Briquet burning analysis

According to our order, the Environment Control Laboratory of Riga Technical University’s Institute of Energy Systems and Environment (IESE) carried out a research effort to analyse the combustion parameters of different densities of wood fuels briquettes, with a view to clarifying the impact of the density of fuels on their combustion parameters.

At what pressure does material compress? Does this affect the quality of briquettes? Seems quite logical – the higher the pressure, the higher the density – the better burning, but is it?

Therefore, in cooperation with the Riga Technical University Institute for Environmental Protection and Heating Systems, we carried out a study showing how much pressure changes in the settings of the briquettes plant affect briquettes burning.

Purpose of work

Effect of the density of fuel briquettes on their combustion parameters.

In the course of the work, the following analyses and calculations were carried out:

1. Fuel analysis:
• humidity of the material;
• the highest and lowest burning heat;
• energy density.

2. Combustion analysis:
• concentrations of CO, NOx, O2 and CO2 in the flue gases;
• concentration of particulate matter in the flue gases;
• the temperature of the flue gas.

3. Estimates:
• breakdown of heat losses;
• efficiency of the stove.

Original material for analysis.

Fuels or briquettes were manufactured on RUF hydraulic press, RB440 model, serial No. 1150, with three different main cylinder pressures:

• 180 Bars - Test No 1;
• 220 Bars - Test No 2;
• 250 Bars - Test No 3.

The briquettes are rectangular, with a cross section of 60x150 mm.

Material - oak sawdust from parquet production.

Three roughly equal mass briquettes were burned in each test.

Analysis and calculation summary table

Conclusions

All three briquette samples are made of a homogeneous material showing the equivalent humidity of all three samples (6,38-6,48%), ash content (0.61-0.68%) and the lowest combustion heat (16,85 - 16,93 MJ/kg).

1. Increasing the pressing pressure from 180 to 250 Bar increases:

• brunch capacity of 858,9 to 908,9 kg/m³;
• briquettes energy density from 14,51 to 15,31 GJ/m³.

2. Increasing briquettes and energy density:

• the duration of burning is reduced from 1,15 to 0,9 hours due to increased burning;
• reduce the average CO emissions during the smoke gas test from 22300 to 14477 mg/Nm³ (1,54 times);
• the stove power is increasing from 6,97 to 9,58 kW (1,37 times);
• combustion efficiency increases from 67.0% to 72.3%.

So, in short, pressure has an impact on the quality of the briquettes, or on their combustion parameters.

A detailed research report can be read here: Brikešu degšanas analīzes atskaite