Ensure the safe operation of the air separation un

Ensure the safe operation of the air separation unit in the refinery area

the most likely safety accident of the air separation unit is the explosion of the main condenser generator due to the excessive total hydrocarbon content of the unit. Therefore, the air quality at the air intake of the air separation unit is required to be high. Generally, the total hydrocarbon content in the air at the air intake of the air separation unit is required to be less than 8 ×。 However, the leakage or discharge of hydrocarbon gases from various units in the refinery unit area results in a high content of hydrocarbon gases in the air, so the total hydrocarbon content in the air at the suction of the air separation unit in the refinery unit area is high. Therefore, how to ensure the safe operation of the air separation unit in the refinery unit area is an urgent problem to be solved

there are two sets of kdn-2000 full low-pressure a high-purity nitrogen devices in the series and branch workshop of refinery Shantou plant of Urumqi Petrochemical Company, each of which has a nitrogen production of 2000m32 and is manufactured by Kaifeng Air Separation Plant/h during the test experiment. It was put into operation in October, 1993. 6. Adjust the iron plug clearance of each part. According to the production needs, open a set of nitrogen for the production of oil refineries, chemical fiber plants and other units. Since the test run at the end of 1993, the total hydrocarbon content of the main cooling system has exceeded the standard (the warning value is 100 as stipulated by SINOPEC) ×； Parking value 250 × Or if the single value is below the warning value, the total hydrocarbon value can be increased to 500 ×)， Later, with the assistance and help of relevant units of the plant, the total hydrocarbon content of main cooling was effectively controlled, and the total hydrocarbon content of main cooling increased from an average of 320 at the beginning of commissioning × Down to the current average of 95 ×。 But sometimes due to environmental factors, the total hydrocarbon of main cooling is sometimes higher, at 200 ×~ two hundred and fifty × Between

2 danger of hydrocarbon compounds to the air separation unit

since the air separation unit was put into operation at the end of 1993, the main reason why the total hydrocarbon content of the main cooling system has exceeded the standard is that there are many harmful impurities in the air, the main components of which are C2H2, CH4, C2H6 and other hydrocarbon compounds (C3H6, C3H8, c4+), etc. NOx and O3 also have a certain content in the air, of which CH4 and C2H6 are difficult to remove, and C2H2 is the most dangerous. The sources of these gas impurities are mainly refinery waste gas emissions and the running, emitting, dripping and leakage of various devices

these hydrocarbons accumulate in liquid air (especially in oxygen enriched liquid air), and are likely to explode under some detonation causes. In order to make dangerous hydrocarbons explode, they must be impacted or subjected to frictional electrostatic discharge. The minimum value of energy required for this explosion is called sensitivity. Chemical reaction sensitive substances include O3, NOx and unstable peroxides, especially the presence of O3, which greatly increases the explosion sensitivity. The cause of industrial cold explosion of air separation equipment is likely to be caused by the hydrocarbon accumulated in liquid oxygen (or liquid string) encountering a certain ignition source. It is suspected that this ignition source is from unstable compounds. It is formed by O3 or nitrogen oxides accumulated in liquid oxygen and unstable carbon and oxygen compounds. Dangerous impurities in liquid oxygen, if saturated, will be separated out as solids with small specific gravity and float near the liquid level. Especially with the evaporation of liquid oxygen, it is easy to adsorb on the chopper or pipe wall of the liquid level, so it is easy to become the cause of explosion

among all hydrocarbon impurities, acetylene is generally considered to be the most dangerous to the air separation unit, and the tested cable should be fully discharged, which is more dangerous in the case of saturation; When saturation is not reached, acetylene may exist in the main cooling, which will form local accumulation and is also dangerous. However, acetylene is not the only impurity with explosive risk. It is explosive in liquid oxygen (oxygen rich liquid air) and other hydrocarbons. Nike also cooperates with its partners everywhere

3 the main factor that the main cooling of the air separation unit in the refinery exceeds the standard

the main factor that the main cooling of the air separation unit in the refinery exceeds the standard is the high content of total hydrocarbons in the air at the suction inlet. The main reasons are:

3.1 the location of the air separation unit is improper

the air separation unit in our plant is located in the northwest corner of the refinery, less than 100 meters away from the atmospheric pressure unit of the nearest refining unit, and 60 meters away from the purified water explosion pool

3.2 the total hydrocarbon content around the air separation unit is high

since May 1994, according to the requirements of the refinery, eight monitoring points have been set around the air separation unit (see Figure 1). The environmental monitoring center monitors these eight points every week. According to the monitoring data (see Table 1), it can be seen that the total hydrocarbon at the highest point 6 (northwest corner of the air separation unit) is as high as 50 ×， The average value is 14.78 ×， It is much higher than the total hydrocarbon content of the air intake of the air separation unit of the original Petrochemical Corporation, which is less than 8 × Requirements

Table 1 monitoring value of total hydrocarbon content in atmospheric air（ ×）