RU2065761C1 - Method of controlling quality of products from separation of petroleum mixtures by rectification process - Google Patents

Abstract

FIELD: petrochemical industry and petroleum processing. SUBSTANCE: invention relates, in particular, to methods of automatically controlling quality indexes of rectification column side-cut distillates, such as viscosity and flash point, and can be used when separating crude oil and mazut on atmospheric and vacuum primary distillation columns. Quality indexes of products are controlled by means of calculating determining indexes of products on the basis of process variables, whereas quality indexes of these products are calculated on the basis of calculated values of determining indexes of products. Flows' rates, temperature, level and pressure in apparatuses, and determining indexes of quality of products are controlled taking into account calculated quality indexes of these products. EFFECT: facilitated automatic process control. 1 dwg

Description

 The invention relates to methods for automatically controlling the quality indicators of the side shoulder straps of a distillation column (RK), for example, viscosity and flash point, and can be used in the petrochemical and oil refining industries, in particular when separating oil and fuel oil in atmospheric and vacuum columns of an oil primary distillation unit (AWT )

 A known method of controlling the quality of commercial products by calculating the limits of selection of fractions by their boundary boiling temperatures determined by indirect parameters [1] However, the known method does not provide a complete selection of distillation products of a given quality.

The closest in technical essence to the proposed method is a method of controlling the process of primary oil refining in a complex distillation column [2] by which the task for the quality of oil products, the values of the process parameters are supplied to the computing device to set the possible selection of distillation products and determine the required values of the controlled parameters according to the mathematical model of the control process, which is based on a system of linear equations formed from the function tional dependencies on calculation determining indicators products (e.g. kerosene for determining the flash point indicator is selected (t _Aux) and the boiling temperature of the 90% point). According to the formed process model, the calculated values of quality indicators are determined. The quality indicators of the obtained petroleum products are regulated by setting the necessary values of the temperature of the raw materials at the inlet to the column, the irrigation flow rate and the flow rate of superheated water vapor, determined by the computing unit.

 The known method also does not provide a complete selection of distillation products of a given quality. This is due to the incorrectness of the task of forming determining indicators (characteristic points of the true boiling temperature of the ICC) for the totality of quality indicators due to: 1) in the general case, there is no solution to the problem of simultaneously maintaining the set values of individual quality indicators due to their possible inconsistency; restrictions caused by characteristics, in particular (ITC), raw materials and technical characteristics of equipment.

 In addition, a (formalized numerical) assessment of the quality of a product based on a set of quality indicators, as a rule, is not performed. These circumstances cause major difficulties in the automatic control of product quality.

 The present invention solves the problem of increasing the yield of product streams of a given quality, selected in the form of side shoulder straps, by increasing the accuracy and efficiency of regulation.

 The essence of the invention lies in the fact that in a method of controlling the quality of products for the separation of oil mixtures by the rectification method, which includes regulating the quality indicators of products by calculating the technological parameters of the defining indicators of the products and calculating the quality indicators of these products from the calculated values of the defining indicators of the products, regulating the flow rate and temperature in devices, according to the invention regulate the level and pressure in the devices, the regulation of determining product exponent is performed with the correction of the calculated indicators of quality of these products. The characteristic points of the true boiling points of the products are used as determining indicators. For a given curve (ITC) of products, a multitude of product quality indicators (shoulder straps) can be uniquely determined, for example, flash point and solidification, viscosity. The inverse problem, namely the formation of the ITC product according to specified quality indicators, is generally incorrect. The formation of feedback loops on the quality of the products ultimately leads to the task of the invention.

 The drawing shows a schematic diagram of the implementation of the method.

 The control method is as follows. Signals about the power consumption in the distillation column (RK) and water vapor per cube of the column from sensors 1 and 2, pressure sensors 3 in the column, temperature sensors for top 4, power 5, bottom 6 and on side plates 7-9, selection sensors side 10-12 and head 13 shoulder straps enter the computing device 14, where the values of the characteristic points of the TIC are determined by calculation, that is, boiling temperatures 1% 5% 10% 50% 90% 95% and 99% of the distillation of products taken from above, from below and three side epaulettes of the column.

