As the biggest coke producer, Chinese coke output is roughly 36% of those round the world and Chinese coke Exports takes fifty percent proportion of the global market. In the general situation of Chinese coke production, 1 to 1.5 t coking wastewater are produced when 1 t coke is refined. Coking wastewater contains large amount of polycyclic aromatic hydrocarbons, heterocyclic compound, phenol, phenol derivatives and chlorinated solvents, which pose a severe threat on environment. In addition, these compounds are hardly degraded biologically and cause a huge challenge on coking wastewater treatment. Due to characteristics mentioned above, Chinese government had long paid much attention on coking wastewater' s detoxication and emerged a series of regulations and goals to minimize impact of industrial coking wastewater in 11th Five-Year Plan. Regulations require that as of 2010, all coking wastewater must be treated before recharged into natural water body or reuse and COD must be less than 100mg/l. However, restricted by existing treatment technologies, majority of coking manufacturers can not achieve this goal so far.
Recently, numbers of institutions and companies focus on researches of new coking wastewater treatment technology, such as catalytic wet air oxidation and supercritical water oxidation which can achieve 99% COD removal rate. However, some rigid operating conditions restrict widely industrial applications of these technologies. For example, supercritical water oxidation requires more than 22.1MPa of operating pressure and more than 374.3oC of oxidative temperature; Catalytic wet air oxidation performs effectively at 250oC and 7MPa. These rigid operating condition not only hardly achieve in mass production but also require extremely high running cost.
Dedicated in innovation of coking wastewater treatment for more 5 years, Tuofeng developed a strong electromagnetic-field oxidation system, which can degraded coking wastewater much effectively. The principles of a strong electromagnetic-field oxidation system are following:
Electromagnetic field can stimulate vibration of both polar molecule and Non-polar molecules. Majority of organic molecules contain the significant number of Carbon-hydrogen bonds and carbon-carbon bonds. Because these bonds vibrated in inconsistent pattern when a constant electromagnetic field presents, inconsistent amplitude and frequency will cause molecular structure distortion. The distortion can decrease the degradative and oxidative chemical energy, increase oxidation rate for tens of times and allow less degradable compounds to be oxidized under normal condition.
Oxidant's oxidation potential is a function of operating temperature. Generally. Increase of temperature can increase oxidation potential which can increase the oxidation rate subsequently. Therefore, dramatic increase of oxidation rate allow oxidation of less degradable organic compound taking place under normal condition.
The solid reactive media is added during oxidative reaction. The media has a strong ability of absorbing electromagnetic and produces number of hot spots by transformation electromagnetic energy into heat. Some hot spots can achieve 1000oC and produce tens of Million Pa of pressure partially in liquid phase, which simulate a environment that supercritical water oxidation can take place. Another function of the solid reactive media is to absorb both contaminants and oxidants onto its surface. The hot spot increases oxidation potential by heating oxidant up and enhances oxidation of contaminant significantly.
The solid reactive media contains small amount of transition metals, which concentrate around hot spots. Addition of transition metals not only can increase number of hot spots but also serve as a catalyst which decrease required oxidative chemical energy.
Tuofeng applied electromagnetic-field oxidation on a treatability test of biological treated coking wastewater recharged from Steel-making Plant. The COD in final output water after electromagnetic-field oxidation is less than 50mg/L, chroma is less than 3. Final treated water is not different from normal deion water by eyes.The analytical result is following:
In order to test the effect of electromagnetic-field oxidation system, Tuofeng entrust an institution to conduct the GC-MS analyse for final output coking water. The analytical result is following:
We can draw following conclusions from the GC-MS analyse:
103 organic compounds were found in raw coking wastewater. 8 out of 103 exceeded the regulation in biological treated wastewater. Most of them are phenol, phenol derivatives.
Only 9 organic compounds were found in final output wastewater which was treated by electromagnetic-field oxidation. Contaminant concentration decreased dramatically after electromagnetic-field oxidation treatment. The GC-MS analytical result indicated that this treatment can degrade less chemical and biological degradable compounds effectively. In addition, no by-products occurred.
Eectromagnetic-field oxidation. System does not require high operating temperature and pressure. These characteristics opened up more opportunities of its application on industrial mass production. Tuofeng had conducted a 1-5m3/h semi-industrialized treatability test and the result achieve the ideal goals.
Based on Chinese condition, majority of Coking factories had establish coking wastewater treatment plants. Coking factories only need to invest a small-scale update in their existing treatment unit, the output water can meet the regulation. |
