Co-generation plants are also called Combined heat and power plants. In a cogeneration plant, unlike in a combined cycle plant, steam generated in the Heat Recovery Steam Generator is used for processing in industries.  Co-generation plants are installed in 

industries like fertilizers, chemicals and refineries, where there is need for both steam and power.  Co-generation plants can be designed to any ratio of heat and power depending on the need of the industry.  The schematic of a cogeneration cycle is shown above.  

The process is also depicted by the T– diagram of the above image.  The area A-B-C-D-E-F-G represents the total heat recovered  in the cogeneration  plant.  The  efficiency of heat recovery is very high in co-generation plants, as mainly the loss of heat is only in the flue gasses exiting in the boiler stack.  Lower the gas temperature, higher will be the efficiency of co-generation and co-generation plants are designed for efficiency as high as 90% and more