© Cao Qingxin and Zhang Mangang

Exploring the Principle and Innovating Desulfurization Process

At the beginning of establishment, the company has set up a technical innovation R&D team, signed an industry-university-research cooperation agreement with Beijing University of Chemical Technology, and established a “New Rubber and Plastic Building Process Technology and Equipment Engineering Research Center”, which takes innovating the automation of reclaimed rubber desulfurization equipment and process operability as R&D goal.

According to the principle of reclaimed rubber production process, the intelligent control system is developed. The main sub-units are controlled by modular PLC, which finally makes all units seamlessly and softly connected and supported by remote control. According to the difference between rubber bond energies, C-C bond (bond energy 370kJ/mol), C-S bond (bond energy 310kJ/mol), S-S bond (key energy 270kJ/mol), use environmentally friendly rubber chemicals and mechanical shear force, selectively cut off the cross-bond of C-S and S-S, thereby restore the plasticity of vulcanized rubber to achieve the effect of rubber devulcanizing and plasticizing.

Based on the above mechanism, Jiangsu Zhonghong has researched and developed a high-efficiency devulcanizing reclaiming equipment with single screw, large length-diameter ratio and composite shear and squeeze structure. Together with the independently developed Z/H series green composite reclaiming softener and full-automatic control and management system, the invention realizes the green reclaimed rubber production process which is energy-saving, high-efficiency and pollution-free, and effectively solves the generation of waste water and waste gas.

At present, the company has obtained 24 core intellectual property rights, including 3 authorized patents for inventions, 21 utility model patents and 4 software copyrights, and passed environmental protection and safety certifications such as EU ROSH and CE. The company has also installed intelligent and ganged ten-thousand-ton level tire reclaimed rubber production demonstration line and ten-thousand-ton level particle reclaimed rubber production demonstration line, on the one hand for industry exchanges, on the other hand, becoming a R&D base for enterprise staff training and equipment upgrading.

Intelligent Equipment with Outstanding Advantages

The “waste rubber intelligent recycling of ten-thousand-ton reclaimed rubber complete production line equipment” of the company is composed of a crushing unit, a devulcanizing and plasticizing unit and a kneading and building unit. The process characteristics of this complete equipment are:

The first is the technology of dry condition method of sulfur bond cross point destruction and reclaiming. Through the reclaiming equipment with single screw, large length-diameter ratio and composite shear and squeeze structure, in the state of no water, utilize thermal oxidation, mechanical force and chemical reaction, effectively cut off the cross point of C-S bond and S-S bond in materials, while does not or less destroy C-C bond, thereby ensure the stability of the quality of reclaimed rubber.

The second is the design of totally enclosed high-efficiency devulcanizing equipment. A screw is used. By the optimization of the screw design, improve the screw conveying capacity and heat transfer efficiency to ensure stable operation of the product for a long time.

The third is the design of fully-automatic control and intelligent analysis system. Combined with the end pressure adjustable system, through automatic adjustment of feed rate, screw speed and control method, the outlet pressure of desulfurization equipment is stabilized within the set pressure range; numerical simulation technology is used to optimize the position of cooling medium passage and temperature collection point to realize the intelligent management of product.

The fourth is the R&D of high-efficiency devulcanizing production formula. Independently developed Z/H series environmentally-friendly and energy-saving composite reclaiming activator, using green vegetable oil-based swelling agent, effectively reduces the smell of sulfur-depleting products, reduces the content of VOCs, and meets the requirements of safety and environmental protection.

Safety and Environmentally Friendly with Significantly Emission Reduction

Single production line of the complete equipment can process 10,000 tons of waste tires annually, of which 25% is steel wire, 20% is 40-60 mesh rubber powder for high value utilization, and 55% is used as raw material rubber powder for producing reclaimed rubber, which can produce 6,000 tons of reclaimed rubber.
The energy consumption per ton of the equipment is about 160kWh. Compared with traditional dynamic devulcanizer, whose energy consumption per ton is more than 220kWh, only the energy consumption per ton of desulfurization link can reduce by as much as 60kWh, with nearly 30% of energy saving, and significant effect on reducing carbon emissions. According that the production of reclaimed rubber in China is 4.8 million tons in 2017, if 50% of the reclaimed rubber is produced by the environmentally-friendly intelligent waste rubber reclaiming complete equipment of Jiangsu Zhonghong, only the desulfurization process will save as much as 144 million kWh with converted standard coal volume be 17,609.76 tons (equivalent value); calculating according to the reduction of pollutants discharged using standard coal value, it will reduce CO2 emissions by 46,137.395 tons, reduce SO2 emissions by 122.4 tons, and reduce nitrogen oxides by 106.557 tons.

