JP2539691B2 - Multi-branch control method for gas-liquid mixed phase fluid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a gas in a heating furnace for a gas-liquid mixed phase fluid used in a hydrodesulfurization apparatus, a hydrorefining apparatus, etc. installed in an oil refining plant or the like. The present invention relates to a multi-branch control method for a liquid multiphase fluid.

[Problems to be Solved by Prior Art and Invention]

In petroleum refining factories and the like, a large number of devices such as hydrodesulfurization devices and hydrorefining devices that process petroleum distillates containing hydrocarbons as main components with hydrogen are installed.

In such a device, usually, a heating furnace is installed in front of the reaction tower, and a gas-liquid mixed phase fluid consisting of a petroleum fraction containing hydrocarbon as a main component and a gas such as hydrogen is heated to the reaction temperature in the heating furnace. The temperature is rising.

When heating a fluid in a heating furnace, the flow path of the fluid may be branched into multiple channels inside the heating furnace due to restrictions such as the size of the heating pipe, but the number of branch channels is three. In the above case, there is a risk that a drift may occur which may lead to damage of the heating pipe forming the flow path.

Particularly, in the case of a gas-liquid mixed phase fluid, it is necessary to control a fluid in which a gas and a liquid having extremely different physical properties are mixed, so that the control method is difficult.

For this reason, when it is necessary to perform multi-branch control of the gas-liquid mixed phase fluid, a method of branching and controlling the gas and the liquid separately, and then mixing and heating is usually adopted.

However, in this method, it is necessary to control the branched gas and the liquid separately, and the control method tends to be complicated.

On the other hand, a method of branching a gas-liquid mixed-phase fluid from one flow path to two flow paths is also conventionally known. In this method, the gas-liquid multiphase fluid tends to flow relatively uniformly, and the risk of nonuniform flow is small.

Therefore, when it is necessary to branch the gas-liquid mixed phase fluid, a so-called tournament system is often used in which one flow path is branched into two flow paths and each of the branched flow paths is further branched into two flow paths.

However, even in this method, it is not sufficient to prevent uneven flow, and it is necessary to provide a certain distance or more from the location where one flow path is branched into two flow paths to the location where each flow path is further branched into two flow paths. . Further, the tournament method has a problem that the number of flow paths can be limited to a specific number of flow paths such as two, four, and eight.

The present invention has been proposed in order to solve the above problems, in which a gas-liquid mixed phase fluid of one flow path is branched into at least three flow paths, heated in a heating furnace, and then integrated into one flow path. In the multi-branch control method for fluids, a relatively simple means is used to prevent uneven flow in the branch flow passage or to quickly eliminate the uneven flow even when the uneven flow occurs, and to provide the branch flow passage in the heating furnace. It is an object of the present invention to provide a multi-branching control method for a gas-liquid mixed phase fluid, which prevents the heating tube constituting the above from being destroyed and does not occupy a large installation area.

[Means for solving the problem]

As a result of various studies to solve the above-mentioned problems, the inventors of the present invention have found that the occurrence of drift occurs largely depending on the liquid supply amount, the pressure difference between before and after branching of the flow path, and the occurrence of drift occurs. Focusing on the fact that it can be detected by monitoring the temperature deviation of the heating furnace outlet of each branch flow channel, we have found that multi-branch control of a gas-liquid mixed phase fluid can be performed by a combination of specific control methods, and have completed the present invention.

