Superheated steam drying and processing?

Transcription

1 Superheated steam drying and processing? Stefan Cenkowski Department of Biosystems Engineering University of Manitoba Nov. 17, 2014

2 Overview History of SS drying What is superheated steam drying? How does it work? What are the (dis)advantages? Where are the potential opportunities? Our experimental results

3 History Hausbrand (1912) Heat transfer textbook Considered drying with steam alone and wide application attainable once advantages known Use of SS kilns for lumber (on the West Coast of US 1908) WWI produced a high velocity, low superheat kiln Inefficiencies and corrosion caused decline in use WWII saw kilns with SS or air-steam mixtures, with 2 companies supplying kilns Brown coal (low grade, high mc) drying Introduction of the Fleissner process (1920 s) In addition to lumber and coal, there was foundry sand drying, and resin production Yoshida and Hyodo (Osaka, Japan) looked at synthetic fibers and potato slices

4 Industrial Applications Greatest number of units for lumber Brunner/Hildebrand and WWT account for over 250 units Outside of the lumber industry suppliers are : GEA/Barr-Rosin drying pulpy materials BMA AG to dry sugar beet pulp W. Kunz drytec AG Swiss Combi Ecodry dryers (dry sludge, sawdust, wood chips, and other products on a rotary drum dryer with recirculating SS) Maschinenfabrik Gustav Eirich GmnH & Co KG for processing sludge, brake linings, pigments, wash powder additives, and ferrites Moenus Artos Textilmaschinen GmbH (Textile dryer - impingement Keith Engineering New Zealand (Pinches Industries of Melbourn) rendering industry, animal b-products, blood, wood chips, and sewage sludge Sharp Coroperation (Japan) Healsio SS oven to cook and roast food

5 Drying Systems: Batch Fixed Bed SS Dryer On the industrial scale: Lumber On the laboratory scale: Spent grains Sugar-beet pulp alfalfa Potatoes, flour Molasses, clay Wheat, corn, oilseed Instant foods, Asian Meat (ham, chicken) Shrimp, fishmeal Silkworm cocoons Sterilization - enhanced microbial destruction (spores), product sterilization (hemp seed) Vegetables (carrot, cauliflower, asparagus, leek) Citrus pulp/peel, apple pomace. Herbs (oregano, parsley, green tea) Spices (paprika, onion powder)

6 Hot air vs SS - Advantages Summary Closed-loop system reduces the energy Evaporated moisture can be recovered High heat transfer high drying rate, reduction in the equipment size and capital cost No oxidation can eliminate fire and explosion hazards Elimination of environmental pollution Valuable volatile organic compounds could be recovered

7 Main Limitations: High temperature for temperature sensitive products Browning reactions, Discolouration, Starch gelatinization, Enzyme destruction, Protein denaturation Drying systems are more complex but Simultaneous drying and cooking Change in textural properties could be beneficial (e.g. baking potatoes, instant pastas and noodles) Microbial destruction What is Superheated Steam? Steam that has additional sensible heat added so that its temp. is above the saturation temp. at a given pressure.

8 How does it work? Conventional air drying depends on: psychrometric equilibrium 30 o C SS drying relies on: saturated steam equilibrium superheat of steam P=P a +P v ΔQ ΔS=---- T s T o C T dp t sat 50 C Super- Heated Steam Wet steam s

9 Superheated Steam Processing System condensate condenser steam out processing chamber water steam generator superheated sup steam superheater Sample tray

10 Three distinct periods in SS drying Preheating and condensation period Constant drying rate period, and The falling rate period. condensation SS temp Product temp(t) Temp mc mc(t) Drying time

11 SS Research U of M Sugar-beet pulp Drying kinetics

12 Temp Temp Temp Temp Temp Temp SS Research at U of M Potatoes Moisture Moisture Drying kinetics

13 SS Research at U of M a w for brewers grain and distillers grain ` a w for sugar beet pulp SS vs hot air

14 Drying Asian Noodles C SS temperature 1.4 Moisture ratio, MR Measured (0.5 m/s) Measured (1.0 m/s) Measured (1.5 m/s) Predicted Drying time (s)

