An automatic control system and method for tower top water injection

Abstract

The application discloses a kind of tower top water injection automatic control system and method, it includes data acquisition system, water injection execution system and control system, the data acquisition system and water injection execution system are connected with control system;The data acquisition system includes real-time process parameter acquisition module, analysis test data acquisition module, the real-time process parameter data and analysis test data of data acquisition system are transported to control system, the control system calculates water injection quantity target value and water injection quantity limit value according to real-time process parameter data and analysis test data, and determines water injection quantity set value by water injection quantity target value and water injection quantity limit value, the control system compares tower top water injection quantity measured value with water injection quantity set value, controls water injection execution system to adjust tower top water injection quantity.The water injection quantity set value in the application is determined based on tower top distillation amount, saturated water injection amount and control tower top drainage ion concentration three aspects, reliable water injection control can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automatic control of overhead water injection system of distillation column or fractionating column, and particularly relates to an automatic control system and method for overhead water injection. BACKGROUND

[0002] In a refinery, the low-temperature corrosion problem of the overhead system is a common and prominent problem affecting the safe and long-period operation of the device. The main corrosion mechanism of typical overhead systems such as the atmospheric column, catalytic fractionating column and coking fractionating column of a distillation device is HCl dew point corrosion and corrosion under ammonium chloride / amine deposition scale. In order to control the overhead corrosion, the refinery generally adopts certain process corrosion prevention measures, which may specifically include electric desalting, alkali injection, neutralizing agent injection, corrosion inhibitor injection and water injection. Among them, water injection is one of the most common and effective means to alleviate overhead corrosion and salt deposition. The role of water injection is to dilute acidic substances, increase the pH value of the initial condensation zone, wash away the deposited salt, and wash away the substances that may be salted from the gas phase. Since water injection will cause the water dew point temperature to rise, the position of the initial condensation zone will change with the amount of water injection. In the overhead water injection corrosion prevention, the amount of water injection is the key parameter of water injection control. The typical value given in the literature is generally to keep 25% of the injected water in liquid state after injection at the injection point. Patent CN201511005086.8 discloses a fractionating column overhead oil and gas system water injection device and method, and proposes that the actual total amount of water injection is 20% to 30% more than the theoretical amount of water injection when the water dew point is reached. Patent CN202010505537.9 discloses a protection system and method for delaying flow corrosion of a normal overhead heat exchanger, and proposes that according to the comparison result of the real-time calculated dew point temperature and the set value, the water injection valve before the heat exchanger inlet is controlled, the water injection amount is increased when the dew point temperature is lower than the set value, and the air cooler inlet temperature is obtained. The required water injection amount when 25% of the water before the air cooler is in liquid state is calculated by ASPEN simulation, and the water injection amount should not be lower than the calculated water injection amount when adjusting the water injection amount. Patent CN201810584592.4 discloses a distillation column overhead process corrosion automatic control system, and proposes that the water injection is still kept in liquid state according to 20% to 50% of the water injection, and 25% is taken as the control value. Overall, the existing water injection amount control method is mainly based on the calculation of the "saturated water injection amount" required for the gas phase water partial pressure at the water injection point to reach the saturated water vapor pressure under this condition, and a certain excess is maintained on this basis.

[0003] However, the above control method has defects, the saturated water injection amount needs relatively complex phase equilibrium thermodynamic calculation, often needs to use commercial process simulation software, because of many input parameters, when performing online control, system reliability is not high, on the other hand, the basic starting point of the above control method is to ensure that the injected water does not all vaporize but a certain amount of liquid water exists, but cannot guarantee the effect of diluting corrosive substances and dissolving and depositing salt. Therefore, the application provides a tower top water injection control system and method, which optimizes the calculation method of the water injection amount, in addition to the conventional consideration of the saturated water injection amount, also increases the consideration of the tower top distillation amount and the control of the ion concentration of the tower top drainage, and comprehensively determines the water injection amount based on the above three factors, realizes reliable water injection control, and guarantees good fault tolerance. SUMMARY

[0004] To solve the above technical problems, the application provides a tower top water injection control system and method, which optimizes the calculation method of the water injection amount set value, and comprehensively determines the water injection amount set value through the tower top distillation amount, the saturated water injection amount and the control of the ion concentration of the tower top drainage, to realize reliable water injection control.

[0005] In order to achieve the above purpose, the technical solution adopted by the application is:

[0006] A tower top water injection automatic control system, comprising a data acquisition system, a water injection execution system and a control system, the data acquisition system and the water injection execution system are connected with the control system;The data acquisition system comprises a real-time process parameter acquisition module and an analysis and test data acquisition module, the data acquisition system sends the collected real-time process parameter data and analysis and test data to the control system, the control system calculates a water injection amount target value and a water injection amount limit value according to the real-time process parameter data and analysis and test data, and determines a water injection amount set value through the water injection amount target value and the water injection amount limit value, the control system compares the measured value of the tower top water injection amount with the water injection amount set value, and controls the water injection execution system to adjust the tower top water injection amount;

[0007] The real-time process parameter acquisition module is connected with a DCS or MES system, and is used to collect real-time process parameters in the DCS or MES system, wherein the real-time process parameters include tower top operating pressure, water injection point operating temperature, water injection temperature, water injection steam amount, tower top water injection amount, tower top drainage amount, tower top oil return amount, tower top oil extraction amount and tower top non-condensable gas amount;

[0008] The analysis and test data acquisition module is connected with a LIMS system, and is used to collect analysis and test data in the LIMS system, wherein the analysis and test data include tower top oil density, tower top oil distillation range, tower top non-condensable gas composition and ion concentration of tower top drainage.

[0009] In the technical solution, the real-time process parameter data in the DCS or MES system is real-time detection data of relevant detection instruments installed in the overhead system, such as pressure gauges, temperature gauges, steam flow detection instruments, liquid flow meters, etc.

