Introduction to the Gas Purge and CO Emission Reduction Technology
Regenerative combustion technology has been widely applied to various types of industrial furnaces and kilns. This combustion technology allows low-calorific value gas, such as blast furnace gas and producer gas, to be used directly for billet heating through regenerative technology without the need to mix with other high-calorific value gases. Furthermore, regenerative combustion technology can achieve extremely low-temperature flue gas emissions, maximizing waste heat recovery to achieve energy-saving effects.
However, heating furnaces using regenerative combustion technology commonly face the following problem:
As shown in the figure, each time the reversing valve switches, a set (side) of burners transitions from combustion state to exhaust state. The gas between the reversing valve and the regenerative burners is then drawn into the exhaust system. This area is referred to as the "common area" (the area marked in the figure).
As long as regenerative combustion technology is used in heating furnaces, this issue commonly exists. This is because regenerative combustion relies on the frequent switching of reversing valves to store heat using the regenerative media inside the burners and achieve maximum heat recovery. Therefore, the "common area" between the reversing valve and the burners inevitably exists.
This brings about the following issues and potential risks:
1. Gas is directly discharged without being effectively utilized, leading to energy waste and increased production costs for the enterprise.
2. The direct discharge of gas causes air pollution. In today's context of increasing environmental pressures, this will inevitably affect the development of enterprises.
3. The gas medium generally contains substances such as sulfur, which, when mixed with flue gas, can cause corrosion and damage to pipeline systems, valves, and other components.
4. During the instantaneous exhaust process, there is a possibility of high-temperature flue gas inside the furnace mixing with the gas inside the burners. If the oxygen content in the flue gas is too high, it can lead to secondary combustion with the gas in the regenerative media, causing the honeycomb structure to melt, fracture, deform, and twist, ultimately resulting in blockages.
Energy saving and environmental protection have always been the unwavering direction and pursuit of Xuanding. In response to the common problems of industrial kilns using regenerative combustion technology, especially in the increasingly severe environmental situation in China, Xuanding's technical team has proposed an integrated solution centered on gas purging through extensive theoretical research and field practice. This solution can thoroughly solve the problem of gas (common area) emissions, achieving the goals of energy saving, emission reduction, and environmental protection.
This integrated solution mainly focuses on three aspects:
Gas Purging:
By recirculating part of the flue gas discharged from the furnace back into the regenerative combustion system, the gas purging is carried out as follows:
A new fan is added to extract part of the flue gas from the exhaust system and deliver it to the reversing valve, where it purges the gas in the common area back into the furnace for combustion.
The following key points need careful consideration:
Equipment Sealing Performance
The frequent reversing technology in regenerative combustion strengthens the circulation of furnace gas within the heating furnace, evens out the temperature field, and improves heating quality. The reversing valve used in this technology needs to consider its sealing performance (especially after prolonged use) because any internal leakage during normal exhaust would result in gas being directly discharged through the exhaust system, causing energy waste and environmental pollution.
Air-Fuel Ratio Control
Improper air-fuel ratio control leads to incomplete combustion of gas in the furnace, resulting in a certain amount of gas being directly discharged in the flue gas, causing energy waste and environmental pollution. It also negatively impacts the uniformity of the furnace temperature and the heating quality of the material.
Depending on the actual situation on-site, residual oxygen analyzers can be configured for each section to detect residual content, thereby adjusting the air-fuel ratio coefficient and air-fuel ratio accordingly. An integrated oxygen/CO analyzer can also be configured to detect residual oxygen and CO content, allowing for timely adjustments to the air-fuel ratio and real-time monitoring of CO emissions, the sealing status of the reversing valve, and necessary handling.
Case Studies and Achievements
Donghai Special Steel Bar Heating Furnace Phase IV (Technical Improvement + Gas Emission Reduction Retrofit)
Original Heating Furnace:
Blast furnace gas dual regenerative heating furnace
170 tons/hour
Three-zone control, centralized reversing, four-way reversing valve
Specific Retrofit Content:
Technical improvement + gas purging
Conversion of four-way valves to three-way valves
Retrofit of the combustion system and control system
Addition of a gas purging system
First Line Heating Furnace at Dadaohai in Fujian (Gas Emission Reduction Retrofit)
Original Heating Furnace:
Blast furnace gas dual regenerative heating furnace
120 tons/hour, three-stage control
Sectional and side distribution, large three-way reversing valve
Specific Retrofit Content:
Modification of the combustion system and control system
Addition of a purging system
Hebei Zongheng Steel 1450 Production Line Heating Furnace Gas Emission Reduction Project
Original Heating Furnace:
Blast furnace gas dual regenerative heating furnace
270 tons/hour
Combination of centralized and distributed control
Upper and lower centralized control for preheating section, first heating section, and second heating section
Upper and lower distributed control for equalizing section
Specific Retrofit Content:
Modification of the combustion system and control system
Addition of a purging system
Company Profile
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With decades of rapid development and accumulation, China has been perfect and mature on technology and management in various industrial areas, shaping a complete processing manufacturing industry with competitive price, well known for its excellent skill, high efficiency and hardworking team with qualification for personnel dispatching.
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