Recovery of valuable chemicals from caprolactam and adipic acid production
Caprolactam and adipic acid production generates significant volumes of liquid waste. These wastes contain valuable chemical products. New technologies make it possible to recover these products, reducing the volume of waste incineration and air pollution.
One of the significant disadvantages of existing caprolactam and adipic acid production facilities is that significant quantities of liquid waste are generated during the production process at the stage of cyclohexane oxidation with molecular oxygen from the air.
These wastes, namely sodium adipates (alkaline wastewater, hereinafter referred to as SAPW), POD oil (X-oil or ANON-oil), the alcohol fraction (hereinafter referred to as AFPC), and a mixture of esters and carboxylic acids (hereinafter referred to as MECA), contain significant quantities of valuable chemical products. However, the overwhelming majority of the above-mentioned wastes are currently sent for thermal treatment (incineration). Hundreds of thousands of tons of liquid waste are disposed of in this way every year, while millions of cubic meters of flue gases are released into the atmosphere.
These flue gases contain nitrogen oxides, carbon monoxide, and aerosols of soda dust, which in turn contains manganese, cobalt, and chromium. They contribute to environmental degradation and are among the major factors contributing to air pollution in areas where caprolactam and adipic acid production facilities are located. They also require significant expenditures on fines for atmospheric emissions and result in substantial costs—tens of millions of US dollars—for the purchase of natural gas used to incinerate the above-mentioned wastes.
New technologies for processing waste from caprolactam and adipic acid production were developed by our engineering team in the 1990s and 2000s and successfully tested at a pilot-scale plant comprising four main process units, each with a volume of 2 m³. The technologies were tested using waste samples from caprolactam production facilities located in the former USSR, including CherkasyAzot OJSC (Ukraine), KuibyshevAzot PJSC, KemerovoAzot OJSC, ShchekinoAzot OJSC, and GrodnoAzot OJSC, as well as waste from adipic acid production facilities, including SeverodonetskyAzot OJSC and RivneAzot OJSC (Ukraine).
The application of these new technologies at caprolactam and adipic acid production facilities will make it possible to completely eliminate waste incineration, generate significant additional profit from the sale of valuable chemical products recovered from these wastes, substantially reduce the negative environmental impact, and save large volumes of natural gas.
The residual water stream with low chemical oxygen demand (COD) is sent for biological treatment.
Chemical products recovered from the wastes can be used as feedstock for the production of high-quality polyamide fibers, polyester engineering plastics, polyurethane foams, motor fuel additives, plasticizers, technical detergents, synthetic coolants (metalworking fluids, MWFs), varnishes, and solvents.
Preliminary calculations show that the sale of chemical products recovered from the wastes can provide enterprises with significant additional net profit comparable to the profit generated by their primary production.
The following is an approximate calculation of the economic efficiency expected after implementing our technology for processing liquid waste from the following production facilities:
Recycling of alkaline wastewater from caprolactam production based on the example of Kuibyshev Azot PJSC in the amount of 140,000 (tons/year)
| No. | Recovered products | Content (%) | Quantity of products in 140 ths. tons of alkaline wastewater, tons |
Price per ton (thousand USD) |
Total cost (thousand USD) |
Notes |
|---|---|---|---|---|---|---|
| 1. | Adipic Acid | 12 | 116,800 | - | - | Adipic acid is used to produce dimethyladipinate after esterification with methanol |
| 20,021 dimethyladipinate |
2 | 40,042 | ||||
| 2. | Resin | 10 | 14,000 | 1 | 14,000 | technical detergent base |
| 3. | Cobalt | 0.043 | 60 | 20 | 1,200 | on metal basis |
| 4. | Chrome | 0.057 | 80 | |||
| 5. | Sodium sulfate | 31.71 | 44,392 | 0.4 | 17,756 | on dry basis |
| 6. | Annual savings on natural gas purchases | 50,000 | ||||
| Estimated gross revenue | 122,998 | |||||
Recycling of ANON-oil generated during cyclohexane oxidation and dehydrogenation based on the example of Grodno Azot OJSC in the amount of 17,000 tons/year
| No. | Recovered products | Content (%) | Quantity of ANON-oil, tons |
Price per ton (thousand USD) |
Total cost (thousand USD) |
Notes |
|---|---|---|---|---|---|---|
| 1. | Mixture of cyclohexanol and cyclohexanone | 15 | 2,550 | 2 | 5,100 | |
| 2. | Cyclohexanone dimer (dianon) | 45 | 7,650 | 1 | 7,650 | Raw material for the production of alcohol (2-cyclohexylcyclohexanol), corrosion inhibitors, ortho-phenylphenol, fragrances, and phenyl-formaldehyde resin |
| 3. | Polymer resin | 40 | 6,800 | 1 | 6,800 | Base for anti-corrosion coatings |
| Estimated gross revenue | 19,550 | |||||
Recycling of esters and acids mixture (EAM) based on the example of BASF (Belgium) in the amount of 80,000 tons/year.
| No. | Recovered products | Content (%) | Quantity of products in 80 ths. tons of EAM, tons |
Price per ton (thousand USD) |
Total cost (thousand USD) |
Notes |
|---|---|---|---|---|---|---|
| 1. | Adipic Acid | 27 | 21,600 | Adipic acid is used to produce dimethyladipinate after esterification with methanol | ||
| 25,742 dimethyladipinate |
2 | 51,484 | ||||
| 2. | Ɛ - oxycapronic acid | 23 | 18,400 | 2.5 | 46,000 | Monomer for production of polycaprolactone |
| 3. | Polymer acid resin | 10 | 8,000 | 1 | 8,000 | Concentrate for production of technical detergents and synthetic coolants |
| 4. | Other acids | 10 | 8,000 | 1 | 8,000 | |
| 5. | Water | 30 | 24,000 | |||
| 6. | Presumed annual savings on natural gas purchases | 5,000 | ||||
| Estimated gross revenue | 118,484 | |||||
Recycling of alcohol fraction of caprolactam production based on the example of BASF (Belgium) in the amount of 3,000 tons/year
| No. | Recovered products | Content (%) | Quantity of products in 3,000 tons of alcohol fraction, tons |
Price per ton (thousand USD) |
Total cost (thousand USD) |
Notes |
|---|---|---|---|---|---|---|
| 1. | N-pentanol | 46 | 1,380 | 2.5 | 3,450 | Raw materials for the production of potassium xanthogenate as well as n-amialyl acetate |
| 2. | Hexanal, cyclohexanone | 47 | 1,410 | 1.5 | 2,115 | Raw material for the production of aldehyde and keto resins used in paints and varnishes for glossing |
| 3. | Heptanone | 1 | 30 | 1.5 | 45 | |
| 4. | Water | 6 | 180 | |||
| Estimated gross revenue | 5,610 | |||||
Currently, EuroMoving Ltd. is engaged in the development of new technologies for processing liquid waste generated during the production of caprolactam and adipic acid at the stage of cyclohexane oxidation with molecular oxygen from the air.
These new technologies make it possible to almost completely eliminate the need for thermal treatment (incineration) of waste and recover valuable chemical substances from it.
The technologies were developed by a team of our engineers in the 1990s and 2000s using waste samples from production facilities located in Ukraine and other countries of the former Soviet Union.
Until February 2022, a pilot-scale waste processing plant was located on the premises of the Krasitel production association in Rubizhne, Luhansk Region, Ukraine.
As a result of the war, the plant was destroyed, and all further work in this area has been relocated to Kyiv, Ukraine.
