Analysis of the effect of catalytic additives in the agricultural waste combustion process

Ci a ion: Najse , T.; Gaze, B.; Knu el, B.; Ve ne , A.; Najse , J.; Mikeska, M.; Chojnacki, J.; Nˇemˇcek, O. Analysis o he E ec o Ca aly ic Addi i es in he Ag icul u al Was e Combus ion P ocess. Ma e ials 2022,15, 3526. h ps://doi.o g/10.3390/ ma15103526 Academic Edi o s: And ea Pe ella and An onio Gil B a o Recei ed: 15 Ma ch 2022 Accep ed: 12 May 2022 Published: 13 May 2022 Publishe ’s No e: MDPI s ays neu al wi h ega d o ju isdic ional claims in published maps and ins i u ional a il- ia ions. Copy igh : © 2022 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). ma e ials A icle Analysis o he E ec o Ca aly ic Addi i es in he Ag icul u al Was e Combus ion P ocess Tomáš Najse 1,* , Bła˙ zej Gaze 2, Be na d Knu el 2, Adam Ve ne 1,3, Jan Najse 1, Ma cel Mikeska 1, Je zy Chojnacki 4and Ondˇ ej Nˇemˇcek 1 1 ENET Cen e, VSB—Technical Uni e si y o Os a a, 17 Lis opadu 2172/15, 708 00 Os a a, Czech Republic; [email p o ec ed] (A.V.); [email p o ec ed] (J.N.); [email p o ec ed] (M.M.); [email p o ec ed] (O.N.) 2Ins i u e o Ag icul u al Enginee ing, W oclaw Uni e si y o En i onmen al and Li e Sciences, 51-630 W oclaw, Poland; blazej.gaze@upw .edu.pl (B.G.); be na d.knu el@upw .edu.pl (B.K.) 3Nano echnology Cen e, VSB—Technical Uni e si y o Os a a, 17 Lis opadu 2172/15, 708 00 Os a a, Czech Republic 4Facul y o Mechanical Enginee ing, Koszalin Uni e si y o Technology, Racławicka S . 15-17, 75-620 Koszalin, Poland; je zy[email p o ec ed] *Co espondence: [email p o ec ed]; Tel.: +420-596-995-724 Abs ac : This pape p esen s he esea ch esul s o he e ec o using calcium oxide and po assium pe mangana e on he combus ion o pelle s om whea b an and bee pulp. The measu emen s we e pe o med in he echnical labo a o y o he Cen e o Ene gy U iliza ion o Non-T adi ional Ene gy Sou ces in Os a a. The esea ch examined he e ec o he use o chemical subs ances on he amoun o ai pollu an s om biomass he mal con e sion in a low-powe boile and he p ocess empe a u e. Fi s , we pe o med echnical and elemen a y analyses o ag icul u al was e. The aw ma e ial was hen comminu ed, mixed wi h a selec ed addi i e, pelle ized, and inally bu ned in a low-powe boile . The addi i e was added in h ee p opo ions: 1:20, 1:10, and 1:6.67 (i.e., 15%) ela i e o he uel weigh . The combus ion p ocess e iciency was measu ed using a lue gas analyze and h ee he mocouples a ached o he da a eco de . F om he measu emen esul s, we we e able o de e mine he pe cen age educ ion o pollu an emissions in o he a mosphe e (CO, NO x , and SO 2 ) due o he use o addi i es. Because emission s anda ds a e becoming inc easingly s ingen and uel and ene gy p ices a e ising, he esul s p esen ed in his a icle may be use ul o ag i- ood p ocessing plan s ha wan o manage hese ma e ials he mally. Keywo ds: ag icul u al was e; ca aly ic addi i es; combus ion; emission educ ion 1. In oduc ion The use o biomass in he ene gy sec o can po en ially educe he emission o ha m ul subs ances in o he ai . I is assumed ha he abso bed amoun o CO 2 du ing plan g ow h balances he amoun gene a ed in he p ocess o biomass combus ion [ 1 ]. Biomass is he e o e conside ed a ze o-emission