet gas temperature | 150-800°C | Pre-cooling required above 400°C. |
| Outlet gas temperature | 40-60°C | Below dew point for latent heat recovery. |
| Liquid-to-gas ratio | 0.5-3.0 L/m3 | Higher ratios improve removal efficiency. |
| Pressure drop | 500-2,500 Pa | Compensated by induced draft fan. |
| Liquid column depth | 1-5 m | Greater depth increases contact time. |
| Residence time | 1-5 s | Minimum contact for absorption. |
| Energy consumption | <1-3% of output | Offset by recovered heat. |
99%+
Operational availability.
20-30 yrs
System lifetime.
Quarterly
Maintenance rhythm.
316L / FRP / PTFE
Materials selected by exhaust chemistry and temperature.
Cost-benefit
Heat recovery turns compliance into ROI
CAPEX, operating costs and ROI depend on scale, fuel displacement, recovered heat use and emission-control requirements.
1-5 yrs
Simple payback, typically 24-36 months.
15-40%
Internal rate of return for heat-integrated systems.
$55k-540k+
Annual avoided-fuel savings from heat recovery.
Strong +
Net present value over a 20-year operating life.
CAPEX by scale
Operating cost drivers
- Electricity for fan, pumps and controls.
- Reagents for alkaline scrubbing and pH correction.
- Water makeup and treatment.
- Sludge, spent carbon and captured-material handling.
- Maintenance labour and quarterly inspection cycles.
Case studies
Industry examples
From foundries to steel plants and biomass power: real-world patterns for heat recovery and air cleaning.
Iron Foundry - Midwest USA
VOC and Heat Recovery System
Combined wet scrubbing and regenerative thermal oxidation reduced hazardous air pollutants while recovered heat preheated process air.
- 98.5% VOC destruction
- >95% particulate reduction
- Full EPA HAPs compliance
Aluminum Foundry - Europe
Waste Heat Recovery
Condensing scrubber and heat exchangers captured exhaust heat from 400-700°C furnace streams.
- Primary fuel reduction
- Verified CO2 reduction
- Payback under 3 years
Energy Production - Scandinavia
Biomass Condensing Scrubber
Wet flue gas cleaning recovered latent and sensible heat for a district-heating return line.
- 10-15% efficiency gain
- Several MW added to district heating
- 13-24 USD/MWh delivered heat
Steel Manufacturing - China
Integrated Heat Recovery
Multi-stage cooling, waste heat boiler, evaporative cooling and condensing scrubber reduced energy waste.
- 20-50% less primary energy waste
- Heat recovery below $3/GJ
- Positive return in 2-4 years
Environmental impact
Emission reduction and regulatory alignment
BubblePipe provides direct pollutant reduction and indirect CO2 savings from avoided fuel, while supporting major regulatory frameworks.
Direct emission reductions
100-500+ tonnes CO2/year
Typical avoided emissions per installation by displacing fossil-fuel heat. A 2 MW thermal system operating 6,000 h/year can avoid roughly 2,400 tonnes CO2/year when replacing natural gas heat.
EU IED
Supports Best Available Techniques requirements.
EU ETS
Reduces carbon footprint and trading obligations.
US EPA NESHAP
Targets hazardous air pollutant standards.
Canadian CEPA
Aligns with multi-pollutant emission standards.
Resource recovery
Carbon filtration and recoverable streams
An activated carbon bed in the scrubbing-water circuit captures residual metals and gases, turning stack waste into recoverable resources.
Activated carbon polishing stage
High-surface-area carbon adsorbs vapor-phase mercury, dioxins/furans, residual VOCs, odours and heavy-metal traces that a water scrubber alone cannot fully capture.
Captured pollutants
Thermal energy
0.5-50+ MW sensible and latent heat for heating loops.
Condensate water
0.1-2 t/h treated and reused to reduce freshwater demand.
Metal concentrate
Hg, Pb, Zn and Cd streams sent to specialized refiners.
Metal-oxide dust
Fe, Zn and Al oxides can return to smelting feed.
Gypsum products
SO2 plus lime yields marketable CaSO4.
Regenerated carbon
Spent carbon is thermally regenerated or valorized.
Deployment scale
Applications across every scale
Bubble pipe technology is modular: it scales from a small foundry workshop to a large integrated steel complex.
Small-scale installations
<5,000 m3/h flue gas, 0.5-2 MW recovered, $270k-$540k CAPEX.
- Artisan foundries and casting shops
- Bakeries and food-processing ovens
- Small biomass and wood-fired boilers
- Workshop heating loops
Medium-scale facilities
5,000-50,000 m3/h flue gas, 2-15 MW recovered, $540k-$1.6M CAPEX.
- Iron and aluminum foundries
- Brick, ceramic and glass kilns
- District heating substations
- Chemical, paper and textile plants
Large industrial complexes
>50,000 m3/h flue gas, 15-50+ MW recovered, $1.6M-$2.7M+ CAPEX.
- Integrated steel mills and smelters
- Waste-to-energy and biomass plants
- Cement and lime production lines
- Municipal district-heating networks