Article pubs.acs.org/EF
Straw Combustion: Pilot and Laboratory Studies on a Straw-Fired Grate Boiler Krystyna Kubica,† Marcin Jewiarz,*,‡ Robert Kubica,§ and Andrzej Szlęk† †
Institute of Thermal Technology, Silesian University of Technology, Konarskiego 22, 44-100 Gliwice, Poland Department of Mechanical Engineering and Agrophysics, Agricultural University in Krakow, Balicka 120, 30-149 Kraków, Poland § Department Chemical Engineering and Process Design, Silesian University of Technology, Ksiȩdza Marcina Strzody 7, 44-100 Gliwice, Poland ‡
ABSTRACT: This paper presents the results of work carried out by the project “Development of the Methods for Pretreatment of Agricultural Biomass Used for Production of Energy” supported by the national program Innovative Economy. The research includes the analysis of several factors related to utilization of straw for energy purposes. The main points of interest were a decrease of ash-sintering potential using inorganic additives, application of alloy steels in boiler construction, and leaching of mineral compounds to minimize corrosion risk. This paper also provides a review of the results of experiments, including the combustion of two different types of straw in a grate boiler, with a capacity of 3.5 MWth. The testing was carried out for rape and wheat straw with and without the addition of kaolin. The energy balance and emission factors of pollutants [CO, NOx, SO2, and total suspended particles (TSP)] were derived. The obtained results show that application of mineral additives gives satisfactory results in terms of the increase of the ash-softening point. High-quality materials could be used in the manufacturing of the boiler parts exposed to a corrosive environment.
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INTRODUCTION Biomass is supposed to become a major renewable energy source in Poland, with regard to both useful heat and electricity. This type of fuel is sourced mainly from forestry, agriculture, and energy crops. One of the most underestimated biomass sources in Poland is cereal straw. The annual surplus in production, which can be used for energy purposes, is estimated to be about 10 million tons.1,2 This amount of straw could substitute about 7 million tons of hard coal used in the energy sector. Straw can be used as a fuel in three main forms: as chaff and bales and in compacted form of pellets and briquettes. Effective utilization of cereal straw leads to many technological and economical barriers. Economic analysis shows that 100 km is the distance, above which transportation of straw is unviable. This favors utilization of the straw near the place of its collection.3 In this term, the most effective way of utilization is the combustion in small- and medium-scale, municipal heating plants. The main technological issue is the substantial variability of chemical and physical parameters, e.g., lower heating value (LHV) and moisture content. On the other hand, low bulk density makes this type of fuel very demanding material in view of storage. Furthermore, a usually high concentration of chlorine and alkalis promotes corrosion in heat exchangers of the boilers. That is why effective and clean combustion of straw requires modern techniques and materials to be applied. It is also important to use physical and/or chemical means to prevent corrosion.4 This paper presents the results of complex studies, which were divided into four main parts. First were laboratory-scale tests on a leaching process, in which diminution of chlorine and alkalis in straw was investigated. Next, several additives were proposed, to prevent the formation of corrosive deposits in the heat exchanger. The laboratory experiments included the use of © XXXX American Chemical Society
kaolin, halloysite, limestone, and spent bleaching earth (SBE). Next, the selected additive was used during tests carried out on a 3.5 MWth straw-fired boiler, installed in a municipal heating plant in Lubań (Lower Silesia). In addition to that, there was also instrumental investigation on the corrosion potential of ash deposits formed during the boiler operation. Different types of construction materials were subjected to testing. Straw as Fuel. Straw is a very demanding type of fuel, with diversified physical properties and composition. Other challenging issues for boiler designers and manufacturers as well as its users are corrosion risk and low ash fusion temperatures. Extensive studies on the process of straw combustion show that the biggest amount of corrosive deposits is formed in the convection part of the boiler heat exchangers.4−6 Chlorine and potassium, which are usually present in the straw at large quantities, are mainly responsible for the phenomenon of slagging and the formation of mentioned deposits. Fly ash from the combustion of straw contains more than 20% of unburnt carbon. On the other hand, it contains a lot of potassium and chlorine compounds.4−7 Almost 40% of chlorine leaves the boiler in a condensed form as KCl, not appearing in the exhaust gases. The high amount of alkali metals in the straw causes a low sintering temperature of ash, which varies in the range of 700− 900 °C. The ash-softening temperature is usually below 1000 °C. Full melting occurs often below 1200 °C.8 This characteristic of ash produced by straw combustion can cause Special Issue: International Symposium on Combustion Processes Received: November 14, 2015 Revised: January 6, 2016
