1. Improvement of refining process and equipment.
1) Acid refining and alkali refining.
1. Conventional acid refining and degumming.
Crude vegetable oil contains hydrated phospholipids and non-hydrated phospholipids. Different phospholipids have different hydration rates (see full text), and the phosphatidylcholine (PC) content of soybean oil is generally about 30%, and rapid hydration at high temperature can only remove phospholipids with faster hydration speed. The metal ion content of non-hydrated phospholipids is 4 times higher than that of hydrated phospholipids, and acids need to be added to convert non-hydrated phospholipids into hydrated phospholipids. The conventional acid refining process is to add acid to the crude oil to mix and degum, and then add alkali to mix and neutralize the separation.
The energy-saving and consumption-reducing measures taken by acid refining and degumming are as follows:
Heating the crude oil into the workshop with the cooling water coming out of the refined oil cooler can save 3 4kg t of steam.
In order to avoid crystallization of the acid pipeline, the phosphoric acid concentration was reduced from 85% to 75%, and the transmission pipeline was insulated.
The acid tank is placed on the top layer of the deodorization tower, and the acid is added accurately by self-flow to avoid the metering error caused by the wear or failure of the metering pump.
The acid addition amount was calculated according to the non-hydrated phospholipid content and impurity content of the incoming oil, and a small sample test was done to control the acid value (KOH) of the degummed oil after acid refining to increase by 015~0.35 mg g to rise by 02~0.5mg g, the amount of washing water was reduced from 8% 15% to 6% 13% of the quality of the desoaped oil.
The acid mixer is a powerful mixer, using two acid reaction tanks, the reaction time is 35min and 25min respectively, the acid reaction tanks are connected in series, and there is a bypass pipe.
2. Enzymatic degumming.
Enzymatic degumming refers to the degumming of enzyme preparations PLC and PLA added together or separately to crude oil. Enzymatic degumming can reduce the neutral oil content in the gum, and the process flow is as follows:
The main steps of enzymatic degumming:
The phosphorus content of crude oil is 350 1500mg kg, plus 005%~0.1% citric acid, mixed by a high shear mixer for 30min, citric acid plays a role in chelating CA and MG metal ions, releasing phospholipids, and the suitable reaction temperature is 70 75.
After adding acid, the pH of the oil decreases, and the oil temperature drops to 55, NaOH is added to increase the pH to the appropriate range of enzyme activity, and the enzyme preparation is added and the reaction is mixed for 90min.
Add about 2% water to increase the water droplets in the grease and produce a large surface area (water-oil) for enzymatic degumming.
For the centrifugal separation of oil after enzymatic degumming, heating the crude oil to 70 75 is suitable for centrifuge separation, and attention should be paid to adjusting the pH, the back pressure of the centrifuge, and the opening degree of the centripetal pump.
Advantages of enzymatic degumming: increasing the content of glycerides (DAG) and free fatty acids can increase the yield of degumming oil by 06%~1.8%。Disadvantages of enzymatic degumming: increased investment, uneven quality crude oil can not be enzymatic degumming, gum can not produce lecithin, increase the consumption of clay, enzyme preparation ** high (1500 yuan kg), the deacidification capacity of the deodorization tower should consider the original fatty acids and newly generated fatty acids, the deodorization distillate increases (increases the loss of neutral oil), and 95% of the glyceride (DAG) remains in the oil after deodorization.
Effect of enzymatic degumming: the phosphorus content of crude oil with a phosphorus content of 600 1500mg kg is degummed by PLC, and the phosphorus content of the degummed oil is less than 200mg kg, and the degumming oil with a phosphorus content of less than 5mg kg can be obtained after PLA degumming. The application effect of enzymatic degumming in oil refining is shown in the full text.
3. Nano neutralization.
Nano neutralization is after adding acid and alkali, the oil enters the nano mixer under a pressure greater than 4MPa, and is ultra-fine mixed in the emulsified state, and the contact between the oil and the chemical reagent is complete and the reaction is complete. Phosphoric acid or citric acid is added to convert non-hydrated phospholipids into hydrated phospholipids, and then alkali is added to neutralize them, and the process flow is as follows:
The main steps of nano neutralization: crude oil (30 at room temperature) is pumped from the crude oil tank into the heat exchanger to 95, * after adding acid, it enters the strong mixer, enters the acid refining retention tank for 20min and then discharges the oil, adds lye, enters the low shear mixer to mix, enters the alkali refining retention tank for about 1min, and pressurizes 6 with a pressure pump5MPa, into the nano mixer, the oil into the temporary storage tank, into the centrifuge to separate the soap feet, after water washing, centrifuge separation of wastewater, to obtain nano neutralization oil. The parameters and effects of 400t d soybean oil nano neutralization process are shown in the full text.
Soybean oil and rapeseed oil can reduce the acid content by 50% by degumming and deacidification by nano neutralization process, no excess alkali is required, no CIP automatic cleaning system is required, and the soap content in the oil is less than or equal to 150mg kg. Sunflower oil with a phosphorus content of 400 600mg kg, the phosphorus content of the degummed oil obtained by conventional hydration degumming is 110 120mg kg, and the phosphorus content of the degummed oil is 25 30mg kg by degumming with a nanomixer.
4. Conventional alkali refining and deacidification.
Conventional alkali refining is suitable for crude oil acid value (KOH) less than or equal to 25mg g, the mass fraction of the purchased lye solution is 32%, and it is diluted to about 14%. The acid value (KOH) of alkali refining is controlled at 005~0.08mg g, the water content of dry oil is less than or equal to 045%。
Fine-tuning measures for conventional alkali refining:
The alkali mixing tank is placed on the bottom floor of the workshop, and the alkali tank is placed on the top floor of the deodorization tower for self-flowing and stable alkali addition to avoid mechanical wear or failure of the metering pump.
In the neutralization process, to prevent excessive saponification of neutral oil, the residence time of the neutralization reaction tank is designed to be 10-15min. For corn oil and cottonseed oil with high alkali refining acid price, the alkali refining reaction tank adopts upper and lower output, and considering the large soap content of alkali refining oil, the plate heat exchanger is changed to a tubular heat exchanger. For the oil with low acid value in alkali refining, the alkali refining reaction tank adopts the bottom in and out of the alkali refining reactor.
The interval between slag discharge of the butterfly centrifuge is 1 60min, and the interval between slag discharge of the butterfly centrifuge is extended when it is suitable for the needs of the oil. The butterfly centrifuge oil inlet pipe is equipped with a regulating valve to keep the oil inlet of the centrifuge stable, so that the back pressure and oil outlet of the centrifuge are stable, and the separation effect is also stable. Adjust the back pressure and the opening rate of the centripetal pump according to the soap content of the oil output and the oil content of the soap feet. Control the oil content of soap feet to be less than or equal to 30%, and control the soap content in the oil to be less than or equal to 500mg kg, so as to avoid emulsification during washing.
The temperature of the washing water is higher than the oil temperature 5, the pH of the washing water is controlled at 5 6, the amount of washing water added is 6% 8%, the emulsification of oil is avoided or reduced, and the oil content of the wastewater is controlled at 1600 2000mg kg.
In order to prevent the soap foot tank pipeline from being blocked, a centrifugal pump is installed next to the oil distribution tank, and the washing wastewater is pumped into the centrifuge soap foot pipeline, and the soap foot in the centrifuge is flushed, or the soap foot pump is turned on every 5min. For the refining of 600t d, it can save 10t of soft water and sewage treatment fees per day.
*Condensate in acid and alkali refining section is used as centrifuge flushing water.
In the acid refining and alkali refining section, one key start, according to the set output is fully automatic start-up.