Cleaning and/or unblocking of process equipment

A method of cleaning an internal cyclone of a fluidized bed process vessel, the method including:

• opening a permanent guide which forms an integral feature of the process vessel and which extends at least from an externally accessible vessel access port or entry nozzle to the internal cyclone of the process vessel, the internal cyclone comprising a gas inlet and a gas outlet;
• guiding at least one of a cleaning agent and a cleaning device by means of said permanent guide to the internal cyclone, the guiding occurring in a manner such that the cleaning agent or the cleaning device reaches into the internal cyclone without entering either the gas inlet or gas outlet of the internal cyclone;
• cleaning the internal cyclone with said at least one of a cleaning agent and a cleaning device;
• closing said guide;
• and
• operating the fluidized bed process vessel with said permanent guide remaining in the fluidized bed process vessel.