Final Product Temperature Research Articles

Demonstration of a Pilot-Scale Plant for Biomass Torrefaction and Briquetting

Abstract. A semi-mobile torrefaction and densification pilot plant was constructed in order to determine ideal operating conditions and evaluate briquette quality and throughput rate using forest residuals as the input feedstock. Experiments were conducted at various conditions with feedstock moisture content ranging from 4% to 25% (wet basis), reactor residence times of 10 and 20 min, and final product temperatures between 214°C and 324°C. Optimal operating conditions, evaluated based on throughput rate, specific electricity demand, torrefied briquette grindability, briquette volumetric energy density, and briquette durability, were identified to occur with a short residence time (10 min), low feedstock moisture content (<11% wet basis), and high final product temperature between 267°C and 275°C. These conditions were able to process 510 to 680 kg h-1 (wet basis) feedstock with a dry mass yield of 79% to 84% to produce torrefied biomass with a higher heating value of 21.2 to 23.0 MJ kg-1 (dry basis) compared to 19.6 MJ kg-1 for the original biomass. Torrefied briquettes produced at these conditions had a neatly stacked packing density of 990 kg m-3 and a volumetric energy density of 21,800 MJ m-3. Their specific grinding energy was an average 37% of the energy required to grind a raw biomass briquette. These torrefied briquettes were more durable (94% DU) than raw briquettes (85% DU) directly following production, but were less durable after undergoing temperature and humidity fluctuations associated with long distance transportation (74% DU for torrefied and 84% DU for raw biomass briquettes). Results from this pilot plant are promising for commercial scale production of high quality torrefied briquettes and should lead to additional research and development of a torrefaction system optimized for a higher throughput rate at these conditions. Keywords: Biomass, Biomass conversion technology, Bioenergy, Briquetting, Densification, Forest residuals, Pyrolysis, Torrefaction.

مقایسه ویژگی های کیفی برگه خرمالو خشک شده به دو روش هوای داغ و مادون قرمز

Introduction: One of the most important aspects of food preservation is controlling the moisture of material such as fruits.Dryingis considered as important method to controlbacteriasafely using reduction of moisture. The hot air drying method has been widely adopted in manufacturing of conventional dried food.Nowadays, Infrared radiation (IR) has significant advantages over conventional drying. Among these advantages,higher drying rates giving significant energy savings anduniform temperature distribution giving a better quality of product. Therefore, it can be used as an energy saving drying method. Earlier attempts forapplying infrared waves to drying of agricultural materials have been reported in the literatures, such as banana, onion, garlic, apple, corn, pomegranate seeds and peach. The persimmon (Diospyros kaki) is native to East Asia, most likely China. This fruit has very short shelf-life; it is due to thehigh soluble tannin content of the fruit during storage even at refrigerated conditions. The persimmon is mainly eaten fresh, but can be dried.Duringdrying the tannin cells coagulate, so astringency is removed and the sugars in the fruit exude to the surface where they crystallize, thus producing a sweet, candied product. The objective of this study was to examine the drying behavior of the far infrared and hot- air drying of persimmon slices by comparing the physical quality. Materials and methods: Persimmon (Diospyros kaki) used in this study was purchased from a local market (KhorasanRazavi, Mashhad). The whole samples were stored at 4°C. The initial moisture content of persimmon was found to be 78.2 kg H2O/kg moisture. The sampleswerecut into 5mm slices using a cutting machine and were dried to 10% final moisture (wet basis). - Infrared dryer setup: Infrared (IR) dryer used in this research was equipped with IR lamp (1300W). Persimmon slices were placed in a single layer on the drying tray and heated from one side. Thermocouples (Type K) were inserted at the center of persimmon slice.IR drying tests were conducted with final product temperatures controlled at 50°C, 60°C and 70°C. -Hot air dryer setup: Persimmon slices were arranged in a single layer on the trays and dried in cabinet dryer at material temperatures of 50°C, 60°C and 70°C.Air velocity in the dryer was 1.5 m/s. -Quality evaluation: Persimmon slice drying characteristics including rehydration ratio, color parameters, shrinkage, texture and sensory properties were investigated ResultsandDiscussion: It is clear that the moisture content and drying rate decrease continuously with drying time. The drying rate was rapid during the initial period but it became very slow at the last stages of dryingprocess. Persimmonslices dried with hot-air and infrared dryer at temperatures 60 and 70◦c respectively, had a maximum rehydration ratio. In general, infrared drying showed significant effect on L value (p<0.05) and slices dried in 70°C were found to have maximum L values (64.33).Due to the reduction of browning reactions byIR heating, b vales of samples were reduced. The lowest content of shrinkage was observed in infrared dried samples at 50°C. Results of sensory evaluation showed that infrared dried samples are more acceptable and obtained higher score comparing to hot-air dried samples. Conclusion: In conclusion, our results showed thatthe IR drying had much higher drying rate compared to the hot air drying. Its drying rate increased remarkably with increasing of the radiation intensity. Infrared drying of persimmon slices is an effective method of water removal. Drying with application of infrared energy is much faster than convective drying(under equivalent parameters). Beside, IR radiation did not cause any negative impact on characteristics and quality dried sample. Besides, IR drying methods dramatically reduced the drying temperature.

