A total of four motors in this boiler use D32 frequency converters to control steam, hot oil and hot flue gas respectively. The hot flue gas is controlled by two 315KW motors, and sent to the main fan through pipes for drying wood pulp. Two 315KW QD6000 inverters control the two fans respectively, and control the output power of the fans by adjusting the output frequency of D32, so as to realize the precise regulation of the flow of hot smoke, which not only meets the requirements of the process, but also is more efficient than using a windshield. It is more energy efficient to adjust the flow of hot smoke. The other two 132KW motors feed the steam from the steam generator and the hot oil from the thermal oil generator into the mixing chamber respectively. The adjustment of the steam output in the steam generator can control the pressure and temperature in the steam generator, and the adjustment of the thermal oil output in the thermal oil generator can control the temperature of the thermal oil generator. D32 also adjusts the output of steam and hot oil by controlling the output power of the motor, so as to control the pressure and temperature of the steam generator and the temperature of the hot oil generator.