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1、Task 1 Gasoline StabilityI.Significance of Assessing Gasoline Stability stability refers to the property that maintains the quality of petroleum products during transport,storage and application.Gasoline with poor stability may have oxidation reactions during transport,storage and application.It is
2、easy to generate acidic substances,sticky gelatinous substances and insoluble sediments,darken oil products,lead to an decrease in octane value,corrode metal devices,cause engine malfunction and increase oil consumption.II.Factors Affecting Gasoline Stability The stability of oil products,firstly de
3、pends on the chemical composition of the oil itself,especially the amount of unsaturated hydrocarbons and non-hydrocarbon substances.Next is the conditions of oil transport,storage and application,such as light,heating,air oxidation,metal catalysis,etc.The importance of quality control in petroleum
4、products.A strong nation requires supreme quality.A good and rapid economic and social development cannot leave.Must be a good word high quality.Method of evaluating gasoline stabilityThe indicators and test methods for evaluating the stability of gasoline and aviation piston engine fuels are shown
5、in Table 8-1.1.Solvent gel content (1)Solvent gel content The sticky and non-volatile brown colloidal substance formed during the storage and use of gasoline is called colloid.Depending on the solubility,colloids can be separated into insoluble colloid,soluble colloid and adhesive colloid,which are
6、called total colloids.Solvent-washed gum mainly refers to the second kind of colloid.In addition,the colloid produced during the test process is also included.Solvent washing gum content refers to the part of automobile gasoline evaporation residue insoluble in n-heptane measured under test conditio
7、ns,expressed in mg/100mL.The actual colloid refers to the evaporation residue of oil products such as aviation piston engine fuel measured under the test conditions,and the part that has not been washed by n-heptane,expressed in mg/100mL.Solvent washed gum contentt is an important index to indicate
8、the antioxidant stability of engine fuel,using to assess the tendency of generating colloids in the engine and intake pipe,and on the intake valve.Tendency to produce colloid,It is also an important index of engine fuel storage control to judge whether the fuel can be continuously used and kept (Tab
9、le 8-1).Therefore,the existent gum should be tested regularly.(2)Overview of Method of determination solvent gum content test according to GB/T 8019-2008fuel gum content determination Method injection evaporation Method.This standard is applicable to the determination of the solvent washing gum cont
10、ent and actual gum of vehicle gasoline,vehicle ethanol gasoline,aviation piston engine fuel and jet fuel.As shown in Table 8-1,the device is divided into three parts:air intake system(air or steam,including steam superheater),measurement system(including gas flow meter and thermometer)and evaporatio
11、n bath(metal block bath or electric heating liquid bath).When measuring,the 50ml sample is controlled at temperature(150160),air flow rate(air flow is required for vehicle gasoline,and the flow rate is 1000ml/s)and evaporation time(30min)under the conditions of evaporation,and weighing the mass of t
12、he residue before and after the extraction of n-heptane,the results are reported in mg/100mL,which are called the unwashed gum content of vehicle gasoline and the solvent-washed gum content.The purpose of the test on motor gasoline is to determine the oxide formed by the sample before and under the
13、test conditions.Since non-volatile oils or additives are often intentionally added to the production of motor gasoline,it is necessary to use n-heptane to extract them from the evaporation residue.X1=（mCmDmXmZ）2000 mg/(100mLg)（8-1）X2=（mBmDmXmY）2000 mg/(100mLg)（8-2）The test method for determining act
14、ual colloid is also GB/T 509-1988Determination of Actual Colloid of Engine Fuel.At present,this method is only used for the determination of actual gum of jet fuel.2.Induction period (1)Induction period.Induction period is the time when oil products are in a stable state under specified accelerated
15、oxidation conditions(min).Induction period is an important index to evaluate the antioxidant stability of gasoline.It indicates the tendency of gasoline to oxidize and form colloids in long-term storage.A longer induction period means smaller tendency to form colloids,better antioxidant stability,mo
16、re stable oil products,and longer storage period.Automobile gasoline requires that the induction period should be not less than 480 minutes.(2)Overview of determination methods GB/T 8018-1987Determination of oxidation stability of gasoline(induction period method)is suitable for determination of oxi
