Summary of lithium molecular sieves for oxygen production
CG-LiPO2 lithium molecular sieve is the basis of pressure swing adsorption for oxygen production. The equilibrium adsorption capacity and separation coefficient of high-efficiency lithium oxygen molecular sieve are about 2 times that of traditional oxygen rich adsorbents (see Table 1), and the adsorption rate is much higher than that of traditional oxygen rich adsorbents.
Table 1 Comparison of lithium molecular sieve and sodium molecular sieve
Item
CG-LiPO2
CG-XPO2
5APSA
Diameter mm
1.3-1.8
0.4-0.8
1 .6-2.5
0.4-0.8
1 .6-2.5
Adsorption capacity of N2 ml/g
23
23
8.5
8.5
10
N2/O2 selection
6.30
6.30
3.1
3.1
3.0
Crushing strength N/P
30
-
40
-
30
Gas production NL/ Kg·h
75-85
35-45
35-45
Bulk density g/ml
0.63
0.63
0.63
0.63
0.74
The oxygen production device has high requirements for stabilizing and improving the economic and technical indicators of the oxygen production device. The core of pressure swing adsorption oxygen production is molecular sieve. It is very important to master the characteristics of different molecular sieve to improve the efficiency of pressure swing adsorption oxygen production device and reduce energy consumption.
The application of lithium molecular sieve in PSA device
1. Adsorption pressure and yield High adsorption pressure, although it can increase the adsorption speed of molecular sieve, but in the case of high relative pressure for endothermic desorption, desorption tower temperature reduction, adsorption balance will become very slow, absorbent utilization rate decreased significantly. Therefore, the adsorption pressure cannot be too high, and the difference between the adsorption pressure and the desorption pressure should be as low as possible. The adsorption performance of lithium molecular sieve under the condition of low partial pressure is very good (see Table 3), which makes it possible to use high vacuum desorption, low adsorption pressure process to reduce the pressure difference, improve he utilization rate of adsorbent, and improve the yield. After the test, the operation process of -70KPa desorption pressure and 40KPa adsorption
pressure is adopted on the oxygen producing device. The utilization rate of the adsorbent is very high, and the energy consumption can be controlled at 0.35Nm3 /KW ·h.
Table 2 Technical indexes of lithium molecular sieve under different adsorption pressures
Adsorption pressure（KPa）
Adsorption pressure（KPa）
93% oxygen productivity（NL/kg· h）
-50
25
86
30
95
35
100
-55
24
95
27
98
30
101
40
125
50
144
-60
24
113
27
113
30
122
35
128
40
135
45
139
50
158
-65
25
120
30
137
35
139
40
149
45
153
-70
24
133
27
140
30
144
35
158
40
160
45
170
Temperature and yield
Our company's lithium molecular sieve in Mike adsorption instrument for different temperature N2 equilibrium adsorption capacity test, and foreign products in the same equipment with the same test conditions measured data comparison, as shown in the following.
Table 3:Technical indexes of lithium molecular sieve under different adsorption temperature.
Temp.
15℃
20℃
25℃
30℃
Competitor 01（ml/g）
25.62
26.21
23.57
21 .69
Competitor 02（ml/g）
27.86
27.55
25.55
22.99
CG-LiPO2（ml/g）
26.21
26.02
24.07
21.42
Different lithium molecular sieve adsorbents have different sensitivity to temperature, and the adsorption capacity of lithium molecular sieve decreases with the increase of adsorption temperature. As the temperature increases, the adsorption rate and desorption rate increase, however, the adsorption capacity decreases with the increase of temperature, if the adsorption cycle is unchanged, the adsorption bed of the adsorption mass flow rate relative to 25℃ attenuation, will appear in the adsorption cycle
of the adsorption mass penetration phenomenon, thereby reducing the product purity.
Results
Lithium molecular sieve promoted the rapid development of pressure swing adsorption oxygen production, improved oxygen production rate and reduced energy consumption.
The influence of adsorption pressure and temperature should be considered when using lithium molecular sieve. Through experiments, the characteristics of high adsorption capacity and high separation coefficient of lithium molecular sieve can be fully played, and the yield of oxygen production by pressure swing adsorption can be greatly improved and energy consumption can be reduced.
The CG-LiPO2 lithium molecular sieve produced by our company has good adsorption performance and high separation coefficient, and the comprehensive performance of the product has reached the international advanced level.