That is, the present invention is a multi-branch of a gas-liquid multi-phase fluid used for hydrotreating petroleum, in which a gas-liquid multi-phase fluid of one flow path is branched into at least three flow paths, heated in a heating furnace, and then integrated into one flow path. In the control method, the supply amount of the liquid, the differential pressure between before and after the branch of the flow channel and each branch flow channel temperature at the heating furnace outlet are respectively measured, and when the differential pressure is within a set range, Based on the liquid supply amount, collectively control each branch flow path control valve installed on the heating furnace inlet side of each branch flow path, and when the differential pressure fluctuates outside the set range, Based on a collective control of the respective branch flow path control valve based on, when the temperature deviation between any one flow path of each branch flow path and the other flow path other than the one flow path exceeds a set value , Each of the branch passage control valves is independently controlled (first invention ), When the branch flow passage control valves are collectively controlled based on the liquid supply amount or the flow passage differential pressure or individually controlled, the operation amount given to each branch flow passage control valve is adjusted to the operation amount given to each branch flow passage control valve. The operation amount determined on the basis of the heating furnace outlet temperature is added as a weight to control each of the branch flow passage control valves (second invention).

[Action]

In the first aspect of the present invention, the gas-liquid mixed-phase fluid in one flow path is branched into at least three flow paths, and is heated in the heating furnace via the branch flow path control valves respectively installed on the heating furnace inlet side of each branch flow path. After that, the branch channels are integrated into one channel.

On the other hand, the supply amount of the liquid that forms the gas-liquid mixed phase fluid, the pressure difference between the flow path before branching and after integration (flow path differential pressure), and the temperature of each branch flow path at the heating furnace outlet are measured. .

Then, when the flow path differential pressure is within the set range, each branch flow path control valve is collectively controlled based on the liquid supply amount (hereinafter, this control is referred to as “liquid supply amount control”).

The controller that controls the liquid supply amount inputs a function of the liquid supply amount as a target value and outputs the same operation amount to each branch flow passage control valve. As a result, the control valves are collectively controlled, and drift due to fluctuations in the liquid supply amount is prevented.

Here, the function of the liquid supply amount is determined, for example, by performing a simulation in consideration of the physical properties of the liquid and gas, equipment, operating conditions, etc., but normally, it is represented by a linear function with the liquid supply amount as a variable. To be done.

By the way, if the pressure difference between the flow path before branching and the flow path after integration is small, uneven flow is likely to occur, and if it is too large, it affects the process.

Therefore, when the flow path differential pressure fluctuates outside the set range, each branch flow path control valve is collectively controlled based on the flow path differential pressure (hereinafter, this control is referred to as "flow path differential pressure control"). ).

That is, when the flow path differential pressure changes from within the desired setting range to outside the setting range, the control of each branch flow path control valve is switched from the control based on the liquid supply amount to the control based on the flow path differential pressure. . As a result, each branch flow path control valve is controlled so that the flow path differential pressure becomes a preset value, and it is possible to prevent the occurrence of the drift due to the flow path differential pressure, which causes the drift. However, the drift is eliminated promptly.

The setting range of the flow path differential pressure is determined, for example, by performing a simulation in consideration of the physical properties of liquid and gas, equipment, operating conditions, and the like.

Furthermore, when a nonuniform flow occurs, the temperature difference between the heating furnace outlet temperatures of the respective branch flow paths becomes large, and the temperature deviation increases.

Therefore, the temperature deviation is monitored, and when the temperature deviation exceeds the set value, each branch flow path control valve is independently controlled (hereinafter, this control is referred to as "independent control").

In this case, the heating furnace outlet temperature of one flow passage and the temperatures of the other flow passages other than the flow passage are compared for each branch flow passage.

When the control of each branch flow passage control valve is collectively controlled based on the fluid supply amount or the flow passage differential pressure, any one of the above comparison results (that is, temperature deviation) for each flow passage is When the set value is exceeded, the control of each branch flow path control valve is switched from the collective control based on the fluid supply amount and the flow path differential pressure to the control of each branch flow path control valve alone.

Here, each of the temperature deviations is generally the difference between the heating furnace outlet temperature of one of the branch passages and the heating furnace outlet temperature average value of the other passages other than the one passage. Represented by The set value of the temperature deviation is determined by, for example, performing a simulation in consideration of the physical properties of liquid and gas, equipment, operating conditions, and the like.

