| Abstract | Za proizvodnju biogoriva druge generacije koristi se lignocelulozna biomasa, uključujući ostatke nakon žetve iz biljne proizvodnje i biomase voćnjaka (orezana biomasa i jame). Najvažnija svojstva lignocelulozne biomase su vrlo dobra čvrstoća, zapaljivost, biorazgradivost i reaktivnost. Prednost biomase je što se mehaničkim, fizikalnim, toplinskim ili biološkim postupcima pretvara u čvrsta, tekuća ili plinovita biogoriva. Izbor postupka ovisi o vrsti, svojstvu i količini dostupne biomase, željenom krajnjem obliku energije i ekološkim standardima.
Posljednjih godina teži se uvođenju naprednih krutih i tekućih biogoriva iz poljoprivredne biomase, a jedan od najznačajnijih procesa korištenih u tu svrhu je piroliza. Piroliza je termokemijski postupak kojim se dobivaju bioulje i biougljen, čiji je glavni cilj zamjena dijela fosilnih goriva. Bioulje ima ekološke prednosti kao čisto tekuće gorivo, dok biougljen ima visoku energetsku vrijednost kao kruto gorivo. Na kvalitetu navedenih proizvoda utječu mnogi čimbenici kao što su vrsta biomase, priprema sirovine (veličina i oblik čestice, sadržaj vlage i pepela) te uvjeti postupka pirolize.
Cilj ovog istraživanja bio je odrediti utjecaj sastava i mehaničke pripreme ratarske i voćarske biomase na kvalitetu bioulja i biougljena dobivenog pirolizom.
Istraživanje je bilo podijeljeno u tri glavne faze, uključujući prikupljanje, mehaničku pripremu i analizu biomase, proces pirolize sa česticama veličine 300 i 600 μm te analizu krajnjih proizvoda bioulja i biougljena.
Istraživanje je pokazalo da se ratarska i voćarska biomasa, s obzirom na analizirana energetska svojstva, mogu koristiti kao kvalitetni energenti u proizvodnji krutih, kao i u proizvodnji tekućih goriva. Veličina i ujednačenost čestica utjecale su na količinu proizvedenog biougljena pa su čestice veličine 600 μm povećavale količinu proizvedenog biougljena. Sastav bioulja dobivenog iz poljoprivrednih ostataka ratarske biomase, orezane biomase i biomase koštica je sličan te je lošije kvalitete od naftnih goriva i zahtijeva različite prilagodbe prije primjene. Temeljem usporedbe energetskih svojstava ulazne biomase te kvalitete dobivenog ulja ne vidi se izravna poveznica, što je možda povezano i sa samim procesom pirolize i uvjetima u reaktoru, te su zbog navedenog vidljive sličnosti u fizikalno-kemijskoj analizi bioulja svih grupa istraživane biomase. Istraživanje je pokazalo da se ratarska i voćarska biomasa te konačni produkti njihove pirolize, biougljen i bioulje, mogu koristiti kao sirovine za proizvodnju energije (neposredno ili kao sirovina u suspaljivanju), dok se dio proizvedenog biougljena, s obzirom na to da zadovoljava standarde, može koristiti i kao poboljšivač tla. |
| Abstract (english) | For the production of second-generation biofuels, lignocellulosic biomass is used, including postharvest residues from crop production and orchards biomass (pruned biomass and pits). The most important properties of lignocellulosic biomass are very good strength, flammability, biodegradability and reactivity. The average values of the lignocellulosic composition of biomass are: 40 - 60% cellulose, 20 - 40% hemicellulose and 10 - 25% lignin. Lignin provides strength to the structure, and biomass with a higher lignin content is more suitable for the production of electrical and/or thermal energy by the combustion process. Biomass with a higher content of cellulose has a higher oxygen concentration than lignin, so the heating value of cellulose is lower than lignin and is more suitable for the production of liquid biofuels.
