lobal
G
SLAG
SLAG
SLAG
GRINDING WITH
MPS VERTICAL
GRINDING
ROLLER MILLS
BY Y ORK ORK R EICHHARDT EICHHARDT
GEBR . PFEIFFER AG
Since 1980 a vertical roller mill MPS 3750 C near Hannover supplied by Gebr. Pfeiffer AG produces cement types CEM III A and CEM III B with a slag content between 40% and 80%. Actually an MPS 5600 BC with 5300kW installed main drive is under erection. The guarantee values for grinding blast furnace slag in this mill are 120t/h at a fineness of 5000cm²/g (Blaine) and 170t/h at a fineness of 5000cm²/g (Blaine). Introduction
Pfeiffer’s MPS vertical roller mill
Gebr. Pfeiffer AG, a medium-sized family business, has been a supplier to the cement, lime and gypsum industry for over 140 years. The company’s product range comprises machines and equipment for the grinding, classification and drying of diverse materials and for slaking quicklime and calcining gypsum, which are sold worldwide. The company, headquartered in Kaiserslautern, employs 260 staff and maintains manufacturing facilities as well as a foundry of its own. Gebr. Pfeiffer AG has an annual turnover of around Euro75m. With over 2000 MPS vertical roller mills in use around the world today for grinding cement raw material, coal, clinker, granulated blast furnace slag, pozzolana, limestone, clay, gypsum and various other materials, the MPS technology represents the company’s major source of revenue. In the cement industry, MPS vertical roller mills grinding cement raw materials and cement or granulated blast furnace slag with installed powers of over 5000kW are currently in operation or on order.
The structure of the MPS BC series, to which all mills producing cement or blast furnace slag powder belong, basically correspo corresponds nds to that of the MPS vertical roller mills that have been used for cement raw material and coal grinding since the 1960s: the statically determinate 3-roller-system, 3-roller-s ystem, which is pressed against the grinding bed by a pressure frame, external pull rods and the hydraulic system, is a characteristic feature of the mill. The grinding rollers can be lifted with the help of the tensioning cylinders during start-up or for maintenance purposes. An SLS high-efficiency classifier classifier sits on top of the grindgrinding zone. The supply of fresh material is integrated in such a way that the fresh material and the grits from the classifier mix well and the material drops onto the centre of the grinding table. The MPS BC model range distinguishes itself from raw mills through its process-related design, which is particularly characterised by the increased grinding force, an adapted, reduced speed of the grinding table and lower gas velocities.
MPS 5600 BC for Tenghui Cement, China. Under erection 120t/h slag 5000 Blaine, 170t/h slag 4000 Blaine (250t/h OPSC 3000)
July 2006
21
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The mechanical design is tailored to the higher abrasiveness of the material to be ground. The nozzle ring and other parts exposed to increased jet wear in the area of the grinding table are made of Ni-hard IV. The area of the classifier is provided with a ceramic lining, and the rotor of the classifier is hardfaced. The wear parts of the rollers and the grinding table normally are made of chromium alloy cast iron and will be hardfaced at a later stage, when knowing the exact wear profile. The hardfacing can be carried out inside the mill without the rollers having to be removed from the mill. The rollers are lifted up for this purpose, and, while it is being welded, the grinding plate is turned with the help of a variable-speed maintenance drive, which is integrated in the gear. Then the rollers are lowered again, driven by the grinding table and welded using several weld heads simultaneously. With an
MPS
2500 BC
2500 BC
2500 BC
2500 BC
country
India
India
Czech Republic
Czech Republic
commissioning
2000
2000
2002
2002
1980
48
97
96
43
clinker (%) blast furnace slag (%)
48
gypsum (%)
4
3
3600
3100
specific power consumption (mill, classifier, fan) (kWh/t)
31
throughput rate (t/h)
specific surface (Blaine) (cm/g)
dust collection in cyclone
4
5
3800
4300
3600
27
31
38
32
22
26
23
21
70
yes
yes
no
no
yes
Table 1, above: MPS vertical roller mill for the grinding of cement and blast furnace slag. Left: References in the cement industry from 1994 onwards.
