Superheated steam drying and processing?

Stefan Cenkowski

Department of Biosystems Engineering University of Manitoba

Nov. 17, 2014

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

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

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

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

–  Vegetables (carrot, cauliflower, asparagus, leek)

–  Citrus pulp/peel, apple pomace.

–  Herbs (oregano, parsley, green tea)

–  Spices (paprika, onion powder)

§ Sterilization - enhanced microbial destruction (spores), product sterilization (hemp seed)

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

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.

How does it work? •  SS drying relies on:

–  saturated steam equilibrium –  superheat of steam

P=Pa+Pv

ΔS=---- ΔQ T

30oC

s

Tdp

T1

100oC tsat

Wet steam

Super- Heated Steam

1

2

1

2 50°C

s

•  Conventional air drying depends on: –  psychrometric equilibrium

Superheated Steam Processing System

condensate steam out

water

processing chamber

condenser

steam generator superheater

sup

supe

rhea

ted

st

eam

Sample tray

Three distinct periods in SS drying •  Preheating and condensation period •  Constant drying rate period, and •  The falling rate period.

mc

Temp

mc(t)

Drying time

Product temp(t)

SS temp condensation

SS Research U of M

Sugar-beet pulp

Drying kinetics

SS Research at U of M

Temp

Temp

Temp

Temp

Temp Temp

Moisture Moisture

Drying kinetics

Potatoes

` SS Research at U of M

aw for brewers’ grain and distillers grain

aw for sugar beet pulp SS vs hot air

Drying Asian Noodles

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 100 200 300 400 500 600 700 800 900 1000

Drying time (s)

Moi

stur

e ra

tio, M

R

Measured (0.5 m/s)

Measured (1.0 m/s)

Measured (1.5 m/s)

Predicted

120°C SS temperature

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

Table 5. D-values of Bacillus stearothermophilus treated in superheated steam

Temperature (ºC)

D-value (min) for 103

(cfu•g-1) inoculum levelD-value (min) for 106

(cfu•g-1) inoculum level[a]

105 23.5 -130 65.9 -145 63.0 29.0160 9.3 2.1175 2.2 1.5

[a] D-values at 105 and 130ºC could not be calculated even after 80 min of processing

D-value of bacillus stearothermophilus treated with SS

•  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

Developing Manitoba’s Ethanol Industry

Steam

Steam

Steam Thermal/Steam

Disintegra*on  of  biomass  compacts    

Crumbled  compacts  and  fines  may  

interrupt  the  drying  system  

Superheated  steam  dryer  

Compacted  biomass  

Densification and drying of DSG

S*llage  (Corn  and  wheat  

ra*o  9:1)  

Thin  s*llage  

Wet  dis*ller’s  spent  grain  (WDG)    MC:  69.0%  wb  

d(0.9)=  1283.6  µm    

d(0.9)=  1069.3  µm  

Raw  Materials  and  Ini/al  Sample  Prepara/on    

Grinding  

Centrifuga*on  Solubles  (CDS)  MC:  79.4%  wb  d(0.9)=  563.9  

d(0.9)=  812.8  µm  

Effect of SS at 220oC on moisture content of wheat straw (i) boiled at 119C for 15 min followed by SS treatment and (ii) processed in SS alone.

Time, s

Moi

stur

e co

nten

t, %

db BW

SS

Drying Characteristics of WDG Compacts during SS Drying

ü  Approximately 78 to 130% percentage increase in volume was observed while drying the compacts in SS.

SS processing

Before

Percent increase in volume

Percent decrease in density

Oven drying temp

Per

cent

age

chan

ge

After

Solubles (%)

Solubles (%) H

ardn

ess

(N)

Hardness and Asymptotic Modulus

Before processing

5s SS processing

Har

dnes

s (N

)

Moisture content (% wb)

Asy

mpt

otic

mod

ulus

(MP

a)

Moisture content (% wb)

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

Processing  with  superheated  steam  

Dave  Barchyn  &  Stefan  Cenkowski  University  of  Manitoba  Department  of  Biosystems  Engineering  November  17th,  2014  

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    

2-­‐Phase  pre-­‐treatment  

•  Treatment  in  pressurized  hot  water  •  Treatment  with  atmospheric  SS  at  220˚C  

0%  

10%  

20%  

30%  

40%  

50%  

60%  

70%  

Raw   15HW   15HW2SS   15HW5SS   15HW10SS  

%  Con

version  

Treatment  

Glucose  yield  (%)  

Xylose  yield  (%)  

0%  

10%  

20%  

30%  

40%  

50%  

60%  

70%  

80%  

Raw   15HW   15HW2SS   15HW5SS   15HW10SS  

%  xylose  conversion

 

Treatment  

With  xylose  recovery  Without  xylose  recovery  

Treatment  Change  in  

moisture  content  (kg/kg)  

Corresponding  energy  demand*  

(kJ/kg)  

Total  energy  demand  (kJ/kg)  

15  min.  HW   0   0   930  

15  min.  HW    +  2  min.  SS   0.368   1068   1998  

15  min.  HW  +  5  min.  SS   0.611   1772   2702  

15  min.  HW  +10  min.  SS   0.809   2348   3278  

* Associated with SS phase of treatment

Energy  Balance  Steam  explosion  

Process  energy  

Energy  in  ethanol  

Superheated  steam  (no  xylose  recovery)  

Process  energy  

Energy  in  ethanol  

Superheated  steam  (xylose  recovery)  

Process  energy  

Energy  in  ethanol  

Cost  of  produc*on  

Process  efficiency  

$0.73  

$0.74  

$0.75  

$0.76  

$0.77  

40   45   50   55   60   65   70   75   80   85  

MESP  ($/L)  

Glucose  conversion  efficiency  (%)  

MESP  

MESP  w/  xylose  recovery  

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