“heat of compression" and "zero air consumption"

What is "Heat of Compression"

1. Compression heat dryer means that the heat source in the heating regeneration process mainly comes from the heat generated by the final stage of the air compressor during the compression process, that is, the desorption tower is heated and regenerated by using superheated compressed air with a higher temperature. The temperature is about 90~110°C, the lowest is 80°C, and the highest is 180°C. Of course, the air compressor must be an oil-free machine. In the industry, it is mainly a centrifugal type and an oil-free screw. The former belongs to medium and large displacement, which is suitable for occasions with relatively stable working conditions. big change.

2. The exhaust temperature has a great influence on the compression heat dryer. Medium and large centrifuges are generally three-stage compressors, and the exhaust temperature is mostly 90~110 ° C. Small centrifuges and oil-free screws are generally two-pole compression, and the exhaust temperature is more 150~170℃.

3. The biggest advantage of compression heat regeneration is that the heat is abundant, and its full flow passes through the analysis tower, while other types with heat regeneration are 15%~25%, so at the same regeneration temperature, the heat contained in the heat of compression is 4~4% of other types. 6 times, this alone shows the huge energy saving significance of compression heat utilization.

4. The biggest weakness of compression heat regeneration is the low grade. Compared with other heating regeneration, the temperature is as high as 180~220℃, and the exhaust temperature of the centrifuge is far from that. The two-stage compression, such as oil-free screw, can reach above 150°C during stable operation, but due to frequent unloading or unloading, in addition to the proportional reduction of the amount of heat contained, the exhaust temperature also drops, so in order to obtain a lower and stable dew point index , Corresponding to whether it is a three-stage compression centrifuge or a two-stage compression oil-free screw, the auxiliary regeneration system (TSA/PSA) has almost become a must.

According to experience: every time the adsorption temperature (P0) drops by 10°C, the dew point can drop by 10°C; every 10°C increase in the heating temperature (P2), the dew point can drop by 4-5°C. Use dry gas (P1) for regeneration, especially dry gas. The effect of blow cooling on the instant dew point and adsorbent life is too great to ignore.

5. To sum up, the advantages and disadvantages of compression heat regeneration coexist. The core technology is not whether to use compression heat, but how to make good use of the auxiliary regeneration system. Specifically, how to obtain low dew point, zero air consumption, low cost and low cost at the same time. running costs.

What is "zero gas consumption"

1. Zero gas consumption (also known as zero discharge in process gas) is a large category in various compressed air/gas dryer processes, which means that the product dry gas at the outlet of the dryer does not need to be consumed during the regeneration of the adsorbent.

2. The compressed air adsorption dryer has stepped into the era of thermal regeneration, that is, temperature swing adsorption/regeneration (TSA), and has accelerated the pace of "zero air consumption" in the past ten years. Heaters are usually divided into two categories: blast heating and compression heat, which are classified as follows according to product gas consumption:

3. Why pursue "zero gas consumption"? In short, it is to reduce the use of expensive compressed air energy as much as possible, and to follow the conservation law in the process of energy conversion, but the conversion of energy into another energy is efficient. Generally speaking, the heat/electricity conversion efficiency It is about 45%, and the electricity/gas conversion is converted from electricity to compression energy that can do expansion work, and the efficiency is less than 30%, (see the figure below):

Assume the efficiency of the power plant is 45%

Then the power plant needs to consume 100kW/45% of basic energy = 222kW

The available energy is only 23.4kW/222kW = 10.5% of the basic energy

Some people think that the consumption of part of the product gas can be converted into electricity in equal proportions, and then into standard coal in equal proportions. This concept is wrong. The mistake is to equate the calorific value conversion relationship with the value conversion relationship, and equate the energy conservation and environmental protection indicators with the economic benefit and operating cost indicators. For example, on the calorific value relationship:

0.123kg standard coal=1kw.h

1kg standard coal=8.137kw.h

0.123kg standard coal=0.040m3 (compressed air)

1kg standard coal=25m3

According to 1kg standard coal 1.0 yuan, 1KW.h is 0.75 yuan, 1m3 compressed air is 0.15 yuan, then 0.75 yuan × 8.137 = 6.1 yuan, which is more than 6 times the standard coal price; 0.15 yuan × 25 = 3.75 yuan, which is standard coal 3.75 times the price;

For a powered air compressor, 1kw.h can generate 10m3 of compressed air, and there is a relationship between 0.75 yuan and 1.5 yuan, that is, the electricity cost only accounts for about 50% of the cost of oil-free dry compressed air. Equating high-grade energy with low-grade energy shows that the compressed air is not equivalent, which can be briefly described as gas/electricity inequivalence.

4. Conclusion: As the regenerative energy of the adsorption dryer, if you can use electricity, you should not use gas, if you can use heat, you should not use electricity. If you can use the residual heat in the compressed air system, it is the highest level.

FROM:compressor technology