Cement, Energy and Environment

38 CPP boiler systems need typically a continuous addition of dilution water in order to better penetrate into the cross-section, which is typically not required in the high turbulent flow of a preheater / precalciner. Fig. 6 Installation of water softener, water pump module, process module and control module inside climate protected container near the injection levels Injectors The injectors and their location will have an important effect on the efficiency. They should be manufactured in stainless steel. The spraying length and width as well as the size of the droplets should be adjustable. The possibilities of adjustments give a broad flexibility and means that the spraying dose can reach a large area of the ducting. Compressed air is used to atomize the droplets of reduction agent. For injectors in stand-by the compressed air is used for cooling of the injector. The injectors are located in one or more levels on the ducting and the recipe of the control and management program will automatically select which injectors shall be in operation to match the actual operating conditions. For CPP boilers YARA can select from the variety of different injector types (with adjustable spray pattern and air cooled systems with movable parts in the combustion chamber partly patented), which one ensures the best coverage of the cross- sectional area. In addition with a good temperature detection and control and management program an optimum reduction is realized. Nevertheless it is to be clearly stated that a SNCR system in a boiler is typically is more complex and also more limited in terms of reduction efficiency. Control and management module Normally there is a standalone control and management with PLC and distributed I/Os that normally communicates via Profibus DP or Ethernet. CMM controls, manages, co-ordinates and monitors all process functions to an automatically controlled system. It communicates with the superior control system (DCS) of the plant, receives signals from the plant, takes care of the recipe arithmetic and calculates set points for the reduction process. The local operator interface (HMI) is an industrial PC and a touch screen. All commands to the system are given through the operator terminal. The daily operation is done and Fig. 7 Injector and its installation