Mr. Wang Shuhua, the president of Kemai Chemical Co., Ltd.
In recent years, as new Environmental Protection Law and “ten-measure action plan to tackle water pollution” are implemented, and the nation constantly enhances its supervision on environmental protection, rubber chemicals enterprises face huge environmental protection pressure. “After several decades of development, the category, scale and industry concentration of Chinese rubber chemicals products are largely improved, however, the environmental protection problems during production, especially the waste water treatment problem, has not been solved thoroughly yet, and becomes the bottleneck restraining the industry development and many chemicals enterprises face the awkward situation of shutdown and rectification.” On the Rubber Industry Cutting-edge Technology Forum held in Tongling recently, Wang Shuhua, president of Kemai Chemical Co., Ltd., expressed when being interviewed by the journalist. Kemai always took waste water treatment as the R&D focus and successfully developed rubber chemicals waste water recycling technology in 2015 to thoroughly solve the waste water pollution problem of rubber chemicals and realize resource application of waste water and green production of rubber chemicals.
Waste water is hard to be treated - Existing technology can not solve
The journalist learned that the waste water generated by production of rubber chemicals generally had the characteristics of high COD, high salt content and difficult degradation and belonged to the category which was difficult to be treated in waste water treatment industry. Its features were: high salt content, which meant that the salt concentration was more than 3% on average, and the salt concentration of the waste water of some products could even reach over 10%; high COD, which meant that the raw materials, intermediate products and finished products during production had certain solubility in water and the COD was mostly about 20,000mg/L; and difficult degradation, which meant that the waste water generally contained organic amine such as aniline, tert-butylamine, and cyclohexylamine and its derivatives as well as thiazole organics and ammonia nitrogen such as benzothiazole and MBT, which had strong toxicity to microorganisms and poor biodegradability.
Wang Shuhua told the journalist that due to the above reasons, waste water treatment of rubber chemicals process had been the hot spot in the industry, domestic chemicals enterprises carried out extensive attempts for waste water treatment, and the common treatment methods were mainly physical method, chemical method, physical-chemical method and biochemical method. The known reported methods included various combined processes such as “multiple-effect evaporation+biochemistry”, “evaporation+oxidation”, “deep oxidation+flocculation+resin absorption” and “electrolysis+absorption”. Kemai also tried multiple technologies and combinations for waste water treatment over the years, including multiple-effect evaporation, Fenton oxidation, catalytic oxidation, microelectrolysis, biochemistry, resin absorption, etc., but still had four large problems.
Firstly, waste salt processing problem. A part of processes do not remove the salt from the waste water and can not realize recycling; a part of processes adopt multiple-effect evaporation desalting technology, but can not completely separate the organics and salt; with a large area, high energy consumption and large operation cost. Secondly, organics processing problem. Adoption of oxidation technology generally will destroy the structure of the organics and cause change of the structure of the organics, thus the organics can not be recycled, easily forming solid waste, and the pollution source still exists. Thirdly, large waste water discharge. Generally, the industry will generate over 10 tons of waste water by producing 10,000 ton of rubber chemicals, which has a high operation cost and bad operation stability after being deeply treated. Fourthly, the processing unit covers a large area and has high operation and maintenance cost, which largely squeezes and even totally occupies the living space of the enterprise.
Find a new path - Developing waste water recycling process
Wang Shuhua said that aiming at the above process, operation and cost problems, Kemai found a new path and changed thinking to propose the concept of waste water recycling in 2012, that is, separating the process waste water with high COD, high salt content and difficult to be degraded into recyclable reclaimed water, industrial salt and organics. The target is: developing a solution which can realize reasonable separation of water, salt and organics; the equipment covers a small area and the waste water reaches the standard to be charged (COD < 40ppm); and the reclaimed water, salt and organics synchronously realize recycling.
Through investigation, Kemai locked MVR evaporation technology with dual advantage of energy conservation and low temperature. The main features of this technology are: the system has modular structure and the structure is compact and simple; with electric energy as the main power source, the operation cost is low; the system operates with low pressure and temperature, which can reduce scaling and heat waste, has high heat efficiency, and does not destroy the structure of the organics; and it can be operated simply and adjusted conveniently.
Wang Shuhua introduced that such equipment had been widely applied to industries such as chemicals, pharmaceuticals, food and water processing, the technology was mature but it was the first time to be applied to waste water treatment of rubber chemicals. Therefore, organically combining this equipment with supporting processing process of waste water of rubber chemicals is the technical key of this project to realize the above target.
Through years of research and development, Kemai successfully developed the rubber chemicals waste water recycling process relying on the energy efficiency advantage and low temperature feature of MVR evaporation equipment together with key technologies for raw water pre-treatment and condensate water deep treatment.
Wang Shuhua expressed that this solution not only solved the problem of up-to-standard discharge of waste water, but also realized recycling utilization of salt, organics and water and solved many difficult problems of traditional process blocking industrialization of waste water treatment such as large floor area, large odor, difficulty of waste water in reaching standard, difficult separation of salt and organics and large volume of waste water and hazardous solid waste.
In June 2017, the “Research and Development of Rubber Chemicals Waste Water Recycling Technology” project of Kemai passed the achievement appraisal organized by CPCIF. The experts thought that the overall technology of this achievement reached international leading level and that the main innovative points of this project included: Firstly, it developed the new generation of rubber chemicals waste water recycling technology to realize reasonable separation and resource recycling of salt, water and organics in chemicals waste water, with 100% salt, 98% organics and 95% water recycled to solve the problem of disposing high-concentration organic waste water with high salt content and difficult degradation in rubber chemicals industry. Secondly, as for different products such as rubber accelerator and anti-aging agent, MVR was adopted to develop fourstep pre-treatment process of “distillation recovery + cooling sedimentation + acid-alkali regulation + airflow flocculation” to recycle the organics, thus realizing recycling of organics; and recycle the industrial salt through concentration and crystallization. Thirdly, it developed the process combining two-stage evaporation + condensation deep treatment to ensure that the effluent is recycled for production process and a small part of waste water reaches the standard to be charged, thus realizing recycling of waste water.
The effect is obvious - Promoting green development of rubber chemicals
Wang Shuhua introduced that the effect of this project was mainly embodied in three aspects, recycling of reclaimed water, MVR salt leaching and recycling of organics.
Take Tianjin factory as the example, after treatment of waste water of rubber chemicals, it realized that 95% water returned to the production process and a part of reclaimed water which can not be consumed could reach the standard to be discharged with COD reduced to 40mg/L after being deeply treated, thus realizing saving 80,000 tons of fresh water each year. The MVR leached salt reached the standard of industrial salt, conformed to the use requirements of the downstream users and could be used as snow-melting agent, cement additive, salt for leather curing, etc.
It is learned that Kemai successively built six equipment in two factories in Tianjin and Inner Mongolia in 2016 to satisfy the existing use demand; and added 2 backup equipment in 2017 to satisfy the demand for stable operation. Meanwhile, Kemai has applied for 3 relevant invention patents.
