OCR Text |
Show -greater than 10/1 turn down ratio without losing fuel/oxygen mixing efficiency -low NOx formation A comparison of controllability of various combustion processes is provided in Table 1. This table includes the combustion chemistry and the engineering principles for introducing oxygen by two distinct oxidizing gases (in the simple version, oxygen and air) in each stage of the Pyretron combustion process. The Pyretron combustion system control is designed to handle all of the above mentioned parameters by accurate flow control utilizing programmable logic controllers having software based on the equations in Table 1. This software contains an algori thm which optimizes combustion throughout the entire heating and/or melting cycle based upon temperature measurements. When measurement of temperature is not practical, the system can use other secondary process parameters such as KWH consumed in the case of an EAF application. SUMMARY OF THE EFFECTS OF THE PYRETRON APPROACH ON FLAME CHARACTERISTICS LUMINOSITY - The flame structure has greatly improved luminosity because of activated pyrolysis of the central portion of the fuel which occurs in the first increment of staged combustion. EXCESS OXYGEN OR AIR - The improvement in mixing controllability by utilizing a parallel staged combustion technique reduces the need for the excess oxidizer which is usually required in conventional system to compensate for mixing deficiency. TEMPERATURE - The ability to vary the amount of oxygen essentially without limit so as to control temperature and provide flame stability yields a combus-· tion system with a temperature range from 1600 F to 5000 F. This means that the same system can deliver low temperatures for heating in the fashion of an air/fuel burner and high temperature for melting in typical oxy-fuel applications. FLAME STRUCTURE - With the ability to control each of the constituents of combustion, the flame structure can be varied from big, bushy and luminous to high velocity and impingement. 176 CHEMISTRY - Because the chemical oxygen is introduced into the center of the flame, it can always be controlled so that its complete consumption is assured. Therefore, the flame chemistry can be varied widely from oxidizing to reducing based on heating process requirements and without resulting in process flame temperature reduction. CONTROLLABILITY - With the ability to manage all of the critical flame characteristics, the PYRETRON system can track changing process heating requirements to obtain the best use of fuel, oxygen and process time with the least negative effects on the product. SCOPE OF APPLICATION The Pyretron combustion method and several new high temperature heating and melting methods based on it have received U.S. Patent office approval. Two lines of combustion products using the PYRETRON concept have been developed. PYRETRON I is a line of customized combustion systems designed for applications where preheating of combustion air cannot be justified. PYRETRON II uses combustion air which may be preheated up to 20000 F and is designed to increase the efficiency of the PYRETRON I system even further in cases where recuperation is justified. The PYRETRON I and II methods of controlling heat input have made it possible to provide a combustion system which follows the heating needs of many high temperature industrial processes. In addition, the PYRETRON ability to change the heat flux from the flame to the load and to change the combustion product chemistry makes the system especially beneficial in applications where the load and the furnace are sensitive to the temperature and chemistry of combustion products. PERFORMANCE IN EAF MELTING - Steel melting applications are an area wherein oxygen is much utilized today due to the insensitivity of the process to local overheating, oxidation and decarburization of product by the flame pattern. An erroneous impression has been created that the flame of an oxy-fuel burner is an appropriate source of energy for such applications as melting of steel scrap, copper and even aluminum. In reality the oxy-fuel burner is a very poor heating device whether or not its cost of operation is considered. The oxy-fuel burner exhibits the extreme effects of oxygen utilization in that the flame becomes very small in volume because of the in- |