Process integration and economic analysis of bio-oil platform for the production of methanol and combined heat and power

Process to process material and heat integration strategies for bio-oil integrated gasification and methanol synthesis (BOIG-MeOH) systems were developed to assess their technological and economic feasibility. Distributed bio-oil generations and centralised processing enhance resource flexibility and technological feasibility. Economic performance depends on the integration of centralised BOIG-MeOH processes, investigated for cryogenic air separation unit (ASU) and water electrolyser configurations. Design and operating variables of gasification, heat recovery from gases, water and carbon dioxide removal units, water-gas shift and methanol synthesis reactors and CHP network were analysed to improve the overall efficiency and economics. The efficiency of BOIG-MeOH system using bio-oil from various feedstocks was investigated. The system efficiency primarily attributed by the moisture content of the raw material decreases from oilseed rape through miscanthus to poplar wood. Increasing capacity and recycle enhances feasibility, e.g.1350 MW BOIG-MeOH with ASU and 90% recycle configuration achieves an efficiency of 61.5% (methanol, low grade heat and electricity contributions by 89%, 7.9% and 3% respectively) based on poplar wood and the cost of production (COP) of methanol of 318.1 Euro/t for the prices of bio-oil of 75 Euro/t and electricity of 80.12 Euro/MWh, respectively. An additional transportation cost of 4.28-8.89 Euro/t based on 100 km distance between distributed and centralised plants reduces the netback of bio-oil to 40.9-36.3 Euro/t.     

Comparative analysis of Fischer-Tropsch and integrated gasification combined cycle biomass utilization

Use of agricultural biomass (switchgrass, prairie grasses) through Fischer-Tropsch (FT) conversion to liquid fuels is compared with biomass utilization via (IGCC) integrated gasification combined cycle electrical production. In the IGCC scenario, biomass is co-fired with coal, with biomass comprising 10% of the fuel input by energy content. In this case, the displaced coal is processed via FT methods so that liquid fuels are produced in both scenarios. Overall performance of the two options is compared on the basis of total energy yield (electricity, liquid fuels), carbon dioxide emissions, and total cost. Total energy yield is almost identical whether biomass is used for electrical power generation or liquid fuels synthesis. Carbon dioxide emissions are also approximately equal for the two pathways. Capital costs are more difficult to compare since scaling factors cause considerable uncertainty. With IGCC costs roughly equivalent for either scenario, cost differences between the pathways appear based on FT plant construction cost. Coal FT facility capital cost estimates for the plant scale in this study (721 MW_t LHV input) are estimated to be 410 (MUSD) million US Dollars while the similar scale biomass-only FT plant costs range from 430 MUSD to 590 MUSD.     

Polygeneration and efficient use of natural resources

The consumption of natural resources has been increasing continuously during recent decades, due to the growing demand caused by both the economic and the demographic rise of global population. Environmental overloads that endanger the survival of our civilization and the sustainability of current life support systems are caused by the increased consumption of natural resources—particularly water and energy—which are essential for life and for the socio-economic development of societies. While not yet well utilized, process integration and polygeneration are promising tools which reach the double objective of increasing the efficiency of natural resources, and also minimizing the environmental impact. This paper discusses the concepts of polygeneration and energy integration and various examples of polygeneration systems: (i) sugar and energy production in a sugarcane factory; (ii) district heating and cooling with natural gas cogeneration engines and (iii) combined production of water and energy. It is clearly evident that polygeneration systems which include appropriate process integration significantly increase the efficient use of natural resources.     

