Regarding the gasification ash water system

Additionally, the pipeline from the gasifier quench chamber to the high flash point also became clogged. The pH of black water is around 5.5. By adding alkali to raise the pH above 8, a large amount of white flocculent material is formed, while the supernatant remains a transparent liquid. When the pH is adjusted to around 4, the turbidity of the black water increases and substances precipitate out. Have any of you encountered this situation?

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1. Coal used for gasification has certain requirements regarding sulfur content: the international standard GB/T29722-2013 \"Technical specifications for raw coal used in fluidized bed gasification\" specifies that the sulfur content should be less than 3%; of course, the lower the better. Since coal used for gasification contains high levels of sulfur, the black water generated by the gasification furnace contains a large amount of acidic gases, which are highly corrosive and can cause damage to the equipment and pipelines in the gasification furnace. 2. What is the cause of the blockage in the pipeline from the quench water pump to the quench ring in the gasification system? The question posed is too general; it should be described in more detail – what type of furnace does your device use, and what is its size? How much coal is consumed? What type of coal should be used? What is the operating pressure? Regarding the quality of water used for supplementation and other such factors, you must be referring to normal operation. If, during normal operation, the quench water pump in the gasification system becomes clogged in the quench ring pipeline, it’s definitely due to scaling in the system, which indicates that the effect of the ash and water dispersant is insufficient. 3. The pipeline from the gasifier quench chamber to the high flash point also became clogged. It depends on how long the system operates. Generally, this phenomenon does not occur within a single production cycle, unless it is during the startup of the system; in such cases, the principle of thermal expansion and contraction may come into play. Often, improper handling by the operators on site can cause scale to break off from the inner walls of the black water pipelines, which then gets stuck inside the pipes or at the bends, leading to blockages in those pipelines.

The sulfur content in the coal used for gasification should not be too high, as this can accelerate corrosion of equipment and pipelines; however, it doesn’t mean that the lower the sulfur content, the better. In particular, the carbon monoxide conversion process in the subsequent systems requires a certain amount of sulfur in the gas, as the cobalt-molybdenum catalysts used in this process only exhibit catalytic activity when they are in a sulfided state. The quality of vaporized water is generally weakly alkaline.

Please find the article: Analysis of Texaco’s gasification ash water treatment process. Thank you!

Additionally, it should be noted that there are also blockage issues in the pipes running from the quenching chamber of the gasifier to the high flash point vessel. Typically, the quenching water is at around 250 degrees Celsius and under a pressure of 6.5 MPa inside the furnace; upon exiting the gasifier, it undergoes rapid cooling and pressure reduction. The salts present in this water, along with large amounts of ash, precipitate quickly and adhere to the pipe walls, forming scale. Therefore, when providing on-site services for ash water treatment, we generally recommend that the client replace the first 5 meters or so of pipes running from the quenching chamber to the high flash point vessel with flange connections, to facilitate maintenance and cleaning and ensure the safe and stable operation of the gasification unit.