Countermeasures to prevent carbon buildup on reforming catalysts and what to do after carbon buildup

_{① Carbon build-up mechanism. The alkaline additives of the steam reforming catalyst generally adopt alkaline minerals and alkaline earth oxides and other additives to jointly resist carbon to achieve the best anti-carbon accumulation performance. Alkaline minerals make alkali metals form a stable structure, alkali metals are released slowly during the process of use, alkaline hydroxide formed by alkali metals in contact with steam is the catalyst for the reaction between C and H2O, so the alkaline additives in the catalyst not only satisfy the demand for anti-carbon deposits, but also prolong the service life of the catalyst to varying degrees.}

_{② Judgement of carbon accumulation phenomenon.}

_{Once carbon build-up occurs in the reforming catalyst bed, the phenomena shown are spots, hot spots, red tubes and increased bed resistance, and increased residual methane content at the reforming outlet. Severe carbon build-up can lead to blockage of the furnace tube, resulting in an increase in differential pressure, inability of the reaction medium to pass through, a decrease in reaction heat absorption, and ultimately the appearance of a bright tube. The appearance of bright tube is a very serious matter, and if no measures are taken, the phenomenon of pipe burst often occurs.}

_{Countermeasures to prevent carbon build-up}

_{Select clean raw materials. In order to increase the amount of hydrogen produced per unit of raw material or to reduce the consumption of raw material per standard cubic metre of hydrogen, preference should be given to selecting hydrocarbons with a small average molecular weight, light specific gravity, low content of aromatics, low content of cycloalkanes, and low content of olefins as raw materials. Reduce the rate of carbon build-up on the reforming catalyst by stabilising the water-to-carbon ratio, the feed quantity and the combustion of the reformer nozzle during normal production.}

_{Measures to be taken after carbon build-up on the reforming catalyst.}

_{When the reforming catalyst is slightly carbonised, the method of gentle carbon burning can be adopted. That is, increase the conversion water to carbon ratio (about 5.0), reduce the production load (about 60%), with a certain amount of reducing gas, without affecting the hydrogen production conditions of the hydrogen plant to eliminate.}

_{Cumulative carbon is serious, must be removed from the raw material, with the water vapour charcoal, steam volume for normal operation of 30 ~ 40%, the pressure of 1MPa or so, strict control of each point of the bed temperature shall not be higher than the temperature of the normal production, charcoal burning time is generally 4 ~ 10h, the conversion of the export of CO2 down and stabilised to a minimum value, the end of charcoal burning. After the end of charcoal burning, the oil can be put into the oil only when it is reduced again. If the end of charcoal burning still can't restore the normal operation, the catalyst should be replaced.}

_{The reaction formula of charcoal burning is: C+2H2O→CO2+4H2}