Analysis of Main Technologies of Energy Saving and Emission Reduction in Carbon Industry Production in China

Carbon materials are divided into three major categories: conductive materials, special structural materials and special functional materials according to different functions. They are mainly used in metallurgy, chemical engineering, machinery, aerospace, nuclear industry, biology, and electronics industries. The industrial production of carbon materials mainly includes the processes of storage and transportation of raw materials, calcination, melting of bitumen, kneading of medium-breaking ingredients, molding, roasting, impregnation, secondary roasting, graphitization, machining, and packaging.
China's carbon material industry has made considerable progress, with great achievements in terms of production, variety, and quality. The level of production technology and equipment has already become an important part of the international industry. Although China has not listed carbon products as high-energy-consuming products, raw materials for carbon products such as petroleum coke, needle coke, pitch coke, metallurgical coke, anthracite coal, and coal-tar pitch are all energy products that are consumed during the production of carbon products. A large number of secondary energy products such as electricity, fuel, and water. Taking the production of high-power graphite electrodes as an example, the total energy consumption per ton of finished products is as high as about 5 tons of standard coal, and the comprehensive energy consumption per unit of foreign advanced carbon companies is on average about 20∼30% lower than that of Chinese carbon companies. In addition, carbon materials in the production process more pollutant emissions, such as asphalt melting, kneading, molding, roasting, impregnating process of asphalt smoke pollution, etc., causing harm to the environment and the health of employees. It can be seen that China's carbon industry has great potential for energy saving and emission reduction.
1 carbon industry energy-saving emission reduction requirements from the perspective of <br> carbon industry to consider the development of low-carbon economy, there are two main aspects: First, to meet the research and production of renewable energy, clean energy production and energy conservation and other industries needed Carbon products, the second is to do a good job in the carbon industry's own production process of energy-saving emission reduction, including the production process and equipment [1]. The following focuses on energy-saving and emission reduction technologies in the carbon industry production process.
1.1 Main Issues to be Solved in Energy Saving and Emission Reduction of Carbon Enterprises
1) The energy conservation, emission reduction and quality improvement of downstream industries of carbon material products are the primary concerns, involving the quality and specification of the carbon products themselves, followed by the production process of the carbon material industry itself.
2) Realization of Energy Saving and Consumption Reduction Although carbon products do not belong to industries with high energy consumption, compared with similar advanced foreign companies, the energy consumption index per unit of product output is relatively high, especially roasting and graphitization processes, and the energy consumption is high. technical problem. The starting point is to reduce material process losses, including increasing the yield, qualification rate and yield of carbon products (including finished products and semi-finished products); strengthening on-line monitoring and management control of production processes; formulating and producing various types of products according to product quality requirements and raw material performance. The process flow and process control conditions improve the inspection system for finished products, production processes and semi-finished products.
3) Resolving Pollutant Emissions During the production process, pollutants are discharged in various processes. For example, the bitumen fume pollution caused by the asphalt melting, kneading, molding, roasting, and impregnation processes in the asphalt melting process has become an issue for carbon companies. The primary problem facing cleaner production.
4) Reuse of waste by-products Due to the special nature of carbon production, various processes in the production process will produce a large number of waste by-products. If these waste by-product materials are not used, they will not only cause high energy consumption per unit of product. It will also cause great waste of raw materials and serious environmental pollution. However, how to detect waste by-products in production in a timely and on-line manner is also a major problem.
1.2 Standards of Energy-Saving and Emission Reduction Standards for Carbon Production <br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br> 1.2 Energy Consumption Limits for Production Furnaces YS/T 131-2010, Energy Consumption Limits for Prebake Anode Products for Aluminum Electrolysis, GB25325-2010, Process Design Specifications for Carbon Plants (GB50XX--2012), and Comprehensive Energy Consumption Calculation General Principles GB2589-2008, Technical Specifications for Environmental Protection Design of Non-ferrous Metal Industry YS5017-2004, Aluminum Industry Pollutants Emission Standard (GB25465-2010), Clean Production Standards - Electrolytic Aluminum Industry HJ/T187-2006, Carbon Production Safety and Hygiene Regulations" GB15600-2008, "Industrial Boundary Noise Standards for Industrial Enterprises" GB12348-2008, Implementation of Class II Standards, "Boiler Air Pollutant Emission Standards" GB13271-2001.
1.3 Concepts and Types of Energy Saving in Carbon Production
1.3.1 Carbon per unit of product energy consumption Carbon per unit of product Energy consumption including unit product comprehensive energy consumption and main process of carbon production (calcination, roasting and graphitization) unit product energy consumption; energy consumption including physical consumption and process consumption; unit product points For the preparation of raw materials, carbon products, graphite products.
