Potassium salt, in a narrow sense, refers toPotassium chloride, chemical formula KCl,(also known as potassium rock salt)，Colorless cubic crystal, often in the shape of long columns. Colorless elongated diamond shaped or cubic crystal, or white crystalline small particle powder, density 1.984g/cm）Broadly speaking, it includes all potassium containing salts, such as potassium magnesium aluminate (KC1 · MgSO4 · 3H20), carnallite (KC1 · MgC12 · 6H20), and polyhalite (K2SO4 · MgSO4 · 2CaSO4 · 2H20). 95% of global potassium salt products are used foragricultureThe main function of potassium fertilizer on crops is to balance nitrogen, phosphorus, and other nutrients, promote the formation of plant proteins and carbohydrates, regulate plant functional functions to develop roots, strengthen branches, and improve drought and cold resistance; Improve crop quality and increase crop yield. It is very important to apply nitrogen, phosphorus, and potassium fertilizers in proportion based on soil, climate conditions, and crop types to increase the yield per unit area of crops. In agricultural production, the effective component content in fertilizers is usually calculated based on N: P205: K20. The current ratio of fertilization on arable land in the world is approximately 1:0.42:0.42, In 2003, the proportion of total fertilizer production in China was 1:0.19:0.13.

China is a major agricultural country. With the development of agricultural technology innovation and industrial restructuring, agricultural development has made significant progress, and the demand and dependence on potassium fertilizer have gradually increased. From the analysis of China's potassium resources, the confirmed amount of soluble potassium resources in 2013 was 1.005 billion tons. The distribution of potassium mineral resources continues to be extremely uneven, with about 95% of potassium salt resources distributed in the western Qaidam Basin in Qinghai and the northern depression of Lop Nur in Xinjiang. According to the industry development trend, the annual production capacity of potassium fertilizer in China will reach 12 million tons of physical quantity in 2016, and the annual output will be maintained at 7-10 million tons of physical quantity based on market conditions. Among them, potassium chloride production is mainly concentrated in the Qaidam Basin of Qinghai Province. According to industry experts, there are currently 32 potassium chloride production enterprises in China. In 2015, the production capacity of potassium chloride increased by 1.34 million tons year-on-year, with the main growth point in Qinghai Salt Lake; The production increased by 9.6% year-on-year, reaching a historical high of 7.426 million tons. Among the scattered salt lakes in the Chaidamu Basin of Qinghai, the Cha'erhan Salt Lake has unique and advantageous conditions for resource development. Its production capacity can meet 2/3 of the domestic demand, providing a guarantee for the smooth development of the entire fertilizer production and operation. The self-sufficiency rate of potassium fertilizer in China has reached 68%, with domestic potassium fertilizer supporting half of the country.

The consumption of potassium fertilizer in China is primarily as a raw material for compound fertilizers; The second is to directly fertilize the farmland. According to the statistical analysis of the yield of compound fertilizers in China, it is estimated that there are approximately40%Potassium fertilizer enters the compound fertilizer, while the rest60%Still applied directly as a single fertilizer.

Extrusion granulation has the following process characteristics:

The process of powder agglomeration into dense and hard plates under pressure is called extrusion; The process of crushing and sieving the plates into granular materials is called granulation. The function of squeezing is to expel the air between particles, and to bring the distance between particles close enough to generate attractive forces such as van der Waals forces, adsorption forces, crystal bridges, and embedded connections. The strength of extruded granules is mainly formed by the intermolecular forces between molecules.

The dry rolling granulation process has the following characteristics:

1. Low energy consumption: Roll granulation is the process of granulating materials at room temperature, which eliminates the need for other granulation methodsDrying measures such as fuel and gas are required. Production only requires electricity consumption, with each ton of product consuming only about 30kWh of electricity.

2. No need to add adhesive: Other granulation processes are mostly wet processes that require a drying process, resulting in high energy consumption and high product moisture content. Dry granulation does not require additional additives and only utilizes the intermolecular forces of the material itself, simplifying the process and reducing energy consumption.

