Laboratory Hammer Mill for Coal

What is the Laboratory Hammer Mill for Coal?

A laboratory hammer mill reduces crushed coal to about one to three millimetres in a single pass using swinging hammers and a screen, handling higher throughput than a jaw crusher. It bridges the gap between crushing and pulverizing.

Overview

Material enters the top of a chamber where hammers mounted on a rotating shaft strike it against a breaker plate. Particles leave through a screen that sets the product size, so the screen aperture, not the gap, controls fineness. Hammer mills accept feed of about 20 to 50 mm and reduce it to one to three millimetres at rates from 100 to 1000 kg per hour, which makes them suitable for continuous flows and for secondary size reduction. Because the product has a wide size spread, a final pulverizing stage is still needed for analysis samples. Coal dust and moisture are the main concerns: the chamber should be sealed with an extraction port, and screens, hammers and liners must be checked for wear, since a torn screen lets oversize particles pass and worn hammers reduce throughput and increase heat.

How does it work?

Coal is heterogeneous, so sample preparation must cut particle size and sample mass without changing composition. Size reduction proceeds in stages: a jaw or roll crusher takes lump coal down to a few millimetres, a hammer mill or crusher reduces it to about one millimetre, and a vibratory ring mill or disc pulverizer grinds a laboratory portion below 200 µm, or to 75 µm for ash and elemental work. Between stages the sample must be mixed and divided, because mass reduction must be proportional: a riffle divider splits a stream into two equal halves through alternate chutes, and a rotary divider collects a controlled stream in rotating vessels to give identical fractions. Moisture control is critical, so equipment is enclosed, pass-through times are short and contact surfaces are chosen to avoid adding iron or other contamination that would bias ash and elemental results.

What are the key features?

• Swinging hammers with hardened or tungsten carbide tips
• Exchangeable screens setting product size
• Feed size up to about 50 mm
• Continuous throughput for sample flows
• Sealed chamber with dust extraction port
• Quick-opening casing for cleaning between samples

What are the technical specifications?

A typical laboratory hammer mill for coal configuration offers maximum feed size of 20–50 mm, product size of 1–3 mm with 1–3 mm screen, throughput of 100–1000 kg/h, rotor speed of 1000–3000 rpm, screen options of 1, 2, 3, 6 mm and hammer material of Hardened steel or tungsten carbide. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Laboratory Hammer Mill for Coal is used in second-stage coal size reduction, continuous sample flows in plant laboratories, coke and biofuel crushing and preparation before pulverizing. Across the wider Coal Sample Preparation class, laboratories also deploy it for coal mine and preparation plant sample chains, power station coal quality laboratories and commercial inspection sample preparation.

Which standards and certifications apply?

Relevant standards and methods include ASTM D2013, ASTM D2234, ISO 1988, ISO 13909-1, ISO 18283, GB/T 474, GB/T 475 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Prepare samples in a controlled room where moisture loss is limited, and work quickly through each stage, weighing after every division so that mass balance can be checked. Clean equipment between samples with brushes and, where necessary, by running a small amount of the next sample through, to avoid cross-contamination. Record the top size, mass and equipment settings for each stage so the reduction history can be audited. Keep grinding sets within wear limits, since worn plates change product size and can raise ash through iron pick-up. Guard feed openings, provide dust extraction rated for coal dust and use motors and switches suitable for a dusty environment. Reference materials and duplicate samples should be put through the same chain as routine samples to verify that no bias is introduced.

How do I select the right Laboratory Hammer Mill for Coal?

Use the hammer mill where throughput and continuous operation matter more than a narrow size range, and keep a pulverizer for the final analysis sample. Specify screen apertures, hammer material, feed size and extraction, and factor spare screens and hammers into the running cost.

How does it compare with other Coal Sample Preparation variants?

Plan the whole chain before buying individual machines. Match the top size of incoming material to crusher feed openings and the required final fineness to the pulverizer, and keep reduction ratios moderate by using several stages rather than one large step. Check throughput against the number of samples per shift, and check that the product size table of the sampling standard is respected, since the minimum sample mass depends on top size. Choose contact materials with contamination in mind: manganese steel wears well but adds iron, while tungsten carbide or ceramic grinding sets cost more and keep ash and trace element results cleaner. Look for enclosed, dust-tight designs with extraction connections, quick-release bowls or plates for cleaning, and drives rated for continuous duty. For dividing, riffle dividers suit gravity flows and rotary dividers give the best precision on fine coal.