Carbon dioxide stripping process flow

The main differences between the carbon dioxide stripping method and the aqueous solution full-circulation method: 1. The CO2 stripping method features a high-pressure zone, where most of the unreacted substances are recycled within this high-pressure zone； Aqueous solutions are mainly recovered in an absorption system. 2. The CO2 stripping method does not have a medium-pressure system; it only has a low-pressure system, resulting in a shorter process flow ； The aqueous solution method has medium-pressure and low-pressure systems, with a long process flow. 3. The evaporation systems for these two processes are basically the same. The main difference is that the CO2 stripping method generally operates on a larger scale due to the large amount of steam produced as a by-product; it features a booster for the second-stage evaporation, whereas most aqueous solution systems do not have one (although a few manufacturers do). This post was last edited by Boating on the Five Lakes on 2009-3-10 12:48.]

Evaporation of urine: The urea solution from the bottom of the distillation column is sent to the flash tank after being depressurized by a level control valve in the liquid level tank, at a pressure of approximately 0.015 MPa(A). As the temperature dropped from 135°C to 91.6°C, a considerable amount of water, NH3, and CO2 flashed off. It enters an evaporation condenser to be condensed. The urine leaving the flash tank has a concentration of about 73% (wt) and flows into the urine storage tank, from where it is pumped to the first-stage evaporator. The urine separated in a separation section of the evaporator is sent to the second-stage evaporator, where it is concentrated to about 99.7% (wt) molten urea at 0.0033 MPa(A) and 140°C. After separation, the molten urea is pumped by a melt pump to a rotating nozzle located at the top of the granulation tower for granulation. The resulting granulated urea is transported by a belt conveyor to the packaging building for packaging. The flash vapor is sent to the flash condenser for condensation, while the non-condensable gas combines with the vapor from stage 1 and is sent to the stage 1 evaporation condenser for condensation; the pressure difference between the two is adjusted via valves. The uncondensed gas from the first-stage evaporation condenser is drawn to the final condenser by the first-stage evaporation ejector ； The secondary evaporation vapor is pressurized by a booster and then sent to the secondary evaporation condenser for condensation. The non-condensable gas is drawn by the secondary evaporation ejector (A) to the secondary evaporation post-condenser for condensation, while the non-condensable gas drawn by the secondary evaporation ejector (B) is sent to the final condenser for condensation; the non-condensable gas is then discharged through an exhaust stack. This post was last edited by lxq700918 on 2009-3-11 17:24.]

High-pressure cycle: The CO2 gas from the compressor enters the stripping tower. The gas phase from this tower, along with ammonia pumped out through the ejector and methanamine pumped from the high-pressure scrubber, mixes together and then enters the high-pressure methanamine condenser. There, it is used to produce urea at the bottom of the synthesis tower. The liquid phase then enters the stripping tower to remove any excess ammonia and carbon dioxide, after which it proceeds to low-pressure decomposition units for further purification of the urine-like substance. The gas phase from the synthesis tower passes through the high-pressure scrubber, where it is absorbed by methanamine pumped in, thereby removing ammonia and carbon dioxide; it then goes on to the tetraamine absorption tower for further absorption before being released

The difference in evaporation itself lies in the carbon dioxide stripping process: in this case, the urine enters the urine tank via flashing, and then is pumped into the evaporation system by a urine pump. In the case of evaporation of aqueous solutions, the urine goes directly from the flashing tank to the first stage of evaporation. There is also the traditional aqueous urea evaporation system, where the evaporation heater and separator are separate, with feed entering at a tangential direction; whereas in the carbon dioxide stripping process, the evaporation heater and separator are integrated together, and the urine enters directly. However, the carbon dioxide stripping process can also adopt a design based on aqueous solution evaporation.

Are the carbon dioxide stripping evaporation heater and separator integrated? ? The evaporation in our carbon dioxide stripping process is separate.

The differences between the carbon dioxide stripping process and aqueous solutions are as follows: 1. The operating pressures differ; the pressure in the high-pressure system for the carbon dioxide stripping process is generally 14.4–15.0 MPa, while the operating pressure for aqueous solutions is around 20 MPa. 2. In the carbon dioxide stripping process, the high-pressure system transitions directly to the low-pressure system via a pressure reducing valve; there is no medium-pressure system. 3. The carbon dioxide stripping process has a short flow path, but it requires a high purity of the feed gas. 4. The carbon dioxide stripping process system has high requirements for H2S, H2, and CO present in the feed gas; dehydration is necessary before the gas enters the system. Furthermore, the oxygen addition amount to the feed gas must be strictly controlled to prevent equipment corrosion. Especially the stripping tower. 5. The evaporation aspect is similar to that on the fifth floor, except that the \"carbon dioxide stripping evaporation heater and separator are integrated.\" This post was last edited by Boating on the Five Lakes on 2009-3-13 01:12.]

Our factory originally used the modified C process with full aqueous solution circulation; it underwent technological upgrades by introducing TEC’s ACES21 process. The CO2 stripping method is currently being used. The original synthesis tower was retained, with a stripping tower and an ammonium methylate condenser added. A two-stage decomposition is employed corresponding to a two-stage recovery, and the original crystallization granulation is replaced by evaporation granulation. After two-stage evaporation, urine with a concentration of 99% is sent to a granulation tower for granulation. This post was last edited by Fan Zhou Wu Hu on 2009-3-13 22:30.]

Excuse me, on the 3rd floor, what is the typical level that should be maintained for the urine tank? How many m³ is your urine tank capacity? What is the Bi content in the finished product? Is it possible to go straight into a section using the aqueous solution circulation method? Personally, I think the pressure is similar to that in aqueous solutions, so there should be no problem.