uel. This assump ion is inco ec because bu ning biomass also p oduces o he pollu an s ha he plan canno abso b du ing he g owing season. The pollu an s emi ed du ing he combus ion p ocess can be di ided in o p ima y and seconda y g oups. P ima y pollu an s a e emi ed in o he a mosphe e di ec ly a he loca ions whe e hey a e p oduced. P ima y pollu an s emain in he a mosphe e unchanged om he momen hey a e gene a ed. The sou ces o p ima y pollu ion a e powe plan s and hea ing de ices o single- amily houses. Seconda y pollu an s, howe e , a e he p oduc s o physical changes and chemical eac ions be ween he componen s o he a mosphe e and he pollu an s ha low in o i . Con inuous echnological p og ess, new b anches o indus y, and he de elopmen o anspo con ibu e o he inc ease in he numbe o poin , line, and a ea emi e s. The cons an inc ease in he numbe o sou ces Ma e ials 2022,15, 3526. h ps://doi.o g/10.3390/ma15103526 h ps://www.mdpi.com/jou nal/ma e ials Ma e ials 2022,15, 3526 2 o 13 o ha m ul emissions has an ad e se impac on ai quali y. In highly de eloped coun ies, legal di ec i es and laws speci y he emission limi s o indi idual compounds ela ed o he ype o uel bu ned o he nominal powe o he emi e . The e o e, he g owing numbe o emi e s is no e lec ed in he amoun o emissions [2]. Resea ch commissioned by he Eu opean En i onmen Agency (EEA) showed ha ai pollu ion is one o he leading en i onmen al ac o s a ec ing human li e and heal h [ 2 ]. In highly de eloped coun ies, including EU coun ies, app op ia e legal egula ions we e in oduced o limi he p oblem o ha m ul emissions [ 2 – 4 ]. Du ing he combus ion p ocess, ha m ul subs ances emi ed in exhaus gases include suspended dus (PM), ca bon monox- ide (CO), ni ogen oxides (NO x ), and sul u oxides (SO x ). The haza dous compounds emi ed in exhaus gases a e polycyclic a oma ic hyd oca bons (PAHs) and ola ile o ganic compounds (VOCs). The emissions o hese compounds a e inc edibly high in he case o biomass combus ion [ 4 – 8 ]. Too high o a concen a ion in he ai o he compounds men- ioned abo e can po en ially lead o de iciencies in he human ci cula o y and espi a o y sys ems. E en a sligh excess in he pe missible concen a ions o pollu an s in he ai may cause dis u bances in concen a ion and pe cep ion [8–12]. The implemen ed EU Emissions T ading Sys em (EU ETS) is one o he main ools in he igh agains ai pollu ion. This sys em co e s app oxima ely 40% o all g eenhouse gas (GHG) emissions in he Eu opean Economic A ea. The emissions ading sys em, in addi ion o new legal egula ions, enables he con inuous educ ion o pe missible limi alues in educing he o al emission o pollu an s [ 13 ]. Acco ding o he Eu opean Commission, all o hese measu es aim o b ing abou an economic ans o ma ion owa d clima e neu ali y, which mus be a ained by 2050 [14,15]. Ca aly ic subs ances added o combus ed ene gy ca ie s a e a g oup o compounds ha imp o e he e iciency o he combus ion p ocess. One o he asks o ca aly ic addi i es is o inc ease he oxida ion p ocess o uel pa icles oge he wi h p oduc s o incomple e combus ion. Depending on he used ca alys , i is possible o educe o oxidize selec ed ha m ul compounds. The use o co-combus ion o ac i e subs ances wi h uels is able