A new way to save electricity and reduce consumpti

2022-07-24
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Abstract: This paper introduces the exploration and experience of the shale refinery of Fushun Mining Group in the application of high voltage variable frequency speed regulation equipment, and introduces the technical characteristics of domestic HARSVERT-A high voltage variable frequency device. Through the comparison of different working conditions, it shows that the energy-saving effect of frequency conversion transformation of main fan in shale retort unit is remarkable, and the safety and reliability of equipment and system are improved

key words: oil refinery main fan frequency converter energy saving

I. preface

in the oil refining process of shale retort unit, an important link is to use centrifugal fan (i.e. main fan) to supply air to the generation section at the lower part of the retort furnace, in order to provide saturated air for the oxidation-reduction reaction of shale semi coke at the upper part of the retort furnace. The driving motor power of the main fan is 250KW and the voltage level is 6000V. In actual operation, the air supply volume of the main fan shall be adjusted according to the control requirements of various process indicators in the reaction device. The air volume shall be adjusted by manually adjusting the opening of the butterfly valve at the inlet of the main fan and the opening of the vent, and the excess air volume shall be discharged through the vent. The working current of the motor is 20 ~ 22a, and the output of the motor is about 70%. According to the requirements of the production process, the air volume should be manually controlled by the workers once or twice every hour, and a large amount of air is discharged through the vent. Therefore, this air volume adjustment method is unreasonable, the labor intensity of the workers is high, and it causes unnecessary waste of energy consumption, which is in urgent need of improvement

the frequency conversion and speed regulation transformation of the main fan can not only meet the production process requirements, but also replace the workers to adjust the air volume with valves, saving a lot of electric energy. Through the frequency conversion transformation, the equipment has low noise, reduced equipment wear, prolonged the service life of the equipment, and saved maintenance costs, which has opened up a new way for the energy-saving transformation of the refinery

II. Feasibility demonstration of applying variable frequency speed regulation technology

at the initial stage of technical transformation of department D (No. 4 branch), we demonstrated whether the main fan could be transformed by variable frequency. From the process point of view, the flow of the main fan should be adjusted frequently every day. The workers have to pay heavy labor, and the adjustment deviation is large. If the motor adjusts the speed through the frequency converter, it can meet the needs of the process, achieve accurate adjustment and save manpower. More importantly, during the operation of the fan, the smaller the opening of the inlet butterfly valve, the more energy will be lost on the fan baffle. Therefore, there will be a lot of energy-saving space for the speed regulation operation of the main fan as required

according to the operation characteristics of the main fan of the existing retort unit, through the market research of a specially assigned person, it is found that there are three schemes that can be implemented and applied:

1. High high high frequency conversion: on the basis of the original high-voltage electrical components, it is unnecessary to transform the motor and purchase a high-voltage frequency converter

2. High low high mode: first change the high-voltage power supply into the low-voltage power supply, use the low-voltage frequency converter, change the 300KN tensile testing machine to test the test bar frequency, and then boost the voltage, and the motor does not need to be modified

3. High low mode: a separate transformer is used to reduce 6kV high voltage to 380V, and the industrial layout scheme of coal chemical industry is adopted: low voltage frequency converter and low voltage motor

compared with the three schemes, the high high frequency converter is used, and the motor does not need to be modified. It can be started directly in case of frequency converter failure. There are finalized products with good performance, stability and reliability, but the cost is high; For high low high mode amorphous products, it is necessary to redesign the circuit and successfully industrialize it into the commercial field. The circuit is cumbersome and huge. It is necessary to add two transformers, and the cost is also high; In the high-low mode, the frequency converter directly uses the low-voltage power supply, and the capacity of the transformer currently used is insufficient, so another step-down transformer needs to be set. When the capacity of step-down transformer is relatively small, the motor cannot be started directly after the frequency converter fails. If the capacity of step-down transformer is too large, the cost of capacity increase will be increased, and the transformer will have certain power loss. Through comprehensive comparison, we choose the direct high-high frequency control scheme

III. application attempt of variable frequency speed regulation technology

in order to ensure the success of the transformation without detours and reduce losses, we first conducted a more detailed theoretical demonstration and believed that it was feasible in theory. Two professional technicians were assigned to consult a large number of data. According to the requirements of the technical process, various parameters of the fan operation were compared, and the number of revolutions of the motor under different process requirements was calculated in combination with the favorable conditions available on site. The power required by the motor was calculated. Through the calculation, it was known that there is a large space for power saving. At the same time, we also conducted field research on Fushun new Fushun Iron and Steel Co., Ltd. and Shandong Laiwu Steel Co., Ltd. in the city, and learned that the high-voltage inverter they used was in good operation. After that, I got to know the manufacturing enterprises of high-voltage frequency converters and made a field visit to the manufacturing base of Beijing Lide Huafu company. Through investigation and demonstration, we believe that Beijing Lide Huafu Electric Technology Co., Ltd. has advanced technology, standardized management, advanced production and manufacturing process, and the high-voltage inverter manufactured by it has stable and reliable performance. On this basis, it is decided to select a high-voltage inverter on the main fan of the dry distillation unit of Part D for test operation, and finally select the harsvert-a06/030 high-voltage inverter produced by Beijing Lide Huafu company

harsver-a variable frequency device adopts the unit series multi-level PWM topology. Several low-voltage PWM variable-frequency power units are connected in series to realize direct high-voltage output, that is, 6kV output voltage has 7 power with rated voltage of 480v per phase. It feels that only those with brands are made of market guaranteed units in series. The output phase voltage is 3450v, and the line voltage reaches about 6kV. The device system configuration is shown in Figure 1. This technology is the most extensive and mature technology in the field of high-voltage frequency conversion

Figure 1: system diagram of harsver-a high voltage variable frequency speed regulation device

the speed regulation device has the following characteristics:

◆ the frequency converter is of high-high structure, and does not need to output step-up transformer. The efficiency of the frequency converter is as high as 96%

◆ the 42 pulse rectifier circuit structure makes the input current waveform close to the sine wave, the total harmonic current distortion is less than 4%, and the input power factor is more than 0.95

◆ the inverter output adopts the multi electric translation phase PWM technology, and the output voltage is close to the sine wave. Each level step of the output voltage is only the voltage of the unit DC bus, so the dv/dt is very small, and there is no need to configure a special filter device

◆ power units are connected in series instead of power devices. The maximum voltage borne by devices is the voltage of DC bus in the unit. Devices do not have to be connected in series, and there is no voltage sharing problem caused by devices connected in series

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