A
DOI: 10.1021/acs.energyfuels.5b02693 Energy Fuels XXXX, XXX, XXX−XXX
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Energy & Fuels the phenomenon of agglomeration of the fuel in the bed, called slagging. For straw combustion, agglomeration is caused by separate, viscous, and partially melted particles of ash and not by the viscous alkaline calcium silicate layer, which, in the case of wood combustion, is gradually formed on the particles.9 The molten ash particles are mainly composed of potassium chloride and potassium silicate, which are formed in the reaction between potassium and silica, present in the ash.10,11 Use of the straw for energy production is difficult in large industrial boilers (power plants) as a result of its physicochemical properties. That is why it is important to build the plant according to the requirements specific for straw combustion boilers. Currently, in the Polish power plants, straw is co-fired with coal in the form of pellets or chaff but most often is burned in medium-scale water boilers, installed in municipal heating plants. In such a plant with a water boiler, there is a small risk of high-temperature corrosion but the problems associated with bed agglomeration and formation of deposits on heat-exchange surfaces exist.12 Leaching is the most common technique to diminish the amount of chlorine and alkali metals in straw. This process may be carried out in two ways: on field, immediately after the harvest of cereals, by leaving straw to be exposed to the rain. It could also be performed with the use of specially designed installations.13 As clearly described in the literature, up to 80% of potassium and chlorine that form the straw can be leached by rain.14 Fuel obtained in this way is called gray straw, having lower contents of mineral matter and better energy parameters.15,13 Using additives is a way to mitigate the risks of creating corrosive deposits in the straw combustion units. There are usually compounds with high melting points, which may also react with constituents of the ash. Additives not only increase the sintering temperature of the ash, but they also reduce the amount of potassium chloride by reaction with mineral matter.11,16 The use of such substances leads to certain modifications of the combustion unit and exploitation procedures. The selection of additives should account for their availability and price. At present, straw-fired units include plants designed for municipal heating plants, air heaters for drying, and cogeneration using organic Rankine cycles (ORCs), with thermal oil as the heating medium.17 Conventional steam boilers fired by straw are quite rare, because of the high temperature in the steam superheater section. This leads to an increased risk of a high temperature and chlorine corrosion and imposes usage of expensive construction materials.18,19 These are mainly noble, alloy austenitic steels, with a high amount of metals, such as Cr, Mo, Ni, or Zn.
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Figure 1. Scheme of installation used for leaching: (1) upper part, (2) bottom part, (3) straw sample, (4) grid supporting the sample straw, (5) drainage, (6) tank, (7) spillway, and (8) dosing pump. module (number 1 in Figure 1). In the lower part (number 2 in Figure 1), a given amount of straw (about 1 kg) was placed. The installation was fed with deionized water, to avoid the deposition of mineral substances contained in drinking water, on the surface of straw. Leaching tests were applied to wheat straw. The sample was placed in the apparatus and washed with deionized water for 3 days with breaks appropriate for drying of straw. By the drying period, the lower modulus was taken out of laboratory to fresh air. This was meant to simulate the periodicity of rainfall and a series of straw soaking and drying periods, similar to what it is subjected during aging in the field. Leaching was performed for the two samples of straw. After leaching, straw samples were analyzed, to determine the content of chlorine and alkali metals, such as Na, K, Mg, and Ca. From this, a degree of reduction of selected elements was calculated. The next part of the research included the laboratory-scale studies, on the properties of the ash after mixing of straw with additives. This included the use of five admixtures: kaolin, dolomite, halloysite, spent bleaching earth (SBE), and limestone. The selection was driven by the physicochemical properties of the selected substances, especially the contents of SiO2, Al2O3, CaO, and MgO, which may significantly increase the ash fusion temperatures. Wheat straw samples with and without additives, in the form of chaff, with a stalk length from 20 to 50 mm, were placed in a ceramic stove at 850 ± 50 °C, in the presence of air for about 300 s. For each sample, ash fusion temperatures were determined, according to norm PN-G-04535:1982. Consecutive parts of the study were testing a WCO-160S strawfired boiler with a capacity of 3.5 MWth (Figure 2). The unit was a