The total energy consumption per unit product of carbon materials accounts for 65 to 80% of the physical energy consumption, and the process energy consumption accounts for 20 to 35%. Therefore, in the production process, we must strengthen the management of raw materials and intermediate products. We should minimize material losses in all production processes, especially strictly control the burning of petroleum coke in the calcination section. In the energy consumption of the process, fuel consumption accounts for 65 to 80%, which indicates that selecting the advanced kiln and combustion control system is crucial for the daily maintenance of the kiln.
1.3.2 Carbon production enterprises' energy-saving key carbon production enterprises should actively rely on technological progress, deploy advanced energy-saving equipment and new energy-saving technologies, and maximize the thermal efficiency of the three major furnaces (calciners, roasters, and graphitization furnaces) of carbon companies. , Reduce energy losses and reduce corporate energy costs.
1.3.3 Evolution of carbon industry process With the advancement of science and technology, the production process of carbon products is similar to that of the steel industry. It gradually becomes large-scale, continuous, automated, and highly integrated. Its energy-saving thinking has also undergone a certain evolution, mainly from monomer energy-saving development. To the system energy saving.
The system energy conservation refers to the carbon industry as a whole, and the comprehensive utilization of energy cascades at each step makes the total energy consumption of the carbon industry as small as possible. System energy saving includes: management energy saving, technology saving, and process optimization.
(1) Management and energy conservation Establish and improve the company's energy control and management center, monitor, control, adjust, analyze and diagnose failures in carbon manufacturing processes, predict energy balance, optimize system operation, expert systems, collect data at high speed, and analyze in a timely manner. Archive processing to achieve decentralized control of energy systems, centralized management, seamless integration with ERP or MES systems. Managing energy savings can save companies from 10 to 15% of their total energy consumption.
(2) Energy Saving Technology Energy conservation is achieved using the first technology equipment and processes.
(3) Process optimization means the structural adjustment of the entire carbon industry or a certain process, optimization and retrofitting, elimination of outdated equipment, and adoption of advanced processes to achieve overall energy savings.
2 Main energy-saving technologies in China's carbon production process
2.1 Major energy-saving technological achievements in carbon production equipments <br> China's carbon-based industrial production major energy-saving technologies have made great progress, is based on quality and homogeneity of process products, large-scale equipment, thermal furnace structure optimization and energy-saving material applications, etc. Among them, breakthroughs have been made in the energy-saving technology of carbon furnace equipment. These results include: calcination of large-scale petroleum coke rotary kiln, large-scale tank calciner technology, high-temperature continuous DC electric forge graphitization furnace, new open roasting technology, and large materials Box baking furnace with lid, bottom-type roaster, high pressure impregnation, tunnel kiln, new ring furnace secondary roasting furnace, LWG (series graphitization) technology, large-scale Acheson graphitization technology.
The production technology of the above kiln equipment or the energy saving technology optimized for the equipment structure is the key to reducing the overall energy consumption of the carbon industry. They are the main equipment for production and also the energy consumption head. At the same time, some technology research institutes and enterprises in China have successively carried out technological optimization or renewal of related furnace equipment, including optimization of production and operation processes, optimization of furnace structure and application of energy-saving materials, and automation of supporting facilities. Its research methods are diversified, and some of the most powerful scientific research units have adopted a combination of computer simulation and industrial testing.
2.2 Carbon Waste Heat Recovery
2.2.1 Type of waste heat:
Some industrial furnaces consume large amounts of fuel, and their thermal efficiency is very low, generally only about 30%, while the heat taken by high-temperature flue gas, high-temperature slag, high-temperature products reaches 40% to 60%. The waste heat used accounts for about one-third of the fuel consumption in metallurgy. Waste heat is a secondary energy source. It is a product of the conversion process of primary energy and flammable materials. It is the amount of heat left by the heat generated in the process of fuel combustion after a certain process is completed. Generally divided into the following categories: high-temperature flue gas waste heat, high-temperature steam waste heat, high temperature slag waste heat, high temperature product waste heat (including intermediate products), cooling medium waste heat, combustible waste heat, chemical reaction and waste char residue, condensate waste heat, etc. 2].
2.2.2 Use of charcoal waste heat:
At present, China's carbon industry waste heat utilization methods are mainly direct, indirect or comprehensive. The main waste heat utilization is to directly preheat materials, preheat air or fuel for the production process or the upper and lower related processes; use the heat medium as a heat carrier; produce steam (production and take-out); produce superheated steam and generate electricity; Heating and cooling, etc.
The temperature of flue gas generated during the calcination process of petroleum coke, electric calcined anthracite, roasting of carbon products, graphitization, etc., reaches 200-1000°C, which is of great value. At present, the calcined waste heat has been successfully used to generate steam, power generation, heat media, heating, immersed hot air circulating heating, etc., and the utilization technology of roasting and graphitizing furnace waste heat remains to be researched and developed.
3 carbon production and emission reduction technology
3.1 Main sources of pollution and methods of treatment <br> The main environmental pollutants produced by carbon production are air pollution. The main air pollutants are: asphalt fume (including PAH), particulate matter, fluoride, and sulfur dioxide. One of the asphalt gas is more difficult to deal with, there are processing technology [3]:
1) Asphalt smoke wet washing and purifying (washing): The effect is poor, and secondary pollution is difficult to handle.
