Integrierte Vermeidung und Verminderung der Umweltverschmutzung
Teilen Einbetten Melden
ePaper herunterladen

Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Integrierte Vermeidung und Verminderung der Umweltverschmutzung Integrierte Vermeidung und Verminderung der Umweltverschmutzung

bvt.umweltbundesamt.de
von bvt.umweltbundesamt.de Mehr von diesem Publisher
10.12.2012 Aufrufe

Chapter 2 2.2.12.2 Sugar cane Raw cane sugar is usually separated, purified and crystallised in the country of origin. The cane sugar, which is in a crudely refined state, undergoes final processing when transferred to the country of use. 2.2.12.3 Sugar refining Raw sugar is typically a minimum of 96 % sucrose. The impure crystals, with adhering molasses, are blended in a saturated sugar solution to soften the surface molasses film which can then be removed by centrifugation. The partly processed sugar is dissolved in reclaimed liquors, i.e. light waters from the refining process. Carbonation, which is treatment with milk of lime and carbon dioxide, then follows. This produces a precipitate which contains impurities such as pectins and proteins and removes suspended impurities such as waxes, gums and starches. The sugar syrup is filtered and decolourised using ion exchange resins and activated carbon to produce a fine liquor, which may be sold as a finished product or passed on for crystallisation. The fine liquor is concentrated by evaporation to produce a syrup of around 60 – 70 % solids, known as thick juice. The juice is filtered and transferred to vacuum pans. When the liquor is slightly supersaturated, the pan is seeded with fine icing sugar to initiate crystallisation. The mixture is centrifugally separated to extract crystalline sugar, which is dried, conditioned for packaging or bulk loaded. Each pan boiling yields around 50 % of the available sugar. The liquor separated during centrifugation, also called jet, is re-boiled for further extraction. Three boilings yield white sugar. A fourth boiling yields off white industrial sugar. Jet four, together with liquor from blending, goes to a recovery house for three further boilings to produce brown sugars which go back to the start of the refining process and are treated as raw sugar. Various intermediary products from jets one to four and the corresponding syrups from recovery and boiling are sold as the starting materials for syrups such as molasses and treacle. Molasses are sometimes used in animal feed, alcoholic fermentation and a number of non-food products. 2.2.13 Coffee Commercial coffees are grown in tropical and subtropical climates at altitudes of up to around 1800 metres. Coffees from different producing regions possess different characteristic flavours. The main processing steps in the manufacture of roasted coffee are blending, roasting, grinding and packing. Instant coffee is produced from a water extract of roasted ground coffee. Roasting coffee beans and the production of instant coffee are energy intensive processes. 2.2.13.1 Roasting coffee Green coffee is received and sorted to remove extraneous matter. Coffees from different varieties or sources are blended before or after roasting. Roasting is usually carried out by hot combustion gases in rotating cylinders. The final bean temperature is around 200 to 220 °C. A water or air quench terminates the roast. Most of any added water is evaporated from the heat of the beans. Fluidised bed systems may greatly reduce roasting times from around 8 to 15 minutes to 1 to 3 minutes. Finished coffee is transferred to storage bins. Any residual foreign bodies are removed before grinding, usually by air classification methods. Most coffees are ground in steel cutting rollers which are scored, once longitudinally and once across the circumference. Cracking rolls break the beans before they are fed into a further series of rollers. For fine grinds, the coffee may pass into further sets of rollers, being scored on each subsequent pair of rollers and becoming progressively finer as the coffee travels through the system. Roasted and ground coffee in Europe is typically vacuum packed in flexible pouches of plasticlaminated foil. 102 January 2006 RHC/EIPPCB/FDM_BREF_FINAL