EXPERIMENTAL SECTION
The important factors, which influence the operation of the combustion plant, are physicochemical properties of fuel. At the beginning, proximate and ultimate analyses were carried out, to provide information about key parameters. Samples were collected during the first 3 years (2009−2011) of the project and then analyzed by a certified laboratory. Samples were taken from the same fields, near the town of Lubań, in the Lower Silesia region. Next, the experiments on a leaching process were performed, to simulate the influence of rainfall on straw ash composition. Studies were made on a laboratory testing stand (Figure 1) capable of producing water droplets with diameters close to that of raindrops. Rainfall intensity was regulated by the number of holes in the perforated bottom and the height of the water column in the upper
Figure 2. Scheme of installation in heating plant Lubań: (1) chaff cutter, (2) conveyer, (3) sluice, (4) screw conveyer, (5) WCO-160S boiler grate, and (6) heat exchanger. grate boiler installed in a municipal heating plant in Lubań. The exhaust gases were discharged from the boiler to the chimney through the dedusting system. The boiler has its own installation for straw shredding and automated system for feeding the fuel to the boiler. For research purposes, the installation was fitted with additional stub pipes for the online analysis of flue gases (with the use of a Land Lancom III gas analyzer) and the determination of the particulate matter content in the flue gases (gravimetric method). Test were carried out in B
DOI: 10.1021/acs.energyfuels.5b02693 Energy Fuels XXXX, XXX, XXX−XXX
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Energy & Fuels accordance with PN-EN 12952-15 “Water-Tube Boilers and Auxiliary Equipment. Acceptance Tests”. Paired thermocouples (pt-500 type) were installed to monitor the temperature of the water at the inlet and outlet of the boiler. The temperature of flue gases at the outlet was also measured by k-type thermocouples. The water mass flux was calculated according to measurements using a mercury−water manometer, assembled with a measurement orifice mounted at the water outlet. All of the parameters relevant for the boiler energy balance and emission factor estimation were automatically logged by the computer system. Fuel samples were collected to the hermetic jars, every 20 min of the test, to ensure a representative quality of the sampled fuel. Pilot tests were conducted for two types of straw: wheat and rape, with and without use of kaolin as an additive in an amount of 3%. This particular additive was selected on the basis of the previous part ot the work. Each test lasted for 4 h, at a boiler load set on 75% of nominal thermal output. The last part of the research was to investigate the effect of straw combustion on the structure of construction materials, used by boiler production. The main test was conducted with the use of six types of steels listed in Table 1. The materials selected for the study, in the
A radioisotope thermoelectric generator (RTG) technique and scanning microscopy were used.
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RESULTS Analysis of the straw samples collected in the years 2009−2011 (Table 2) shows a moderate variation of its physical and chemical properties. The carbon content in all types of straw is more or less at the same level. The same was observed for the hydrogen content and lower heating value (LHV). Rape straw is characterized by a higher content of chlorine, sulfur, and alkali metals when compared to wheat and rye straw. In contrast, wheat straw contains more alkali metals than rye straw. The determined, average chlorine content in samples of straw, obtained in years of project realization, did not exceed the value of 0.1%. The measured contents can, therefore, be found significantly lower than the values reported in the literature, ranging from 0.1 to 1.2%. The results presented in Figure 3 clearly show that washing of straw gives significant reduction of the chlorine, sodium, and
Table 1. List of Selected Boiler Steel Grades with Prices sample number 1 2 3 4 5 6
steel type non-alloy quality steel alloy special steel austenitic stainless steel austenitic heat-resisting steel
steel code
steel grade
1.0425
P265GH
1.5415 1.7335 1.4541 1.4539 1.4828
16Mo3 13CrMo4-5 X6CrNiTi18-10 X1NiCrMoCu25-20-5 X15CrNiSi20-12
prize (EUR/Mg) 856 915 971 3041 6465 3436
Figure 3. Changes in the content of chlorine and alkali metals in wheat straw before (as a reference) and after leaching. form of 50 × 50 mm plates, were installed in the oxidizing zone of the WCO-160S boiler, at the two levels: the upper part at the inlet of heat exchangers (section 1) and the lower part of the boiler (section 2), about 1 m below section 1. Next, samples were exposed for about 270 h to conditions observed by typical boiler operation. The average thermal load of the boiler was 1.8 MWth, reaching 50% of its nominal power, giving a total production of 479 MWh of thermal energy. After that time, samples were secured and analyzed by a certified laboratory.
