Optimization of CO2 Absorption Characteristic under the Influence of SO2 in Flue Gas by Hollow Fiber Membrane Contactor

Hollow fiber membrane contactor is a new, highly efficient, and the most promising technology for CO2 absorption in flue gas. There is still SO2 that exists in the flue gas after desulfurization tower of power plant. This paper studied the influence of SO2 on CO2 absorption characteristic in flue gas by hollow fiber membrane contactor with absorbent of EDA, EDA +MEA (0.6 : 0.4), and EDA +MEA + PZ (0.4 : 0.4 : 0.2).The influences of SO2 concentration, cycle absorption and desorption characteristic of absorbent, absorbent concentration, and liquid-gas flow rate ratio are studied to analyze the influence of SO2 onCO2 absorption characteristic. The appropriate absorbent composition ratio and appropriate parameter range that can inhibit the influence of SO2 are proposed by studying the hybrid sorbent with activating agent, appropriate absorbent concentration, and ratio of liquid-gas flow rate. Among the three kinds of absorbents, EDA +MEA + PZ (0.4 : 0.4 : 0.2) had the best tolerance ability to SO2 and the highest efficiency.With comprehensive consideration of CO2 removal efficiency and operating cost, under the condition of 1000 ppm SO2, the appropriate concentration and liquid-gas flow rate ratio of EDA, EDA + MEA, and EDA + MEA + PZ are proposed.


Introduction
In recent years, energy consumption has been increasing with the rapid growth of the world economy.The greenhouse effect of CO 2 became increasingly serious, and hence energy conservation is urgent [1].The hollow fiber membrane contactor is a new technology for the CO 2 absorption process [2].The membrane does not participate in the reaction, which isolates gas and liquid.In a hollow fiber membrane contactor, the absorbent flows in one side while the flue gas flows in the other side.The flue gas diffuses through the gas-liquid interface initially, and then CO 2 reacts with the absorbent.Because of the CO 2 concentration gradient in the gas and liquid phases, CO 2 transfers from the gas phase to liquid phases through the membrane pores and continues to react with the absorbent.Because of the high reaction rate, simple operation, small volume membrane absorption technology, and low cost, the hollow fiber membrane contactor is one of the most promising decarburization technologies.
The alcohol amine absorbent used in CO 2 absorption has been used in SO 2 removal by many researchers [3][4][5][6][7][8].The hollow fiber membrane contactor is not only applied for CO 2 removal, but also applied to remove SO 2 .Ogundiran et al. [9] studied SO 2 capture in flue gas by porous hydrophobic hollow fibers and found that it was a more promising technology than conventional scrubbers used in desulfurization.Park et al. [10] studied the effects of operation parameters on SO 2 removal by PVDF hollow fiber membranes and found that it is one of the most competitive alternatives in the future.There is still SO 2 that exists in the flue gas after desulfurization tower.The influence of SO 2 on CO 2 capture gained more attention recently.Zhong [11] studied the effect of SO 2 concentration on MEA, MEA/MDEA, MEDA/PZ, and DEA/AMP.The tolerance of SO 2 was found to be as follows: MEA > DEA/AMP > MEDA/PZ > MEA/MDEA.Uyanga and Idem [12] studied the degradation of MEA caused by SO 2 in a semibatch reactor.The results show that SO 2 accelerates the rate of MEA degradation and established a dynamic model.Supap et al. [13] studied the kinetics of SO 2− and O 2− induced degradation of aqueous MEA during CO 2 capture.The results show that an increase in temperature and concentration of MEA, O 2 , and SO 2 causes a higher degradation rate of MEA.Gao et al. [14] studied the effect of SO 2 on the CO 2 capture process in a pilot plant.The results show that SO 2 causes amine oxidative degradation, which is beneficial to remove SO 2 induced heat stable salts using appropriate methods.Bonenfant et al. [15] studied the absorption of CO 2 and SO 2 mixtures with the absorbent of aqueous 2-(2-aminoethylamino)ethanol (AEE) solution and its blends with N-methyldiethanolamine (MDEA) and triethanolamine (TEA) to estimate the influence of SO 2 .The results show that SO 2 decreases the CO 2 absorption rate.The addition of 5 and 10 wt.% of MDEA and TEA does not influence the CO 2 absorption rate in AEE.TEA decreases the absorption capacity of AEE.Yang et al. [16] studied the influence of SO 2 on the CO 2 capture in an absorptiondesorption experimental setup using MEA as the absorbent.The results show that there were sharp decreases in CO 2 removal efficiency and mass transfer rate of CO 2 after the initial several days of operation; more progress is needed in high-efficiency and stable absorbents.
According to the present research situation, SO 2 causes the degradation of alcohol amine absorbent, resulting in the decrease of CO 2 removal efficiency.The influence of SO 2 on CO 2 absorption by alcohol amine absorbent deserves attention.It is necessary to research the optimization of CO 2 absorption characteristic under the influence of SO 2 .Research on appropriate absorbent and parameter range which can inhibit the influence of SO 2 is needed.MEA, MDEA, DEA, and other amine solutions [11][12][13][14][15][16] are selected as absorbent of CO 2 capture by many researchers.The disadvantage of MEA is the high energy consumption in the CO 2 desorption.The tolerance ability to SO 2 of MEA is better than that of MDEA [11].Studies on EDA as an absorbent used in CO 2 capture are relatively fewer.In the study of Shunxiang [18], the performance of the absorbents used in CO 2 absorption is as follows: PZ > EDA > MEA > DEA.Considering that CO 2 removal efficiency of EDA is higher than of MEA, the tolerance ability to SO 2 of MEA is high and the activation ability of PZ is good, and EDA, EDA + MEA, and EDA + MEA + PZ are selected as absorbents of CO 2 capture in this paper.This paper researches the performance of these absorbents under the influence of SO 2 in order to study the appropriate absorbent composition ratio and specific operating parameters to optimize CO 2 absorption under the influence of SO 2 .The results of this study are an important reference for the industrial application of CO 2 absorption by hollow fiber membrane contactor.