Simplified heat transfer modeling in a cold room filled with food products

High product and air temperatures and moistures are often observed in certain positions of a cold room leading to deterioration of food quality and safety. To reduce food losses, it is necessary to understand heat and mass transfers. However, these transfers are complex phenomena because of the presence of the product (airflow obstacle, heat of respiration…) and the coupling between the transfers and airflow. Temperature and velocity measurements were carried out in a ventilated cold room filled with four apple pallets. Because of the room small dimensions (3.4×3.4×2.5m), the cold supply air headed directly to the rear part of the room. Therefore, the rear pallets were submitted to lower air temperatures compared to the front ones. This leads to more rapid product cooling rate and lower product final temperature at the rear. A simplified model was developed. It describes the evolution of product and air temperatures at different zones in the cold room. Good agreement between the predicted and experimental results was found for both product cooling rate and final product temperature.

Investigation of Pre-milling Effect on Synthesis of Ti5Si3 Prepared by MASHS, SHS, and MA

Ti5Si3 was fabricated by self-propagating high-temperature synthesis (SHS), mechanical-activated SHS (MASHS), and mechanical alloying with the aim of investigating the effect of milling energy on final product. For MASHS process, Ti and Si as starting materials were milled by high energy ball milling, with ball-to-powder weight ratio (BPR) of 10:1, for different times (1, 3, and 6 h), then pressed to form pellets. Green compacts were placed in a tube furnace preheated to three different temperatures of 1000, 900, and 800 °C with argon atmosphere for the synthesis. The milled and synthesized powders were characterized by means of XRD and SEM. The results showed that Ti5Si3 was not formed during milling up to 3 h, after that a trace of Ti5Si3 peaks can be detected from XRD pattern. The increase in milling time prior the combustion reaction caused a decrease in the crystallite size of the final product and ignition temperature of the reactant. The average crystallite sizes of Ti5Si3 after activation of 1, 3, and 6 h were calculated 87, 55, and 48 nm, respectively. Higher milling energy in BPR 15:1, led to the full reaction and formation of nanostructured Ti5Si3 in milling media by mechanical alloying method, even after 1 h. The crystallite sizes of Ti5Si3 after milling of powders from 1, 3, and 6 h, were calculated 70, 26, and 14 nm, respectively. For the SHS process Ti and Si were mixed in the methanol. The combustion reactions were carried out in the tubular furnace and reactor. SEM results showed that Products were formed via MASHS process have more uniformity of microstructure compared to those synthesized via SHS process.