o educe g eenhouse gas emissions and elimina e ca cinogenic, mu agenic, and oxic compounds [ 16 ]. Ca aly ic addi i es based on coppe (Cu) and manganese (Mn) oxide, wi h he use o aluminum oxide (Al 2 O 2 ) as a ca ie , demons a ed he e ec o educing ca bon monoxide (CO) emission and pa icula e ma e du ing he combus ion o solid biomass. The g ea ad an age o his ype o ca alys is i s low p ice [ 16 – 19 ]. Du ing ou esea ch in 2021 a he Uni e si y o Li e Sciences in W ocław, we p epa ed i e di e en ca aly ic compounds based on One me hod o managing and elimina ing ha m ul emissions is p omo ing solu ions based on enewable ene gy in hea and elec ici y gene a ion sys ems. Mainly in la ge and low-powe ins alla ions, his ans o ma ion consis s o eplacing ossil uels, such as coal, wi h high-quali y biomass uel [21]. Du ing he combus ion o biomass, he concen a ion o pollu an s in exhaus gases is many imes lowe han he composi ion o exhaus gases om coal combus ion [ 22 , 23 ]. Ano he ad an age o he use o biomass ene gy is i s local applica ion, he eby educing emissions p oduced h ough anspo a ion. The use o biomass uel p oduced om local aw ma e ials also pe mi s he di e si ica ion o ene gy sou ces, which is now a desi able ope a ion [24,25]. Conside ing he cu en s a e o de elopmen in al e na i e ene gy sou ces, we may sa ely conclude ha in he e a o phasing ou ossil uels, uels om biomass will soon ake o e he ole o basic ene gy ca ie , o example, in hea gene a ion sys ems. Com- pa ed wi h con en ional ene gy sou ces, biomass uels a e a low-emission al e na i e in he p oduc ion o elec ici y and hea . Biomass wi h high ene gy po en ial is ound in almos e e y co ne o he wo ld. Depending on i s physicochemical p ope ies, biomass can be ans o med in he mal p ocesses, o example, gasi ica ion, py olysis, and di ec combus ion, o exploi i s ene gy [26]. Ma e ials 2022,15, 3526 3 o 13 In he a ea whe e we conduc ed ou esea ch, suga p oduc ion is a majo indus y. In he p oduc ion o suga om suga bee , was e is gene a ed in he o m o bee pulp. The companies ha p oduce suga ha e p oblems managing his ype o biomass was e. P e iously, suga pulp was used as eed o a m animals, bu due o dec easing numbe s o pig and ca le b eede s in he nea es egion and he ansi ion o a ms o au oma ed eeding wi h eady-mixed eed, he p oblem o bee pulp managemen has become signi ican . The second local biomass was e ha equi es managemen is whea b an, which is o med du ing he p oduc ion o whea lou . Local companies ha p oduce lou sell a small amoun o his was e as an addi i e o animal eed. Howe e , he p oduc ion o was e in he o m o whea b an is g ea e han he ma ke demand and gene a es a la ge quan i y o biomass was e ha also equi es managemen . This pape consis s o i e sec ions. Sec ion 1includes in o ma ion abou ai pollu ion and i s e ec on heal h, he ypes o ca alys s, and he me hods o was e biomass ene gy managemen . Sec ion 2desc ibes he me hods and equipmen used o measu ing exhaus gas quali y and he empe a u es in he combus ion chambe and lue gas duc . Sec ion 3 discusses he esul s o ou esea ch, which in es iga ed he e ec o addi i es (po assium pe mangana e and calcium oxide) on emissions p oduced by biomass was e combus ion. Sec ion 