Qinggang's practice of developing circular economy

Abstract:Qinggang makes establishing energy-saving and environmental-friendly enterprise as the aim, management innovation and technology innovation as the carrier, transforms the means of economic growth actively and forms a developing mode of circular economy. Internally it achieves the closed circulation of the Gas, water and waste heat and comprehensive reutilization of the solid waste and externally, Qinggang successfully disposed the hazardous waste of chrome slag from the chemical industry. Then a local circulative industrial chain is established preliminarily and achieving the harmonious development of economy, environment and the Society.

I. Introduction

Iron and steel industry is a resource, large energy consumption, energy consumption accounts for about 14% of energy consumption, but also a large pollutant emissions. Therefore, it is imperative for steel companies to explore the establishment of a circular economy model and create resource-saving and environment-friendly enterprises.

Qingdao Iron and Steel Holding Group Co., Ltd. (referred to as Qinggang) is an old enterprise with a history of more than 40 years. Under the traditional economic model, it has been in the vicious circle of “equal equipment backwards – high material consumption – high cost – high pollution – low efficiency”. Among them, many precious resources and secondary energy sources have not been effectively recycled, which has caused waste of resources and energy, and polluted the environment, which has affected the development and image of the company. Since the "Ninth Five-Year Plan", Qinggang has profoundly realized that there is no environmental protection advantage without the advantage of energy conservation, and there is no sustainable development of the enterprise without environmental sustainable development. Therefore Qinggang based on reality, technological innovation, technological transformation project as a carrier, and actively improve the technology infrastructure, eliminate backward production technology, vigorously carry out secondary energy, recycling resources, and actively explore the cycle of economic model, the initial realization of coal gas, water , waste heat energy, closed loop recycling and comprehensive utilization of solid waste, to achieve the recycling of single-process waste in the entire company's production process; bold innovation in the region, explore the resource treatment of chemical hazardous waste - chromium slag new technology, initially established The regional large-circulation industrial chain has achieved a win-win situation in economic, social and environmental benefits.

Second, relying on technological transformation to achieve comprehensive utilization of resources and energy

Enterprises are the mainstay of the development of circular economy, to minimize the use of resources, waste resources, reduction, and harmless. In recent years, Qinggang started with large-scale technological transformation by reducing energy and resource consumption, and initially realized closed loop and comprehensive utilization of gas, water, waste heat and solid waste, and established a circular economy model within the company. Significant results.

(1) Recycling of blast furnace gas and converter gas

1. Recovery of blast furnace gas Since the 1# and 2# blast furnaces of Qinggang have been put into production successively, the blast furnace gas has been used in addition to the hot blast stove, and the remaining gas has been discharged at high altitude, which has caused great waste of energy and polluted the atmospheric environment. Since 1998, Qinggang has invested more than 8,000 yuan, and has completed 6 coal-fired boilers and 4 fuel-fired furnaces to be converted into gas-fired projects (one of which was changed to oil-gas mixed combustion); the domestic advanced full-burning blast furnace gas is used. Double preheating waste heat fully automatic recovery regenerative heating furnace, realize 100% utilization of blast furnace gas, and use the waste heat of waste gas to heat the gas to 700 °C and then enter the furnace to burn, so that the thermal efficiency is greatly improved. At present, there are 6 blast furnaces in Qinggang, the amount of blast furnace gas is 665,000 m ³ /h, and the utilization rate of blast furnace gas has increased from 45% in 1997 to over 92% in 2005, and the annual replacement of heavy oil is 131,300 tons. Reduced by 30 yuan, the annual comprehensive benefit of 390 million yuan. In July 2005, the investment of 50 million yuan of lime rotary kiln was put into operation, and the daily production of lime was designed to be 600t. The lime kiln burned converter gas or blast furnace gas to replace coke , and 170mg of coke per ton of lime was saved. The second lime rotary kiln was put into operation in July 2006. Qinggang ended the history of coke for lime production and saved more than 70,000 tons of coke per year.

