Pressurized pyrolysis of dried distillers grains with solubles and canola seed press cake in a fixed-bed reactor

Investigation on oxygen-controlled sewage sludge carbonization with low temperature: from thermal behavior to three-phase product properties

A comprehensive study was conducted on the characteristics of oxygen-controlled carbonization process of sewage sludge (SS) using thermogravimetric analysis and lab-scale carbonization experiment. Reaction temperature of SS carbonization was varied between 250 and 650 °C in carrier gas with different O₂ contents. The thermal process of SS in low oxygen could be divided into three stages: dehydration (below 160 °C), devolatilization (160-380 °C), stubborn volatile decomposition and fixed carbon combustion (380-600 °C). Based on Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods, the reaction activation energy (E) of SS carbonization process in 10% O₂ was the lowest, with values of 98.50 kJ mol^-1 (KAS) and 103.49 kJ mol^-1 (FWO). The properties of the obtained char, tar, and gas products were analyzed by FTIR and GC-MS. With the increase of carbonization temperature, char yield decreased and gas yield increased. The highest yield of tar was 27.76% (N₂) and 27.04% (10% O₂) at 450 °C. Low-oxygen atmosphere at the same temperature did not change the yield of char but increased the fixed carbon content and its aromaticity. Oxygen would participate in secondary cracking in tar and promote gas generation above 350 °C. It was found that the presence of oxygen not only increased the concentration of H₂, CO, and CH₄ in gas product, but also improved the quality of tar in terms of high aromatic content and low nitrogen-containing compounds.

Waste-Based Intermediate Bioenergy Carriers: Syngas Production via Coupling Slow Pyrolysis with Gasification under a Circular Economy Model

Waste-based feedstocks and bioenergy intermediate carriers are key issues of the whole bioenergy value chain. Towards a circular economy, changing upcycling infra-structure systems takes time, while energy-from-waste (EfW) technologies like waste pyrolysis and gasification could play an integral part. Thus, the aim of this study is to propose a circular economy pathway for the waste to energy (WtE) thermochemical technologies, through which solid biomass waste can be slowly pyrolyzed to biochar (main product), in various regionally distributed small plants, and the pyro-oils, by-products of those plants could be used as an intermediate energy carrier to fuel a central gasification plant for syngas production. Through the performed review, the main parameters of the whole process chain, from waste to syngas, were discussed. The study develops a conceptual model that can be implemented for overcoming barriers to the broad deployment of WtE solutions. The proposed model of WtE facilities is changing the recycling economy into a circular economy, where nothing is wasted, while a carbon-negative energy carrier can be achieved. The downstream side of the process (cleaning of syngas) and the economic feasibility of the dual such system need optimization.

Progress of the Pyrolyzer Reactors and Advanced Technologies for Biomass Pyrolysis Processing

In the future, renewable energy technologies will have a significant role in catering to energy security concerns and a safe environment. Among the various renewable energy sources available, biomass has high accessibility and is considered a carbon-neutral source. Pyrolysis technology is a thermo-chemical route for converting biomass to many useful products (biochar, bio-oil, and combustible pyrolysis gases). The composition and relative product yield depend on the pyrolysis technology adopted. The present review paper evaluates various types of biomass pyrolysis. Fast pyrolysis, slow pyrolysis, and advanced pyrolysis techniques concerning different pyrolyzer reactors have been reviewed from the literature and are presented to broaden the scope of its selection and application for future studies and research. Slow pyrolysis can deliver superior ecological welfare because it provides additional bio-char yield using auger and rotary kiln reactors. Fast pyrolysis can produce bio-oil, primarily via bubbling and circulating fluidized bed reactors. Advanced pyrolysis processes have good potential to provide high prosperity for specific applications. The success of pyrolysis depends strongly on the selection of a specific reactor as a pyrolyzer based on the desired product and feedstock specifications.

A review on pyrolysis of protein-rich biomass: Nitrogen transformation

Pyrolysis of protein-rich biomass, such as microalgae, macroalgae, sewage sludge, energy crops, and some lignocellulosic biomass, produces bio-oil with high nitrogen (N) content, sometimes as high as 10 wt% or even higher. Major nitrogenous compounds in bio-oil include amines/amides, N-containing heterocycles, and nitriles. Such bio-oil cannot be used as fuel directly since the high N content will induce massive emission of nitrogen oxides during combustion. The present review comprehensively summarized the effects of biomass compositions (i.e., elemental, biochemical, and mineral compositions) and pyrolysis parameters (i.e., temperature, heating rate, atmosphere, bio-oil collection/fractionation methods, and catalysts) on the contents of N and the N-containing chemical components in bio-oil. The migration and transformation mechanisms of N during the pyrolysis of biomass were then discussed in detail. Finally, the research gaps were identified, followed by the proposals for future investigations to achieve the denitrogenation of bio-oil.

