Synthetic Ammonia Weekly Topic 2011/11/21-11/27: How is the power for the heating cycle in the nitrogen cycle provided
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This post was last edited by Yan Qiusheng on 2011-11-21 07:52. Weekly topic on synthetic ammonia: How is the power for the nitrogen cycle and heating cycle provided? What are the advantages and disadvantages? During the cold start-up of the synthesis system, the nitrogen circulation heating process involves raising the temperature of the first reactor section, the second reactor section, and the high-activity catalyst bed in the conversion system, with the temperature being increased according to a specified curve. Once the relevant temperature parameters reach the set values, steam is used to further increase the temperature. It is understood that the devices used to provide power for nitrogen circulation vary. May I ask how your factory provides the power for the nitrogen circulation heating process? What are the advantages and disadvantages? Higher scores will be given as appropriate based on the practicality and innovation of the answers; everyone is encouraged to participate actively.
This post was last edited by shfuchenko on 2011-11-21 at 22:48. The power for the nitrogen circulation and heating cycle in our installation’s conversion system is provided by an external Roots blower; it is necessary to open two blind flanges, and additionally two blind flanges must be installed at the inlet and outlet of the low-pressure transformer in order to enable the nitrogen circulation and heating process. As a nitrogen compressor, the external Roots blower has the advantage of being relatively easy to operate. The drawback is that sometimes the circulation volume may be insufficient, resulting in different heating rates across various sections of the furnace tubes; however, this problem does not occur when there are a large number of burners. At the same time, among the several indicators for heating via nitrogen circulation in our system, the rate of high temperature increase is relatively slow ； Also, nitrogen needs to be continuously injected into the nitrogen circulation system. May I ask how your nitrogen circulation power is supplied, and what are the existing problems? Everyone is welcome to actively discuss.
:) Hehe, not bad. Give it some support
At first, when looking at the ammonia synthesis process, it seems a bit like a hydrogen production process just by reading the description below. Our hydrogen production process works in a similar way: desulfurization, conversion, medium-temperature transformation, followed by heating with nitrogen; after reaching a certain temperature, steam is used for further heating. In the hydrogen production process, compressors can be used to increase pressure, but the capacity of these compressors is relatively small, so they are unable to achieve the necessary speed for rapid heating, which results in the temperature at the exit of the conversion stage being lower than that at the inlet – this is due to insufficient flow rate. Another method for heating with nitrogen involves using high-pressure nitrogen at the inlet, with no recycling of the gas at the outlet; it’s simply released, thereby ensuring a high flow rate without the need for compressors, and thus allowing for a fairly fast heating rate… It’s just a waste though. Normally, heating takes 10 hours… which is quite a waste
The power for the nitrogen circulation in our plant is provided by air compressors that generate pressure. The typical flow rate of nitrogen during circulation is around 22,000 Nm3/h, while the outlet pressure from the air compressors is generally around 0.8 MPa. The nitrogen circulation helps to raise the temperature of nitrogen, but heat must also be supplied through burners located at the top of the furnace; usually, 3–4 such burners are required to achieve the desired temperature rise. Generally, raising the temperature of nitrogen results in poor temperature elevation, but the temperature can be increased after discharging waste from the boiler. I think the advantage is that the nitrogen circulation rate remains basically stable, allowing for heating at a normal nitrogen heating rate ； The disadvantage is that 12 blind flanges need to be opened for nitrogen circulation, which results in a significant waste of labor during maintenance.
Our company supplies nitrogen through air separation, using instrument air compressors to create a pressurized cycle. But we only use it when driving originally or after replacing the catalyst. Overall, it’s quite convenient and makes the most of what it has
In our factory, the temperature increase for the transformers is achieved using air, steam, and semi-water gas in a sequential manner. The power is provided by a locomotive
Let’s talk about ours: Our heating process is similar to what the original poster described, except that it involves circulation using a raw gas compressor. Two blind flanges need to be installed; when switching to steam for heating, those flanges have to be removed again. To save time, it’s possible to use two valves along with a drain valve, with the blind flanges placed between the valves. This way, heating can be started directly using steam, thereby saving time that would otherwise be needed for pressure relief and the use of blind flanges. For reference~!
We use a fully low-temperature variation process; during heating, nitrogen is used in combination with semi-water gas to facilitate cyclic heating for sulfidation. The nitrogen blower provides the power, with an outlet pressure of 0.1 Mpa and a circulation rate of 15,000 Nm3/h. The electric heating furnace provides the heat, and the temperature can be raised to 450°C during vulcanization. The disadvantages include a large number of heating and vulcanization guide plates, numerous leakage points during vulcanization, high temperatures when removing the guide plates after vulcanization, as well as high levels of toxic gases such as H2S and CO, posing risks of poisoning and fire.
Nitrogen circulator – good and very useful