Pyrolysis and combustion behaviour of coal-MBM blends

Thermogravimetric and Kinetic Analysis of High-Temperature Thermal Conversion of Pine Wood Sawdust under CO2/Ar

The gasification behavior of pine wood sawdust was investigated in CO2 with different heating rates of 5, 10, 15, and 20 °C/min from room temperature to 1400 °C by thermogravimetric analysis (TGA) and mass spectrometry (MS). It was also examined under Ar to compare the differences observed under CO2 at heating rate of 10 °C/min. Kinetics of pine wood sawdust thermal decomposition was determined by the models of FWO, KAS and master plot method. TGA results revealed different reaction sections from pyrolysis to char gasification under CO2. The pyrolysis behavior was similar under CO2 and Ar and had a similar energy required value about 590 kJ/kg from 250 °C to 420 °C. CO, CH4, and H2 were the primary gases obtained from thermal decomposition, and the amounts of which in CO2 atmosphere were higher than those obtained in Ar. The average activation energy for pyrolysis under CO2 was 184.72 kJ/mol.

Hydrothermal liquefaction (HTL) of animal by-products: Influence of operating conditions

Hydrothermal liquefaction (HTL) of Animal By-Products (ABP) is a promising technology for their recycling and disposal. Different operating parameters have been studied to determine their influence on the process. Higher heating values of biocrudes ranging between 35 and 39 MJ/kg have been obtained showing a maximum yield of 61% at 225 °C. At low HTL temperature, the products are similar to those of rendering process and the biocrude is mainly formed by triglycerides and fatty acids in a 90:10 ratio, approximately. By increasing temperature, the free fatty acid yield increases, as well as amides and heterocyclic compounds as a result of the triglycerides and protein reactions. Between 250 and 290 °C a great difference in the composition of the biocrude obtained is observed. Water content also showed significant effects on the product yields. Large amounts of foams were obtained at low water contents that were minimised when it is increased. This is a very important feature to be considered for scaling up the phase separation process. Glycerine amount in the aqueous phase was remarkable, as a consequence of fat hydrolysis. Increasing pH to 9 increases the extraction of organics into the aqueous phase, whereas operating at pH 5 yields similar amounts of biocrude as compared with neutral pH, with a higher percentage of fatty acids. Reusing of the aqueous phase is necessary for the viability of the process and leads to increasing amounts of dissolved organics in the aqueous phase with the number of cycles, reaching a saturation level after three-four recycling rounds.

Influence of pork and bone on product characteristics during the fast pyrolysis of pig carcasses

The characteristics of the products of pig carcass pyrolysis depend on initial feedstock composition, specifically tissue and bone, as well as the interaction between these components. In this work, the raw pork (RP), pig bone (PB), and a mixture of RP and PB to simulate pig carcasses with a mass ratio of 2:1 (RB21) were pyrolyzed at 650 °C and compared to investigate pig carcass pyrolytic product characteristics. The presence of minerals in PB was found to increase the gaseous product yields of RB21 by 16%, especially the CO₂, C₂H₄ and C₂H₆ yields through steam gasification and steam reforming reactions. These minerals also affect tar product distribution, promoting the cracking of long chain hydrocarbons and the cyclization reaction of hydrocarbons, esters, amides/nitriles to produce more aromatic, O-heterocyclic and N-heterocyclic compounds, respectively. The Brunauer-Emmett-Teller (BET) surface area of pyrolytic RB21 char is 134.025 m²/g and it is a porous material rich in minerals like Ca, P, and K. The addition of RP causes more wrinkles on the surface and reduces its mesopore diameter from 6.263 nm to 5.412 nm. The Ca and P in char are derived from hydroxyapatite occurring in PB, and K presents in RP participates in the crystallization of RB21 char, forming a new crystal compound Ca₈H₂(PO₄)₆·KHCO₃.

Combustion characteristics and air pollutant formation during oxy-fuel co-combustion of microalgae and lignite

Oxy-fuel combustion of solid fuels is seen as one of the key technologies for carbon capture to reduce greenhouse gas emissions. The combustion characteristics of lignite coal, Chlorella vulgaris microalgae, and their blends under O2/N2 and O2/CO2 conditions were studied using a Thermogravimetric Analyzer-Mass Spectroscopy (TG-MS). During co-combustion of blends, three distinct peaks were observed and were attributed to C. vulgaris volatiles combustion, combustion of lignite, and combustion of microalgae char. Activation energy during combustion was calculated using iso-conventional method. Increasing the microalgae content in the blend resulted in an increase in activation energy for the blends combustion. The emissions of S- and N-species during blend fuel combustion were also investigated. The addition of microalgae to lignite during air combustion resulted in lower CO2, CO, and NO2 yields but enhanced NO, COS, and SO2 formation. During oxy-fuel co-combustion, the addition of microalgae to lignite enhanced the formation of gaseous species.

