Heat exchanging units
Photo 1 – Heat recovery system on thermosiphons,
KSS system of BF No.1 V=1750 m³, Jinan
Iron & Steel Co., Ltd. (Jinan, China)
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Photo 1 – Heat recovery system on thermosiphons,
KSS system of BF No.1 V=1750 m³, Jinan
Iron & Steel Co., Ltd. (Jinan, China)
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Photo 3 – System of waste heat recovery on thermosiphons
at BF No.4 OAO Severstal V=2700 m³ (Cherepovets, Russia)
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The most effective WHRS designs are based on preheaters using thermosiphons (see Photo 1) and on tube heat exchangers (see Photo 2). KALUGIN JSC has acquired a vast experience in designing and supplying the waste heat recovery systems of the above two types.
About 30 Kalugin hot stove systems were equipped with waste heat recovery systems and have already been in operation (the first system was incepted in 2002) in the People's Republic of China in blast furnace units of various capacities.
The following options for preheating of gas and (or) air are introduced in all KSS systems operating in China where only lean blast furnace gas with low combustion heat (<750 kJ/m³) is used for the stove heating in order to achieve the hot blast temperature of 1250-1300ºC with no high-calorific value gas addition:
- Preheating of BF gas and air up to 160-180ºC in the heat exchangers based on thermosiphons (Photo 1) by means of the waste gas heat recovery;
- Preheating only combustion air up to 500-600ºC in two small size KSS (preheaters) specially constructed in the system, see the section "High-temperature preheating of combustion air";
- Preheating the gas up to 160-180ºC in the heat exchanger based on thermosiphons with the heat of waste gases, and preheating combustion air up to 450-600ºC in two small size KSS.
Waste heat recovery units based on tube exchangers are applied in Kalugin hot blast stove systems in India and Ukraine designed by KALUGIN JSC, (see the next page, item 2).
In Russia, the first waste heat recovery system of KALUGIN JSC design for Kalugin hot blast stoves was commissioned in 2005 in BF No.4 OAO Severstal of 2700 m³ (Cherepovets, Vologda region) capacity, see Photo 3. Preheaters in this system are made of thermosiphons.
In 2013 experts of Kalugin JSC designed a unique method of engineering and manufacturing of plate recuperators. The first plate recuperator was put into operation as a part of the waste heat recovery system (WHRS) of the blast furnace no.4 of the melting shop at OAO Ufaleynickel (see the photo 4).
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Photo 4. Waste Heat Recovery System (WHRS) at the blast furnace no.4 of the melting shop at OAO Ufaleynickel |
Technical characteristics of the plate recuperator for blast preheating at BF no.4 at OAO Ufaleynickel:
- Waste gas temperature, ºC - 300 - 600, max. 900
- Waste gas volume, nm³/h - 170 000
- Dust content, g/nm³ - 5,5 - 40
- Volume of preheated air,nm³/h - 65 000
- Air temperature before pre-heater, ºC - 20
- Air temperature after pre-heater, ºC - 300
- heat recovery to the blast furnace by heating combustion air up to 300ºC and higher;
- saving of expensive coke;
- reduction of heat emission into the environment;
- increase in productivity of the blast furnace and costs reduction of end products.
The payback period of WHRS is 5-8 months.