Fluidized Bed Roaster Research Articles

CFD Study of Roasting Hydrodynamics in Fluidized Bed Roaster of Zinc Sulfide Concentrate

CFD Study of Roasting Hydrodynamics in Fluidized Bed Roaster of Zinc Sulfide Concentrate

Challenges to Treat Complex Zinc Concentrate and Latest Technical Development

The complex zinc concentrate containing high Pb, Cu, SiO2, Na and K, including the Zn-Pb bulk concentrate, cannot be treated in the fluidized bed roaster. The Imperial Smelting Process (ISP) is the main technology to treat this type of concentrate. However, ISP consumes a large amount of coke, which is not only expensive, but also has high CO2 emission.Several metallurgical processes, which can treat the type of complex zinc concentrate and have low CO2 emission, have been reviewed and compared.Recently, a new technology “Flash Burner Roasting Process” has been tested successfully at the industrial scale suspension roaster, and the tests demonstrate that this technology can treat the complex zinc concentrate containing high contents of Pb, Cu and SiO2. The thermodynamic modelling for this process has been done. The industrial test results, the modelling results and the further development are presented in this paper.

Digestion and gut-microbiota fermentation of cocoa melanoidins: An in vitro study

This research aimed to compare the in vitro digestibility and fermentability of melanoidins extracted from cocoa nibs fast-roasted with a fluidized bed roaster (FR-melanoidins), melanoidins from cocoa nibs slow-roasted in a convective oven (SR-melanoidins), and native high molecular weight compounds extracted from unroasted cocoa nibs (UR-HMWC). Data showed that both types of melanoidin extracts, especially FR-melanoidins, better release polyphenols during digestion and earlier produce short-chain fatty acids during in vitro fermentation than UR-HMWC. The delayed catabolism of UR-HMWC resembled that of dense fibers, while FR- and SR-melanoidins resembled oligosaccharides. The production of SCFA was positively correlated with the increase in Bacteroides sp. The profile of the genera identified in the proximal colon showed the differences in fermentability between FR- and SR-melanoidins, with FR-melanoidins having the higher relative growth of nonpathogenic bacteria. This study demonstrated the in vitro digestibility of bound phenolic compounds and the potential prebiotic activity of cocoa melanoidins.

The effect of fluidized bed roaster temperature on the roasted coffee beans antioxidant activity and its sensory evaluation

A fluidized Coffee roaster has been developed. Application of the roaster on coffee beans roasting gave roasted coffee beans with characteristics of being clean and well-roasted. It also could preserve the coffee beans aroma and maintain the antioxidant activity. In this report, the effect of the roasting temperature on the antioxidant activity as well as the aroma and the taste of the roasted coffee beans was examined. The coffee beans used in this experiment were Arabica coffee originating from Tlahap, Temanggung, Indonesia. The roasting conditions were at the temperatures of 205 to 240 °C and it was performed to achieve three degrees of roasted coffee which were light roasts (205 °C), medium roasts (220 °C), and dark roasts (240 °C). The antioxidants were extracted using methanol as a solvent and the antioxidant activity was examined using the scavenging effect method. It was observed that light-roasted coffee, medium-roasted coffee, and dark-roasted coffee have antioxidant activity µg/g BHA equivalent of 58793.333, 39468.000, and 24721.500 respectively. The light-roasted coffee bean was considered the best result with a score of sensory evaluation of 82.25 which is categorized as a specialty grade of coffee.

Fluidized-Bed-Roasted Cocoa Has Different Chemical Characteristics than Conventionally Roasted Cocoa.

The roasting process can modulate sensory and physicochemical characteristics of cocoa. This study compared the chemical characteristics of cocoa nibs roasted by a convective oven [slow roasting─(SR)] vs cocoa nibs roasted in a fluidized bed roaster [fast roasting─(FR)] at two temperatures (120 and 140 °C). The contents of sugars, free amino acids (FAAs), polyphenols, acrylamide, 5-hydroxymethylfurfural, and melanoidins were monitored. Roasting reduced fructose, glucose, and sucrose contents by 95, 70, and 55%, respectively. The concentration of total FAAs was reduced up to 40% at 140 °C. The FAA profile revealed that FR favored the reactivity of some amino acids (Leu, Lys, Phe, and Val) relevant in the formation of aroma compounds and melanoidins. FR resulted in the generation of more intense brown melanoidins, a significant increase in catechin content, a higher formation of acrylamide, and a lower formation of 5-hydroxymethylfurfural in cocoa compared to SR.

