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When it comes to the gas storage tank, we all think that the bigger the better, this can effectively reduce the frequency of restarting the host, reduce the damage of the instantaneous current to the equipment circuit, and prolong the service life of the gas storage tank. In addition to its own function as a gas storage tank, the gas storage tank is also a nitrogen generator action and energy-saving effect equipment. The adsorption tower of the nitrogen generator switches every minute, and the boosting time for each switching is only 1~2 seconds, which means that the instantaneous gas consumption is very large. If there is no buffer effect of the gas storage tank, a large amount of compressed air directly enters the system. The nitrogen system cannot be processed in an instant. In this way, the large amount of water and oil contained in the compressed air will definitely poison the molecular sieve inside the nitrogen generator, shorten the service life of the molecular sieve, reduce the gas production rate, and increase the user cost. If there is an air storage tank, the compressed air here will stay for a certain period of time, which can precipitate foreign matter such as impurities and moisture in the air, and the temperature of the compressed air is also reduced, which can send out higher quality compressed air. At the same time, it can also ensure that the compressed air pressure is maintained at a good set value, and the gas system can obtain a stable pressure, which is very necessary for the use of modern factories.

First, Comparison of various nitrogen sources

1. Nitrogen bottle

The cylinder volume is 40L, the rated pressure is 15MPa, and the full gas storage is 6m3. According to different needs of users, the purity of bottled nitrogen is 99.5%, 99.999% and 99.999%. Due to the different supply and demand in different places, the price of bottled high-purity nitrogen varies greatly, ranging from 18 to 90 yuan/bottle, that is, the nitrogen price is 3 to 15 yuan/m3.

2. Liquid nitrogen

Liquid nitrogen is the product of cryogenic air separation nitrogen production. Under standard conditions, 1m3 of liquid nitrogen can be gasified into 643m3 of nitrogen, but the actual utilization rate during use is generally around 95%, that is, the nitrogen that 1m3 of liquid nitrogen can actually use. About 610m3 or so. At present, the average price of liquid nitrogen in the market is about 1,000 yuan/m3, and the unit price of nitrogen is 1.67 yuan/m3. When using liquid nitrogen, the user must be equipped with a liquid nitrogen storage tank, a vaporizer corresponding to the flow rate, and a pressure regulating valve corresponding to the pressure, which is a necessary initial investment.

3. Nitrogen production on site

On-site nitrogen production refers to nitrogen production with nitrogen production equipment purchased by nitrogen users. At present, there are three types of industrial-scale nitrogen production at home and abroad: cryogenic air separation nitrogen production, pressure swing adsorption nitrogen production and membrane separation nitrogen production.

3.1 Nitrogen production by cryogenic air separation

It is a traditional air separation technology with a history of more than 90 years. It is characterized by large gas production and high nitrogen purity. However, it has a complex process, a large area and high infrastructure costs, requiring special Maintenance force, many operators, slow gas production (18 ~ 24h), it is suitable for large-scale industrial nitrogen production, and the nitrogen cost is about 0.7 yuan/m3.

3.2 PSA nitrogen production

Pressure Swing Adsorption (PSA) gas separation technology is an important branch of non-cryogenic gas separation technology. It is the result of people's long-term efforts to find a simpler air separation method than the cryogenic method. A strong competitor to cryogenic air separation. It uses air as raw material, uses carbon molecular sieve as adsorbent, utilizes the characteristics of carbon molecular sieve to selectively adsorb oxygen and nitrogen in the air, and uses the principle of pressure swing adsorption (pressure adsorption, decompression desorption and molecular sieve regeneration) at room temperature. Separation of oxygen and nitrogen to produce nitrogen. Compared with cryogenic air separation nitrogen production, pressure swing adsorption nitrogen production has remarkable characteristics: adsorption and separation is carried out at room temperature, the process is simple, the equipment is compact, the area is small, the start and stop are convenient, the start-up is rapid, and the gas production is fast ( Generally about 20~30min), low energy consumption, low operating cost, high degree of automation, convenient operation and maintenance, convenient skid installation, no need for special foundation, product nitrogen purity can be adjusted within a certain range, nitrogen production ≤ 2000Nm3/h. The cost of nitrogen is about 0.4 yuan/m3.

3.3 Nitrogen production by membrane separation air separation

Membrane separation air separation nitrogen production is also a new branch of non-low temperature nitrogen production technology. It is a new nitrogen production method developed rapidly abroad in the 1980s. It uses air as raw material, and under certain pressure, utilizes the different permeation rates of oxygen and nitrogen in the hollow fiber membrane to separate oxygen and nitrogen to produce nitrogen. Compared with the above two nitrogen production methods, it has the characteristics of simpler equipment structure, smaller volume, no switching valve, easier operation and maintenance, faster gas production (within 3 minutes), and more convenient capacity expansion. The fiber membrane has stricter requirements on the cleanliness of the compressed air. The membrane is easy to age and fail, and it is difficult to repair. It needs to be replaced with a new membrane. The membrane separation nitrogen production is more suitable for small and medium-sized users whose nitrogen purity requirements are less than or equal to 98%. At this time, it has the best function. Price ratio: When the nitrogen purity is required to be higher than 98%, the price is about 30% higher than that of the pressure swing adsorption nitrogen generator of the same specification, so there is no competitive advantage.

Second, Nitrogen source ash injection phenomenon

The phenomenon of soot spraying of nitrogen generators is also called carbon molecular sieve pulverization, which occurs because the carbon molecular sieve is not tightly pressed or the carbon molecular sieve is loose.

Structural faults of the adsorption tower caused by the impact of the nitrogen generator or the movement of the equipment during the use of the nitrogen generator, such as the desoldering of the adsorption tower pipeline, the outflow of the carbon molecular sieve, and the looseness and pulverization of the carbon molecular sieve. The substances ejected from the muffler generally have small particles, and we need to check whether the particles are activated carbon or molecular sieves. Because activated carbon and molecular sieve are black solid particles, it is difficult to distinguish from the color, but their particle shapes are different. If activated carbon is sprayed out, then the problem is not serious. We can remove the activated carbon filter, remove the activated carbon inside, and check whether the wire mesh at the bottom of the activated carbon is damaged. If it is damaged, replace it with a new stainless steel wire mesh, and then install it. Return to activated carbon to operate normally. When filling activated carbon, try to fill the filter as much as possible to prevent the activated carbon from colliding with each other under the action of airflow to generate dust. If molecular sieve is sprayed out, it will be more troublesome to handle, and the equipment needs to be transported back to the factory for overhaul.