As a result, even if uneven flow occurs, it is possible to quickly eliminate the uneven flow by controlling each branch flow path control valve independently.

Therefore, according to the first aspect of the invention, even if the flow of the liquid is changed or the pressure difference before and after the branching of the flow path is changed, each of the factors causing the non-uniform flow (liquid The flow rate is controlled according to the fluctuation of the supply amount and the differential pressure of the flow path, and when the drift occurs, the control is immediately switched to the independent control, so that the prevention of the drift can be realized, and even if the drift occurs, it can be promptly resolved. It

As described above, in the normal multi-branch control, in the liquid supply amount control and the flow channel differential pressure control, by collectively controlling each branch flow channel control valve, a control with a good balance as a whole control system. When a deviation occurs due to monitoring of the temperature deviation and switching to the independent control, the deviation can be detected early and the deviation can be promptly eliminated.

By the way, for example, the burning situation of the burner in the heating furnace,
Depending on other equipment, operating conditions, etc., the temperature difference of the heating furnace outlet temperature of the branch flow path may be different when the branch flow path control valves are collectively controlled by the liquid supply amount control and the flow path differential pressure control. It can occur.

Therefore, in the second aspect of the present invention, the heating furnace of each branch flow path is controlled when the branch flow path control valves are collectively controlled based on the liquid supply amount or the flow path differential pressure, or individually controlled. Control is performed with the outlet temperature taken into consideration.

That is, in the second invention, in the liquid supply amount control and the flow path differential pressure control of the first invention,
The operation amount (bias value) determined based on the heating furnace outlet temperature of each branch flow path is added as a weight.

Therefore, when variations occur in the heating furnace outlet temperature of each branch channel due to equipment, operating conditions, etc., each branch channel temperature and the average value of each branch channel temperature, etc. The bias value is added to the manipulated variable during the liquid supply amount control and the flow path differential pressure control.

Note that each of the bias values is represented as a function of the manipulated variable such that each flow path outlet temperature converges to the average value of the heating furnace exit temperature of each branch flow path, and the function is a physical property of liquid and gas, It is determined, for example, by performing a simulation in consideration of equipment, operating conditions, and the like.

Further, the control of adding the bias value as a weight can be continuously performed even after switching to the independent control. Also in this case, each branch flow passage control valve is controlled so as to converge to the average value of the heating furnace outlet temperature of each branch flow passage.
That is, when the control is switched to the independent control due to occurrence of drift, etc., each control valve may cancel the drift by manual operation, or may automatically cancel the bias by controlling the bias value as a weight.

As described above, in the second invention, when the liquid supply amount control and the flow path differential pressure control in the first invention are collectively controlled or independently controlled, the heating is performed between the branch flow paths. When there are variations in the furnace outlet temperature, the individual manipulated variables based on the heating furnace outlet temperature are added to the manipulated variables given to each branch passage control valve.

Therefore, for example, when there are a large number of branch channels, even if a drift is likely to occur in combination due to fluctuations in the liquid supply amount and the flow path differential pressure, the drift tends to disappear rapidly. As a result, highly reliable prevention of nonuniform flow is achieved, or even if the nonuniform flow occurs, the nonuniform flow is promptly eliminated.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples. These are listed for illustrative purposes only and the invention is not limited to these examples.

FIG. 1 illustrates a flow system diagram of the present invention in a kerosene hydrodesulfurization apparatus.

The flow rate of the undesulfurized kerosene boosted by the raw material pump 1 is controlled by the flow rate control valve 2, the temperature is raised by the heat exchanger 3, and then the gas is boosted by the compressors 4 and 4 ′ and mixed with a gas containing hydrogen as a main component. To be done.

The mixed gas-liquid mixed phase fluid is further heated by the heat exchanger 5 and then branched into four flow paths l ₁ , l ₂ , l ₃ , l ₄ to control valves 6, 7, 8, 9 respectively. Then, the temperature is raised in the heating furnace 11.

