Throughout the past 3 years «M Technology» has participated in over than 30 blast furnace reconstruction projects.

Over a dozen of projects were focused on solving one of the most challenging issues of the modern blast furnace process – significant decrease of operating time of standard cooling systems (with the use of untreated water), and subsequently – a fast failure of the cooling staves under the condition of pulverized coal injection.
The efficiency of the cooling system today determines the period of the blast furnace campaign, that is why modern cooling systems are faced with increased requirements to ensure reliability and high operation availability.
What do we understand by a modern cooling system and what are the requirements to it today? The cooling system should provide the following under  the conditions of PC injection:

— efficient heat removal from cooling staves and lining;
— formation and maintenance of a stable skull layer on the lining surface;
— energy efficiency, reduction of heat losses with the use of the cooling system, saving expensive coke;
— reduction of the environmental impact by using closed-loop (zero-discharge) cooling systems or load decrease on the enterprise’s recirculation system;
— extension of the BF campaign up to 15 years.

Using an innovative approach to solving this problem,  modern calculation systems and three-dimensional modeling, “M TECHNOLOGY” LLC has developed a number of measures that have been successfully implemented at  many blast furnaces.
After implementation of the facilities  our company experts monitor the the cooling systems work over the entire  period of the facility operation.

By collecting data on the progress of work, taking into account the experience of the operating personnel, we are constantly improving the decisions made.

We are proud that METINVEST HOLDING has used “M TECHNOLOGY” proprietary system of cooling intensity regulation as a standard solution for revamping and construction of new  blast furnaces.

Among the projects described above, the following ones can be underscored:

BF No. 2, BF No. 3, BF No. 4, BF No. 5 of PJSC “Zaporizhstal”, BF No. 3, BF No. 4 and BF No. 6 at PJSC “Azovstal”, BF  No. 4 of PJSC ” Ilyich Iron and Steel Works “, BF  №5 of PJSC” EMZ”.

BF №2 PJSC “Zaporizhstal”

At Zaporizhstal PJSC BF No.2 it was our company to apply solutions that effectively deal with the negative impact of the pulverized coal injection on blast furnace campaign duration and its energy efficiency.
– Our company performed the following scope of works:
— we were the pioneers to apply an automatic cooling system with the cooling rate control depending on the heat load inside the blast furnace. It was cooling with hot demineralized water, where heat was removed from heated water not through heat exchangers, but by removing steam from a separator drum. This cooling system has 3 operation modes: closed loop cooling with “hot” demineralized water, evaporative cooling with natural circulation, industrial water backup;
– — first ever in Ukraine, copper cooling staves have been installed in the second and third rows of the BF stack. The blast furnace lintel-type design made it difficult to install the copper staves in the bosh. Later on we have found a solution for lintel-type BF #5 at PJSC “EMZ”, but this project has been never implemented due to “EMZ” secession from METINVEST HOLDING;
—highly heat-conductive thick-walled lining was applied at this blast furnace: (in the bosh and 3 stack rows it was made of silicon carbide, above them it was alumina-carbon and chamotte);
— a new pumping station with electric pump units and frequency-controlled engine speed was built;
— a modern Automatic Process Control System was installed.
All above-listed solutions have allowed to prevent the staves from burn-outs and to enormously reduce heat losses from the furnace, resulting in reduction of coke consumption.
Combined application of copper staves, highly heat-conductive lining and automatic cooling system provided formation and maintaining a stable skull layer on the lining surface, but not on the staves, which made possible reliable BF operation and extended the BF campaign.
Basic diagram of the “hot” demineralized water cooling of BF No. 2:

BF№4 PJSC «Zaporizhstal»

The scope of our work related to the BF repair, as well as the solutions taken, were similar to BF No.2 repair, but they had several distinctive features:
— copper cooling staves were installed in the belly zone and two bottom rows of the stack, but the BF lintel-type design made installation of copper cooling staves in the bosh area challenging, so cast iron cooling plates were left in that zone;
— pre-lined cooling staves were first used at this BF (silicon carbide firebricks were inserted into the copper stave prior to installation, the bricks and the staves were dovetailed). This solution allowed to reduce erection time, eliminated the risk of the entire brickwork falling as a result of local destruction, enhanced fixation and contact area of silicon carbide with the stave wall, which significantly increased the heat transfer from the stave to the brickwork, resulting in an effective lining protection and maintaining a stable skull layer.