Materials and Methods
2.1.Reaction Mechanism.SO 2 diffuses from gas phase to gas-liquid interface firstly and then diffuses from gas-liquid interface to liquid phase and dissolves in liquid.The reaction between SO 2 and amine solution can be assumed as a combination of the physical dissolution of SO 2 in water and the chemical absorption of amine solution.SO 2 in water generates SO 3 2− firstly [11,19]: The solubility of SO 2 increased by the addition of amine solution, and the amine reacted with the hydrogen ion from the water and formed a compound of strong heat stability: With oxygen: The compound generated in formula ( 3) is stable and cannot be regenerated by heating, which results in degradation and depletion of the amine solution.In addition to this, it will cause solution foaming and decrease CO 2 removal efficiency in the system in the long run.
For MEA, the reaction between CO 2 and MEA is as follows [20][21][22]: The reaction between SO 2 and MEA is as follows [19]: where R is HOCH 2 CH 2 .1.The membrane is designed by internal pressure and stretch forming.The inlet and outlet of the gas and liquid are arranged on the side and the end, respectively.The maximum pressure designed is 0.3 MPa, applicable to the pH of 1∼14, at 15∼40 ∘ C.

Experimental Procedures.
The system is shown in Figure 1.The flue gas is simulated by mixed gas of CO 2 , SO 2 , and N 2 .The flue gas is introduced into fiber membrane contactor from compressed gas cylinders.The absorbent is introduced into the contactor by a pump.The gas flows in the tube side and the absorbent flows in the shell side.There are regulating valves at the outlet of the simulative flue gas  and absorbent pump which can control the flow rate of gas and absorbent.The absorbent reacts with CO 2 and becomes a rich liquid and is then introduced into the absorbent tank by a pump.The desorption tank desorbs CO 2 by heating the rich liquid.This is one cycle of absorption and desorption.The desorption tank is designed by electric heating.There are sample portions to analyze the gas component by a gas analyzer (ECOM-J2KN, German RBR Company) and gas chromatograph (GC7900, Shanghai Tianmei Scientific Instruments Co., Ltd.).Values are obtained when the reaction is stable for 5 min, and then an average value of three times is obtained, each time interval of 30 s.The experimental conditions and parameters are shown in Table 2. Gas flow rate is 4 m 3 /h, and absorbent flow rate is 0.7 m 3 /h.Volume fraction of CO 2 in gas is 14 vol.%.