The gas-liquid mixed phase fluid whose temperature has been raised in the heating furnace 11 is integrated into one flow path, and then hydrodesulfurization reaction is carried out in the reaction tower 12, and is sent to the high temperature separation tank 13 via the heat exchanger 5.

After that, it is processed by the flow of a general kerosene hydrodesulfurization device.

That is, the gas such as hydrogen separated in the high temperature separation tank 13 is sent to the compressor 4 through the cooler 14, the condenser 15 and the low temperature separation tank 16, and the desulfurization kerosene separated in the high temperature separation tank 13 is a valve. It is sent to the next process via 17.

FIG. 2 shows a control system diagram of the present invention in the flow of the kerosene hydrodesulfurization apparatus shown in FIG.

The undesulfurized kerosene whose flow rate is controlled by the flow rate control valve 2 based on the signal indicating the liquid supply amount of the orifice flow meter 21 is mixed with a gas containing hydrogen as a main component in the gas-liquid mixing section 22 to form a gas-liquid mixed phase. Become a fluid. This gas-liquid multiphase fluid is
Via the pressure detector 23, branched into four flow paths l _{1 to} l ₄ , each branch flow path control valve, that is, a control valve 6, 7 installed in each branch flow path.
It is heated in the heating furnace 11 through 8 and 9.

The gas-liquid mixed-phase fluids exiting the heating furnace 11 are temperature detectors, respectively.
After being integrated into one flow path via 25, 26, 27, 28, pressure detector 2
It is sent to the next process via 4.

Further, the pressure detected by the pressure detector 23,24 is a pressure indicator 29,30, and the temperature detected by the temperature detector 25,26,27,28 is a temperature indicator 31,32, Displayed at 33 and 34 respectively.

The control valves 6 to 9 can individually control the opening degree, but are normally controlled to the same opening degree by the host controller 37.

That is, an output signal indicating the liquid supply amount from the flow rate control valve controller 35 based on the signal from the orifice flow meter 21 is input to the arithmetic circuit 36, and based on this arithmetic result, the host controller 37 controls the control valve 6 The liquid supply amount control is performed by controlling the opening degrees of 9 to 9.

In this embodiment, the arithmetic operation of the arithmetic circuit 36 is performed based on the following linear expression.

Opening (%) = A x kerosene supply (kl / H) + B A: Constant set according to raw material, equipment, operating conditions, etc. (for example, A = 0.151) B: Constant set according to raw material, equipment, operating conditions, etc. (For example, B = 28) Here, the constants A and B are determined by a known method such as simulation.

On the other hand, the difference between the inlet pressure p _i and the outlet pressure p _o of the heating furnace 11 (p _i −
If p _o ) is outside the setting range, the control switch 38
Is activated, and the same opening degree control (liquid supply amount control) based on the arithmetic circuit 36 is switched to the same opening degree control (flow path differential pressure control) based on the differential pressure (p _i −p _o ).

That is, the pressure p _i at the inlet of the heating furnace 11 is measured by the pressure detector 23, and the pressure at the outlet p _o is measured by the pressure detector 24, and the differential pressure (p _i −p _o ) is within a certain range, for example, 3 ~ 5k
When it goes out of the range of g / cm ^2, the control switch 38 switches,
Based on the output signal from the differential pressure controller 39, the differential pressure (p _i −
The upper controller 37 adjusts the same opening so that p _o ) becomes a constant value, for example, 3 kg / cm ² or 5 kg / cm ² .

As described above, the control of each of the control valves 6 to 9 causes the differential pressure (p _i −
When the switch is switched to the same opening control based on p _o ), that is, the flow path differential pressure control, an alarm is automatically issued, and the operator confirms and changes the differential pressure range to switch to differential pressure control and differential pressure control. It is possible to take necessary measures such as changing the setting value of.