4summa izes he esea ch ou comes. Sec ion 5p esen s conclusions d awn om he esea ch and p oposes ollow-up s udies in his ield. 2. Ma e ials and Me hods 2.1. Resea ch Expe imen The s udy in es iga ed he use o a low-powe , ully au oma ed e o boile wi h a nominal powe o 31.5 kW (VARIANT SL-33 A, p oduced by Sloko , Mo a skýPísek, Czech Republic). The ope a ing pa ame e s o he de ice we e egula ed using a con olle . The eadings o he empe a u e senso and lambda p obes enabled he con ol uni o adjus he ene gy ca ie and ai supplied o he combus ion chambe o p o ide sui able doses. An exhaus gas an and auge coupled wi h a pelle hoppe egula ed he ai and uel doses. The hea p oduced om he uel he mal con e sion p ocess was ans e ed o he en i onmen h ough wo an hea e s wi h a hea ing capaci y o 30 kW each. The combus ion p ocess was con inuous, and he doses o ai and uel we e injec ed pe iodically o e sho pe iods. These pa ame e s we e he same o each ype o biomass uel used in he combus ion p ocess. A schema ic diag am o he boile is p esen ed in Figu e 1, showing he loca ions o he he mocouples and sampling poin s. Figu e 1. Schema ic diag am o he boile , he mocouples, and sampling poin s. Ma e ials 2022,15, 3526 4 o 13 The speci ica ions o he pelle boile a e shown in Table 1. Table 1. Speci ica ions o he VARIANT SL33A pelle boile . Pa ame e Uni Value Boile class acco ding o Ecodesign Di ec i e - 4 Boile ou pu kW 31.5 Boile e iciency % 87.3 Boile weigh kg 320 Maximum ope a ing empe a u e ◦C 90 Minimum e u n wa e empe a u e ◦C 70 Fuel ank capaci y dm3210 Highes wo king o e p essu e ba 2 2.2. Ma e ials The ene gy ca ie was a pelle wi h a diame e o 6 mm and was composed o ag icul u al was e, i.e., whea b an (Figu e 2a) and bee pulp (Figu e 2b). Figu e 2. Ag icul u al was e used in he combus ion p ocess in he biomass low-powe boile : (a) whea b an and (b) bee pulp. The he mal con e sion p ocess o he pelle s included he use o ca aly ic addi i es in he o m o calcium oxide CaO (Figu e 3a) and po assium pe mangana e KMnO 4 (Figu e 3b) wi h pu i ies o 99.5%. They we e added o he uel du ing pelle iza ion o g ound aw ag icul u al ma e ial in concen a ions o 5, 10, and 15%. Figu e 3. Ca aly ic addi i es: (a) calcium oxide and (b) po assium pe mangana e. 2.3. Bio uel Physicochemical Analysis All es s o analyze he physicochemical p ope ies o he biomass ma e ials we e pe o med h ee imes. Using he TGA me hod and a TGA 701 analyze , we examined he biomass ene gy ca ie s o de e mine hei mois u e con en , ola ile subs ance con en , ash con en , and calo i ic alues. Table 2lis s he echnical speci ica ions o he TGA 701 analyze . Ma e ials 2022,15, 3526 5 o 13 Table 2. Technical speci ica ion o TGA 701 analyze . Pa ame e Uni Value Sample mass g 1 Numbe o samples pcs 19 (+1 e e ence) P ecision % 0.02 Tempe a u e con ol ange ◦C 100–1000 Tempe a u e con ol accu acy ◦C±2 Tempe a u e con ol s abili y ◦C±2 Maximum amp a e om ambien o 104 ◦ C ◦C·min−115 Maximum amp a e om 104 ◦C o 1000 ◦C◦C·min−150 Gas p essu e ba 3.1 o ai , 2.4 o ni ogen, 2.4 o oxygen Minimum gas pu i y % 99.9 o ni ogen, 99.5 o oxygen G oss calo i ic alues we e asce ained using an IKA C 200 calo ime e . A highe hea ing alue was applied in acco dance wi h he