Technoeconomic analysis of a methanol plant based on gasification of biomass and electrolysis of water

Methanol production process configurations based on renewable energy sources have been designed. The processes were analyzed in the thermodynamic process simulation tool DNA. The syngas used for the catalytic methanol production was produced by gasification of biomass, electrolysis of water, CO₂ from post-combustion capture and autothermal reforming of natural gas or biogas. Underground gas storage of hydrogen and oxygen was used in connection with the electrolysis to enable the electrolyser to follow the variations in the power produced by renewables. Six plant configurations, each with a different syngas production method, were compared. The plants achieve methanol exergy efficiencies of 59–72%, the best from a configuration incorporating autothermal reforming of biogas and electrolysis of water for syngas production. The different processes in the plants are highly heat integrated, and the low-temperature waste heat is used for district heat production. This results in high total energy efficiencies (∼90%) for the plants. The specific methanol costs for the six plants are in the range 11.8–25.3 €/GJ_exergy. The lowest cost is obtained by a plant using electrolysis of water, gasification of biomass and autothermal reforming of natural gas for syngas production.     

Optimization of two bio-oil steam reforming processes for hydrogen production based on thermodynamic analysis

Thermodynamics of hydrogen production from conventional steam reforming (C-SR) and sorption-enhanced steam reforming (SE-SR) of bio-oil was performed under different conditions including reforming temperature, S/C ratio (the mole ratio of steam to carbon in the bio-oil), operating pressure and CaO/C ratio (the mole ratio of CaO to carbon in the bio-oil). Increasing temperature and S/C ratio, and decreasing the operating pressure were favorable to improve the hydrogen yield. Compared to C-SR, SE-SR had the significant advantage of higher hydrogen yield at lower desirable temperature, and showed a significant suppression for carbon formation. However excess CaO (CaO/C > 1) almost had no additional contribution to hydrogen production. Aimed to achieve the maximum utilization of bio-oil with as little energy consumption as possible, the influences of temperature and S/C ratio on the reforming performance (energy requirements and bio-oil consumption per unit volume of hydrogen produced, Q_D/H2 (kJ/Nm³) and Y_Bio-oil/H2 (kg/Nm³)) were comprehensively evaluated using matrix analysis while ensuring the highest hydrogen yield as possible. The optimal operating parameters were confirmed at 650 °C, S/C = 2 for C-SR; and 550 °C, S/C = 2 for SE-SR. Under their respective optimal conditions, the Y_Bio-oil/H2 of SE-SR is significant decreased, by 18.50% compared to that of C-SR, although the Q_D/H2 was slightly increased, just by 7.55%.     

Effect of mesoporous ZSM-5 morphology on the catalytic performance of cobalt catalyst for Fischer-Tropsch synthesis

Mesoporous ZSM-5 with various morphologies loading cobalt were prepared and applied in Fischer-Tropsch synthesis. Smaller ZSM-5 particles showed higher intensity of strong acid sites resulting in higher cobalt-support interaction. The activity and CH₄ selectivity were remarkably related with cobalt-support interaction over such acidic supports. Cobalt loaded on spindle mesoporous ZSM-5 exhibited the lowest activity and the highest CH₄ selectivity due to the strongest cobalt-support interaction, but the highest activity was obtained over cubic mesoporous ZSM-5 with the lowest cobalt-support interaction originating from weaker acid sites. In addition, adjusting acid intensity and mesopore volumes could successfully tuned hydrocarbon distribution. Spherical ZSM-5 with hierarchical structure containing larger mesopore volumes and moderate acid intensity effectively promoted the production of C₁₂-₁₈ hydrocarbons. The highest C₅-₁₁ selectivity was observed over cobalt supported on hexagonal meso-ZSM-5 due to the enhancement in diffusion limitation over lower mesopore volumes and hydrocracking of primary hydrocarbons over higher Brønsted acid sites.     