Industrial Scale CFD Simulation of Gas–Solid Flow in a Fluidized Bed Roaster of Copper Concentrate

Industrial Scale CFD Simulation of Gas–Solid Flow in a Fluidized Bed Roaster of Copper Concentrate

Fluidized bed roasting modifying the microstructure of cocoa nibs and improving cocoa butter quality

AbstractThe extraction of butter from cocoa seeds involves various processing steps that weaken the lipid‐storing cell walls of cocoa cotyledons. Roasting is particularly critical, making cocoa nibs porous and brittle. In this study, the degree of disruption of the microstructure of cocoa nibs, and the quality and aroma profile of cocoa butter, were evaluated using two roasting techniques, forced convective oven, and fluidized bed. Fluidized bed roasting, recognized for its energy efficiency and low‐carbon footprint, was 12 times faster than oven roasting. This technique allowed a rapid release of steam when parenchyma cell walls were still in a glassy state, while oven roasting caused gradual physical modification allowing the cell wall to become more elastic. Consequently, small pores expanded and coalesced to produce larger pores. X‐ray tomographic analysis showed a total porosity in unroasted cocoa nibs of 8.5 ± 2.0% (vol/vol), which was doubled upon oven roasting and triplicated upon fluidized bed roasting. The higher porosity in fluidized‐bed‐roasted nibs was reflected in the lowest densities and highest cocoa butter yield. Cocoa butter obtained from fluidized‐bed roasted cocoa showed a higher presence of pyrazines and 3‐methylbutanal, and a lower concentration of hydroperoxides, thus enhancing the chocolate flavor and quality. In this paper, we proved that the pore structure of cocoa nibs is a key quality descriptor of roasting processing, and we concluded by quality considerations that fluidized bed roasting technique should be preferred for cocoa nibs roasting over conventional roasting.

Numerical analysis of the Gas − Solid heat transfer characteristics of a lightly calcined MgO Fluidized-bed roaster

The fluidized bed roaster is a novel energy-efficient calcination device for lightly calcined magnesia production. However, the gas − solid heat transfer process in the roaster, the key which can significantly impact energy consumption and product quality, has not an in-depth study yet. In the present work, for the determination of the optimal operating parameters of the roaster, the Euler-Lagrange model of ANSYS Fluent software was employed to simulate the influence of inlet temperature and flow rate of flue gas and feed amount of magnesite on the temperature distribution, production capacity and decomposition rate. The results show that the specific energy consumption is reduced by approximately 6.45 % under the optimal operating conditions with production capacity of 5 × 104 t/a. Furthermore, the maximum production capacity reaches 5.5 × 104 t/a with 9.2 % reduction of specific energy consumption when the feed amount, flue gas flow rate and flue gas temperature are optimized as 14.5 t/h, 21,000 Nm3/h and 1660 K, respectively.

Mineralogical Study of Low and Lean Grade Iron Ore Fines during Slow and Rapid Reduction Roasting

Abstract The present study focuses on the mineralogical aspects and roasting of iron ore (Fe: 55.4%) fines in both fixed bed and fluidized bed roaster. Goethite is the dominant mineral phase in this low-grade iron ore containing hematite, silica and alumina. Such ore was roasted at a constant temperature of 900°C, with non-coking coal of 20% at residence time ranging from 15 to 60 minutes at intervals 15-minute in the fixed bed and 2 to 8 minutes at intervals 2-minute in the fluidized bed reactor. Non-coking coal was utilized as a reductant in the reduction reaction. A high-grade iron ore concentrate was subsequently extracted using Low Intensity Magnetic Separation (LIMS) from the roasted ore. Phase changes in both cases were different due to the difference in the mechanism of reduction. In the fixed-bed reduction roasting phase, transformation occurs as Goethite – Hematite – Magnetite – Wustite, whereas in a fluidized bed, it has followed Goethite – Hematite – Magnetite – Maghemite route. The maghemite phase formed during the fast reduction process due to reoxidation of the reduced magnetite. The wustite phases are reported in the nonmagnetic fractions during LIMS, lowering the yield. On the other hand, the maghemite phase is reported to the magnetic portions. It has a simple cubic structure like magnetite, which increases the yield in the fast reduction roasting process. The results show that 65.85-grade iron ore can be obtained after 30 minutes of residence time with a recovery of 51.5% from the fixed bed and 62.17-grade iron ore can be obtained after 4 minutes of residence time with a recovery of 53.2 % from the fluidized bed.

