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Case Study

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The application of Huafei GBP medium voltage variable frequency drive in paper mill for Booster fan

2016-09-13 11:15:40 bobo HUAFEI Group

I. Overview

In the pulp (chemical) and paper manufacturing process to produce three major wastewater: black (red) liquid waste and paper machine white middle. Black (red) was mainly cooking pulp wastewater, including gray water pulp washing, screening, bleaching wastewater, waste paper machine white water of papermaking workshop. Wherein the waste water from cooking the most serious environmental pollution, accounting for 90% of the entire paper industry pollution.

The red liquid acid pulping produce is the key paper industry wastewater treatment. Paper red liquid handling system MVR evaporator. MVR evaporator, mechanical vapor recompression is the English abbreviation. MVR is the re-use of secondary energy generated by its own steam, thereby reducing the demand for a technology for external energy.

Secondary steam, compressed in a compressor, the pressure and temperature can be increased, increased enthalpy, it is supplied to the evaporator as the heating chamber is heated using steam that is generated steam, liquid material to maintain the state of evaporation, and the steam heating itself transferring heat to the material itself is condensed into water. Thus, it had to be abandoned steam has been fully utilized, the latent heat recovery, and improved thermal efficiency.

The technology is widely used in chemical, pharmaceutical, paper, sewage treatment, desalination and other industries.

Two, MVR evaporator system

MVR evaporator re-use of secondary energy generated by its own steam, thereby reducing the demand for a technology for external energy. Their work is low bit vapor compressed by the compressor, temperature, pressure increased enthalpy increases and then condensed into the heat exchanger, to take advantage of the latent heat of the steam. In addition to start the car, the entire evaporation process without the generated steam.

Multi-effect evaporation process, a secondary steam evaporator efficiency of this effect can not be directly used as a heat source, as a secondary effect or only a few times efficient heat source. As this effect as an additional heat source for its energy, its temperature (pressure) is improved. Steam ejector can only compress part of the secondary steam, MVR evaporator and evaporator can compress all of the secondary steam.

Solution in a falling film evaporator, the circulating pump through the material circulating within the heating pipe. The initial steam tube with fresh steam to heat the solution is boiled to produce secondary steam, the steam generated by the secondary turbo blower inhalation, pressurized secondary steam temperature is increased, as a heating source into the heating chamber cycle evaporation. After the start, the secondary turbo compressor steam inhalation, after heating becomes pressurized steam, so a steady stream circulating evaporated. Evaporated moisture eventually become condensed water discharge

Due to cost reasons, single-stage centrifugal compressor and pressure fan is widely used in mechanical vapor recompression system.

Increased evaporation fan pump is the core component of red liquid evaporation system, reliable and stable operation of the device is a set of red liquid evaporation system normal operation of the fundamental guarantee. Since the evaporation fan pressurized air pump special function in the entire system, so it is a special type of load, a non-fan and can not be equated to ordinary pump load, its great for the entire production process of the evaporator process control influences.

Third, mechanical pulp evaporation works

Mechanical pulp evaporation wind pump is mainly used for waste water treatment plant, field process shown in Figure 1:

Figure 1 site process

work process:

Evaporator fan ... high temperature (greater than 100 ℃) was evaporated into high temperature steam pipes, and then pulls out the subsequent stage of the steam back to the evaporator, if the evaporator temperature is lower than 100 deg.] C, then the plant will be added to the high temperature steam evaporated fan, the steam temperature is maintained above 100 ℃. The preheater is heated by a pump, and concentrated wastewater is introduced into the processing MVR evaporator in a heat exchanger, recycling of waste water using steam heating, evaporation, concentration and other treatment, distilled water was refluxed into the preheater, and to for preheating the liquid concentrate obtained and the steam enters the separator through the separator, the separated steam into the compressor, and the separated concentrate were directly back to the collection tank, is processed in the concentrate. wherein the recyclable useful substances, to achieve zero discharge of wastewater, protection of the environment.

(1) liquid preheater to be treated in a heat exchanger before entering the steam temperature is low, in order to take full advantage of the thermal energy within the system requires the use of a heat exchanger for preheating liquid.

(2) liquid evaporator preheated by feed pump load it into the evaporator, compressor and compressed steam heated by steam boost after heat exchange, it quickly vaporized.