The “waste rubber intelligent recycling of ten-thousand-ton reclaimed rubber complete production line equipment” can continuously run without adhesive and be free of cleaning, and the complete running is controlled by computer, achieving “environmentally friendly, energy-saving, stable, high-efficiency, safe and manpower-saving” production methods for waste rubber desulfurizing, reclaiming and plasticizing process.

Compared with operating traditional dynamic desulfurizer, the quality of reclaimed rubber and the production environment are greatly improved, reflecting in the following aspects:

The first is energy saving and environmental protection. Unit energy consumption per ton of reclaimed rubber is ≤160kWh, which is 30% less than traditional process. There is no waste water in the production process. After the environmental monitoring department tests, the emission air quality meets the environmental protection requirements and avoids secondary pollution.

The second is high quality of the products. The Z/H series environmentally-friendly and energy-saving composite reclaiming activator has been adopted, with the characteristics of high conversion rate, stable quality and less Mooney rebound. Reclaimed rubber produced from whole tire powder without coal tar, tested by Tianjin Rubber Industry Research Institute, under the premise of the same materials and the same formula, parked for one month, has a Mooney rebounded within 8 points, and other performance indicators are all better than dynamic desulfurization method which is now most commonly used.

The third is stable and high-efficiency. A screw is used. By the optimization of the screw design, improve the screw conveying capacity and heat transfer efficiency to ensure stable operation of the product for a long time.

The fourth is high security. Traditional technical equipment desulfurizes in a high-temperature and high-pressure desulfurizer, and the working pressure is 2.0 MPa to 4.0 MPa when desulfurizing. The dynamic desulfurizer is a type II pressure vessel. If it is used for a long time or improperly used, it may cause safety hazards such as deformation of tank wall, and even cause equipment and personal accidents. Jiangsu Zhonghong uses a single-screw unit to heat and desulfurize under sealed conveying conditions and completes desulfurizing and cooling with spiral cooling of the jacket to achieve normal pressure desulfurization, avoiding the risk caused by high-pressure desulfurizing and avoiding safety hazards.

The fifth is intelligence. Combined with the end pressure adjustable system, through automatic adjustment of feed rate, screw speed and control method, the outlet pressure of desulfurization equipment is stabilized within the set pressure range; numerical simulation technology is used to optimize the position of barrel cooling medium passage and temperature collection point to realize the intelligent management of product. As long as the formula data and operating parameters are set, all production processes can run automatically; production can be started with just one button, reducing labor costs by two-thirds.

The sixth is convenient for maintenance and management. The equipment is modularly assembled with small floor space, and “big data management” remote control platform is established, which can track and analyze the whole process of user data to ensure stable product quality. The clean-free design solves the dirty, disorderly and bad phenomenon at the production site, making maintenance easier and repair more worry-free. At the same time, combined with the R&D progress of the company, the system will be upgraded online and full-life-circle managed in real time to provide users with accurate services.

The “waste rubber intelligent recycling equipment” process and screw mixing technology, which are researched, developed and launched by Jiangsu Zhonghong, has hatched reclaimed rubber manufacturing enterprises such as Anhui Zhonghong Rubber & Plastic Co., Ltd. and Fujian Zhonghong New Material Technology Co., Ltd. in as short as three years; at the same time they are sold to the EU and other countries, won the praise of domestic and foreign customers, and was successfully introduced to Qatar in 2017. In addition, Jiangsu Zhonghong has also developed and applied in succession a variety of reclaimed rubber, including tire, IIR, EPDM and latex, as well as sheet-like and granular reclaimed rubber.