Pure triglyceride as a colorless liquid, however, a common form of fat various colors, because of containing various pigments caused. The presence of the pigment affect not only the appearance of grease, and, even on the flavor on human health has great. Therefore, have to be removed. The main role of decolorization process: removal of pigment; the removal of trace metals; remove residual soap, gum and some odor substances; eliminate oxidation products, as well as vitamin E, sterols, pigments and other lipid oxidation products.
Common types of adsorbents and features:
Common adsorbents have activated clay, activated carbon, zeolite, diatomaceous earth.
Activated Clay features:
Free water(105 ℃) ≤13% (4-7% of bound water strongest decolorization);
Residual acid, phosphorus KOH consumed less 3.5mg / g;
pH 5.2 (pH <0.2% H₂SO₄);
Hold oil yield of 30%;
The average particle size of 35μm (through200 mesh / in more of 95%);
Depending on the density of 560kg / m³;
The specific surface area of about 300 ㎡ / g(temperature decolorization 180-240㎡ / g; low temperature decolorization of 250-300㎡ / g).
Continuous decolorization process parameters:
Continuous decolorization process is decolorized oil degassing, and clay mixed directly into the pipeline pump decolorization system, you can complete a row preheating, heating, discoloration and all decolorization process cooling.
Mixing the oil in the pipe flow rate 0.1-0.2 m / s;
Bleaching temperature 100-110 ℃;
Decolorization time 15-20 min (no more than35min);
Clay added amount of 0.3% -1.5% (up to 2%rice bran oil, plus charcoal 0.02%);
Degassing the oil temperature above 80 ℃;
Vacuum degree 94.7-100.7 kPa (ie 710-775 mmHg).
Factors affecting the adsorption decolorization:
1, the amount of clay: Generally speaking, the increase of amount of adsorbent, is conducive to improve the decolorization effect. However, with the increase of the content of neutral oil loss, increased the adsorption. Production Rapeseed Oil when China clay dosage is generally 1%-2%.
2, Operating pressure: general vacuum requirements of 93.3-96kPa (700-720mmHg).
3, temperature and time of treatment: in the negative pressure (6.7kPa or 50mmHg) conditions, the decolorization of soybean oil with activated clay, the highest temperature is only 82 ℃; decolorization time of 20min; and the highest operating temperature is required at atmospheric pressure and 104 ℃.