I would like to ask about the dechlorination process technology for compound fertilizers

The dechlorination process for compound fertilizers involves using alkaline substances such as sodium hydroxide and calcium carbonate to neutralize the chlorine elements in pesticides and fertilizers, converting them into harmless substances like sodium chloride or potassium chloride that are not volatile. For the step of hydrogen chloride absorption, soda ash is typically used for neutralization, as it can react with hydrogen chloride to produce sodium chloride and water, while also neutralizing other acidic substances. As for why dilute ammonia solution is not used, it may be because it releases ammonia gas, which can cause environmental pollution and safety hazards; moreover, the cost of dilute ammonia solution is high, while using soda ash is more economical and practical. .

It is mainly due to considerations of reaction kinetics and economics; certainly, sulfuric acid is cheaper while dilute ammonia is more expensive.

Dilute ammonia water is also slower in terms of reaction speed

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This post was last edited by qugd on 2023-4-21 at 17:49. 1. Ammonia is a weak base, and its efficiency in absorbing acids is low; in the later stages of absorption, it is unable to effectively absorb acidic gases； 2. Ammonia has significant volatility; when its concentration is high at the beginning of absorption, it will volatilize along with the exhaust gases, leading to ammonia loss, so it is necessary to find ways to control the ammonia content in the exhaust gases ； 3. Ammonium chloride has low value; although it can be incorporated into compound fertilizers, considering factors such as raw material costs, operating expenses, and exhaust gas testing, using ammonia water for absorption is not economically advantageous ； 4. The absorption of hydrogen chloride by ammonia is significantly affected by environmental and climatic temperature conditions; more parameters are required for automatic detection and control, which adds complexity to operation and management.

The main purpose of the dechlorination process for compound fertilizers is to remove chlorides from the raw materials, while simultaneously producing nutrients such as nitrogen and phosphorus. Dilute ammonia water is a commonly used absorbent for removing hydrogen chloride, but it is not the only option available. Other absorbents include sodium hydroxide, calcium carbonate, calcium hydroxide, lime, etc. Sodium hydroxide is also a common absorbent, as it can form sodium chloride, thereby turning pollutants into precipitates that are not volatile, thus achieving the purpose of purifying gases. Regarding whether to use dilute ammonia water as an absorbent, each manufacturer’s choice may vary due to factors such as technology, economics, and environmental considerations; a decision must be made after evaluating the specific circumstances.