Intermittent type adsorbent decoloring process
In the intermittent type decoloring process of edible oil, oil & adsorbent mixing, heating, reacting, cooling and filtering are batch processed in edible oil bleaching pots. Intermittent type adsorbent decoloring process is suitable for small and medium oil refining factory, and the main processing equipment is bleaching tank. The bleaching tank is a closed cylindrical container with a dish cover and a conical bottom. Edible oil bleaching machine is equipped with stirring device and heating coil, and the power motor is fixed on the top cover of it. In addition, bleaching machine has decolorizer inlet pipe, vacuum pump, inlet-outlet-oil-tube, cooling water pipe and steam pipe.
Continuous type adsorbent decoloring process
In the continuous type oil decoloring process, the steps of adsorbent’s quantitative supply, oil & adsorbent mixed adsorption, and oil & pigments separation, are in the process of continuous operation. The main processing equipment of continuous type oil decolorization is continuous decolorizer (decolorization tower), leaf filter and vacuum system equipment.
- Decolorization tower is a three-layer oil and adsorbent stirring decolorization device with overflow pipe which can connect with three layers (to control the mixing time of adsorbent and oil). Each of the layers is equipped with a stirring blade, and the second layer of the tower is equipped with an exhaust passage for venting air and the bottom layer is also equipped with a liquid level control device and sensor. In addition, the bleaching tower has a vacuum inlet to prevent oil oxidation and a level glass for machine observation and easy maintenance.
- Leaf filter is mainly composed of the tank body, filter leaf group, pneumatic vibrator, oil inlet tube & oil outlet pipe and slag discharge port.
- Vacuum system equipment can be installed at bleaching machine which effectively prevents the contact between oil and air. The quality of the oil is guaranteed.
The phenomenon that the automatic change of material in the phase interface is called adsorption. An adsorbent is a solid substance that adsorbs a substance on the surface to reduce its surface energy, and its adsorption capacity is of practical value. There are many adsorbents available for production and application. In oil refining process, the commonly used adsorbents are bleaching earth, activated clay, and activated carbon:
Natural bleaching earth has a certain activity, and its scientific name is bentonite. Its structure is microporous crystals or amorphous and it has a larger specific surface area than other clay. However, its decolorization coefficient is low(which means that when the same batch of oil is decoloring, the ratio of oil column is observed to achieve the same color), and the oil absorption rate is higher, so the bleaching earth is gradually replaced by activated clay.
Activated clay is a highly active adsorbent which is processed by bentonite as raw material and is widely used in the bleaching of the oil industry. Activated clay has a strong adsorption capacity on chlorophyll and other gelatinous impurities, especially basic group and polar group. After activated clay bleaching, the residual soil smell in the oil can be removed in the deodorization process.
Activated carbon is made from carbonized sawdust, bagasse, chaff and hard shell, and then by chemical or physical activation. Activated carbon has loose pores, large specific surface area, high decolorization coefficient, and hydrophobicity. It can adsorb macromolecule substances, especially blue and green pigments. It also can remove trace minerals. In addition, it has a strong adsorption capacity for the gas, polycyclic aromatic hydrocarbons and pesticide residues. But because of activated carbon’s high cost and high oil absorption, it is often used with bleaching earth or activated clay in oil decolorization. The mixing ratio is usually 1: 10~20. Mixed use can obviously improve the decolorization ability, and can remove the smell of drifting soil.