Trace elements found in the fuel and in-furnace fine particles collected from 80MW BFB combusting solid recovered fuel

doi:10.1016/j.fuproc.2011.06.023

Fuel Processing Technology

Volume 105, January 2013, Pages 202-211

https://doi.org/10.1016/j.fuproc.2011.06.023 Get rights and content

Abstract

The main fine particle (d_p < 1 μm) forming elements found in combustion gases of anthropogenic waste or biomass fired boilers are typically K, Na and Cl, possibly complemented with S. When these are excluded, in solid recovered fuel (SRF) combustion the main elements were found to be: Ba, Br, Cr, Cu, Fe, Pb, Sb, Sn and Zn. Fine particle composition is presented for 6 different furnace heights of a bubbling fluidized bed (BFB) boiler. As the fine particles are formed of vaporized ash species the experimental results are discussed with the support of thermodynamic equilibrium modeling for estimating the forms of the gaseous elements in the furnace. The occurrence of bromine was found to be similar to chlorine as the main forms of bromine in the furnace were estimated to be KBr(g) and NaBr(g) complemented with CuBr₃(g). It is proposed that the trace elements mentioned originate mainly from plastics and rubber where they are used as production additives, stabilisers, dyes, colorants and flame retardants. Cr, Cu and Zn may originate to a large extent from alloys and other metallic impurities. SEM-EDS analyses carried out for the SRF supports the postulated origin of the elements.

Highlights

► Speciation of vaporised trace elements changes over furnace height. ► Change in speciation is seen in fine particle composition. ► Speciation were estimated by thermodynamic equilibrium modelling. ► Main elements after Na, K, Cl and S were Ba, Br, Cr, Cu, Fe, Pb, Sb, Sn and Zn. ► Bromine is found in the combustion gas aerosols.

Introduction

From a technical point of view, replacing conventional fuels with waste or biomass tends to lead to increased chlorine-induced corrosion rates and to various ash-related problems in boiler furnaces [1], [2], [3]. In waste-fired boilers the main areas of failures, caused by gases and ash forming vapors, are the refractory lining, water walls and superheaters [4]. Regarding biomass combustion, the salts of Na, K, S and Cl are attributed to be the main initiators of ash melting and corrosion [5], [6], [7]. These are also the compounds that are easily vaporized during combustion, forming fine particles [8], [9], [10], [11], [12], [13], [14]. For waste combustion the aforementioned list of main contributors is commonly complemented with Zn and Pb with regard to both high temperature corrosion [15], [16], [17], [18], [19] and fine particle formation [20], [21], [22]. All these elements can be found in SRF, the mentioned metals and halogens particularly in plastic fraction [23], [24], [25]. Regarding bromine the few studies found in the literature indicate that it has a similar influence on the volatilization of the named cations as chlorine [26], [27], [28], [29], [30], [31], [32]. But due to the very specific applications of bromine its concentration in waste fuels can be assumed to be lower [33] than that of chlorine and even negligible in biomass.

In addition to inorganic salts, other bromine bearing species relevant for waste combustion are polybrominated dibenzodioxins (PBDDs) and polybrominated dibenzofurans (PBDFs). Polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are likely human carcinogens which can be formed in thermal processes such as uncontrolled combustion. Analogously PBDDs/Fs can be formed in the presence of bromine. These are by their chemical structure exact homologues to the PCDDs/Fs. The general understanding is that after the formation of PBDDs/Fs bromine is substituted (to varying degree) by chlorine to yield PXDDs/Fs (brominated/chlorinated dibenzodioxins (PXDDs) and brominated/chlorinated dibenzofurans (PXDFs) which are the most common bromine bearing dioxins/furans. In this paper these organohalogens are not discussed further [34], [35], [36], [37].

The objective of this paper is to determine the composition and concentration of fine particle forming matter (aerosols) in different locations of a BFB (bubbling fluidized bed) boiler combusting solid recovered fuel (SRF). The focus is on the inorganic elements, with the largest concentration in aerosols, after excluding K, Na, Cl and S. These were found to be Ba, Br, Cr, Cu, Fe, Pb, Sb, Sn and Zn. The occurrence of these elements in the fuel and combustion gases is discussed. The discussion is supported by thermodynamic equilibrium modeling for the elements.