Copper cooling staves with silicon carbide brick pre-lining:

BF №2 and BF №4 PJSC «Zaporizhstal»

The enterprise intended to increase the pulverized coal injection into the BF hearths and to achieve performance of 180 ÷ 200 kg/t-HM. Therefore it was decided to change-over BF No.2 and BF No. 4 cooling system to “cold” demineralized water closed-loop cooling.
For this purpose our company has developed a project for installation of plate heat exchangers, water/water type, at these blast furnaces, aimed to decrease the cooling water temperature up to 35 ÷ 45°C. A technology of service water flow control depending on season temperature fluctuations and heat load inside the blast furnace was applied in all heat exchangers. This solution allowed up to 50% service water saving in winter time.
After the project implementation the blast furnaces can be operated with 4 independent cooling modes:
— cooling with “cold” demineralized water;
— cooling with “hot” demineralized water;
— evaporative cooling with natural circulation;
— standby cooling with technical water.
Basic diagram of the “cold” demineralized water cooling:

BF №5 PJSC «Zaporizhstal»

During the project execution an automatic cooling system by means of “cold” demineralized water in a closed loop with construction of a new pumping station and a room for plate heat exchangers, water/water type, was implemented.
It was decided to install steel cooling staves, pre-lined with silicon carbide bricks, in the peak heat load areas (bosh, belly and stack rows 1 – 3). Steel staves are an alternative to copper cooling staves, they provide a reliable heat dissipation and ensure efficient cooling of the lining. The main feature of the steel cooling staves is no boundary between the cast-in pipe and the stave body. The cast steel stave material is low-carbon steel with 0.2 to 0.3% carbon content.
It was the first blast furnace in the post-Soviet space, equipped with steel cooling staves.
Steel cooling staves with silicon carbide pre-lining:

BF №3 PJSC«Zaporizhstal»

Pulverized coal injection into the furnace hearth (PCI was put in operation in 2011) led to considerable increase of the thermal load on the cooling system, especially in stressed areas, which resulted in stave damages, BF shell overheating, as well as shell cracks and deformations.
For this reason it was decided to dismantle the blast furnace and to build a new one with the same volume of Vn = 1513 m³ in the same place but on a new foundation.
BF cooling is performed both with technical water and demineralized water in a closed loop.
Process water is used for cooling the furnace bottom, bottom staves, hearth staves, upper stack and top staves, while the bosh, belly, lower and middle stack staves as well as the tap-hole staves are cooled with demineralized water.
Due to high thermal loads on the cooling system, typical for operation with PCI, the furnace is equipped with copper staves in the bosh, belly and lower stack.
In addition, copper staves are installed around the hot metal tapholes. The solution is first ever implemented on the territory of Ukraine, precisely in the framework of this project.
The rest of the staves are traditional cast-iron plate staves.
Both copper and cast-iron staves of the stack have dovetail joints for firebrick installation. Refractory lining is produced by Gongyi AR Co. (China).
The lower part of the furnace is presented with one row of graphitized blocks (production of “Ukrgraphite”, Ukraine), four rows of microporous carbon blocks covered with a ceramic cup. Peripheral blocks are carbon microporous and supermicroporous carbon blocks covered with a ceramic cup. The tuyer zone is lined with sialon-bonded silicon carbide refractory bricks.
The bosh, belly, lower and middle stack are lined with silicon carbide bricks, the stack upper part and the top – with fireclay bricks.
Carbon concrete and silicon carbide concrete are used for filling the space between the BF metal bottom and water cooling pipes.
The gap between the staves and peripheral blocks is filled with cold ramming mass of increased thermal conductivity.
The space between the furnace shell and the staves is filled with unshrinkable mass with low thermal conductivity.