Residues from the thermal conversion of waste from the meat industry as a source of valuable macro- and micronutrients

The increased consumption of meat (including poultry) observed over the last decade has led to the intensification of its production. With the production increase, the amount of generated waste also increases. Appropriate disposal of waste from the meat industry will significantly reduce the amount of such waste and its negative impact on the environment. The paper presents a method for the thermal neutralisation of feathers, poultry litter and meat and bone meal (MBM). Waste incineration was carried out in a stationary electric furnace, at a temperature varying in the range of 600-900°C. The resulting ashes were characterised by a high percentage of phosphorus (30-170 g/kg ash), calcium (20-360 g/kg ash) and other valuable macro- and micronutrients like copper, iron, manganese and zinc. The ashes produced during the thermal treatment are safe in terms of sanitary and can be used as additives enriching the fertilisers and soil improvers.

Impact of blend ratio on the co-firing of a commercial torrefied biomass and coal via analysis of oxidation kinetics

Incorporation of torrefied biomass into coal-fired power plants could potentially lower the SOx and net CO2 emissions resulting from electricity generation. However, concerns over lower heating values and slightly higher ash content of torrefied biomass suggest that blending it with coal in industrial boilers may be preferable to complete fuel transition. By studying the oxidation kinetics of coal-torrefied biomass blends in a thermogravimetric analyzer at a heating rate of 100°C/min, we find an additive nature among the fuels for peak mass loss rates and enthalpies of combustion. The activation energy required to initiate decomposition decreases from 132.6 to 77.6 kJ/mol as the torrefied biomass increases from 0 to 100 wt%, with a sharp decrease between 0 and 40 wt%. Data suggest that incorporation of torrefied biomass into coal-fired boilers is dependent on the ability to sacrifice heating value for the lower emissions of SOx and net CO2 garnered using bio-coal.

Pyrolysis and gasification of meat-and-bone-meal: energy balance and GHG accounting

Meat-and-bone-meal (MBM) produced from animal waste has become an increasingly important residual fraction needing management. As biodegradable waste is routed away from landfills, thermo-chemical treatments of MBM are considered promising solution for the future. Pyrolysis and gasification of MBM were assessed based on data from three experimental lab and pilot-scale plants. Energy balances were established for the three technologies, providing different outcomes for energy recovery: bio-oil was the main product for the pyrolysis system, while syngas and a solid fraction of biochar were the main products in the gasification system. These products can be used - eventually after upgrading - for energy production, thereby offsetting energy production elsewhere in the system. Greenhouse gases (GHG) accounting of the technologies showed that all three options provided overall GHG savings in the order of 600-1000kg CO2-eq. per Mg of MBM treated, mainly as a consequence of avoided fossil fuel consumption in the energy sector. Local conditions influencing the environmental performance of the three systems were identified, together with critical factors to be considered during decision-making regarding MBM management.

Environmental impact of incineration of calorific industrial waste: rotary kiln vs. cement kiln

Rotary kiln incinerators and cement kilns are two energy intensive processes, requiring high temperatures that can be obtained by the combustion of fossil fuel. In both processes, fossil fuel is often substituted by high or medium calorific waste to avoid resource depletion and to save costs. Two types of industrial calorific waste streams are considered: automotive shredder residue (ASR) and meat and bone meal (MBM). These waste streams are of current high interest: ASR must be diverted from landfill, while MBM can no longer be used for cattle feeding. The environmental impact of the incineration of these waste streams is assessed and compared for both a rotary kiln and a cement kiln. For this purpose, data from an extensive emission inventory is applied for assessing the environmental impact using two different modeling approaches: one focusing on the impact of the relevant flows to and from the process and its subsystems, the other describing the change of environmental impact in response to these physical flows. Both ways of assessing emphasize different aspects of the considered processes. Attention is paid to assumptions in the methodology that can influence the outcome and conclusions of the assessment. It is concluded that for the incineration of calorific wastes, rotary kilns are generally preferred. Nevertheless, cement kilns show opportunities in improving their environmental impact when substituting their currently used fuels by more clean calorific waste streams, if this improvement is not at the expense of the actual environmental impact.