 Based on the calculated values of the characteristic points of the TEC, the signals are generated in the computing device 14, which are fed to the flow rate regulators for the steam supply to the cube of the column 15, the pressure of the top of the column 16, the selection of the head 17 and side 18-20 shoulder straps. The regulators 15-20 are supplied with the same signals as correcting signals generated in the computing device 21, the inputs of which are the calculated values of the characteristic points of the ITC flows. In the computing device 21 form the values of regulated quality indicators, which are fed to the corrective controllers 22-27. At the same regulators 22-27 set target values of regulated indicators of product quality. The outputs of the regulators 22-27 as tasks go to the regulators 15-20, respectively. Command signals from the output of the regulators 15-20 are sent to actuators installed on the lines for supplying water vapor to the cube of the column 28, for removing the vapor phase of the overhead 29, for supplying reflux 30, and for taking side straps 31-33, respectively. The power consumption is stabilized by a regulator 34, the output of which is supplied to an actuator 35 mounted on the power supply line. The stabilization of the level in the reflux capacity and the cube of the column is carried out using level controllers 36 and 38, respectively. Command signals from level controllers 36 and 38 are sent to actuators 37 and 39 installed on the lines for selecting the overhead and bottoms, respectively.

 An example of the implementation of the proposed method for a vacuum column installation ABT oil purpose.

D_i (i 1,4) отборы погонов в условных единицах (мас. на количество нефти, поступающей на установку АВТ).The calculation of the characteristic points of the TIC is carried out for the head shoulder strap (index i 1), three side shoulder straps (indices i 2,3,4) and the bottom residue (index i 5). Temperature calculation models t $\genfrac{}{}{0ex}{}{\text{k}}{\text{i}}$ ( ^° C) of the characteristic points of ITC K 10% and K 90% of the distillation of products are:
t $\genfrac{}{}{0ex}{}{\text{ten}}{\text{1}}$ = 1150.5 (D ₁ / G) -0.12 (PP _o ) +243.9;
t $\genfrac{}{}{0ex}{}{\text{90}}{\text{1}}$ = 1.031t ₂ + 0.13t ₃ -0.12 (PP _o ) +66.2;
t $\genfrac{}{}{0ex}{}{\text{ten}}{\text{2}}$ = 282.2 (D ₁ + D ₂ ) / G-0.13 (PP _o ) +321.8;
t $\genfrac{}{}{0ex}{}{\text{90}}{\text{2}}$ = 0.021t ₂ + 1.037t ₃ -0.13 (PP _o ) +105.6;
t $\genfrac{}{}{0ex}{}{\text{ten}}{\text{3}}$ = 1.09t $\genfrac{}{}{0ex}{}{\text{90}}{\text{2}}$ -94.66;
t $\genfrac{}{}{0ex}{}{\text{90}}{\text{3}}$ = 0.485t ₃ + 0.505t ₄ -0.14 (PP _o ) +147.7;
t $\genfrac{}{}{0ex}{}{\text{ten}}{\text{4}}$ = 0.338t ₃ -1.998W-0.145 (PP _o ) +348;
t $\genfrac{}{}{0ex}{}{\text{90}}{\text{4}}$ = 0.44t ₃ -1.337W-0.145 (PP _o ) +387.39;
t $\genfrac{}{}{0ex}{}{\text{ten}}{\text{5}}$ = 1,087t $\genfrac{}{}{0ex}{}{\text{90}}{\text{4}}$ -76.184;
D ₁ = (1.11-0.0397t ₁ + 0.000342t $\genfrac{}{}{0ex}{}{\text{2}}{\text{1}}$ ) × F / 100;
GG _F + G _otg ;
G _F (-1.85 + -0.158 Z _F + 0.0065 t _F 0.00165 P) x F;
G _otg (-0.8360 + 0.1767 • Z _bottom + 0.0026 t _F 0.00005 x p) x W;

D _i (i 1,4) the selection of shoulder straps in arbitrary units (wt. On the amount of oil supplied to the installation ABT).

t _i (i 1,5) the temperature of the top of the column, on the plates of selection of side shoulder straps and the bottom of the column ^o C;
P, P < _o current and nominal (calculated) value of the residual pressure of the top of the column, mm Hg

t _F column supply temperature, ^o C;
Z _F , Z _bottom flow rate of water vapor in the feed and cube columns in arbitrary units;
F power consumption in arbitrary units.