PN-EN s anda d [ 27 ]. Table 3lis s he echnical speci ica ion o he IKA C 200 calo ime e . Table 3. Technical speci ica ions o he IKA C 200 calo ime e . Pa ame e Uni Value Maximum ou pu ene gy J 40,000 Tempe a u e senso esolu ion ◦C 0.0001 Oxygen wo king p essu e ba 40 Ini ial empe a u e se ings ◦C 18–25 Using a Pe kinElme CHNS/O 2400 analyze (Wal ham, MA, Uni ed S a es), we de e mined he elemen al composi ion (i.e., ca bon, hyd ogen, ni ogen, and sul u con en ) o he biomass ma e ials. The analysis was pe o med on d y samples agmen ed in o pa icle sizes o less han 0.2 mm, acco ding o he PN-EN s anda d [ 28 ]. Table 4lis s he echnical speci ica ions o he de ice. Table 4. Technical speci ica ions o he Pe kinElme CHNS/0 2400 analyze . Pa ame e Uni Value Tempe a u e ange ◦C 100–1100 Sample size mg 0–500 Accu acy % ≤0.3 Ca bon analy ical ange mg 0.001–3.6 Hyd ogen analy ical ange mg 0.001–1.0 Ni ogen analy ical ange mg 0.001–6.0 Sulphu analy ical ange mg 0.001–2.0 Oxygen analy ical ange mg 0.001–2.0 2.4. Measu emen o he Exhaus Gas Composi ion The exhaus gas composi ion was measu ed using a Wöhle A 550 analyze . Indi idual compounds in he lue gas we e de ec ed using an elec ochemical non-dispe si e in a ed senso (NDIR). We i s calib a ed he analyze , hen measu ed he exhaus gas compounds a e he combus ion p ocess had s abilized. The sampling loca ion was he lue gas pipe jus behind he boile . Values we e eco ded e e y second o e 6 h o con inuous boile ope a ion. Table 5summa izes he echnical speci ica ion o he analyze . Ma e ials 2022,15, 3526 6 o 13 Table 5. Technical speci ica ions o he Wöhle A 550 lue gas analyze . Componen Measu emen P inciple Range Accu acy O2Elec ochemical senso 0–21 ol.% ±0.3% ol.% CO Elec ochemical senso , H2 compensa ed 0–4000 ol. ppm ±20 ppm (< 400 ppm), o he wise ±5% o measu emen CO2NDIR 0–40% ±0.3 ol.% (0–6 ol.%) o he wise ±5% o eading NO Elec ochemical senso 0–3000 ol. ppm (con inuously up o 1000) ±5 ol. ppm (<100 ppm), o he wise 5% o eading NOxElec ochemical senso 0–1000 ol. ppm (con inuously up o 200) ±5 ol. ppm (<100 ppm), o he wise 5% o eading SO2Elec ochemical senso 0–5000 ol. ppm ±10 ol. ppm (0–200 ppm), o he wise 5% o eading The expe imen p o ided a compa ison o he e ec o selec ed chemical ac i e sub- s ances on he combus ion p ocess o whea b an and bee pulp pelle s. The measu ed emission alues we e ecalcula ed o a e e ence oxygen con en o 10 ol.%. 2.5. Measu emen o he Combus ion P ocess Tempe a u e The empe a u e in he combus ion chambe was measu ed acco ding o he PN-EN s anda d. The empe a u e was eco ded using h ee K- ype he mocouples connec ed o he PAR AR205 eco de . The empe a u e was eco ded e e y second o he en i e pe iod o he boile ope a ion. The mean measu emen e o in he esul s was ±1.5 ◦C. 3. Resul s We conduc ed a se ies o es s o de e mine and compa e he e ec s o selec ed ca aly ic addi i es on he combus ion p ocess o whea b an and bee pulp pelle s. The measu ed alues o indi idual pollu an emissions we e con e ed o a e e ence oxygen con en (10 ol.% o con en in he exhaus gas). 