2.2.13.2 Instant coffee Chapter 2 Instant coffee is subjected to similar processing, namely blending, roasting and grinding, although processing details such as particle size after grinding may differ. During extraction of coffee for the production of soluble coffee, water is the extracting solvent. The coarsely ground coffee is extracted in a battery of batch percolating columns. The process is operated semicontinuously with water in a countercurrent flow to the coffee, from the most extracted cell to the one just filled with fresh roast and ground coffee. The extract is recovered from the fresh or least-extracted cell. One consequence of using high temperatures is that the system must be kept under pressure, so, the individual cells and associated pipework has to be designed accordingly. Once a batch of solids has been extracted, the exhausted cell is separated from the train and the spent grounds are discharged. At the same time, a cell containing fresh roast and ground coffee is added to the train. The extraction yield is expressed as the amount of recovered water-soluble dry solid content of roasted coffee as a percentage of roasted coffee (dry weight). Yields of 40 to 56 % are obtainable. Some manufacturers vacuum-concentrate the extract. The extract is dried, typically by spray-drying or freeze drying. The powder may be agglomerated to improve solubility. The final product is then packed into containers. During the extraction of soluble solid matter from the roasted coffee, a large quantity of coffee grounds is produced in addition to the fluid coffee extract. These are utilised as fuel in special grate firing installations. The ground coffee is used, in balance with heating oil and natural gas, as a special fuel. The following paragraphs describe the manufacture of instant coffee in an example installation which produces 18000 tonnes of green coffee per year. A diagram of the process is shown in Figure 2.21. Figure 2.21: Instant coffee manufacturing The arriving green coffee is picked up by discharge hoppers and mechanically cleaned through sifting and air separation before it reaches the silos. The raw coffee is roasted to enable its characteristic aromas and flavours to be appreciated. Then, after the coffee beans are ground, hot water is added to produce an extract. The extract is clarified and concentrated. A portion leaves the company in its now liquid form. This portion is transported by a road tanker to other installations for further processing. RHC/EIPPCB/FDM_BREF_FINAL January 2006 103

2.2.13.2 Instant coffee<br />

Chapter 2<br />

Instant coffee is subjected to similar processing, namely blending, roasting and grinding,<br />

although processing details such as particle size after grinding may differ. During extraction of<br />

coffee for the production of soluble coffee, water is the extracting solvent. The coarsely gro<strong>und</strong><br />

coffee is extracted in a battery of batch percolating columns. The process is operated semicontinuously<br />

with water in a countercurrent flow to the coffee, from the most extracted cell to<br />

the one just filled with fresh roast and gro<strong>und</strong> coffee.<br />

The extract is recovered from the fresh or least-extracted cell. One consequence of using high<br />

temperatures is that the system must be kept <strong>und</strong>er pressure, so, the individual cells and<br />

associated pipework has to be designed accordingly. Once a batch of solids has been extracted,<br />

the exhausted cell is separated from the train and the spent gro<strong>und</strong>s are discharged. At the same<br />

time, a cell containing fresh roast and gro<strong>und</strong> coffee is added to the train. The extraction yield is<br />

expressed as the amount of recovered water-soluble dry solid content of roasted coffee as a<br />

percentage of roasted coffee (dry weight). Yields of 40 to 56 % are obtainable. Some<br />

manufacturers vacuum-concentrate the extract. The extract is dried, typically by spray-drying or<br />

freeze drying. The pow<strong>der</strong> may be agglomerated to improve solubility. The final product is then<br />

packed into containers.<br />

During the extraction of soluble solid matter from the roasted coffee, a large quantity of coffee<br />

gro<strong>und</strong>s is produced in addition to the fluid coffee extract. These are utilised as fuel in special<br />

grate firing installations. The gro<strong>und</strong> coffee is used, in balance with heating oil and natural gas,<br />

as a special fuel.<br />

The following paragraphs describe the manufacture of instant coffee in an example installation<br />

which produces 18000 tonnes of green coffee per year. A diagram of the process is shown in<br />

Figure 2.21.<br />

Figure 2.21: Instant coffee manufacturing<br />

The arriving green coffee is picked up by discharge hoppers and mechanically cleaned through<br />

sifting and air separation before it reaches the silos. The raw coffee is roasted to enable its<br />

characteristic aromas and flavours to be appreciated. Then, after the coffee beans are gro<strong>und</strong>,<br />

hot water is added to produce an extract. The extract is clarified and concentrated. A portion<br />

leaves the company in its now liquid form. This portion is transported by a road tanker to other<br />

installations for further processing.<br />

RHC/EIPPCB/FDM_BREF_FINAL January 2006 103

logo

Produkte

Ressourcen

Unternehmen

AGB
Datenschutzerklärung
Cookie-Richtlinien
Cookie-Einstellungen
Impressum
Change language
Made with love in Switzerland
© 2024 Yumpu.com all rights reserved

Hurra! Ihre Datei wurde hochgeladen und ist bereit für die Veröffentlichung.

Erfolgreich gespeichert!

Leider ist etwas schief gelaufen!