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Small scale pellet boiler gas treatment in fog unit


The current research is aimed at experimentally finding out characteristic parameters of the operation of the fog unit and their effect on the efficiency of particulate matter capture. To conduct the experiment, a laboratory equipment—fog unit—was designed and prepared. The fog unit is suitable for 10, 20 and 30 kW pellet boilers. The impact of the parameters on essential changes of indicators important for PM capture is described: sprayed water and gas contact surface; droplets and gas contact time in the unit; droplets holdup in the unit. In the process, a regression equation for predicting the effectiveness of PM capture in a direct contact fog unit is obtained. A good experimental and calculated data correlation is observed (adjusted R squared statistics is 85.32%).

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ω1, ω2 :

Inlet and outlet moisture content, kg/kg dry gas

C p1, C p2 :

Inlet and outlet PM concentration in flue gas, mg/Nm3

ΔC p :

PM reduction, %

d d :

Diameter of a droplet, m

d d0 :

Initial diameter of a droplet, m

F d :

Total droplets surface area, m2

g :

Water volumetric flow rate, l/s

G b :

Boiler water flow rate, m3/h

G w :

Water volumetric flow rate, l/h

H :

Height of the unit, m

H d :

Droplets holdup of the unit

M f :

Fuel consumption, kg//h

O 2 :

Oxygen concentration in flue gas, %

O f :

Fuel lower heating value, MJ/kg

O fu :

Fog unit capacity, kW

O b :

Boiler capacity, kW

t b1, t b2 :

Boiler water input and output temperature, °C

t g1, t g2 :

Gas inlet and outlet temperature, °C

t w :

Water temperature, °C

t w1, t w2 :

Inlet and outlet water temperature, °C

u d :

Droplet velocity, m/s

u g :

Gas velocity, m/s

u g2 :

Outlet gas velocity, m/s

u r :

Settling velocity of a droplet in relation to gas, m/s

V w :

Water volumetric flowrate, m3/s

V g :

Gas volumetric flowrate, m3/s

S :

Cross-sectional area of the unit, m2


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The work has been supported by European Regional Development Fund project “Individual Heating with Integrated Fog Unit System (IFUS)”


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Correspondence to Vladimirs Kirsanovs.

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Blumberga, D., Priedniece, V., Kalniņš, E. et al. Small scale pellet boiler gas treatment in fog unit. Int J Energy Environ Eng 12, 191–202 (2021).

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  • Air pollution
  • Wet scrubber
  • Performance evaluation
  • Particulate matter
  • Droplet
  • Pellet boiler