Passion for Progress

Transcription

1

2 Fluidized-bed drying with superheated steam Jochen Gaßmann, Mirko Löhn, Hartmut Hafemann BMA Braunschweigische Maschinenbauanstalt AG Braunschweig, Germany ifood 2013, Hannover Without verbal explanation the information on this document is incomplete

3 Steam drying has been proven in a number of practical applications takes place in a pressurized fluidized bed uses superheated steam instead of hot air for fluidisation and drying provides excess steam by evaporation of the product water should be integreated into the energy system of a factory is characterized by multiple use of primary energy reduces CO 2 emissions

4 Operating principle Main components (1) product feed system (3) fuidized bed (4) pruduct discharging system (6) rotary dust separator (8) vapour discharge (9) heat exchanger (10) fan

5 Integration into an energy system (pulp drying) Main processes (1) steam generation (2) power generation (3) pressurized fluidized-bed steam drying (4) utilization of the excess steam

6 Advantages The vapour produced during drying has a high energy content. This energy potential can be used for downstream processes. Because of the closed system emissions can be avoided. No air pollution by dust and odours. No loss of product. Oxygen-free steam atmosphere prevents oxidative reactions. Volatile substances can be removed and recovered by condensation. Optimum conditions for sterilisation prozesses.

7 New applications Necessary investigations Assessment of the properties of the wet product before steam drying Investigation of flow characteristics Investigation of drying kinetics Assessment of product properties after the steam drying process In order to carry out such studies appropriate test equipment is necessary.

8 Test unit fluidized-bed steam dryer Parameter batch-wise operating device batch size: 0,5 to 2 kg fluidized-bed: d = 200 mm fluid velocity: up to 8 m/s working pressure: up to 4,5 bar process temperature: up to 210 C

9 Technological principle test unit Main components 1 feeding lock system 2 dryer 3 fluidized bed with perforated plate 4 steam injection 5 discharge lock system 6 cyclone for dust separation 7 dust discharge 8 fan 9 heat exchanger

10 Drying kinetics Temperature profiles depend on the product characteristics 180 Temperatur [ C] Zeit [s] Wheat stillage Brewers grain Te m pe ratu r [ C ] 210 Dampfeinlass 200 Erweiterungsteil WS oben 190 WS unten Dampfeinlass Erweiterungsteil WS oben WS unten eff. Dampftemp Zeit [s]

11 Results of steam drying tests Dried materials of different structures and composition after drying (reference particle d=5mm) Wood chips 200 C, v=4 m/s, p=2 bar Corn stillage 200 C, v=3 m/s, p=4 bar Brewers grain 200 C, v=2,5 m/s, p=3 bar

12 Results of drying tests Conditioned wet material after drying 160 C 6 Min 1 bar 160 C 6 Min 2 bar 160 C 6 Min 3 bar 180 C 5 Min 1 bar 180 C 5 Min 2 bar Corn stillage 180 C 5 Min 3 bar 180 C 5 Min 4 bar 200 C 4 Min 3 bar 200 C 3 Min 4 bar 200 C 2 Min 4 bar Wheat stillage

13 Flow characteristics The flow test unit represents the elements of a real dryer Fluid: air, atmospheric pressure

14 Flow characteristics to investigate the flow behavior during fluidization to investigate the efficiency of dust separation via investigation to simulation

15 Summary The aim of the fluidized-bed steam drying technology is the multiple use of primary energy and the reduction of CO 2 emissions. New applications require the possibility to conduct experiments. Investigations according real process conditions are necessary. The pressurized steam dryer is an highly efficient multiple utilisation system if integrated in combined plants or in energy networks Temperatur [ C] Dampfeinlass Erweiterungsteil WS oben WS unten Zeit [s]

16 The installation of the pilot plant was co-financed by Deutsche Bundesstiftung Umwelt (DBU) as part of a research project (Ref.No.: /2)