4250 BC
4250 BC
country
Germany
Germany
Ecuador
Italy
Italy
1980
1980
2002
2004
2004
20
95
67
64
89
75
4250 BC
18
pozzolana (%)
30
6
limestone (%) gypsum (%)
6
5
5
5
3
6
6
4300
3000
4600
4400
3800
specific power consumption (mill, classifier, fan) (kWh/t)
45
29
28
23
34 (guarantee)
throughput rate (t/h)
45
78
118
126
103 (guarantee)
yes
yes
yes
no
no
specific surface (Blaine) (cm/g)
dust collection in cyclone
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52
limestone (%)
3750 C
blast furnace slag (%)
Germany
pozzolana (%)
3750 C
clinker (%)
3750 C
100
MPS
commissioning
GRINDING
22
MPS 5600 BC for 170t/h slag powder like the one currently under erection, downtime for the entire hard-facing can be kept as short as 110 hours, approximately, if work is organised accordingly. The hardfacing is expected at this mill to be necessary each 2000 hours based on a production of 170t/h slag at 4000cm 2/g acc. to Blaine. MPS mills are in operation which are hardfacened more than ten times. In total this leads to comparatively low maintenance costs.
Plant concept The entire grinding plant consists of • equipment for metering, supplying the wet slag to the mill and for metal Table 2: MPS vertical roller mill for the grinding of cement and blast furnace slag.
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be in between just the vertical roller mill or the complete machinery and the electric part of such a grinding plant.
Operating data The first industrial-scale vertical roller mill for slag cement, an MPS 3750 C, went into operation in Hannover 25 years ago [1] and is still in operation. It produces 70t/h CEM III A and 45t/h CEM III B with slag content between 50 and 80% and fineness of 3600cm 2/g and 4300cm2/ g. The cement quality meets all the requirements of the German market. For 100% slag at a fineness of 4100cm2/ g the capacity of this mill is 60t/h. Also newer mills of the MPS BC series produce slag cement and slag powder in this range of composition and fineness. Today more than 20 MPS vertical roller mills of the BC series for slag, cement and binding agents with capacities of up to 150t/h [2-5] are used or under contract for slag powder and the production of virtually all cements of various compositions commonly used worldwide. The mills achieve finenesses ranging from 2000cm2/g to
Above: Grinding of slag. Right: Design of MPS BC cement/slag mill by Gebr. Pfeiffer AG.
extraction upstream of the mill • the MPS BC vertical roller mill • the external material circulation system with a complementary metal extraction system especially aimed at the already dried and liberated pig iron • the process gas routing • bag filter for dedusting and product removal. For drying the wet slag in the mill either process gases like clinker cooler exhaust gases or hot gases from a hot gas generator may be used. Gebr. Pfeiffer AG’s scope of supply may
MPS
4250 BC
16x4250 BC
5600 BC
5600 BC
country
Italy
Iran
China
China
commissioning
2004
100
100
clinker (%) blast furnace slag (%)
29
95
65
pozzolana (%) limestone (%) gypsum (%)
6
5
4000
3000
5000
4000
specific power consumption (mill, classifier, fan) (kWh/t)
45 (guarantee)
18 (guarantee)
38 (mill drive)
30 (mill drive)
throughput rate (t/h)
75 (guarantee)
120 (guarantee)
120 (guarantee)
170 (guarantee)
no
yes
no
no
specific surface (Blaine) (cm/g)
dust collection in cyclone
July 2006
23
Above: a MPS 250 0 BC vertical roller mill at Sagar Cement at Bayyavaram works, India. Table 3, to the left: MPS vertical roller mill for the grinding of cement and blast furnace slag.
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7000cm 2/g in the case of binding agents which contain cement. The operating data are proving, that the sales arguments in favour of the MPS technology for the economic production of slag powder and cement are true. The actual development goes to bigger units with higher capacity. Actually an MPS 5600 BC with an installed power of 5,300kW is under erection. It is guaranteed for 120t/h of granulated blast furnace slag at a fineness of 5,000cm2/g or 170t/h with a fineness of 4,000cm2/g. Start of production is scheduled for spring 2006.
References [1]
Steinberg,
H.,
Hoffmann, R.: Production of
slag
cements
in
a
vertical roller mill, ZKG International
51
(1998)
No. 3, pp.101-109 [2] Jung, O.: MPS vertical roller mills for blended cements,
Wold
Cement
Vol. 20 (1989) No. 9 [3] Reddy, S.A, Reichardt, Y.:
Production
of
slag
cement with an MPS vertical roller mill at the cement plant of Sagar Cements in Bayyavaram, India, ZKG
International
54
(2001) No. 9, pp. 492-497 [4] Reichardt, Y., Link,
Above: Grinding of slag with a MPS 2500 BC at Cemex/RMC in the Czech Republic. Left: MPS 3750 C vertical roller mill at Teutonia AG, Germany.
G., Gilabert, H.: Cement finish grinding with an MPS vertical roller mill at the San Rafael cement plant in Ecuador, ZKG
of MPS vertical roller mils in the production of
International
cement and blast furnace slag powder, Cement
55
(2002)
No. 11, pp. 54-57
International (2005) No. 2m pp.64-69
[5] Reichardt, Y., The use
July 2006
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24
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