A method and device for calculating the water level of a steam drum in hot and cold working conditions

Abstract

The present invention discloses a method and device for calculating the drum water level in both cold and hot operating conditions. By establishing a calculation formula for the drum water level in the cold state and a method for determining whether the two conditions are hot or cold, the method automatically switches between the cold and hot state calculation formulas. This avoids the inaccurate measurement of differential water level gauges before the drum enters the hot state, facilitating full-time monitoring of the drum water level by unit operators.

Description

Technical Field

[0001] The invention relates to a method and device for calculating the water level of a steam drum in both cold and hot working conditions, and belongs to the field of thermal power generation. Background Art

[0002] Drum boilers commonly use differential pressure water level gauges to measure drum water level. The results are used for drum water level control and protection, and their accuracy is crucial to safe and stable unit operation. The differential pressure water level gauge utilizes the principles of hydrostatics to convert the water level into a differential pressure. A differential pressure transmitter then converts the differential pressure signal into a 4-20 mA signal and transmits it to the DCS control system. The DCS uses the corresponding relationship between differential pressure and water level to reverse-calculate the drum water level. However, due to the influence of drum pressure on water and steam density, the relationship between differential pressure and water level is not fixed.

[0003] The water level calculated during the drum filling process or before the boiler is ignited is inaccurate. This is because the water in the drum is subcooled, and the gas inside the drum is not saturated steam, but air. Therefore, when the drum is cold, operators often need to be on-site and use a two-color water level gauge or electric contact water level gauge to determine the water level. This is very inconvenient and hinders real-time monitoring of the drum water level. Summary of the Invention

[0004] The present invention provides a solution to the problem disclosed in the background technology.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for calculating the water level of a steam drum under both hot and cold working conditions:

[0007] Measure the differential pressure between the balance container and the sampling port under the drum, input the differential pressure into the pre-built cold drum water level calculation model, and the cold drum water level calculation model outputs the drum water level under cold working conditions;

[0008] Measure the differential pressure between the balance container and the sampling port under the drum, input the differential pressure into the pre-built hot drum water level calculation model, and the hot drum water level calculation model outputs the drum water level under hot working conditions;

[0009] Measure the drum lower wall temperature and drum pressure, obtain the saturation temperature corresponding to the drum pressure through the drum pressure, compare the drum lower wall temperature and the saturation temperature corresponding to the drum pressure, if the drum lower wall temperature is higher than the saturation temperature corresponding to the drum pressure, select the drum water level under hot conditions; otherwise, select the drum water level under cold conditions.

[0010] Furthermore, the formula of the cold drum water level calculation model is:

[0011]

[0012] Where: H is the drum water level, L is the reference water column height, ρ c is the average density of the reference water column, ρ w is the density of water in the drum, ρ a is the air density in the drum, and ΔP is the differential pressure between the balance container and the sampling port below the drum.

[0013] Furthermore, the formula of the hot drum water level calculation model is:

[0014]

[0015] Where: H is the drum water level, L is the reference water column height, ρ c is the average density of the reference water column, ρ w is the saturated water density of the drum, ρ s is the saturated steam density of the drum, and ΔP is the differential pressure between the balance container and the sampling port below the drum.

[0016] Furthermore, the drum water level is calculated using a cold drum water level calculation model before the drum is filled with water or the boiler is not ignited.

[0017] Accordingly, a cold and hot dual-state drum water level calculation device includes:

[0018] Differential pressure transmitter: used to measure the differential pressure between the balance container and the sampling port under the steam drum;

[0019] Cold drum water level calculation module: used to calculate the drum water level under cold working conditions through differential pressure;

[0020] Hot drum water level calculation module: used to calculate the drum water level under hot working conditions through differential pressure;

[0021] Temperature and pressure measurement module: used to measure the lower wall temperature and pressure of the steam drum;

[0022] Hot and cold state switching module: obtain the saturation temperature corresponding to the drum pressure through the drum pressure, compare the drum lower wall temperature with the saturation temperature corresponding to the drum pressure, and if the drum lower wall temperature is higher than the saturation temperature corresponding to the drum pressure, select the drum water level under the hot state; otherwise, select the drum water level under the cold state.