3.1. Bio uel Physicochemical Analysis Tables 6and 7p esen he esul s o ou analysis o he ag icul u al o igin aw ma e ials. Table 6. Resul s o he analysis o whea b an. Pa ame e Uni Value Mois u e con en % 12.73 ±1.91 Ash con en % 5.65 ±0.85 Vola ile ma e con en % 65.27 ±11.75 Highe hea ing alue MJ·kg−116.92 ±1.69 Lowe hea ing alue MJ·kg−113.19 ±1.32 Table 7. Resul s o he analysis o bee pulp. Pa ame e Uni Value Mois u e con en % 11.81 ±1.77 Ash con en % 7.14 ±1.07 Vola ile ma e con en % 66.15 ±11.91 Highe hea ing alue MJ·kg−115.04 ±1.50 Lowe hea ing alue MJ·kg−111.79 ±1.18 Tables 8and 9p esen he esul s o ou elemen al analysis o he whea b an and bee pulp. Ma e ials 2022,15, 3526 7 o 13 Table 8. Resul s o he elemen al analysis o whea b an. Pa ame e Uni Value Ni ogen con en % 2.70 ±0.40 Ca bon con en % 40.50 ±6.08 Hyd ogen con en % 6.67 ±1.00 Sul u con en % 0.16 ±0.02 Table 9. Resul s o he elemen al analysis o bee pulp. Pa ame e Uni Value Ni ogen con en % 1.34 ±0.20 Ca bon con en % 37.90 ±5.68 Hyd ogen con en % 6.18 ±0.93 Sul u con en % 0.16 ±0.02 3.2. Analysis o he Exhaus Gas Composi ion We compa ed ou measu emen s wi h he igu es o bu ning A1 class wood pelle s (used as a e e ence, as in [ 29 ]), which a e a popula ype o ene gy ca ie . Using he analyze manu ac u e ’s so wa e, he esul s we e au oma ically con e ed in o an oxygen con en o 10 ol.% in he exhaus gases. Table 10 p o ides a key o he e ms used in he cha s ha indica e hese esul s. Table 10. Te ms used in he cha s. Abb e ia ion Desc ip ion RM Re e ence measu emen CaO (5%) 5% CaO con en in ela ion o he mass o uel bu ned CaO (10%) 10% CaO con en in ela ion o he mass o uel bu ned CaO (15%) 15% CaO con en in ela ion o he mass o uel bu ned KMnO4(5%) 5% KMnO4con en in ela ion o he mass o uel bu ned KMnO4(10%) 10% KMnO4con en in ela ion o he mass o uel bu ned KMnO4(15%) 15% KMnO4con en in ela ion o he mass o uel bu ned Figu e 4shows he ela ionship be ween he CO concen a ion in he exhaus gases and he ype o bio uel and ca aly ic addi i e used in he expe imen . Figu e 4. Concen a ions o ca bon monoxide in he lue gas o a low-powe boile while bu ning biomass wi h ca aly ic addi i es. Ma e ials 2022,15, 3526 8 o 13 Du ing he biomass was e combus ion p ocess, he CO emissions eached le els o 451 mg·m−3 o whea b an pelle s and 746 mg · m −3 o bee pulp pelle s. Ca bon monoxide emissions du ing he combus ion o comme cial uel (wood pelle s) eached a le el o 252 mg · m −3 . The use o addi i es in combina ion wi h uel du ing combus ion educed he CO concen a ion in he exhaus gases in each case. Du ing he combus ion o whea b an pelle s, ca bon monoxide emissions dec eased, on a e age, by 15–41% using a CaO-based addi i e and 20–45% using a KMnO 4 -based addi i e. When bu ning he bee pulp pelle s, he CO emissions we e educed by 12–21% using a CaO-based addi i e, depending on he addi i e concen a ion, and 19–30% using a KMnO 4 -based addi i e, also depending on he concen a ion o he ac i e subs ance. While eeding he boile wi h wood pelle s, he CO emissions in o he a mosphe e we e educed by 8–18% using CaO, depending on he concen a ion o he subs ance, and 3.5–30% using KMnO 4 . These da a we e he a e age alues o wo measu emen se s. Figu e 5indica es he ela ionship be ween he exhaus gas NO x concen a ion, he ype o bio uel, and he ca alys . Figu e 5. Concen a ions o ni ogen oxides in he lue gas o a low-powe boile du ing