Bench-scale Unit Research Articles

Process Control Strategies in Chemical Looping Gasification—A Novel Process for the Production of Biofuels Allowing for Net Negative CO2 Emissions

Chemical looping gasification (CLG) is a novel gasification technique, allowing for the production of a nitrogen-free high calorific synthesis gas from solid hydrocarbon feedstocks, without requiring a costly air separation unit. Initial advances to better understand the CLG technology were made during first studies in lab and bench scale units and through basic process simulations. Yet, tailored process control strategies are required for larger CLG units, which are not equipped with auxiliary heating. Here, it becomes a demanding task to achieve autothermal CLG operation, for which stable reactor temperatures are obtained. This study presents two avenues to attain autothermal CLG behavior, established through equilibrium based process simulations. As a first approach, the dilution of active oxygen carrier materials with inert heat carriers to limit oxygen transport to the fuel reactor has been investigated. Secondly, the suitability of restricting the air flow to the air reactor in order to control the oxygen availability in the fuel reactor was examined. Process simulations show that both process control approaches facilitate controlled and de-coupled heat and oxygen transport between the two reactors of the chemical looping gasifier, thus allowing for efficient autothermal CLG operation. With the aim of inferring general guidelines on how CLG units have to be operated in order to achieve decent synthesis gas yields, different advantages and disadvantages associated to the two suggested process control strategies are discussed in detail and optimization avenues are presented.

Influence of high-pressure homogenization on structural properties and enzymatic hydrolysis of milk proteins

This study investigated the effects of HPH processing parameters on the conformational structure of bovine serum albumin (BSA) and whey protein isolate (WPI).BSA and WPI dispersions (1% w/v in phosphate buffer, pH = 7.5) were treated in a bench-scale HPH unit at different pressures (100, 150, 200 MPa) and number of passes (1, 2, 3, 5). The modifications of proteins' primary structure (carbonyl groups), secondary structure (α-helix, β-sheet, turn), tertiary and quaternary structure (free -SH groups) were analyzed together with their particle size distribution (PSD). HPH-assisted hydrolysis with trypsin and α-chymotrypsin was performed (200 MPa, 1 pass). Hydrolysis degree and molecular weight distribution of peptides were determined and compared with those of untreated protein dispersions.HPH treatments did not affect proteins' primary structure while slight modifications of secondary structure were detected. Interestingly, free - SH groups in BSA increased with increasing the pressure due to partial unfolding, while decreased in WPI, possibly due to disaggregation and compaction of native WPI aggregates. HPH pre-treatment allowed enhancing BSA hydrolysis reaction rate, while the compaction of WPI aggregates caused a reduced hydrolysis extent. In conclusion, HPH caused an appreciable modification of protein conformation and affected the degree of enzymatic hydrolysis.

Sustainable hydrogen-rich syngas from steam reforming of bio-based acetic acid over ZnO and CeO2-ZnO supported Ni-based catalysts.

Sustainable hydrogen-rich syngas from steam reforming (SR) of bio-based acetic acid over ZnO and CeO2–ZnO supported Ni-based catalysts was studied by means of a bench-scale fixed-bed unit combined with NDIR/TCD techniques. The effects of Ni/ZnO catalysts with different nickel loadings (5–15%), temperature (T = 500–900 °C), steam to carbon molar ratio (S/C = 1–5) and weight hourly space velocity (WHSV = 3–7 h−1) on SR of acetic acid were explored. In addition, the influence of CeO2 addition on the catalytic performance was assessed to investigate the improvement effect of Ce as a promoter on the catalytic activity. As the nickel loading increased from 5 to 15%, the H2 yield increased significantly from 31.0 to 51.0% with a growth rate of 64.5%, while the CO yield first decreased from 31.6 to 27.7% and then increased to 35.7%. Between 500 and 900 °C, the yields of H2 and CO first increased and then decreased, corresponding to the peak yields of 51.0% and 35.7% at 800 °C, respectively. S/C gave a similar trend of H2 yield to the T, while the CO yield continued to decrease with increasing S/C from 1 to 5. The H2 yield gradually decreased from 54.1 to 28.7% as the WHSV increased, while the peak value of CO yield was 35.7%, corresponding to WHSV = 5. The addition of 25 wt% CeO2 to the Ni/ZnO catalyst with a nickel loading of 15% improved the H2 yield from 51.0 to 74.0% when reforming acetic acid under the optimal operating conditions of T = 800 °C, S/C = 3 and WHSV = 5 h−1. The CO yield was reduced from 35.7 to 33.2%, and the corresponding H2/CO ratio increased from 2.9 to 4.5. The excellent catalyst stability was obtained in the SR of acetic acid using Ni/CeO2–ZnO catalyst. H2 yield was reduced from 76.0 to 73.5% with a decrease of 3.4%, while CO yield increased from 32.1 to 41.3% with a growth rate of 28.7% within 15–360 minutes.