[0010] Further, the data acquisition system further comprises an ion concentration data acquisition module connected with the online water quality multi-parameter measurement system, for acquiring ion concentration of the overhead drainage detected by the online water quality multi-parameter measurement system.

[0011] In the technical solution, the ion concentration data is also stored in the LIMS system, and the data in the LIMS system is entered after offline analysis and testing of samples, which is usually 2-3 times per week to once per month, and the frequency is relatively low, and the analysis and testing data cannot be updated in time, so the online water quality multi-parameter measurement system is set, the detection frequency of which can be set to 1 time per hour to 1 time per day, so that the chlorine ion concentration, ammonia nitrogen concentration and sulfide concentration in the overhead drainage can be acquired and calculated in real time, and the control accuracy is improved.

[0012] Further, the ion concentration data comprises chlorine ion concentration, ammonia nitrogen concentration and sulfide concentration of the overhead drainage.

[0013] Further, the water injection execution system comprises a water injection pipeline, a water injection pump and a water injection adjusting device, and the water injection adjusting device is a regulating valve or a water pump frequency converter, and the regulating valve is arranged on the water injection pipeline.

[0014] The application further provides a water injection control method for a tower top, comprising the following steps:

[0015] (1) The data acquisition system acquires real-time process parameter data and analysis and testing data through a real-time process parameter acquisition module and an analysis and testing data acquisition module, wherein the real-time process parameters comprise overhead operating pressure, water injection point operating temperature, water injection temperature, steam injection amount, overhead water injection amount, overhead drainage amount, overhead oil return amount, overhead oil extraction amount and overhead non-condensable gas amount, and the analysis and testing data comprises overhead oil density, overhead oil distillation range, overhead non-condensable gas composition, chlorine ion concentration, ammonia nitrogen concentration and sulfide concentration of the overhead drainage;

[0016] (2) The data acquisition system transmits the acquired real-time process parameter data and analysis and testing data to a control system, the control system calculates a water injection amount target value and a water injection amount limit value, and determines a water injection amount set value through the water injection amount target value and the water injection amount limit value, the control system compares the measured value of the overhead water injection amount with the water injection amount set value, controls the water injection execution system to adjust the overhead water injection amount, and simultaneously, the control system feeds back the water injection amount set value to the DCS or MES system, so that the water injection amount set value and the measured value of the overhead water injection amount can be monitored by the staff from the DCS or MES system.

[0017] Further, the method for determining the water injection amount set value in step (2) is: if the water injection amount target value W is within the water injection amount limit value range, then the water injection amount target value is taken as the water injection amount set value; if the water injection amount target value W is greater than the upper limit value W max of the water injection amount, then the upper limit value W max of the water injection amount is taken as the set value; if the water injection amount target value W is less than the lower limit value W min of the water injection amount, then the lower limit value W min of the water injection amount is taken as the set value.

[0018] Further, the calculation formulas of the water injection amount target value W and the water injection amount limit value W min , W max in step (2) are as follows:

[0019] Water injection amount target value:

[0020] W = EW1 + (1 - E)W2;

[0021] wherein E is a weight, E is 0-1, preferably E = 0.5; W1 is a first water injection amount determined based on the tower top distillation amount; W2 is a second water injection amount determined based on the saturated water injection amount;

[0022] Water injection amount limit value:

[0023] W min = max{min{W 1min , W 2min}, W3};

[0024] W max = min{max{W 1max , W 2max , W3}, 2W0};

[0025] wherein W 1min , W 1max are the lower limit value and the upper limit value of the first water injection amount determined based on the tower top distillation amount, W 2min , W 2max are the lower limit value and the upper limit value of the second water injection amount determined based on the saturated water injection amount, W0 is the current water injection amount measurement value, and W3 is a third water injection amount determined based on the tower top drainage ion concentration.

[0026] Further, the calculation formulas of the first water injection amount W1 and the first water injection amount lower limit value W 1min , the first water injection amount upper limit value W 1max are as follows:

[0027] W1 = A · F T ;

[0028] W1min = A l · F T ;

[0029] W 1max = A h · F T ;

[0030] wherein F T is the total distillate amount at the top of the column, F T = the amount of oil return at the top of the column + the amount of oil extraction at the top of the column + the amount of non-condensable gas at the top of the column + the amount of natural water at the top of the column, A, A1, A h are coefficients, and A1 h < 0.15.

[0031] In the above technical solution, the first water injection amount determined based on the distillate amount at the top of the column is actually a percentage relative to the distillate amount of the material at the top of the column, the water injection amount can be determined according to the distillate amount of the material at the top of the column, and A1 h < 0.15.

[0032] The above coefficients are preferably A = 6%, A l = 3%, and A h = 10%.

[0033] Further, the calculation formulas of the second water injection amount W2 and the lower limit value W 2min and the upper limit value W 2max of the second water injection amount are as follows:

[0034] W2 = B· W S ;

[0035] W 2min = B l · W S ;

[0036] W 2max = B h · W S ;

[0037] wherein W S is the saturated water injection amount, B, B l , B h are coefficients, and 1 < B l < B < B h < 2.

[0038] In the above technical solution, the saturated water injection amount is the water injection amount required for water in the gas phase to reach saturation when the overhead material reaches phase equilibrium. Generally, the overhead oil gas is in a gaseous phase at a temperature higher than the dew point and is extracted from the overhead into a volatile line, and then is mixed with the water injection at a relatively low temperature, when the two materials reach thermal equilibrium, the equilibrium temperature is between the oil gas temperature and the water injection temperature. When the water injection amount is very small, the equilibrium temperature is still higher than the water dew point, and the water is completely vaporized; as the water injection amount increases, the equilibrium temperature decreases, and the water dew point temperature rises, when they are equal, that is, the water in the gas phase reaches saturation, and the corresponding water amount is the saturated water injection amount. In the present application, when calculating the second water injection amount W2, W2 is in excess of a certain proportion on the basis of the saturated water injection amount, which is also the main setting principle of the overhead water injection in various standard specifications. However, the saturated water injection amount requires many input data for calculation, and also involves iterative calculation, and there is a possibility of calculation failure due to missing input parameters or non-convergent results, therefore, in the present application, water injection control is not separately relied on W2 to improve the calculation reliability.

