Based on the difference of alkaline concentration and the oil temperature, alkali refining operation is divided into low temperature concentrated alkaline (initial temperature is 20-30 ℃; alkali concentration is 20-30 Be) and high temperature light alkaline (initial temperature is 75 ℃; alkali concentration is 10~16 Be). The former is widely used, and the latter is mainly suitable for crude oil with low acid value, light color and less impurity.
(1)Low temperature concentrated alkaline:
Adjust the oil temperature to 20-30 ℃, and then will add alkali of 20-30Be within 5-10 minutes and stir about 20~60 minutes under the condition of 60 rpm. Observe the form and separation of reacted soapstock grain and began to slowly heat up, about 1 ℃ higher per minute. When the temperature reaches to 60 ℃, stop stirring and make soapstock settlement. Usually need 6~8 hours and then released soapstock.
(2)High temperature light alkaline:
First ensure alkaline concentration as defined by the crude oil acid price (see table), and calculate amount of alkaline and water addition. When the acid value is less than 5, each unit acid value, water addition is 23 kg per ton; acid value is more than 5, no more than 12% wight oil, super alkali is only 0.002~0.005%. Crude oil acid price < 3 3-5 5-7 of 7-10 > 10, alkali concentration Be 11 12 14 16, during operating, first stir crude oil and then heat up to 70-75 ℃, adding dilute brine or phosphoric acid (concentration 85%, the dosage 0.1%); add alkali after appearing particles; continue to stir 40~50 minutes and heat up to 90-95 ℃; stop stirring when soapstock grain separate out obviously; keep 2~3 hours and then released soapstock.