Thermogravimetric kinetic analysis and demineralization of chars from pyrolysis of scrap tire pretreated by waste coal tar

ABSTRACT With the remarkable increase in the number of vehicles worldwide, the disposal of scrap tire is a pressing issue. Pyrolysis is one treatment option to recover resources from the scrap tire, by which pyrolytic char with a high ash and sulfur content is generated, restricting its utilization value. The focus of this study was to improve the quality of the solid product obtained from scrap tire pyrolysis. In this paper, a feasible and effective approach is presented to remove ash from the char using a bench-scale unit. Unlike direct co-pyrolysis of the mixture of scrap tire and other materials, in the study, prior to pyrolysis, the scrap tire was soaked in waste coal tar for a few hours, and then, char was obtained from pyrolysis of the as-prepared scrap tire. According to the comparative analysis of thermogravimetric kinetics of the scrap tire and the as-prepared scrap tire, it revealed that the as-prepared scrap tire was more easily pyrolyzed under relatively low temperature with activation energy of 45.65 kJ/mol and at higher temperature with activation energy of 142.12 kJ/mol. With three kinds of acid (HCl, HNO3, and H2SO4) as the demineralization agent, comparative experiments on the removal of ash from the chars arising from pyrolysis of the as-prepared scrap tire (Char1) and the scrap tire (Char2) were carried out. The results showed that there were the highest efficiencies of ash removal from chars soaked in HCl solution, at 84.9% for Char1 and 59.6% for Char2. With HCl as the demineralization agent, a series of experiments on the removal of ash from Char1 and Char2 was conducted in which the effects of parameters, such as the mass ratio of the acid to the char (L/S), acid concentration, heating temperature, reaction time, stirring rate, particle size of the char, and the number of filtrate cycles, were systematically performed. Under the optimum conditions, the ash removal efficiencies for Char1 and Char2 reached 87.5% and 77.2%, respectively. The kinetics of the char demineralization process was also performed, conforming to a quasi-first-order rate equation. The results obtained indicated that the process of soaking scrap tire in waste coal tar is very useful for removing ash from the char.

Dewatering of Brackish Water and Wastewater by an Integrated Forward Osmosis and Nanofiltration System for Direct Fertigation

Inorganic fertilizers, namely potassium chloride and monoammonium phosphate, have been used as draw solute for dewatering of brackish water and wastewater by forward osmosis (FO). A bench-scale unit with an ultra-low-pressure RO membrane was used. Moderate water flux was achieved for desalination of brackish water and wastewater concentration. Water flux using blended fertilizer was little lower than using individual fertilizers. Low reverse solute flux entailed negligible draw solute replenishment and eliminated eutrophication issues in feed disposal. Reversible fouling was observed with > 90% flux restoration. Partial recovery of draw solute by low-pressure nanofiltration process produced fertilizer solution with NPK content suitable for fertigation and hydroponics without any loss of precious draw solute. The integrated fertilizer-driven FO–NF system proved to be versatile and effective.

Catalytic Steam Reforming of Biomass-Derived Acetic Acid over Two Supported Ni Catalysts for Hydrogen-Rich Syngas Production.

The catalytic steam reforming (CSR) of biomass-derived acetic acid over the commercial Ni-based catalyst (CNC) and the maize stalk ash-supported Ni catalyst (Ni/MSA) for hydrogen-rich syngas production was studied by means of a bench-scale fixed-bed unit combined with NDIR/TCD techniques. A maize stalk ash-supported Ni catalyst was developed for steam reforming of HOAc. The chemical composition and structural characteristics of CNC and Ni/MSA catalysts were compared. Evolution characteristics of H2 and CO during CSR of HOAc were explored. Between 600 and 900 °C, the yields of H2 and CO showed a similar trend over time, which first increased rapidly to the peak value, then began to decrease and finally tended to stabilize. The optimal reaction conditions were as follows: temperature = 800 °C, water to carbon molar ratio (WCMR) = 3, and weight hourly space velocity (WHSV) = 5 h–1. Elevating the reforming temperature up to 900 °C gave rise to the continuously increased H2 yield and enhanced catalyst ability for selective hydrogen production. The percentage of coke deposited on the catalyst decreased by 49.8% with the rise of temperature from 600 to 900 °C. The CO yield continued to decrease with increasing WCMR from 1 to 7. Ni/MSA gave similar CO yield to the CNC. The Ni/MSA exhibited better ability to selectively generate hydrogen than the CNC, resulting in significantly higher hydrogen yield.