Thermodynamic analysis of steam assisted conversions of bio-oil components to synthesis gas

The aim of this study is to investigate the thermodynamics of steam assisted, high-pressure conversions of model components of bio-oil – isopropyl alcohol, lactic acid and phenol – to synthesis gas (H₂ + CO) and to understand the effects of process variables such as temperature and inlet steam-to-fuel ratio on the product distribution. For this purpose, thermodynamic analyses are performed at a pressure of 30 bar and at ranges of temperature and steam-to-fuel ratio of 600–1200 K and 4–9, respectively. The number of moles of each component in the product stream and the product composition at equilibrium are calculated via Gibbs free energy minimization technique. The resulting optimization problems are solved by using the Sequential quadratic programming method. The results showed that all of the model fuels reached near-complete conversions to H₂, CO, CO₂ and CH₄ within the range of operating conditions. Temperature and steam-to-fuel ratio had positive effects in increasing hydrogen content of the product mixture at different magnitudes. Production of CO increased with temperature, but decreased at high steam-to-fuel ratios. Conversion of model fuels in excess of 1000 K favored molar H₂/CO ratios around 2, the synthesis gas composition required for Fischer–Tropsch and methanol syntheses. It was also possible to adjust the H₂/CO ratios and the amounts of CH₄ and CO₂ in synthesis gas by steam-to-fuel ratio, the value depending on temperature and the fuel type. Product distribution trends indicated the presence of water–gas shift and methanation equilibria as major side reactions running in parallel with the steam reforming of the model hydrocarbons.     

Non-catalytic partial oxidation of bio-oil to synthesis gas for distributed hydrogen production

A system has been developed for the volatilization and conversion of a bio-oil mixed with methanol to synthesis gas via non-catalytic partial oxidation (NPOX) using an ultrasonic nozzle to feed the mixture. Such a process would be ideal for distributed H₂ production. The feedstock used was derived from poplar wood. The effects of both temperature (from 625 to 850 °C) and added oxygen (effective O:C ratio from 0.7 to 1.6) on the yields of CO and H₂ have been explored. High yields of CO (between 50% and 70% of the maximum possible from the bio-oil) have been observed. Hydrogen yields are much lower (∼25% of the maximum possible). However, the water formed during NPOX can be used to generate additional H₂. The bio-oil carbon to gas conversion is typically between 85% and 95% for optimal conditions. Due to this significant conversion, lower catalyst loadings are expected to be required for the downstream processing.     

Engineering analysis of uncertainties in the performance evaluation of CHP systems

From January 1, 2011, in all UE countries the combined production of electric (or mechanical) and thermal energy (also called Combined Heat and Power, CHP, or cogeneration) is recognized as a high efficiency technology only when it is able to ensure a minimum value of energy saving with respect to the separate production of the same energy flows. The Directive 8/2004/EC, and a few successive Decisions of the European Commission, introduced a methodology to establish whether any cogeneration plant, existing or new, can be acknowledged as a high-efficiency CHP plant, and can therefore be supported from the UE member states. In the paper, such methodology, based on the evaluation of a standard Primary Energy Saving (PES) index, is briefly described, and then a metrological analysis is presented, in order to evaluate the uncertainties affecting the field evaluation of such index. Three numerical examples are also presented and discussed, referred to natural gas plants, showing that the evaluation of the PES index can be quite critical, especially for values close to the minimum limit fixed by the Directive, and in particular for small and medium scale CHP units, mainly due to the low accuracy that usually affect, in such cases, the measures of the fuel input.     

Optimization of bio-oil steam reforming process by thermodynamic analysis

A straightforward thermodynamic analysis of bio-oil steam reforming was carried out in the context of hydrogen and syngas production, employing Gibbs energy minimization method to determine equilibrium composition and global reaction heat. The bio-oil model compound was a mixture of acetic acid, phenol, and acetone. The effects of process variables, such as temperature and inlet S/C molar ratio, were investigated over a wide range of conditions. Thermodynamic analysis was performed using the software Aspen Plus v.11. It was identified the best operational conditions that could maximize syngas and further hydrogen production considering energy efficiency. The optimum production of hydrogen is 2.28 mol per carbon mole at S/C = 10 and 850 K, and syngas is 2.37 mol per carbon mole at S/C = 10 and 900 K. It has been demonstrated that the equilibrium calculations can be used to simulate these steam reforming reactions, given the catalyst's behavior.     

