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Contenido archivado el 2022-12-27

BLAST FURNACE SLAG BENEFICIATION BY USING INNOVATIVE ENERGY SAVING TECHNOLOGIES, THUS REDUCING GLOBAL CO2-EMISSIONS

Objetivo

For the first time in Europe CIMENTS LAFARGE will set to work a grinding plant devoted to granulated B.F. slag beneficiation. Using its hydraulic properties at adequate fineness, it is able to substitute cement in specific applications, thus saving clinker production energy and related CO2 emissions.
Slag grinding needs a very high energy level, process optimization by using energy saving equipments is a major task. C. L. will use the new LOESCHE vertical mill designed for slag application, i.e. equipped with precompacting and grinding rollers and the LDKSZ high efficiency classifier.
By separate grinding of pure B.F. slag and mixing afterwards with cement and /or fly ash, etc... C.L. will look for optimizing the hydraulic properties of each component.
After a 4 year rise the production level would reach approx. 300000 t/year. At this rate the expected energy saving is over 21000 TOE/year and the payback time is approx. 9,6 years.
Grinding shop start up on 02.02.95.
Tentative performance tests on 21, 22 and 23.03.95 and on 12, 13 and 14 .04.95. According to present registered operations, grinding shop is able to produce ground slag from 2800 to 4800 BLAINE. Up to now, finer products have not been looked for.
PERFORMANCE TESTS RESULTS :
- average throughput : 51,0 t/h (dry basis)
- average fineness : 3290 BLAINE (instead of 3500 BLAINE)
- absorbed power : 28,36 kWh/t mill motor
0,18 kWh/t classifier motor
so 28,54 kWh/t in total
CONNECTED FIGURES AT 3500 BLAINE :
- throughput : 47,64 t/h
instead of 48 t/h, LOESCHE dry basis guarranty
- absorber power : 30,30 kWh/t
instead of 24,7 kWh/t, LOESCHE guarranty
COMPARISON WITH COMMISSION CONTRACT FIGURES :
- absorber power design estimation
after optimisation : 23,3 kwh/t (mill + classifier)
accounting a reasonable bonus between
guarranty and estimated optimum
- difference with corrected
absorbed power : + 7,0 kWh/t or + 30,0%.
Keeping constant other contract power figures, total power consumption of grinding shop becomes 40,0 kWh/t (measuring and recording of the grinding shop only is to be available nextly) instead of 33,0 kWh/t in the contract.
Last recorded data (June 95) for total plant (slag reclaiming shop, grinding shop, fuel storage and preparation, groung slag storage, mixing and bulk delivery shop, ancillaries and control room) are :
- power consumption : 43,52 kWh/t
- thermal consumption : 476,5 Mj/t
Difference in power consumption between the two figures - 3,52 kWh/t is too weak to represent correctly the rest of the plant. Obviously at the present state, total actual power consumption of grinding shop should be lower than 40,0 kWh/t. Ulterior power measurements will confirm these assessments.
Nevertheless, thermal consumption (476,5 MJ/t) seems to be in excess, taking into account during considered period grinding shop has not been operated continuously but only 8h a day with consistant heating period before production starting. Actual value should be lower than contract figure.
Commissioning to be continued to fullfill almost guarantied performances. System economics to be discussed after commissioning completion.
Original project cost estimation valid. Modifications costs (aleas) in a normal range for such an innovative project.
Replication potential has been estimated in the range of 10 to 20 units taking into account the present and potential use of B.F. slag in E.U.
1. INNOVATIVE TECHNOLOGY
Up to now in Europe B.F. slag was ground with clinker for production of blast furnace, composite and Portland composite cements, mostly by ball mill plants. Up to this date separate slag grinding was not performed.
In co-grinding processes, grinding slag at adequate fineness to obtain optimized hydraulic reactivity, leads to overgrinding the other components, particularly limestone and clinker. This leads currently to high water demand and false setting.
Due to moisture, it is not possible to mix more than 15 to 20% of B.F. slag without prior drying. CIMENTS LAFARGE experience let link high BLAINE slag manufacturing is with ball mills technically doubtfull, without speaking of electric consumption becoming dramatic. Due to present european slag poor reactivity it is now necessary to reach this level.
Standard vertical mill design was thought to be energy saving solution. It was experienced by manufacturers and cement producers; the main conclusions concerning slag grinding were : - Difficulty to reach high fineness
- Necessity to transfer to table material bed higher pressure to create adequate comminution
- Necessity to reduce drastically bed thickness to obtain efficiency
- High pressure and low bed thickness lead to unstability (high vibration level), frequent operation
shutdown, high wear and reduced equipment lifetime, and low grinding efficiency. The LOESCHE innovation consists in the following developments :
- Precompassing rollers acting on the material bed before grinding rollers, increasing bed cohesion and grinding efficiency
- New grinding rollers design enabling increased hydraulic pressure transfer
- Substantial increase of hydraulic pressure
- Reduction of table velocity to increase bed stability
- Setting to work a new high efficiency classifier, LDKS Z type, to ensure production finenesses over 5000 SSB to enable, at will, grain size distribution and ROSINRAMMLER slope modifications.
The CIMENTS LAFARGE innovationconsists in separate slag grinding in order to benefit from hydraulic properties of each cement component.
2. OPERATION TECHNOLOGY CONTEXT :
Hydraulic binders grinding for cement manufacturers.
3. ECONOMIC ASPECTS OF THE TECHNOLOGY, COMPARED TO CONVENTIONAL EQUIPMENT :
Compared to conventional ball mill or newly introduced roller press units (or even mixing of the two technologies), necessitating both a separate drying equipment, the investment and production costs are much lower.
Compared to the project unit equipped with the LM 35 S, estimations of investment overcosts are as follows :
- 1,1 to 1,2 for a dryer + ball mill unit - 1,1 to 1,2 for a dryer + roller press unit - 1,3 to 1,4 for a dryer + (roller press + ball mill) unit.

Convocatoria de propuestas

Data not available

Régimen de financiación

DEM - Demonstration contracts

Coordinador

CIMENTS LAFARGE SA
Aportación de la UE
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Dirección
5 BOULEVARD LOUIS LOUCHEUR
92210 SAINT-CLOUD
Francia

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Coste total
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