Continuous Catalytic & Hydrothermal Oxidation for Refractory COD

Catalytic Hydrooxidation (CHD-Ox) and Pressure Hydrothermal Oxidation (PHT-Ox) is a process that involves the use of high pressure and temperature in the presence of oxygen to oxidize refractory organic compounds. Refractory organic compounds are compounds that are resistant to biodegradation and are difficult to treat using conventional methods. Spent Caustic from Refineries, Drugs molecules from API plants and agrochemicals and pesticides are suitable candiates for this technology.

Process

The process of PHT-Ox involves the use of a reactor vessel, where the refractory organic compounds are mixed with water and then pressurized. The mixture is then heated to a high temperature, typically above 200°C, in the presence of oxygen. The high temperature and pressure cause the organic compounds to oxidize, producing carbon dioxide, water, and other non-toxic byproducts.

PHT-Ox has been used to treat a wide range of refractory organic compounds, including polycyclic aromatic hydrocarbons (PAHs), chlorinated hydrocarbons, and phenols. The process has been found to be effective in removing up to 99% of these compounds from wastewater and other industrial effluents.

One of the advantages of PHT-Ox is that it does not produce any toxic byproducts, making it a safe and environmentally friendly process. Additionally, PHT-Ox can be used to treat a wide range of organic compounds and can be easily scaled up for industrial applications.

Overall, PHT-Ox is a promising technology for the treatment of refractory organic compounds in industrial wastewater, and it has the potential to become an important tool in the field of environmental engineering.

Compounds that are difficult to biodegrade and/or have a low BOD:COD ratio are categorized as refractory organic compounds.

Tertiary butyl alcohol, present in cosmetics, perfumes and dyes, aromatics, phenols, and cresols, used in pharmaceutical production, have low BOD:COD values and are thus considered poorly biodegradable. On the other hand, acetic acid and chloroform, which are common chemicals, have zero BOD5 concentrations and are therefore classified as non-biodegradable. The Spent Caustic coming from Ethlene and refinery plants is a tough one to break. The mercaptans, Phenols and Sulfidic compounds have to treated. PHT-Ox can be a chosen technology for Caustic re-cycle?

The PHT-Ox process is utilized for treating industrial wastewaters as well as in-process applications, and has been widely employed for sludge treatment and destruction purposes.?

The Method:

CHD-Ox & PHT-Ox are?oxidation?process of dissolved or suspended substances in a water-based environment, utilizing oxygen as the oxidant. The?source of oxygen can be cyclinders or?air, the process oxidises the COD at diffetent conditions. The oxidation reactions are carried out at pressures ranging from 1.- 22 bar and temperatures between?30-180°C . The reaction takes place in continuous plug flow reactors. The necessary temperature for the process is determined by the desired treatment goals and the ease or difficulty of oxidizing the substances. Operating at higher temperatures necessitates greater pressure to maintain a liquid phase in the system. The reactions areenergy positive, so the cost of treatment is very low.?

The typical PHT-Ox system is a continuous process using rotating equipment to pressurize the feed stream and air to the system operating pressure. Heat exchangers are routinely used to recover energy from the reactor effluent, which is then used to preheat the feed/air mixture entering the system. Auxiliary energy, usually steam, is necessary for startup and can provide heat if required.

The reactor vessel provides residence time at the desired operating temperature enabling propagation of the oxidation reactions. Since the oxidation reactions are exothermic, sufficient energy may be released and recovered to allow the Oxidation system to operate without any additional heat input.

Piloting:

Pilot testing are an effective way for customers to test solutions. The Innovation Center at Diva Envitec Pvt Ltd offers this service to clients on cost basis. These tests can be conducted on-site or off-site in actual operating conditions, with the aim of finding the most optimal and cost-effective solutions for each application. The cost of the test work is often recovered multiple times over through more efficient and trouble-free full-scale plants.?

Bench-scale autoclave testing is utilized to establish preliminary design standards for full-scale designs and allows for the assessment of process economics. Autoclaves can also be used to conduct materials-of-construction testing to identify suitable alloys for a particular application. Other treatment processes, such as biological treatment, can be evaluated in conjunction with PHT-Ox for effluent polishing. Continuous flow pilot studies can be carried out under a broad range of operating conditions. Pilot plant studies are conducted to optimize the design conditions for customized applications, and to produce representative treated products for further testing and evaluation. Pilot systems are built using a variety of alloys, including high nickel alloys and titanium, and the PHT-Ox system configurations are typically tailored to the specific process approach.

In conclusion, the wet air oxidation process can effectively convert refractory compounds into more biodegradable oxidized effluents. As a result, the treated aqueous solutions exhibit higher BOD:COD ratios and demonstrate greater oxygen uptake during respirometry tests compared to the untreated parent compounds. These findings suggest that the effluents resulting from?CHD-Ox and PHT-Ox are more conducive to biological treatment.?