Application of metal-organic frameworks in VPSA technology for CO2 capture

One of the technologies that may find application in the reduction of CO2 emissions from both energy and other industrial plants is the adsorption method. Among all adsorption techniques, the Vacuum Pressure Swing Adsorption (VPSA), seems to be the most effective for the separation of CO2 from flue gases, because flue gas is at low pressure. The development of the adsorption method in recent years has been favoured by the intensive development of efficient adsorbents, including metal-organic frameworks (MOFs). Owing to their unique sorption properties and high selectivity, these compounds provide a chance for a considerable reduction of the adsorbent volume, should CO2 be needed to be removed from a huge volume of flue gas. In order to evaluate the possibility of using MOFs, besides zeolites and activated carbon, for CO2 adsorption in large-scale VPSA units, investigations of these compounds in bench-scale and pilot VPSA adsorption units are necessary. In this paper, its authors have carried out investigations into the use of MIL-53(Al) in a bench-scale VPSA installation.. The tests of CO2 separation from a simulated combustion gas mixture on a MIL-53(Al) and on activated carbon and zeolite 13X, respectively, have been carried out in a two-column VPSA installation, which enables adsorbent regeneration in a vacuum. The study also analyzes the effects of adsorption/regeneration time and desorption pressure on CO2 purity and CO2 recovery. The presented results provide new insights into the behaviour of MOFs in the VPSA installation.

Catalyst/Feedstock Ratio Effect on FCC Using Different Catalysts Samples

The present study is a follow-up to a recent authors contribution which describes the effect of the C/O (catalyst/oil) ratio on catalytic cracking activity and catalyst deactivation. This study, while valuable, was limited to one fluidized catalytic cracking (FCC) catalyst. The aim of the present study is to consider the C/O effect using three FCC catalysts with different activities and acidities. Catalysts were characterized in terms of crystallinity, total acidity, specific surface Area (SSA), temperature programmed ammonia desorption (NH3-TPD), and pyridine chemisorption. 1,3,5-TIPB (1,3,5-tri-isopropyl benzene) catalytic cracking runs were carried out in a bench-scale mini-fluidized batch unit CREC (chemical reactor engineering centre) riser simulator. All data were taken at 550 °C with a contact time of 7 s. Every experiment involved 0.2 g of 1,3,5-TIPB with the amount of catalyst changing in the 0.12–1 g range. The resulting 0.6–5 g oil/g cat ratios showed a consistent 1,3,5-TIPB conversion increasing first, then stabilizing, and finally decreasing modestly. On the other hand, coke formation and undesirable benzene selectivity always rose. Thus, the reported results show that catalyst density affects both catalyst coking and deactivation, displaying an optimum C/O ratio, achieving maximum hydrocarbon conversions in FCC units.

Reducing our waste size

Reducing our waste size

Separation of volatile fatty acids from biogas plant hydrolysates

In this study the separation of volatile fatty acids (VFAs) from biogas plant hydrolysates and from each other was investigated. This creates the possibility to make the biogas process more profitable by selling these marketable volatile fatty acids (e.g. butyric acid, caproic acid, valeric acid) as isolates or as highly concentrated mixtures.Four kinds of screw-pressed liquid hydrolysates were used: sugar beet, grass cut and grass-corn hydrolysate from a bench-scale unit as well as a corn-triticale hydrolysate from a real biogas plant. The separation and the concentration of the VFAs were carried out by nanofiltration (NF) and reverse osmosis (RO). It was possible to separate acetic acid from the other acids in the permeate but only in low concentrations (0.25%). All VFAs were enriched in the retentate anyway. With the membrane SWC4 (RO) a total mass concentration enrichment of about factor 19 could be reached (from 7 g/l to 134.6 g/l).A further approach for concentration and separation of the investigated VFAs was their extraction with organic solvents (diethyl ether (DEE), methyl-isobutyl-ketone (MIBK)), followed by a consecutive distillation of the solvent. In this manner it was possible to extract the rather nonpolar butyric acid, valeric acid and caproic acid nearly completely, while the polar, shorter-chain VFAs remained in the aqueous phase. After distillation of the organic solvent, a highly concentrated mixture of butyric acid, valeric acid and caproic acid could be obtained (cVFA;DEE = 805 g/l).As the liquid hydrolysate still contained suspended particles, which possibly could clog the NF and RO membranes and disturb the extraction, tests were carried out to remove these particles by microfiltration (MF) and ultrafiltration (UF). UF membranes with separation limits from 10 kDa to 50 kDa proved to be the best.An assessment of the probably most valuable acid product was carried out against market prices for the individual acids and against calculated possible extractable yields for a hydrolysate of a 250 kW biogas plant.

