Purified terephthalic acid (PTA) is an important organic raw material, which is mainly used in the production of polyester fibers (polyester), polyester films, and polyester bottles, and is widely used in the national economy such as chemical fibers, light industry, electronics, and construction. All aspects of it are closely related to people’s living standards.
The water quality of the wastewater discharged from the PTA production plant is complex, and the main components include terephthalic acid (TA), purified terephthalic acid (PTA), crude terephthalic acid (CTA), benzoic acid (BA), p-xylene, m- Phthalic acid, p-toluic acid, 4-formaldehyde benzoic acid (4-CBA), methyl acetate, acetic acid and trace heavy metals cobalt, manganese, and other substances
Organic pollutants exist as soluble and colloidal substances. Except for chain compounds such as acetic acid and methyl acetate, which have good biochemical properties, benzene ring compounds such as TA and p-toluic acid have poor biochemical properties. Among them, toluic acid has poor biochemical properties. The proportion of COD in PTA wastewater is about 15%, while toluic acid is almost non-biodegradable.
After conventional anaerobic + aerobic biochemical treatment, the effluent of PTA has high salt content and a certain amount of COD, and the concentration of heavy metal (cobalt, manganese) ions is almost unchanged during the entire treatment process. Removal of salt to achieve reuse target.
At present, the double-membrane method is mainly used in the PTA industry for desalination and reuse of reclaimed water. The double-membrane method realizes the reuse of part of the water, which greatly reduces the unit water consumption in the production process of PTA. It is technically difficult to further process the residual RO concentrated water to meet the standard, and the investment and operation costs are relatively high.
And according to the research and analysis data of the residual RO concentrated water after the wastewater reuse in the PTA industry, the COD is about 100mg/1, the sodium ion content is 3000-5000mg/L, and the TDS can reach 12000-15000mg/l. Such water quality enters the sewage treatment plant in the park, which will have a great impact on the subsequent process.
How to provide a hardening removal system that can remove calcium and magnesium ions in RO concentrated water and reduce the burden of subsequent processes is an urgent problem to be solved.
The main purpose of the utility model is to provide a hardening system for residual RO concentrated water after reuse of PTA sewage, thereby overcoming the deficiencies of the prior art.
- The hardening system also includes a self-cleaning filter communicated with the ultrafiltration device, and the RO concentrated water enters the ultrafiltration device after being processed by the self-cleaning filter.
- The hardening system also includes a security filter, which is connected between the ultrafiltration device and the reverse osmosis device.
- The MCR device further comprises a water production tank for storing the water produced by the MCR device, and the produced water tank is communicated with the sedimentation mechanism.
- The hardening system further comprises an ion exchange lifting pump, and the water production tank is communicated with the sodium ion exchange device through the ion exchange lifting pump.
- The sedimentation mechanism includes a tank body and a tubular microfiltration membrane arranged in the tank body.
- The precipitation mechanism includes a casing and a tubular microfiltration membrane arranged in the casing.
- The sodium ion exchange device comprises a plurality of sodium ion exchangers connected in series.
- The hard removal system also includes an ultrafiltration lift pump that communicates with the self-cleaning filter, and the RO concentrated water enters the self-cleaning filter through the ultrafiltration lift pump.
- The reverse osmosis device is a multi-stage continuous desalination reverse osmosis device.
Compared with the prior art, the beneficial effects of the present utility model are at least as follows:
The hardening system of residual RO concentrated water after reuse of PTA sewage can effectively remove calcium and magnesium ions in RO concentrated water, so that the hardness of the treated water can meet the requirements of entering the concentrated water reverse osmosis device, and reduce the process burden for the subsequent evaporation and crystallization system.