Issues encountered during the operation of 6.5MPa aerospace gasification furnaces
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This post was last edited by aqiao1011 on 2023-8-26 at 14:40. It is a space furnace with a pressure of 6.5 MPa, capable of handling 3,500 tons of coal per day. Severe problems arose during operation, namely a high level of by-product formic acid. According to the Aerospace Institute, this is a by-product that occurs under high pressure and is difficult to address. The increase in formic acid concentration directly led to a low pH value in the graywater treatment process, resulting in high levels of total iron in the graywater. The pH value of the black water flowing into the sedimentation tank was only 5.8, and the pH value of the graywater was also very low. To do this, the pH value can only be adjusted by adding alkali. Has anyone else encountered this situation? Where is the best place to add alkali? Additionally, when the same coal was used in the other 4.0 MPa gasifiers and flocculants at the same concentration were added, the ash water from the low-pressure gasifiers was very clear, whereas that from the high-pressure gasifiers was white, with suspended solids levels of around 40–50 ppm. The results of the pilot tests were good, but the water turned white when it was actually applied. Is this situation related to the medication? Under the 6.5 MPa and 4.0 MPa processes, what changes occur in ash content or gasification efficiency, resulting in such a large difference in flocculation and sedimentation effects?
This issue may be related to the increased formation of formic acid under the operating conditions of high-pressure space vaporizers. An increase in the concentration of formic acid leads to a lower pH value in the graywater treatment process, and it also affects the flocculation efficiency of the flocculants. According to the Aerospace Institute, by-products under high pressure are difficult to deal with, so other measures may need to be taken to solve this problem. One method is to adjust the pH value by adding alkali, in order to raise the pH of the graywater and reduce the total iron content. Additionally, trying to change the concentration of the flocculant added, or using other types of flocculants, can help improve the transparency of graywater. It should be noted that due to differences in operating conditions and pressure between high-pressure gasifiers and low-pressure gasifiers, they may exhibit different performance when dealing with by-products and ash water. If the problem persists and cannot be resolved, it is recommended to engage in further communication and consultation with the Aerospace Institute to seek professional advice and solutions. .
Thank you for your answer. Do other vaporizers have this problem? For example, do the 8.7 MPa multi-nozzle vaporizers of East China University of Science and Technology, as well as the 6.5 MPa Texaco vaporizers, experience such problems during operation?
I’m sorry, I can’t understand your question. Is there anything I can help you with? .
I mean, have issues such as a high content of by-product formic acid and poor quality of the graywater in the sedimentation tank occurred in other high-pressure (6.5–8.7 MPa) gasification systems? Do these problems only occur in space furnaces?
6.5 The water-coal slurry is acidic in the quenching chamber, but not to such a low degree. If it is formic acid, this may be related to the carbonylation reactions that can occur under high temperature, high pressure, and high CO levels. What is the reason for the high iron content? It can’t be corrosion caused by low pH, right? As for flocculants, it is recommended to work together with the chemical manufacturers to explore whether it is possible to adjust the pH value before the liquid enters the sedimentation tank.
This is a typical issue related to the design of water balance. It needs to be interpreted in conjunction with the drawings. This month, a technical meeting for the space furnace will be held at the headquarters. It would be better for us to study it together then. If you want to message me privately, please add me on WeChat at 15326774377
Thank you for the reply. It was the Aerospace Academy itself that said the formic acid level was high; it’s probably a design issue. And the pH value of the entire graywater system must be lower than that of the gasification furnace at 4.0 MPa. The manufacturer also added alkali, but the effect was not very good. Without adding alkali, the pH value of the water entering the sedimentation tank is only around 6.2, which **increases the corrosivity** of the system. After adding alkali, the pH value was adjusted to around 8.0, but this affected the flocculation efficiency of the flocculant; the turbidity and suspended solids in the gray water at the overflow weir were high, causing the water to turn white.
Recently, a strange problem has arisen with this system: the pH value of the water entering the sedimentation tank (from which we take samples of the true flash water) is around 5.8, while the pH value of the graywater at the overflow weir of the sedimentation tank is as high as 8.1, an increase of 2.3 units. These past few days, the manufacturer has not added alkali to the system, so alkaline substances cannot be discharged into it. It really flows out to the overflow weir of the sedimentation tank; only cationic amides were added, at a concentration of about four to five ppm, so it certainly won’t affect the pH value of the graywater. At normal pressure, even if acidic gases escape, the increase won’t be that much. Have any of you experts encountered this situation? Are there any other possibilities?