CO-PRODUCTION OF LIQUID IRON AND SYNTHESIS GAS IN SMELTING REDUCTION

Objectif

To develop a process for the co-production of liquid steel and a predominantly sulphur-free off-gas, consisting mainly of carbon monoxide and hydrogen of consistent quality and production rate. The process is based on the additions of iron ore and coal, together with top injection of oxygen, into a liquid iron bath.L%
Oxygen lance design changes meant that a lower O2 flow of 500 Nm3/h could be obtained leading to stable blowing conditions and production of a lower output gas flow rate. To establish steady state conditions with the O2 flow a new set of matched inputs of iron ore, coal and lime were determined following base data experiments involving inputs of DRI, coal and O2. During these DRI commissioning heats, conditions of continuous operation with continuous tapping were fixed with liquid metal discharge periods in excess of 1 hour.
Iron ore input of 720 kg/h and powered coal injection rates of up to 900 kg/h have produced steady state operating conditions giving low iron oxide levels in the slag coupled with CO/H2 rich off-gases of consistent quality and production rate. Continuous steady state operations up to 1 1/2 h have been achieved with continuous metal tapping over limited periods. Metal splash sticking to water cooled surfaces in the off-gas duct and hood prevented further continuous metal tapping, but iron balances carried out at the conclusion of the experiments showed positive iron yields. Operating with lower slag basicities of between 1 and 1. 5 has helped to generate more fluid slags but the problem of continuous slag discharge still exists.
An engineering feasibility study running in parallel with the pilot plant studies, the design and operating criteria for a medium sized smelting reduction plant. In these initial studies on technical and economic considerations. A decision has been taken to detail a plant producing 5 t/h of liquid metal and associated gas sited within an "ideal" iron and steelworks rather than an existing site.
Preliminary mass balances based on the use of a medium volatile granular coal have been determined together with operating costs and a return on the metal and gas make. The design is too incomplete to allow capital costs to be made at this stage in the study. Some preliminary considerations have been given to reactor design to enable continuous operation to continue over a number of weeks and particular attention has been given to minimising slag and metal splash and the removal of the off-gas. A twin-chambered design has been evolved in which a melting chamber is joined to a setting and discharge chamber by a short launder and gas passage. All feeds enter the reaction chamber, but gas and metal are discharged from the settling chamber.
For this study it is assumed that the product gas will not be passed on for chemical synthesis at this stage in the development programme but for economic viability it is essential that the gas be disposed of in such a way that a financial return is realised. Several alternative methods for gas disposal have been considered including power generation, fuel gas, direct selling or simply flaring the gas at source. A layout of the smelting reduction plant and associated raw material handling, metal and gas disposal plants has been drawn up.
This a five phase project scheduled to operate over an 18 month period.
PHASE 1 : PILOT PLANT PREPARATION AND COMMISSIONING STUDIES
The pilot plant, designed to operate with continuous additions of iron ore, coal, oxygen and lime, will be operated over extended oxygen blowing periods with continuous injection of powdered coal and oxygen to establish a base operating practice with balanced process conditions of constant bath carbon and temperature levels. Various coal types and injection heights will be examined, together with varying oxygen lance blowing heights. To trim the bath temperature to the desired operating level, DRI will be added as a coolant through a top bunker discharge system. Phase 1 experiments will take place over a 30 minute feeding period allowing an approach to chemical and thermal stability to take place within the system. The effects of the various coal types on gas, composition and flow rate, dust loading and thermal requirements of the pilot plant will beassessed. Operating experience of the metal and slag notches will be gained together with the testing of the emergency Lhut-down procedures, the computerized data logging system and data evaluation techniques.
PHASE 2 : MAIN PILOT PLANT EXPERIMENTAL PROGRAM
A series of separate experiments, during 12 months of continuous pilot plant operation, will be performed. It is proposed that the excellent results obtained during the previous batch operating campaigns conducted on the 3 T converter can be successfully transferred onto a continuously operating basis.
PHASE 3 : DATA EVALUATION
PHASE 4 : REPORT PREPARATION
PHASE 5 : ENGINEERING STUDY
This phase runs parallel with the main pilot plant work and consists of a detailed engineering feasability study for a proposed intermediate sized works - based smelting reduction plant.
The project work is being carried out using the 3 T capacity continuous smelting reactor located at Teesside Laboratories.
The process consists of adding iron oreand coal, together with oxygen into a molten iron bath at such feed rates to maintain chemical and thermal equilibrium.
Iron ore and coal may be added in lump or powder form, either separately in, physical mixes, or in briquette form. Oxygen is injected at high pressure through a convergent-divergent nozzle to interact with the liquid bath surface at sonic velocities. The reacting species produces co-products of liquid iron and gas, consisting mainly of carbon monoxide and hydrogen. The British Steel Corporation holds several patents protecting the process, covering the U. K. , Europe, U. S. A. and South Africa.

Programme(s)

ENG-LIGASF C - Financial support for pilot industrial projects and demonstration projects (EEC) relating to the liquefaction and gasification of solid fuels, 1983-1985

Thème(s)

1.1 - GASIFICATION

Appel à propositions

Data not available

Régime de financement

DEM - Demonstration contracts

Coordinateur

British Steel plc

Contribution de l’UE

Aucune donnée

Adresse

Moorgate
S60 3AR Rotherham
Royaume-Uni

Coût total