Temperature control loop of denitration electric heater

Abstract

The utility model discloses a denitration electric heater temperature control loop, which comprises a temperature detection module, a logic judgment module and a temperature control module which are sequentially connected, and the temperature control module comprises a plurality of temperature measuring elements which are respectively connected with each input end of the logic judgment module and independently output temperature signals. And the logic judgment module comprises a three-out-of-center unit, performs logic judgment on the temperature signal, and is connected with each isolation control element in the temperature control module through a plurality of control signal output ends, so that the control signal is independently output, and temperature control is completed. The temperature control module is connected with the power supply module, undisturbed switching of multiple alternating current power supplies is carried out through the power supply switching switch, and the power supply reliability is improved. The utility model solves the technical problem that when a single element in the temperature control loop fails, the temperature control loop can not work normally, and the electric heater can not operate safely.

Description

Technical Field

[0001] The utility model relates to the field of electric heating temperature control, in particular to a denitration electric heater temperature control loop. Background Art

[0002] The denitration electric heater of coal-fired power plants is a key equipment of the denitration system. Once it is shut down, it will affect the operation of the denitration system, causing the unit's NOx emissions to exceed the standard and the unit to shut down unplanned. The four groups of denitration electric heating thyristor power thermostats KTM1, KTM2, KTM3, and KTM4 are provided with temperature signals by a single medium temperature outlet isolation distributor IG. The control operation of the isolation distributor IG only uses one outlet medium temperature element. Once the outlet medium temperature element fails or has a large measurement error, the control operation of the entire medium temperature outlet isolation fence distributor IG cannot be carried out, and the signal cannot be provided to the medium power thermostat, and the heater temperature cannot be adjusted, and even an over-temperature protection trip occurs.

[0003] On the other hand, if a single medium temperature outlet isolation grid distributor IG fails, the denitrification heater cannot be automatically adjusted and is forced to stop operating. The denitrification electric heating control power supply is designed to be output through the intermediate relay after the 4 power supply B phases are connected in parallel. Since the power output by the 4 groups of thyristors is not completely consistent, and the resistance of each group and each phase of the electric heating core cannot be exactly the same, the probability that the actual value of the control power supply voltage running in parallel is exactly the same is very small. Once the heater load fluctuates greatly, the voltage of two or more control power supplies will deviate, and a circulation current will be generated between the parallel control switches, causing the control power switch current to increase, and the current overload will trip. If only one control power supply circuit breaker is closed, when the group of loads fails and the power supply switch trips, the control power supply will also be lost. It is very easy for the control circuit breaker to trip completely, causing the heater control power supply to be lost, resulting in the entire heater tripping. The unreliability of the control power supply brings great risks to the stable operation of the heater. Summary of the invention

[0004] The utility model provides a temperature control loop for a denitration electric heater, so as to solve the technical problem that when a single component fails, the temperature control loop cannot work normally, resulting in the electric heater being unable to operate safely.

[0005] In order to solve the above technical problems, the embodiment of the utility model provides a denitration electric heater temperature control circuit, including a temperature monitoring module, a logic judgment module and a temperature control module connected in sequence;

[0006] Among them, the temperature monitoring module includes several temperature measuring elements, each of the temperature measuring elements is respectively connected to the logic judgment module, the logic judgment module includes three centering units, and the temperature control module includes several isolation control elements, and the isolation control elements are respectively connected to the control signal output end of the logic judgment module.

[0007] By setting multiple temperature measuring elements and judging through the three-way logic configuration, it is possible to avoid the problem of a single temperature measuring element failing or the temperature measuring element's measurement error being too large, which would cause the temperature control loop to not work properly, thereby improving the accuracy and reliability of the temperature control loop. Multiple isolation control elements can prevent the electric heater from not being able to operate safely when a single isolation control element fails, thereby improving the safety of equipment operation.

[0008] As a preferred solution, the temperature measuring elements are arranged at the outlet of the electric heater, and the distance between each of the temperature measuring elements and the electric heater is the same.

[0009] The temperature measuring element is used to monitor the temperature of the electric heater. A plurality of temperature measuring elements are evenly arranged and are used together to output a temperature signal to the logic judgment module for subsequent judgment.

[0010] As a preferred solution, the number of the temperature measuring elements is three, the temperature measuring elements are connected in parallel with each other, and the output ends of the temperature measuring elements are respectively connected to the input ends of the logic judgment module.