Cultivation and characterization of Cynara Cardunculus for solid biofuels production in the Mediterranean region

Technical specifications of solid biofuels are continuously improved towards the development and promotion of their market. Efforts in the Greek market are limited, mainly due to the climate particularity of the region, which hinders the growth of suitable biofuels. Taking also into account the increased oil prices and the high inputs required to grow most annual crops in Greece, cardoon (Cynara cardunculus L.) is now considered the most important and promising sources for solid biofuel production in Greece in the immediate future. The reason is that cardoon is a perennial crop of Mediterranean origin, well adapted to the xerothermic conditions of southern Europe, which can be utilized particularly for solid biofuel production. This is due to its minimum production cost, as this perennial weed may perform high biomass productivity on most soils with modest or without any inputs of irrigation and agrochemicals. Within this framework, the present research work is focused on the planning and analysis of different land use scenarios involving this specific energy crop and the combustion behaviour characterization for the solid products. Such land use scenarios are based on quantitative estimates of the crop'sproduction potential under specific soil-climatic conditions as well as the inputs required for its realization in comparison to existing conventional crops. Concerning its decomposition behaviour, devolatilisation and char combustion tests were performed in a non-isothermal thermogravimetric analyser (TA Q600). A kinetic analysis was applied and accrued results were compared with data already available for other lignocellulosic materials. The thermogravimetric analysis showed that the decomposition process of cardoon follows the degradation of other lignocellulosic fuels, meeting high burnout rates. This research work concludes that Cynara cardunculus, under certain circumstances, can be used as a solid biofuel of acceptable quality.

Characteristics of industrial and laboratory meat and bone meal ashes and their potential applications

This paper reports the characterization of four meat and bone meal (MBM) ashes obtained from specific incineration (laboratory) and from co-incineration (industrial process). Three out of the four MBM ashes were mainly composed of calcium phosphates (hydroxyapatite and whitlockite). Their compositions (major and trace) were in the range for natural phosphate rocks. Trace element contents, including heavy metals, were below 0.6% and industrial ashes contained much more heavy metals than laboratory ash. The amounts of leached elements were low, especially for laboratory ash. According to the European classification of waste to be landfilled, the laboratory ash can be classified as an inert waste. Two industrial ashes are mostly inert. Only one ash is highly leachable and needs a stabilization treatment to be classified at least in the category of hazardous waste. It seems, from these results, that possibilities other than landfilling could be considered to give economic value to these ashes.

Co-firing coal with rice husk and bamboo and the impact on particulate matters and associated polycyclic aromatic hydrocarbon emissions

The potential of co-firing rice husk and bamboo with coal was studied in a bench-scale pulverized fuel combustion reactor. Experimental parameters including biomass blending ratio in the fuel mixture, biomass grinding size, excess air ratio and relative moisture content in the biomass were investigated. Particulate Matters in the forms of PM(10), PM(2.1), ultra fine particles as well as the associated Polycyclic Aromatic Hydrocarbons (PAHs) emissions were evaluated. An operation range between 10% and 30% of biomass to coal ratio was found to be the optimum range in terms of minimum pollutant emissions per unit energy output. Co-combustion of coal with biomass seemed to have the effect of moving the fly-ash in PM(2.1) to a larger size range, but increasing the number counts of the ultra fine particles. It was noted that the much higher volatile matter content in the biomass fuels has played a key role in improving the combustion performance in the system. However, slagging, fouling and formation of clinker could be the issues requiring attention when using biomass co-combustion in conventional boilers.

Evaluation of meat and bone meal combustion residue as lead immobilizing material for in situ remediation of polluted aqueous solutions and soils: "chemical and ecotoxicological studies"

As a result of bovine spongiform encephalopathy (BSE) crisis, meat and bone meal (MBM) production can no longer be used to feed cattle and must be safely disposed of or transformed. MBM specific incineration remains an alternative that could offer the opportunity to achieve both thermal valorization and solid waste recovery as ashes are calcium phosphate-rich material. The aim of this work is to evaluate ashes efficiency for in situ remediation of lead-contaminated aqueous solutions and soils, and to assess the bioavailability of lead using two biological models, amphibian Xenopus laevis larvae and Nicotiana tabaccum tobacco plant. With the amphibian model, no toxic or genotoxic effects of ashes are observed with concentrations from 0.1 to 5 g of ashes/L. If toxic and genotoxic effects of lead appear at concentration higher than 1 mg Pb/L (1 ppm), addition of only 100 mg of ashes/L neutralizes lead toxicity even with lead concentration up to 10 ppm. Chemical investigations (kinetics and X-ray diffraction (XRD) analysis) reveals that lead is quickly immobilized as pyromorphite [Pb10(PO4)6(OH)2] and lead carbonate dihydrate [PbCO(3).2H2O]. Tobacco experiments are realized on contaminated soils with 50, 100, 2000 and 10000 ppm of lead with and without ashes amendment (35.3g ashes/kg of soil). Tobacco measurements show that plant elongation is bigger in an ashes-amended soil contaminated with 10000 ppm of lead than on the reference soil alone. Tobacco model points out that ashes present two beneficial actions as they do not only neutralize lead toxicity but also act as a fertilizer.