Characterization of bio-oil and its sub-fractions from pyrolysis of Scenedesmus dimorphus

In the present study, microalgae Scenedesmus dimorphus was reported for pyrolysis in a fixed-bed reactor to determine the effects of temperature on products yield and the chemical compositions of the liquid and solid products. Experiments were carried out at a temperature range of 300–600 °C with heating rate of 40 °C/min and nitrogen flow rate of 100 ml/min. The yield of bio-oil was found to be maximum (39.6%) at the temperature of 500 °C and was further fractionated into n-hexane, toluene, ethyl acetate and methanol sub-fractions by using liquid column chromatography. Various characteristics of bio-oil and its sub-fractions were determined by ¹H NMR, FTIR and GC–MS. The biochar produced as a co-product can be a potential soil amendment with multiple benefits including soil fertility and C-sequestration. The present investigation suggests the suitability of Scenedesmus dimorphus as a potential feedstock for exploitation of energy and biomaterials through pyrolytic conversion.     

Hierarchical porous spinel MFe2O4 (M=Fe,Zn, Ni and Co) nanoparticles: Facile synthesis approach and their superb stability and catalytic performance in Fischer-Tropsch synthesis

The environmental pollution problem and the dwindling in the crude oil resources have been driving considerable researches into alternative routes for the production of clean and low cost liquid fuels. Fischer-Tropsch synthesis (FTS) is a key-technology and a clean alternative for the production of valuable organic chemicals and high standard liquid fuels through the reaction of syngas (CO/H₂). In this study, one-pot hydrothermal reaction was adopted for the synthesis of robust MFe₂O₄ (M = Fe, Zn, Ni and Co) nanoparticles (NPs) with hierarchical porous-structured. The as-synthesized NPs and without the reported necessary pre-calcination step were appointed as robust catalysts in FTS at various reaction temperature (240–290 °C). The obtained catalytic results have demonstrated that CoFe₂O₄ NPs catalyst with its inversed spinel structure exhibited the optimum catalytic activity compared with the type of normal spinel structure of ZnFe₂O₄ catalyst. More precisely, CoFe₂O₄ NPs catalyst showed the best CO conversion ratio of 96% at 290 °C and the highest light-olefin (C₂–C₄) selectivity value of 63%. However, Fe₃O₄ NPs catalyst displayed the highest selectivity toward long chain hydrocarbon product (C₅₊) of 50 wt%, and the lowest CH₄ selectivity value of 12% at 260 °C. Notably, the obtained results from X-ray diffraction and N₂-physisorption characterization for the spent ferrite catalysts demonstrated that the co-existence of the active sites of Hägg iron carbide (χ-Fe₅C₂) and metallic Co phases and along with the high surface area and pore diameter plays the key role for the obtained high catalytic activity in CoFe₂O₄ NPs. Moreover, the produced catalysts in this study exhibited good stability performance within maintained high catalytic activity for a period of at least 700 h of industrial-relevant FTS conditions.     

Process analysis of a novel coal-to-methanol technology for gasification integrated solid oxide electrolysis cell (SOEC)

China's carbon peaking and carbon neutrality goals present a significant challenge for coal chemical technology, which is critical to securing the energy structure. Combining coal chemical industry technology with new energy is an effective approach to transform the development of the coal chemical industry. This paper proposes and studies a novel coal-to-methanol (CTM) technology of gasification integrated solid oxide electrolysis cell (SOEC). SOEC electrolytic hydrogen production technology is an advanced electrolytic water technology with the advantages of large scale and high efficiency, which is very suitable to be combined with industrial technology and can solve the painful problem of H₂ deficiency in the conventional coal to methanol process. In this study, from mechanistic analysis and model simulations, it is observed that by increasing the SOEC capacity, the novel CTM system can create more methanol at the same coal consumption and simultaneously reduce CO₂ emissions. The novel CTM system can produce up to 2.2 times more methanol and reduce CO₂ emissions by 94% by replacing the water-gas-shift (WGS) process with the SOEC unit. The novel CTM increases energy consumption. In addition, the novel CTM technology will effectively improve the economics of coal to methanol, taking into account the carbon tax. At the methanol price of 2900 RMB/t and SOEC capacity of 250 MW, the economic benefits of novel CTM were 2.1 times greater than CTM technology.     

