Why flour mill selection starts with the T/24h figure
Wheat mills are rated worldwide in tonnes per 24 hours (T/24h), not tonnes per hour, because a modern mill is designed for continuous operation. When a Chinese manufacturer offers you a "50-tonne mill", it means 50 tonnes of wheat milled over a full operating day — roughly 2.1 tonnes of wheat per hour. Confusing the two units is the single most common error at the quotation stage, and it leaves the buyer mentally sizing a plant twenty-four times larger than what will be delivered.
The second critical point: the advertised figure describes the wheat entering the milling system, not the flour leaving it. The gap between them is the extraction rate, and that is the variable that determines your actual revenue.
From market size to mill capacity: the practical calculation
Start from daily flour demand in your target market, then work backwards:
- Define the daily flour requirement in tonnes (example: 35 tonnes of flour).
- Divide it by your target extraction rate (example: 0.76) to get the wheat required: about 46 tonnes.
- Add an operating margin of 10% to 15% for maintenance, product changeovers and variations in wheat quality.
- Round up to the nearest standard capacity class — here, 50 T/24h.
That margin is not a luxury. A mill running at 100% of its nameplate capacity around the clock has no flexibility left to absorb seasonal orders or to handle damp wheat that slows the cleaning section.
Extraction rate: the number that defines profit
Extraction rate is the weight of flour produced divided by the weight of clean wheat entering the mill. For commercial white flour it realistically sits between 72% and 78%, and can reach 80% for all-purpose grades, while wholemeal flour runs far higher. The balance is bran and middlings — a saleable animal-feed by-product that belongs in your feasibility study rather than being ignored.
Be wary of offers promising an 82% extraction rate on premium white flour; a high figure achieved at the expense of flour purity shows up immediately in the ash content. Always tie the guaranteed rate to a specified ash value and a reference wheat type — a rate quoted without an ash specification is a meaningless promise.
Roller mill pairs and total roll length
The mechanical heart of the plant is the roller mill set, split between the break system and the reduction system. Typical specific loading runs from 45 to 60 kg of wheat per centimetre of roll length per 24 hours. In practice, a 50 T/24h mill needs a total roll length of roughly 9 to 11 metres, usually delivered as four to six double roller mills. Any offer with substantially less roll length means either less capacity than advertised, or forced grinding that raises flour temperature and lowers quality.
Matching that is the sieving area in the plansifter and the number of purifiers. Insufficient sieving area is the most common hidden bottleneck in budget mills: the rolls break the kernel efficiently, but the system cannot separate the output, material is recirculated, and real throughput drops.
Comparing common capacity classes
| Capacity (T/24h) | Approximate installed power | Building footprint and height | Typical application |
|---|---|---|---|
| 10 – 20 | 90 – 160 kW | 200 m² / 3 floors | Local mill or integrated bakery |
| 30 – 50 | 250 – 400 kW | 350 m² / 4 floors | Serving a mid-sized city |
| 100 – 150 | 700 – 1100 kW | 600 m² / 5 floors | Regional distribution and retail packs |
| 200 and above | 1400 kW and above | 900 m² and above / 6 floors | Large industrial mill |
Specific energy consumption in milling normally falls between 60 and 90 kWh per tonne of wheat, rising with harder wheat and finer finished products. Use that figure to sanity-check the installed power stated in any quotation.
Cleaning and conditioning: half the mill's success
Good milling begins before the rolls. Wheat needs separation of impurities, stones and metals, then scouring or surface peeling, then water addition and storage in tempering bins for 18 to 24 hours until moisture reaches about 16%. This step makes the bran tough so it separates cleanly from the endosperm, and lifts extraction by one to two percentage points with no change to the grinding system at all. Any quotation that does not detail the number and volume of tempering bins is incomplete.
Recurring mistakes when importing
- Accepting a guaranteed extraction rate without specifying wheat type and ash content.
- Overlooking building height: mills work by gravity and need multiple floors, not a single horizontal hall.
- Ignoring the aspiration and dust system, which accounts for a significant share of installed power.
- Buying the mill without a packing section matched to the pack sizes your market demands.
- Failing to require a trial run on the buyer's own wheat during pre-shipment inspection.
The golden rule: never sign a mill contract before three numbers appear together in one document — capacity in T/24h, extraction rate at a defined ash specification, and total roll length. If any one is missing, the guarantee is just words.
Checklist before requesting a quotation
- A complete flow sheet signed by the supplier showing every break and reduction passage.
- A roller mill schedule: quantity, diameters, lengths and motor power for each unit.
- Total sieving area and the number of plansifter compartments.
- Reference wheat specification: moisture, test weight and protein content.
- Export and machinery-safety conformity certificates such as CE.
- A priced wear-parts list covering two years of operation.
Choosing a flour mill is an engineering decision before it is a purchasing decision, and getting the numbers right in your specification saves you years of under-capacity production. Contact our team for a capacity study and a preliminary flow sheet for your mill before you request quotations from Chinese manufacturers.