Study of seamless tube extrusion of SiCp-reinforced AZ61 magnesium alloy composites

This study involves the investigation of the mechanical properties of the extruded tube products with reinforced silicon carbide particulates (SiCp). Finite element analyses are firstly conducted to analyze the plastic flow of the magnesium alloy AZ61 within the die and to investigate the effects of initial billet temperatures on the extrusion loads and final product temperatures. AZ61/SiCp composite ingots reinforced with different weight fractions of SiCp are fabricated by a melt stirring technique. A specially designed die set is used in the extrusion experiments to obtain tubes with uniform thickness distribution in the circumferential direction. The extruded tubes are also heat treated to obtain even better mechanical properties. Finally, tensile tests, Vickers microhardness, tests and microstructure observation are performed on the billets and extruded tubes of AZ61 monolithic alloys and AZ61/SiCp composites. A much smaller grain size and higher tensile strength and hardness are achieved for the extruded AZ61/SiCp composite tubes.

Optimization of Intensification of Freeze-Drying Rate of Banana: Combined Applications of IR Radiation and Cryogenic Freezing

A programmed experimental study on infrared (IR) aided freeze-drying of cryogenically (LN2) frozen heat sensitive material viz. banana (Musa acuminata) rendered faster moisture separation rate compared to the conventionally frozen samples. Response surface methodology (RSM) could determine the simultaneous optimal freeze-drying conditions of 59.78°C IR temperature, 10 mm sample thickness, and 5 h drying time corresponding to the minimum moisture content of 4.11%, lowest final product temperature of 22.799°C, and maximum rehydration ratio of 1.72. Color difference, shrinkage, microstructure, pH, wettability, polysaccharide, and mineral contents of the cryogenically frozen freeze-dried banana at the optimal conditions have been determined coupled with Fourier Transform Infrared Spectroscopy (FTIR) and Carbon Hydrogen Nitrogen Sulfur (CHNS) analyses. Freeze-drying kinetics at optimal conditions have been evaluated and compared with literature published models and the “Handerson and Pabis” model was found to characterize the present case most closely among all drying models. A novel method for intensification of moisture separation rate leading to freeze-dried banana with high quality could thus be explored.

Optimal control and CFD modeling for heat flux estimation of a baking process

An optimal control method was combined with commercial CFD software for the optimization of heat flux during a baking process. The objective function was defined in terms of the transient heat flux, the temperature and the humidity of the baking product. The optimal control was achieved by the conjugate gradient method. The minimum energy consumption for a desired final baking product temperature and humidity was estimated. This study confirmed the relationship between the heat flux and baking product quality attributes and showed that optimal control models represent reliable tools to support decision making for complex processes such as baking. The proposed optimal control approach is general and could be easily extended to other processes.

Infrared-Assisted Freeze Drying of Tiger Prawn: Parameter Optimization and Quality Assessment

This article presents an extensive experimental study coupled with statistical analysis on infrared (IR)-assisted freeze drying of tiger prawn (Penaeus monodon) in cuboidal geometry. The work aims to estimate quality attributes of freeze-dried prawn in terms of final product temperature (below protein denaturation temperature), rehydration ratio, and final moisture content as a function of process parameters, viz. IR temperature (55–65°C), distance between sample and IR heater (30–60 mm), sample thickness (10–25 mm) and freeze-drying time (5.5–6.5 h). Response surface methodology (RSM) has been employed using a three-parameter, three-level face-centered central composite design (FCCD) to develop multivariate regression models in order to evaluate the influence of process parameters on the quality of the freeze-dried prawn. Optimal drying conditions of 10-mm sample thickness, 60-mm sample distance from the IR heater, 65°C IR temperature, and freeze-drying time of 6.37 h have been established. Separate validation experiments at the derived optimal conditions ascertained the predictive ability of the developed model equations. The outcome of this study would contribute to the development of technical capabilities for the design of freeze dryers applicable to such high-valued foodstuffs.

Simulation and experimental validation of simultaneous heat and mass transfer for cooking process of Mortadella Bologna PGI

SummaryIn this study, Protected Geographical Indication (PGI) Mortadella Bologna cooking process was investigated for heat and mass transfer. Apparent mass and heat transfer coefficient functions as well as apparent thermal diffusivity and mass diffusion coefficients were experimentally estimated. These thermo‐physical properties were used to develop a mathematical model for the simulation of simultaneous heat and mass transfer during Mortadella Bologna PGI cooking. The developed method was successfully validated for both heat and mass transfer by means of experimental cooking tests: maximum errors of about 3.5% and 4% were found for final product temperature and cooking time experimentally obtained respectively. Simulated weight loss values were also found not to differ significantly from those experimentally obtained. In addition, the developed model was successfully validated during a Mortadella cooking process carried out in an industrial plant proposing itself as a predictive tool to forecast and optimise cooking time and weight loss of this type of meat product. The proposed approach may be also used to design air cooking processes of other food products.