(3) separator: separator is a steam and a concentrated liquid separating devices.

(4) a compressor (air pump) MVR system is the core component, through the system of the second vapor compression, enthalpy increase, then the temperature and pressure increase in the secondary steam as a heat source for heating the system .

(5) Control System: IPC and PLC constitute the real-time control system, the MVR evaporator. Through software programming, real-time acquisition status signals from various sensors to automatically control the motor speed, valve switch and adjust the liquid flow rate and flow rate, temperature and pressure control and regulation, to make the system work to a state of dynamic equilibrium. Meanwhile, the device also has an automatic alarm, automatic recording parameters and provide various functions report.

(6) After washing system solution was evaporated over time, it will occur fouling, fouling by adding a chemical solvent removal.

(7) Vacuum system: the role of the vacuum system is to maintain the degree of vacuum of the system, part of the air extracted from the device, as well as non-condensable gas into the solution of the gas in order to achieve a steady vaporization system state.

Fourth, the variable frequency drive speed control principle

Induction motor speed n and frequency f, the motor slip s, motor pole pairs p have the following relationship:

N = 60f (1-s) / p

Seen from the above formula, n and frequency f is proportional to the rotational speed, as long as the change in the frequency f can change the motor speed, and motor output power will change, linear relationship between n and f, when f changes 0 ~ 50Hz when the rotational speed of the adjustment range is very wide. When the load changes induced draft fan speed is reduced, decreasing the output power also learned from the principle of fluid mechanics, using an induction motor-driven fan load, shaft power P and flow Q, head H relationship is as follows:

When the motor speed to change from the n1 and n2, Q, H, P and speed relationship is as follows:

Visible flow rate Q and the motor speed is proportional to n, and the desired shaft power P is proportional to the cube of speed. So when you need 80% of the rated flow rate by adjusting the motor speed to the rated speed of 80%, which can adjust the frequency to 40Hz, then the power required will be only the original 51.2%.

As shown in Figure 2, the fan from running graph to analyze the energy saving effect of frequency control post.

Run graph 2 booster fan

When the desired air volume flow rate is reduced from Q1 to Q2, if the adjustment flap approach adopted, it will increase the resistance of the pipe network, pipe network characteristic curve shift, the system operating point from point A change to the new operating operating point B point run, the required shaft power P2 and H2 × Q2 is proportional to the area; if speed control, fan speed decreased from n1 to n2, its pipe network characteristics are not changed, but the fan characteristic curve down, so the operating conditions from the point A moves to point C. In this case the required shaft power P3 is proportional to the area HB × Q2. Theoretically, savings shaft power Delt (P) is proportional to (H2-HB) × (C-B) in the area.

Reduced efficiency and speeder after considering the deceleration additional losses, through the practice of statistics, fan speed control can save energy by 10% to 40%, some energy-saving fan load ratio of more than 50%.

Firth. Huafei GBP Series MV variable frequency drive technology Features

Jiaozuo HuaFei research and production of Hua Fei GBP series voltage variable frequency drive multi-unit tandem technology, has its own basic functions, also has a unique advantage with other manufacturers variable frequency drives, following China fly GBP series voltage variable frequency drive reliability for an introduction:

Since its inception in 2002, already has more than eight years experience in the production of variable frequency drive production equipment and spare parts, or similar equipment, the company has passed IS09001 certified quality assurance system in January 2006. Inverter device using a plurality of low-voltage PWM inverter power unit in series in a manner direct voltage output. Having minimal harmonic pollution, high input power factor, good output waveform quality, there is no additional motor heating caused by harmonics, torque ripple, noise, dv / dt and common mode voltage issues such characteristics, without adding output filter, you can use ordinary asynchronous motor, no need to replace the motor. Internal communications should inverter device using optical fiber connection, in order to improve communication speed and noise immunity.

In the power unit module is designed for different current ranges with a unique inlet and outlet design, anti-interference ability;

In the structural design and electrical design, the overall use of anti-electromagnetic interference measures to ensure the most efficient and reliable operation of variable frequency drives.

Three core control technology, medium-voltage variable frequency drive main control system adopts DSP + FPGA + ARM and LCD touchscreen with clever, provide Chinese-touch interface, the control system is highly integrated, anti-interference ability, more powerful, more precise control, increasing the reliability of the product.

