A well tool device for forming a permanent well barrier includes a housing having a circular cross-section and a longitudinal extension; a pyrotechnic mixture provided in the housing; a flow generating device provided in the housing; and a motor for driving the flow generating device. After ignition, the pyrotechnic mixture turns into a molten mass; and the flow generating device is configured to generate a forced flow of the molten mass. A method for forming a permanent well barrier using the well tool device includes installing the well tool device in a well; and igniting the pyrotechnic mixture. The pyrotechnic mixture turns into a molten mass upon ignition. The method further includes starting the motor; and generating a forced flow of molten mass by the flow generating device.