potassium contents. In the case of calcium and magnesium, only slight diminution was observed. The calculated reduction ratio of chlorine, potassium, and magnesium is comparable to the degree of reduction reported in the literature,14 which is presented in Table 3. For sodium and calcium according to the literature,14 reduction should be greater but the essential trend
Table 2. Proximate and Ultimate Analyses of Straw from Years 2009−2011 wheat H (%) C (%) N (%) S (%) moisture content (%) chlorine (%, on db) LHV (kJ/kg) P2O5 (%) P (%) K2O (%) K (%) MgO (%) Mg (%) CaO (%) Ca (%) Na2O (%) Na (%)
rye
rape
maximum
minimum
average
maximum
minimum
average
maximum
minimum
average
6.30 46.97 0.88 0.21 8.02 0.155 16437 0.30 0.13 0.48 0.40 0.13 0.08 0.66 0.47 0.006 0.004
5.5 43.9 0.42 0.14 6.24 0.014 14902 0.12 0.05 0.36 0.30 0.05 0.03 0.44 0.31 0.002 0.002
5.93 45.07 0.62 0.18 6.93 0.065 15724 0.18 0.08 0.41 0.34 0.08 0.05 0.52 0.37 0.004 0.003
6.19 46.57 1.2 0.18 12.5 0.098 16006 0.28 0.12 1.48 1.23 0.11 0.07 0.72 0.51 0.014 0.010
5.6 43.9 0.37 0.12 5.7 0.034 14814 0.08 0.03 0.28 0.23 0.06 0.04 0.34 0.24 0.004 0.003
5.91 45.22 0.68 0.14 8.20 0.059 15256 0.19 0.08 0.65 0.53 0.08 0.05 0.52 0.37 0.009 0.006
6.11 45.65 0.97 0.32 8.55 0.124 16168 0.36 0.16 1.10 0.91 0.22 0.13 1.39 0.99 0.019 0.014
5.7 43.8 0.74 0.18 6.78 0.046 14284 0.20 0.09 0.36 0.30 0.10 0.06 1.00 0.71 0.002 0.002
5.92 44.82 0.86 0.25 7.38 0.076 15182 0.30 0.13 0.79 0.65 0.14 0.08 1.24 0.88 0.009 0.006
C
DOI: 10.1021/acs.energyfuels.5b02693 Energy Fuels XXXX, XXX, XXX−XXX
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Energy & Fuels Table 3. Leaching Effectiveness of Main Mineral Substances from Straw Compared to the Literature14 reduction degree (% by mass) element
own research
literature
Cl Na K Ca Mg
86.1 66.7 78.3 17.5 54.6
89.6 84.6 84.3 36.7 53.1
in the reduction of corrosive components as a result of leaching was proven. Figure 4 presents the ash fusion temperatures observed by the addition of selected substances. In all of the cases, the increase in temperatures of softening and sintering was observed. The highest increase was obtained for a kaolinbased additive. What should be noticed is that a higher amount of additive (6% by mass) gives the highest increase of ash fusion temperatures, but the share of additive in fuel is equal to the ash content. At this stage of research, kaolin in the amount 3% by mass was taken for further investigation. Pilot studies confirmed the positive impact of kaolin addition on ash fusion temperatures, which is presented in Figure 5. A detailed energy balance is given in Table 4. Slight differences, mainly by the boiler efficiency, could result from a variable moisture content, which was difficult to monitor in such a complex facility. The use of kaolin lead to increased emissions of particulate matter [total suspended particles (TSP)] (Figure 6). This is connected with the re-entrainment of the particulates from the fuel bed as a result of a powdered form of additive. The last part of the study was instrumental analysis of corrosion caused by deposits formed during straw combustion. The analysis of temperatures, by operation of the boiler, showed that, in section 1, the temperature varied between 380 and 724 °C (average of 505 °C), while, in section 2, the temperature varied between 337 and 671 °C (average of 480 °C). Figure 7 presents the pictures of steel plates, before (zero plate) and after exposure. Figure 8 presents deposits formed on the steel plates, even though the exposure times were relatively short. High surface changes, caused by corrosion, could be observed for the two first types of steel (1.0425 and 1.5415) (Figure 7). Naked eye analysis is presented in Table 5. Microscope analysis of the surface (steel 1.4828), presented in
Figure 5. Characteristic temperature of ash obtained in the exploitational test in Lubań for straw with and without kaolin. ts, temperature sintering; tA, softening point; tB, melting point; and tC, flow point.
