Objective The project is to recover waste heat from dust laden stack gases and use it to heat offices, laboratories, workshops and stores.The quantity of heat is 968 kW and the temperature of gases 110 deg. C.Problems were encountered due to :- cracking of the stainless steel panels due to chloride induced stress corrosion and- apparent incorrect curring of the mastic cement used for heat transfer between the duct and the panels. A K factor of 12 Kcal/m2 deg. c/h only has been achieved when a K factor of 20 Kcal/m2 deg. c/h was expected.Stainless steel panels were removed and replaced by carbon steel panels. Mastic cement was also replaced but no improvement on the K value was noted.It results from the pilot experimentation, that the heat produced by the full size project, 466 kW (TH), would only meet average and not peak demand and as demand for heating has been reduced by economy measures, the TOE saving is now estimated at 70 TOE compared to 250 TOE in the forecast. The payback time should be 6,17 years, which is not acceptable for an industrial project. This made the project uneconomic.It has to be noted that a mastic cement with a better heat transfer could make the concept viable.The Castlemungret cement plant kiln produces 183,300 kg/hour of combustion gases at 320 deg C.- 50% of this quantity is used to dry raw materials- 20% to dry coalOut of the 30% left, say 65,705 kg/h it is contemplated to recover 968 Kw. Normally ; the gases go to a tower where their temperature is reduced down to 110 deg C. They are heavily loaded with dust, so it is not possible to send them into a heat exchanger.For this reason the proposed heat exchanger is fixed around the gas duct before the treatment tower. A conductive mastic has been used to ensure a sufficient heat transfer between the duct and the heat exchanger ; as the K transfer coefficient is only of 20 Kcal/m2 deg. C/hr, a large exchange surface is required. A 196 m2 heat exchanger has been calculated which should ensure an outlet water temperature of 90 deg. C for an initial temperature of 65 deg. C. The gas temperature should go down from 310 deg.C to 275 deg. C. It has been planned before going ahead with the196 m2 project, to set up a pilot scheme of 10,8 m2 of heating panels and dump the heat through a water cooled heat exchanger. Programme(s) ENG-ENALT 2C - Programme (EEC) of demonstration projects relating to the exploitation of alternative energy sources and to energy saving and the substitution of hydrocarbons, 1983-1985 Topic(s) 3.2 - INDUSTRY Call for proposal Data not available Funding Scheme DEM - Demonstration contracts Coordinator IRISH CEMENT LTD EU contribution No data Address STILLORGAN ROAD STILLORGAN CO Dublin Ireland See on map Total cost No data
