The production of blended fertilizers is mainly based on "physical mixing" and does not require chemical synthesis. The process can be divided into "raw material pretreatment → precise batching → mixing and stirring → anti caking treatment → finished product packaging → quality inspection", as follows:

Step 1: Raw material pretreatment (ensuring uniform physical properties)

Screening: Use a vibrating screen (with a mesh size of 2-4mm) to screen all raw materials, remove powder, clumps, or impurities (such as stones and debris), ensure that the particle size of the raw materials is consistent (error ≤ 0.5mm), and avoid layering after mixing;

Drying: If the raw materials absorb moisture (such as urea, potassium chloride), they need to be dried with a hot air dryer (temperature 50-60 ℃) to reduce the moisture content to ≤ 2% to prevent subsequent clumping;

Crushing (optional): If some of the raw material particles are too large (such as ammonium phosphate clumps), use a hammer crusher to crush them to 2-4mm before entering the screening stage.

Step 2: Precise ingredients (core: measured according to the formula)

Ingredients are the key to determining the accuracy of nutrient content in mixed fertilizers, and precise measurement needs to be achieved through an "automated ingredient system" to avoid manual ingredient errors.

Equipment composition: raw material warehouse (divided by raw material type, such as urea warehouse, ammonium phosphate warehouse, potassium fertilizer warehouse), screw conveyor (controlling raw material conveying speed), electronic belt scale (real-time weighing, accuracy ± 0.5%);

Operation process:

Set the "weight ratio" of each raw material according to the formula (such as 30% urea, 25% diammonium phosphate, 40% potassium chloride, and 5% medium and trace fertilizer);

Start the conveyor to transport each raw material to the electronic belt scale at the set speed, provide real-time feedback on weight deviation, and automatically adjust the conveying speed;

The measured raw materials enter the mixer through a chute to avoid premature separation due to particle differences during transportation.

Step 3: Mixing and stirring (key: achieving uniformity)

The goal of mixing is to achieve "uniform distribution" of each raw material particle in the finished product, usually requiring a coefficient of variation of mixing uniformity ≤ 5% (i.e. nutrient content error at any sampling point ≤ 5%).

Common equipment: Double helix mixer (suitable for granular raw materials, mixing time 3-5 minutes), non gravity mixer (high mixing efficiency, suitable for raw materials containing a small amount of powder, time 2-3 minutes);

Operation points:

Control the "loading amount": The loading volume of the mixer should not exceed 70% of the total volume, otherwise insufficient mixing may lead to "dead corners";

Setting the "mixing time": If the mixing is too short and uneven, or too long, it can cause particle wear (resulting in powder production and increased separation risk). It needs to be adjusted according to the characteristics of the raw materials (such as 3 minutes for pure particle raw materials and 4 minutes for medium and micro fertilizers);

Avoid "adding small ingredients first": Trace elements (such as chelated zinc and boron fertilizer) need to be pre mixed with a small amount of main raw materials (such as urea) to make a "mother material", and then added to the mixer to prevent small particles from gathering in corners.

Step 4: Anti caking and anti separation treatment (ensuring storage and application)

Blended fertilizers are prone to layering during storage or transportation due to subtle differences in particle density and size; And some raw materials are prone to clumping after absorbing moisture, which needs to be solved through "anti caking agent addition" and "particle optimization".

Addition of anti caking agent:

Method: set a "spray device" at the outlet of the mixer to evenly spray liquid anti caking agent (such as mineral oil+silica) on the surface of the mixed particles, or add powdered anti caking agent (such as talcum powder) during the mixing process;

Dosage: Liquid anti caking agent 0.3% -0.5%, powder 0.5% -1%, excessive amount will affect the solubility of fertilizer (especially for drip irrigation);

Anti separation treatment:

If there is a significant difference in the density of the raw materials (such as a density of 1.6g/cm ³ for diammonium phosphate and 1.9g/cm ³ for potassium chloride), "slight granulation" (such as extrusion granulation, which compresses small particles into larger "composite particles") can be performed after mixing to reduce delamination;

Before packaging the finished product, it is slowly conveyed through a "vibrating chute" to avoid particle separation by size due to excessive drop.

Step 5: Finished product packaging and storage

Packaging requirements:

Packaged in woven bags lined with polyethylene film (waterproof, moisture-proof), each bag weighs 25kg or 50kg, with an error of ≤± 0.2kg;

The packaging bag should be labeled with "nutrient content (N-P ₂ O ₅ - K ₂ O), raw material composition, production date, shelf life, and application method" to avoid confusion with other fertilizers;

Storage conditions:

Store in a ventilated and dry warehouse, with moisture-proof boards laid on the ground (≥ 10cm above the ground) to avoid direct contact with damp floors;

The stacking height should not exceed 10 layers to prevent the bottom layer fertilizer from clumping due to compression;

Separate the storage of mixed fertilizers with different formulas to avoid cross contamination.

Step 6: Quality inspection (to ensure compliance)

Each batch of finished products needs to be sampled and tested, with the following key indicators:

Nutrient content: The actual content of N, P ₂ O ₅, K ₂ O and trace elements shall be detected through chemical analysis, and the error shall comply with the national standard (GB/T 21633-2020 "Blended Fertilizer (BB Fertilizer)");

Mixing uniformity: Randomly select 10 samples, test the content of the same nutrient (such as nitrogen), and calculate the coefficient of variation (≤ 5% is qualified);

Moisture content: Use drying method to detect moisture content ≤ 2.5% to prevent clumping during storage;

Particle integrity: The proportion of particles with a screening detection of ≥ 2mm is ≥ 90% to avoid separation caused by excessive powder.

Production steps of mixed fertilizer Mixing fertilizer equipment