Temperature detectors 25, 26, 27, 28 are installed at the outlets of the heating furnace 11 in each of the branched flow paths l _{1 to} l ₄ in order to detect and correct the occurrence of uneven flow or malfunction of instruments etc. at an early stage. , Always, the deviation between the outlet temperature of the heating furnace 11 of one branch flow path among the branch flow paths l _{1 to} l ₄ and the outlet temperature of the heating furnace 11 of the branch flow path other than the one branch flow path We are monitoring each. Each temperature deviation is calculated by the arithmetic circuit
It is calculated by 45, the calculation formula is the physical properties of liquid and gas,
Although it varies depending on equipment, operating conditions, etc., it is usually calculated based on the following calculation formula, for example.

dT ₁ = T ₁ − (T ₂ + T ₃ + T ₄ ) / 3 dT ₂ = T ₂ − (T ₃ + T ₄ + T ₁ ) / 3 dT ₃ = T ₃ − (T ₄ + T ₁ + T ₂ ) / 3 dT _{4 = T 4 - (T 1 +} T 2 + T 3) / 3 T 1, T 2, T 3, T 4: outlet temperature of the heating furnace 11 of the branch paths l ₁ to l _4.

_{dT 1, dT 2, dT 3} , dT 4: each deviation dT outlet temperature of the heating circuit 11 in the branch paths l ₁ to l _4.

Any of the temperature deviations dT _{1 to} dT ₄ is within a certain range, for example ± 10 ° C
When it exceeds, the same opening degree control (liquid supply amount control or flow path differential pressure control) by the host controller 37 is automatically stopped, and each control valve 6-9 is switched to a single control.

In this case, the opening degree of each control valve 6-9 is independently controlled by each control valve controller 41, 42, 43, 44.

By the way, in the same degree of opening control by the host controller 37, variations in the outlet temperatures T _{1 to} T ₄ of the heating furnace 11 of the respective branch flow paths l _{1 to} l ₄ due to the structure of the equipment or the combustion state of the burner, etc. May occur.

Therefore, in the second aspect of the invention, the uniformizing control of the outlet temperature of the heating furnace is incorporated for the purpose of preventing the variation of the outlet temperatures T _{1 to} T ₄ .

That is, for example, the average temperature T _ave outlet temperature T ₁ through T ₄ of the heating furnace 11 of the branch paths _{l 1 ~l 4 ((T 1} + T 2 + T 3 + T 4) / 4)
As a set value, and as shown in FIG. 3, each branch flow path l _{1 to} l ₄
Temperature controller 46 with outlet temperatures T _{1 to} T ₄ of
The biases exemplified in the following equations are applied to the control valve controllers 41 to 44 by 49, and the opening degrees of the control valves 6 to 9 are finely adjusted.

Bias value = [Temperature controller output (%)-50] x 0.1 The above temperature controller output is the output of the temperature controller that makes the valve opening of each temperature controller 46, 47, 48, 49 100%. It is expressed as a percentage as a standard.

Also, in the heating furnace, the temperature of the tube surface of each heating tube that constitutes the dispersion channel is detected, and the temperature deviation between each heating tube and other heating tubes (that is, the tube surface temperature deviation between each branch channel) is calculated. By monitoring, if the temperature deviation exceeds the set value, an alarm is issued and a function to notify the abnormality is also installed.

According to the above method, for kerosene, a union type hydrodesulfurization system (design throughput of 50,000 barrels /
The test operation was carried out in the range of the treated amount of 13,000 barrel / day to 50,000 barrel / day.

In this test operation, the coefficients of the above-described linear equation in the calculation of the calculation circuit 36 were set to A = 0.151 and B = 28. Also,
In this test operation, the same opening control by the host controller 37 was performed so that the pressure difference (P _i −P _o ) between the inlet pressure P _i and the outlet pressure P _{o of} the heating furnace 11 was 3 kg / cm ^2. Do each branch flow path
Deviations of the outlet temperatures of the heating furnace 11 of l _{1 to} l ₄ dT _{1 to} dT ₄ are ± 10 ° C
When it exceeded, the liquid supply amount control or the flow path differential pressure control described above was stopped, and the individual control valves 6 to 9 were individually controlled.

