OCR Text |
Show for ~any years, successfully applied oxygen to a wide range of furnaces and kilns, not only in the UK, but worldwide. The alternative methods of applying oxygen fall into the two main categories of: (a) Oxygen enrichment of combustion air utilising conventional air-fuel burners, and stokers. (b) Replacement of existing air-fuel burners by oxy-fuel type burners. In the case of the domestic waste incinerator where no burners as such are used, the application would be to increase the combustion capability of the existing air flow by the injection (as in (a) above) of additional oxygen as and when throughput conditions demand. In chemical waste incinerators the application of oxygen may be as in (a) or (b) above, depending upon the particular situation. By replacing a conventional air/fuel burner with an oxygen-fuel burner the flame temperature can be dramatically increased and the products of combustion are greatly reduced (Fig.l). The flame temperatures shown in Fig. I are based on the adiabatic flame temperature for pulverised coal fired at a stociometric ratio. The actual flame temperatures will, in fact, be slightly lower due mainly to heat losses to the burner cooling system and firing even slightly sub or over stociometric ratios. Both of these effects lead to an increase in furnace efficiency. This gives the option that for the same heat input to the furnace there will be an increase in output or, by reducing the heat input, the existing furnace output can be maintained. As can be seen, this adds greatly to furnace flexibility, enabling the furnace operation to be tuned to meet production or fuel saving demands. 3. BURNER DESIGN AND DEVELOPMENT Air Products has been designing, developing, supplying and operating water cooled oxygen-fuel burners for both gaseous and liquid fuels for over 20 years. The design of the oxygen-pulverised coal burner is based on Air Product's patented -Bundle Burner- with modification to accept pulverised coal (Fig.2). This design of burner is highly reliable and well proven in the field. The modifications to the burner involve replacing the central gas tube with a set of concentric tubes, one of which conveys the pulverised fuel. The remaining tubes act as barriers to prevent pulverised fuel mixing with oxygen in the burner should the central conveying tube wear through. The current design allows for firing up to a maximum of 5.3 Mw on either oxygen-natural gas, oxygen-pulverised fuel, or indeed the burner can also fire in the oxygen-natural gas-pulverised fuel mode enabling the heat input to be maintained when firing with low grade fuels. The turndown of the Page 3 |