Table 4. Energy Balance of the WCO-160S Boiler in Testing Various Straw and without the Addition of Kaolin straw without additive parametera η QG QCO QSL QFA QRC
% % % % % %
straw mixed with kaolin (3%)
rape
wheat
rape
wheat
85.7 10.54 2.94 0.16 0.01 1.78
78.7 15.75 1.97 0.16 1.56 2.03
84.6 10.54 1.84 0.16 0.01 1.78
81.28 14.84 0.97 0.34 0.54 2.03
η, thermal efficiency; QG, heat loss as a result of sensible heat in flue gases, QCO, heat loss as a result of unburned gases in the flue gases; QSL, heat loss as a result of combustible matter in ash and riddling; QFA, heat loss as a result of combustible matter in grit and dust; and QRC, heat loss as a result of radiation, convection, and conduction. a
Figure 9, shows a structure of deposits formed. The detailed results of instrumental analysis of deposit composition are shown in Table 6.
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DISCUSSION The presented study confirmed that cereal straw has potential to be an important renewable source of energy in Poland. The obtained data also show that there are several problems, which must be solved. Straw from different crops has slightly different
Figure 4. Characteristic temperature of ash obtained in a laboratory scale for wheat straw with and without additives. ts, temperature sintering; tA, softening point; tB, melting point; and tC, flow point. D
DOI: 10.1021/acs.energyfuels.5b02693 Energy Fuels XXXX, XXX, XXX−XXX
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Energy & Fuels
Figure 9. Results of microanalysis for steel 1.4828: (left) reference plate and (right) sample from section 1. Figure 6. Emissions of CO, NOx, SO2, and TSP for the test in Lubań. GWE = governmental emission limits.
Furthermore, pretreatment of fuel before combustion seems to be an important option. One of the methods of processing is leaching, which can lead to diminution of the ash content, and but what is more important is that chlorine and alkali compounds are partially washed out. This method could also lead to an increase of ash fusion temperatures (softening, melting, and flow). From this, the risk of slagging phenomena and the formation of deposits are reduced.20,21 It can be achieved by straw aging in the field; however, this non-technical method is hardly controlled and is strongly dependent upon weather conditions. Assembly of the additional system with the combustion plant leads to increased capital costs. Furthermore, a stream of wastewater produced would have to be managed. That is why a thorough economic analysis of the case is required to determine applicability of this technique. In view of preventing deposit formation, the use of additives seems to be profitable. This paper provided analysis of the influence of several admixtures on ash fusion temperatures. The results show that most of the materials used improved fusion temperatures, yet the most promising results were obtained for kaolin and halloysite. This can be related to the effect of similar properties and composition of the substances. The use of additives also has negative effects. They increase the operating costs of the straw combustion units; the higher the share of additives, the higher the cost of energy production. A inflammable inorganic material is also an additional burden for the boiler. When to use of the additive is decided, its amount should be optimized to achieve the best possible effect: the increased fusion temperatures of ash by limited costs. The addition of kaolin during combustion resulted in an increased emission of particulate matter from the boiler as a result of the powder form of this substance. Despite an increased concentration of particulate matter by kaolin addition, standard dedusting equipment was efficient enough to ensure particulate emissions below allowable emission limit values. What is also important is that a significant drop in the carbon monoxide concentration in the flue gases was observed by the tests when kaolin was added. This could be caused by the chemical structure of this additive, yet the issue has to be analyzed further. When the corrosion risk in straw-fired boilers is considered, the use of special, noble steels as construction materials seems to be a reasonable way to improve the life span of crucial parts in heat exchangers. Pilot studies of selected steel samples during the operation of the boiler proceed that X1NiCrMoCu25-20-5 and X15CrNiSi20-12 are the least vulnerable to corrosion. It should be noted that the use of special steel with increased resistance to high-temperature corrosion is profitable to some
Figure 7. Set of steels used in corrosion studies, with pictures before and after exposition in two sections of the boiler.
Figure 8. Steel samples after test, on the left from section 1 and on the right from section 2.