Integration of solid oxide electrolyser,entrained gasification,and Fischer-Tropsch process for synthetic diesel production: Thermodynamic analysis

A novel integrated renewable-based energy system for production of synthetic diesel is proposed and simulated in this study. This system merges solid oxide electrolyser (SOE), entrained gasification (EG) and Fischer-Tropsch (FT) technologies. Two case scenarios are considered here. In the first case, the electrolyser unite produce syngas through co-electrolysis of steam and carbon dioxide, while in the second case only steam is electrolyzed. The effects of SOEC and EG operating pressure and temperatures on the system performance in each case are investigated and compared. It is shown that the operating condition of electrolyser subsystem has a more considerable effect on the performance of the integrated system as compared to the gasification subsystem. Also waste heat recovery results in about 43 and 2 percentage point increase in energy and exergy efficiency, respectively. It is also shown that internal recovering of oxygen has the best effect on the system performance.     

Nickel based monometallic and bimetallic catalysts for synthetic and real bio-oil steam reforming

Catalysts based on Ni supported on alumina were studied for steam reforming (SR) of a synthetic bio-oil/bio-glycerol mixture and a real bio-oil. Catalyst tests were carried out in a continuous fixed bed reactor at atmospheric pressure and steam to carbon (S/C) ratio of 5.0. In the case of experiments with the bio-oil/bio-glycerol mixture the initial temperature was 1073 K, then it was successively changed to 973 K and 1073 K again to assess catalyst deactivation. Experiments with the bio-oil sample were run at 1073 K. First, the effect of modifications to the alumina support with CeO₂ and La₂O₃ was studied in monometallic catalysts. Ni/CeO₂Al₂O₃ was identified as the catalyst more resistant to deactivation, likely due to its higher oxygen mobility, and selected for further tests. Then, bimetallic catalysts were produced by impregnation of noble metals (Pd, Pt or Rh) on the Ni catalyst supported on CeO₂Al₂O₃. Co-impregnation of Rh and Ni on the CeO₂Al₂O₃ support represented a further improvement in the catalytic activity and stability respect to the monometallic catalyst, leading to stable gas compositions close to thermodynamic equilibrium due to the favourable RhNi interactions. RhNi/CeO₂Al₂O₃ is therefore a promising catalyst to produce a hydrogen-rich gas from bio-oil SR.     

Techno-economic analysis of a coal-fired CHP based combined heating system with gas-fired boilers for peak load compensation

Combined heat and power (CHP) plants dominate the heating market in China. With the ongoing energy structure reformation and increasing environmental concerns, we propose gas-fired boilers to be deployed in underperforming heating substations of heating networks for peak load compensation, in order to improve both energy efficiency and environmental sustainability. However, due to the relatively high price of gas, techno-economic analysis is required for evaluating different combined heating scenarios, characterized by basic heat load ratio (β). Therefore, we employ the dynamic economics and annual cost method to develop a techno-economic model for computing the net heating cost of the system, considering the current state of the art of cogeneration systems in China. The net heating cost is defined as the investment costs and operations costs of the system subtracted by revenues from power generation. We demonstrate the model in a real-life combined heating system of Daqing, China. The results show that the minimum net heating cost can be realized at β=0.75 with a cost reduction of 16.8% compared to coal heating alone. Since fuel cost is the dominating factor, sensitivity analyses on coal and gas prices are discussed subsequently.     

