OCR Text |
Show The acid and alkali tanks are calibrated so that their contents may be measured when preparing the dilute solutions.In addition, calibration points are provided in both lines to enable the flow meters to be recalibrated at regular intervals. A sample point is provided on the drain of the model to enable collection of a sample of the effluent. By titrating this sample against the original alkali solution the equivalent excess air can be calculated and used as a final check on the acid and alkali flows. ACID/ALKALI MODELLING AS A COMBUSTION SYSTEM DESIGN TOOL Acid/alkali modelling is often used to investigate operational problems with existing combustion systems. The solutions which are determined can then be applied on the full size plant. The real value of acid/alkali modelling, however, is as a process design tool. The flame characteristics required by the particular process for which the burner is to be designed are reproduced on the model. From a knowledge of the aerodynamics and mixing of the system, the fuel burn out and heat transfer is then calculated. Provided these meet the system requirements, detail design may proceed, otherwise the model system is modified until the plant requirements are satisfied. Once the basic design has been completed using the techniques described above, the detail mechanical design is undertaken. Equipment specifications are prepared and detail drawings made. An example of the use of Acid/Alkali modelling as a practical design tool is the work undertaken in connection with re-burnering a lime kiln to burn natural gas with a liquid fuel firing standby system. -14- ^ |