Section snippets

The BFB plant and fuels used

A detailed description on the BFB boiler and the general arrangements during the experiments can be found in another publication [38]. In the experimental campaign two experimental conditions, (a) and (b), were used in varying the proportions of the three fuels used. The fuels were SRF, spruce bark and wastewater sludge from a paper mill. The SRF-Bark ratio was kept as constant as possible in both experiments, on dry mass basis of 49%–51% and 53%–47% in experiment (a) and (b), respectively. The

Forms and concentration of fine particle forming elements in combustion gases

Fine particle composition and concentration in combustion gases are illustrated in Fig. 2. From the distribution K, Na, Cl and S are excluded. They have been discussed in a previous paper [38]. The mg/Nm³ concentrations are expressed in conditions prevailing at the 2nd pass FTIR, which makes the graphs directly comparable to each other.

With the exception of sample (4b) the total concentration of PM2.5 (particles with aerodynamic diameter d_p < 2.5 μm) is roughly on the same level in every location.

Conclusions

Vaporized ash-forming compounds may form corrosive deposits on boiler waterwalls and superheaters. These ash species form fine particles when combustion gases are cooled down. In this work the main fine particle forming elements after the exclusion of the typical main elements Na, K, Cl and S were found to be Ba, Br, Cr, Cu, Fe, Pb, Sb, Sn and. Zn. These originate mainly from plastics, rubber and alloys in solid recovered fuel. Fe in this work originated mainly from wastewater sludge

Acknowledgements

Financial support from the Finnish Funding Agency for Technology and Innovation (Tekes), Metso Power Oy, Lassila&Tikanoja Oyj, UPM-Kymmene Oyj, the Graduate School in Chemical Engineering (GSCE) and Bioenergy NoE (through contract SES6-CT-2003-502788) is gratefully acknowledged. We are grateful to Stora Enso for providing the BFB plant available for the experimental work and Juergen Vehlow for comments and supporting data. We thank Raili Taipale, Hannu Vesala, Marko Räsänen, Kauko Tormonen and

References (85)

R.W. Bryers
Fireside slagging, fouling, and high-temperature corrosion of heat-transfer surface due to impurities in steam-raising fuels
Prog. Energy Combustion Sci.
(1996)
L.L. Baxter et al.
The behavior of inorganic material in biomass-fired power boilers: field and laboratory experiences
Fuel Process Technol.
(1998)
T.R. Miles et al.
Boiler deposits from firing biomass fuels
Biomass Bioenergy
(1996)
L.A. Hansen et al.
Influence of deposit formation on corrosion at a straw-fired boiler
Fuel Process Technol.
(2000)
H.P. Nielsen et al.
The implications of chlorine-associated corrosion on the operation of biomass-fired boilers
Prog. Energy Combustion Sci.
(2000)
K.A. Christensen et al.
The formation of submicron aerosol particles, HCl and SO₂ in straw-fired boilers
J. Aerosol Sci.
(1998)
K.A. Christensen et al.
The combustion of straw : submicron aerosol particles and gas pollutants
J. Aerosol Sci.
(1995)
T. Valmari et al.
Aerosol dynamics in circulating fluidised bed combustion of biomass
J. Aerosol Sci.
(1995)
J. Kurkela et al.
Fly ash particle formation in fluidized bed combustion of wood-based fuels
J. Aerosol Sci.
(1998)
M. Becidan et al.
Corrosion in waste-fired boilers: a thermodynamic study
Fuel
(2009)

E. Kauppinen et al.

Mass and metal size distributions of municipal waste combustion aerosols

J. Aerosol Sci.

(1986)

Y. Ménard et al.

Thermodynamic study of heavy metals behaviour during municipal waste incineration

Process Saf. Environ. Prot.

(2006)

R. Luijk et al.

The role of bromine in the de novo synthesis in a model fly ash system

Chemosphere

(1994)

J. Ebert et al.

Formation of PBDD/F from flame-retarded plastic materials under thermal stress

Environ. Int.

(2003)

R. Weber et al.

Relevance of BFRs and thermal conditions on the formation pathways of brominated and brominated–chlorinated dibenzodioxins and dibenzofurans

Environ. Int.

(2003)

P. Vainikka et al.

Bromine as an ash forming element in a fluidised bed boiler combusting solid recovered fuel

Fuel

(2011)

L. Sørum et al.

On the fate of heavy metals in municipal solid waste combustion. Part II. From furnace to filter

Fuel

(2004)

C.W. Bale et al.

FactSage thermochemical software and databases — recent developments

Calphad

(2009)

P. Vainikka et al.

High temperature corrosion of boiler waterwalls induced by chlorides and bromides. Part 1: occurrence of the corrosive ash forming elements in a fluidised bed boiler co-firing solid recovered fuel

Fuel

(2011)

H.J. Ollila et al.

SEM–EDS characterization of inorganic material in refuse-derived fuels

Fuel

(2006)

L. Sørum et al.

On the fate of heavy metals in municipal solid waste combustion Part I: devolatilisation of heavy metals on the grate

Fuel

(2003)

M. Becidan et al.

Corrosion in waste-fired boilers: a thermodynamic study

Fuel

(2009)

A. Zahs et al.

Chloridation and oxidation of iron, chromium, nickel and their alloys in chloridizing and oxidizing atmospheres at 400–700 °C

Corros. Sci.

(2000)

J. Latva-Somppi et al.

The ash formation during co-combustion of wood and sludge in industrial fluidized bed boilers

Fuel Process Technol.

(1998)

M. Alaee et al.

An overview of commercially used brominated flame retardants, their applications, their use patterns in different countries/regions and possible modes of release

Environ. Int.

(2003)

V.S. Rotter et al.

Material flow analysis of RDF-production processes

Waste Manage.

(2004)

A.I. Balabanovich et al.

Thermal decomposition behavior of 1,2-bis-(2,4,6-tribromophenoxy)ethane

J. Anal. Appl. Pyrolysis.

(2003)

V.J. Sundar et al.

Cleaner chrome tanning — emerging options

J. Clean. Prod.

(2002)

K. Nakamura et al.

The origin and behavior of lead, cadmium and antimony in MSW incinerator

Waste Manage.

(1996)

A.J. Pedersen et al.

Release to the gas phase of metals, S and Cl during combustion of dedicated waste fractions

Fuel Process Technol.

(2010)

F. Paoletti et al.

Fate of antimony in municipal solid waste incineration

Chemosphere

(2001)

W. Hesseling et al.

Efficiency increase of waste-to-energy plants evaluation of experience with boiler corrosion and corrosion reduction

(2003)

K. Salmenoja, Field and laboratory studies on chlorine-induced superheater corrosion in boilers fired with biofuels,...

K.A. Christensen

The formation of submicron particles from the combustion of straw, Lyngby Ph.D. thesis

(1995)

T. Lind et al.

The effect of chlorine and sulfur on fine particle formation during co-combustion of bark and sludge

J. Aerosol Sci.

(2004)

M. Jöller et al.

Modeling of aerosol formation during biomass combustion in grate furnaces and comparison with measurements

Energy Fuels

(2005)

I.G. Wright et al.

Assessment of factors affecting boiler tube lifetime in waste-fired steam generators: new opportunities for research and technology development

(1996)

M. Spiegel

Salt melt induced corrosion of metallic materials in waste incineration plants

Mater. Corrosion

(1999)

M. Sánchez-Pastén et al.

High temperature corrosion of metallic materials in simulated waste incineration environments at 300–600 °C

Mater. Corrosion

(2006)

D. Bankiewicz et al.

High-temperature corrosion of superheater tube materials exposed to zinc salts

Energy Fuels

(2009)

A.J. Pedersen et al.

A full-scale study on the partitioning of trace elements in municipal solid waste incineration—effects of firing different waste types

Energy Fuels

(2009)

H. Zweifel

Plastics additives handbook

(2000)

Cited by (11)

A comparison of PM exposure related to emission hotspots in a hot and humid urban environment: Concentrations, compositions, respiratory deposition, and potential health risks
2017, Science of the Total Environment
Particle number concentration, particle size distribution, and size-dependent chemical compositions were measured at a bus stop, alongside a high way, and at an industrial site in a tropical city. It was found that the industry case had 4.93 × 10⁷–7.23 × 10⁷ and 3.44 × 10⁴–3.69 × 10⁴ #/m³ higher concentration of particles than the bus stop and highway cases in the range of 0.25–0.65 μm and 2.5–32 μm, respectively, while the highway case had 6.01 × 10⁵ and 1.86 × 10³ #/m³ higher concentration of particles than the bus stop case in the range of 0.5–1.0 μm and 5.0–32 μm, respectively. Al, Fe, Na, and Zn were the most abundant particulate inorganic elements for the traffic-related cases, while Zn, Mn, Fe, and Pb were abundant for the industry case. Existing respiratory deposition models were employed to analyze particle and element deposition distributions in the human respiratory system with respect to some potential exposure scenarios related to bus stop, highway, and industry, respectively. It was shown that particles of 0–0.25 μm and 2.5–10.0 μm accounted for around 74%, 74%, and 70% of the particles penetrating into the lung region, respectively. The respiratory deposition rates of Cr and Ni were 170 and 220 ng/day, and 55 and 140 ng/day for the highway and industry scenarios, respectively. Health risk assessment was conducted following the US EPA supplemented guidance to estimate the risk of inhalation exposure to the selected elements (i.e. Cr, Mn, Ni, Pb, Se, and Zn) for the three scenarios. It was suggested that Cr poses a potential carcinogenic risk with the excess lifetime cancer risk (ELCR) of 2.1–98 × 10^− 5 for the scenarios. Mn poses a potential non-carcinogenic risk in the industry scenario with the hazard quotient (HQ) of 0.98. Both Ni and Mn may pose potential non-carcinogenic risk for people who are involved with all the three exposure scenarios.
Ash contents and ash-forming elements of biomass and their significance for solid biofuel combustion
2017, Fuel
Inorganic matter and some ash-forming elements of biomass may cause numerous technological and environmental problems during biomass processing. Therefore, an extended overview of the ash contents and ash-forming elements of biomass and their significance for solid biofuel combustion was conducted based on reference peer-reviewed data plus own investigations. Initially, some general considerations such as current bioenergy situation and different aspects related to biomass use as biofuels, as well as some common issues concerning the main advantages and disadvantages of ash contents and ash-forming elements of biomass are discussed. Then, definition, specification, terminology clarification and composition related to inorganic and mineral matter of biomass and biomass ash (BA) are considered. Further, the contents and concentration/depletion trends of ash (for 532 biomass varieties) and 12 ash-forming elements based on traditional and complete ash analysis of Si, Ca, K, P, Al, Mg, Fe, S, Na and Ti oxides (141 BA varieties) plus elemental Cl (87 BA varieties) and Mn (156 BA varieties) were characterized. The correlations and associations among the ash yields and contents of ash-forming elements of natural biomass (127 biomass and BA varieties) were also identified using the present database. Finally, the origin and significance of ash-forming elements and their associations established in biomass, namely (1) Si – Al – Fe – Ti; (2) Ca – Mg – Mn; and (3) K – P – S – Cl – Na were described and the benefits and obstacles of these associations for biofuel combustion were evaluated. It was found that the high ash yields and contents of some ash-forming elements such as Cl, K, Na, P, S and some other elements with unfavorable modes of element occurrences (chlorides, sulphates, carbonates, oxalates, nitrates and some oxyhydroxides, phosphates and amorphous material) in biomass and BA may provoke the most critical technological and environmental challenges during biomass processing and especially during biomass thermochemical conversion.
Chemical composition, character and reactivity of renewable fuel ashes
2016, Fuel
The paper is focused on the characterization of renewable fuel ashes and their impact on fouling and slagging during combustion. Biomass (A1) and sewage sludge (A2, A3) ashes were investigated for characterization of their corrosive properties. The chemical and phasemineral composition of ashes were studied using a variety of analytical techniques including XRF, ICP-MS, XRD, SEM–EDS, and the ash fusion characteristics by using a thermal microscope. The slagging and fouling indices, as well as thermal conductivity, were calculated and the sintering properties were predicted. The studied ashes had different concentrations of the main chemical compounds and mineral phases. The XRF results showed that CaO, SiO₂, K₂O, MgO, P₂O₅ and Al₂O₃ are the main compounds of A1 and A3 ashes, whereas Na₂O and SO₃ dominated in A2. Consequently, SEM images showed surface differences between ash particles. Phase analyses indicated the existence of corrosive phases containing potassium and sodium K₂Ca(CO₃)₂, KAlSi₂O₆, KCl, NaAlSiO₄ (A1) and Na₂SO₄, NaCl (A2). Such compounds can decrease the sintering temperature due to formation of low temperature eutectics. The lowest fusion temperatures below 1000 °C were detected from the sewage sludge ash A2 and above 1200 °C from A1 and A2 with high Ca, Si and Al contents.
Searching for a robust strategy for minimizing alkali chlorides in fluidized bed boilers during burning of high SRF-energy-share fuel
2015, Fuel
Citation Excerpt :
This sludge is rich in calcium from paper fillers and coating used during the paper manufacturing. The wastewater treatment facility uses around 30–40 kg of iron(III) sulfate per ton of dry sludge as flocculants and aluminum(III) sulfate for pH control [6]. The gross calorific value (mean = 21 ± 0.7 MW/kg, d) and the concentration of C, H, O in the pure fuels do not vary significantly.
