Objective
The purpose of the project continued from EE/00002/82 is to demonstrate, on an industrial scale, that massive injection of pulverised coal to the tuyeres of a blast-furnace is possible if plasma torches can raise the temperature of the hot blast well above that obtained from standard pre-heating processes.
It is expected that the energy consumed by the plasma torches, in the form of electricity and coal, would be more than compensated by savings made in the consumption of coke, pure oxygen and preheat gas.
Conducted on one of the existing blast-furnace with a pig production capacity of 1600 tons/day production and consumption figures, with and without plasma torches, will provide the basis for determining and comparing the economies of the two systems. The results, when applied to the biggest blast furnaces in Europe with a pig production capacity of 15.000 tons/day, expected are 25% saving. Payback is 4 years.
Tasks and results until 31 December 1987:
1. Preliminary testing:
- testings of a new design of the arc heater - blast furnace (nozzle - tuyere) interface and the coal source in order to prove its reliability on a long term basis
- optimizing the position of the coal injection point to meet the followiing requirements: preheat the coal as much as possible, increase the "reaction time", avoid combustion of the coal in the tuyere and minimize abrasions of the tuyere
- studying the thermal behaviour of the arc heater-blast furnace interface in order to minimize the thermal losses.
The tests have shown the technological feasibility of a massive coal injection with the use of plasma:
- it was possible to inject more than 200 g coal per Nm3 of wind with a lance located at the tuyere mouth;
- the excellent final state of the test device (especially the refractory of the nozzle) is very encouraging.
However, the tests showed also rather high thermal losses of the arc heater - blast furnace interface of the test device. It is expected that these losses can be reduced before putting the demonstration plant into operation.
2. Specific studies, engineering:
- defining the specifications of the major parts of the installation (plasma supply, extension of the coal storage and injection capacities, interface studies, measurement equipments)
- negotiation of plasma offers, placing of orders.
3. Construction:
The extended works concerned the extension of the coal storage and injection capacities, the technical building, the electric auxiliaries (transformers, rectifiers, torch control) and compressors units. Full maintenance of the blast furnace has been made.
This phase was completed in June 1987.
4. Test operation:
Main results are the following:
- after some difficulties, plasma system is now well in operation
- thermal losses of the arc heater-blast furnace interface are very low
- coal injection and measurement devices work well.
1. BLAST-FURNACE. In the case of a conventional blast-furnace, of the type used at Uckange, coke and iron ore are fed into the upper part of the furnace called stack throat. Around the lower part of the stack are fitted a number of tuyeres through which is blown high pressure air preheated to a temperature of 900 to 1300 deg.C.
The hot blast provides the temperature and oxygen required for the combustion of the coke which, in turn, melts the iron from the ore agglomerate. The iron-bearing charge separates into slag, consisting of the sterile parts of the ore and coke scoria, and molten pig which drains into a crucible.
At Uckange, it is also of current practice to inject pulverized coal into the tuyeres where it is ignited by the hot-blast. This allows significant amounts of coke to be saved.
The aim of the project is to boost the injection of pulverized coal by means of electrically powered plasma torches. The added heat generated will raise the temperature of the hot blast, thereby accelerating combustion and improving the furnace's operating efficiency.
2. PLASMA-COAL SYSTEM. The complete plasma generation and coal injection system basically consists of the following equipment:
- Electrical power sources to supply the plasma torches (1 per torch), including on-load power controller, harmonic filter, power factor correction and ancillary equipment power supplies;
- six 1.6 MW plasma torches;
- cooling water supply and piping, including pumps and heat exchangers;
- compressors and blast air feeders;
- modifications required to six of the furnace's existing blow-;pipe circuits;
- Reinforcement of the pulverized coal injection system to increase its capacity from 6 to 10 t/h;
- Test and measurement equipment for operational control and information acquisition.
The basic principle of the plasma torch is the conversion of electrical energy into heat by driving an electric arc through a mass of gaseous material. The volumetric enthalpy of the resulting plasmais up to 5 times higher than that of flames from a conventional burner.
Applied to a blast-furnace, the plasma torches will raise the hot-blast temperature from its present level of 1150 deg.C to more than 1600 deg.C.
Fitted to the Uckange Nr 1 blast-furnace, which has a pig-iron capacity of 1600 t/day, the six plasma-torches would improve the operational efficiency of the furnace and enable 60-65 kg of coke to be saved per tonne of pig-iron, for an additional consumption of 50-55 kg of coal and 150-170 kWh of electricity.
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
57270 UCKANGE
France