As a result, it was possible to prevent the occurrence of non-uniform flow even though the flow path had a structure in which one flow path was branched into four flow paths l _{1 to} l ₄ .

〔The invention's effect〕

According to the first aspect of the present invention, even if the flow rate tends to cause a drift due to the change in each element of the liquid supply amount or the pressure difference before and after the branching of the flow path, the element that causes the drift (the liquid supply amount). Fluctuation, flow path differential pressure), and if deviation occurs, it can be immediately switched to independent control.
The prevention of the nonuniform flow is realized, and even if the nonuniform flow occurs, it is promptly resolved.

Further, in the second invention, when the liquid supply amount control and the flow path differential pressure control in the first invention are collectively controlled, the heating furnace outlet temperature varies due to the combustion state of the burner of the heating furnace and the like. Even if it changes so as to occur, it is decided to add the individual operation amount based on the heating furnace outlet temperature to the operation amount given to each branch flow passage control valve. Even when the mixed flow is likely to occur in a complex manner, the uneven flow is rapidly eliminated to achieve highly reliable prevention of uneven flow, or even if the uneven flow occurs, the uneven flow is quickly eliminated. Done.

Therefore, the heating tube is not damaged and the reliability of the control system is improved.

Moreover, since the control method of the present invention is not a method of separately controlling the gas and the liquid separately, and then mixing and heating, the control method does not become complicated and a highly reliable and simple control system can be realized. .

Further, since there is no need to adopt a so-called tournament system, it is not necessary to provide a certain distance or more from the location where one flow path is branched into two flow paths to the location where each branch flow path is further branched into two flow paths. Therefore, since the installation area of the entire system does not become vast, it is possible to effectively utilize the site area. Also, like the tournament method, the number of channels is 2, 4, 8, etc. The number of branch channels can be arbitrarily selected without the problem that only the number can be set.

[Brief description of drawings]

FIG. 1 is a flow system diagram of the present invention in a kerosene hydrodesulfurization device, FIG. 2 is a control system diagram of the first invention in the flow of a kerosene hydrodesulfurization device shown in FIG. 1, and FIG. 3 is the same second invention. It is a control system diagram of. 11 …… Heating furnace 6,7,8,9 …… Branch flow control valve l ₁ , l ₂ , l ₃ , l ₄ …… Branch flow

Claims (2)

(57) [Claims] 1. A gas-liquid mixed phase fluid in one flow path is branched into at least three flow paths, heated in a heating furnace, and then integrated into one flow path.
In a multi-branch control method of a gas-liquid mixed phase fluid used for petroleum hydrotreating, the supply amount of the liquid, the differential pressure between before and after the branch of the flow channel, and the temperature of each branch flow channel at the heating furnace outlet are set. Each measured, when the differential pressure is within the set range, collectively control each branch flow path control valve respectively installed on the heating furnace inlet side of each branch flow path based on the liquid supply amount, When the differential pressure fluctuates outside the set range, the branch flow passage control valves are collectively controlled based on the differential pressure, and any one of the branch flow passages and the one flow passage are connected to each other. A multi-branch control method for a gas-liquid mixed phase fluid, wherein each of the branch flow channel control valves is individually controlled when the temperature deviation from the other flow channels except the flow channel exceeds a set value. 2. When the branch flow path control valves are collectively controlled or individually controlled based on the liquid supply amount or the flow path differential pressure, each branch flow flow is controlled by the operation amount given to each branch flow path control valve. The multi-branch control method for a gas-liquid mixed phase fluid according to claim 1, wherein each branch flow passage control valve is controlled by adding an operation amount determined based on the outlet temperature of the heating furnace of the passage as a weight.