How to Produce SOP Fertilizer: Common Mistakes and How to Avoid Them

Producing Sulfate of Potash (SOP) fertilizer can be highly profitable, especially as global agriculture shifts toward chloride-free potassium sources for fruits, vegetables, and high-value crops. However, SOP—particularly when manufactured through the Mannheim process—requires precise control at every stage. Many production issues do not come from poor equipment, but from small operational mistakes that quietly undermine purity, output, granule quality, and environmental compliance. Understanding these mistakes—and knowing how to prevent them—is essential for maintaining a stable, efficient, and safe SOP production line.

Unstable Raw Material Feeding

The Mannheim reaction depends on a precise feed ratio between potassium chloride and sulfuric acid. Even slight fluctuations cause a chain reaction of problems: incomplete conversion, excessive residue inside the furnace, unstable molten flow, and increased hydrogen chloride release. When feeding surges or becomes inconsistent, operators often notice temperature swings inside the furnace, which eventually lead to clinker formation or uneven SOP purity. Plants that rely heavily on manual feeding experience these issues most frequently because human adjustments cannot maintain the tight consistency the process requires.

How to Avoid It

Stable feeding begins with consistent particle size and moisture content in potassium chloride and a smooth, uninterrupted acid supply. Automated metering ensures that both materials enter the furnace at predictable rates, creating a balanced reaction environment. Maintaining uniformity in raw materials prevents sudden density changes that disrupt the thermal pattern in the furnace. When the feed remains steady, the chemical reaction becomes more predictable, molten discharge flows uniformly, and SOP purity stabilizes without the operator having to constantly correct the system.

Incorrect Furnace Temperature Control

The heart of SOP production lies in maintaining the correct temperature profile inside the Mannheim furnace. If the furnace runs too cool, the reaction slows, leaving unreacted materials and lowering overall conversion. If it runs too hot, the molten mass becomes overly aggressive, sticking to the furnace wall and forming hardened deposits that interfere with heat transfer. Many operators unintentionally cause temperature instability by adjusting heating based on short-term observations rather than the long-term behavior of the material bed. Overheated furnaces also create harsher operating conditions, shortening the lifespan of refractories and mechanical components.

How to Avoid It

Achieving consistent temperature control requires proper calibration of sensors and a firm understanding of how feeding rate affects heat demand. A stable temperature is maintained not by increasing heat output, but by keeping the reaction environment predictable—steady feeding, balanced airflow, and a well-maintained refractory surface. Operators should rely on gradual adjustments and avoid fast corrections that shock the system. When the thermal profile remains even, the reaction proceeds smoothly, clinker formation decreases, and the furnace operates within its intended efficiency range.

Insufficient Cooling After Furnace Discharge

Freshly reacted SOP exits the furnace at high temperature and remains physically unstable until properly cooled. When cooling is rushed or overlooked, residual heat continues to move through the granules or powder, causing them to cake, harden, or absorb moisture during downstream processing. Warm material also disrupts crushing and granulation by softening particle surfaces, leading to weak granules that break easily. Facilities that bypass adequate cooling often find that later production steps become inconsistent, even if the reaction stage was perfectly controlled.

How to Avoid It

Effective cooling requires allowing the discharged SOP sufficient residence time in a controlled cooling environment, typically through a LANE rotary or fluid-cooling system. Proper airflow removes heat gradually, stabilizing the physical structure of the product and preparing it for crushing or granulation. Cooling should continue until the material reaches a temperature safe for handling and storage. When the cooling stage is treated as a controlled process rather than a quick transition, granulation strength improves, product flowability increases, and long-term storage stability becomes far more reliable.

Inconsistent Crushing and Granule Conditioning

SOP that has been cooled still varies in size and must be conditioned before entering any granulation step. Oversized chunks, uneven powder, or residual fused material disrupts roller pressure distribution inside the granulator. When the feed lacks uniformity, some particles compress properly while others remain soft or fractured. This leads to granules that crumble during storage or transport, reducing the commercial quality of the product. Many plants overlook the importance of this stage, assuming that the granulator can compensate for inconsistent feed conditions.