3. Low investment: Due to the elimination of the drying process and the simple process flow, the investment is relatively low. The system mainly consists of four parts: (1) powder pretreatment; (2) Roll pressing; (3) Consolidation and fragmentation; (4) Processing after granulation.

4. Wide capability range: For roll granulation equipment, the capacity ranges from 1 ton/hour Up to 50 tons per hour Taiwan can carry out more economical designs, so it has a wide range of applicable capabilities.

5. The shape of roll granulation is irregular particles, which does not affect the application of fertilizers. If necessary, a trimming process can be added to further round the particles. Fertilizer produced by extrusion granulation has sufficient strength, less dust, no clumping, narrow particle size distribution range, and good flowability.

technological process:

Roll granulation processIt consists of four parts, described as follows:

1．Pre processing of raw materials:Storage, measurement, and mixing

producefrontTrace elements can also be added to the mixer. In order to ensure uniform particle distribution of trace elements, high-strength mixers are selected. The mixed material and return material are lifted by a bucket elevator and mixed with the return material in a dual axis paddle mixer. The return material is the unqualified particles after crushing and screening, and the ratio of circulating material to new material is about 35:65.

2Rollerpress

mixtureThe material is fed into the gap between two rollers rotating in opposite directions through a vertical spiral feederDuring the compression process, the pressure on the material gradually increases. When the gap between the two shafts is at its minimum position, the material is subjected to the maximum pressure, and then gradually decreases until it reaches zero. During the extrusion process, due to the reduction in material volume, the apparent density of the mixture can increase by 1.5-3 times.rollerThe compressed product is a thick piece of 5-20mmofsectorThe structure and size of the roller press are determined by many parameters, which are generally determined based on material properties and experiments.

There are certain requirements for the particle size, shape, moisture content, plasticity, hardness, temperature, etc. of the applicable raw materials. The materials entering the biting zone need to have good flowability, which requires a low moisture content of the materials because the flowability decreases when the moisture content of the materials reaches a certain level.

The extrusion process of materials includes: a. rearrangement of materials; b、 Fragmentation; c、 There are three stages of plastic deformation. These stages may not necessarily be sequential, they may occur intermittently. The result of extrusion is that the compression ratio of general materials is close to 2.5:1, or the removal rate of gas in the feeding is over 60%. In order to achieve better extrusion effect, the feed particle size should be of different sizes, with a suitable range between 0.1 and 1.0. Materials that are too fine (less than)1.0mm）There is too much gas content, and materials that are too large require more energy consumption.

The hardness or plasticity of the material affects the pressure required for the extrusion process. Some materials, such as potassium chloride, diammonium phosphate, and urea, have good plasticity and can be extruded into granules effectively; And potassium sulfate, ammonium sulfate, magnesium sulfate, phosphorusThe plasticity of mineral powder is poor, the extrusion effect is poor, and it is not easy to extrude. For ingredients that are not easy to extrude, in order to achieve better results, an appropriate amount of binder can be added. Urea, potassium chloride, and a small amount of water can act as binders.

3. Granulation and screening

The plates need to be further broken and graded to obtain the required particle size. There is one under the roller press machinebiaxPlate crusher, pre crushing of platesA small piece of about 50mm.Small pieceRelatively easy to transport and susceptible to subsequent damageGranulatorsFurther fragmentation. The crushed raw materials are divided into large particles, product particles, and small particles on the grading screen. The fine particles on the lowest sieve are recycled back to the mixer and then extruded into shape. The oversized particles that are trapped in the upper layer of the multi-stage sieve need to be further crushed. After crushing, return to screening.

Choosing the right crushing and screening equipment is crucial forRoll granulation processThe economy is crucial. The shape of the particles (usually cubic) and the size range of the particles (1)-5 millimetersOr 2-4 millimeters）The amount of circulation after crushing and screening determines the output and capacity of a set of equipment.

4．Post processing of finished products:Polishing and repairing

Under normal circumstances, the final product needs to be polished and trimmed. Irregular shaped particles are rounded at edges and corners using a grinding drum. The fine powder generated during the polishing process is sieved through a layer of sieve and circulated. When repairing, anti caking agents are usually added.

For environmental protection purposes, the entire device needs to be equipped with a bag filter for dust collection.