Biomass has the advantage of being converted into solid, liquid or gaseous biofuels by mechanical, physical, thermal or biological processes. The choice of process depends on the type, property and amount of available biomass, the desired end-form of energy and environmental standards. Common methods used to convert biomass for energy purposes are biochemical and thermochemical methods. Pyrolysis is a thermochemical process which, unlike direct combustion, can produce a whole range of products with greater added value, it is carried out in the absence of oxygen and its by-product are biofuel and biochar. Typical pyrolysis operating temperature ranges from 500 - 800 °C. The relative amount of each product depends on the characteristics of the biomass and the preparation of the biomass for the pyrolysis process. The quality of the milling and the uniformity of the particles significantly affect the yield. The size and uniformity of the particles affect the degree of heating in the reactor, thus larger particles (> 630 μm) reduce the degree of warming and increase the amount of produced biochar. Smaller particles (<630 μm) favor the decomposition of hydrocarbons with increased hydrogen content, since the residence time of the volatile matter in the reactor is longer. Based on the above, the biochar yield ranges from 10 to 35% and the biofuels from 15 to 35%. Bio-oil has environmental benefits as clean liquid fuel, while biochar has high energy value as a solid fuel.
The aim of this research was to determine the influence of orchards and postharvest biomass composition and mechanical preparation on quality of bio-oil and biochar obtained by pyrolysis.
The investigation was conducted over two years on residues of crop and orchards production. From crop residues, the following was investigated: wheat, rye, barley, oats and triticale straw, while the orchards biomass included apricot, nectarine, peach, cherry and soure cherry pruned biomass as well as the pits of mantioned fruit. In each year the biomass is ground and 300 and 600 μm particles are separated by sieving. Separated particles are subjected to: biomass structural analysis (determination of cellulose, lignin and hemicellulose content), physical chemical analyzes (determination of moisture content, ash, fixed carbon, coke, volatile matter and macro elements), elemental analysis (determination of carbon, nitrogen, hydrogen, sulfur and oxygen content), the analysis of the heat value (higher and lower heating value). Furthermore, the separated particle sizes were subjected to a thermochemical conversion process - pyrolysis after which the obtained fractions of biochar and biofuels were subjected to further analyzes. The analysis of biofuels consisted of determining the content of the obtained
biofuels, the moisture content, the pH value, the electrical conductivity, the heating value and the chemical composition of the biofuels. For biochar, the proportion of obtained biochar, the content of fixed carbon, coke, ash and the amount of micro and macro elements as well as the heating value were determined.
The research has shown that, due to the analyzed energy properties, crop and orchards biomass can be used as quality energy products in the production of solid as well as in the production of liquid biofuels. The size and uniformity of the particles affected the amount of produced biochar, so particles with a size of 600 μm increased the amount of produced biochar. The composition of biofuels obtained from agricultural residues from crop biomass, pruned biomass and pits biomass is similar, and is of inferior quality to petroleum fuels and requires different adjustments before application. Based on a comparison of the raw biomass energy properties and the quality of the resulting bio-oil, no direct link can be seen, which may be related to the pyrolysis process itself and the conditions in the reactor, and due to the aforementioned similarities in the physical and chemical analysis of bio-oil of all investigated biomass groups are noticeable. Due to its physicochemical properties, biochar has proven to be a better energy source per unit mass than raw material, and certain resulting biochar can be used as soil improvers by default. Deviations of biochar from the EBC standard when analyzing heavy metals occurred only with increased cadmium content in a large number of cultures. Given these values and the values obtained in this research as a soil improver can be used biochar from barley straw, peaches apricots, nectarines branches and nectarines pits. The study also found that cadmium content decreased during pyrolysis of smaller particles (300 μm).
Based on the above, it can be concluded that crop and orchards biomass, and the final products of their pyrolysis, biochar and bio-oil, can be used as raw materials for energy production (directly or as co-combustion feedstock), while part of the produced biochar, which meets the standards also can be used as a soil improver. |
