Experience of long-term operation and maintenance

2022-08-20
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Experience of long-term operation and maintenance of small air separation equipment

the working cycle of fractionator reaches one year: the key is purifier

Fujian Huian civil affairs Changqing oxygen plant has a set of kfs-300 air separation equipment, which was produced by Harbin oxygen plant in 1979, and is equipped with L-5/55 horizontal oil lubricated air compressor. Use molecular sieve to purify the air. The working cycle of the originally designed fractionator is 30 ~ 60 days and nights. In actual production, the equipment has been in normal operation since the Spring Festival in 2000, 2001 and 2002 respectively, and the average working cycle of the fractionator has reached more than one year

in these three years of operation, the final stage pressure of the air compressor and the pressure of the fractionator heat exchanger have always maintained 0.2MPa. At present, the wheels of this suitcase account for a large weight pressure difference; When the inlet pressure of fractionator and expander is normal, it is basically balanced. The throttle-1 valve, throttle-2 valve and throttle-3 valve have never been blocked, and there is no need to scrape frost. The liquid oxygen level has been maintained at about 400mm carbon tetrachloride column; The purity of oxygen is above 99.8%; The average oxygen production is about 11 bottles per hour in hot days (13.5mpa pressure); On average, about 12 bottles are filled every hour in cold weather. Other technical indicators are basically normal

in order to prolong the working cycle of fractionator for small air separation equipment, it is very important to solve two points:

the first is to make good use of the use and regeneration of purifier. In particular, the use, heating and cooling of molecular sieves should be strictly controlled. Because the time of these three links is linked, and the time of one link is not well controlled, not only water, acetylene and carbon dioxide will be brought to the fractionator, but also the heating time and cooling time of the purifier will be extended, which will prolong the service time of the other group of purifiers, which will cause a serious vicious cycle

second, change the temperature control at the heating outlet of the purifier to time control. This is critical. The heating time of the purifier of small air separation equipment is controlled by the outlet temperature. When the outlet temperature reaches the set 80 ℃ ~100 ℃, the heating will be automatically cut off. In fact, the outlet temperature is affected by many factors. For example, temperature, air, humidity, air volume, pressure and the use of molecular sieves will directly affect the length of heating time, sometimes even 1-2 hours. If the outlet temperature cannot reach the set temperature, the heating will continue, which will inevitably affect the cooling time. At present, the heating of medium and large-scale air separation purifiers is not based on the outlet temperature, but on the time. The heating time is set between 180 ~ 200 minutes, which ensures that there is enough time to cool the molecular sieve. Therefore, the heating time of the purifier of small air separation equipment can also be subject to. Before October, 1999, the heating time of the plant was controlled by the outlet temperature. As a result, the heating and cooling of the purifier were often too late, and the service time of the purifier was often forced to be extended, so the work of the fractionator could not work normally. The throttle valve was often blocked. You can carry out the tensile test of liquid oxygen on a machine. The liquid level did not go up, and the fractionator had to be heated once in 30~60 days. After October, 1999, it was emphasized that the heating time of the purifier was strictly controlled between 180 and 200 minutes. When the heating time came, no matter how many degrees the outlet temperature was, the heating was stopped, and as a result, everything improved

because in the early stage of cooling molecular sieve, it is actually the continuation of strength and temperature. Considering that consumers are constantly seeking high-quality shoe products that can improve the wearing experience. We can observe that after the heating stops, the outlet temperature will continue to rise to more than 80 ℃, basically reaching adhesives and coatings: adhesives, adhesives, composite adhesives, reinforcing agents, starch adhesives, sealing adhesives, emulsions, resins, self-adhesive; The temperature requirements of molecular sieve regeneration are. Therefore, as long as the purifier is not used for a long time, the inlet temperature is controlled between 280~320 ℃ during heating, and the heating time is not less than 3 hours

in addition, there are several points worth noting:

(1) the use time of the purifier should be strictly in accordance with the time specified in the operation manual, and there should be room for more than less. Generally, small air separation equipment is switched every 8 hours, which should be strictly observed

(2) for cooling time, if the outlet temperature cannot be reduced to within 40 ℃ within 4.5 hours, a blower should be installed, or the cause should be found out and eliminated

(3) when switching the purifier, the pressure equalizing process should be controlled in about 20 minutes. A long time of pressure equalizing is equal to an extended service time. In our previous inspection, we found that the 12 hour switch recorded on the record sheet was accurate, but the pressure equalization time took more than an hour, and in fact, the use of the purifier has exceeded 13 hours. In order to avoid similar situations, it should be emphasized that the switching time recorded on the record sheet should be the time when the switching is started, rather than the time when the switching is started, so as to promote the operator to equalize the voltage on time and switch in time

2 tips for air separation equipment maintenance

2.1 the chamfer of the inner circle of the compressor air valve disc can prolong the service life of the air valve

if the compressor air valve runs for a long time, the valve disc will be offset and leak if the limiter is scratched. If the sharp inner circle right angle of the valve disc of the new air valve is filed away with a file in advance to make it an obtuse angle, it will slow down the scratching of the right angle of the valve disc on the lifting limiter and greatly prolong the service life of the air valve

2.2 adding filtration to the primary air inlet of the oxygen compressor is conducive to safe operation.

3z3..67/150 and 3z3.5-2.833/150 oxygen compressors in operation, the common fault is the sudden overpressure of the low pressure stage. In addition to the damage of the later stage air valve, most of these faults are caused by the valve disc being stuck by dirt. These dirty things are mainly sucked in from the rust pieces and leather cup fragments in the air inlet pipe and air storage box. If a filter is added to the outside of the primary air inlet, this phenomenon can be reduced or avoided. The addition of filtering is also very simple. Prepare a piece in advance Φ About 120mm, with a specification of 2 × 2mm stainless steel or copper wire. After disassembling the primary cylinder head, put the filter on the air inlet, and then tighten the nut on the cylinder head

about the author: Cheng Kairong (1945-), male, former installation engineer and technical team leader of the gas supply workshop of Fujian Refining and chemical company, now specially employed by Fujian Huian Changqing oxygen plant

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