[0023] Furthermore, the formula of the cold drum water level calculation module is:

[0024]

[0025] Where: H is the drum water level, L is the reference water column height, ρ c is the average density of the reference water column, ρ w is the density of water in the drum, ρ ais the air density in the drum, and ΔP is the differential pressure between the balance container and the sampling port below the drum.

[0026] Furthermore, the formula of the hot drum water level calculation module is:

[0027]

[0028] Where: H is the drum water level, L is the reference water column height, ρ c is the average density of the reference water column, ρ w is the saturated water density of the drum, ρ s is the saturated steam density of the drum, and ΔP is the differential pressure between the balance container and the sampling port below the drum.

[0029] Furthermore, it also includes a pulse module: used to reduce water level disturbance during the switching between hot and cold states and ensure automatic control of the water level.

[0030] Accordingly, a computer-readable storage medium stores one or more programs: the one or more programs include instructions, which, when executed by a computing device, cause the computing device to perform any one of the methods described above.

[0031] Accordingly, a computing device includes:

[0032] One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing any of the methods described above.

[0033] The present invention achieves the beneficial effect of automatically switching between cold and hot state calculation formulas by establishing a cold drum water level calculation formula and a method for determining whether the drum is hot or cold. This avoids the inaccurate measurement of differential water level gauges before the drum enters the hot state, making it easier for unit operators to monitor the drum water level throughout the entire process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0036] like Figure 1 As shown, a method for calculating the water level of a cold and hot dual-working state drum of the present invention comprises the following steps:

[0037] Step S1: Establish a calculation formula for the drum water level in a cold state, and use this formula to calculate the drum water level before the drum is filled with water or the boiler is not ignited;

[0038] The calculation of the drum water level in the cold state in step S1 also requires compensation. The density of water and air in the drum is obtained according to the drum pressure and temperature, and then the drum water level is calculated. The corresponding formula is as follows:

[0039]

[0040] Where: H is the drum water level, L is the reference water column height, ρ c is the average density of the reference water column, ρ w is the density of water in the drum, ρ a is the air density in the drum, and ΔP is the differential pressure between the balance container and the sampling port below the drum.

[0041] Step S2: Establish a method for judging hot and cold states, and realize automatic switching of the calculation formulas for hot and cold states;

[0042] The specific method for judging the hot and cold states in step S2 is to obtain the saturation temperature under the pressure according to the drum pressure (which can be obtained by looking up the enthalpy-temperature table, and each pressure corresponds to a saturation temperature), and compare the lower wall temperature of the drum with the saturation temperature. If it is higher than the saturation temperature, it is judged to have entered the hot state. Otherwise, it is judged to be in the cold state. Regardless of the state, the hot and cold drum water level calculation modules are always in real-time calculation, and the calculation results are sent to the switching module. The switching module judges the cold / hot state results and selects the output of the hot or cold state calculation results according to the cold / hot state results. When switching between hot and cold states, a pulse will be triggered, and the first-order inertia link will be enabled within the pulse time. The output of the switching module will go through this link, thereby reducing the water level disturbance during the switching process and ensuring automatic control of the water level. In addition, the pulse time is a variable value, which is positively correlated with the absolute value of the deviation output by the cold and hot drum water level calculation modules to ensure a suitable lag time during the switching process between hot and cold states.

[0043] Step S3: The calculation formula of the drum water level in the hot state is:

[0044]

[0045] Where: H is the drum water level, L is the reference water column height, ρ c is the average density of the reference water column, ρ w is the saturated water density of the drum, ρ s is the saturated steam density of the drum, and ΔP is the differential pressure between the balance container and the sampling port below the drum.