Modeling the effect of cooling system on the shrinkage and temperature of the polymer by injection molding

Injection molding is one of the most exploited industrial processes in the production of plastic parts. Shrinkage behavior of a molded plastic part plays an important role in determining final dimensions of the part. In this paper, the effect of the cooling system on the shrinkage rate of a polystyrene product during injection molding is carried out. A compressible fluid model for the physical system is presented. A finite volume numerical solution is used for the solution of the physical model. A validation of the numerical model in case of square cavity filled with polymer material is presented. The compressibility behavior of polymer material observed by the pressure, volume, and temperature for the state equation (P–v–T equation) is represented by Tait's equation. A Cross type rheological model depending on the temperature and pressure is assumed for the polymer material. The studied configurations consist of a mold having T-shaped plastic part and four cooling channels. Different cooling channels' positions are assumed and the effect of their positions on the cooling process is studied. The results indicate a good agreement between the numerical solution and those of the literatures. They also, show that the position of the cooling channels has a great effect on final product temperature and the shrinkage rate distribution throughout the product.

Impingement Cooking of Meat Products: Effect of Variability on Final Temperature

Heat transfer coefficient (HTC) for chicken fillets and beef burgers were determined at a number of product-to-tube distances in an impingement air unit. The coefficient varied from &lt; 100 W/m2 K to over 200 W/m2 K depending on the input parameter settings. The level of variation in the coefficient between adjacent product items in the oven has been quantified as ±20 W/m 2 K. Models of sheat transfer for both food products have been developed. Parameter of the models indicated that depending on the product, either dimensional variation in the product or dispersion in the HTC between products can make the dominant contribution to dispersion in final product temperature.

Modelling and optimization of seeded batch crystallizers

The existing model identification methods for estimating nucleation and crystal growth kinetic parameters are generally based upon simplified population balance models, such as moment equations, which contain insufficient information on the crystal size distribution (CSD). This paper deals with model identification and optimization of batch-seeded crystallizers. The final product CSD, temperature profile and concentration profile are used for identification. The reliability and precision of estimates are analyzed. Optimal temperature profile is determined such that an objective function pertinent to the final product qualities is minimized. The optimization algorithm finds the minimum of an objective function with respect to a parameter vector temperature input, subject to the mass balance and energy balance dynamics as well as the population balance equation (PBE). Simulation results for different objective functions are given to show the effectiveness of the proposed method. Compared with linear cooling profile, the optimal cooling profile is able to reduce the volumes of fines by 53.2% to improve product quality.

Evaluation of a rendered poultry mortality-soybean meal product as a supplemental protein source for pig diets.

Dehydrated/rendered broiler mortality-soybean meal products (DPS) were evaluated in two trials as high-protein feedstuffs for pig diets. Broiler mortalities, collected and frozen on-farm and transported to a central facility, were minced, blended with soybean meal, and dried with a final product temperature of 120 to 130 degrees C. The final DPS products used contained approximately 30 and 45% (DM basis) dried broiler mortality for the first and second trials, respectively (DPS1 and DPS2). The first trial involved 50 young, growing pigs (9 to 26 kg) and the second, 72 growing and finishing pigs (27 to 111 kg). The trials compared corn-based diets containing either soybean meal (SBM; 48%) or DPS products as the supplemental protein source. The DPS products averaged 50% CP and 2.9% total lysine; crude fat content of DPS used in the first trial was 8%, and for the second, 14.6% (as-fed basis). The ADG of pigs fed the DPS diets in either trial was similar to that of pigs fed the SBM control diets. In the second trial, pigs fed DPS2 had an overall average G:F ratio that was 9% better (P < 0.01) than that of pigs fed the SBM control diets. Carcass characteristics and pork quality from pigs of the growing-finishing trial were not affected by dietary treatment. Subjective carcass fat firmness scores indicated slightly softer fat (P < 0.05) from pigs fed DPS2. The mincing, blending with SBM, and dehydration of frozen stored on-farm broiler mortalities produced a safe and nutritious protein feedstuff for pigs, while also offering a viable disposal option.