Installation of the hearth and hearth bottom staves:


The following works have been performed under the scope of this project:
— construction of a new pumping station with installation of pumps and heat exchangers in the amount needed to provide stable operation of the cooling system taking into consideration standby pumps and heat exchangers as well as redundancy
— installation and connection of instrumentation (water flow, pressure and temperature sensors) with the signal transfer to the room of the pipemen on duty and to the workstations of BF No.5 water treatment plant engineers;
— BF stack thermocouple installation and connection to the instruments;
— connection of the pumping station switchgear from 1600 kVa transformers of the 4ТП5Д substation;
– — the 4ТП5Д power switchboard modernization with installation of additional switching devices;
— ALT is provided in the switchgear of the designed pumping station both for power supply and for standby units activation;
— automatic process control system:
а) pumping units, heat exchanger ventilators control via Ethernet;
b) DLR network technology to improve the system reliability and fault tolerance;
c) modular replacement of the controller equipment without control interruption;
d) diagnostics of the system equipment and the closed loop connected to PLC;
e) subsystem for the BF No.5 shell temperature display;
f) integrated vibration monitoring of the pump units via Ethernet;
— replacement of cast-iron staves of the bosh and 4 rows of the furnace stack with copper staves (the copper staves are designed with consideration of the furnace profile; the staves are interconnected with flexible metal hoses);
— automatic stack lining erosion control of BFNo.5;
— application of a high-conductive silicon carbide lining for the bosh, belly and BF stack.
A pioneer solution of the copper staves installation at a lintel-type furnace both in the bosh and in the lower rows of the stack was implemented at this furnace.

BF №3 PJSC «Аzovstal Iron and Steel Works»

In the scope of the project the existing shell was replaced with a shell of a self-supporting design, made of modern wear- and heat-resistant materials, with consideration of max 2.0 atm top pressure.
In fact, a new blast furnace was constructed on the existing foundation where the top ring elevation and the HM taphole axes elevation remained unchanged.
The furnace profile was designed with taking into account pulverized coal injection.
The new BFNo.3 profile is characterized by the following features: the bosh height increased, the belly height decreased, the belly/hearth diameter ratio increased; the top, belly and hearth diameters increased. The stack inclination angle remained unchanged and the bosh angle decreased.

