Research On The Corrosion Properties Of The Black Liquor Gasification Stove Alkali Dissolution Interior Materia

The technology of black liquor gasification started late in China. The black liquor spray gasifier was produced based on the process of Texaco coal-water slurry gasification. Black liquor gasification experiments with bagasses were carried out by the technology of atmospheric oxygen gasification. And the optimal technological conditions were determined. However, studies on the corrosion of the gasifier chamber, lining crack and the corrosion of alkali dissolved room lining materials need to be deepened.Materials in the alkali dissolved room of black liquor gasifier had a high temperature and a strong turbulence. The temperature reduced from the middle to the edge by gradient. And the place that touched with fusant was overheating in the alkali dissolved room. The ash content of black liquor gasification contained basic compounds like Na2CO3, Na2S. The basic compounds mixed with circulation absorbing liquid from alkali adsorption tower. And alkaline solution of Na2CO3, Na2S and NaOH was obtained, in which the temperature was125-225℃. Therefore, this technology was imitated to research the corrosion behavior of201、304、316L stainless steel. The research contents included the following three sections:1.The design of the corrosion experiment simulation reactor With304stainless steel for material, corrosion reaction tank was designed. Relevant qualification unit was entrusted to process.They designed and manufactured control heating system at the same time.2.Corrosion experiment researchCorrosion experiments of201,304and316L were carried out using the corrosion mediums of Na2CO3, Na2S and mixture solution of the both. Corrosion materials were corroded for168h under a temperature range of125-225℃. Corrosion level was determined by gravimetic method and depth method.Results showed that the three materials could be the lining materials of alkali dissolved room in black liquor spray gasifier. SEM results suggested that general corrosion was observed in201and304, while local corrosion (pitting corrosion) appeared in316L. Corrosion level of the three all reached corrosion resistant level, and could be used as lining materials of alkali dissolved room.3. Corrosion products analysisCorrosion products are analysis through XRD、SEM and EDS. The results are as follows:(1)the main products of201stainless are Fe9S11, FeO, and Fe3O4in a lower temperature, and Fe9S11, FeO in high temperature.(2)In the same corrosive medium, the main products of304stainless steel are all FeO and Fe9S11, and they don’t change with the variation of corrosion temperature.(3)316L stainless steel appears the similar experimental phenomenons with 304stainless steel, but its main products are Fe9S11, FeO, Fe2O3and Fe3O4.