[0039] In the present application, the saturated water injection amount is calculated through two layers of nested loops, wherein the inner loop is used to solve the equilibrium temperature Tm of the mixed material after water injection, and this step is equivalent to performing adiabatic flash calculation.

[0040] According to the heat balance before and after water injection, there is:

[0041] H b (T m )-H a =0;

[0042] Wherein, H b (Tm) is the enthalpy value of the mixed material after water injection, which is a function of temperature; Ha is the total enthalpy value of the mixed material before mixing, which can be calculated according to known conditions, and is equivalent to a constant. The above formula is a one-variable nonlinear equation about Tm, and Tm can be obtained by solving through a proper iterative method. The iteration termination condition is:

[0043] |H b -H a |<ε1;

[0044] Wherein, ε1 is the iteration error, which is usually taken as 10 -6 ;

[0045] The outer loop is used to solve the saturated water injection amount Ws, and this step is equivalent to performing isothermal flash calculation. According to the meaning of the saturated water injection amount, there is:

[0046] T m (W s )-T b (W s )=0;

[0047] Wherein, Tm(Ws) and Tb(Ws) are the equilibrium temperature and water dew point temperature after water injection, respectively, and are functions of water injection amount. The above formula is a nonlinear equation about Ws, and Ws can be obtained by solving the equation through appropriate iteration method. The iteration termination condition is:

[0048] |T m -T b |<ε2; wherein, ε2 is iteration error, usually taken 10 -6 .

[0049] Further, B = 1.25, B1 = 1.1, B h = 1.5.

[0050] Further, the calculation formula of the third water injection amount W3 is:

[0051]

[0052] Wherein, W Cl is water injection amount calculated according to chloride ion concentration, is water injection amount calculated according to ammonium hydrosulfide concentration;

[0053] The calculation formula of W Cl and W is respectively:

[0054]

[0055]

[0056] Wherein, W0 is current water injection amount measurement value, W n is tower top natural water amount (tower top natural water amount is water amount entering tower top before water injection, which can be determined according to steam injection amount or by subtracting tower top water injection amount from tower top drainage amount); C C1 is chloride ion concentration of drainage, unit mg / L; C NH3+NH4+ is ammonia nitrogen concentration of drainage, unit mg / L; C H2S is sulfide concentration of drainage, unit mg / L; C and D are coefficients, C = 30-160, D = 2.

[0057] In the technical solution, the calculation of the third water injection amount W3 considers the dilution effect of water injection on the main corrosive medium, and the water injection amount is limited according to the main corrosive ion concentration control limit. For the overhead system, the main corrosive environment is HCl-H2S-NH3-H2O, and the ions to be focused on are chloride ions, sulfides, ammonia nitrogen and pH (hydrogen ions). At the measurement temperature, the concentrations of chloride ions and ammonium bisulfide are basically linearly related to the amount of liquid water, and since the overhead drainage is generally neutral, and due to the buffering effect of H2S, NH3 and other weak acids and weak bases, the pH value is very limited by the water injection amount. Therefore, in the present application, the water injection amount is limited according to the concentrations of chloride ions and ammonium bisulfide.

[0058] The beneficial effects of the present application are:

[0059] The overhead water injection control system and method provided by the present application automatically control overhead water injection for corrosion prevention based on online measurement data, can real-time regulate and control the overhead water injection amount according to real-time data, reduce water injection cost while ensuring corrosion prevention; at the same time, the present application optimizes the calculation method of the water injection amount set value, determines the water injection amount set value from three aspects of overhead distillation amount, saturated water injection amount and control of overhead drainage ion concentration, can realize more refined corrosion prevention control, and has good reliability and fault tolerance. BRIEF DESCRIPTION OF DRAWINGS

[0060] In order to clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0061] Figure 1 is a schematic diagram of the overhead water injection control system of the present application;

[0062] Figure 2 is a flow chart of the overhead water injection control system of the present application;

[0063] Figure 3 is a calculation flow chart of the saturated water injection amount. DETAILED DESCRIPTION

[0064] The present application provides an overhead water injection automatic control system and method, in order to make the purpose, technical scheme and effect of the present application more clear and definite, the present application will be further described in detail. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0065] The present application will be described in detail below with reference to the drawings:

[0066] Referring to Figure 1 and Figure 2 The present application provides a kind of tower top water injection automatic control system, it includes data acquisition system, water injection execution system and control system, the data acquisition system and water injection execution system are connected with control system;The data acquisition system includes real-time process parameter acquisition module, analysis test data acquisition module and ion concentration data acquisition module;The real-time process parameter data and analysis test data of the data acquisition system are transported to control system, and the control system calculates water injection quantity target value and water injection quantity limit value according to real-time process parameter data and analysis test data, and determines water injection quantity set value by water injection quantity target value and water injection quantity limit value, the control system compares tower top water injection quantity measured value with water injection quantity set value, controls water injection execution system to adjust tower top water injection quantity, i.e. the regulating valve on water injection pipeline or the water pump frequency converter of regulating water injection pump is adjusted.

[0067] Specifically, the above-mentioned real-time process parameter acquisition module is connected with DCS or MES system, which is used to collect real-time process parameters in DCS or MES system, and the real-time process parameters include tower top operating pressure, water injection point operating temperature, water injection temperature, water injection steam quantity, tower top water injection quantity, tower top water discharge quantity, tower top oil return quantity, tower top oil extraction quantity, and tower top non-condensable gas quantity; the real-time process parameter data in DCS or MES system is the data detected by the related detection instruments installed in the tower top system, such as pressure gauge, temperature gauge, steam flow detector, liquid flowmeter, etc.

