| CPC C05C 9/005 (2013.01) [C05C 9/02 (2013.01); C05G 5/12 (2020.02)] | 12 Claims |
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1. A method for industrialized continuous and simplified preparation of a urea-formaldehyde slow-release nitrogen fertilizer by using a device for industrialized continuous and simplified preparation of a urea-formaldehyde slow-release nitrogen fertilizer, the device comprising:
a solid material storage tank;
a first metering belt being arranged below a discharge port of the solid material storage tank; a reaction kettle being arranged below the discharge end of the first metering belt; a feed port of the reaction kettle being connected to a first liquid material storage tank through a first pipeline and connected to a second liquid material storage tank through a second pipeline; a first metering pump being arranged on the first pipeline, and a second metering pump being arranged on the second pipeline; a discharge port of the reaction kettle being successively connected to an upper-stage reactive extruder, a lower-stage reactive extruder, a granulator, a dryer, a cooling machine, a sieving machine, and a packaging machine through a third pipeline; a third metering pump being arranged on the third pipeline between the reaction kettle and the upper-stage reactive extruder; a mechanical stirring device and a heating device being arranged inside the reaction kettle; and a control valve being provided at the discharge port of the reaction kettle; and the sieving machine being connected to a feeding assembly of the upper-stage reactive extruder through a fourth pipeline; and
the method comprising:
(S1) feeding urea from the solid material storage tank to the reaction kettle through the first metering belt; pumping formaldehyde from the first liquid material storage tank to the reaction kettle through the first metering pump, and pumping potassium hydroxide solution from the second liquid material storage tank to the reaction kettle through the second metering pump to form a reaction system with a preset pH value, followed by stirring to obtain a hydroxymethylurea solution;
(S2) opening the control valve arranged on the bottom of the reaction kettle; pumping the hydroxymethylurea solution obtained in step (S1) into the feeding assembly of the upper-stage reactive extruder through the third metering pump; and performing reactive extrusion in the upper-stage reactive extruder to allow hydroxymethylurea to undergo a self-polycondensation to produce urea-formaldehyde, so as to obtain a continuous urea-formaldehyde extrudate;
(S3) feeding the continuous urea-formaldehyde extrudate obtained in step (S2) to a feeding assembly of the lower-stage reactive extruder, followed by kneading and extrusion from a die of the lower-stage reactive extruder to obtain a continuous strip-shaped slow-release nitrogen fertilizer crude product;
(S4) cutting the continuous strip-shaped slow-release nitrogen fertilizer crude product obtained in step (S3) into cylindrical granules by using the granulator;
(S5) drying the cylindrical granules obtained in step (S4) by using the dryer to obtain dried cylindrical granules;
(S6) cooling the dried cylindrical granules obtained in step (S5) by using the cooling machine;
(S7) grading cooled cylindrical granules obtained in step (S6) by using the sieving machine, wherein qualified cylindrical granules are fed to the packaging machine, and unqualified cylindrical granules are returned to the feeding assembly of the upper-stage reactive extruder to undergo an extrusion and granulation process again; and
(S8) packing the qualified cylindrical granules obtained in step (S7) by using the packaging machine to obtain the urea-formaldehyde slow-release nitrogen fertilizer.
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