The lining of the furnace bottom central part from el. +2,500 was performed as follows:
— the base row is made of graphitized blocks, H = 400 mm;
— four rows of low-porous carbon blocks with the total height of 2,000 mm above;
— one row of microporous carbon blocks, H = 500 mm, above;
— two rows of high-alumina refractories with the height of 1,000 mm up to el. +6,400.
The lining of the hearth walls from el. +4,900 to +10,200 is made of microporous carbon blocks. The hearth working surface is protected with a 400-mm thick ceramic cup.
The lining of the tuyer zone is made of compound aluminium-carborundum refractory blocks shaped correspondingly to the tuyer stock elements, which results in reducing the number of joints between the refractory elements and increasing the lifetime of the lining in the tuyer zone.
The bosh and stack lining is made of refractory bricks:
— the bosh is lined with silicon carbide bricks;
— the belly and the lower stack lining is made of 150-mm silicon carbide bricks (the bricks are dovetailed into the staves) and a hydraulic bonded silicon carbide gunite coating;
—the middle stack consists of microporous alumina-carbon bricks;
— the upper stack – fireclay bricks.
The top is lined with protective water-cooled plates with cast-in fireclay bricks.
The space between the blast furnace shell and the cooling staves is filled with special high-flowable refractory mixture, which ensures high gas tightness of the furnace and shell insulation.
The furnace cone is lined with gunite and steel lining plates. The gaps between the lining plates are rammed in with cast-iron sealing compound.
The furnace cooling is performed with closed-loop demineralized water.
The following works have been carried out for the system implementation:
— construction of a new demineralized water circulation pump station, including installation of pumps and heat exchangers in the amount needed for the stable cooling system operation with taking into account standby pumps and heat exchangers as well as redundancy in case of power cutoffs;
— construction of a new filter station for sea water;
— implementation of the automatic staves cooling rate control system
(М TECHNOLOGY patent No. 105036);
— construction of an external and internal pipeline with installation of shut-off, safety and control valves;
— installation of copper staves in the bosh zone, belly as well as in the 1st and 2nd stack rows;
— installation of one row of steel staves (3rd stack row;
— installation of copper staves in the HM tapholes zone.
The staves are designed as follows:
the lower part of the furnace (bottom, hearth and tuyer zone) up to el. +13,650 are smooth cast-iron cooling staves. The staves are made of cast-iron grade СЧ 15-32 GOST 1412-85, cooling pipes are steel “pipe coils”, Ø 70×8 mm; the staves around the HM tapholes and 7 staves under the tapholes are copper plates with drilled channels Ø 50 mm.
Copper staves with drilled channels Deq = 50 mm are installed in the peak thermal load area (two rows of the bosh, one row of the belly and two rows of the stack).
There is a dovetail slot on the fire side of the plate for lining with silicon carbide bricks.
One row of steel plates made of structural carbon steel 15Л with cast-in straight steel cooling tubes Ø70x10mm is installed above the copper staves.
There are two rows of cast-iron staves with cast-in straight cooling tubes above. Cast-iron grade ВЧ 450-10, DSTU 3925-99, cooling tubes Ø 76×9 mm are made of steel.
Six rows of cast-iron staves with cast-in coil pipes and cooling tubes are installed from el. +29,050 to el. 36,690. Cast-iron ВЧ 450-10, DSTU 3925-99, cooling tubes are made of steel Ø 76×9 mm.
The subhearth water cooling system is designed as follows: 44 pipes Ø 60×8 with a pitch of 250-350 mm between are laid under the bottom plate. The cooling pipes are combined in ten sections and poured-in with carbon concrete.

BF №4 PJSC «Аzovstal Iron & Steel Works»

In the scope of this project copper staves in the peak heat load zones (bosh and the first – fourth stack rows) and steel staves in the fifth and sixth stack rows have been installed, the pumping station has been revamped with installation of pumps, providing the cooling water speed of 2 – 3 m/s. The tuyer zone staves cooling has been changed to cooling with closed-loop demineralized water. The cooling rate in the stave coil tubes increased up to 2 – 3 m/s.
Heat exchangers of water/air type have been installed for cold demineralized water cooling, that completely excludes sea water consumption.
The following systems have been implemented: automatic cooling systems for the bosh, stack and the tuyer zone; control system for thermal load on the staves; control system for the lining condition in the stack and bosh; automatic stave burnout detection system.
To compensate thermal loads between the staves, made of different materials (copper, steel, cast-iron), metal hoses with silicone coating are used.
All cooling staves were fitted with dovetail joints for lining before installation.
Two bosh and four stack rows (copper staves zone) as well as two rows of steel staves are lined with nitride bonded silicon carbide bricks (SiC content ≥ 70%, SI3N4 ≥ 21%), with lining thickness equal of 190 mm and more.

BF №4 PJSC «Ilich Iron & Steel Works»

– An automatic cooling system by means of cold demineralized water was developed within the framework of this project for the bosh, lintel and belly. The furnace stack was made in the form of “stack panels” where evaporative cooling system with natural circulation was kept. Process water supply is provided as emergency cooling for both systems.
According to the project of automatic bosh, lintel and belly demineralized water cooling system, the following works have been carried out:
— installation of copper staves in the bosh;
— construction of a new circulating pump station of demineralized water with installation of pumping units and frequency convertors for cooling rate control depending on heat load;
— installation of water/water heat exchangers for heat dissipation from demineralized water by means of process water;
— installation of a control valve on the industrial water pipeline, which allows changing the volume of industrial water supply to heat exchangers depending on the ambient temperature and thermal load in the blast furnace. This solution allows to save up to 400 m³/h of process water in winter and has been applied first ever in Ukraine in this project;
— installation of a modern automatic process control system.
Demineralized water manifold: