Hu Qianlin, deputy secretary-general of the China Petrochemical Federation and secretary-general of the Coal Chemical Industry Committee, said that the current solid waste and waste gas treatment and emission from coal chemical industry can be basically controlled, and wastewater treatment is difficult, especially high-concentration refractory organic wastewater. . For example, the fixed-bed gasification and low-rank coal thermal cracking processes have complex wastewater components and contain hard-degradable tars, phenols, polyhydric phenols, etc., and are difficult to handle using general biochemical processes. In addition, the treatment of salty wastewater is also difficult, and it is difficult to achieve near-zero emissions in areas lacking pollution conditions. In recent years, many coal chemical companies have been actively working on sewage treatment, but their actual results have been unsatisfactory. Practical techniques and techniques are still in the exploration stage and the cost is high.
Coal is the fossil fuel with the highest carbon content. In 2015, the CO2 emissions from the coal chemical industry was approximately 470 million tons, putting pressure on China's carbon emission reduction. The national unified carbon emission trading market is scheduled to be trial run in 2016, and carbon tax will also be accelerated. This will inevitably increase the investment cost of coal chemical projects and affect its overall competitiveness. Once the carbon tax exceeds 100 yuan/ton, coal chemical projects will be difficult to bear.
Hu Qianlin stressed that in order to solve these problems, we must implement the strictest environmental protection standards and earnestly implement an environmental impact assessment system to ensure that the environmental protection facilities and the main project are simultaneously designed, constructed, and put into operation at the same time. In particular, on the discharge of waste water, the management requirements for the restricted red line in the water function area must be strictly implemented. The coal chemical project must meet the following conditions: All the process wastewater is recycled, the circulating water system wastewater is not discharged outside the plant area, and there are perfect groundwater seepage prevention measures.
Zhou Zhuye, vice president of the China Petrochemical Federation, put forward three suggestions on how to promote the green, low-carbon and recycling development of the modern coal chemical industry: First, strictly implement the “three simultaneouss†during the construction and operation of the coal chemical project. Strictly implement the "Air Pollution Prevention Action Plan" and strengthen clean production and pollution control. Comprehensive utilization of general industrial solid wastes such as gasified ash, boiler ash, etc., and the use of unusable waste residues such as high salt water enriched salts to the slag yard for storage or landfill, hazardous wastes such as spent catalyst should be supported by Special facilities for recycling.
The second is to actively research and develop the "three wastes" treatment and energy-saving water-saving technology research, carry out efficient and reasonable zero-emission or near-zero emission technology, improve the industry's energy-saving, water-saving and environmental protection level. Such as air-cooled water-saving, low-level thermal energy utilization, efficient energy-saving, high efficiency dust removal, sulfur recovery, denitrification, phenol recovery, waste water pulping, activated carbon adsorption and other technologies.
The third is to strengthen CO2 capture, application and storage technology development, carry out CO2 flooding, microalgae absorption, geological storage and other test work, and encourage qualified areas and coal chemical companies to develop CO2 recovery and utilization technologies, such as carbon sinks, flooding , purge gas, CO2 chemicals and other technologies.
At the meeting, many representatives of coal chemical companies and related experts put forward proposals and opinions on how to establish a new environmental image of modern coal chemical industry.
Tungsten carbide roller has characteristics of good wear resistance, high temperature red hardness, thermal fatigue resistance and thermal conductivity and high strength , have been widely used in high-speed wire rod, bar, rebar, seamless steel tubes, etc. Domestic production of tungsten carbide roller materials mostly WC- Co, WC- Co- Ni- Cr two series, and the content of Co, Co- Ni - Cr is in the range of 6wt% ~ 30wt%. From the use of perspective, tungsten carbide rollers has good mechanical properties, its flexural strength up to 2200 MPa or more, shock toughness up (4 ~ 6) × 10^6 J/ m^2, Rockwell hardness (HRA) is up to 78 to 90, widely in the high-speed wire rod rolling process, which is much higher than single-slot chilled cast steel or high speed steel rolls.Tungsten carbide is made of Tungsten Carbide Powder and binder phase (such as drilling, nickel, etc.), and then pressing and sintering, regardless of the conditions under cold rolled or hot rolled has excellent wear resistance, tungsten carbide rollers has been widely used in pre-finishing mill and finishing of high-speed wire rod currently. On the performance of tungsten carbide roller in hot-rolling wire rod , the material must meet the following requirements:
1. Sufficient anti-fracture strength;
2. Good abrasion resistance;
3. The smooth surface finish;
4. Excellent corrosion resistance, thermal fatigue, thermal cracking performance.
Tungsten carbide roller rings can working in bad conditions , small profile rolling (especially rebar rolling) process conditions is harsher than the high-speed wire rod, and therefore corresponds to the profile rolling ,tungsten carbide rollers recommend using high binder phase carbide.
Tungsten carbide roller material design
Pre-finishing all vehicles roller should ensure its high toughness, strength, rigidity and thermal conductivity, followed before considering its wear resistance. When designing each vehicles roller, pre-finishing materials should choose carbide grades of Co, Co- Ni- Cr binder content is high (greater than or equal to 25wt%) , requiring an average WC grain size of coarse (5μm ~ 6μm), to obtain a higher shock toughness, proper strength and hardness. For the finishing of the roller movements, particularly the last two rollers of the finish rolling, which suffered load is small, and high relative velocity of the material to be pressed (80 m / min ~ 120 m / min). In this case, the wear resistance of the roller to be the most important requirements, and must ensure the strength , timpact toughness and hardness of a reasonable match, so the binder of Co / Ni content ratio and the average grain WC control of particle size and other factors must have greater control in front of different pre-finishing rolling roll.
Tungsten carbide roller category
According to the structure of tungsten carbide rollers, it can be divided into solid tungsten carbide roller and composite tungsten carbide roller. Solid tungsten carbide rollers have been widely used in pre-finishing and finishing stands high speed wire rod mill (including fixed reducing the rack, pinch roller rack). Composite tungsten carbide roller is made of cemented carbide and other materials, and it can be divided into tungsten carbide composite roll rings and solid tungsten carbide Composite Roller. Tungsten carbide composite roll rings mounted on the roller shaft; solid tungsten carbide composite roller will be directly cast in the roll axis to form a whole, a large load is applied to the rolling mill.
Tungsten carbide roller production process control
Tungsten carbide rollers produced by powder metallurgy method, the key to its process control is the chemical composition of the material and the mixture was prepared, pressed molding, sintering and deep processing and other preparation process parameters.
1. Preparation of starting material (WC focus quality): As the WC raw material and quality control of the use of different levels of quality may fluctuate, resulting in adverse effects on microstructure.
2. Preparation of the mixture: Mixture preparation is the key to the production process of the roller, the roller of failure modes - trachoma, mainly generated by this procedure.
3. Pressing: roller pressing is an important process of the roller mill.
4. Sintering: roller sintering is to determine the final quality of the roller production processes, use of advanced low-pressure sintering technology, HIP sintering technology can greatly improve the performance of roller.
5. Deep processing: deep processing rollers have a greater impact on the quality and accuracy of the roller surface.
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