Demonstrating the suitability of canola residue biomass to biofuel conversion via pyrolysis through reaction kinetics, thermodynamics and evolved gas analyses

The identification of biomasses for pyrolytic conversion to biofuels depends on many factors, including: moisture content, elemental and volatile matter composition, thermo-kinetic parameters, and evolved gases. The present work illustrates how canola residue may be a suitable biofuel feedstock for low-temperature (<450 °C) slow pyrolysis with energetically favorable conversions of up to 70 wt% of volatile matter. Beyond this point, thermo-kinetic parameters and activation energies, which increase from 154.3 to 400 kJ/mol from 65 to 80% conversion, suggest that the energy required to initiate conversion is thermodynamically unfavorable. This is likely due to its higher elemental carbon content than similar residues, leading to enhanced carbonization rather than devolatilization at higher temperatures. Evolved gas analysis supports limiting pyrolysis temperature; ethanol and methane conversions are maximized below 500 °C with ∼6% water content. Carbon dioxide is the dominant evolved gas beyond this temperature.

The transformation of nitrogen during pressurized entrained-flow pyrolysis of Chlorella vulgaris

The transformation of nitrogen in microalgae during entrained-flow pyrolysis of Chlorella vulgaris was systematically investigated at the temperatures of 600-900 °C and pressures of 0.1-4.0 MPa. It was found that pressure had a profound impact on the transformation of nitrogen during pyrolysis. The nitrogen retention in bio-char and its content in bio-oil reached a maximum value at 1.0 MPa. The highest conversion of nitrogen (50.25 wt%) into bio-oil was achieved at 1.0 MPa and 800 °C, which was about 7 wt% higher than that at atmospheric pressure. Higher pressures promoted the formation of pyrrolic-N (N-5) and quaternary-N (N-Q) compounds in bio-oil at the expense of nitrile-N and pyridinic-N (N-6) compounds. The X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results on bio-chars clearly evidenced the transformation of N-5 structures into N-6 and N-Q structures at elevated pressures. The nitrogen transformation pathways during pyrolysis of microalgae were proposed and discussed.

Pressurized entrained-flow pyrolysis of microalgae: Enhanced production of hydrogen and nitrogen-containing compounds

Pressurized entrained-flow pyrolysis of Chlorella vulgaris microalgae was investigated. The impact of pressure on the yield and composition of pyrolysis products were studied. The results showed that the concentration of H₂ in bio-gas increased sharply with increasing pyrolysis pressure, while those of CO, CO₂, CH₄, and C₂H₆ were dramatically decreased. The concentration of H₂ reached 88.01 vol% in bio-gas at 900 °C and 4 MPa. Higher pressures promoted the hydrogen transfer to bio-gas. The bio-oils derived from pressurized pyrolysis were rich in nitrogen-containing compounds and PAHs. The highest concentration of nitrogen-containing compounds in bio-oil was achieved at 800 °C and 1 MPa. Increasing pyrolysis pressure promoted the formation of nitrogen-containing compounds such as indole, quinoline, isoquinoline and phenanthridine. Higher pyrolysis pressures led to increased sphericity, enhanced swelling, and higher carbon order of bio-chars. Pressurized pyrolysis of biomass has a great potential for poly-generation of H₂, nitrogen containing compounds and bio-char.

Application of biomass pyrolytic polygeneration technology using retort reactors

To introduce application status and illustrate the good utilisation potential of biomass pyrolytic polygeneration using retort reactors, the properties of major products and the economic viability of commercial factories were investigated. The capacity of one factory was about 3000t of biomass per year, which was converted into 1000t of charcoal, 950,000Nm(3) of biogas, 270t of woody tar, and 950t of woody vinegar. Charcoal and fuel gas had LHV of 31MJ/kg and 12MJ/m(3), respectively, indicating their potential for use as commercial fuels. The woody tar was rich in phenols, while woody vinegar contained large quantities of water and acetic acid. The economic analysis showed that the factory using this technology could be profitable, and the initial investment could be recouped over the factory lifetime. This technology offered a promising means of converting abundant agricultural biomass into high-value products.