How do various fertilizer plants address the high ammonia nitrogen content in urea wastewater in order to ensure discharge meets regulatory standards?
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How is deep hydrolysis working? Has membrane treatment been used to address the issue?
Deep hydrolysis can fully meet the requirements. We use products from Monsanto; those made in China are also good quality.
Even Monsanto’s solution may not meet the requirements. We developed our own system; it has been in use for a few months, and we’re still working on improving it
It uses technology from Monsanto in the United States (now called Monmoc); the design was carried out locally, and one set of our company’s equipment was put into operation last month. It requires little operation, but due to issues related to analysis and the recovery of ammonium hydroxide solution, it has not yet passed the acceptance tests.
We have been using Monsanto’s deep hydrolysis system for three years now; it’s working fairly well, except that the recirculation pump often has its mechanical seals burn out and require repair. However, the pH of the treated hydrolysis wastewater is only 4.0–5.0. In the past, it was directly fed into the jackets of the gas boilers, which caused severe corrosion of the steam rising pipes; as a result, five boilers leaked within just one month. The jacket also suffered from corrosion to varying degrees; simple alkaline treatment did not resolve the issue, and it was only after installing an additional wastewater reprocessing unit that the problem of wastewater reuse could be basically solved. However, this set of reprocessing equipment is not very suitable for treating hydrolyzed wastewater, and various problems often arise; after some minor modifications, it can basically meet the requirements for use.
Our aqueous solution circulation can achieve rank 0
The key to this technology lies in determining whether the design of the reaction tower and the hydrolysis tower is reasonable. Ensure that the wastewater remains in the stripping tower for a sufficient duration, in order to achieve complete hydrolysis of the urea contained within it. It is recommended to design the analysis tower at an operating pressure of 3 to 4 kilograms.
On the 7th floor, even with full circulation of the aqueous solution, it’s not possible to recover all the water. Our factory uses Far East’s hydrolysis process; the ammonia nitrogen level is below 30, and the urea level is around 10, so it can be discharged without any issues.
Our factory has also installed a set that is working well; it’s from Jiangsu Linggu Chemical – you can come and take a look
The technology of deep hydrolysis of urea: its application at Mianyang Meifeng Plant No. 1. This plant utilizes technology from the American company Monsanto; the total investment in the entire setup amounts to 11 million yuan, of which 228,000 dollars is spent on licensing fees for the patented technology； Use steam at a pressure of 1.3 MPa ； Commissioning date: November 2005. Currently, another set at Mianyang Meifeng Plant 2 is under construction and is set to be put into operation soon. 1. Design parameters: Waste liquid treatment volume: 22 m3/h ； The ammonia content in the waste liquid is 8.73% (w/w) ； Urea content in the waste liquid: 0.64% (w/w) ； Ammonia content in the treated wastewater ≤ 5 ppm ； The urea content in the treated wastewater is ≤2 ppm, with a steam consumption of 200 kg/m3 of treated wastewater. 2. Operating parameters: Waste liquid processing capacity: 11 m3/h ； The ammonia content in the waste liquid is 6.5% (w/w) ； The ammonia content in the treated wastewater is 3~4 mg/l ； The urea content in the treated wastewater is 0.3 mg/l. 3. Equipment failure: Since its commissioning, as the operating load of the equipment has not reached the designed level, the treated wastewater has always met the specified standards. 4. Consumption: Medium-pressure air: ~1.1 m3/h ； Medium-pressure carbon dioxide (compressed at stage 3): 0 m3/h (stripping is not active due to low load) ； 1.3MPa steam: ~2.67t/h (it is also said that the instrument is inaccurate; the actual value is 2.1~2.3t/h) ； Circulating cooling water: ~240 m3/h ； 5. Process flow and related parameters: The liquid to be treated (temperature: 15°C, flow rate: 11 m3/h) is sent to a high-efficiency heat exchanger via a booster pump; after heat exchange (temperature around 174°C), it is directed to the hydrolysis stripping tower. Within this tower, desorption occurs as the fluid flows downward through the tray layers. The desorbed waste liquid (temperature: 189°C) is discharged from the bottom of the tower. After exchanging heat with the liquid to be treated in the high-efficiency heat exchanger (temperature: 50°C, flow rate: 14.4 m3/h), this waste liquid is sent to the boiler. The desorbed gas (temperature: 157°C, pressure: 1.05 MPa) is condensed in the desorption condenser; the condensate (temperature 68.5°C) is sent by a booster pump to the hydrolysis stripping tower and the first-stage external cooler respectively, to serve as reflux liquid and absorption liquid ； The gas is sent to the second cycle and first cooler for ammonia recovery. Medium-pressure air (flow rate: 1.1 m3/h), carbon dioxide, and medium-pressure steam (pressure: 1.25°C, flow rate: 2.7 t/h) all enter the lower part of the hydrolysis stripping tower, where they heat the treatment liquid directly.
I wonder if the waste liquid from your factory doesn’t meet the standards? Is the ammonia and urea content in the waste liquid produced during the manufacturing process too high? After desorption and hydrolysis in our plant, the ammonia and urea contents in the waste liquid are reduced to below 5PPM; this water can be purified for use as pure water, from which steam can be generated