he p ocess o bu ning biomass wi h ca aly ic addi i es. We eco ded he concen a ions o ni ogen oxides emi ed du ing he combus ion o he biomass pelle s. NO x emissions a ied a ound 559 mg · m −3 du ing he combus ion o whea b an pelle s, 341 mg · m −3 in he case o bee pulp pelle s, and 185 mg · m −3 o wood pelle s. The addi ion o he CaO-based addi i e educed he NO x emissions by 7–16% (whea b an pelle s), 8–27% (bee pulp pelle s), and 8–18% (wood pelle s), depending on he concen a ion o he subs ance. Bu ning he biomass wi h he KMnO 4 -based addi i es also succeeded in educing he concen a ions o ni ogen oxides in he lue gas. Using his addi i e, NO x emissions we e educed by 24–36% (whea b an), 12–35% (bee pulp), and 3.5–30% (wood pelle s), depending on he concen a ion o he ac i e subs ance. These da a we e he a e age alues o wo measu emen se s. Figu e 6indica es he e ec o he bio uel and ca aly ic addi i es on he concen a ions o sul u dioxide (SO2) in he exhaus gases. We also eco ded educed concen a ions o SO 2 du ing he p ocess o bu ning whea b an and bee pulp wi h addi i es. No educ ion in he composi ion o exhaus gases was obse ed while bu ning wood pelle s in he boile . The SO 2 emissions we e 13.4 mg · m −3 du ing he combus ion o whea b an pelle s and 9.8 mg · m −3 in he case o bee pulp pelle s. Each o he addi i es in combina ion wi h he biomass uel p oduced a educ ion in SO 2 concen a ion in he exhaus gases. While bu ning whea b an, he SO 2 emissions dec eased by 74–83% using he CaO-based addi i e and 15–42% using he KMnO 4 -based addi i e, depending on he concen a ion o he ac i e subs ance. In he case o bu ning bee pulp pelle s, he SO 2 emissions we e educed by 71–87% using he CaO-based addi i e Ma e ials 2022,15, 3526 9 o 13 and 41–65% using KMnO 4 , depending on he concen a ion o he addi i e. These da a we e he a e age alues o wo measu emen se s. Figu e 6. Concen a ions o sul u oxides in he lue gas o a low-powe boile du ing he p ocess o bu ning biomass wi h ca aly ic addi i es. 3.3. Measu emen o he Combus ion P ocess Tempe a u e Figu e 7p esen s he a e age empe a u e egis e ed in he combus ion chambe o he boile a e he s abiliza ion o he combus ion p ocess. Figu e 7. The dis ibu ion o he a e age empe a u es in he combus ion chambe du ing he combus ion o biomass wi h ca aly ic addi i es. We eco ded inc eases in he a e age empe a u es in he combus ion chambe o he low-powe boile du ing he combus ion o biomass uels in combina ion wi h CaO and KMnO 4 addi i es (in all concen a ions). The a e age inc ease in he eco ded empe a u es in he boile ’s combus ion chambe in he case o whea b an pelle s was 5 ◦ C–24 ◦ C depending on he CaO concen a ion and 7 ◦ C–28 ◦ C depending on KMnO 4 concen a ion. In he case o bee pulp pelle s, he empe a u e inc eased in he combus ion chambe on a e age by 2 ◦ C–12 ◦ C wi h he addi ion o CaO, depending on i s concen a ion, and 9 ◦ C–19 ◦ C wi h he addi ion o KMnO 4 , also depending on concen a ion. While eeding he boile wi h he mos popula biomass uel, i.e., wood pelle s, he empe a u e inc eased by 1 ◦ C–11 ◦ C using he CaO addi i e, a ying wi h concen a ion, and 2 ◦ C–13 ◦ C while using he KMnO4addi i e. These da a we e he a e age alues o wo measu emen se s.