[0011] The three temperature measuring elements respectively output the collected temperature signals to the logic judgment module for three-way logic judgment, which not only avoids the failure of a single temperature measuring element to cause the inability to monitor the temperature, but also improves the accuracy of temperature measurement and enhances the temperature control effect.

[0012] As a preferred solution, the three-centering unit includes a first high selector, a second high selector, a third high selector and a low selector, the first input terminal and the second input terminal of the logic judgment module are connected to the first high selector input terminal, the second input terminal and the third input terminal of the logic judgment module are connected to the second high selector input terminal, the first input terminal and the third input terminal of the logic judgment module are connected to the third high selector input terminal, and the output terminals of the first high selector, the second high selector and the third high selector are connected to the low selector input terminal.

[0013] The three-median unit takes the median of the three input signals during operation. When the deviation of the measurement signals at the same position is too large, the control chip in the logic judgment module can output a control signal to achieve temperature control.

[0014] The logic judgment module also includes a control chip, the input end of the control chip is connected to the output end of the low selector, and the output end of the control chip is the control signal output end.

[0015] The logic judgment module can control the isolation control elements separately, so that the isolation control elements can work independently, thereby improving the reliability of the temperature control loop.

[0016] As a preferred solution, the logic judgment module includes a bad pixel locking unit, and the bad pixel locking unit includes a signal quality detector, and the signal quality detector is respectively connected to each input end of the logic judgment module.

[0017] When an abnormal temperature measurement result occurs, the corresponding temperature measurement element can be shielded through the bad point locking logic unit to avoid misjudgment based on the abnormal temperature measurement result and cause safety problems.

[0018] As a preferred embodiment, the logic judgment module also includes a relay control unit, which includes a first control loop, a second control loop and a third control loop, the first control loop includes a first switch and a first relay connected in series, the second control loop includes a second switch and a second relay connected in series, the third control loop includes a third switch and a third relay connected in series, and the first control loop, the second control loop and the third control loop are connected in parallel.

[0019] The corresponding relays can be controlled respectively by closing the switches, and the working state of the logic judgment module can be controlled by the relays.

[0020] As a preferred solution, the isolation control element includes a medium temperature outlet isolation grid distributor, the number of the medium temperature outlet isolation grid distributors is the same as the number of heating cores of the denitrification electric heater, and the medium temperature outlet isolation grid distributors are connected in parallel with each other.

[0021] The isolation control elements correspond to the heating cores respectively and are respectively connected to the temperature controllers controlling the corresponding heating cores, thereby providing individual control for each heating core and improving the safety of the temperature control loop and the independence of operation.

[0022] As a preferred solution, it also includes a power supply module, which is connected to the logic judgment module. The power supply module includes a power switching switch and a switching power converter. The input side of the power switching switch is connected to multiple external AC power sources, the output side of the power switching switch is connected to the input side of the switching power converter, and the output side of the switching power converter is connected to the temperature control module.

[0023] The power supply is supplied separately by the power module to improve the power supply reliability and ensure that the heater does not stop running due to power loss. The power switching device realizes that the control power supply of the temperature control circuit and the power supply of the electric heating module do not affect each other.

[0024] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0025] 1. The utility model improves the accuracy and reliability of temperature monitoring by setting multiple temperature measuring elements and making judgments through logical configuration according to the measurement results;

[0026] 2. The utility model realizes independent control by setting multiple isolation control elements, which are respectively connected to the temperature controllers controlling the corresponding heating cores, thereby improving the reliability of temperature control and avoiding the failure of the temperature control circuit to work normally due to the failure of a single isolation control element;

[0027] 3. The utility model improves the reliability of power supply to the temperature control circuit by providing a power supply module that supplies power independently and including a plurality of power supply units that can switch between working modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 : A circuit connection diagram of a temperature control circuit of a denitration electric heater provided in an embodiment of the utility model;

[0029] Among them, the figure numbers of the drawings in the specification are as follows: 1. Temperature monitoring module, 1.1. First temperature measuring element, 1.2. Second temperature measuring element, 1.3. Third temperature measuring element, 2. Logic judgment module, 3. Temperature control module, 3.1. First isolation control element, 3.2. Second isolation control element, 3.3. Third isolation control element, 3.4. Fourth isolation control element, 4. Power supply module, 4.1. Power switching switch, 4.2. Switching power converter. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0031] Reference Figure 1The figure shows a circuit connection diagram of the temperature control circuit of the denitrification electric heater provided in the embodiment of the utility model. As shown in the figure, the temperature control circuit of the denitrification electric heater provided by the utility model includes a temperature monitoring module 1, a logic judgment module 2, a temperature control module 3 and a power supply module 4. The output end of the temperature monitoring module 1 is connected to the input end of the logic judgment module 2, the output end of the logic judgment module 2 is connected to the input end of the temperature control module 3, and the power supply module 4 is connected to the temperature control module 3 to provide power output for the temperature control module 3.

