The dilemma of bio organic fertilizer granules: easy to form, difficult to round, and quality upgrade encounters bottlenecks

Bio organic fertilizers, rich in active bacteria such as Bacillus subtilis and Bacillus licheniformis, as well as organic matter, can improve soil and enhance crop stress resistance, making them a core fertilizer category in green agriculture. The annual production of bio organic fertilizers in China has exceeded 30 million tons, with granular products accounting for over 60%. Due to its advantages such as easy transportation, uniform fertilization, and stable fertilizer efficiency, it is highly favored by large-scale growers.

However, the production of bio organic fertilizer granules faces the core challenge of "upgrading the quality after molding": the initial granules produced by the granulator often have sharp edges, rough surfaces, and insufficient strength, resulting in a damage rate of over 15% during transportation, and a 20% increase in the inactivation rate of active bacteria due to particle damage and contact with air; At the same time, rough particles are prone to moisture absorption and agglomeration, resulting in poor product appearance and a price 10% -15% lower than round particles. As a key equipment for post-treatment in the production of bio organic fertilizers, the round throwing machine can address these pain points and achieve a leapfrog improvement in particle quality through "physical shaping+surface optimization". Its special role is irreplaceable. This article deeply analyzes the core value and application logic of the round throwing machine in the production of bio organic fertilizers.

Core function one: Physical shaping to enhance the properties and storage resistance of granular products

The commodity value of bio organic fertilizers is directly linked to the appearance and strength of the particles. Through the unique principle of "centrifugal friction+collision shaping", the throwing machine optimizes the physical properties of the particles from three dimensions, laying the foundation for product quality:

（1） Round particles shape, enhancing both appearance and premium

The initial granules produced by granulators (such as rotary drum granulators and double roll extrusion granulators) have an angular ratio of over 40% and a surface roughness Ra of over 1.2 μ m. The circular polishing machine drives particles to undergo centrifugal motion through a high-speed rotating cylinder (with a speed of 300-500r/min). The particles rub and collide with each other on the inner wall of the cylinder and the plate, and the edges and corners are polished and rounded, making the surface smooth. After rounding treatment, the particle roundness can be increased from 60% -70% to 85% -95%, the surface roughness can be reduced to below 0.4 μ m, and the appearance is uniform spherical.

Market data shows that bio organic fertilizer particles with a roundness of ≥ 90% have a terminal selling price 0.2-0.5 yuan/kg higher than ordinary particles; In export trade, the pass rate of inspection for round particles exceeds 98%, while for ordinary particles it is only 82%. Round processing has become a "standard procedure" for the high-end development of bio organic fertilizers.

（2） Strengthen particle strength, reduce the risk of transportation damage and bacterial inactivation

Bio organic fertilizers contain a large amount of organic matter and active bacterial carriers. The internal structure of the initial particles is loose, and the compressive strength is only 5-10N. During transportation, the damage rate is high due to bumps and collisions. During the shaping process, the throwing machine will further compact the material inside the particles, reduce the porosity by 15% -20%, increase the compressive strength to 15-25N, and control the transportation damage rate within 5%.

More importantly, the decrease in particle breakage rate directly reduces the contact area between active bacteria and air, avoiding the inactivation of microbial agents due to oxidation. The experiment of a certain bio organic fertilizer factory in Shandong showed that the retention rate of active bacteria in particles treated with round throwing after storage for 3 months reached 85%, while the retention rate of non round particles was only 62%, effectively ensuring the core fertilizer efficiency of bio organic fertilizer.

（3） Reduce moisture absorption and clumping, extend product shelf life

The organic matter and active bacterial carriers in bio organic fertilizers have strong hygroscopicity. The rough particles, due to their large surface area and numerous surface pores, are prone to adsorb moisture from the air and clump together. The shelf life is usually only 6 months. The surface of the particles after rounding treatment is smooth, with a specific surface area reduction of 30% -40%. The surface pores are compacted, and the moisture absorption rate is reduced from 25% to below 8%. The agglomeration rate is controlled within 3%, and the shelf life can be extended to 12 months, significantly reducing inventory loss for enterprises.