Results and Discussion
The CO 2 removal efficiency is the parameter that reflects the CO 2 removal performance; it can be calculated by [23] where  is the CO 2 removal efficiency,  in is the gas flow rate of inlet,  out is the gas flow rate of outlet, and  in and  out are the volume fraction of CO 2 at inlet and outlet, respectively.The mass transfer rate reflects the performance of mass transfer.It can be calculated by [23] where  CO 2 is the mass transfer rate,   is gas temperature, and S is the total area of the membrane.removal efficiency and mass transfer rate are shown in Figures 2 and 3.The CO 2 removal efficiency and mass transfer rate of the three absorbents decrease with the increasing of SO 2 concentration.The solubility of SO 2 is much higher than of CO 2 .The pH value of SO 2 aqueous solution is smaller than the pH value of CO 2 equilibrium solution.The reaction between SO 2 and amine absorbent can be considered as instantaneous [11].The reaction rates and opportunities for SO 2 and absorbent are much higher than those of CO 2 and absorbent, which leads to the decrease of CO 2 removal efficiency.

Influence of SO
The CO 2 removal efficiency of three absorbents decreased suddenly after 1000 ppm SO 2 .The effective components keep constant when the absorbent concentration is fixed.When SO 2 concentration increased to a certain value, the effective components of absorbent are consumed largely by SO 2 , which leads to the sudden decrease of CO 2 removal efficiency.The CO 2 removal efficiency of EDA decreases by 4.05% with 500 ppm SO 2 and decreases by 37.3% with 2000 ppm SO 2 .It can be considered that the influence of SO 2 on CO 2 removal efficiency with EDA is not significant when the SO 2 concentration is under 500 ppm.Because of the low concentration of SO 2 , even with the faster reaction rate of SO 2 , there is still a chance for CO 2 to react with the absorbent.The concentration gradient of the gas and the liquid vapor interface increases with increasing SO 2 concentration, which improves the mass transfer dynamics.This is favorable for SO 2 molecules to diffuse to the surface and the interior of the absorption solution and speed up the reaction of SO 2 with EDA.Therefore, the absorption of CO 2 reduced greatly with the increasing of SO 2 concentration.The influence of SO 2 on CO 2 removal efficiency is more significant with the increase of SO 2 concentration.The SO 2 concentration in the outlet of flue gas is always zero, which indicates that SO 2 is absorbed by the absorbent completely, and the reaction rate of SO 2 and the absorbent is significantly higher than that of CO 2 and the absorbent.
The CO 2 removal efficiency of EDA + MEA decreases by 2.1% with 500 ppm SO 2 , the efficiency is 53.1% with 1000 ppm SO 2 , and the efficiency decreases to 29.3% with 2000 ppm SO 2 .Comparing the results of EDA + MEA (0.6 : 0.4) and EDA, the CO 2 removal efficiency and mass transfer rate of EDA are higher than those of EDA + MEA without the addition of SO 2 .With the increasing of SO 2 concentration, the CO 2 removal efficiency and mass transfer rate of EDA + MEA (0.6 : 0.4) are higher than those of EDA.The CO 2 absorption capacity of EDA is better than that of MEA [18]; therefore, the CO 2 removal efficiency and mass transfer rate of EDA are higher than those of EDA + MEA (0.6 : 0.4) without the influence of SO 2 .The active ingredient increases after the addition of MEA, which promotes the tolerance ability of the absorbent to SO 2 .The CO 2 removal efficiency and mass transfer rate reduction of EDA + MEA (0.6 : 0.4) are smaller than those of EDA; therefore, the tolerance ability of EDA + MEA (0.6 : 0.4) to SO 2 is better than that of EDA.
Zhong [11] researched the influence of SO 2 concentration on CO 2 absorption with the absorbent of 10% MEA and 10% MEA + 2% MDEA (liquid flow rate 18 L/h, temperature 40 ∘ C; flue gas flow rate 1800 L/h, temperature 15 ∘ C; SO 2 concentration is 500-1500 ppm).The results are shown in Figure 2. The results indicate that the CO 2 removal efficiency decreases with the increase of SO 2 concentration, and the influence of SO 2 is not significant till the SO 2 concentration becomes greater than 500 ppm, which agrees well with the results in this paper.The CO 2 removal efficiency of 10% MEA + 2% MDEA is higher than that of 10% MEA when SO 2 concentration is under 117 ppm, and the decrease extent of CO 2 removal efficiency in 10% MEA + 2% MDEA is more than that in 10% MEA with the increase of SO 2 concentration.The CO 2 removal efficiency of 10% MEA is higher than that of 10% MEA + 2% MDEA with 200 ppm SO 2 .This indicates that the reaction between 10% MEA + 2% MDEA and SO 2  is more rapid and intense, so the decrease extent of CO 2 removal efficiency with the absorbent of 10% MEA + 2% MDEA is more significant than of 10% MEA.Because of the poor absorptive capacity and slow absorption rate of MDEA, MDEA is not suitable for CO 2 absorption with the influence of SO 2 .The tolerance ability of 10% MEA + 2% MDEA to SO 2 is lower than that of 10% MEA.
Comparing the results of EDA and 10% MEA, the CO 2 removal efficiency of 10% MEA is higher than of EDA without SO 2 , and the decrease extent is smaller than EDA with the increase of SO 2 concentration.So, the tolerance ability to SO 2 of 10% MEA is greater than 500 mol/m 3 EDA.After adding of MEA, the CO 2 removal efficiency of EDA + MEA (0.6 : 0.4) is higher than of EDA with the increase of SO 2 concentration.So, the hybrid absorbent of EDA + MEA (0.6 : 0.4) is appropriate for removal of CO 2 in the flue gas containing SO 2 .
The absorbent of EDA + MEA + PZ is the most efficient in the three absorbents.The CO 2 removal efficiency of EDA + MEA + PZ decreases by 1.2% with 500 ppm SO 2 , decreases by 3.4% with 800 ppm SO 2 , and decreases by 27.1% with 2000 ppm SO 2 .The CO 2 removal efficiency reduction of EDA + MEA + PZ is not significant until 1000 ppm SO 2 .Because of the activity of PZ, the influence of SO 2 on CO 2 absorption with EDA + MEA + PZ is not significant under the condition of low SO 2 concentration in a short time.And the tolerance ability of EDA + MEA + PZ to SO 2 is greater than that of EDA and EDA + MEA.The influence of SO 2 is getting more significant when the PZ active effect is gradually consumed.Therefore, the CO 2 removal efficiency decreases significantly with 2000 ppm SO 2 .
The results of the three absorbents indicate that the influence of SO 2 on CO 2 is not significant with low SO 2   concentration in the short run performance; the hybrid absorbent with high absorptive capacity component and high tolerance ability to SO 2 can inhibit the influence of SO 2 on CO 2 absorption effectively.