2) The trapping method of the electric trap: it is effective for asphalt fumes, but it has poor effects on PAH, sulfur, and fluoride.
3) Dry material adsorption method (carbon powder, alumina, alumina): The fluoride effect is better, but the alumina “blow” containing bituminous fumes is not welcome back to the electrolytic cell.
4) Regenerative incineration method: It has good effect on asphalt fume (including PAH), but its energy consumption is large, and it needs to consider the comprehensive utilization of thermal energy.
5) Black method: The effect on bitumen fume (including PAH) is good, but the current application range has limitations.
3.2 Carbon emission reduction technical requirements
1) The concentration of bituminous fume emitted from the roaster, bituminous melting, and batching reaches the standards of 20 mg/m3, 30 mg/m3, and 20 mg/m3, respectively, as stipulated in the newly promulgated Environmental Protection Standards for Aluminum Industry Pollutants (GB25465-2010); BaP (benzene) And a芘) emission concentrations reached 0.06mg/m3, 0.09mg/m3 and 0.06mg/m3 limit, respectively;
2) The SO2 emission concentration of flue gas purification in the roaster and calciner reaches a limit of less than 400 mg/m3; the flue gas purification fluoride emission concentration of the roaster reaches a limit of less than 3 mg/m3.
3.3 Asphalt gas treatment technology for raw products <br> Asphalt gas treatment technology for raw products belongs to the dry black method adsorption. Feeding with a dosing weigher, providing stable and uniform feed; a patented reactor in the system, high adsorption efficiency; electric heating system to prevent tar condensation; high purification efficiency (>99%); tar discharge concentration ≤ 10mg/Nm3, dust emission Concentration ≤ 30mg/Nm3. The main technical features:
1) The system flow is simple and reasonable; 2) The coke powder used for adsorption is used in the production workshop and recycled; 3) The adsorption efficiency is high; 4) It is safe and reliable; 5) The independent innovation has complete intellectual property rights; 6) The control technology is advanced; ) Suitable for continuous kneading and intermittent kneading, the existing production line transformation and new construction.
3.4 Purification of Roasting Flue Gas Combined Method <br> Pre-dust removal, total evaporation spray, electric tar catching, and dry alumina adsorption dust collection technology are integrated in series to form a multi-stage treatment roaster flue gas technology that can be used flexibly. The main effects are: high purification efficiency, no secondary pollution, easy operation and management, etc. After purification, pollutant emission indicators are far lower than national standards and meet international standards.
4 New Trends in Energy Saving and Emission Reduction Technologies for Carbon Production <br> Current major energy conservation and emission reduction technologies for carbon industry in China and in the near future are mainly energy-saving technologies for furnaces and integrated emission reduction technologies for asphalt smoke, BaP and SO2, some of which have reached the stage. Sexual results, most of which are under development, mainly include the following: petroleum coke ball calcination technology; calcined flue gas and raw product asphalt smoke, roaster low-temperature flue gas comprehensive treatment technology; regenerative combustion technology (RTO, regenerative thermal oxidation); Roasting technology without purification facilities; waste charcoal batch-type combustion rack for open-loop roaster; waste heat recovery and flue gas desulfurization of graphitizing furnace; recycling and utilization of flue gas heat recovery and flue gas desulfurization technology; Further recycling and process desulfurization technology; carbon production "interface technology".
5 Conclusions (1) The main problems that need to be solved in the energy conservation and emission reduction of China's carbon industry are energy saving and consumption reduction and pollutant emission in the process and furnace equipment. The energy conservation and emission reduction in downstream industries of carbon material products and the improvement of quality and efficiency are the primary concerns. Focus.
(2) Computer simulation and optimization techniques are mainly used for the main energy-consuming furnace equipment in China's carbon industry. The furnace kiln operation parameters, process and furnace structure are optimized for analysis to improve equipment performance and reduce energy consumption.
(3) There are many ways to use waste heat, but the technology of roasting and graphitizing furnace waste heat utilization in China's carbon industry needs to be researched and developed.
(4) The bio-adsorption treatment technology of raw product asphalt flue gas dry material is distinctive and its technology is mature. It has played a significant role in the treatment of bitumen in the carbon industry in China. Regenerative combustion technology (RTO) is a promising method for the treatment of asphalt smoke.

references:
[1] Wang Shaowen, Yang Jingling et al. Metallurgical Industry Energy Saving and Emission Reduction Technology Guide [M]. Beijing: Chemical Industry Press, 2008.8
[2] Zhao Qinxin, Wang Yufeng, et al. Current status and technology development of waste heat utilization in China [J]. Industrial Boiler, 2009(5): 8~15
[3] Li Shenghua. Smoke elimination, dust control and noise control in carbon plants[J]. Carbon Technology, 2006(2): 49~55