Objective
The Sept-Fons Foundry ensures the production of gray cast iron owing to a hot-blast cupola furnace (400 deg. C). The purpose of this project is to overheat the whole blast (up to 950 deg. C in nominal operation) of this industrial cupola furnace by means of a plasma torch. The conventional solutions consist in recovering heat with an exchanger in order to obtain a hot-blast the maximum temperature of which is on the order of 650 deg. C. The use of a plasma torch on a foundry cupola furnace and the utilization of high temperatures are the innovations of this project.
The economic profitability of the project concerns the primary energy savings through the virtual suppression of new cast iron and oxygen and the reduction the coke rate one one hand and the reduction of the melting bed cost, on the other hand. The main advantages of this solution are: (i) quick reaction after starting and a flexible increased cast iron flowrate from 20 to 29 t/h, depending of the torch power utilized; (ii) control of the installation without additional personnel; (iii) very good reliability of the aerospatiale system, 99% availability with regard to the running time. Since the lst of January 1990, this installation (4 MW) has been used industrially at 700-800 deg. C and has produced 190 000 tons of liquid iron.
ADVANTAGES :
- Very favourable gain in materials : FF 113/t
- Electric power consumption of the torch : 88.61 kWh/t at 750 deg. C
- Increased flowrate of liquid cast iron (up to 29 t/h) depending on the torch power, i.e. a gain of 33%.
- Increased temperature of the cast iron at the taphole : 25 deg. C min. (i.e. 1,535 to 1,545 deg. C)
- Increased carbon pick-up rate in the cupola furnace : from 0.8% without torch to 1.77% at 750 deg. C in the heightened cupola furnace and with torch
- Virtually no oxygen (except for starting th cupola furnace at the beginning of the week and in case of a long stop)
- improved fire losses :
- FeSI : from 26.5% without torch to 19% with torch
- FeMn : from 27.8% without torch to 4.23% with torch
- Versatility of the system :
- quick reaction after starting with melting bed change : 30 mn
- quick reaction after an intentional discontinuation: 5 mn
- increased cast iron flowrate : from 20 to 29 t/h, depending on the torch power utilized
- control of the installation without additional personnel
- utilization of usual refractories
- Reliability of the plasma system : 99% availability with regard to the running time.
DISADVANTAGES :
- No important gain in coke : 0.2%, major consequence: no significant reduction of the dust released in the atmosphere (however, the cupola furnace is now free from dust).
- The tests of product injection at the location of the nozzles did not give the expected results. The improvement of the injection in this field can be considered only within the framework of very specific applications.
- In order to optimize the economical operation of the cupola furnace, it was necessary to change its morphology (throat heigtened by 3.5 m.
This unavoldable requirement did not permit to conduct high temperature tests (< 1,000 deg. C) during a representative period of time.
The project consisted in installing 4 MW plasma torch system on the Sept-Fons cupola furnace. The capacity of these units is 360/400 tons a day (80 000 t/yr). Its main activity is the manufacture of cast iron engine blocks.
The hot-blast cupola furnace, equipped with an AEROSPATIALE 4 MW plasma torch intended to overheat the blast and a dry dust removing installation.
The plasma torch system includes mainly:
* the 4 MW torch proper, mounted on the blast pipe leading to the cupola furnace,
* the torch power supply
* the hydraulic system, which cools the water-circulation electrodes,
* the compressed air production system, which sends compressed air into the electric arc.
* a control system
The torch proper consists of 2 co-axial tubular electrodes, cooled (upstream and downstream with regard to the plasma flow direction) and connected by a vortex gas injection chamber.
The arc, initiated by contact by means of an auxiliary starting electrode, is tranferred between the two tubular electrodes owing to the vortex gas injection. Moreover, the latter provides for the motion of the downstream arc foot in order to prevent the electrode from melting. The motion of the upstream arc foot is obtained by means of an auxiliary magnetic field generated by a coil.
The control and regulation system enabling the cupola furnace operator to control all the operational parameters was designed by AEROSPATIALE on the basis of the specifications laid down by AUTOMOBILES PEUGEOT; the overheat temperature is the key parameter for the cupola furnace control: It determines the carbon pick-up which itself determines the melting bed. The operator selects the blast flow rate and temperature, and the regulation system calculates and applies the necessary power supplied by the system.
This regulation method is simple. The clearly designed scopes of the process supervisor enable the present operators (who are the same as those before the installation of the torch) to control this new toolperfectly.
The different phases of the project were as follows :
* Plasma system design, production and start-up,
* Development and testing :
- modification of the cupola furnace for torch (torch interface, blast box, blast flues cooled pipes) and the gas circuit (installation of by-pass on cyclone to allow its cleaning),
- electrical problems (network resonance, adjustment of anti-harmonic filters),)
- plasgmagene air filtration,
* Tests on insertion of chips + coke dust in the jets with phenomenon of accumulation in front of pipes,
* Tests on insertion of briquettes and chips (in form of compressed bricks) into load with excellent results,
* Tests to add silica (2%) to load at mouth in the form of core sand block waste with a 7% silica breakdown efficiency. * High temperature tests (reduction of firing losses in operational) after heightening the cupola furnace.
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
33165 SAINT MEDARD EN JELLES
France