[0068] The above-mentioned analysis test data acquisition module is connected with LIMS system, which is used to collect analysis test data in LIMS system, and the analysis test data includes tower top oil density, tower top oil distillation range, tower top non-condensable gas composition, and tower top water discharge ion concentration.

[0069] The above-mentioned ion concentration data acquisition module is connected with online water quality multi-parameter measurement system, which is used to collect tower top water discharge ion concentration detected by the online water quality multi-parameter measurement system, and the detection frequency can be set to 1 time / hour-1 time / day, so that the tower top water discharge ion concentration can be collected and calculated in real time, and the ion concentration data includes tower top water discharge chloride ion concentration, ammonia nitrogen concentration, and sulfide concentration.

[0070] The above-mentioned water injection execution system includes water injection pipeline, water injection pump and water injection regulating device, the water injection regulating device is regulating valve or water pump frequency converter, the regulating valve is arranged on the water injection pipeline, and the water pump frequency converter is connected with water injection pump motor.

[0071] The method for determining water injection quantity set value in the above-mentioned tower top water injection automatic control system is as follows: if water injection quantity target value W is within the range of water injection quantity limit value, then water injection quantity target value is taken as water injection quantity set value; if water injection quantity target value W is greater than water injection quantity upper limit value W maxW max as the set value; if the water injection amount target value W is less than the water injection amount lower limit value W min , the water injection amount lower limit value W min is taken as the set value.

[0072] The water injection amount target value and the water injection amount limit value are obtained by comprehensively calculating the overhead distillation amount, the saturated water injection amount and the ion concentration of the overhead drainage.

[0073] The overhead water injection automatic control method of the present application will be described below in combination with specific examples, and the calculation process of the water injection amount target value and the water injection amount limit value will be described in detail, and then the water injection amount set value is determined according to the water injection amount target value and the water injection amount limit value.

[0074] Example 1

[0075] In this embodiment, the overhead water injection of a coking fractionating tower is automatically controlled by using the overhead water injection control system described above, and the control method is as follows:

[0076] (1) The data acquisition system obtains input parameters

[0077] The relevant real-time process parameters and analysis data are obtained from the DCS system, the LIMS system and the online water quality multi-parameter measurement system, wherein the detection frequency of the online water quality multi-parameter measurement system is set to 1 time / hour, and the ion concentration related data of the overhead drainage is obtained from the online water quality multi-parameter measurement system. The above-mentioned related data are obtained in a real-time and online manner, and the data acquisition system reads these input data at a frequency of 1 time / hour, and then calculates and controls the water injection amount. In order to facilitate the description of the entire control process, the collection data of the data acquisition system at a certain time are listed in Table 1:

[0078] Table 1

[0079]

[0080]

[0081] (2) The data acquisition system transmits the collected data to the control system, and the control system calculates the water injection amount target value and the water injection amount limit value

[0082] (21) The first water injection amount W1 and the first water injection amount lower limit value W 1min , the first water injection amount upper limit value W 1max are calculated according to the overhead distillation amount;

[0083] From the data in Table 1, it can be obtained that:

[0084] The overhead oil return amount = 0 (t / h);

[0085] The overhead oil extraction amount = 44 (t / h);

[0086] The amount of overhead non-condensable gas = 36200 - 880 - 640 = 34680 (Nm 3 / h);

[0087] The molecular weight of overhead non-condensable gas = (16 x 42.56 + 30 x 16.98 + 28 x 2.02 + 44 x 8.36 + 42 x 3.58 + 58 x 4.63 + 72 x 2.47 + 86 x 0.3 + 2 x 8.16 + 44 x 0.12 + 32 x 0.77 + 28 x 4.09 + 28 x 0.24 + 34 x 5.72) / 100 = 26;

[0088]

[0089] In the calculation of the amount of overhead non-condensable gas, the unit of the amount of overhead non-condensable gas is usually Nm 3 / h, which needs to be converted into t / h, and the conversion method is:

[0090] Wherein, M w is the molecular weight of overhead non-condensable gas:

[0091] Wherein, n i is the content of component i in the overhead non-condensable gas, with the unit of v / v%, and M wi is the molecular weight of component i;

[0092] The amount of overhead natural water = 14 + 3 = 17 (t / h);

[0093] The total amount of overhead distillate F T = the amount of overhead oil return + the amount of overhead oil extraction + the amount of overhead non-condensable gas + the amount of overhead natural water = 0 + 44 + 40.2 + 17 = 101.2 (t / h);

[0094] Through the above data calculation, it is obtained that:

[0095] W1 = 6% x F T = 0.06 x 101.2 = 6.1 (t / h);

[0096] W 1min = 3% x F T = 0.03 x 101.2 = 3.0 (t / h);

[0097] W 1max = 10% x F T = 0.1 x 101.2 = 10.1 (t / h);

[0098] (22) According to the amount of saturated water injection, the second water injection amount W2 and the lower limit value W 2min , the upper limit value W2max ;

[0099] Saturation water injection amount W s According to Figure 3 the program shown in the calculation program, which can be obtained by those skilled in the art from the prior art, the present embodiment will not be described, according to the program of Figure 3 Saturation water injection amount calculated by the program of

[0100] W s = 3.8 (t / h);

[0101] The corresponding saturation water injection mixture balance temperature is 99.1℃, and the enthalpy is 9.77765 x 10 7 kJ;

[0102] Through the above data calculation:

[0103] W2 = 1.25 x W S = 1.25 x 3.8 = 4.7 (t / h);

[0104] W 2min = 1.1 x W S = 4.2 (t / h);

[0105] W 2max = 1.5 x W S = 5.7 (t / h);