Fluidized bed roasting of cocoa nibs speeds up processing and favors the formation of pyrazines

Roasting is an important step in cocoa processing causing water loss and generating volatile compounds responsible for chocolate aroma like nitrogen-heterocycles. In this study, the comparison of two techniques, oven roasting, and fluidized bed roasting, in terms of effective water diffusivity (De) and activation energies of formation (Ea) of nitrogen-heterocycles was achieved with cocoa nibs. Fluidized bed roasting, recognized for its energy efficiency and low-footprint synthesis, was 16 times faster than oven roasting. The order of magnitude of De in fluidized-bed-roasted nibs was −8, while it was −9 in the oven-roasted nibs. Moreover, the aw was 50% higher in fluidized-bed-roasted nibs than in the oven-roasted ones. The Ea of nitrogen-heterocycles ranged roughly between 40 and 80 kJ/mol. Those values were lower under fluidized bed roasting than under oven roasting. The more effortless water mobility within fluidized-bed-roasted cocoa demanded lower Ea, and favored the formation of nitrogen-heterocyclics. Industrial relevanceThis study can inspire cocoa manufacturers and equipment designers to pursue the formation of nitrogen-heterocycles during the roasting process of cocoa. It can be done either by adapting and scaling the current fluidized bed coffee roasters to cocoa beans or nibs; or by exploring other alternatives capable of leading enough water diffusivity and water activity in the cocoa nibs, as reported here. These physicochemical conditions undoubtedly boosted the formation of volatile compounds responsible for chocolate aroma, e.g., the pyrazines, without carrying the formation of typical-burn volatile compounds. This natural way of favoring the generation of pyrazines in cocoa nibs could contribute to clean labels by reducing or avoiding the subsequent use of flavorings. The implementation of efficient heat-transfer techniques during roasting, e.g., fluidized bed roasting, could reduce the processing cost and improve sustainability. Studies in the matter of sensory profile, and energy consumption/conversion are called for future research.

A multimode mechanism-guided product quality estimation approach for multi-rate industrial processes

Discrete and delayed laboratory analyses of product quality restrict the operational optimization of industrial processes. However, it is challenging to build an accurate online estimation model for product quality because of complex process dynamics, multiple working conditions, and multi-rate characteristics. Therefore, a multimode mechanism-guided product quality variable estimation model is proposed in this study. First, representative features are extracted from high-dimensional and redundant process variables via both feature engineering and deep learning to describe the internal reaction state. Then, the representative features are used to partition the data samples which are used to train the multi-mode long short-term memory (LSTM) network to increase the adaptability of the estimation model. Finally, the LSTM units are cascaded to learn the variation in the quality variable against time to handle the multi-rate problem. The mechanism models are placed in parallel with the LSTM units to guide the learning process. The estimation model utilizes production data, mechanism knowledge and working condition information, which increases model interpretability and adaptability. A zinc fluidized bed roaster is used to illustrate the proposed estimation approach. The simulation results demonstrate the feasibility and effectiveness of the proposed multi-rate estimation approach.

Effects of roasting on bioavailability and bioactivities of Vigna angularis and potential of coffee-like beverage.