17、dation stability of gasoline under accelerated conditions.See Figure 8-2 and Figure 8-3 for the tester.The test steps are as follows:(1)remove the original air in the oxygen bomb at a temperature of 1525,put the glass sample bottle into the bomb,add 50mL of sample,cover the sample bottle,close the o
18、xygen bomb tightly,oxygen is passed until the gauge pressure is 689703kPa,and then the gas is released slowly(not less than 15s)at a constant speed to flush out the original air in the bomb.(2)test the leakage of oxygen until the gauge pressure is 689703kPa,observe the pressure drop,the rapidly chan
19、ging pressure drop(generally not more than 41.4kpa)caused by the dissolution of oxygen in the sample at the beginning is not considered.If the pressure drop does not exceed 6.89kPa in the next 10min,it will be regarded as no leakage and can be tested without re-boosting.(3)During the induction perio
20、d of the determination,put the oxygen bomb containing the sample into a violent boiling water bath(avoid shaking!),Record the test start time at this time.Maintain the water bath temperature between 98102.During the test,observe the temperature on time(read to 0.1)and calculate the average temperatu
21、re to 0.1 as the test temperature.Continuously record the pressure in the oxygen bomb.If an indicator pressure gauge is used,record the pressure reading every 15min or less.Continue the test until the turning point,and record the oil at the test temperature from the time the oxygen bomb is put into
22、the water bath until the turning point.Test should be noted:If the test begins within 30min,the leak increases(with 15min stable pressure drop greatly exceeds 13.8kPa to judge),the test is invalid;if the test area of the atmospheric pressure is consistently lower than 101.3 kPa,it is allowed to add
23、a higher boiling point of the liquid to the water(such as glycol),so that the water bath temperature is maintained between 98 102.(4)disassemble and clean the instrument First cool the oxygen bomb,then slowly release(not less than 15s each time)the pressure inside the oxygen bomb,clean the oxygen bo
24、mb and the sample bottle,in preparation for the next test.(5)Calculation If the test temperature is not equal to 100,the measured induction period needs to be corrected with equation(8-3)and equation(8-4).（8-3）（8-4）.Main Factors Affecting the determination 1.Solvent gel content (1)Weighing condition
25、 control Weighing the beaker containing the sample and the beaker containing residues after the test shall be carried out strictly according to operation rules.That is to say,after drying in the specified manner,put them in a cooling container near the balance and wait for at least 2 hours,then,weig
26、h the beakers again.(2)The effect of heating temperature on the test result.Generally speaking,under the test condition that there exists oxygen in the air,colloids will be generated at a more rapid speed as the temperature becomes higher.Therefore,if the controlled water bath temperature exceeds th
27、e standard,the test result will be higher.When the temperature is too low,matrix components in oil products cannot be evaporated completely,which leads to a larger test result.(3)The sample container should be a glass instrument.For the same sample,a metal container has a catalytic effect on the for
28、mation of colloids.Thus,its result is larger than that of a glass container.It is required to use glassware as sample containers when the existent gum is tested,instead of steel or copper containers.(4)The purification degree of the air flow.Usually using a steel cylinder to supply air presents a be
29、tter effect.When air is supplied by an air compressor,lubricating oil in the equipment is easily entangled in the air supply.If the purification process doesnt work well,and this kind of oil is difficult to evaporate at the test temperature,the test result will be larger.When an industrial air duct
30、is used as a source of air flow,purification also needs much attention so as to avoid bringing water,oil and rust into the sample beaker.2.Induction period (1)Oxygen pressure.Adjust the oxygen pressure to 686.5 kPa 4.9 kPa and make sure it doesnt leak (2)Recognizer installation A leak will cause ina
31、ccuracy of the result.Use the components on the recognizer correctly and pay attention to being symmetrical when tightening them.The strength should be even,keep maintenance regularly.(3)water bath temperature The water bath temperature must be controlled in the range of 100 1 when measured.Attentio
32、n should be paid to the appropriate adjustment of the bath according to the local air pressure,such as low atmospheric pressure,when the water is heated to boiling state still can not reach the test temperature requirements,you can add the appropriate amount of glycerin or glycol,or directly use the oil bath device.Petroleum product analysis instrument displayFigure 8-4 MW4-PJ type jet evaporation type actual gummi meter Figure 8-5 SYD-8018C gasoline oxidation stability tester(induction period method)