Prediction of cooling time in injection molding by means of a simplified semianalytical equation

AbstractA simplified semianalytical equation, used successfully in food freezing/chilling time prediction, is proposed as a potential simple alternative for cooling time prediction in injection molding of polymer parts, amorphous or semicrystalline. This equation is based on a convective boundary condition for the mold‐part interface and requires information on the thermal contact resistance (TCR) or thermal contact conductance (TCC) at this interface, as well as information on the initial and final product temperatures, the mold surface temperature, and the thermal properties of the part. Eighty‐five data points for four polymers, Polystyrene (PS), Polycarbonate (PC), Polypropylene (PP), and Polyethylene (PE) were generated with C‐MOLD™, a commercial injection molding design software, and the performance of the proposed equation was tested. The % mean error and its standard deviation (SD) in cooling time prediction were, respectively, −11.61 and 2.27 for PS, −6.04 and 2.13 for PC, −7.27 and 6.55 for PP, and −8.88 and 2.93 for PE. It was also shown that the accuracy of the proposed equation is not affected significantly by the exact knowledge of the TCC, provided that the latter is not smaller than 1000–2000 W m−2 K−1. Since in this comparison all necessary temperatures were obtained from C‐MOLD™, methods of using the proposed equation independently were tested. The use of the inlet melt temperature as the initial product temperature increased the % mean error by mostly 1.5% while its SD remained practically the same. By incorporating a literature based heat balance method in the proposed equation, it was possible to use it as a stand‐alone predictor of polymer cooling time. The % mean error and its SD calculated this way were, respectively, −9.44 and 0.97 for PS, −9.44 and 0.83 for PC, −14.22 and 5 for PP, and −20.12 and 1.38 for PE. The proposed equation, at least in a preliminary stage, can be used successfully to predict the cooling time of the selected semicrystalline or amorphous polymers with the accuracy being higher for amorphous polymers. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 188–208, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10048

Heat Transfer Properties, Moisture Loss, Product Yield, and Soluble Proteins in Chicken Breast Patties During Air Convection Cooking

Chicken breast patties were processed in an air convection oven at air temperatures of 149 to 218 C, air velocities of 7.1 to 12.7 m3/min, and air relative humidities of 40 to 95%. The air humidity was controlled via introducing steam into the oven. The patties were processed to a final center temperature of 50 to 80 C. Heat flux, heat transfer coefficient, moisture loss in the cooked chicken patties, the product yield, and the changes of soluble proteins in the product were evaluated for the cooking system. During cooking, heat flux varied with the processing time. Heat flux increased with increasing air humidity. The effective heat transfer coefficient was obtained for different cooking conditions. Air humidity in the oven affected the heat transfer coefficient. The moisture loss in the cooked products increased with increasing the final product temperature and the oven air temperature. The soluble proteins in the cooked patties decreased with increasing the final product temperature. Increasing humidity increased heat transfer coefficient and therefore reduced cooking time. Reducing oven temperature, reducing internal temperature, and increasing air humidity increased the product yield. Soluble proteins might be used as an indicator for the degree of cooking. The results from this study are important for evaluating commercial thermal processes and improving product yields.

Moisture, Oil and Energy Transport During Deep-Fat Frying of Food Materials

A multiphase porous media model has been developed to predict the moisture migration, oil uptake and energy transport in a food material such as a semi-dry potato during deep-fat frying. The model predictions are validated using experimental data from the literature. Spatial moisture profiles show two distinctive regions (dry or crust region near the surface and wet region in most of the core) with a sharp interface which can be referred to as the evaporation front. Spatial temperature profiles show two distinctive regions—higher but constant temperature gradient region near the surface, and lower temperature gradient region in the core. In the crust region, vapour diffusional flux is comparable with vapour convective flux. In the more moist core region, capillary flux of liquid water is comparable to the convective flux of liquid water. Therefore, all three modes of transport—diffusional, capillarity, and pressure driven (Darcy) flow are found to be important. Sensitivity of the final product moisture and temperature to changes in oil temperature, initial moisture content of the sample, thickness of the sample, and the surface heat and mass transfer coefficients are discussed.

