CN102259896A - Method for extracting sodium thiocyanate from coking desulfurization waste liquid - Google Patents

Abstract

The present invention is a method for extracting sodium thiocyanate from coking plant desulfurization waste liquid, which is characterized in that: coking desulfurization waste liquid is added with 2-6wt% activated carbon, heated to 70-90°C and kept stirring for 1-2 hours, filtered, and the filtrate Add sulfuric acid to the closed container to pH = 3.5-4.5, heat to 60-80°C and keep stirring for 1-2 hours, the escaped sulfur dioxide gas is drawn out with a catheter and absorbed with dilute ammonia water, filtered after the reaction, and the filtrate is in a closed container Add sodium hydroxide in the same amount as ammonium thiocyanate in the filtrate and calcium hydroxide in the same amount as ammonium sulfate in the filtrate, heat to 50-70°C and keep stirring for 1-2 hours, the released ammonia gas Lead out with a catheter and absorb it with water to form dilute ammonia water. After the reaction is completed, filter, and the filtrate is evaporated and crystallized to obtain sodium thiocyanate product.

Description

Method for extracting sodium thiocyanate from coking desulfurization waste liquid

Technical field:

The invention belongs to the field of recovery and treatment of chemical wastewater, and in particular relates to a method for extracting sodium thiocyanate from coking desulfurization waste liquid.

Background technique:

At present, many domestic coking plants adopt the HPF desulfurization and decyanation process, which must discharge part of the desulfurization waste liquid and replenish water to maintain a high desulfurization efficiency. Coking desulfurization waste liquid contains a large amount of ammonium thiocyanate, which is a chemical product with high added value. Extracting ammonium thiocyanate from coking desulfurization waste liquid is a feasible method for resource treatment of desulfurization waste liquid.

At present, the main method of extracting ammonium thiocyanate from coking desulfurization waste liquid in China is vacuum distillation and concentration, followed by fractional crystallization to obtain ammonium thiosulfate and ammonium thiocyanate respectively. The ammonium thiocyanate purity obtained by this method is relatively low, generally between 70-90%, and the purity is difficult to reach more than 95%. The use of ammonium thiocyanate with lower purity is limited, the price is low, and the economic benefit is relatively poor. How to improve the salt extraction method and extract high-purity sodium thiocyanate from coking desulfurization waste liquid is of great significance.

Contents of the invention

The invention uses coking desulfurization waste liquid as a raw material to extract sodium thiocyanate product with a purity greater than 96%.

The specific operation of the present invention is as follows: add 2-6wt% activated carbon to the coking desulfurization waste liquid, heat to 70-90°C and keep stirring for 1-2 hours, filter, add sulfuric acid to the filtrate in a closed container to pH=3.5-4.5, heat to 60 Keep stirring at -80°C for 1-2 hours. The escaped sulfur dioxide gas is drawn out with a catheter and absorbed with dilute ammonia water. After the reaction is completed, filter it. Add sodium hydroxide in the amount of ammonium thiocyanate and other materials in the filtrate to the filtrate in a closed container. and calcium hydroxide in the amount of ammonium sulfate and other substances in the filtrate, heated to 50-70°C and kept stirring for 1-2 hours, the escaped ammonia gas was drawn out with a catheter and absorbed into dilute ammonia water, filtered after the reaction, and the filtrate Evaporation and crystallization to obtain sodium thiocyanate product.

Detailed ways

Example 1

Take the coking desulfurization waste liquid provided by Tongling Xinyaxing Coking Co., Ltd. After analysis, the main components of the waste liquid are: NH ₄ SCN 183g/L, (NH ₄ ) ₂ S ₂ O ₃ 155g/L, (NH ₄ ) ₂ SO ₄ 47g/L, take 1 liter of the waste liquid, add 60g of activated carbon to a beaker, heat to 70°C and keep stirring for 1 hour, filter; add 60mL of 98% concentrated sulfuric acid to the filtrate in a closed container until pH=3.5, heat to 80 ℃ and keep stirring for 1 hour, the escaped SO ₂ gas is drawn out with a catheter and absorbed with dilute ammonia water; after the reaction is completed, filter, add NaOH 96g and Ca(OH) ₂ 110g to the filtrate in a closed container, heat to 70 ℃ and keep stirring for 1 hour , the escaping ammonia is drawn out with a conduit and absorbed into dilute ammonia water; after the reaction is finished, filter, and the filtrate is evaporated and crystallized to obtain 178g of sodium thiocyanate product, with a purity of 97%.

Example 2

Take the coking desulfurization waste liquid provided by Huahao Coking Co., Ltd. in Changyi City, Shandong Province. After analysis, the main components of the waste liquid are: NH ₄ SCN 136g/L, (NH ₄ ) ₂ S ₂ O ₃ 107g/L, (NH ₄ ) ₂ SO ₄ 31g/L, take 1 liter of the waste liquid, add 20g of activated carbon to a beaker, heat to 90°C and keep stirring for 2 hours, filter; add 55mL of 70% concentrated sulfuric acid to the filtrate in a closed container until pH = 4.5, heat 60°C and keep stirring for 2 hours, the escaped SO ₂ gas is drawn out with a catheter and absorbed with dilute ammonia water; after the reaction is completed, filter, add 72g of NaOH and 75g of Ca(OH) ₂ to the filtrate in a closed container, heat to 50°C and keep stirring After 1 hour, the released ammonia gas was drawn out with a catheter and absorbed into dilute ammonia water; after the reaction was completed, it was filtered, and the filtrate was evaporated and crystallized to obtain 129 g of sodium thiocyanate product, with a purity of 96%.

Claims (1)

1. The method for extracting sodium thiocyanate from coking desulfurization waste liquid, the steps are as follows: add 2-6wt% activated carbon to coking desulfurization waste liquid, heat to 70-90°C and keep stirring for 1-2 hours, filter, and the filtrate is in a closed container Add sulfuric acid to pH = 3.5-4.5, heat to 60-80°C and keep stirring for 1-2 hours, the escaped sulfur dioxide gas is drawn out with a catheter and absorbed with dilute ammonia water, filtered after the reaction is completed, and the filtrate is added to the filtrate in a closed container Sodium hydroxide of the amount of substances such as ammonium thiocyanate and calcium hydroxide of the amount of substances such as ammonium sulfate in the filtrate are heated to 50-70 ° C and kept stirring for 1-2 hours, and the released ammonia gas is drawn out with a catheter and Absorbed with water to form dilute ammonia water, filtered after the reaction, and the filtrate was evaporated and crystallized to obtain sodium thiocyanate product.