Core function 2: Process adaptation to ensure the core fertilizer efficiency of bio organic fertilizers

The core advantage of bio organic fertilizer is the fertilizer efficiency of active bacteria. The round throwing machine not only does not damage the active bacteria, but also adapts to the special production process of bio organic fertilizer, enhancing the stability of fertilizer efficiency. Its process adaptation value is mainly reflected in two aspects:

（1） Low temperature plastic surgery to protect the survival of active bacteria

The active bacteria in bio organic fertilizers, such as nitrogen fixing bacteria and phosphorus solubilizing bacteria, are sensitive to temperature and have a deactivation rate of over 90% when they exceed 60 ℃. The round throwing machine adopts the "physical friction shaping" method, without high-temperature heating, and the temperature rise of particles during the shaping process does not exceed 5 ℃ (measured high temperature ≤ 45 ℃), which can maximize the retention of active bacterial activity. In contrast, some traditional plastic surgery equipment (such as high-temperature drying plastic surgery machines) can result in a deactivation rate of over 30% of active bacteria due to improper temperature control.

According to data from a bio organic fertilizer enterprise in Hebei Province, products processed using a round machine have a particle count of 250 million CFU per gram of active bacteria, far exceeding the 120 million CFU of products that have not been round, fully meeting the requirements of the "Bio Organic Fertilizer" (NY 884-2012) standard.

（2） Adapt to coating technology to achieve slow-release and precise supply of fertilizer efficiency

High end bio organic fertilizers often require coating processes (such as humic acid coating and slow-release agent coating) to achieve slow-release fertilizer efficiency, and the core prerequisite for coating effect is a smooth, rounded, and uniform particle surface. The particles processed by the polishing machine have high roundness and good surface flatness. The coating material can uniformly adhere to the surface of the particles, forming a coating layer with a consistent thickness (0.1-0.3mm), and the coating coverage rate is over 98%.

The release cycle of nitrogen, phosphorus, and potassium nutrients in the bio organic fertilizer treated with round throwing and coating has been extended from 30 days to 90 days, avoiding the problem of "burning seedlings in the early stage and fertilizer removal in the later stage". In the tomato planting experiment, this type of product extended the tomato harvest period by 15 days and increased the total yield by 18%, fully reflecting the adaptability value of the round throwing machine to high-end technology.

Core function three: Scene adaptation to meet the production needs of different scales

The production scale of bio organic fertilizers varies greatly (ranging from 10 tons to 500 tons per day), and the round throwing machine is designed with different models to adapt to the full scenario production from small workshops to large factories, ensuring the quality upgrade needs of enterprises of all sizes:

（1） Small scale production scenario (daily output of 10-50 tons): high-efficiency and energy-saving round throwing machine

Small scale bio organic fertilizer plants usually adopt the basic process of "granulation+simple screening", with a focus on "low cost and easy operation" for round throwing requirements. It is recommended to use a single cylinder circular polishing machine with a diameter of 1.2-1.5m, a power of 5.5-11kW, an hourly processing capacity of 1-3 tons, and an equipment investment of only 20000-50000 yuan. This type of machine has a simple structure and adopts a variable frequency speed regulation design. The speed can be adjusted according to the initial state of the particles, and it is suitable for different raw materials (such as straw based and bacterial residue based bio organic fertilizers) to meet the rounding requirements. The finished product roundness can reach over 85%.

（2） Medium scale production scenario (daily output of 50-200 tons): Continuous production type circular polishing machine

Medium sized enterprises need to achieve continuous production of "granulation polishing screening packaging". It is recommended to use a double tube series polishing machine with a diameter of 1.8-2.2m, a power of 15-22kW, and an hourly processing capacity of 5-10 tons. This model adopts a two-stage design of "initial polishing+precision polishing". The first stage is to remove the edges and corners of the cylinder, and the second stage is to optimize the surface smoothness, increasing the roundness to over 90%; Equipped with automatic feeding and discharging devices, it can seamlessly connect with granulators and screening machines, reducing manual intervention and increasing production efficiency by 40%.