Cholesterol Content of Restructured Pork/Soy Hull Mixture

ABSTRACTThe effect of convective heat processing was studied on cholesterol and its oxides in a restructured pork/soy hull model system. Products were analyzed from 30 different time‐temperature conditions of processing. Following lipid extraction, GC‐MS was used for analysis of cholesterol and its oxides. No cholesterol oxides were found at 2 ppm in the product with any of the 30 time‐temperature profiles, ranging from 19 ‐89.6 min of heat processing, and 9–97°C final product temperatures. Cholesterol in heat‐processed samples ranged from 45.43–66.47 mg/l00g. Positive correlations were found between final temperatures and fat and cholesterol content.

Development of a successful spray-dried egg white-based experimental diet for dogs: Effect of heat treatment on diet utilization

The effect of processing spray-dried egg white (SDEW) was evaluated in two experiments to determine the efficacy of SDEW for use in a semi-purified diet fed to dogs. In previous studies feeding SDEW to growing dogs resulted in poor growth and diarrhea. Therefore to evaluate the possible beneficial effects of heat treating SDEW, four different processing methods were examined: 1) untreated SDEW, 2) extruded SDEW (final product temperature = 105°C), 3) extruded SDEW (final product temperature = 120°C), 4) autoclaved SDEW. Processed SDEW was added to the semi-purified basal diet at 20% of each treatment as the sole source of protein. Diets were fed to ten-weekold Pointer dogs for 14 days which included a 7-day adaptation and 7-day fecal collection period. Dogs fed the untreated SDEW lost weight, while those fed any of the heat-treated SDEWs gained weight. Autoclaved SDEW was more digestible (P<0.05) than untreated or extruded SDEW, although all diets had digestibilities greater than 83%. A protein efficiency ratio (PER) assay was conducted using 8-day-old male chicks to assess protein quality of SDEW. PER values were slightly higher for untreated and autoclaved SDEW than either of the extruded products. Thus, it can be concluded that the weight loss resulting from consumption of untreated SDEW can be prevented by each form of heat treatment evaluated. While autoclaved SDEW had slightly higher digestibility and PER values and lower trypsininhibitor activity than the extruded SDEW, the utilization of the extruded products was still considered adequate. The enhanced utilization of the heat-treated products may have been due to destruction of trypsin-inhibitor during heat processing.

Microwave Oven Solids Determination of High Oil Foods

Mustard, mayonnaise and salad dressing were dried in a microwave oven as a rapid method of determining solids content. Power setting, drying time and types of oil absorbent padding were varied to determine the most accurate methodology. Sample temperature was measured immediately after drying. The error in dry solids content compared to the standard convection oven procedure was directly related to the final product temperature. Procedures are outlined for determining the solids content of these food materials by microwave drying.

The synthesis of multiple-effect evaporator systems using minimum utility insights—II. liquid flowpattern selection

The concept of a “heat shunt” provides the insight needed to predict the extra utility consumption that is caused by the liquid flowpattern of a multieffect evaporator system. When no liquid bypassing of the effects is permitted, the liquid flowpattern requiring the minimum use of utilities follows one of two possible shortest “temperature paths” through the process, i.e. either a “down first” path that starts at the feed temperature, proceeds all the way to the lowest effect temperature, reverses, proceeds to the highest effect temperature and finally returns to the final concentrated product temperature; or an “up first” path that proceeds first to the highest effect temperature, etc. A simple calculation permits one to choose between these two paths. The liquid enters each effect the first time the selected path passes the effect temperature. When liquid bypassing is allowed, the paper shows that parallel feed to the effects is best. Major assumptions are constant boiling point elevation and negligible heat of mixing. An example illustrates all ideas.