Anti-blocking pressure and accurate measurement are the consistent pursuit of all large, medium and small power plants in wind pressure measurement, and some important parameters in boiler operation (such as furnace pressure, flue gas pressure, coal mill pressure, one or two Secondary air pressure, etc.) The containment problem must be solved to make accurate measurements. At present, the power plant's anti-blocking pressure generally adopts conventional anti-blocking samplers, such as a vase-type built-in three-layer anti-blocking mechanism sampler, self-cleaning ash (static, dynamic pressure) sampler and rated continuous purging anti-blocking device ( The amount of blowing 60L/H), etc., these products have a little effect on the anti-blocking pressure, but it is not very obvious, or often appear to block. Bid farewell is that the fluidized bed boiler is more likely to be blocked. The combustion in the fluidized bed hearth utilizes a strong wind to make the material flow to fully burn. The fluidization in the hearth is an important operating parameter, but the flowing material is easy to Blocking the conventional anti-blocking sampler will have a certain impact on the safe and energy-saving operation of the boiler.
In view of the above situation, after years of research and several field tests, the company has used the principle of fluid mechanics to study the SCY-FDQY series of compensating antiblocking and pressure-removing devices. The device is composed of an anti-blocking sampler and a compensation control box, completely and completely solves the problem that it is necessary to take pressure and prevent clogging, and the measurement accuracy is correct. The anti-blocking sampler can thoroughly remove the dust, particles and attachments in the sampling tube. The compensation control box consists of a compensator, oil filter, and trimming. The system not only completely solved the anti-blocking problem, but also greatly improved the measurement accuracy, the absolute error is less than 5Pa. It fundamentally solves the problem of large measurement error of traditional anti-blocking devices. The application of this device provides a powerful guarantee for safe and reliable operation of power plant boilers.
The device has the advantages of reasonable structure, convenient installation, never blocking, accurate measurement, etc. It will be widely used in electric power, petroleum, chemical industry, metallurgy and material industry.
○Main technical indicators
1, instrument air pressure: ≥ 0.6MPa
2, measurement error: ≤ 0.5Pa
3, the internal blowback air consumption: 0.5 ~ 1.5m3 / h pressure of 0.24MPa (adjustable)
4, the use of the environment: -30 ~ 70 °C, relative humidity: ≤ 95%
5, protection class: IP56
6, Purge sample tube material: 1Cr18Ni9Ti
○ Anti-blocking sampling device numbering method
1. Using dynamic pressure compensation method of fluid mechanics to truly reflect the pressure value of each point online, it is necessary to locally solve the problem that the accuracy of the transmitter is improved quickly, and the measurement error of the system is indeed large.
2. The pressure of purging is greater than the measured pressure, which completely solves the problem of clogging and burning of the pressure measurement pipeline under the state of multi-dust and temperature regulation.
3. The regulator regulator can be used to regulate the gas source provided by the power plant to ensure that the output of the flow controller is stable and can achieve long-term reliable operation.
4. There is an independent compensator and pressure accurate compensator, so that the absolute pressure error ≤ 5Pa.
5. No artificial purging is required, which greatly reduces the artificial labor intensity.
6. The control box adopts IP56 structure, beautiful appearance, small size and easy installation.
7. The biggest feature of the device is the use of advanced and reasonable compensation methods for integrated structures, which are applicable to both static and differential pressure measurements. The distance between the control box and the pressure measurement point is increased from 4 meters to 200 meters.
○Structure and principle
The compensating anti-blocking and pressure taking device consists of two parts: a constant air flow control box and a purging pressure sampler (head). (See Figure 1)
Anti-blocking pressure device mechanism as shown above
Principle: The measuring principle of the device is to use the method of continuous ventilation in the measuring point to prevent the blocking of the measuring point, and to use the dynamic pressure compensation method of fluid mechanics to eliminate the differential pressure generated by the reverse purge flow to ensure the true and accurate measurement. The value, which is the biggest feature of the compensation type blocking prevention measuring device.
Its derivation formula is as follows:
In the above figure, if no compensation device is added, the pressure difference between the sampling point PA and the purge port PB of the pressure transmitter port due to gas flow is ΔP, and the density of the flowing gas is ρ. The air velocity is V and the air resistance coefficient is λ.
It can be seen from the formula that changes in gas pressure can cause changes in the gas flow rate and changes in ΔP. In the conventional purging method, in order to ensure the measurement accuracy, only a small flow rate can be selected, so that it is easy to cause clogging and burnout; if the flow rate is increased, the transmitter must also generate a zero offset, and then only the transmitter and the transmitter must be used. The method of displaying the instrument zero is displayed, which causes the display system to be confusing. It is also difficult to correct the problems during operation. The faults and deviations of the pressure regulating valve and the flow controller will directly affect the measurement accuracy, and the daily maintenance workload is quite large.
In order to overcome the above drawbacks and improve the accuracy of measurement, a pressure compensation device is added to the system. The compensation pressure is set to P2, and the pressure after compensation is PC.
The PB varies with the flow rate, and the PA value is not affected by the nitrogen source pressure and the gas flow rate.