t $\genfrac{}{}{0ex}{}{\text{всп}}{\text{2}}$ = -40+0,65t $\genfrac{}{}{0ex}{}{\text{10}}{\text{2}}$ ;

t $\genfrac{}{}{0ex}{}{\text{всп}}{\text{3}}$ = -35+0,66t $\genfrac{}{}{0ex}{}{\text{10}}{\text{3}}$ ;

t $\genfrac{}{}{0ex}{}{\text{всп}}{\text{4}}$ = -30+0,665t $\genfrac{}{}{0ex}{}{\text{10}}{\text{4}}$
t $\genfrac{}{}{0ex}{}{\text{всп}}{\text{5}}$ = -28+0,67t $\genfrac{}{}{0ex}{}{\text{10}}{\text{5}}$
Выбор вида и значений регламентируемых показателей осуществляют по показателям качества соответствующих погонов и режимным параметрам с учетом их приоритетов и ограничений по технологическому регламенту. В данном случае это сделано экспертным путем. Модели для расчета регламентируемых параметров качества имеют вид:

ξ₂=P_зд;
ξ₃=t_1/

β₁=0,2÷0,3

β₂=0,4÷0,6

β₃=0,2÷0,3
Индексы "зд" и "мах" обозначают заданное и максимальное значения соответствующих параметров.Models for calculating the quality of shoulder straps, namely, viscosity ν _i (in centistokes) and flash point t $\genfrac{}{}{0ex}{}{\text{aux}}{\text{i}}$ ( ^° C) ( ^o C) have the form:

t $\genfrac{}{}{0ex}{}{\text{aux}}{\text{2}}$ = -40 + 0.65t $\genfrac{}{}{0ex}{}{\text{ten}}{\text{2}}$ ;

t $\genfrac{}{}{0ex}{}{\text{aux}}{\text{3}}$ = -35 + 0.66t $\genfrac{}{}{0ex}{}{\text{ten}}{\text{3}}$ ;

t $\genfrac{}{}{0ex}{}{\text{aux}}{\text{4}}$ = -30 + 0.665t $\genfrac{}{}{0ex}{}{\text{ten}}{\text{4}}$
t $\genfrac{}{}{0ex}{}{\text{aux}}{\text{5}}$ = -28 + 0.67t $\genfrac{}{}{0ex}{}{\text{ten}}{\text{5}}$
The choice of the type and values of regulated indicators is carried out according to the quality indicators of the relevant epaulettes and operational parameters, taking into account their priorities and restrictions on technological regulations. In this case, this is done by an expert. Models for calculating regulated quality parameters are:

ξ ₂ = P _health ;
ξ ₃ = t _{1 /}

β ₁ = 0.2 ÷ 0.3

β ₂ = 0.4 ÷ 0.6

β ₃ = 0.2 ÷ 0.3
The indices "zd" and "max" indicate the set and maximum values of the corresponding parameters.

The found dependencies for determining the characteristic points of the TEC shoulder straps t $\genfrac{}{}{0ex}{}{\text{k}}{\text{i}}$ , viscosity ν _i , flash point t $\genfrac{}{}{0ex}{}{\text{aux}}{\text{i}}$ and regulated product quality parameters ξ _i allow implementing the proposed method of product quality management on the basis of the regulating microcontroller R-100 in accordance with the above schematic diagram in the petrochemical and oil refining industries, in particular when separating oil and fuel oil in atmospheric and vacuum columns.

Using the present invention will allow us to solve the problem of continuous automatic control of distillation columns with side shoulder straps on the basis of the aggregate quality indicators of product flows. This provides:
1) improving the accuracy of regulation of quality indicators;
2) increasing the efficiency (reducing regulation time) of management processes;
3) the possibility of a direct impact on the technological parameters through the set values of quality indicators.

Information sources:
1. Oil, gas and petrochemicals abroad, 1988, N 4, p. 131-134.

 2. A.S. USSR N 1178461, class In 01 D 3/42, 1985 (prototype)

Claims (1)

 A method for controlling the quality of products of separation of oil mixtures by a rectification method, which includes regulating the quality indicators of products by calculating the determining parameters of the products according to the technological parameters and calculating the quality indicators of these products from the calculated values of the determining parameters of the products, controlling the flow rate and temperature in the apparatus, characterized in that they control the level and pressure in the apparatus, the regulation of determining indicators of products is carried out with correction of the calculated indicators of quality of these products.