Hartmann apparatus

Note These values are based chi experiments using a 1-m3 sphere. Previous experimental studies on explosibility were carried out using the Hartmann apparatus which tends to give values for Kg, lower than the 1-m3 sphere (see Pineau et al., 1976). 

Explosion characteristics of dust clouds are generally examined by the Hartmann apparatus (Fig. 3.84) developed in USA. It consists of a vertical combustion tube of 1200 cm volume, 305 mm long and 64 mm inside dia., mounted over a brass dispersion cup. The powder sample is placed in the cup and dispersed by an air stream of 50 cm injected at a pressure of 7 bar. The ignition source is usually a pair of electrodes with a spark gap of 3 to 6 mm mounted at the lower one-third level of the tube. A wire coil igniter can also be used. 

Explosion characteristics of various types of powders as measured in the Hartmann apparatus are shown in Table 3.15. 

Ignition temperatures in the Godbert - Greenwald furnace and explosion characteristics measured by the Hartmann apparatus with plastics and other powders... 

Class of hazard Hartmann apparatus l-m explosion bomb ... 

The explosion classification test is usually conducted in a modified Hartmann tube apparatus. The apparatus consists of a 1.2 L vertical tube mounted onto a dust dispersion system. Dust samples of various quantities are dispersed in the tube and attempts are made to ignite the resulting dust cloud by a 10 J electrical arc ignition source. If the material fails to ignite in the modified Hartmann tube apparatus, the testing is continued in the 20 L sphere apparatus. Dust samples of various quantities are dispersed inside the sphere and are exposed to a 10,0001 ignition source. 

The exhaust gas average composition was the following 02=4%, C02=ll%, H20=12%, HC (as propane)=410 ppm, NOx=1220 ppm, CO=1310 ppm, N2=balance. The experiments were effected at space velocity of 30000 h. NOx, HC, CO and O2 concentrations were measured by on-line Rosemount analyzers chemiluminescence for NOx, flame ionisation for total HC, infrared for CO, and electrochemical for O2. N2O was measured by on-line Hartmann Braun infrared analyzer. An Applied Automation on-line gas-chromatograph, with a FID detector, was adopted to analyse the individual hydrocarbon concentrations. Other details of the experimental apparatus are described in [16]. 

The apparatus for kinetic tests is shown in Figure 1. It comprises a quartz tubular flow reactor 300 mm height and 20 mm internal diameter, heated by an electrical furnace. The reactor temperature was controlled by a programmer-controller (Ascon). Cylinder air (99.999 % purity) was fed to the reactor and the flow rate was controlled by mass flow controllers (Hi-Tec). Exhaust gas concentrations were determined by Hartmann Braun continuous analysers Uras lOE (for carbon monoxide and carbon dioxide) and Magnos 6G (for oxygen). The signals from the analysers were acquired and processed by a personal computer which also performed the control of the experiment. 

The violence of explosion parameters has been determined for many years in the United Kingdom and the United States in the Hartmann bomb apparatus of 1.3-L mm capacity (Figure 56.7a) [9]. 

FIGURE 56.7 Apparatus for testing dryer explosion characteristics for organic powders, (a) Hartmann bomb apparatus, (b) Chemical igniter. 

The analysis of NO and NO2 was effected by a continuous chemiluminescence apparatus (Beckmann model 955), NH3 was detected by a continuous IR spectrophotometer (Hartmann Braun model Uras 30y N2 and N2O concentrations were measured by gaschromatographic analysis on a double packed 5A molecular sieves-Porapak Q by a Hewlett Packard instrument (model 5890) with a TCD detector. 

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