Production method for preparing potassium humate fertilizer from potassium feldspar through continuous high-pressure hydrothermal method

A production method for preparing a potassium humate fertilizer through continuous high-pressure hydrothermal reaction of potassium feldspar, the production method comprises the following steps:

• (1) a wet grinding slurrying process:
• initially adding a KOH solution and crushed potassium feldspar according to a weight ratio of (1.5-5):1 into a wet mill and subjecting to a fine grinding to obtain an alkaline ore slurry, the KOH solution has a concentration within the range of 25 wt %-45 wt %, and the slurrying temperature is lower than 80° C.;
• (2) a hydrothermal reaction process:
• pressurizing the alkaline ore slurry obtained from step (1) by a high pressure pump and feeding into an electromagnetic heating tubular reactor to carry out a hydrothermal reaction, wherein the flow rate in tube is within the range of 1-5 m/s, the reaction temperature is within the range of 200-350° C., the pressure is the saturation pressure at the reaction temperature, the reaction time is within the range of 1-900 seconds;
• then feeding the alkaline ore slurry into a tower-type delayed reactor to extend the reaction time by 30-240 minutes and further enhance the hydrothermal reaction, a hydrothermal reaction slurry with an extraction rate of potassium within the range of 95%-99.9% is obtained from the tower-type delayed reactor bottom;
• (3) a flash evaporation filter pressing process:
• introducing the hydrothermal reaction slurry into a flash tower to carry out a flash separation, wherein a pressure of the flash tower top is from atmospheric pressure to 30 KPa, the high temperature steam obtained from the tower top preheats air to provide a cooling water, diluting the slurry at the tower bottom with the cooling water and subjecting the slurry to a filter pressing to obtain an alkaline potassium aluminosilicate filter residue and a potassium silicate filtrate;
• (4) a humic acid modified potassium fertilizer preparation process:
• mixing the alkaline potassium aluminosilicate filter residue with a humic acid according to a weight ratio of 1:
• (0.1-0.3), then modifying and granulating the mixture to produce a neutral long-acting slow-release potassium fertilizer, subsequently heating and drying the long-acting slow-release potassium fertilizer with hot air to obtain a humic acid coated long-acting slow-release potassium fertilizer product;
• alternatively, reacting the alkaline potassium aluminosilicate filter residue with a biologic fulvic acid to generate a water-soluble potassium fulvate;
• (5) a causticization and humic acid modified silicon-calcium fertilizer preparation process:
• blending the alkaline potassium silicate filtrate with lime according to a potassium and calcium molar ratio of 2:
• (1-1.2) to carry out a causticization reaction, returning the obtained KOH solution to the wet grinding slurrying process for recycling;
• mixing the obtained alkaline calcium silicate with a humic acid according to a weight ratio of 1:
• (0.1-0.3), modifying and granulating the mixture to produce a neutral long-lasting slow-release silicon-calcium fertilizer, subsequently heating and drying the long-lasting slow-release silicon-calcium fertilizer with hot air to prepare a humic acid coated long-acting slow-release silicon-calcium fertilizer product.