265168 Development of PSA System for the Recovery of Carbon Dioxide and Carbon Monoxide From Blast Furnace Gas in Steel Works

Tuesday, October 30, 2012: 3:33 PM
405 (Convention Center )
Hitoshi Saima1, Yasuhiro Mogi1 and Takashi Haraoka2, (1)Steel Research Labs., JFE Steel Corp., Fukuyama, Hiroshima, Japan, (2)Steel Research Labs., JFE Steel Corp., Kawasaki, Kanagawa

Development of PSA System for the Recovery of Carbon Dioxide and Carbon

Monoxide from Blast Furnace Gas in Steel Works

H.Saima, Y. Mogi, T. Haraoka,

Environmental Process Research Department, Steel Research Laboratory, JFE Steel Corp,

Climate exchange by carbon dioxide became the serious and global problem.  In Japan, steel works discharge carbon dioxide about 15% of total discharging amount.  From this point of view, The Japan Iron and Steel Federation (JISF) starts a new project, called  "COURSE 50" (CO2 Ultimate Reduction in Steelmaking process by innovative technology for cool Earth 50).  The authors are trying to develop separation and recovery technology of carbon dioxide and carbon monoxide from Blast furnace gas by utilizing PSA technology.

This trial seemed to be easy by binding PSA for carbon dioxide and one for carbon monoxide.  However, the amount of Blast furnace gas is enormous, such as more than several million m3/hr and the concentrations of both carbon dioxide and monoxide are only around 20%.  Furthermore, it is necessary to built up low cost process for the commercialization.

At first the authors compared 13 kinds of adsorbent from the market by isothermal curve and choose 2 kinds of adsorbent.  These adsorbents are tested by PSA testing apparatus in the laboratory.  The inner diameter of adsorption tower in testing apparatus is 43mm and the height of it is 500mm long.  We found Zeolum F-9 was suitable for carbon dioxide separation because of high adsorption capacity and adsorption selectivity.

From the importance of recovery cost for the commercialization, the authors estimated the recovery it at laboratory PSA apparatus, which was shown in photo 1, in the various separation conditions.  Higher adsorption pressure leads higher recovery ratio although it also leads higher power consumption at blower.  Simultaneously, lower desorption pressure leads higher recovery ratio and higher power consumption at vacuum pump. As the results of experiment and power estimation at blower and vacuum pump, it is suitable that adsorption pressure is around 150-200kPa (absolute pressure) and desorption pressure is around 10kPa (absolute pressure).  Furthermore, cycle time is key factor of cost for construction.  The authors thought the standard cycle time was 630 seconds.  As the results of laboratory PSA apparatus, which was shown in Figure 1, any change in separation ability was recognized among the results of cycle time at 450, 630 and 720 seconds.  And slight change was observed in the results of cycle time at 300 seconds.  The effects of CO2 concentration in raw gas were also tested.  Higher CO2 concentration leads higher CO2 recovery ratio. As shown in Figure 2, when CO2 concentration is 32% in raw gas, CO2 recovery ratio rises up to 1.6 times higher than one in original CO2 concentration even the ratio in CO2 concentration in raw is only around 1.4.  This change is important because CO2 concentration in blast furnace gas is thought to be increased in the future development.  Injection of hydrogen to blast furnace is studied in the same project.  If hydrogen is injected, CO2 in the blast furnace gas will be increased because of operation conditions of blast furnace.  By these results, recovery cost estimated to be 63% of original cost suggested.

Base on these results, bench scale PSA plant called "ASCOA-3" (Advanced Separation system by Carbon Oxides Adsorption) was constructed as shown in Photo 2.  The planned capacity of ASCOA-3 is 3 tons of CO2 per day.  The inner diameter and height of adsorption tower are 0.6m and 1.2m, respectively.  Figure 3 shows the flow diagram of ASCOA-3.  The actual blast furnace gas is compressed up to 300kPa, cools to 10 degree centigrade and removes water and sulfur compounds by adsorption with silica-alumina gel and activated carbon before feeding to PSA unit.  At the first operation called RUN100, ASCOA-3 shows its enough ability.  CO2 recovery rises up to 4.2tons per day and CO2 recovery ratio and purity exceeds the target.  At the second and third operation called RUN 200 and 300, various operation conditions were tested and actual power consumption was measured in these operations.  Especially in RUN 300, CO2 recovery rises up to 6.2 tons per day with shorter cycle time (225 seconds) and high CO2 concentration in blest furnace gas (34%) even at low adsorption pressure (150kPa).  From these results, recovery cost (63% of original one), which is suggested in laboratory PSA apparatus, is confirmed.  And further operation called RUN 400 is now started to reduce cost to the target (50%).

Furthermore, 9 thermocouples were installed in a adsorption tower.  They can measure the temperature of center, half radius and wall side of 3 height.  At adsorption step and rinsing step, rise of temperature which is caused by adsorption of carbon dioxide is observed from bottom to top.  On the other hands, temperature goes down simultaneously at desorption step.  Adequate adsorption, rinsing and desorption time is easily known by this method.

Those results ware obtained at small PSA testing apparatus compared with commercial sized plant. The diameter and length of adsorption tower in commercial plant is presumed to be 6.5m and 20m, respectively.  The volume of adsorption tower of commercial plant is near 1 thousand times larger than that of ASCOA-3.  Especially, there are possibilities that the gas pressure and the velocity in the adsorption tower will not be uniform because the adsorption tower is enormously large as mentioned.  The gas pressure distribution of lower face of adsorbent is calculated with "Fluent". Unexpectedly the results of calculation clearly show that pressure distribution is homogeneous and the maximum difference is only 0.03kPa as shown in Figure 4.  This means there needs no special design to the adsorption tower from the viewpoint of pressure distribution.

  COURSE 50 project including this study is sponsored by NEDO (New Energy and Industrial Technology Development Organization). 

Photo 1 Laboratory PSA Apparatus

Figure 1  Influence of Cycle Time

Figure 2 Influence of CO2 Concentration in Raw Gas

 Photo 2  Bird View of ASCOA-3

 Figure 3  Flow Diagram of ASCOA-3

Figure 4  Calculation Results of Pressure Difference in Commercial Adsorption Tower

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