The name of instument as shown in figure is Electrostatic precipitator

Electrostatic precipitator a device that uses an electric charge to remove certain impurities—either solid particles or liquid droplets—from air or other gases in smokestacks and other flues. The precipitator functions by applying energy only to the particulate matter being collected, without significantly impeding the flow of gases. Originally designed for recovery of valuable industrial-process materials, electrostatic precipitators are used for air pollution control, particularly for removing harmful particulate matter from waste gases at industrial facilities and power-generating stations.