[0032] The temperature monitoring module 1 is arranged at the outlet of the electric heater, and is used to monitor the internal temperature of the electric heater, and output a temperature signal to the temperature control circuit for subsequent judgment and control. The temperature monitoring module 1 includes a plurality of temperature measuring elements. In this embodiment, three temperature measuring elements are arranged in the temperature monitoring module 1, including a first temperature measuring element 1.1, a second temperature measuring element 1.2, and a third temperature measuring element 1.3. The temperature measuring elements are evenly arranged at the outlet of the electric heater, and each temperature measuring element has the same distance to the heating core assembly inside the electric heater, that is, each temperature measuring element has the same distance to the main heat generating position in the electric heater. Therefore, it can be considered that for a single electric heater, the temperature signals output by the first temperature measuring element 1.1, the second temperature measuring element 1.2, and the third temperature measuring element 1.3 should be the same.

[0033] During normal operation, if any temperature measuring element fails and stops working or outputs abnormal results, the measuring element can be stopped and monitoring can continue through the remaining temperature measuring elements to avoid the failure of a single temperature measuring element that causes the temperature to be unable to be measured normally, causing the temperature control loop to malfunction, thereby improving the stability and reliability of the temperature control loop.

[0034] The temperature measuring elements are respectively connected to the input terminals of the logic judgment module 2, that is, the first temperature measuring element 1.1 is connected to the first input terminal of the logic judgment module 2, the second temperature measuring element 1.2 is connected to the second input terminal of the logic judgment module 2, and the third temperature measuring element 1.3 is connected to the third input terminal of the logic judgment module 2. The first temperature measuring element 1.1, the second temperature measuring element 1.2 and the third temperature measuring element 1.3 output temperature signals to the logic judgment module 2 separately. The three temperature measuring elements respectively output the collected temperature signals to the logic judgment module to perform three-way logic judgment, avoiding the problem that the temperature cannot be monitored when a single temperature measuring element fails, resulting in the temperature control circuit not being able to work properly. At the same time, the accuracy of temperature measurement is improved, and the temperature control effect is improved.

[0035] In this embodiment, the temperature measuring element can be any one of the conventionally used measuring elements in the prior art, and the temperature measuring range must be 0-800° C. to adapt to the temperature measurement of the electric heater. In other embodiments, different types or different numbers of temperature measuring elements can be selected for connection to meet different practical application requirements.

[0036] The denitration electric heater temperature control loop provided by the utility model also includes a logic judgment module 2, the logic judgment module 2 includes a DCS logic configuration function block, and the DCS logic configuration function block includes a three-centering unit, a bad point locking unit and a control chip.

[0037] The three-centering unit includes a first high selector, a second high selector, a third high selector and a low selector, wherein the first input terminal and the second input terminal of the logic judgment module 2 are connected to the input terminal of the first high selector, the second input terminal and the third input terminal of the logic judgment module 2 are connected to the input terminal of the second high selector, the first input terminal and the third input terminal of the logic judgment module 2 are connected to the input terminal of the third high selector, and the output terminals of the first high selector, the second high selector and the third high selector are all connected to the input terminal of the low selector.

[0038] The first high selector compares the signals inputted from the first input terminal and the second input terminal of the logic judgment module 2, selects the signal with the higher value and outputs it. The second high selector compares the signals inputted from the second input terminal and the third input terminal of the logic judgment module 2, selects the signal with the higher value and outputs it. The third high selector compares the signals inputted from the first input terminal and the third input terminal of the logic judgment module 2, selects the signal with the higher value and outputs it. The low selector compares the three input signals, selects the signal with the lower value and outputs it. It can be seen that the result outputted from the high selector includes the highest signal and the second highest signal, and the second highest signal can be selected as the actual output value by the low selector, thereby completing the three-select output.

[0039] The three-centering method can realize the deviation check of the signal measuring the same input quantity, take the median of the three input signals, and when the deviation of the measurement signal at the same position is too large, the control chip can output a control signal to achieve temperature control. This method avoids the measurement element outputting an abnormal signal, causing the logic judgment module 2 to make a misjudgment and cause safety problems, and improves the accuracy of temperature monitoring. In other embodiments, the three-centering unit can also adopt other structures to meet different practical application requirements.