A thermodynamic equilibrium analysis of hydrogen and synthesis gas production from steam reforming of acetic acid and acetone blends as bio-oil model compounds

Thermodynamic analysis of steam reforming of blends of two model oxygenates, acetic acid and acetone, representing carboxylic acids and ketones in bio-oil is performed to investigate the effects of their potential interactions on hydrogen yield, synthesis gas composition and progress of reaction network. The results show that both acetic acid and acetone reach complete conversion at all operating conditions. Higher S/C molar ratio results in higher H₂ and CO₂ yields for both acetic acid and acetone. With the increase in pressure, H₂ and CO yields are diminished whereas CH₄ and CO₂ yields are enhanced. H₂ and CO₂ yields increase with the decrease in acetone concentration in the feed blend. CO and CH₄ production are affected adversely for acetic acid rich blends. The maximum H₂ yield values are 75.54%, 78.34%, 80.09%, 81.78% and 84.17% at 700 °C for acetic acid/acetone blends of 0.0/1.0, 0.3/0.7, 0.5/0.5, 0.7/0.3 and 1.0/0.0, respectively.     

Catalyst deactivation and regeneration during CO2 reforming of bio-oil

Catalyst deactivation and regeneration during CO₂ reforming of bio-oil were researched in this paper. The results of XRD, TG and SEM analyses showed that the catalyst deactivation was a combination of carbon deposition and sintering. There were amorphous carbon and filamentous carbon on the catalyst surface, but amorphous carbon was the main carbon product, which was the main reason for the catalyst deactivation. The activity and stability of steam regeneration catalyst is superior to that of CO₂ and air regeneration catalyst, but steam regeneration process will consume much quantity of steam, which can be increased production cost. Air regeneration method is easy to sinter the center of catalyst. CO₂ regeneration process not only produces useful gases (C + CO₂ = 2CO), but also makes good use of greenhouse gases, which has an industrial application prospect. However, with the cycle of catalyst increasing, the activity and stability catalyst will decrease gradually during the CO₂ reforming process.     

Combustion characteristics of bio-oil from swine manure/crude glycerol co-liquefaction by thermogravimetric analysis technology

The thermal analysis and kinetics of bio-oils derived from swine manure/crude glycerol co-liquefaction were studied by thermogravimetric analysis (TGA) in the air. It was found that the combustion processes of bio-oils can be divided into three stages, with most of the materials decomposing between 330 and 370°C. In kinetic calculations, oxidation of the bio-oils was determined using the Coats–Redfern method, considering that bio-oil combustion occurs in three consecutive steps. Four models including more than 12 alpha functions were tested to fit the study’s experimental results. The calculation shows that the diffusion models are the best fit for describing the bio-oil combustion process in the air.     

Biomass-derived syngas production via gasification process and its catalytic conversion into fuels by Fischer Tropsch synthesis: A review

The Fischer–Tropsch (FT) synthesis has been investigated over decades as an alternative route to obtain synthetic fuels from synthesis gas. FT is a high-performance synthesis based on metallic catalysis, mainly using ruthenium, cobalt and iron catalysts, which converts syngas in hydrocarbons and chemical precursors. This work presents a review on the aspects of the syngas production from biomass gasification and its subsequent conversion into fuels through the Fischer-Tropsch synthesis. The usage of biomass, including lignocellulosic residues, as a raw material in the gasification process. Biosyngas is highlighted as a synthetic fuel source to replace nonrenewable, conventional fossil fuels. Lignocellulosic material must be considered a low-cost feedstock to the liquid biofuel production on a large scale. Studies on syngas cleaning to attain the purity required by the FT process is revised. Recent understanding of reaction kinetics and thermodynamics has contributed to increasing the FT performance and economic viability. This paper includes also the debate on main catalysts, industrial process requirements, and chemical reaction kinetics and mechanisms of Fischer–Tropsch synthesis.