Effects on NOx and SO2 Emissions During Co-Firing of Coal with Woody Biomass in Air Staging and Reburning

Co-firing coal with different types of biomass is increasingly being applied in thermal power plants in Europe. The main motive for the use of biomass as the second fuel in coal-fired power plants is the reduction of CO2 emissions, and related financial benefits in accordance with the relevant International regulations and agreements. Likewise, the application of primary measures in the combustion chamber, which also includes air staging and/or reburning, results in a significant reduction in emission of polluting components of flue gases, in particular NOx emissions. In addition to being efficient and their application to new and future thermoblocks is practically unavoidable, their application and existing conventional combustion chamber does not require significant constructional interventions and is therefore relatively inexpensive. In this work results of experimental research of co-firing coals from Middle Bosnian basin with waste woody biomass are presented. Previously formed fuel test matrix is subjected to pulverized combustion under various temperatures and various technical and technological conditions. First of all it refers to the different mass ratio of fuel components in the mixture, the overall coefficient of excess air and to the application of air staging and/or reburning. Analysis of the emissions of components of the flue gases are presented and discussed. The impact of fuel composition and process temperature on the values of the emissions of components of the flue gas is determined. Additionally, it is shown that other primary measures in the combustion chamber are resulting in more or less positive effects in terms of reducing emissions of certain components of the flue gases into the environment. Thus, for example, the emission of NOx of 989 mg/ measured in conventional combustion, with the simultaneous application of air staging and reburning is reduced to 782 mg/, or by about 21%. The effects of the primary measures applied in the combustion chamber are compared and quantified with regard to conventional combustion of coals from Middle Bosnian basin.Article History: Received: November 5th 2017; Revised: Januari 6th 2018; Accepted: February 1st 2018; Available onlineHow to Cite This Article: Hodžić, N., Kazagić, A., and Metović, S. (2018) Experimental Investigation of Co-Firing of Coal with Woody Biomass in Air Staging and Reburning. International Journal of Renewable Energy Development, 7(1), 1-6.https://doi.org/10.14710/ijred.7.1.1-

Co-firing Bosnian coals with woody biomass: Experimental studies on a laboratory-scale furnace and 110 MWe power unit

This paper presents the findings of research into cofiring two Bosnian cola types, brown coal and lignite, with woody biomass, in this case spruce sawdust. The aim of the research was to find the optimal blend of coal and sawdust that may be substituted for 100% coal in large coal-fired power stations in Bosnia and Herzegovina. Two groups of experimental tests were performed in this study: laboratory testing of co-firing and trial runs on a large-scale plant based on the laboratory research results. A laboratory experiment was carried out in an electrically heated and entrained pulverized-fuel flow furnace. Coal-sawdust blends of 93:7% by weight and 80:20% by weight were tested. Co-firing trials were conducted over a range of the following process variables: process temperature, excess air ratio and air distribution. Neither of the two coal-sawdust blends used produced any significant ash-related problems provided the blend volume was 7% by weight sawdust and the process temperature did not exceed 1250ºC. It was observed that in addition to the nitrogen content in the co-fired blend, the volatile content and particle size distribution of the mixture also influenced the level of NOx emissions. The brown coal-sawdust blend generated a further reduction of SO2 due to the higher sulphur capture rate than for coal alone. Based on and following the laboratory research findings, a trial run was carried out in a large-scale utility - the Kakanj power station, Unit 5 (110 MWe), using two mixtures; one in which 5%/wt and one in which 7%/wt of brown coal was replaced with sawdust. Compared to a reference firing process with 100% coal, these co-firing trials produced a more intensive redistribution of the alkaline components in the slag in the melting chamber, with a consequential beneficial effect on the deposition of ash on the superheater surfaces of the boiler. The outcome of the tests confirms the feasibility of using 7%wt of sawdust in combination with coal without risk to the efficiency of the unit, its combustion process and with the benefits of emissions reductions. Furthermore, they show that no modification to the existing coal transport system and boiler equipment is necessary to achieve this outcome

A novel index for the study of synergistic effects during the co-processing of coal and biomass