（3） Large scale production scenario (daily output>200 tons): intelligent control type round throwing machine

Large scale bio organic fertilizer enterprises pursue "high quality and intelligence", and it is recommended to use intelligent round throwing machines with a diameter of 2.5-3.0m, a power of 30-45kW, and an hourly processing capacity of 15-25 tons. This model is equipped with a PLC control system, which can monitor parameters such as particle roundness and temperature in real time, automatically adjust the speed (300-500r/min infinitely adjustable) and feed speed; The inner wall of the cylinder is lined with wear-resistant rubber, with a service life of over 2 years, reducing equipment maintenance costs; At the same time, it can be integrated with the enterprise MES system to achieve full traceability of production data.

Practical Guide: Optimization and Application Techniques of Rounder in Bio organic Fertilizer Production

（1） Parameter matching: precise control based on the characteristics of raw materials

The initial particle characteristics of bio organic fertilizers from different raw materials are different, and the throwing parameters need to be adjusted accordingly: ① Bacterial residue based bio organic fertilizers: the initial particles are brittle, the speed is controlled at 300-350r/min, and the throwing time is 5-6 seconds to avoid excessive friction causing particle breakage; ② Fecal based bio organic fertilizer: The initial particles have high viscosity, and the rotation speed is adjusted to 450-500r/min. The rounding time is 8-10 seconds to ensure a smooth surface; ③ Straw based bio organic fertilizer: The initial particles are loose and can be sprayed with 0.5% -1% water (at room temperature) before rounding to enhance the shaping effect.

（2） Linkage regulation: Collaborative optimization with granulation process

The rounding effect is directly related to the quality of granulation, and process linkage needs to be achieved: ① The particle size at the outlet of the granulator should be controlled within 2-5mm, with a particle size deviation of ≤ 1mm, to avoid insufficient rounding of large particles and excessive wear of small particles; ② After granulation, the moisture content of the particles should be controlled at 18% -22%. If the moisture content is too high, it can easily lead to particle adhesion, while if it is too low, it will be difficult to shape. This can be adjusted by coordinating the humidification module of the granulator with the ventilation device of the throwing machine.

（3） Maintenance: Ensure stable operation and particle quality of equipment

Daily maintenance should focus on three points: ① Clean the residual materials on the inner wall of the cylinder daily to avoid material clumping and affecting the throwing effect; ② Check the wear of the lining plate weekly, and replace it promptly if the wear exceeds 3mm to prevent metal contamination; ③ Lubricate the transmission system monthly to ensure stable speed and avoid uneven particle roundness caused by speed fluctuations.

Guide to Avoiding Pits: 5 Misunderstandings in the Application of Rounders in Bio organic Fertilizer Production

Misconception 1: The higher the rotational speed, the better the roundness. Excessive rotational speed (over 500r/min) can lead to excessive particle wear, deactivation of active bacteria due to frictional heat generation, and a 30% increase in energy consumption. The rotational speed should be adapted according to the characteristics of the particles.

Misconception 2: The longer the rounding time, the smoother the surface, and the lower the toughness of the bio organic fertilizer particles. If the rounding time exceeds 12 seconds, it is easy to break, usually controlled within 5-10 seconds.

Misconception 3: Neglecting the influence of raw material moisture content on roundness. When the moisture content is below 15%, particles are prone to breakage, and above 25%, they are prone to adhesion. It is necessary to strictly control it within 18% -22%.

Misconception 4: Small factories do not need dedicated round polishing machines. Even if they produce in a small scale, the damage rate of unpolished particles is high and the selling price is low. The investment in introducing a simple round polishing machine can be recovered within 1-2 months.

Misconception 5: Packaging directly after rounding, omitting the screening and rounding process will produce a small amount of fine powder, which needs to be removed by screening (fine powder content ≤ 2%), otherwise it will affect the uniformity of the product.

The special role of the round throwing machine in the production of bio organic fertilizers is reflected in three core dimensions: "the shaper of quality upgrading, the guardian of fertilizer efficiency guarantee, and the connector of process adaptation". It not only enhances the commodity properties and storage resistance of particles through physical shaping, but also adapts to special process requirements such as protection of active bacteria and coating slow-release of bio organic fertilizers, while meeting the production adaptability of enterprises of different scales. With the continuous improvement of consumers requirements for the quality of bio organic fertilizers, the spinning machine has shifted from an "optional equipment" to a "mandatory equipment". For enterprises, scientifically selecting circular polishing machines and optimizing operating parameters can achieve a dual improvement in product quality and economic benefits, and build core advantages in the competition of green agriculture market.