OCR Text |
Show measured by a flow sensor and differential pressure transducer in the case of oxygen and natural gas and an Endress + Hauser 6ranucor unit in the case of pulverised fuel. The actual measured flows are compared with the desired flows and if there is an error of more than ± 1~ the system will alarm. As can be seen the control loop could be closed relatively easily to give a proportionating system if required. There are a number of other modifications that could be made to the control system that may give operational benefits. These include the ability for plant personnel to enter the calorific value of a pulverised fuel and the system would automatically set fuel and oxygen rates to give the required thermal input of 5.3 Mw, the expansion of the system to chec~ running times and impart maintenance information and also the expansion to allow information other than alarm messages to be printed for analysis. These modifications, depending on customer requirements, may be evaluated in the later stages of the project. 5. FUTURE DEVELOPMENT The burner that has been installed is rated at 5.3 Mw, a smaller 2.3 Mw prototype burner has already been built and proved to run effectively. As part of the development project a 10.6 Mw burner may be built. There is no reason why a burner of any size cannot be built providing there is a transport system that can supply a steady flow of pulverised fuel. As mentioned previously, there are a number of modifications that could be made to the control system and these will be evaluated over the next year. Extensive monitoring is to be carried out to determine the flue gas composition with varying fuels. 6. OTHER APPLICATIONS There are a number of environmental advantages due to firing with oxygen-fuel and oxygen enrichment techniques which, with the increasing emission regulations, are becoming more advantageous. The great reduction in waste gas volume reduces the load on waste gas handling and cleaning systems, and due to reduction in gas velocities less materials are carried over into the waste gas systems. This has been particularly beneficial in the lead smelting and processing industries where dust carryover includes lead - this is both harmful and effectively results in lost production. The reduction in dust emissions can also be of benefit in the cement industry through the application primarily of oxygen enrichment techniques. The levels of NOX have been measured on oxygen-fuel systems and found to be 20-30% of the levels of those normally found on similar high temperature processes. The use of a dense phase transport system for oxygen-pulverised fuel firing ensures that the minimum amount of air-bound nitrogen is introduced into the process, thereby ~eeping NOX levels as low as possible. Page 8 |