15 SS Research at U of M Decontamination of oat groats Bacillus stearothermophilus Spore-forming microorganism Spores are heat resistant and used to monitor sterilization of moist heat D-value Table of bacillus 5. D-values stearothermophilus of Bacillus stearothermophilus treated with SS treated in superheated steam Temperature (ºC) D-value (min) for 10 3 (cfu g -1 ) inoculum level D-value (min) for 10 6 (cfu g -1 ) inoculum level [a]

16 Developing Manitoba s Ethanol Industry Distillers and Brewers spent grain Modeled drying process in SS Results favorable with benefits of reduced fire risks, and better aroma with acetic acid removal Pentosan, β-glucan, and protein levels not affected with increase in drying time and temperature, Starch content low due to partial starch gelatinization and/or formation of amylose-lipid complexes

17 Steam Steam Steam Thermal/Steam

18 Densification and drying of DSG Compacted biomass Superheated steam dryer Disintegra*on of biomass compacts Crumbled compacts and fines may interrupt the drying system

19 Raw Materials and Ini/al Sample Prepara/on S*llage (Corn and wheat ra*o 9:1) Thin s*llage Centrifuga*on Wet dis*ller s spent grain (WDG) MC: 69.0% wb d(0.9)= µm Solubles (CDS) MC: 79.4% wb d(0.9)= Grinding d(0.9)= µm d(0.9)= µm

20 Effect of SS at 220 o C on moisture content of wheat straw (i) boiled at 119C for 15 min followed by SS treatment and (ii) processed in SS alone. Moisture content, % db BW SS Time, s

21 Drying Characteristics of WDG Compacts during SS Drying

22 SS processing Before After Percentage change Percent decrease in density Percent increase in volume Oven drying temp ü Approximately 78 to 130% percentage increase in volume was observed while drying the compacts in SS.

23 Hardness and Asymptotic Modulus Hardness (N) Solubles (%) Solubles (%)

24 Hardness (N) Before processing 5s SS processing Moisture content (% wb) Asymptotic modulus (MPa) Moisture content (% wb)

25 Conclusions SSD technology can provide: Product benefits increased drying rate specific product quality Pelleting moist product before drying Developing surface area Condensation period affecting hardness Volume increase Environmental advantages

26 Processing with superheated steam Dave Barchyn & Stefan Cenkowski University of Manitoba Department of Biosystems Engineering November 17th, 2014

27 Pre- treatment of lignocellulose Disrup*on of lignin structures / delignifica*on Hydrolysis of 5- and 6- carbon sugars Minimize genera*on of inhibitors, destruc*on of sugars Maximize poten/al conversion to end product

28 2- Phase pre- treatment Treatment in pressurized hot water Treatment with atmospheric SS at 220 C 70% 60% Glucose yield (%) 80% 70% With xylose recovery Without xylose recovery % Conversion 50% 40% 30% 20% Xylose yield (%) % xylose conversion 60% 50% 40% 30% 20% 10% 10% 0% Raw 15HW 15HW2SS 15HW5SS 15HW10SS Treatment 0% Raw 15HW 15HW2SS 15HW5SS 15HW10SS Treatment

29 Treatment Change in moisture content (kg/kg) Corresponding energy demand* (kj/kg) Total energy demand (kj/kg) 15 min. HW min. HW + 2 min. SS 15 min. HW + 5 min. SS 15 min. HW +10 min. SS * Associated with SS phase of treatment

30 Energy Balance Steam explosion Process energy Energy in ethanol Superheated steam (no xylose recovery) Superheated steam (xylose recovery) Process energy Energy in ethanol Process energy Energy in ethanol

31 Cost of produc*on

32 Process efficiency MESP ($/L) $0.77 $0.76 $0.75 MESP MESP w/ xylose recovery $0.74 $ Glucose conversion efficiency (%)

33 Conclusions Processing with SS can provide energy savings for the pre- treatment of lignocellulosic substrates Subject to op*miza*on of the process to increase the efficiency of glucose and xylose conversion