| OCR Text |
Show As part of the ongoing trials program measurements will be made of the overall furnace and combustion efficiencies when firing conventionally and on oxygen-natural gas and oxygen-pulverised coal. One problem that is not encountered with an oxygen-gas burner is that of wear due to fuel flow. Because of the abrasive nature of pulverised coal, attention has to be paid to the problem of wear within the burner. The central pulverised fuel transport tube is manufactured from schedule 80 steel giving a larger than normal wall thickness which should slow down the speed at which the tube wears through and give an acceptable transport tube life. However, due to the problems that may be encountered if the pulverised fuel was to come into contact with the oxygen within the burner at any place other than the designed location, it was decided to place two further concentric tubes around the central transport tube, thereby giving three walls to be worn through before oxygen and pulverised fuel can come into contact. Regular inspection of the central pulverised fuel transport tube by manual retraction would ensure that any breakthrough would be noticed and dealt with before any hazardous situation could arise. This method works well although it is felt that it can be improved upon significantly. By capping the ends between the central pulverised fuel transport tube and the first concentric tube this space could be pressurised. By monitoring this pressure via a pressure switch the moment at which the central tube wears through may be detected. This has been incorporated into the burner design, although not yet tried in the field. This method of wear detection will obviate the need for monthly inspections on the burner central tube and will provide an automated wear detection system and will be tested later in the life of the project. 4. CONTROL SYSTEM Air Products is committed to engineer systems to extremely high safety standards. The safety interlocking and safe operation of oxygen-gas burners have been well proven over many years of operation. The oxygen and gas flow control trains used in this project are designed to give safe and accurate operation. Both systems have valve proving, supply pressure failure and flow metering with high and low flow alarms. There are no standards that relate to oxygen-pulverised fuel firing, so consideration was given to various standards relating to the storage and use of pulverised fuel. Three main documents were used - German Standard VOl 3673, American Standard NFPA85F and the UK Code of Practice 1017. By taking salient points from each of these documents it was possible to draw up a mode of operation which was confirmed as being safe at a Hazard and Operability Review (HAZOP) meeting between both contractors and interested parties. Page 6 |
