Chemical descaling of the washing water pipeline in the crude syngas scrubber tower
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The wash water pipes in the washing tower of a certain gasification unit have developed scale, and pieces of this scale often fall off and block the spray nozzles and air coolers, causing great trouble. I would like to seek advice from experts: The analysis of the sample is as follows: Al2O3: 13.06%, CaO: 0.76%, SiO2: 7.09%, NaO: 7.20%, Fe2O3: 0.96%, S: 2.6%. Regarding the acid dissolution test, the dried scale samples were placed in an ammonium sulfonic acid solution that was heated to 70–80°C and contained about 1.5% of this acid. After 2 hours, the undissolved portion was filtered out, dried, and weighed; the dissolution rate was around 30%. Scale cannot be largely dissolved by dilute nitric acid or dilute hydrochloric acid either. This pipe is made of duplex steel seamless tube, and mechanical cleaning is unlikely to be effective. I was wondering if there are any better chemical cleaning methods?
Scaling in the washing water pipes of the crude syngas scrubber tower; the key is to control the graywater. Chemical descaling is rarely used.
Online descaling during production was considered, but the idea was abandoned after a risk assessment of the system. What’s troubling now is that the thin deposits on the inner walls of the pipes are difficult to remove manually even during shutdowns, and this could cause problems in the future. There are diameter changes and elbows in the pipes, making it difficult to use a \"pipe pig\" for cleaning; moreover, cutting and cleaning the duplex steel pipes is not an option either. It’s really frustrating
There is relatively little research on scaling in production pipelines in China at present; initially, Lunan and the Wei River regions organized scientific and technological efforts to address this issue, achieving some results. Currently, various gasification plants are organizing personnel to conduct research. Since both coal and water are variables, it varies from place to place. But I haven’t heard of chemical cleaning being used; mechanical descaling is what’s employed instead. You could consider using equipment for softening scale (such as overclocking, quantum rings, etc.) and give it a try.
Ultrasonic descaling can be tried
It should be possible to remove it online, right? What is the effect of offline descaling? Could you introduce a few practical application cases?
Chemical cleaning should be avoided as much as possible in the water washing pipeline system; elbow fittings can be made using tees along with blind flanges to facilitate disassembly for cleaning. Previously, there was a chemical cleaning solution for waste boilers, but the scale mainly consisted of FES and NIS. How thick is the scale layer? Is the existence form of scale in an oxidized state? ? ? ?
Thank you for your attention. The thickness of the slag is around 0.5mm to 1.5mm. The analysis results regarding the form in which the slag exists are expressed in terms of oxidation state. See the first floor for details
Controlling gray water is indeed key to preventing scaling in pipes, but there are many factors that can affect scaling. It might be due to the presence of large amounts of scaling-causing elements in the gas coming from upstream, or it could be because the fresh water added contains such elements as a result of inadequate treatment. It may also be caused by various internal factors, such as a low volume of circulating water, which leads to scaling in the pipes. So, once scaling has occurred, how can it be removed? I have seen it cleaned using high-pressure water before.
With the current position of the flanges, there may be dead zones when using a high-pressure water gun; I want to carry out a thorough cleaning first, and then implement control measures during subsequent operation. :)
Try it with hot sodium hydroxide solution; it should work.