[0046] Accordingly, the present invention provides a cold and hot dual-state drum water level calculation device, comprising:

[0047] Differential pressure transmitter: used to measure the differential pressure between the balance container and the sampling port under the steam drum;

[0048] Cold drum water level calculation module: used to calculate the drum water level under cold working conditions through differential pressure;

[0049] Hot drum water level calculation module: used to calculate the drum water level under hot working conditions through differential pressure;

[0050] Temperature and pressure measurement module: used to measure the lower wall temperature and pressure of the steam drum;

[0051] Hot and cold state switching module: obtains the saturation temperature corresponding to the drum pressure through the drum pressure, compares the drum lower wall temperature with the saturation temperature corresponding to the drum pressure, and selects the drum water level under the hot state if the drum lower wall temperature is higher than the saturation temperature corresponding to the drum pressure; otherwise, selects the drum water level under the cold state;

[0052] Pulse module: used to reduce water level disturbance during hot and cold state switching and ensure automatic control of water level.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

[0054] A computer-readable storage medium storing one or more programs, wherein the one or more programs include instructions, which, when executed by a computing device, enable the computing device to execute a method for calculating a cold and hot dual-state steam drum water level.

[0055] A computing device includes one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing a method for calculating the water level of a cold and hot dual-state steam drum.

[0056] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0057] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0058] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0059] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0060] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A method for calculating the water level of a hot and cold dual-state drum, characterized by: Measure the differential pressure between the balance container and the sampling port under the drum, input the differential pressure into the pre-built cold drum water level calculation model, and the cold drum water level calculation model outputs the drum water level under cold working conditions; Measure the differential pressure between the balance container and the sampling port under the drum, input the differential pressure into the pre-built hot drum water level calculation model, and the hot drum water level calculation model outputs the drum water level under hot working conditions; Measure the drum lower wall temperature and drum pressure, obtain the saturation temperature corresponding to the drum pressure through the drum pressure, compare the drum lower wall temperature and the saturation temperature corresponding to the drum pressure, and if the drum lower wall temperature is higher than the saturation temperature corresponding to the drum pressure, select the drum water level under the hot working condition; otherwise, select the drum water level under the cold working condition; The formula for the cold drum water level calculation model is: Where: H is the drum water level, L is the reference water column height, ρ c is the average density of the reference water column, ρ w is the density of water in the drum, ρ a is the air density in the drum, ΔP is the differential pressure between the balance container and the sampling port below the drum; The formula of the hot drum water level calculation model is: Where: H is the drum water level, L is the reference water column height, ρ c is the average density of the reference water column, ρ w is the saturated water density of the drum, ρ s is the saturated steam density of the drum, ΔP is the differential pressure between the balance container and the sampling port below the drum; The drum water level is calculated using the cold drum water level calculation model before the drum is filled with water or the boiler is ignited.

2. A cold and hot dual-state drum water level calculation device, characterized in that: include: Differential pressure transmitter: used to measure the differential pressure between the balance container and the sampling port under the steam drum; Cold drum water level calculation module: used to calculate the drum water level under cold working conditions through differential pressure; Hot drum water level calculation module: used to calculate the drum water level under hot working conditions through differential pressure; Temperature and pressure measurement module: used to measure the lower wall temperature and pressure of the steam drum; Hot and cold state switching module: obtains the saturation temperature corresponding to the drum pressure through the drum pressure, compares the drum lower wall temperature with the saturation temperature corresponding to the drum pressure, and selects the drum water level under the hot state if the drum lower wall temperature is higher than the saturation temperature corresponding to the drum pressure; otherwise, selects the drum water level under the cold state; The formula of the cold drum water level calculation module is: Where: H is the drum water level, L is the reference water column height, ρ c is the average density of the reference water column, ρ w is the density of water in the drum, ρ a is the air density in the drum, ΔP is the differential pressure between the balance container and the sampling port below the drum; The formula of the hot drum water level calculation module is: Where: H is the drum water level, L is the reference water column height, ρ c is the average density of the reference water column, ρ w is the saturated water density of the drum, ρ s is the saturated steam density of the drum, ΔP is the differential pressure between the balance container and the sampling port below the drum; It also includes a pulse module: used to reduce water level disturbances during the switching between hot and cold states and ensure automatic control of the water level.

3. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform the method of claim 1 .

4. A computing device, characterized in that include: One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including instructions for executing the method according to claim 1.

Images