Scaling prevention of thin film composite polyamide Reverse Osmosis membranes by Zn ions

On the West Coast of South Africa, there is an abundance of brackish groundwater. Reverse Osmosis membrane systems are used to make the borehole water fresh. Unfortunately, the salts that are removed from the water, precipitates on the membrane surface, thus, decreasing the overall process efficiency. In this study, the use of Zn2+ ions as an anti-scalant was investigated in terms of feasibility in the treatment of brackish water influent. Experimental tests were conducted on a bench scale unit, followed with a pilot plant thereafter. Three commercial membranes were exposed to natural groundwater scaling. The first, commercial anti-scalant treatment, second, anti-scalant treatment with Zn2+ ions and the third, untreated. The results, after a period of close to 5 months, showed that the flux of the membranes treated with commercial (32.78 L·m−2·h−1) and zinc (30.80 L·m−2·h−1) ions anti-scalant was higher than the untreated membrane flux (25.56 L·m−2·h−1), which decreased continuously.

Effect of intermittent operation on performance of a solar-powered membrane distillation system

Solar-powered membrane distillation is a promising technology for water desalination, especially in remote arid areas. However, the intermittent nature of solar irradiation restricts the operation of this technology to the daylight hours. Many studies tried to extend the daily operating period but at the expense of increasing complexity and cost. Therefore, most likely the stand-alone solar-powered system will be operated intermittently. This work is focused on studying the effect of the intermittent operation on a solar-powered MD system performance. A set of experiments were carried out on a bench-scale membrane distillation unit. A programmable temperature-controlled circulating bath was used to generate a feed temperature pattern similar to the temperature output of a solar heater in a real pilot solar-powered system. Different operation shutdown procedures (protocols) were examined to identify the best operation protocol for intermittent operation of MD system. The results showed fluctuations in the daily permeate flux and quality. Moreover, the permeate flux was observed to increase with the thermal expansion of the membrane material. There was a gradual deterioration in membrane module performance in terms of salt rejection when the module left to dry overnight. On the other hand, keeping the saline feed inside the module overnight was found to preserve the performance of the module. Ultrasonic cleaning was applied to the used hollow fiber membranes and found to help in recovering their hydrophobicity. This is observed by an increase in the contact angle values of these membranes from 77° to 98°.

Coupling gas flow pattern and kinetics for tyre pyrolysis modelling

A novel strategy has been proposed for the rigorous kinetic modeling of tyre pyrolysis in a conical spouted bed reactor. A kinetic model coupled with a gas flow model was used in the fitting of experimental results obtained in a bench scale unit in the 425–610 °C range. A gas flow model should be incorporated to account for the delay and mixing phenomena observed in tracer experiments, as these phenomena cause remarkable deviations in the assessment of the kinetic parameters. The gas flow pattern from the reactor to the measuring device was modeled using two different approaches based on ideal flow reactors. Furthermore, two kinetic schemes considering lumped products have been proposed; the first one is based on four parallel independent reactions accounting for the volatile products (gas, liquid, aromatics and tar). The second one considers an additional secondary reaction of aromatic formation from the liquid. The strategy proposed for coupling the kinetics and the flow model led to a suitable fitting of the experimental results, with the performance of the model considering a secondary reaction being slightly better than the simple one.

