Evotech Pvt. Ltd., Sister Concern of Evcon Technologies, Providers of Evcon Turbo TMT System
Kalugin Shaftless Hot Stoves for Blast Furnaces (KSS)
Kalugin Shaftless Hot Stoves for Blast Furnaces (KSS)Kalugin shaftless hot blast stove with a small diameter pre-chamber at the top of the dome has become the further development of the dome combustion concept. Gas is combusted in the ceramic burner device of “pre-chamber” type where the jet-vortex flow of gas and air is arranged in the vertical axis of the stove.

Annular headers of gas and air are arranged inside the brickwork of the KSS pre-chamber and the latter is independently supported on the dome shell. Such a design has been incorporated for the first time in BF No.1 of Satka Iron-Melting Works in 1992, and the above hot stove has been operating failure-free up to the present moment.

Numerous trials were carried out at special combustion and aerodynamic test facilities for several versions of pre-chamber burner devices. According to the acquired data, the most reliable and suitable design of the pre-chamber burner was selected from the viewpoint of technical parameters, and simplicity and reliability of performance of the refractory lining as well.

Furthermore, a method of 3D numerical computer calculation has been developed based on those tests, a detailed comparison of calculated and experimental results has been made and an excellent correlation was established. At present, calculations of all pre-chamber burner devices of Kalugin hot blast stoves is made based on this 3D numerical computer calculation method.

Jet vortex of gas and air in the pre-chamber ensures intensive and uniform mixing & combustion of gas and the process of combustion is over in the middle part of the dome before entering the checker-work. The optimum degree of jet vortex is obtained experimentally and can also be verified through theoretical calculations. Thus, unevenness of distribution of combustion products across the checker-work surface does not exceed 3-5%.

Kalugin Shaftless Hot Stoves for Blast Furnaces (KSS)Pre-chamber burner design for each KSS is of tailor-made engineering, as well as that of the optimum number of nozzles, their location and angle, gas and air velocities and the degree of jet vortex are also calculated individually. Based on the data obtained, the patterns of gas combustion, temperatures and flow distribution are prepared and subsequently engineering of the refractory lining and steel shell is carried out.

It is obvious that gas combustion starts in the pre-chamber and completes in the top part of the dome so that before entering the checker-work, the gas is almost burnt out having the content of carbon monoxide max 50 ppm. When gas is moving down the checker-work, after-burning of remaining carbon monoxide occurs and at the outlet of KSS the content of CO is less that 20 mg/m³. Hence, the ceramic burner system of the pre-chamber ensures a very intensive mixing and instant combustion of gas owing to the jet vortex flow of gas and air.

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Jet vortex flow distribution may be different for Kalugin hot stoves of different thermal capacities. Research work carried out in the operating KSS with oxygen (O2) content in exhaust waste gas in the range of 0.3 to 5.1% during full thermal capacity operation have shown that the jet-vortex burner ensures the content of carbon monoxide (CO) of 0.0016%, or about 20 mg/m3, which is 5 times less than the European standards. The Kalugin ceramic burner performs better than the most commonly used slot-hole ceramic burner of DME design (Germany).

Kalugin Shaftless Hot Stoves for Blast Furnaces (KSS)Since there is no pulsating of combustion, it is possible to enhance operating modes of KSS without great pressure fluctuations and vibrations, and therefore, damage to brickwork and structures is avoided.

Hydraulic resistance of the hot blast stove is insignificant and a normally available pressure of gas (4.0-5.0 kPa) at the burner inlet is sufficient for full capacity operation.

Jet vortex of gas and air in the pre-chamber of Kalugin hot blast stove ensures an even combustion of gas and subsequent distribution of flows of combustion products across the checker-work surface and requires no adjustment of the ceramic burner before commissioning. Refractory lining of most of the parts of KSS is quite simple except that of the pre-chamber.

1 – Hot stove with the internal combustion chamber;
2 – Hot stove with the external combustion chamber (such as Didier-Werke);
3 – Kalugin hot stove

Kalugin Shaftless Hot Stoves for Blast Furnaces (KSS)Since there is no the direct impact of flame on the brickwork in KSS, local overheating is avoided and this also provides a symmetric distribution of temperatures along the dome, checker, refractory lining and steel shell. Hence, the thermal stress on all design elements is reduced significantly and the service life of the stove is improved.

As measurements have shown, the average level of temperatures in the pre-chamber brickwork is low (about 900ºС on the average), and fluctuations in temperatures of the brickwork between the gas and blast periods are close to fluctuations in temperatures in the brickwork of the ceramic burners of the first shaftless hot stove with the annular pre-chamber (stove No.4 (23) of BF4, NTMK) which has been operated since 1982 without capital repairs and is still in a good condition. This allows us to determine long term service life of the pre-chamber brickwork, and thus the Kalugin stove lifetime is specified by the service life of the silica dome, which reaches 30 years without reline.

Design of the dome proper also promotes a longer service life at high temperature operation because the wider part of sphere above the checker-work passes to the conical part and further to the narrow neck accomplished in the ceramic burner dome, which has a much smaller radius and operates at relatively low temperatures. The diameter of the KSS dome having an independent support of its brickwork on the shell, as compared with the typical hot stove, is only slightly wider, and therefore Kalugin hot stoves can be fit well into the dimensions of existing stove units in case of their modification into a shaftless stove unit.

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Cut-off valves of gas and combustion air were installed in the dome area in the first Kalugin dome combustion stove. Presently, new arrangement and technological solutions are developed, in which all technological equipment of KSS system (hot blast valves, cut-off and control valves of gas and air) is located either on the existing maintenance platforms at the bottom, or on new platforms in the upper part of the shell. As a rule, all equipment is located on one side of the hot stoves system and this reduces the space for its arrangement. Technological equipment of KSS is serviced with lifting equipment installed in the Stove House. In general, the operation process of KSS practically does not differ from the operation of conventional hot stove system.

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