To meet the increasing volume of waste to be treated via energy recovery, high SRF-energy-share fuel is being fired in conventional waste-to-energy facilities. In this work, corrosion related risk during firing of 70 e-% share (target fuel) is studied and compared against the base case fuel containing 50 e-% share. Cl and S concentration is highest in the target fuel as a direct result of increasing the proportion of SRF in the fuel mixture. Br, Zn and Pb showed the same trend. Meanwhile, the concentration of Na, K, Al and Si are highly dependent on the type of the SRF fired. The corrosion risk of the base and target fuels are analyzed using the composition of the fine aerosol fraction and deposit samples measured near the vicinity of the superheater. Surprisingly aerosols for the target fuel are less risky – having less Cl and more S, than that of the base fuel. The effects of sulfur based additives – elemental sulfur and sulfate injection, and fuel substitution on the risk of superheater corrosion are likewise analyzed. All these strategies can reduce the concentration of Cl in the aerosols, however it is concluded that sulfate injection is considered as a robust strategy for mitigating alkali chloride formation. Sulfate injection is able to reduce Cl in the aerosols and deposits regardless of the quality of the fuel mixture. Robust strategies are important in ensuring the boiler performance during high SRF-energy share firing. An attempt of linking the quality of the deposits and the properties of the flue gas and aerosols around the superheater using partial least squares regression is also presented.
Towards controlling PCDD/F production in a multi-fuel fired BFB boiler using two sulfur addition strategies. Part I: Experimental campaign and results
2014, Fuel
Citation Excerpt :
PVC based packaging plastics have been excluded during the collection and preparation of the SRF. In the SRF plant, materials are homogenized to 50–100 mm particle size and magnetic materials are separated, SRF is transported to the BFB in wrapped bales or fluffs [39]. The proportions, in percentage energy share, of the fuels fired are given in Table 1.
Levels of PCDD/F production in a 140 MW_th bubbling fluidized bed boiler were measured. The boiler uses solid recovered fuel, bark and sludge. Homologue distribution patterns suggest the de novo mechanism is the main pathway for the generation of dioxin and furans in the post combustion zones of the boiler. Two modes of sulfur addition were tested to induce the deactivation of Cu which has been identified as the prime catalyst of this mechanism. First, S-pellet promoted Cu sulfation as supported by aerosol sampling data and resulted in a decrease in PCDD/F levels. The second approach was adding sulfur through peat; this resulted in an increase in PCDD/F concentration. Factors such as high Cu content in the SRF-peat-sludge fuel mixture and reduced volatilization of Cu may have contributed to the said increase. For all test cases, phase redistribution of PCDD/F was observed in the electrostatic precipitator favoring more gaseous PCDD/F at the outlet. The homologue distribution pattern did not change in the flue gas path, suggesting that further synthesis and/or chlorination in the stream were minimized. There is however evidence for subsequent reactions happening in the ESP fly ash. The homologue distribution pattern in the latter was different from that of the flue gas, and more highly chlorinated PCDD/Fs were present. Furthermore, the ratio of PCDD and PCDF was different from that of the samples in the flue gas path.
Trace element concentrations and associations in some biomass ashes
2014, Fuel
Citation Excerpt :
It was highlighted in the above overviews that despite the low contents of trace elements (TEs) in biomass and BA they have very important ecological and technological impacts during sustainable utilization of solid biofuels and their products. Numerous studies related to TE concentrations in biomass and BA and their behaviour during thermo-chemical conversion including combustion, pyrolysis, gasification and liquefaction, as well as co-combustion, co-pyrolysis and co-gasification of coal with biomass have been performed worldwide ([7–52] among others). Consequently, significant data for contents of TEs in biomass, biochar and BAs such as low-temperature and high-temperature laboratory ashes and industrial bottom ashes, slags and fly ashes, along with behaviour of TEs during thermal treatment of different biomass varieties have been generated.
The phase-mineral and chemical composition of biomass ashes (BAs) produced from 8 biomass varieties, namely beech wood chips, corn cobs, marine macroalgae, plum pits, rice husks, switchgrass, sunflower shells and walnut shells, was studied for the elucidation of trace element (TE) concentrations and their associations. For that purpose the contents of 60 major, minor and TEs in high-temperature BAs produced at 500 °C were determined by inductively coupled plasma and laser ablation mass spectrometry, as well as scanning electron microscopy equipped with an energy dispersive X-ray analyser. The phase-mineral composition of BAs was studied by light microscopy, powder X-ray diffraction, differential-thermal and thermo-gravimetric analyses plus some leaching, precipitation, ashing (500–1500 °C) and other procedures. The composition and properties of the biomass fuels studied and their ashes were characterized, and some general considerations about TEs in them are described. An elucidation of the TE contents in BAs and their ash types was conducted and a comparison with coal ashes was also performed. An explanation of the correlations and clarification of the associations of TEs with major and minor elements, as well as with different constituents (organic matter, inorganic matter, cellulose, hemicellulose, lignin, inorganic amorphous matter, silicates, phosphates, carbonates, oxides, hydroxides, sulphates and chlorides) in biomass and BAs are given. It was revealed that the greatest ecological challenges related to some TEs in biomass and BA include their: (1) high concentrations; (2) unfavourable modes of occurrence; (3) enhanced volatilization and limited retention and capture performance during biomass combustion; and (4) increased leaching behaviour during biomass and BA processing or storage.