[0106] (23) According to the ion concentration of the overhead water, the third water injection amount W3 is calculated;

[0107] From the data in Table 1:

[0108] The current water injection amount measurement value: W0 = 4.6 (t / h);

[0109] The overhead natural water amount: W n = 17 (t / h);

[0110] Chloride ion concentration measurement value: C Cl = 17 (mg / L);

[0111] Ammonia nitrogen concentration measurement value:

[0112] Since there is no available sulfide data, the NH4HS concentration is calculated according to the ammonia nitrogen concentration, and the above data is calculated as follows:

[0113]

[0114] In this embodiment, the coefficient C is taken as 30, i.e. the concentration of Cl ions in the overhead drainage is controlled within 30 mg / L. For the coking fractionating column, the concentration of Cl ions in the overhead drainage is relatively low, and it is usually required to be controlled within 30 mg / L.

[0115]

[0116] Thus, we have:

[0117]

[0118] (24) Determining the water injection amount target value W

[0119] W = 0.5 x W1 + 0.5 x W2 = 0.5 x 6.1 + 0.5 x 4.7 = 5.4 (t / h);

[0120] (25) Determining the water injection amount limiting value

[0121] W min = max{min{3.0, 4.2}, 1.7} = 3.0 (t / h);

[0122] W max = min{max{10.1, 5.7, 1.7}, 2 x 4.6} = 9.2 (t / h);

[0123] (3) Determining the water injection amount set value

[0124] The control system determines the water injection amount set value according to the calculated water injection amount target value and the water injection amount limiting value. In this embodiment, W min < W < W max , and the water injection amount set value is determined as W. That is, the water injection amount set value calculated in this embodiment is 5.4 t / h, and the water injection amount set value is output to the water injection execution system. The water injection execution system can execute water injection amount adjustment action according to the water injection amount set value and the current water injection amount measurement value. At the same time, the water injection amount set value 5.4 t / h is fed back to the DCS system, and the staff can monitor the water injection amount set value and the current water injection amount measurement value from the DCS system. After completing the adjustment, the next measurement, calculation and adjustment process is waited. In this embodiment, the adjustment frequency is set to 1 time / hour.

[0125] Embodiment 2

[0126] In this embodiment, the above-mentioned overhead water injection control system is used to automatically control the overhead water injection of a certain atmospheric column, and the control method is as follows:

[0127] (1) The data acquisition system acquires input parameters

[0128] The relevant real-time process parameters and analysis data are obtained from the MES system, the LIMS system and the online water quality multi-parameter measurement system, wherein the detection frequency of the online water quality multi-parameter measurement system is set to 1 time / hour, the ion concentration related data of the tower top drainage is obtained from the online water quality multi-parameter measurement system, the above related data are obtained in a real-time and online manner, and the data acquisition system reads these input data at a frequency of 1 time / hour, and then calculates and controls the water injection amount. In order to facilitate the description of the entire control process, the collection data of the data acquisition system at a certain time are listed, as shown in Table 2:

[0129] Table 2

[0130]

[0131]

[0132] The atmospheric tower device of the embodiment has two water injection points, the first one is located at the volatilization line position of the atmospheric tower top outlet, and the second one is located at the inlet position of the atmospheric tower top air cooler, and there are 10 air coolers in parallel at this position, and each air cooler has two inlet paths, therefore, the second water injection point has 20 branch paths. The first and second water injection points need to be calculated respectively in the embodiment.

[0133] (2) The data acquisition system transmits the collected data to the control system, the control system calculates the first water injection amount target value of the first water injection point and the first and second water injection amount limit values of the first water injection point, and determines the water injection amount set value of the first water injection point;

[0134] (21) The first water injection amount W 11 of the first water injection point is calculated according to the tower top distillation amount; 11min , the first water injection amount upper limit value W 11max of the first water injection point;

[0135] From the data in Table 2, it can be obtained that:

[0136] The tower top oil return amount = 0 (t / h);

[0137] The tower top oil extraction amount = 62.3 (t / h);

[0138] The tower top non-condensable gas amount = 270 (Nm 3 / h);

[0139] The tower top non-condensable gas molecular weight = (16×13.55+30×26.9+28×0.13+44×19.64+42×0.06+58×6.21+72×0.935+86×0.045+2×2.165+44×3.19+32×0.775+28×22.92+28×0.155+34×0.335) / 100 = 32.5;

[0140]

[0141] Natural water volume at the top of the tower = 6.7 (t / h);

[0142] Total distillate F from the top of the column T =Oil return flow rate at the top of the tower + oil extraction rate at the top of the tower + non-condensable gas flow rate at the top of the tower + natural water flow rate at the top of the tower = 0 + 62.3 + 0.4 + 6.7 = 69.4 (t / h);

[0143] W1 = 6% × F T =0.06 × 69.4 = 4.2 (t / h);

[0144] W 11min =3% × F T =0.03 × 69.4 = 2.1 (t / h);

[0145] W 11max =10% × F T =0.1 × 69.4 = 6.9 (t / h);

[0146] (22) Calculate the second water injection volume W at the first water injection point based on the saturated water injection volume. 21 and the second lower limit value W of the water injection volume at the first water injection point 21min The second upper limit of water injection volume W 21max ;

[0147] Saturated water injection volume W s according to Figure 3 The program shown calculates, according to Figure 3 The saturated injection volume calculated by the program is:

[0148] W s =5.1 (t / h);

[0149] The corresponding equilibrium temperature of the mixture after saturated water injection is 109.2℃, and the enthalpy is 5.40138×10⁻⁶. 7 kJ;

[0150] Based on the above data, the following calculations were performed:

[0151] W 21 =1.25×W S =1.25 × 5.1 = 6.4 (t / h);

[0152] W 21min =1.1×W S = 5.6 (t / h);

