Oxygen analyzer is an industrial online process analysis instrument that is not only widely used in the detection of oxygen concentration in mixed gases in heating furnaces, chemical reaction vessels, underground wells, industrial nitrogen production, etc., but also widely used in the treatment of dissolved oxygen in boiler water and sewage Detection of dissolved oxygen in drainage outside the device. There are many types of trace oxygen analyzers, with different detection principles and strong pertinence. Therefore, appropriate instruments should be selected according to different use occasions and different process conditions.
- In the dew point measurement, the control of the mirror cooling processing speed is a very important development issue. For students, the automatic passage of the photoelectric oxygen analyzer is determined by design research, while for the oxygen analyzer with hand-controlled cooling capacity, it is a kind of operation. The problem. Because the heat conduction between the cooling point, the temperature measurement point and the mirror surface of the cold source has a learning process and there is a certain temperature gradient. Therefore, thermal inertia will affect the process and speed of condensation (frost), and bring some errors to the measurement results. This teaching situation varies with the choice of temperature measurement system components used in different countries. For example, due to the economic structure of the company, the temperature and gradient between the measurement point and the mirror surface of the platinum resistance temperature sensor are relatively large, and the heat transfer speed is relatively slow. , So that the temperature measurement and condensation can not achieve synchronization information. Moreover, the thickness of the exposed layer cannot be effectively controlled. This will produce a negative error for visual inspection.
2. The temperature of the measured gas is usually room temperature. Therefore, the air flow through the dew point chamber will inevitably affect the heat and mass transfer process of the system. When other conditions are constant, increasing the flow is beneficial to the mass transfer between the airflow and the mirror. Especially in the low frost point measurement, the flow rate should be increased appropriately to accelerate the formation of outcrops, but the flow rate should not be too large, otherwise it will cause overheating. This is especially true for thermoelectric refrigeration oxygen analyzers with low cooling power. When the flow is too large, the pressure in the dew point chamber will drop, and the change in flow will affect the thermal balance of the system. Therefore, it is very necessary to select the appropriate flow rate in the dew point measurement. The choice of flow depends on the cooling method and the structure of the dew point chamber. The general flow rate range is 0.4 to 0.7l/min-1. In order to reduce the influence of heat transfer, you can consider pre-cooling the measured gas before entering the dew point chamber.
3. Another problem is that the cooling rate is too fast may lead to “too cold”. We know that under certain conditions, when the water vapor is saturated, the liquid still does not appear, or the still water freezes. At a temperature below zero, it is called supersaturation or the phenomenon “too cold.” Used for condensation (or frost) In the process, this phenomenon is due to the fact that the measured gas is often very clean and reflective, even lacking a sufficient number of cores to cause condensation. Finnish has found in experiments that if a highly polished mirror surface and its cleanliness expect chemical requirements, the real formation temperature is a few degrees below the dew point of the dew point temperature. The supercooling phenomenon is temporary, the total duration and dew point or frost point temperature. This phenomenon can be observed through a microscope. One solution is to repeat the heating and cooling operation of the mirror until this is solved so far. Another solution is to directly use the vapor pressure data of supercooled water. Consistent with weather systems where the relative humidity is limited and when doing so is below zero.
