| A large number of bacteria and algae exist in industrial circulating cooling water system, the microorganism grown quickly not only seriously decrease thermal exchange efficiency of equipments but also cause equipment corrosion, which leads to great economic loss about 1 billion per year in China. Therefore, it is very significant to develop high voltage pulse generator and study on its inhibition effect of microbial growth in the cooling water.There are abundant research reports illustrated the obvious inhibition of bacterial growth with high voltage pulsed electric field(PEF) including parameters such as electric field intensity, the pulse width during one second and pulse polarity, whereas only a few reports introduced PEF’s inhibition effect on microalgae growth. Meanwhile, it is lack of the load characteristic data about the algae solution. Then, a newly high voltage pulse generator with monopolar/bipolar polarity output is put forward for microalgae experimental research. This paper illustrates the circuit structure and operation principle of each module. Moreover, operation principl e and output parameters are deduced and verified by PSIM software simulation on condition of a variety of loads such as resistive, inductive and capacitive loads respectively. In addition, a prototype of Pulse Generator is self-made whose output electrical parameters are as follows, peak voltage reaches ±7000V, maximum current attains ±10A, pulse frequency is up to 1000 pps, rising edge is 160 ns or so, pulse width is 4ms. The pulse generator can work stable at various load conditions, and it is easy to adjust the voltage, frequency, pulse width and polarity. In general, it is easy to realize modularization and miniaturization of manufacture, and the IGBT floating drive technology guarantees its safe and reliable operation.By using this high voltage pulse generator, experimental research firstly focus on testing the load characteristics of the chlorella pyrenoidosa solution. We find that the solution load is resistive, the volume, concentration and temperature of the solution all have significant impacts on the value of solution resistance. Moreover, in order to restrict algal liquid temperature not to exceed its suitable temperature range during pulse treatment, pulser generator’s maximum output parameter was calculated. Meanwhile, the reliability of the high voltage pulser and the feasibility of the graphite electrodes in processing chamber were verified. Then, the detailed experimental layout was design to investigate the impact of pulser’s single parameter on algae inhibition, The experimental data showed that high voltage pulses did have inhibitory effect on the proliferation and growth of chlorella pyrenoidosa. The optimum pulse parameters were chosen after comparing the experimental data from 18 test groups and one blank group, which includes EFI as 750 V/cm, pulse width as 4 μ s and molopolar pulses. According to data analysis for the single variable’s effect, we found that high voltage pulses has common growth inhibition effect on algae cell when the pulse electric field intensity is 750 V/cm, and the algae inhibition level changes regularly with the rising pulse treatment period per second and the same pulse polarity. However, when the electric field intensity is as low as 500 V/cm or 250 V/cm, pulsed electric field has no obvious regularity on algal inhibition effect. |
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