[0153] W 21max =1.5×W S =7.6 (t / h);

[0154] (23) Calculate the third water injection amount W of the first water injection point according to the ion concentration of the overhead water 31 ;

[0155] The relevant data of the first water injection point can be obtained from the data in Table 1:

[0156] The current water injection amount measurement value: W0=5+18=23 (t / h);

[0157] The natural water amount of the column top: W n =6.7 (t / h);

[0158] The chloride ion concentration measurement value: C Cl =126 (mg / L);

[0159] The ammonia nitrogen concentration measurement value:

[0160] The sulfide concentration measurement value:

[0161] The calculation result is:

[0162]

[0163] In this embodiment, the coefficient C is 160, that is, the concentration of Cl ions in the overhead water is controlled within 160 mg / L. Generally, for a normal pressure column, the ion concentration of the overhead water is relatively high, and if the Cl ion concentration is controlled within a lower range, the water injection amount will be too large. Of course, the coefficient can also be determined according to the chloride ion concentration detected by the online water quality multi-parameter measurement system, and C is slightly greater than C Cl ;

[0164]

[0165] Thus, the above data gives:

[0166]

[0167] (24) Determine the water injection amount target value W1 of the first water injection point

[0168] W1=0.5×W 11 +0.5×W 21 =0.5×4.2+0.5×6.4=5.3 (t / h);

[0169] (25) Determine the water injection amount limit value of the first water injection point

[0170] W 1min = max{min{2.1, 5.6}, 0}=2.1 (t / h);

[0171] W 1max = min{max{6.9, 7.6, 0}, 2x5} = 7.6 (t / h);

[0172] (26) determining the injection amount set value of the first injection point

[0173] The control system determines the injection amount set value according to the calculated injection amount target value and the injection amount limit value; in this embodiment, the calculated injection amount target value is W 1min <W1<W 1max , and the injection amount set value is determined as W1. That is, the injection amount set value of the first injection point calculated in this embodiment is 5.3 t / h, and the injection amount set value is output to the injection execution system, which can execute the injection amount adjustment action according to the injection amount set value and the current injection amount measurement value; at the same time, the injection amount set value 5.3 t / h is fed back to the MES system, and the staff can monitor the injection amount set value and the current injection amount measurement value from the MES system. After completing the adjustment once, the next measurement, calculation and adjustment process is waited. In this embodiment, the adjustment frequency is set to 1 time / hour.

[0174] (3) The data acquisition system transmits the collected data to the control system, which calculates the injection amount target value of the second injection point and the first and second injection amount limit values of the second injection point, and determines the injection amount set value of the second injection point;

[0175] (31) determining the first, second and third injection amounts of the second injection point

[0176] In fact, the first injection point has met the requirements of 3-10% of the tower top distillation amount and 10-50% excess of the saturated injection amount, so for the second injection point, the first injection amount W 12 calculated based on the tower top distillation amount and the second injection amount W 22 calculated based on the saturated injection amount can be recorded as:

[0177] W 12 = W 22 = 0; and W 12min = W 22max = 0;

[0178] But the requirement of controlling the ion concentration of the tower top still needs to be met, so the third injection amount W 32 of the second injection point needs to be calculated according to the ion concentration of the tower top.

[0179] The relevant data of the second injection point can be obtained from the data in Table 1:

[0180] The current injection amount measurement value: W0=18 (t / h);

[0181] The tower top natural water amount: W n= 6.7 + 5 = 11.7 (t / h);

[0182] Chloride ion concentration measurement value: C Cl = 126 (mg / L);

[0183] Ammonia nitrogen concentration measurement value:

[0184] Sulfide concentration measurement value:

[0185] Calculated:

[0186]

[0187]

[0188] Thus, from the above data:

[0189]

[0190] (32) Determine the injection volume target value W2 of the second injection point

[0191] W2 = 0.5 x W 12 + 0.5 x W 22 = 0.5 x 0 + 0.5 x 0 = 0 (t / h);

[0192] (33) Determine the injection volume limit value of the second injection point

[0193] W 2min = max{0, 11.7} = 11.7 (t / h);

[0194] W 2max = min{max{0, 11.7}, 2 x 18} = 11.7 (t / h);

[0195] (34) Determine the injection volume set value of the second injection point

[0196] The control system determines the injection volume set value according to the calculated injection volume target value and injection volume limit value; in this embodiment, W2 < W 2min , the injection volume set value is W 2min , that is, the injection volume set value of the second injection point calculated in this embodiment is 11.7 t / h, and the injection volume set value is output to the injection execution system, which can execute the injection volume adjustment action according to the injection volume set value and the current injection volume measurement value; at the same time, the injection volume set value 11.7 t / h is fed back to the MES system, and the staff can monitor the injection volume set value and the current injection volume measurement value from the MES system. After completing the adjustment once, wait for the next measurement, calculation and adjustment process. In this embodiment, the adjustment frequency is set to 1 time / hour.

[0197] Example 3

[0198] This example uses the above-mentioned overhead water injection control system to automatically control the overhead water injection of a catalytic fractionating column, and the control method is as follows:

[0199] (1) The data acquisition system obtains input parameters

[0200] Real-time process parameters and analysis data are obtained from the MES system, the LIMS system and the online water quality multi-parameter measurement system, wherein the detection frequency of the online water quality multi-parameter measurement system is set to 1 time / hour, and the ion concentration related data of the column overhead drainage is obtained from the online water quality multi-parameter measurement system. The above-mentioned related data are obtained in a real-time and online manner, and the data acquisition system reads these input data at a frequency of 1 time / hour, and then calculates and controls the water injection amount. In order to facilitate the description of the entire control process, the collection data of the data acquisition system at a certain time are listed, as shown in Table 3:

[0201] Table 3

[0202]

[0203]

[0204] (2) The data acquisition system transmits the collected data to the control system, and the control system calculates the water injection amount target value and the water injection amount limit value

[0205] (21) According to the column overhead distillation amount, the first water injection amount W1 and the first water injection amount lower limit value W 1min , and the first water injection amount upper limit value W 1max are calculated.