2. Converter gas recovery and utilization In March 2005, the 80t converter gas recovery project of Qinggang No. 2 Steelmaking Plant was put into use. The recovered gas of ton steel exceeded 80m ³ , and the recovered gas was used for lime slewing except for the second steel mill. The kiln saves 22,000 tons of standard coal and can generate 30.2 million yuan of benefits. The 4th 30t converter gas recovery project of Qinggang No. 1 Steelmaking Plant was put into use in July 2006. The recovery of gas per ton of steel exceeded 90m ³ , saving 41,000 tons of standard coal per year, and the profit was nearly 56 million yuan. In addition, the recycling of blast furnace and converter gas replaces coke and heavy oil, which can reduce SO2 emissions by 2958t and reduce smoke (powder) dust emissions by 892t.

(2) Industrial water to achieve closed loop

In terms of water saving, the eight key water treatment processes of Qinggang are all supporting the production of sewage treatment facilities. On the basis of the closed loop of steel rolling water, the converter dust removal water treatment system was reformed in 2000, and the net cooling ring for two equipments was restored. The water cooling tower and two dust-removing turbid water cooling towers have added a sulphur gun net water cooling tower to achieve a full closed loop of the lance cooling water, so that the dust removal water has basically reached a full closed loop; The machine cooling water realizes a full closed circuit cycle, which reduces the consumption of new water and improves the reuse rate of water. In 2005, the recycling rate of Qinggang water reached 97%, and the consumption of new water per ton of steel was 3.3m ³ .

(3) Comprehensive utilization of solid waste

In 2005, three steels, steels and steels realized three 3 million tons, and various solid wastes of 1.8 million tons were produced throughout the year (including 1.05 million tons of blast furnace slag, 480,000 tons of converter steel slag, 70,000 tons of dust-removing sludge, and iron oxide scale 5). 10,000 t, dust ash 150,000 t). The blast furnace slag is all exported; the dust-removing sludge, iron oxide scale and dust-removing ash are all used for sintering; in the comprehensive utilization of steel slag, the principle of “steel slag discharge is gradually reduced, resourced and harmless” is followed. For comprehensive treatment, the slag steel recovered by magnetic separation is used for raw materials for steel making, iron making and sintering, and the remaining steel slag is used for municipal construction and cement plant as raw materials, so that the comprehensive utilization rate of steel slag exceeds 100%. In the same month, the slag production will be processed and the amount of stacking in previous years will be gradually reduced. The recycling of solid waste generated economic benefits of 11.25 million yuan and saved raw materials of 21.12 million yuan.

(4) Recycling of waste heat and residual energy

In the production process, iron and steel enterprises will generate a large amount of waste heat and residual energy. Qinggang has done a lot of work in waste heat and waste energy recycling, and has achieved remarkable economic benefits.

1. The coking waste heat power coking plant uses two high-temperature flue gas to drive two 12000kW steam turbines to generate electricity, with a daily power generation of 380,000 kW.h and an annual benefit of 90 million yuan.

2. Waste heat recovery of converter flue gas The high-temperature flue gas of about 1500 °C is produced in the smelting process. The high-temperature sensible heat of this part of the flue gas is recovered in the form of steam for production and life. The recovery of steam per ton of steel is 100kg, the annual recovery of steam is 350,000 tons, the standard coal is 45,000 tons, and the benefit is 61.8 million yuan.

3. The continuous casting billet produced by the steelmaking plant has a temperature of about 900 °C. Since 1999, it has implemented a new hot-steaming process for billet in the continuous casting-rolling steel production line, making full use of continuous casting. The physical heat of the billet achieves the purpose of saving energy and reducing consumption. At present, the hot charging rate reaches 72%, the temperature of the slab into the heating furnace reaches 500-600 °C, the heat recovered by the ton steel reaches 6kg standard coal, and the annual utilization of waste heat converts the standard coal by 19,000 tons and the benefit is 26 million yuan.

