Capturing CO2 from ambient air - David Keith

More documents

Recommendations

Info

Figure B.5: Tower support structure 74
fastened together and lined, the reaction chamber was lifted by crane and placed onto the frame, a sparse truss-like structure of 1x3 in (nominal) pine boards (see Figure B.5). The donut, also suspended from the frame, is plywood and pine-board frame with 1/8 in PVC interior walls. The cone was constructed of two custom-cut PVC sheets folded into shape and fixed together with stainless steel bolts and sealant. The very tip of the cone is a standard polyethylene funnel fitted with a flexible 1 in diameter tube by hose clamp. The bottom of the reaction chamber is positioned 4 in below the top of the donut so that air leaving the reaction chamber is forced to make a sharp U-turn and travel upwards a short distance, shedding most of the entrained drops, before entering the particle trap. The cone is set at a 45 ◦ angle with respect to the horizontal to minimize splashing (and creation of fine mist which may bias the rate of CO2 uptake) at the bottom of the reaction chamber. Also, since the flow lines of process air pass into the donut above the cone, we reason that edge effects as the spray hits the bottom will have a negligible impact on mass transfer. A lip on the bottom of the inside wall of the reaction chamber collects solution running down the walls and channels it to a separate return-flow tube that exits through a hold in the cone. The lip is a 1 in diameter flexible tube cut in half to form an open-top channel, and slightly sloped so that collected fluid drains to a single dedicated return-flow tube attached to the bottom of the channel. The separate return flow for fluid hitting the walls allows for measurement of the relative fraction of spray hitting the walls as opposed to remaining as drops through the reaction chamber. B.1.2 Materials compatibility Since the working solution would be strong caustic (up to 20 wt%, pH 14.7), we required materials that would stand up to caustic for several cumulative days of running time. Fortunately, most plastics have excellent caustic compatibility, including the most common and inexpensive varieties, like polyvinyl chloride (PVC) and polyethylene (PE). Most of the wetted surfaces in the prototype were constructed of PVC. Portable PE gasoline cans served as convenient solution reservoirs and storage containers. Most tubing was PE or nylon, and fittings were stainless steel Swagelok. The wire mesh particle trap was constructed of stainless steel wool and the spray nozzles and some miscellaneous fasteners were also stainless steel. A chemical-resistant pump head and an off-the-shelf silicon-based sealant completes the list of wetted materials (the sealant was not explicitly resistant to caustic but it was tested and did not visually degrade after several days of submersion). B.1.3 Air handling and air safety As in a full-scale contactor, the prototype has a forced-air system which is meant to move air uniformly through the tower co-current with the spray and employs a particle trap to keep a significant fraction of the working solution (in the form of very fine droplets) from leaving the system with the outlet air. See Figure B.6 for a diagram. The prototype had the additional constraint that experimenters working and breathing close to the prototype should not be exposed to hazardous levels of caustic particles. OSHA standards for airborne concentration of caustic solution were used as a guide. 75
Page 1 and 2:
Capturing CO2 from ambient air: a f
Page 3 and 4:
For my family, friends, and everyon
Page 5 and 6:
etween the National Science Foundat
Page 7 and 8:
Contents Acknowledgments iv Abstrac
Page 9 and 10:
List of Figures 1.1 Global CO2 emis
Page 11 and 12:
Chapter 1 Introduction The climate
Page 13 and 14:
egeneration at a high enough concen
Page 15 and 16:
1.4 Routes to air capture 1.4.1 Org
Page 17 and 18:
The NaOH approach is the primary su
Page 19 and 20:
there is no compelling reason to ca
Page 21 and 22:
7Na2CO3(l)+5Na2Ti3O7(s) ⇋ 4Na8Ti5
Page 23 and 24:
changing the process design to acco
Page 25 and 26:
Component / source GJ/t-CO2 electri
Page 27 and 28:
Chapter 3 Contactor In this chapter
Page 29 and 30:
the CO2 capture rate in a spray sys
Page 31 and 32:
CO 2 absorption per pass [mol/l] 10
Page 33 and 34: CO 2 absorption [mmol/pass] 16 14 1
Page 35 and 36: Figure 3.5: Water loss measured in
Page 37 and 38: 3.3.1 CO2 depletion in air With lon
Page 39 and 40: where vt,1 and vt,2 are the termina
Page 41 and 42: surface area [m 2 -surface / m 3 -r
Page 43 and 44: spray mass density [kg / ln(μm)] 1
Page 45 and 46: average surface area [m 2 -spray /
Page 47 and 48: As a bound on the effects of coales
Page 49 and 50: Draft type Height [m] Crosssectiona
Page 51 and 52: 2. Median assumptions, no coalescen
Page 53 and 54: capture system. We can also see tha
Page 55 and 56: Multistage spray One possible solut
Page 57 and 58: Although, the cost of water loss ma
Page 59 and 60: 3.5.6 Solids formation - scaling an
Page 61 and 62: Chapter 4 Cost of air capture Altho
Page 63 and 64: Capital Capacity Electric a Thermal
Page 65 and 66: Component Capital + O&M Energy cost
Page 67 and 68: Chapter 5 Discussion Overview In th
Page 69 and 70: 5.2 Lessons for assessing of future
Page 71 and 72: Bibliography Adams, P. J. and Seinf
Page 73 and 74: IPCC (2001). Climate Change 2001: M
Page 75 and 76: Tzivion, S., Feingold, G., and Levi
Page 77 and 78: F Liquid flow rate in the contactor
Page 79 and 80: Appendix B Experimental details and
Page 81 and 82: Figure B.2: Photograph of completed
Page 83: Figure B.4: Two cranes lift the rea
Page 87 and 88: The prototype has three particle fi
Page 89 and 90: Figure B.7: Sampling points of CO2
Page 91 and 92: In order to calculate CO2 absorbed,
Page 93 and 94: Absorbed CO 2 [mol/l] 0.3 0.25 0.2
Page 95: periodic switching of the spray on
show all

Capturing CO2 from ambient air - David Keith

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?