In this study, synergistic interaction between coal and biomass and its intensity were investigated systematically using a low rank coal and its blends with different biomass samples at various blending ratios. The catalytic effects of minerals originated from biomass were also studied. It was found that some of the minerals existing in the ash derived from oat straw catalysed the combustions process and contributed to synergistic interactions. However, for the coal and rice husk blends, minimal improvements were recorded even when the biomass and coal blending ratio was as high as 30 wt%. Biomass volatile also influenced the overall combustion performance of the blends and contributed to synergistic interactions between the two fuels in the blends. Based on these findings, a novel index was formulated to quantify the degree of synergistic interactions. This index was also validated using data extracted from literature and showed satisfactory correlation coefficients. It was found that at a blending ratio of 30 wt% oat straw in the blend, the degree of synergistic interaction between coal and oat straw showed an additional SF value of 0.25 with non-catalytic and catalytic synergistic effect contributing 0.16 (64%) and 0.09 (36%) respectively. This index could be used in the selection of proper biomass and proper blending ratio for co-firing at coal-fired power stations aiming at improving the combustion performance of poor quality coals via enhancing synergistic interactions during co-processing

Fuel additive technology - NOx reduction, combustion efficiency and fly ash improvement for coal fired power stations

Fuel additive technology is based on the use of a solid, fuel additive (iron, aluminium, calcium and silicon based oxides), to reduce NOx emission, improve the quality of fly ash and result in 1-3% coal savings for pulverised coal combustion. The findings in this study have been mainly based on extensive experimentation on 100 kWth down fired-combustion test facility (CTF) and partially on a commercial 260 tons/h steam producing water tube pf boiler. International Innovative Technologies (IIT) developed this additive based technology for the combined effect of reducing NOx from the combustion of hydrocarbon fuels (mainly coal) and more specifically to improve the combustion process of fossil fuels resulting in an ash by product with improved loss on ignition and lower carbon content. The improvement in the combustion thermal efficiency of the commercial 260 tons/h steam producing boiler has been calculated as per the direct calculation method of EN BS12952-15:2003 standard. © 2014 Elsevier Ltd. All rights reserved

Evigheten venter : en studie av en pinsemenighet på Sørlandet

Oppgaven tar utgangspunkt i en karismatisk menighet på Sørlandet. Menigheten er en av landets største, og har møter hver dag. Den er en veletablert menighet som forsøker å starte opp andre menigheter i lokalmiljøet, men også i utlandet. Oppgaven ser på hvordan medlemmene bruker ritualer under sin tilbedelse, hvordan ritualer brukes for å forstå verden står sentralt. Gjennom rituell praksis i menigheten uttrykker medlemmene idealer om hvordan karismatikere skal leve og ordne sine liv. Det er et skille mellom ideal og praksis når det kommer til forestillingen om egalitet, som står sterkt i karismatiske miljøer. Jeg har argumentert for at praksisen til medlemmene har ritualisert forventningene til det spontane under ritualer, og hvordan den ritualiserte praksisen har vært med på å danne en karismatisk habitus. Gjennom at menigheten arrangerer aktiviteter hver dag, bekrefter medlemmene den åndelige aktiviteten og nærværet til det spirituelle. Den karismatiske habitus legger fundamentet for en radikalisering av karisma. Jeg argumenterer for at radikaliseringen av karisma bekrefter og forsterker menighetens åndsliv og medlemmenes karismatiske habitus, og hvordan menigheten gjennom dette har blitt en institusjon, men gjennom en radikalisering av karisma, bevarer et minne om communitas. Målet mitt er å si noe om karismatiske menigheter generelt, og mer spesifikt noe om medlemmene og menigheten hvor feltarbeidet ble gjort

Jeg kom, jeg så, jeg vant: Gevinstrealisering, innføring og digital transformasjon i offentlig sektor

Master´s thesis in management (ORG917

Co-Combustion of Low-Rank Coal with Woody Biomass and Miscanthus: An Experimental Study

This paper presents a research on ash-related problems and emissions during co-firing low-rank Bosnian coals with different kinds of biomass; in this case woody sawdust and herbaceous energy crops Miscanthus. An entrained-flow drop tube furnace was used for the tests, varying fuel portions at a high co-firing ratio up to 30%wt woody sawdust and 10%wt Miscanthus in a fuel blend. The tests were supposed to optimize the process temperature, air distribution (including OFA) and fuel distributions (reburning) as function of SO2 and NOx emissions as well as efficiency of combustion process estimated through the ash deposits behaviors, CO emissions and unburnt. The results for 12 co-firing fuel combinations impose a reasonable expectation that the coal/biomass/Miscanthus blends could be successfully run under certain conditions not producing any serious ash-related problems. SO2 emissions were slightly higher when higher content of woody biomass was used. Oppositely, higher Miscanthus percentage in the fuel mix slightly decreases SO2 emissions. NOx emissions generally decrease with an increase of biomass co-firing rate. The study suggests that co-firing Bosnian coals with woody sawdust and Miscanthus shows promise at higher co-firing ratios for pulverized combustion, giving some directions for further works in co-firing similar multi-fuel combinations