4. Waste heat recovery of rolling steel heating furnace flue gas There are 6 steel rolling furnaces in Qinggang. The temperature of the flue gas discharged from the heating furnace is about 1000-1100 °C. In order to make better use of the physical heat of the high-temperature flue gas, the air and gas entering the heating furnace are preheated by the high-temperature flue gas, and the air and gas are preheated to 900 to 1050 ° C, and the flue gas exhausting temperature is lowered to 150 ～. Below 200 ° C, far below the temperature required by the 710 ° C energy saving standard. In addition, the heating furnace recovers steam by using residual heat of cooling water for heating in winter. Qinggang recovered 26,000 tons of steam per year, converted 0.34 million tons of standard coal, and benefited 4.68 million tons.

5. The waste heat recovery and sintering process of the sintered ore recovers the sensible heat generated during the cooling process of the sintered ore, and is used for preheating the air for sintering. Therefore, each ton of sinter can save 4kg of coke powder, save 18,000 tons of anthracite, and benefit 12 million yuan.

6. Blast Furnace Top Pressure Residual Power Generation (TRT) Qinggang has a 6300kW generator set in 5 ^# and 6 ^# blast furnaces with an annual generating capacity of 50 million kW.h and a benefit of 30 million yuan.

Third, the resource treatment of chromium residue

The chromium slag (hazardous waste) produced by Qingdao Red Star Chemical Plant has been produced for about 200,000 tons in the past decades. It has been stored for more than 50 years because of no safe and effective detoxification treatment method, which has become a problem that plagues the Qingdao municipal government. To this end, after two years of research and demonstration, Qingdao Environmental Protection Department and Qinggang have determined the comprehensive utilization plan for using chromium slag for ironmaking and sintering, and found an effective way to completely solve the problem of chromium slag pollution. Qinggang implements the recycling of chromium slag resources, and the energy saving and consumption reduction effect is obvious. Due to the equal replacement of dolomite, the comprehensive economic benefit can reach 37.83 million yuan. The successful implementation of the resource disposal of chromium slag has enabled Qinggang to initially exit a waste area cycle. the road. At present, Qinggang is exploring the recovery of carbon dioxide from the lime kiln exhaust gas for Qingdao Alkali Industry Co., Ltd. as a raw material for production.

Fourth, the environmental indicators have been improved

In 2003, Qinggang carried out ISO14001 environmental management system certification. In 2004, it fully implemented clean production and passed government acceptance. In March 2006, it won the honorary title of “Qingdao Clean Production Enterprise”. Carrying out ISO14001 environmental management system certification and promoting cleaner production are the most effective means of developing a circular economy and taking a sustainable development path. By establishing and operating a complete set of environmental management systems, the entire process of “raw materials – products – recycled raw materials – recycled products” can be effectively controlled to enable continuous improvement and sustainable development. In recent years, due to the successful establishment of the internal and regional recycling industry chain, Qinggang aims to create resource-conserving and environment-friendly enterprises, and implements a comprehensive circular economy with management innovation and technological innovation as the carrier, so that enterprises can produce Continued growth, while the benefits have increased year after year, the environmental indicators have been fundamentally improved. The changes in various indicators in recent years are shown in Table 1.

Table 1 Changes in various environmental indicators from 2001 to 2005

V. Conclusion

At present, Qinggang has been included in the Qingdao circular economy pilot enterprise. In the future development process, Qinggang will continue to adhere to the scientific development concept, and take the road of sustainable development of energy saving, pollution reduction and efficiency utilization and comprehensive utilization of resources, and promote cleanliness. The application of production technology will fully promote the recycling of waste energy and waste heat, and realize waste resource utilization and harmlessness, so as to build Qinggang into a resource-saving and environment-friendly enterprise as soon as possible.

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