Rich control functions, our medium voltage variable frequency drive inherits its low-voltage control features, control functions is very rich. Performance in the frequency control mode is very flexible. Frequency control is divided into A and B frequency control, frequency control A control can have multiple sources (including PID control, multi-speed control belong to this aspect); B frequency control also has a variety of control, the user can choose to use flexible A frequency control source, B frequency control source or A + B, A, B the maximum. By this abstract mathematics, medium voltage variable frequency drive Jiaozuo Hua Fei can not only meet the requirements of process control simple situations, but also to meet the specific requirements of process control situations. In addition, the command channel selection is equally diverse. You can basically meet the wide range of application scenarios.

Module redundant configuration, the power unit with some redundant configuration. Power switching device by more than two times the actual configuration of the current and voltage operating parameters, such as the use of medium voltage 1700V IGBT, device parameters a large margin, high reliability.

The input side of the low harmonic design, rated load (on the grid) harmonics <2%; (on the motor) harmonic output side of <2%;

DSP control system modulation waveform optimization, Perfect Harmony ensures that the output waveform.

AVR function, it can automatically adjust the duty cycle of the PWM signal output according to the fluctuation of the bus voltage, thereby reducing the output voltage of the power grid voltage fluctuations fluctuations.

V / F control Torque boost function provides low torque boost function, which is mainly used to solve the low-frequency voltage loss caused by the resistance of the stator flux leads to the problem of insufficient.

Choose a variety of V / F curve offers a variety of V / F curve form (such as: multi-point V / F curve, power 1.3 times, 1.7 times the power, the power of 2.0 V / F curve), to meet a variety of different load requirements.

Input voltage and adaptable, allowing the network side voltage fluctuation between 10% -15%. AVR also has features that can automatically adjust the output voltage according to the fluctuation of the bus voltage. Side voltage network in a short time of less than 85% to 65% rating or greater than 110% to 120% of rated medium voltage variable frequency speed control system downtime and ensure continuous operation of the motor.

Long non-stop instantaneous power failure, avoid downtime caused by grid instability, our medium voltage variable frequency drive instantaneous stop the introduction of better treatment, can do more to adapt to the grid power shake 1S, whether fans or pumps , you can achieve the effect. If the fan class load, shake up the grid electricity 5S are no problem.

ULF speed tracking capabilities, effectively guarantee the rapid re-start the power-down, the whole band has speed automatic tracking function starts, regardless of how long the motor down, the motor regardless of the level of the band, the search will automatically track motor speed, acceleration and deceleration according to the set time to resume normal operation, do not worry about the motor running, can achieve real-time medium voltage motor starting and stopping control, ensure safe start.

Symmetrical bypass function, the unit body double bypass technology, system reliability, using electronic bypass (internal bypass) optional mechanical bypass strategy (external bypass), which can be mechanical bypass completed in 200ms automatic bypass of the power unit and the electronic bypass, as are electronic components control, the operation time will come soon, in milliseconds to complete the bypass operation. And whether it is mechanical or electronic bypass bypass, we went through a rigorous overloading, small inertia load verification, completely reliable bypass.

Dual power-limiting circuit design, the effective protection of system security, extend equipment life, using the hardware current limit, and software limiting technology, when the effective protection of the system because the load mutations lead to over-flow problems of failure, improve the reliability of the product sex

Anti output short circuit protection technology, the system output when a cable short circuit protection quickly, without causing other adverse consequences.

Sixth, rehabilitation programs

The end of August 2015, the Yanbian Shixian Deer Industrial Co., Ltd. mechanical pulp wind pump pressure booster fan frequency control in progress, this transformation to transform an electric motor, using a drag and automatic isolation mode, the blower motor can be cited workers, frequency two modes. After comparative analysis, the choice of Jiaozuo Hua Fei Hua Fei Electric Co., Ltd. production GBP-A0400-06-S series medium voltage variable frequency drives, variable frequency drive of the device is a diode rectifier, inverter device is IGBT, the control method of speed sensor vector control, performance is more superior. In August 2015 the new system fully operational.

