Waste Heat Recovery For Steel Refining
1, Main waste heat resources in steel metallurgy (classified by temperature)
1. High temperature waste heat (>500 ℃) - high-value and easy to recover
Source: Coke oven raw gas (800 ℃), converter flue gas (600-800 ℃), steel slag sensible heat (>600 ℃), electric furnace/reheating furnace flue gas (800-1200 ℃).
Utilization methods: Waste heat boiler produces steam for power generation, preheats gas/combustion air, and recovers waste heat from steel slag.
2. Medium temperature waste heat (150-500 ℃) - large amount, utilization rate needs to be improved
Source: Sintering flue gas (350-400 ℃), hot blast furnace flue gas (250 ℃), steel rolling heating furnace flue gas (200-400 ℃).
Usage: Preheating air/gas, ORC low-temperature power generation, steam production.
3. Low temperature waste heat (<150 ℃) - difficult to disperse and recover
Source: Blast furnace slag flushing water (80-90 ℃), cooling tower drainage, low-temperature flue gas, equipment cooling water.
Usage: Factory heating, domestic hot water, preheating process water, ORC power generation.
2, Mainstream waste heat recovery technology and application scenarios
1. Coke oven process: waste heat recovery of rising pipe raw gas
Technology: The rising tube heat exchanger recovers the sensible heat of 800 ℃ raw gas and produces medium and high pressure steam (≥ 4.0MPa) or superheated steam above 400 ℃.
Benefit: Replacing coke oven gas heating furnaces, more than 100 coke ovens such as Baosteel and Shougang have been applied, creating millions of annual benefits.
2. Ironmaking process: utilization of residual pressure/heat from blast furnace gas
TRT residual pressure power generation: Recovering blast furnace top pressure (0.2-0.3MPa), high power generation efficiency, generating 30-40kWh of electricity per ton of iron, and significant annual emission reduction.
Blast furnace gas waste heat boiler: Low calorific value gas (accounting for 53% of waste heat) is used for supercritical power generation, with an efficiency of 44%+and an annual power supply of over 1 billion kWh.
3. Steelmaking process: Converter flue gas/steel slag waste heat recovery
Converter flue gas waste heat boiler: recovers 600-800 ℃ flue gas, produces steam and connects to the grid; The explosion-proof system solves the problems of explosion and dust accumulation, and increases steam recovery by more than 40%.
Steel slag sensible heat recovery: 1500 ℃ molten steel slag waste heat recovery, with a recovery rate of over 80%, can generate electricity or steam.
4. Sintering/rolling process: recovery of waste heat from flue gas
Sintering waste heat boiler: recovers 350-400 ℃ flue gas, produces medium pressure steam, and 75-182kg of sintered mineral steam per ton.
Heating furnace flue gas preheating: Preheating combustion air/gas with flue gas at 200-400 ℃ can reduce fuel consumption by 20% -30%.
5. General technology for medium and low temperature waste heat
Organic Rankine Cycle (ORC): Suitable for 150-300 ℃ heat sources, generating 10kWh+of electricity per ton of steel, with a return on investment of 3-5 years.
Heat medium heat exchanger/heat pipe: Gas gas/gas-liquid heat exchange, preheating air/gas, compact and efficient.
3, Core benefits (taking a 5 million ton/year steel plant as an example)
Energy saving and cost reduction: Waste heat power generation replaces purchased electricity, saving tens of millions of yuan in annual electricity bills; Reduce fuel consumption by 15% -30%.
Significant carbon reduction: for every 1GJ of waste heat recovered, 80-100kg of carbon reduction is achieved; the annual reduction of CO ₂ is hundreds of thousands of tons.
Energy self-sufficiency: Waste heat power generation accounts for 30% -50% of the plant's electricity consumption, improving power supply stability.
Comprehensive utilization: Waste heat heating covers the factory area/surrounding communities, saving thousands of tons of standard coal annually.
4, Implementation Path (Four Stages)
Thermal balance audit: Identify residual hotspots, temperatures, and flow rates throughout the factory, and determine recycling priorities.
Priority high temperature: first build coke oven/converter/sintering waste heat boiler TRT, Supercritical gas power generation.
Integrate medium and low temperature: ORC, preheating system, waste heat heating/steam supply.
Intelligent control: AI heat flow monitoring+optimization, realizing heat flow visualization, fault warning, and energy efficiency closed-loop.