[0206] From the data in Table 3, it can be obtained that:

[0207] The column overhead oil return amount = 0 (t / h);

[0208] The column overhead oil extraction amount = 0 + 151 = 151 (t / h);

[0209] The column overhead non-condensable gas amount = 47811 (Nm 3 / h);

[0210] Molecular weight of overhead non-condensable gas = (2 x 11.43 + 28 x 9.29 + 32 x 2.5 + 16 x 12.9 + 30 x 6.29 + 28 x 5.88 + 44 x 5.61 + 42 x 16.18 + 56 x 8.54 + 56 x 2.28 + 54 x 4.12 + 54 x 2.55 + 54 x 1.84 + 72 x 4.44 + 72 x 0.32 + 70 x 1.57 + 86 x 1.32 + 34 x 1.58 + 44 x 1.03 + 28 x 0.21) / 100 = 35.8:

[0211]

[0212] Natural water amount of overhead = 7.49 + 0.89 + 15.17 + 0.25 + 8.71 + 5.58 = 38 (t / h);

[0213] Total distillation amount F of overhead T = overhead oil return amount + overhead oil extraction amount + overhead non-condensable gas amount + natural water amount of overhead = 0 + 151 + 76.4 + 38 = 265.4 (t / h);

[0214] Through the above data calculation:

[0215] W1 = 6% x F T = 0.06 x 265.4 = 15.9 (t / h);

[0216] W 1min = 3% x F T = 0.03 x 265.4 = 8.0 (t / h);

[0217] W 1max = 10% x F T = 0.1 x 265.4 = 26.5 (t / h);

[0218] (22) According to the saturated water injection amount, the second water injection amount W2 and the lower limit value W 2min of the second water injection amount, and the upper limit value W 2max of the second water injection amount are calculated.

[0219] The saturated water injection amount W s is calculated according to the procedure shown in Figure 3 , and the saturated water injection amount calculated according to the procedure of Figure 3 is:

[0220] W s = 6.3 (t / h);

[0221] The corresponding saturated water injection mixture material balance temperature is 109.0°C, and the enthalpy value is 2.16046 x 10 8 kJ;

[0222] From the above data, the following is calculated:

[0223] W2= 1.25 x W S = 1.25 x 6.3 = 7.9 (t / h);

[0224] W 2mi n= 1.1 x W S = 6.9 (t / h);

[0225] W 2max = 1.5 x W S = 9.4 (t / h);

[0226] (23) The third water injection amount W3 is calculated according to the ion concentration of the overhead water;

[0227] From the data in Table 1, the following is obtained:

[0228] The current water injection amount measurement value: W0= 13 (t / h);

[0229] The overhead natural water amount: W n = 38 (t / h);

[0230] The chloride ion concentration measurement value: C Cl = 144.5 (mg / L);

[0231] The ammonia nitrogen concentration measurement value:

[0232] The sulfide concentration measurement value:

[0233] From the above data, the following is calculated:

[0234]

[0235] In this embodiment, the coefficient C is taken as 160, i.e., the Cl ion concentration in the overhead water is controlled within 160 mg / L. Generally, for a catalytic fractionating column, the ion concentration of the overhead water is relatively high, and if the Cl ion concentration is controlled in a lower range, the water injection amount will be too large. Of course, the coefficient can also be determined according to the Cl ion concentration in the overhead water detected by the online water quality multi-parameter measurement system, and C is slightly greater than C Cl ;

[0236]

[0237] Thus, the following is obtained:

[0238]

[0239] (24) The water injection amount target value W

[0240] W = 0.5 x W1 + 0.5 x W2 = 0.5 x 15.9 + 0.5 x 7.9 = 11.9 (t / h) ;

[0241] (25) determining the water injection amount limit value

[0242] W min = max{min{8.0, 6.9}, 8.0} = 8.0 (t / h) ;

[0243] W max = min{max{26.5, 9.4, 8.0}, 2 x 13} = 26 (t / h) ;

[0244] (3) determining the water injection amount set value

[0245] The control system determines the water injection amount set value according to the calculated water injection amount target value and the water injection amount limit value. In this embodiment, W min < W < W max , and the water injection amount set value is determined as W. That is, the water injection amount set value calculated in this embodiment is 11.9 t / h, and the water injection amount set value is output to the water injection execution system. The water injection execution system can execute water injection amount adjustment action according to the water injection amount set value and the current water injection amount measurement value; at the same time, the water injection amount set value 11.9 t / h is fed back to the MES system, and the staff can monitor the water injection amount set value and the current water injection amount measurement value from the MES system. After completing the adjustment once, the next measurement, calculation and adjustment process is waited. In this embodiment, the adjustment frequency is set to 1 time / hour.

[0246] It should be noted that the parts not mentioned in the present application can be realized by using or referring to the existing technology.

[0247] Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present application should also be within the scope of protection of the present application.

Claims

1. An automatic control system for overhead water injection, characterized in that, The application relates to a water injection control system for a tower, which comprises a data acquisition system, a water injection execution system and a control system, wherein the data acquisition system and the water injection execution system are connected with the control system; the data acquisition system comprises a real-time process parameter acquisition module and an analysis and test data acquisition module; the data acquisition system transmits the collected real-time process parameter data and analysis and test data to the control system; the control system calculates a water injection amount target value and a water injection amount limit value according to the real-time process parameter data and the analysis and test data, and determines a water injection amount set value through the water injection amount target value and the water injection amount limit value; the control system compares a measured value of the tower top water injection amount with the water injection amount set value, and controls the water injection execution system to adjust the tower top water injection amount; the real-time process parameter acquisition module is connected with a DCS or MES system, and is used for collecting real-time process parameters in the DCS or MES system; the real-time process parameters include a tower top operating pressure, a water injection point operating temperature, a water injection temperature, a water injection steam amount, a tower top water injection amount, a tower top drainage amount, a tower top oil return amount, a tower top oil extraction amount and a tower top non-condensable gas amount; the analysis and test data acquisition module is connected with a LIMS system, and is used for collecting analysis and test data in the LIMS system; the analysis and test data includes a tower top oil density, a tower top oil distillation range, a tower top non-condensable gas composition and a tower top drainage ion concentration; the water injection amount target value is calculated according to the real-time process parameter data and the analysis and test data; the water injection amount limit value is calculated according to the real-time process parameter data and the analysis and test data; the data acquisition system further comprises an ion concentration data acquisition module which is connected with an online water quality multi-parameter measurement system, and is used for collecting the tower top drainage ion concentration detected by the online water quality multi-parameter measurement system; the ion concentration data includes a tower top drainage chlorine ion concentration, an ammonia nitrogen concentration and a sulfide concentration; the water injection execution system comprises a water injection pipeline, a water injection pump and a water injection adjusting device; the water injection adjusting device is a regulating valve or a water pump frequency converter; the regulating valve is arranged on the water injection pipeline; and the water pump frequency converter is connected with a water injection pump motor. The application further relates to a water injection control method for a tower, which comprises the following steps: (1) a data acquisition system acquires real-time process parameter data and analysis and test data through a real-time process parameter acquisition module and an analysis and test data acquisition module; the real-time process parameters include a tower top operating pressure, a water injection point operating temperature, a water injection temperature, a water injection steam amount, a tower top water injection amount, a tower top drainage amount, a tower top oil return amount, a tower top oil extraction amount and a tower top non-condensable gas amount; the analysis and test data includes a tower top oil density, a tower top oil distillation range, a tower top non-condensable gas composition, a tower top drainage chlorine ion concentration, an ammonia nitrogen concentration and a sulfide concentration; The water injection amount target value The water injection amount limit value , The calculation formulas of the water injection amount target value, the water injection amount limit value, and the water injection amount limit value are as follows, respectively. (2) the data acquisition system transmits the collected real-time process parameter data and analysis and test data to a control system; the control system calculates a water injection amount target value and a water injection amount limit value, and determines a water injection amount set value through the water injection amount target value and the water injection amount limit value; the control system compares a measured value of the tower top water injection amount with the water injection amount set value, controls a water injection execution system to adjust the tower top water injection amount, and feeds back the water injection amount set value to a DCS or MES system, so that a worker can monitor the water injection amount set value and the measured value of the tower top water injection amount from the DCS or MES system. ； wherein, E is a weight, E is taken as 0~1; is a first water injection amount determined based on the overhead distillation amount; is a second water injection amount determined based on the saturated water injection amount; ​ ； ； wherein, , are a lower limit value and an upper limit value of the first water injection amount determined based on the overhead distillate amount, respectively, , are a lower limit value and an upper limit value of the second water injection amount determined based on the saturated water injection amount, respectively, is a current water injection amount measurement value, is a third water injection amount determined based on the overhead drain ion concentration, the overhead distillate amount = overhead oil return amount + overhead oil extraction amount + overhead non-condensable gas amount + overhead natural water amount.

2. The automatic control system for tower top water injection according to claim 1, characterized in that, ​ 3. The automatic control system for tower top water injection according to claim 1 or 2, characterized in that, ​ 4. The automatic control system for tower top water injection according to claim 1, characterized in that, ​ 5. A tower top water injection control method, which is implemented by using the automatic control system for tower top water injection according to any one of claims 1-4, characterized in that, ​ ​ ​ 6. A tower-top water injection control method according to claim 5, characterized in that, The method for determining the water injection amount set value in step (2) is: if the water injection amount target value is within the water injection amount limit value range, then the water injection amount target value is taken as the water injection amount set value; if the water injection amount target value is greater than the upper limit value of the water injection amount , then the upper limit value of the water injection amount is taken as the set value; if the water injection amount target value is less than the lower limit value of the water injection amount , then the lower limit value of the water injection amount is taken as the set value.

7. The tower-top water injection control method of claim 5, wherein The first water injection amount And the first water injection amount lower limit value The first water injection amount upper limit value The calculation formula is respectively: ； ； ； in, F T This represents the total distillate from the top of the column. A , A l , A h Let be the coefficient, and A l < A < A h ≤0.

15.

8. A tower-top water injection control method according to claim 7, characterized in that, A =6%， A l =3%， A h =10%。 9. The tower-top water injection control method of claim 5, wherein The second water injection amount And the second water injection amount lower limit value The second water injection amount upper limit value The calculation formula is respectively: ； ； ； wherein is the saturated water injection rate, B , B l , B h is a coefficient, and 1 B l < B < B h <2.

10. The tower-top water injection control method of claim 9, wherein B =1.25， B l =1.1， B h =1.5。 11. The tower-top water injection control method of claim 5, wherein The third water injection amount The calculation formula is: ； wherein, Qwater is the water injection rate, in barrels per day, calculated from the chloride ion concentration, Qwater is the water injection rate, in barrels per day, calculated from the ammonium bisulfide concentration; and The calculation formulas of the above are respectively: ； ； wherein, W 0 is the current water injection rate measurement, W n is the natural water rate at the top of the tower, C Cl is the chloride ion concentration of the effluent, in mg / L; C NH3+NH4+ is the ammonia nitrogen concentration of the effluent, in mg / L; C H2S is the sulfide concentration of the effluent, in mg / L; C and D is a coefficient, C = 30~160, the coefficient C is determined according to the chloride ion concentration of the effluent at the top of the tower detected by the online water quality multi-parameter measurement system, and the control C is greater than C Cl , D = 2.

Images