Method for operating lock hopper and solid movement device

A method for operating a lock hopper, the method including a solid movement step, wherein

• the solid movement step is a step of moving a solid from either one of an inside of a combustible gas production system and an outside of the combustible gas production system to another one of the inside of the combustible gas production system and the outside of the combustible gas production system, by introducing a solid into a lock hopper or discharging the solid from the lock hopper,
• the combustible gas production system is a system that produces a combustible gas,
• the method includes a non-combustible gas introduction step and a discharge step,
• the non-combustible gas introduction step is a step of introducing a non-combustible gas into a lock hopper from a path different from an introduction port for the solid and a discharge port for the solid, and
• the discharge step is a step of discharging a gas in the lock hopper from the lock hopper by using a path different from an introduction port for the solid and a discharge port for the solid.