View all citing articles on Scopus

¹: Vapor Finland Oy, Messipohjantie 20, 90520 Oulu, Finland.

View full text

Trace elements found in the fuel and in-furnace fine particles collected from 80MW BFB combusting solid recovered fuel

Abstract

Highlights

Introduction

Section snippets

The BFB plant and fuels used

Forms and concentration of fine particle forming elements in combustion gases

Conclusions

Acknowledgements

Prog. Energy Combustion Sci.

Fuel Process Technol.

Biomass Bioenergy

Fuel Process Technol.

Prog. Energy Combustion Sci.

J. Aerosol Sci.

J. Aerosol Sci.

J. Aerosol Sci.

J. Aerosol Sci.

Fuel

J. Aerosol Sci.

Process Saf. Environ. Prot.

Chemosphere

Environ. Int.

Environ. Int.

Fuel

Fuel

Calphad

Fuel

Fuel

Fuel

Fuel

Corros. Sci.

Fuel Process Technol.

Environ. Int.

Waste Manage.

J. Anal. Appl. Pyrolysis.

J. Clean. Prod.

Waste Manage.

Fuel Process Technol.

Chemosphere

Efficiency increase of waste-to-energy plants evaluation of experience with boiler corrosion and corrosion reduction

The formation of submicron particles from the combustion of straw, Lyngby Ph.D. thesis

The effect of chlorine and sulfur on fine particle formation during co-combustion of bark and sludge

J. Aerosol Sci.

Modeling of aerosol formation during biomass combustion in grate furnaces and comparison with measurements

Energy Fuels

Assessment of factors affecting boiler tube lifetime in waste-fired steam generators: new opportunities for research and technology development

Salt melt induced corrosion of metallic materials in waste incineration plants

Mater. Corrosion

High temperature corrosion of metallic materials in simulated waste incineration environments at 300–600 °C

Mater. Corrosion

High-temperature corrosion of superheater tube materials exposed to zinc salts

Energy Fuels

A full-scale study on the partitioning of trace elements in municipal solid waste incineration—effects of firing different waste types

Energy Fuels

Plastics additives handbook