[0040] The logic judgment module 2 also includes a control chip, the input end of the control chip is connected to the output end of the three-centering unit, and the temperature signal output by the three-centering unit is received. According to the level of the temperature signal, it is judged whether the temperature in the electric heater is within the normal range at this time, and the control chip optimizes the obtained signal into multiple identical control signals. In this embodiment, the control chip includes four control signal output ends, which are respectively connected to each isolation control element in the temperature control module 3, and outputs a control signal to each isolation control element. When the temperature is within the normal range, no operation is performed, and the temperature continues to be monitored. When the temperature exceeds the normal range, at this time, according to the difference between the actual temperature and the preset normal temperature, a control signal is output from the control signal output end, thereby controlling the isolation control element to complete temperature control.

[0041] The bad point locking unit includes a signal quality detector, which is arranged at each input end of the logic judgment module 2, and is used to detect the quality of the output signal of the temperature monitoring module 1, and judge whether the received signal is a bad point or exceeds the normal range. When the input signal is judged to be a bad point, the bad point locking unit shields and locks the path where the signal is located to prevent the output of the wrong signal. At this time, the logic judgment method of the three-centering unit is to take the average of the remaining two signals and output them. When there are two signals judged to be bad points, the logic judgment method of the three-centering unit is to automatically take the remaining signals and output them. When all signals are judged to be bad points, an alarm is issued to the outside through the control chip. When an abnormal temperature measurement result occurs, the bad point locking logic unit can prevent the temperature control circuit from making a misjudgment based on the abnormal temperature measurement result, resulting in safety problems. In other embodiments, the bad point locking unit can also adopt other structures to meet different practical application requirements.

[0042] The logic judgment module 2 also includes a relay control unit, which includes a first control loop, a second control loop and a third control loop, wherein the first control loop, the second control loop and the third control loop are connected in parallel.

[0043] The first control loop includes a first switch and a first relay KA1 connected in series, and the first relay KA1 is used to start the logic judgment module 2, thereby starting the temperature signal judgment process. The second control loop includes a second switch and a second relay KA2 connected in series, and the second switch is used to control the opening and closing of the second relay KA2, and the second relay KA2 is used to stop the logic judgment module 2, thereby stopping the temperature signal judgment process. The third control loop includes a third switch and a third relay KA3 connected in series, and the third switch is used to control the opening and closing of the third relay KA3, and the third relay KA3 is used to repair the logic judgment module 2. The corresponding relays can be controlled by closing the switches, and the working state of the logic judgment module can be controlled by the relays.

[0044] The temperature control module 3 includes a plurality of isolation control elements. In this embodiment, the isolation control element is a medium temperature outlet isolation grid distributor IG, the number of which is the same as the number of heating cores in the electric heater, which is four. It is arranged in the electrical control cabinet that controls the electric heater, and is connected to the thermostat KTM that controls the corresponding heating core through the temperature control signal output terminal TC, and acts on the heating core alone. After receiving the control signal, the medium temperature outlet isolation grid distributor IG outputs the corresponding temperature adjustment signal through PID control adjustment, thereby controlling the temperature of the heating core and improving the safety of the operation of the electric heater.

[0045] The isolation control elements are connected in parallel with each other, and the control signal receiving end of each isolation control element is respectively connected to the control signal output end of the logic judgment module 2, wherein the first control signal output end of the logic judgment module 2 is connected to the control signal receiving end of the first isolation control element 3.1, the second control signal output end is connected to the control signal receiving end of the second isolation control element 3.2, the third control signal output end is connected to the control signal receiving end of the third isolation control element 3.3, and the fourth control signal output end is connected to the control signal receiving end of the fourth isolation control element 3.4, thereby realizing separate control of the isolation control elements, avoiding the temperature control circuit from being unable to adjust the temperature of the heating core when an isolation control element fails, ensuring that the failure of any isolation control element does not affect the safe operation of other groups of heating cores, and improving the reliability of the operation of the electric heater.

[0046] The temperature control loop of the denitration electric heater provided by the utility model also includes a power module 4, which is connected to the isolation control element. The power module 4 includes a power switch 4.1 and a switch power converter 4.2.