Cycle Absorption and Desorption Characteristic of
Absorbent.According to the previous research, the influence of SO 2 on CO 2 absorption is not significant in the low concentration of SO 2 .The absorption experiment is conducted in a short time, and the cycle absorption and desorption of the absorbent are not considered.It is necessary to study the cycle absorption and desorption of the absorbent.Based on the influence of SO 2 concentration on CO 2 removal efficiency, the influence is not significant when the SO 2 concentration is below 500 ppm of the three absorbents.In order to study the influence of SO 2 on CO 2 absorption in low SO 2 concentration, the SO 2 concentration of 500 ppm is selected in this experiment.
The results are shown in Figures 4 and 5.The absorbent from absorption to desorption is one cycle.The CO 2 removal efficiency and mass transfer rate decrease with the increase of cycle number.The CO 2 removal efficiency of EDA decreases by 26.85% with SO 2 and decreases by 21.8% without SO 2 ; the CO 2 removal efficiency of EDA + MEA decreases by 24.7% with SO 2 and decreases by 22.1% without SO 2 ; the CO 2 removal efficiency of EDA + MEA + PZ decreases by 14.6% with the influence of SO 2 .
Desorption of the absorbent by heating the rich liquid results in absorbent degradation.SO 2 reacts with the absorbent and generates stable salts, which cannot be regenerated by heating.The existence of SO 2 accelerates the degradation of most amine solutions.Strazisar et al. [24] studied the effect of SO 2 on the degradation of MEA.The results show that SO 2 accelerates the degradation rate of MEA, which is significant in higher concentration of SO 2 .Therefore, the CO 2 removal efficiency and mass transfer rate decrease significantly with the increasing cycle of absorption and desorption.
Gao et al. [17] studied the influence of SO 2 on the absorption character of absorbent in the following campaign: no SO 2 , 214 ppm SO 2 , and 317 ppm SO 2 , respectively.The result is shown in Figure 6.The CO 2 removal efficiency decreases gradually with increasing circulating time.And the decrease extent of CO 2 removal efficiency increases with SO 2 concentration.The absorbent degradation and heat stable salts formation are the main reasons for the significant influence of SO 2 .The trend of Figure 4 in this experiment agreed with the trend of Figure 6.
The study in this section indicated that there is a significant influence of SO 2 on CO 2 absorption even in low SO 2 concentration in the long run performance.The order of tolerance ability to SO 2 is EDA + MEA + PZ (0.4 : 0.4 : 0.2) > EDA + MEA (0.6 : 0.4) > EDA.The CO 2 removal efficiency of EDA + MEA + PZ (0.4 : 0.4 : 0.2) decreased to 60% after ten absorption and desorption cycles.Therefore, it is necessary to study the appropriate parameter range in the operation to inhibit the influence of SO 2 .

