Equipment requirements for calorimetry systems

The calorimetry system consists of an oxygen bomb, inner cylinder, outer cylinder, agitator, water, temperature sensor, ignition device, temperature measurement and control system.

 1 oxygen bomb

Oxygen bomb materials are heat-resistant and corrosion-resistant; The volume of oxygen bombs is generally between (250~350) mL; Water pressure test, China's oxygen bomb water pressure test is 20MPa, with a validity period of 2 years; The oxygenation pressure and time are (2.8~3.0 MPa) and continuous oxygenation is maintained for more than 15 days.

 2 inner tubes 

The inner cylinder material can be made of copper, brass, or stainless steel; The cross-sectional shape of the inner cylinder can be elliptical, diamond, or other shapes; The inner cylinder has a capacity to hold (2000-3000) mL of water. 

The water volume requirement for the inner cylinder is to add water to the inner cylinder after inserting the oxygen bomb, so that the top surface of the oxygen bomb cover is submerged (10-20) mm below the water. If the water volume is too high, stirring will cause splashing, while if the water volume is too low, stirring will cause the oxygen bomb cover to be exposed, and some heat will not be absorbed by the water. The same is maintained in all experiments, with a difference of no more than 0.5g. The internal cylinder water inlet method can be divided into weighing method, balance method, measuring cup method, and water level probe quantitative method.

 3 outer cylinder

The outer cylinder is a double walled container made of metal, with a circular outer wall shape and an inner wall shape that depends on the shape of the inner cylinder; The assembly requirements for the outer cylinder are that the outer cylinder should completely surround the inner cylinder, and there should be a distance of (10-20) mm between the inner and outer cylinders to minimize heat exchange between them. 

The temperature control method of the outer cylinder can be divided into automatic temperature control outer cylinder and static form outer cylinder.

 4 agitators

 The mixing methods are divided into propeller type and electromagnetic type, but both require electric motor drive. The speed is generally between (400-600) r/min, and based on experience, a speed of 500r/min is ideal and should be kept constant. It should not be too fast or too slow. The ignition time to the endpoint should not exceed 10 minutes. If it exceeds 10 minutes, it indicates that the mixing efficiency is not sufficient. Stirring heat: When the water temperature of the inner and outer cylinders is consistent with room temperature, the heat generated by continuous stirring for 10 minutes should not exceed 120J.

 5 thermometers 

Use a platinum resistor to read temperature, with a temperature resolution of at least 0.001K.

 6 ignition device

 Ignition power supply

Generally, (24-36) V DC or AC power supply is used. There are two types of ignition methods: fusible and non fusible. Fusible installation is more convenient, but it is prone to short circuits and burns out the crucible and crucible support. Non fusible installation is a bit troublesome, but safe, and will not burn out the crucible and crucible support.

 7 Oxygen, pressure gauge and heating crucible

 The oxygen purity requirement is 99.5%. A pressure gauge consists of two heads, one indicating the pressure in the oxygen cylinder and the other indicating the pressure filled into the oxygen bomb during oxygenation. The meter head should be equipped with a pressure reducing valve and a safety valve. Pressure A Biao should be verified by the metrology department every 2 years to ensure correct instructions and safe operation.

 Heat generating crucibles can generally be made of nickel chromium steel products, which can ensure complete combustion of the sample without corrosion or thermal effects. They are divided into deep walled crucibles and shallow walled crucibles based on the principle.