[0047] The input side of the power switching switch 4.1 is connected to multiple external AC power supplies, including the power supply for the unit working section and the power supply for the dust removal section, both of which provide 220V AC power input for the power module 4. The power module 4 can switch between the two inputs without interference through the power switching switch 4.1. When the temperature control loop is working, it is only connected to one of the power inputs, avoiding the deviation between the multiple power supplies, resulting in commutation, causing the control power switch current to increase, and causing the current overload and tripping. If only one control power supply is connected, when the switch trips, it is easy to cause the control power supply of the temperature control loop to be lost, causing the electric heater to trip and fail to work normally. The power module 4 realizes that the control power supply of the temperature control loop and the power supply of the electric heater do not affect each other, thereby improving the reliability of power supply.

[0048] The output side of the power switching switch 4.1 is connected to the input side of the switching power converter 4.2, and the output end of the switching power converter 4.2 is connected to the isolation control element. The switching power converter 4.2 converts the input 220V AC power into the 24V DC power required by the isolation control element and outputs it, thereby powering the isolation control element.

[0049] In summary, compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0050] 1. The utility model improves the accuracy and reliability of temperature monitoring by setting multiple temperature measuring elements and making judgments through logical configuration according to the measurement results;

[0051] 2. The utility model realizes independent control by setting multiple isolation control elements, which correspond to the temperature controllers controlling each heating core respectively, and improves the reliability of temperature control, thus avoiding the failure of the temperature control circuit to work normally due to the failure of a single isolation control element;

[0052] 3. The utility model improves the reliability of power supply to the temperature control circuit by providing a power supply module that supplies power independently and including a plurality of power supply units that can switch between working modes.

[0053] The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the utility model in detail. It should be understood that the above description is only a specific embodiment of the utility model and is not intended to limit the protection scope of the utility model. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A denitration electric heater temperature control circuit, characterized in that: It includes a temperature monitoring module, a logic judgment module and a temperature control module which are connected in sequence; Among them, the temperature monitoring module includes multiple temperature measuring elements, each of the temperature measuring elements is respectively connected to the input end of the logic judgment module, the logic judgment module includes three centering units, and the temperature control module includes multiple isolation control elements, and the isolation control elements are respectively connected to the control signal output end of the logic judgment module.

2. The denitration electric heater temperature control circuit according to claim 1, characterized in that: The temperature measuring elements are arranged at the outlet of the electric heater, and the distance between each of the temperature measuring elements and the electric heater is the same.

3. The denitration electric heater temperature control circuit according to claim 2, characterized in that: The number of the temperature measuring elements is three, the temperature measuring elements are connected in parallel with each other, and the output ends of the temperature measuring elements are respectively connected to the input ends of the logic judgment module.

4. The denitration electric heater temperature control circuit according to claim 1, characterized in that: The three-centering unit includes a first high selector, a second high selector, a third high selector and a low selector. The first input and the second input of the logic judgment module are connected to the first high selector input, the second input and the third input of the logic judgment module are connected to the second high selector input, the first input and the third input of the logic judgment module are connected to the third high selector input, and the outputs of the first, second and third high selectors are connected to the low selector input.

5. The denitration electric heater temperature control circuit according to claim 4, characterized in that: The logic judgment module also includes a control chip, the input end of the control chip is connected to the output end of the low selector, and the output end of the control chip is the control signal output end.

6. The denitration electric heater temperature control circuit according to claim 5, characterized in that: The logic judgment module includes a bad point locking unit, and the bad point locking unit includes a signal quality detector. The signal quality detector is respectively connected to each input end of the logic judgment module.

7. The denitration electric heater temperature control circuit according to claim 6, characterized in that: The logic judgment module also includes a relay control unit, which includes a first control loop, a second control loop and a third control loop. The first control loop includes a first switch and a first relay connected in series, the second control loop includes a second switch and a second relay connected in series, and the third control loop includes a third switch and a third relay connected in series. The first control loop, the second control loop and the third control loop are connected in parallel.

8. The denitration electric heater temperature control circuit according to claim 1, characterized in that: The isolation control element comprises a medium temperature outlet isolation grid distributor, the number of the medium temperature outlet isolation grid distributors is the same as the number of heating cores of the denitrification electric heater, and the medium temperature outlet isolation grid distributors are connected in parallel with each other.

9. The denitration electric heater temperature control circuit according to claim 1, characterized in that: It also includes a power supply module, which is connected to the logic judgment module. The power supply module includes a power switching switch and a switching power converter. The input side of the power switching switch is connected to multiple external AC power sources, the output side of the power switching switch is connected to the input side of the switching power converter, and the output side of the switching power converter is connected to the temperature control module.

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