Biomass Boilers Research Papers - Academia.edu (original) (raw)

More than seventy district heating (DH) plants based on biomass are operating in South Tyrol (Italy) and most of them supply heat to residential districts. Almost 20% of them are cogenerative systems, thus enabling primary energy savings with respect to the separate production of heat and power. However, the actual performance of these systems in real operation can considerably differ from the nominal one. The main objectives of this work are the assessment of the energy performance of a biomass boiler coupled with an Organic Rankine Cycle (i.e., ORC) generator under real operating conditions and the identification of its potential improvements. The fluxes of energy and mass of the plant have been measured onsite. This experimental evaluation has been supplemented with a thermodynamic model of the ORC generator, calibrated with the experimental data, which is capable to predict the system performance under different management strategies of the system. The results have highlighted that a decrease of the DH network temperature of 10 °C can improve the electric efficiency of the ORC generator of one percentage point. Moreover, a DH temperature reduction could decrease the main losses of the boiler, namely the exhaust latent thermal loss and the exhaust sensible thermal loss, which account for 9% and 16% of the boiler input power, respectively. The analysis of the plant has pointed out that the ORC pump, the flue gases extractor, the thermal oil pump and the condensation section fan are the main responsible of the electric self-consumption. Finally, the negative effect of the subsidisation on the performance of the plant has been discussed.

- by
- •
- Organic rankine cycle, CHP, Biomass Boilers

Biomass plays an important role in the world primary energy supplies, currently providing 14% of the world’s primary energy needs and being the fourth largest contributor following coal, oil and natural gas. Over the past decade, domestic biomass heating has received more governmental and public supports than ever before in many developed countries, such as the UK. Although biomass combustion releases some combustion pollutants, biomass is renewable and produces little net CO2 emissions to the atmosphere. Owing to the low sulphur and low nitrogen contents of many biomass materials, substituting biomass for fossil fuels, particularly coal, can reduce SOx and NOx emissions. This study investigated flue gas emissions, particularly carbon monoxide and nitrogen oxides, of a
domestic biomass boiler under various operating conditions. The biomass boiler used in this study satisfies the current EU regulation (EN 303-05) on emissions of domestic biomass boilers. Emissions of the boiler had been measured not only under normal combustion conditions, but also under ‘idle’ combustion conditions when the boiler was not in but was ready for full operation. The experimental results are analysed and presented in this paper.

- by Hao Liu
- •
- Biomass Boilers

KCl-induced high-temperature corrosion behavior of four HVAF-sprayed Ni-based coatings (Ni21Cr, Ni5Al, Ni21Cr7Al1Y and Ni21Cr9Mo) under KCl deposit has been investigated in ambient air at 600°C up to 168 h. The coatings were deposited onto 16Mo3 steel-a widely used boiler tube material. Uncoated substrate, 304L and Sanicro 25 were used as reference materials in the test environment. SEM/EDS and XRD techniques were utilized to characterize the as-sprayed and exposed samples. The results showed that the small addition of KCl significantly accelerated degradation to the coatings. All coatings provided better corrosion resistance compared to the reference materials. The alumina-forming Ni5Al coating under KCl deposit was capable of forming a more protective oxide scale compared to the chromia-forming coatings as penetration of Cl through diffusion paths was hindered. Both active corrosion and chromate formation mechanisms were found to be responsible for the corrosion damages. The corrosion resistance of the coatings based on the microstructure analysis and kinetics had the following ranking (from the best to worst): Ni5Al [ Ni21Cr [ Ni21Cr7Al1Y [ Ni21Cr9Mo.

- by Reza Jafari
- •
- Materials Engineering, Mechanical Engineering, Microstructure, Thermal Spray Coating

- by Reza Jafari
- •
- Microstructure, Thermal Spray Coating, Corrosion Engineering, Corrosion