Table motor parameters and supporting medium voltage variable frequency drive parameters

Seven, the system is running Process Description

After the variable frequency drive 6kV power input via the inverter device with knife contacts to medium voltage variable frequency device, an output frequency by means qualifying knife and contactors to the motor; 6kV power supply can also be contacted directly by bypassing the starter motor. Inlet and outlet knife with knife contacts and bypass contactor role is: Once the inverter device fails, you can immediately disconnect the inlet and outlet with knife contact, the frequency isolation device, manually close the bypass contactor, starter motor running frequency power supply. Bypass cabinet with five anti-lockout feature; with workers, inverter-type indicator; charging indicator and electric lock door function.

Modification primary circuit as shown in Figure 3. In order to fully guarantee the reliability of the system, to the variable frequency drive at the same time the installation of frequency bypass means abnormal variable frequency drives, variable frequency drive stops running, the motor can automatically (process requiring manual) to switch to the operating frequency operation state, so you can to ensure the normal safe operation of the unit.

In order to achieve the protection of the variable frequency drive failure, a variable frequency drive for 6kV switch QF interlocked, once the variable frequency drive failure, variable frequency drive tripping QF. When the frequency bypass, variable frequency drive always allow closing QF, QF revoke a trip signal to enable the motor to start frequency by closing QF.

Frequency control system by the user switches, automatic bypass cabinet, Hua Fei GBP series voltage variable frequency drives, medium voltage motor. Bypass contactor KM1 pressure cabinet is composed of three vacuum, KM2, KM3 and MV disconnect switch QS1, QS2 composition. Normal operation QS1, QS2 all closed, only disconnected during maintenance. When the motor is running in inverter mode, KM1, KM2 closed, QS3 off; the motor runs in frequency mode when, KM3 closed, KM1, KM2 disconnected. Switching between frequency inverter and automatic / manual completed. Bypass cabinet strict accordance with the "Five Anti" interlock requirements of the design, the inverter output frequency switch KM2 and KM3 interlock switches, fully able to ensure safe operation of frequency control system.

Since the entire inverter system before the user-level switchgear with overload protection device, thus manual bypass cabinet will not overload the motor. Switchgear and users must break protection value in accordance with 8-10 times the rated current set speed, excitation inrush ensure escape.


A circuit diagram of FIG. 3 after the transformation

 

Eight, after the analysis of the economic benefits of energy-saving

After the booster fan frequency transformation, medium voltage variable frequency drive is put into operation a success. And energy efficiency and to achieve the desired control on the requirements. Operation on the locale photograph shown in Fig.

Figure 4 Field MV variable frequency drive

Compared with the original frequency drive, the current shutter open, variable frequency drive running at 40Hz, compared with the previous shutter adjustment mode to reduce power consumption significantly. Statistically comprehensive energy-saving rate up to 25%

Conclusion

After a booster fan frequency transformation, energy-saving effect is very obvious, and the starting frequency, low speed, current small and smooth. To achieve a soft start, to avoid large current high torque before start labor frequency impact on motors, cables, switches and mechanical equipment. Not only to extend the life of the motor and other equipment, but also reduce bearing wear, improving the security of electricity supply reliability.

Recommended paper mill new projects, technological transformation projects in the comprehensive application of inverter technology, elimination of inefficient adjustment tailgate, valves, and other ways to monetize the maximum less energy consumption and pollutant emissions, energy efficiency is submitted for our energy emissions contribute.

references:

[1] HuaFei GBP series voltage variable frequency drive manual. Jiaozuo Hua Fei Electric Co., Ltd.

[2] Huafei GBP medium voltage variable frequency drive series commissioning instructions. Jiaozuo Hua Fei Electric Co., Ltd.

about us:

Jiaozuo Huafei Electronic & Electric Co., Ltd. is established on 1987, the head quarter located in Beijing capital of china, two producing bases located in middle of China, it is the national high-tech enterprise and its technology center, company has been mainly engaged in the research and production of hoisting, transporting and automatic control complete equipment which is of safe, reliable and advanced technology such as AC, DC and frequency conversion hoister electric control device, mining in general and explosion-proof hoister, frequency conversion device of conveyor, multi-level mine hoisting signal device, stochastic control system of conveyor and medium voltage inverter, explosion proof inverter, high power dc speed regulator and so on,

contact us:

Official website: http: //en.jzhfdq.com

E-mail: info@jzhfdq.com

Hotline: +86 391 2971115

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