Containing similar aroma and flavor profile of coffee after roasting, Vigna angularis have potential to be a caffeine-free coffee-like beverage. Microwave roasting process was conducted in a microwave oven at 600 W for 7, 14, and 21min at 2-min intervals, and fluidized bed roasting process was conducted in a fluidized bed roaster at 200°C for 9, 18, and 27min. In order to compare the roasted beans, color, fat, ash, crude protein, crude fiber, antioxidant activity, and total phenolic content measurements were performed. In addition, effects of roasting methods on protein bioavailability and antinutritional factors were investigated. Sensory test was conducted to compare the coffee and coffee-like beverages. Fluidized-bed roasted beans had higher scores than microwave roasted beans in terms of sensory acceptability (p ≤ 0.05). Roasting process increased the total phenolic contents up to 25.32 (mg GAE/g) and the protein bioavailability up to 89.82± 0.11%. The results of this study revealed that roasting can be used as a tool to increase nutritive value, bioavailability, antioxidant activity, and potential of coffee-like beverage of V. angularis. PRACTICAL APPLICATION: Since Vigna angularis beans contain similar aroma and flavor profile of the coffee after roasting, they have a potential to be a caffeine-free coffee alternative. Although coffee is very popular in demand, most of the coffee drinkers think that caffeine is very harmful. Having similar sensory scores as coffee beverages in certain roasting degrees, V. angularis beverages could be a delicious caffeine-free alternative.

Batch scale study on magnetizing roasting of low-grade iron ore tailings using fluidized bed roaster

The present steel production of India is 111.24 MTPA in January 2019 as per the Ministry of Steel, Govt. of India. The demand for steel production is increasing day by day. Depleting the high-grade iron ore resources compels steel industries to utilize the low/lean grade iron ore to meet future demand. However, there is no technology available that can directly use these low-grade iron ore. Further, these iron ores are dumped in different mine heads and slime ponds as waste creating environmental and societal problems. Therefore, it is need of the hour to develop suitable scientific methods where these low and lean grade iron ore can be effectively utilized. Magnetizing roasting of this low and lean-grade iron-ore followed by low-intensity magnetic separation can produce high-grade magnetite. The present study focused on the reduction roasting of a tailing iron ore sample having 47.47 %Fe in a batch-type fluidized bed roaster. The roasting of the sample was conducted at a temperature of 1000 °C and varying residence time from 2 to 10 min. Non-coking coal was employed as a reductant for the reduction reaction. The fluidization velocity was maintained at 1.5–1.7 times the minimum fluidization velocity. Then, the roasted sample was subjected to LIMS to obtain a high-grade magnetite concentrate. The study reveals that 61.1-grade iron ore can be obtained at 2 min residence time with 48.4% and 62.5% yield and recovery.

Valorization of roasted longan stone in production of functional biscuits with high antioxidant activity and dietary fiber

Being waste products of the food industry, longan stones can be a promising functional food ingredient owing to their high fiber content, nutrients and antioxidative properties. Biscuits were enriched with roasted and unroasted longan stone powder. The longan stones were roasted at 170 °C for 5, 15, and 25 min by using a fluidized bed roaster. Longan stone powders were incorporated in wheat flours at different concentrations. Biscuits were obtained with higher fiber content (5.72 ± 0.03%) and lower fat content (12.50 ± 0.02%) compared to the control biscuits. Antioxidant activity (51.18 ± 0.02% inhibition) and total phenolic contents (394.61 ± 0.63 mg GAE/100 g) of the biscuits increased significantly as the roasting degree of added longan stone powder increased (p≤0.05). Biscuits enriched with longan stone powder roasted during 15 minutes took higher sensory scores than control biscuits and biscuits enriched with unroasted longan stone powder. The roasting process increased the acceptability of addition longan stone powder.

Estimation of Feeding Composition of Industrial Process Based on Data Reconciliation.

For an industrial process, the estimation of feeding composition is important for analyzing production status and making control decisions. However, random errors or even gross ones inevitably contaminate the actual measurements. Feeding composition is conventionally obtained via discrete and low-rate artificial testing. To address these problems, a feeding composition estimation approach based on data reconciliation procedure is developed. To improve the variable accuracy, a novel robust M-estimator is first proposed. Then, an iterative robust hierarchical data reconciliation and estimation strategy is applied to estimate the feeding composition. The feasibility and effectiveness of the estimation approach are verified on a fluidized bed roaster. The proposed M-estimator showed better overall performance.