The Influence of Absorbent Concentration on CO 2 Absorption.
The concentration of absorbent is one of the most important parameters of CO 2 absorption in operation.The influence of absorbent concentration on CO 2 removal efficiency is studied in this section for confirming the appropriate concentration of the absorbent which can inhibit the influence of SO 2 .
The CO 2 removal efficiency of the three absorbents decreased suddenly after 1000 ppm SO 2 in the study of influence of SO 2 concentration.Therefore, the experiment is  ) ) ) ) ) )  ) ) ) ) ) ) conducted under the condition of 1000 ppm SO 2 .The concentration of the absorbent is from 400 mol/m 3 to 800 mol/m 3 .The CO 2 removal efficiency and mass transfer rate increase with the increasing absorbent concentration which is shown in Figures 7 and 8. Comparing the result of 1000 ppm SO 2 with that of no SO 2 , the CO 2 removal efficiency of 400 mol/m 3 EDA, 600 mol/m 3 EDA, and 650 mol/m 3 EDA decreases by 13.27%, 6.5%, and 5.3%, respectively.The decreasing extent of CO 2 removal efficiency and mass transfer rate of absorbent reduce with the increasing absorbent concentration.
A certain amount of absorbent is needed when the concentration of SO 2 keeps constant in flue gas.There are more active ingredients in the absorbent to improve the CO 2 absorption with the increase of absorbent concentration.Therefore, increasing absorbent concentration can inhibit the influence of SO 2 on CO 2 absorption.The cost and the energy consumption increase with the increasing absorbent concentration.Hence, there is an appropriate concentration of absorbent which can inhibit the influence of SO 2 on CO 2 absorption with low cost and low energy consumption.The CO 2 removal efficiency of 800 mol/m 3 EDA, 750 mol/m 3 EDA + MEA, and 650 mol/m 3 EDA + MEA + PZ is 75%, 74%, and 83%, respectively, with 1000 ppm SO 2 .Continuing to increase the absorbent concentration, the increment of CO 2 removal efficiency will reduce because the absorbent viscosity and the mass transfer resistance increase with the increasing absorbent concentration.Furthermore, continuing to increase the absorbent concentration will increase investment and operating costs.Considering the above factors, under the condition of 1000 ppm SO 2 , the appropriate concentrations of EDA, EDA + MEA, and EDA + MEA + PZ are 800 mol/m 3 , 750 mol/m 3 , and 650 mol/m 3 , respectively.

Influence of the Liquid-Gas Flow Rate Ratio on CO 2
Absorption.The flow rates of absorbent and gas are important parameters which can affect the CO 2 absorption significantly.It is necessary to study the appropriate ratio of liquidgas flow rate for inhibiting the influence of SO 2 .
With the increasing ratio of liquid-gas flow rate under the condition of 1000 ppm SO 2 , the CO 2 absorption characteristic of EDA, EDA + MEA, and EDA + MEA + PZ is shown in Figures 9 and 10.The CO 2 removal efficiency and mass transfer rate rise with the increasing ratio of liquid-gas flow rate.With the addition of SO 2 , the CO 2 removal efficiency of EDA decreases by 7.9%, 6.28%, and 5.26%, respectively, when the ratio of liquid-gas flow rate is 0.1, 0.15, and 0.25 individually.The CO 2 removal efficiency difference between the case with SO 2 and that without SO 2 decreases with the increasing ratio of liquid-gas flow rate.The experimental results of EDA + MEA and EDA + MEA + PZ are similar to that of EDA.Therefore, the influence of SO 2 on CO 2 absorption decreases with the increasing ratio of liquid-gas flow rate.Lv et al. [25] studied the simultaneous removal of CO 2 and SO 2 in a polypropylene hollow fiber membrane contactor using MEA.The CO 2 removal efficiency of MEA with 1600 ppm increased with the liquid flow rate.The experimental result in this section of this paper agrees with the result of Lv et al.
With a certain concentration of SO 2 , the reaction of absorbent with CO 2 increases gradually with the increasing ratio of liquid-gas flow rate.The mass transfer rate increases with the ratio of liquid-gas flow rate under a certain gas condition.Because of the increment of concentration gradients,  ) ) ) ) ) ) the mass transfer and the reaction of absorbent and CO 2 are improved.The increase of absorbent flow rate accelerates the membrane wetting and wear, which result in a mass transfer resistance increase.Therefore, the increments of CO 2 removal efficiency and mass transfer rate reduce with the increasing ratio of liquid-gas flow rate.Meanwhile, the consumption of absorbent and pump increases with the increasing liquidgas flow rate ratio, which raises the operation cost.In the liquid-gas flow rate ratio of 0.2-0.25, the lowest CO 2 removal efficiencies of EDA, EDA + MEA, and EDA + MEA + PZ are 60%, 63%, and 77%, respectively; the highest CO 2 removal efficiencies of EDA, EDA + MEA, and EDA + MEA + PZ are 67%, 70%, and 92%, respectively.In order to inhibit the influence of SO 2 on CO 2 absorption and maintain high CO 2 removal efficiency and low operating cost, under the condition of 1000 ppm SO 2 , the appropriate liquid-gas flow rate ratio of EDA, EDA + MEA, and EDA + MEA + PZ is from 0.2 to 0.25.

