Semi-Micro Oxygen Bomb Calorimeter

What is the Semi-Micro Oxygen Bomb Calorimeter?

A semi-micro oxygen bomb calorimeter measures calorific value on samples of roughly 0.1 to 0.5 g, using a smaller bomb and cup. It is used when only limited material is available or for screening crushed coal and coke fractions.

Overview

This instrument scales the bomb, cup and water system down so that a determination needs only a few tenths of a gram. Heat release is smaller, so the temperature sensor and the water equivalent are matched to the reduced scale, and the software applies the same corrections as a full-size calorimeter. The advantage is that scarce or valuable material, such as core samples, individual lithotypes or single coal particles, can be tested, and small fractions from a size analysis can be compared. The limitation is sample heterogeneity: coal is not uniform, so a smaller mass represents the lot less well and scatter between replicates is higher. Semi-micro instruments are therefore used for screening, research and comparison rather than for contract settlement, where full-size determinations with reference materials apply.

How does it work?

A bomb calorimeter burns a pressed pellet of coal, about 0.5 to 1 g, in a high-pressure oxygen bomb immersed in a measured volume of water. The heat released raises the water temperature, and the temperature rise multiplied by the effective heat capacity of the system, called the water equivalent, gives the energy released. Corrections are applied for fuse wire, acid formation and the mass of the crucible contents. In an isoperibol design the jacket stays at a fixed temperature and the temperature-time curve is computed, in an adiabatic design the jacket follows the bomb temperature so heat loss is nearly zero, and in a manual static design the operator reads temperatures and applies a radiation correction. A microprocessor logs the curve, derives the water equivalent from certified benzoic acid and reports the result in MJ/kg.

What are the key features?

• Bomb and cup scaled for 0.1–0.5 g samples
• High-sensitivity temperature sensor for small heat release
• Water equivalent matched to the reduced thermal scale
• Software applies fuse wire and acid corrections
• Suitable for core samples and single-particle testing
• Compact bench footprint for research laboratories

What are the technical specifications?

A typical semi-micro oxygen bomb calorimeter configuration offers sample mass of 0.1–0.5 g, calorific value range of 5–35 MJ/kg, oxygen charging pressure of 25–30 bar, temperature resolution of 0.0001 °C, repeatability of ≤ 0.3 % RSD at 0.3 g and test duration of 10–15 min. 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 Semi-Micro Oxygen Bomb Calorimeter is used in core sample and single-particle testing, screening crushed coal and coke fractions and research on coal rank and maceral concentrates. Across the wider Calorimeters class, laboratories also deploy it for coal calorific value for pricing, power plant boiler efficiency monitoring and cement and steel kiln fuel checks.

Which standards and certifications apply?

Relevant standards and methods include ASTM D5865, ISO 1928, GB/T 213, ASTM D3175, ISO 18125, ASTM E711 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.

Install the calorimeter on a stable bench away from direct sunlight, draughts and heat sources, because ambient stability affects jacket temperature. Use oxygen of the specified purity from a regulator fitted with a pressure relief, and inspect the bomb, seals and valves on a schedule. Verify the water equivalent at the start of each working session with certified benzoic acid and monitor it as a trend, since drift indicates a leaking bomb, contaminated water or a failing sensor. Keep records of calibration and reference coal results, and compare them with the tolerances stated in the method. Confirm that report basis, sulfur and moisture corrections in the software match your contract.

How do I select the right Semi-Micro Oxygen Bomb Calorimeter?

Select a semi-micro calorimeter only when sample quantity is the limiting factor, and accept the higher scatter that comes with a small mass. Ask for repeatability data at the sample mass you plan to use, and keep a full-size instrument or a reference laboratory for settlement testing.

How does it compare with other Calorimeters variants?

Selection turns on required accuracy, sample throughput and how much operator attention your laboratory can accept. Manual static-jacket units are the least expensive and are adequate for occasional checks, but they depend on the operator for temperature reading and correction. Isoperibol instruments dominate routine coal laboratories because they combine good accuracy with automatic temperature logging. Adiabatic calorimeters give the highest precision for reference work and for samples that burn slowly, such as some cokes and biomass, but they cost more and need careful setup. Check water-equivalent stability, reported resolution, the type of oxygen filling system, availability of benzoic acid and certified reference coal, and whether the software reports on the as-received, dry or dry ash-free basis your contract expects.