Experimental study on partial oxy-combustion technology in a bench-scale CO2 capture unit

The reduction of CO2 emissions from anthropogenic sources in this century will require a higher reliance on carbon capture and storage (CCS) technologies. Post-combustion based on a regenerative chemical absorption is considered a mature and close-to-market option in near and mid-term. However, the high energy penalty related to solvent regeneration and solvent degradation are two of the main drawbacks hindering the deployment of this technology. Partial oxy-combustion is considered a promising CCS technology that can substantially decrease the reboiler duty due to the increase on the CO2 partial pressure in the flue gas and hence the driving force in the absorber compared to conventional post-combustion approaches. This work explores the potentialities of partial oxy-combustion in a bench-scale CO2 capture unit to evaluate the benefits on the CO2 separation stage. The experimental facility consists of a regenerative CO2 chemical absorption process with a CO2 removal capacity of 0.48 kg/h. The most relevant operating parameters such as temperature, CO2 loading and L/G ratios were evaluated under variations of the CO2 concentration of the flue gas, ranging between 15%v/v and 60%v/v CO2, in order to obtain the optimal reboiler duty associated to the solvent regeneration. Results showed that the use of four packing bed improved the CO2 absorption performance. Although the optimal L/G ratios were moved to higher values, they also achieved CO2 removal efficiencies over 95% and lower energy consumptions compared with the baseline case (post-combustion). Experiments carried out using a 60%v/v CO2 in the flue gas provided 95.7% of CO2 removal efficiency and the lowest reboiler duty (4.74 GJ/t CO2) which resulted in a 57% reduction of the specific energy consumption compared with the post-combustion run.

Power-to-X technology using renewable electricity and carbon dioxide from ambient air: SOLETAIR proof-of-concept and improved process concept

This work demonstrates hydrocarbon production directly from water, solar energy, and air—called SOLETAIR. The plant includes direct air capture (DAC) of carbon dioxide, hydrogen production by water electrolysis, and two-step synthesis bench-scale units that operate using grid-connected solar photovoltaic (PV) electricity. In addition, co-feeding of hydrogen and carbon monoxide from gas bundles are utilized to enable scaling between units. This pilot plant achieved a total operating time of approx. 300 h with a combined production of oil and wax of 6.2 kg per day. The mass and energy balances in integration of the units are studied. According to the experiments and studies, potential and bottlenecks to improve the individual units and their integration are found. Finally, a conceptual Power-to-X plant is presented, which can achieve energy and carbon efficiencies of 47% and 94%, respectively, considering liquid and solid hydrocarbons as products.

Iron Ore Concentrate Particle Size Controlling Through Application of Microwave at the HPGR Feed

Nowadays, the HPGR (high-pressure grinding rolls) is an intermediate step between filtering and balling in the most modern iron ore pelletizing operation. The operation debottlenecks filtering process and reduces pressure over the typical milling process to control particle size to the balling. The present study evaluated aspects of microwave application to the iron ore concentrate fed to HPGR in a bench scale unit. Iron ore concentrate was irradiated varying the microwave exposure time and grinding efficiency was evaluated. The moisture influence in the HPGR efficiency was also assessed. The pellet feed blaine surface area (BSA) improved by 300 cm2/g and % < 325# fraction by 3%. Scanning electron microscope (SEM) images show the formation of micro-cracks onto the particle surface induced by microwave; the effect observed helped improve the milling process performance, in addition to the moisture reduction observed due to the temperature increase.

Biomethane production monitoring and data analysis based on the practical operation experiences of an innovative power-to-gas benchscale prototype

Power-to-gas (P2G) is referred to technologies that convert carbon dioxide into methane. Both bio- and chemical catalysts may be used for conversion purposes. One of the most disruptive biotechnologies was developed by the University of Chicago (IL) (publication number: EP2661511B1), using a robust, highly selective, patented strain of Archaea. Electrochaea GmbH has developed an innovative bench-scale P2G prototype unit, which uses this highly efficient Archaea strain, specialized components and specifically developed control strategies. The structure and the components of the prototype are equivalent with the functional parts of the currently largest commercial scale biomethanation BioCat plant located in Avedøre, Denmark (www.biocat-project.com). Power-to-Gas Hungary Kft. has committed to further develop this innovative technology. The first steps of this development have been taken by operating the benchscale unit and analyzing the data of the operating periods.&#x0D; The prototype is operated based on weekly campaigns. During continuous operation, H2O is generated as a by-product of methane. Therefore, approximately 200 ml of biocatalyst is discharged each day and concentrated media containing macro and micronutrients are injected into the reactor to maintain media composition. The laboratory staff records all gas composition data each morning. The gas composition is measured every 12 minutes by an Awite AwiFlex Cool+ gas analyzer. Within this article, we analyze the collected datasets containing more than 12 000 records and present the first practical experiences of the operations of the innovative power-to-gas bench-scale prototype.&#x0D; The analysis of the collected gas composition data of the product gas already provides important data for modelling the commercial-scaled processes. The average value of VVD was about 40 l/l/d in the period under review. Further increase of the methane content can be achieved by introduction of higher mixing energy and by increasing pressure levels in the bioreactor (as demonstrated in the BioCat plant – data not shown here) – both of which are strategies envisioned for the commercial plant. In routine activities (turn on, shut down, continuous operation) we could verify the high robustness of the biocatalyst and the base connection between the registered datasets and performed test results.

