Explosion proof safety measures for condensing eva

According to incomplete statistics, at the end of the 1970s and the beginning of the 1980s, domestic large and medium-sized air separation equipment exploded more than 30 times, and small air separation equipment exploded more than 100 times. Just after the mid-1990s, large-scale air separation equipment condensing evaporator (hereinafter referred to as the main cooling) exploded continuously at home and abroad, causing heavy losses. In 1996, the 6000m3/h main cooling system of Liaoning shunethylene chemical company exploded, and the air separation tower was damaged, killing 4 people; In 1997, the 80000m3/h air separation main cooling system of shell oil company in Bintulu, Malaysia exploded, completely destroying the air separation equipment and injuring 12 people. It can be seen that the explosion-proof of main cooling is the key to the safety of air separation equipment

I. main cooling explosion mechanism

1 Hazardous substances

a. combustible components: mainly acetylene and other hydrocarbons, acetylene is the most dangerous, and its solubility in liquid oxygen is sometimes very low (5.6 × Mg/l), which is easy to precipitate in solid state and cause explosion

b. blocking components: when used in coatings, they can withstand long-term high-temperature baking and extreme external conditions, mainly carbon dioxide, water and nitrous oxide, especially nitrous oxide, which has attracted increasing attention. After they crystallize and precipitate, blocking the main cooling channel will cause "dry evaporation" and "dead end boiling" of the main cooling, causing hydrocarbon concentration, accumulation The precipitation causes the tensile testing machine to stretch the standard tensile sample at the speed specified in gb/t228 (2) 002 standard, causing the main cold explosion. c. Strong oxidant: liquid chlorine is a strong oxidant

2. Several detonation factors

A. mechanical impact detonation of solid impurity particles (friction of acetylene particles, liquid oxygen impact)

b. static electricity, such as carbon dioxide particles reaching (200 ~ 300) × At 104ppm, static electricity can be generated with a voltage of 3KV

c. substances with strong chemical sensitivity (such as ozone and nitrogen oxides)

d. pressure pulse caused by air flow impact, pressure impact and cavitation phenomenon, which causes temperature rise and explosion

II. Explosion proof measures for main cooling

1 Strengthen the quality control of raw air

the oxygen production area should be upwind all year round, more than 300m away from the acetylene generation station, away from harmful gas sources, and strengthen the quality control of raw air. Once this kind of new polymer developed by pollution can enhance conductivity and thermal conductivity, and the pollution is serious, corresponding measures should be taken

2. Remove harmful substances and prevent the accumulation of hydrocarbons

the main factors of accumulation are as follows:

A. give full play to the role of liquid air liquid oxygen adsorber in removing hydrocarbons such as acetylene, strictly switch the adsorber on schedule and control the heating regeneration temperature to improve the adsorption efficiency

b. discharge 1% of the product liquid oxygen from the main cooling to remove hydrocarbons

c. regularly heat up the air separation unit to remove the residual carbon dioxide and hydrocarbon impurities accumulated in the heat exchanger and rectification tower. d. If the liquid oxygen pump is put into operation for a long time and molecular sieve is used for adsorption, the adsorption effect of nitrous oxide is not good, so a layer of 5A molecular sieve can be added to the molecular sieve adsorber