Table 5. Results of Naked Eye Analysis of Steel Samplesa
a
Colors: red, most corroded; orange, medium corroded; and gray, without visible signs of corrosion.
properties according to proximate and ultimate analyses, but the most important quantities, such as the carbon content or LHV, are at the comparable level for investigated types of straw. E
DOI: 10.1021/acs.energyfuels.5b02693 Energy Fuels XXXX, XXX, XXX−XXX
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Energy & Fuels Table 6. Results of Instrumental Analysis of Steel Samples Exposed in the Boiler amount of element sample number 1.2 1.3 2.2 2.3 3.2 3.3 4.2 4.3 5.2 5.3 6.2 6.3
SiO2
Fe2O3
CaO
MgO
K2O
P2O5
low vestigial vestigial
vestigial vestigial vestigial
vestigial vestigial vestigial
average
vestigial vestigial vestigial vestigial
dominant average dominant vestigial dominant low dominant dominant dominant dominant dominant
dominant vestigial dominant vestigial dominant vestigial vestigial vestigial vestigial vestigial vestigial
dominant
vestigial vestigial
vestigial
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The paper is based on the work carried out within the project “Elaboration of Agricultural Biomass Preparation Process for Energy Utilization”, Contract POIG.01.03.01-00-096/08 (2009−2011).
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vestigial low vestigial vestigial vestigial
Mn3O4
vestigial significant low significant vestigial significant low significant significant significant significant significant
vestigial low vestigial low average low vestigial
vestigial
Na2O
vestigial vestigial vestigial vestigial
vestigial vestigial vestigial
(10) Liao, Y.; Yang, G.; Ma, X. Experimental study on the combustion characteristics and alkali transformation behavior of straw. Energy Fuels 2012, 26 (2), 910−916. (11) Zeuthen, J. H.; Jensen, P. A.; Jensen, J. P.; Livbjerg, H. Aerosol formation during the combustion of straw with addition of sorbents. Energy Fuels 2007, 21 (2), 699−709. (12) Lund, H.; Möller, B.; Mathiesen, B. V.; Dyrelund, A. The role of district heating in future renewable energy systems. Energy 2010, 35 (3), 1381−1390. (13) Bakker, R. R.; Jenkins, B. M.; Williams, R. B. Fluidized bed combustion of leached rice straw. Energy Fuels 2002, 16 (2), 356−365. (14) Jenkins, B. M.; Bakker, R. R.; Wei, J. B. On the properties of washed straw. Biomass Bioenergy 1996, 10 (4), 177−200. (15) Bakker, R. R.; Jenkins, B. M. Feasibility of collecting naturally leached rice straw for thermal conversion. Biomass Bioenergy 2003, 25 (6), 597−614. (16) Xu, X. G.; Li, S. Q.; Li, G. D.; Yao, Q. Effect of Co-firing Straw with Two Coals on the Ash Deposition Behavior in a Down-Fired Pulverized Coal Combustor. Energy Fuels 2010, 24 (1), 241−249. (17) Ericsson, K. Co-firing - A strategy for bioenergy in Poland? Energy 2007, 32 (10), 1838−1847. (18) Yin, C.; Rosendahl, L.; Clausen, S.; Hvid, S. L. Characterizing and modeling of an 88 MW grate-fired boiler burning wheat straw: Experience and lessons. Energy 2012, 41 (1), 473−482. (19) Okoro, S. C.; Montgomery, M.; Frandsen, F. J.; Pantleon, K. High temperature corrosion under laboratory conditions simulating biomass-firing: A comprehensive characterization of corrosion products. Energy Fuels 2014, 28 (10), 6447−6458. (20) Khalil, R. A.; Houshfar, E.; Musinguzi, W.; Becidan, M.; Skreiberg, Ø.; Goile, F.; Løvås, T.; Sørum, L. Experimental investigation on corrosion abatement in straw combustion by fuel mixing. Energy Fuels 2011, 25 (6), 2687−2695. (21) Hansen, S. B.; Jensen, P. A.; Frandsen, F. J.; Wu, H.; Bashir, M. S.; Wadenbäck, J.; Sander, B.; Glarborg, P. Deposit Probe Measurements in Large Biomass-Fired Grate Boilers and Pulverized-Fuel Boilers. Energy Fuels 2014, 28 (6), 3539−3555.
limits as a result of economic reasons. Stock prices of steels used during the tests vary substantially and depend upon the applied alloying elements, as shown in Table 1. The discussed results show several means to minimize risks connected with the use of straw for energy production. In all cases, technical and economic analyses are of key importance.
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vestigial
SO3
REFERENCES
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DOI: 10.1021/acs.energyfuels.5b02693 Energy Fuels XXXX, XXX, XXX−XXX