Conclusions
There is a significant influence of SO 2 on CO 2 absorption in the long run performance, which affects the industrial application prospects of this technology.It is necessary to study the SO 2 influence characteristic on CO 2 absorption and the measure to optimize the CO 2 absorption under the influence of SO 2 .
This paper studied the optimization of CO 2 absorption characteristic under the influence of SO 2 with the absorbent of EDA, EDA + MEA, and EDA + MEA + PZ by hollow fiber membrane contactor.The SO 2 concentration, cycle absorption and desorption characteristic of absorbent, absorbent concentration, and ratio of liquid-gas flow rate are analyzed to evaluate the influence of SO 2 on CO 2 absorption characteristic.The reaction rate and absorption performance of SO 2 with amine solution are much greater than those of CO 2 with amine solution, resulting in decreases of CO 2 removal efficiency and mass transfer rate in different extent with the absorbent of EDA, EDA + MEA, and EDA + MEA + PZ.The CO 2 removal efficiency and mass transfer rate decrease with the increasing SO 2 concentration and absorption and desorption cycle of absorbent.
This paper proposes appropriate absorbent composition ratio and operation parameters range which can inhibit the influence of SO 2 on CO 2 absorption and optimize the CO 2 absorption under the influence of SO 2 .Depending on the results in this research, hybrid absorbent with activator agent, appropriate absorbent concentration, and ratio of liquid-gas flow rate can inhibit the influence of SO 2 on CO 2 absorption effectively.EDA + MEA + PZ (0.4 : 0.4 : 0.2) has the best tolerance ability to SO 2 among the three absorbents.Under the condition of 1000 ppm SO 2 in flue gas, the appropriate absorbent concentrations of EDA, EDA + MEA, and EDA + MEA + PZ are 800 mol/m 3 , 750 mol/m 3 , and 650 mol/m 3 , respectively, and the appropriate ratio of liquid-gas flow rate is in the range from 0.2 to 0.25.

Figure 1 :
Figure 1: Flow chart of the experiment using the flue gas.

Figure 5 :
Figure 5: Influence of cycle absorption and desorption on the CO 2 mass transfer rate (  = 4 m 3 /h, U l = 0.7 m 3 /h, and T = 288 K).

Figure 7 :
Figure 7: Influence of SO 2 on the CO 2 removal efficiency in different concentrations of absorbent (  = 4 m 3 /h, U l = 0.7 m 3 /h, and T = 288 K).

Figure 8 :
Figure 8: Influence of SO 2 on the CO 2 mass transfer rate in different concentrations of absorbent (  = 4 m 3 /h, U l = 0.7 m 3 /h, and T = 288 K).

Figure 10 :
Figure 10: Influence of SO 2 on the CO 2 mass transfer rate in different liquid-gas flow rate ratios (T = 288 K).

Table 1 :
Specifications and parameters of PP hollow fiber membrane contactor.

Table 2 :
Parameters of operating conditions.
2Concentration on CO 2 Absorption.In order to emphasize the influence of SO 2 concentration, the concentration of SO 2 is amplified from 500 ppm to 2000 ppm in this research.The influences of SO 2 concentration on CO 2 Influence of SO 2 on the CO 2 mass transfer rate in different liquid-gas flow rate ratios (T = 288 K).