How to Avoid It

Reliable granulation depends on a consistent feed texture. Proper crushing breaks down oversized fractions without generating excessive fines, while controlled screening ensures that only appropriately sized material advances to granulation. When the feed entering the granulator is uniform, pressure distributes evenly across the roller surfaces, producing stronger, more resilient SOP granules. This single improvement—consistent conditioning—often solves multiple downstream issues simultaneously.

Weak Granulation Stability

Even with well-conditioned feed, granulation can still fail if particle pressure, moisture balance, or roller surface condition is unstable. Operators sometimes increase roller pressure to correct weak granules, only to create excessive fines or uneven compaction. Moisture fluctuations also cause granules to crack as they dry, especially when ambient humidity varies. In many plants, granulation problems appear without immediate symptoms; only after storage or bagging do operators realize that the granules are fragile or inconsistent.

How to Avoid It

Granulation stability is achieved when feed moisture, roller pressure, and machine load stay within a consistent operating window. Continuous monitoring of granule strength during production allows operators to detect early signs of weakness and make gentle, progressive adjustments. Maintaining the rollers’ surface condition and ensuring balanced material distribution prevents localized stress points that weaken the product. With a stable granulation environment, SOP granules maintain uniform size and hardness from production all the way to the customer’s warehouse.

Poor Gas Absorption and Environmental Control

The Mannheim reaction releases hydrogen chloride gas, which must be captured and neutralized through an absorption system. When scrubbing towers are undersized, poorly maintained, or operated with imbalanced circulation, gas escapes or corrosive liquid floods parts of the system. Over time, this results in environmental non-compliance, corrosion of pipelines, and unsafe workplace conditions. Plants that treat scrubbing as a low-maintenance component often face unexpected downtime or regulatory issues.

How to Avoid It

A well-functioning gas absorption system relies on a stable chemical environment inside the scrubbing tower. The circulation solution must remain within its optimum pH range, allowing it to consistently neutralize incoming gas without losing efficiency. Components exposed to acidic vapor should be inspected and replaced before corrosion compromises their integrity. Continuous monitoring of exhaust concentration ensures that operators can detect system changes early and respond before emissions rise. When scrubbing is managed as an active process rather than a passive one, environmental compliance becomes easier, safer, and more reliable.

Lack of Real-Time Quality Monitoring

Some SOP plants rely solely on testing the final product to determine whether the batch is acceptable. By the time issues are detected—low potassium content, high impurities, weak granules, inconsistent size—the entire batch has already been produced, leaving no opportunity to correct the problem. Quality deviations often begin early: slight temperature changes in the furnace, minor feeding inconsistencies, or unnoticed variations in granulation moisture accumulate until the final output falls out of specification.

How to Avoid It

Real-time monitoring allows operators to identify problems at the moment they develop. Tracking furnace temperature patterns, reaction stability, moisture levels in granulation, and physical strength of partially formed granules provides continuous insight into the production health. Small corrections made early prevent larger deviations later, reducing waste and ensuring consistent market quality. Plants that integrate automated monitoring systems experience fewer line stoppages and far more predictable product results.

Conclusion

Producing SOP fertilizer requires a carefully managed workflow where small details have significant impact. The most common production issues—unstable feeding, temperature fluctuations, inadequate cooling, granulation instability, insufficient scrubbing, and weak quality monitoring—rarely appear suddenly. They develop gradually when the production line lacks controlled, synchronized operation.

By treating each stage as a connected system and maintaining consistency across feeding, reaction, cooling, granulation, and environmental management, producers achieve higher purity, improved stability, and a more competitive final product. Preventing mistakes, rather than correcting them afterward, is the foundation of a successful SOP manufacturing operation.

For more details, please feel free to contact us.

Henan Lane Heavy Industry Machinery Technology Co., Ltd.

Email: sales@lanesvc.com

Contact number: +86 13526470520

Whatsapp: +86 13526470520