Influence of humic acid on the long-term performance of direct contact membrane distillation

In this study, the influence of humic acid on the treatment of coalbed methane water by direct contact membrane distillation was examined with bench-scale test unit. During short-term distillation (1000 min), high level of humic acid above 50 ppm resulted in significant decrease in permeate flux, while low level of humic acid (∼2 ppm) had little influence on the flux. For the long-term distillation (5000 min), the flux decline began at 3400 min in the presence of 5 ppm humic acid and 5 mM Ca2+, and decreased to ∼40% of initial flux at 5000 min. The spectroscopic analysis of the membrane used revealed that the surface was covered by hydrophilic layers mainly composed of calcite. The membrane fouling effect of humic acid became more significant in the presence of Ca2+ due to more facile calcite formation on the membrane surface. It was demonstrated that humic acid enhanced CaCO3 deposition on the membrane surfaces, thereby expediting the scaling phenomenon.

Techno-economic and environmental evaluation of CO2 mineralization technology based on bench-scale experiments

This work presents a techno-economic & environmental analysis of a CO2 mineralization process, intended to examine its potential for CO2 reduction and economic feasibility. The CO2 mineralization technology of this study is composed of the CO2 carbonation process and the brine electrolysis process, producing various chemical compounds such as sodium bicarbonate, hydrogen, and chlorine. Notably, the CO2 mineralization process is able to utilize flue gas with a low concentration of CO2 that has not been subjected to CO2 capture processes. For the technical feasibility analysis of the CO2 mineralization process examined in the study, performance evaluation is conducted for a bench-scale CO2 mineralization test unit (2 kg/day CO2 utilization capacity), yielding sodium bicarbonate of over 97% purity. It is also estimated that the CO2 utilization process of this study produces 0.65 tons of CO2 emissions per ton of sodium bicarbonate produced, which indicates a 2.09 ton CO2 reduction compared to the conventional processes which produce 2.74 tons of CO2 emissions for the same amount of sodium bicarbonate production. With these results as a basis, an economic evaluation is conducted for a commercial-scale CO2 utilization plant (sodium bicarbonate production capacity: approximately 5000 tons/year) which utilizes CO2 in flue gas produced from thermal power plants. The evaluation supports the economic feasibility of the process with a benefit/cost ratio (B/C ratio) of 1.12 and internal rate of return (IRR) of 10.4%.

Microwave-assisted co-pyrolysis of high ash Indian coal and rice husk: Product characterization and evidence of interactions

In this study, microwave-assisted co-pyrolysis of high ash Indian coal and rice husk is investigated to evaluate the yield and quality of the pyrolysis oil, and to understand the interactions during co-pyrolysis. Microwave co-pyrolysis experiments were conducted in a bench scale unit, and the effects of various parameters such as microwave power (420 W and 560 W), coal:rice husk ratio, and feed:susceptor (graphite) ratio on product yields and oil composition were thoroughly evaluated. Oil yield was not significantly affected by microwave power and feed:susceptor ratio for a particular coal:rice husk ratio. The oil yields were 11 ± 2 wt%, 15 ± 2 wt%, 18 ± 2 wt%, 21 ± 2 wt% and 26 ± 2 wt% for 100:0, 75:25, 50:50, 25:75 and 0:100 wt./wt. coal:rice husk, respectively, at both microwave powers, and followed an additive effect with increase in rice husk amount in the mixtures. Pyrolysis oil contained monoaromatic hydrocarbons, naphthalene derivatives, aliphatic hydrocarbons and phenolic derivatives. The interactions between coal and rice husk pyrolysis intermediates were evidenced in the form of enhanced yields of polyaromatic hydrocarbons with a concomitant reduction in yield of methoxy phenols. Pyrolysis oil from coal had highest heating value (36–38 MJ kg−1) due to the presence of aliphatic hydrocarbons, while that from rice husk had the lowest heating value (28–30 MJ kg−1) due to high oxygenate content. The heating values of co-pyrolysis oils were in the range of 30–36 MJ kg−1. Hydrogen constituted a major fraction in the pyrolysis gases, and the addition of rice husk to coal promoted the evolution of CO.