The normal operation of the rice mill

The normal operation of a rice mill is a systematic process from raw material pretreatment to finished product output, centered around the four goals of "removing rice impurities, peeling off husks, grinding rice bran, and improving rice quality". It can be broken down into five modules: raw material preparation, equipment startup inspection, core processing links, finished product processing, and equipment shutdown maintenance. The operations and requirements for each link are as follows:

1、 Early stage: Raw material preparation and equipment inspection

This is the foundation for ensuring stable operation and avoiding malfunctions of the rice mill, and special attention should be paid to "meeting raw material standards" and "equipment without hidden dangers".

Raw material pretreatment (rice preparation)

Removing impurities: By using auxiliary equipment such as screening (cleaning screen) and air selection (fan), impurities such as stones, soil, weeds, and broken straw in the rice are removed (impurity content should be ≤ 0.5%), avoiding impurities from wearing down the rice mill rollers, blocking the equipment, or affecting the purity of the finished rice. Control moisture content: The moisture content of rice should be controlled between 13% and 15% (too high can cause rice bran adhesion and uneven whitening, while too low can cause an increase in broken rice rate). If the moisture content does not meet the standard, it needs to be adjusted by drying or air drying in advance.

Check before starting the equipment

Mechanical components: Check whether the rice milling roller (sand roller/iron roller) is worn or loose, whether the rice sieve (screen mesh) is damaged or blocked, whether the tightness of the transmission belt (chain) is appropriate, and whether the connecting bolts are firm. Electrical system: Confirm that the power supply voltage is stable (in accordance with the rated voltage of the equipment, such as 380V industrial electricity), there is no leakage or aging phenomenon in the motor, switch, and circuit, and the emergency stop button function is normal. Lubrication and Cleaning: Check whether the lubricating oil of rotating parts such as bearings is sufficient and free from deterioration, and whether there is any residual rice bran or broken rice accumulation inside the equipment (such as the whitening chamber and rice bran collection channel).

2、 Mid term: Core Processing Flow (Continuous Automated Operation)

The rice mill achieves the conversion from rice to white rice through "multi link collaboration". Different types of rice mills (such as rice hulling and milling combination machines, single machine rice mills) have slightly different processes, but the core links are the same. Taking the common integrated rice hulling and milling equipment as an example:

Husking process

Principle: After the rice enters the hulling chamber, it is separated from the brown rice by a pair of rotating rubber rollers (or sand rollers) that generate squeezing and rubbing forces. Key requirement: The pressure of the rubber roller needs to be adjusted according to the variety of rice (such as indica rice and japonica rice) (excessive pressure will crush brown rice, while insufficient pressure will result in low shelling rate), and the shelling rate should be ≥ 95%. At the same time, the lightweight husks should be sucked into the collection bag through the air selection device, and the brown rice should enter the next stage.

Grain roughness separation process

Principle: After husking, there are still "hulled rice" mixed in the material. The hulled rice is screened out through a separation screen (using the difference in particle size and specific gravity between rice and brown rice), and then sent back to the husking chamber for secondary husking. Pure brown rice then enters the whitening process. Key requirement: The separation efficiency must be ≥ 98% to avoid untreated rice entering the whitening chamber and causing finished rice to contain grains.

Whitening (rice bran removal) process

Principle: Brown rice enters the whitening chamber and is ground by a high-speed rotating rice mill roller (sand roller grinds to remove bran, iron roller rubs to remove bran) to remove rice bran (brown rice skin layer). At the same time, the rice bran is filtered out by a rice sieve, and the white rice is pushed towards the outlet in the whitening chamber. Key requirements: Adjust the air pressure, roller speed, and outlet pressure valve tightness of the milling chamber according to the customer's demand for "rice quality accuracy" (such as refined white rice and standard white rice) - the higher the accuracy, the greater the milling strength (but the broken rice rate should be controlled to be ≤ 3%~5%). Rice bran collection should be timely to avoid blockage and affect the milling effect.

White rice sorting process

Principle: Crushed rice and rice bran powder may be mixed in the white rice after grinding. Fine processing is carried out through a white rice sieve (separating crushed rice from whole rice), a polishing machine (optional, improving the glossiness of white rice through water mist and friction), and a color sorting machine (optional, removing discolored grains such as yellow rice and diseased rice). Key requirements: The whole meter rate must meet the standard (such as ≥ 90%), the impurity content of finished rice should be ≤ 0.1%, and the glossiness should be uniform (after polishing).

3、 Post production: Collection of finished products and maintenance of equipment

Finished product output and storage

The sorted white rice is sent to the finished product warehouse through a conveyor belt or directly bagged (pay attention to the cleanliness and moisture resistance of the packaging bags). The storage environment should be dry, ventilated, and insect proof (temperature ≤ 25 ℃, relative humidity ≤ 70%) to avoid moisture absorption and mold growth of the finished rice. Synchronize the collection of by-products such as rice bran and rice husk (rice bran can be used for feed processing, rice husk can be used as fuel or organic fertilizer), ensuring that the by-product collection channel is unobstructed.

Equipment shutdown and maintenance

Cleaning: Thoroughly clean the residual materials in the whitening chamber, rice sieve, and rice bran collection channel to avoid rice bran mold and odor, which may contaminate the rice grains for the next processing. Inspection and replacement: Check the wear of the rice mill roller and rubber roller (replace the sand roller after grinding it flat, repair or replace the rubber roller if it has cracks or dents), clean the motor heat dissipation hole, and replenish the bearing lubricating oil. Record: Record the startup time, processing volume, and equipment operating status (such as current and abnormal noise) for troubleshooting and developing maintenance plans. Shutdown process: First, close the raw material feeding valve, wait for the residual materials in the equipment to be completely discharged (no materials in the whitening chamber and conveyor belt), then turn off the motor power supply, and finally cut off the main power supply. 

4、 Core judgment criteria for normal work

Whether the rice mill is running normally can be visually judged by the following indicators:

Processing quality meets the standard: the broken rice rate of finished rice is ≤ 5%, the grain content is ≤ 0.1%, the impurity content is ≤ 0.1%, the rice quality is uniform, and the glossiness meets the requirements (without "over grinding" or "under grinding"). Stable operation of the equipment: The motor operates without any abnormal noise (such as buzzing or friction), the current is within the rated range (without overload), there is no severe vibration of any components, and the collection of rice bran and rice husks is unobstructed (without blockage). No safety hazards: The equipment casing has no electrical leakage, the emergency stop button responds promptly, the operator wears protective equipment (such as dust masks and gloves) according to regulations, and there is no material leakage (such as rice bran overflow).