The temperature and specific enthalpy (H ′ 2) of the low pressure saturated liquid and the enthalpy (H ″ 2) of the saturated steam remain unchanged due to the constant pressure of the upper tower. That is to say, in the above formula, only the value of the molecule (h1-h ′ 2) decreases, while the denominator (H ″ 2-h ′ 2) remains unchanged, resulting in the decrease of gasification rate. Generally, the gasification rate can be reduced to about 11% under the above subcooling conditions.DEAR Air separation equipment.When the amount of backflow gas increases and the amount of positive flow air and its inlet temperature remain unchanged, the situation is opposite to the above. That is to say, the middle temperature decreases, the cold end temperature decreases, the cold end temperature difference decreases, and the hot end temperature difference expands. The range of temperature change in the middle is also larger than that in the end. To sum up, the change of middle temperature can reflect the change of cold end and hot end temperature condition, and the change is significant and easy to detect.
The adjustment of the temperature condition of the accumulator (or switching heat exchanger) is based on the middle temperature. The "middle part" here does not refer to the median position in geometric dimension, but refers to the temperature on the cylinder (or switching channel) near the outlet of the middle suction or circulation.DEAR Air separation equipment.Scale attached to the cooler wall, nitrogen water precooler packing, nozzle or sieve, not only affect the heat transfer, reduce the cooling effect, but also hinder the circulation of cooling water or air, serious equipment failure will be caused, such as nitrogen water precooler with water, so that the accumulator (or heat exchanger) frozen. The scale is hard and hard to remove.DEAR Air separation equipment.Adjust the excess hydrogen in hydrodeaeration to meet the process requirements. Adjust the working conditions of the deaerator, and the furnace temperature is generally stable between 350 ℃ and 450 ℃ (if the furnace temperature does not meet the requirements, the palladium metal on the surface of the palladium catalyst may be lost due to long-term use, and the efficiency will be reduced, so the palladium catalyst can be replaced);
At both ends of the channel, the flow direction of the fluid is changed by using guide vanes, and the outlet and inlet of the same fluid are respectively concentrated on one side. For example, air and sewage nitrogen are set at the upper and lower sides, and oxygen, pure nitrogen and circulation are set at the left and right sides. Generally, cold and hot fluids are arranged in reverse or cross flow. Then connect the head, gather all the channels of the same fluid, and weld the corresponding pipes to realize the heat exchange between several streams.DEAR Air separation equipment.Annular or U-shaped condensing isolation pipe must be added to the pipeline used for the detection of steam or other condensing gas near mounted instruments to prevent overheating of measuring elements; for the positive and negative pressure detection pipelines of flow and liquid level, the length and number of elbows shall be consistent as far as possible, so as to make the resistance of positive and negative pressure pipelines the same and eliminate the instrument error caused by local resistance of pipelines;
DEAR Air separation equipment.For carbon dioxide, the cold end temperature should be below - 133.5 ℃ before some carbon dioxide begins to precipitate in the heat exchanger. The carbon dioxide content at the cold end is the saturation content corresponding to the temperature at that time. According to the above method, the minimum allowable temperature of carbon dioxide in the expander can also be determined.The temperature of the liquid blown out from the automatic valve box of the accumulator (or switching heat exchanger) or the backflow sewage nitrogen at the cold end is about - 180 ℃, which is the sign that the air at the cold end of the accumulator (or switching heat exchanger) is liquefied. The harm of air liquefaction at the cold end is great, mainly as follows: part of the liquefied air is deposited in the automatic valve box (or at the bottom of the cold accumulator), and part of it is brought into the tower with the air, so that the moisture content of the air entering the tower increases, and the liquid air purity (oxygen content) decreases.
