Brainstorming: The color of light-weight soda ash
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This post was last edited by steinback on 2012-5-22 at 00:00. For many factories, the whiteness of light soda ash isn’t a problem; however, in our factory, we’ve noticed on multiple occasions lately that the products have poor whiteness. To the naked eye, they appear somewhat yellowish; when dissolved in water, the water turns slightly yellow, and in severe cases, it becomes dark yellow. I hope all the experts can explain this? ? ? Supplement: For a long time, the H2S content in our CO2 has been between 100 and 200, while the iron content in the alkali has always fallen within the range of first-class and qualified products. Since the relevant supervisors believe that adding sodium sulfide can inhibit iron formation, on average, 1 pack of 25 kg of sodium sulfide is added per shift. However, when switching towers, the caustic soda tends to turn grayish in color. After reducing the amount of sulfur added, the caustic soda turned yellow again. Nevertheless, the iron content remained within the range of first-class and acceptable grades. Once we reverted to adding 1 pack per shift, the caustic soda no longer appeared as yellow. This situation utterly baffles me.
What is the iron content in soda ash? This situation is generally caused by a high iron content.
Previously, we’ve experienced graying of the material; this was mainly due to the high H2S content in the CO2 gas. However, we’ve never encountered any yellowing phenomenon at all
It might be that the iron content in the raw materials exceeds the standard.
Moderator, when the alkali treatment results in graying, what’s the H2S concentration in your area?
Reply to #4 by Han Yun: The iron content is within the acceptable range; it doesn’t exceed the limit. It’s just that it isn’t white enough.
The yellowing of soda ash is likely caused by elemental sulfur; the sulfur content can be appropriately reduced
Reply to 5# steinback: The H2S level in the CO2 gas has exceeded 500 mg
Reply to #7: Brother machun*ao, your thoughts align with mine. I believe it’s related to S and its compounds. For a long time now, the H2S content in our CO2 has been between 100 and 200, while the iron content in the alkali has always fallen within the range of first-class and qualified products. Since the relevant supervisors believe that adding sodium sulfide can inhibit iron formation, on average, one 25-kg pack of sodium sulfide is added per shift. However, when switching towers, the alkali tends to turn grayish in color. After reducing the amount of sulfur added, the alkali turns yellow instead. Nevertheless, the iron content remains within the range of first-class and acceptable grades. So, I’m very confused about this.
It’s probably caused by high levels of hydrogen sulfide. After being left for some time, the hydrogen sulfide will evaporate, and the ash alkali will return to its normal trona color.
Elemental sulfur cannot exist alone in soda ash. When the tower was repaired, the alkali turned yellow; this is probably due to poor sulfur removal during tower cleaning.