Effects of air temperature on the physicochemical properties and flavor compounds of roasted red ginseng lateral roots in a jet impingement fluidized bed roaster

This study aimed to improve the availability of red ginseng lateral roots by applying air jet impingement fluidized bed roasting as a novel processing technology. The effects of air temperature (150 °C, 160 °C, 170 °C, 180 °C, 190 °C, and 200 °C) on the physicochemical properties and flavor compounds of red ginseng lateral roots were investigated. The air roasting time and velocity of the jet impingement fluidized bed roaster were 10 min and 21.68 m s−1, respectively. The moisture content and bulk density significantly decreased, while the total weight loss, expansion index and specific volume significantly increased as the temperature increased (p < 0.05). The extraction yields significantly increased by 38.34% at 200 °C compared with unroasted samples (p < 0.05). The high-temperature roasted sample had larger and more porous structures on their surfaces than the unroasted sample in the scanning electron microscope images. The major ginsenosides (Re, Rg1, Rb1, Rc, Rb2 and Rd) peaked at 150 °C or 160 °C, whereas the minor ginsenosides (Rh1 and Rg2) peaked at 190 °C or 200 °C. Furfural and maltol increased >444 and >10 times in the roasted samples at 200 °C and 170 °C, respectively, when compared with the unroasted samples.

Sensory analysis and mid-infrared spectroscopy for discriminating roasted specialty coffees

In general, the process of roasting coffee uses a rotated fix drum or fluidized bed. Theoretically, the fluidized bed can provide more homogenous roastings throughout the process. Thus, in this study, we analyzed the sensorial and chemical attributes for two different coffees submitted to three roasting profiles using fluidized bed roaster. The coffees were roasted for a high temperature for a short time (HTST), medium temperature for a medium time (MTMT), and low temperature for a long time (LTLT). Sensory analysis was performed on the roasted coffees according to the SCA methodology and chemical analysis through mid-infrared spectroscopy. The results of sensory analysis indicated a preference for MTMT roasting for coffee grown at high altitude and HTST roasting for coffee grown at low altitude. Chemically, coffees show that LTLT and MTMT roasts are most distant from each other in their chemical composition when roasting low altitude coffee, whereas the HTST and MTMT roasts are the most distant from each other when roasting high altitude coffee. Key words: Arabica coffee; Coffee roasting; Infrared spectroscopy; Specialty coffee.

A novel mechanism model of the fluidized bed roaster in the zinc roasting process

A novel mechanism model of the fluidized bed roaster in the zinc roasting process

Comparative evaluation of acrylamide and polycyclic aromatic hydrocarbons contents in Robusta coffee beans roasted by hot air and superheated steam

Although hot air (HA) is a conventional roasting medium for coffee beans, HA roasting is known to result in possible formation of toxic compounds, including acrolein, acrylamide and polycyclic aromatic hydrocarbons (PAHs). Superheated steam (SHS) roasting is therefore proposed as an alternative means to alleviate the formation of these toxic compounds in roasted coffee beans. Robusta coffee beans were roasted either with HA or SHS in a fluidized bed roaster at 210–250 °C until the bean color reached the targeted roast levels. The contents of acrolein, acrylamide and 16 PAHs in the roasted beans were determined; only acrylamide and 5 PAHs were nevertheless found. SHS roasting interestingly resulted in lower acrylamide contents in dark-roasted beans; similar trend was noted in the beans medium-roasted at 250 °C. The contents of three-ring PAHs, namely fluorene, phenanthrene and anthracene, in dark-roasted beans were significantly lower upon SHS roasting at 250 °C.

Effect of roasting speed on the volatile composition of coffees with different cup quality

This study investigated the volatile composition of coffee blends of different cup quality, roasted in an industrial-scale semi-fluidized bed roaster (SFBR) and in a lab-scale fluidized bed roaster (FBR), at three roasting speeds/profiles, to reach medium roast degree. Thirty volatile compounds were selectively investigated. Roasting the specialty coffee blend in both roasters produced lower concentrations of total volatile compounds, compared to the low cup quality blends. Higher concentrations of pyrazines and phenols were observed in low cup quality blends. In SFBR, quality and roasting speed affected all groups of compounds, including impact compounds such as 2,5-dimethylpyrazine, 2-ethylpyrazine, 2,3-dimethylpyrazine, 2-methoxyphenol and 4-ethyl-2-methoxyphenol. In FBR, only phenols were affected. The present results help explain why different roast profiles should be used for coffees with different cup quality for better sensory outcome and why blending should be performed after roasting of green seeds. They also show that results obtained in lab scale roasters are not necessarily reproduced in industry under the same settings.