Thermodynamic Modeling of Aqueous Piperazine/N-(2-Aminoethyl) Piperazine for CO2 Capture

AbstractAqueous piperazine (PZ) blended with N-(2-aminoethyl) piperazine (AEP) is an attractive solvent for CO2 capture from coal-fired power plants. A rigorous thermodynamic model was developed in Aspen Plus® to predict properties of PZ/AEP/H2O/CO2, using the electrolyte-Nonrandom Two-Liquid (eNRTL) activity coefficient model. A sequential regression was performed to represent CO2 solubility, speciation, and amine volatility data over operationally significant loading and temperature ranges. The model predicts a CO2 cyclic capacity of 0.86mol/kg (PZ + AEP + water) for 5 m PZ/2 m AEP, compared to 0.50mol/kg for 7 m MEA and 0.86mol/kg for 8 m PZ. The predicted heat of absorption is 75 to 85kJ/mol CO2 in the operating loading range (0.288–0.380mol CO2/mol alkalinity). Speciation for PZ/AEP/H2O at various CO2 loading and temperature was also predicted, from which behavior of CO2 in the amine system was proposed

Process for removing sulfur from sulfur-containing gases

The present disclosure relates to i The government may own certain rights in the present invention pursuant to EPA Cooperative Agreement CR 81-1531. This is a continuation of U.S. Ser. No. 928,337, filed Nov. 7, 1986, now U.S. Pat. No. 4,804,521.Board of Regents, University of Texas Syste

Optimum design and control of amine scrubbing in response to electricity and CO2 prices

AbstractThis paper presents steady state and dynamic modelling of post combustion CO2 capture using 30 wt% MEA integrated with models of CO2 compression and the steam power cycle. It uses multivariable optimization tools to maximize hourly profit of a 100 MWe coal-fired power plant. Steady state optimization for design provided optimum lean loading and CO2 removal as a function of price ratio (CO2 price/electricity price). The results indicated that for price ratio between 2.1 and 7, the plant should be designed at removal between 70% and 98% and lean loading in the range of 0.22–0.25. Dynamic optimization determined the operation of the capture system in response to two partial load scenarios (reboiler steam load reduction and power plant boiler load reduction) and provided optimum set points for steam rate, solvent circulation rate and stripper pressure control loops. Maximum profit is maintained by allowing the stripper pressure to drop and implementing a ratio control between solvent and steam rate (and flue gas rate for partial boiler load operation)

Concurrent Validity of the Wide Range Assessment of Memory and Learning and the Woodcock-Johnson Tests of Cognitive Ability-Revised with a Neurologically Compromised Pediatric Population

The Wide Range Assessment of Memory and Learning (WRAML) is a relatively new instrument used in the assessment of memory in children. The purpose of this study was to examine the validity of the WRAML by comparing the performance of children on both the WRAML and the Woodcock-Johnson Tests of Cognitive Ability- Revised (WJTCA-R). Subjects for the study were children in treatment for a brain tumor at a regional children's medical center. Fifty children participated in the study ranging from ages 6 to 17. A multiple regression analysis was conducted to determine which of four selected clusters from the WJTCA-R would have the highest correlation with the Verbal Memory Index (VERI) from the WRAML. The Short-Term Memory (GSM) cluster had the highest correlation ( r = .82) as predicted. A Pearson's product-moment correlational analysis was conducted between the Visual Processing (GV) cluster from the WJTCA-R and the Visual Memory Index (VISI) from the WRAML. GV was found to have a high positive correlation ( r = .63) with VISI. A similar analysis was conducted between the Long-Term Retrieval (GLR) cluster from the WJTCA-R and the Learning Index (LRNI) from the WRAML. GLR was found to have a high positive correlation ( r = .81) with LRNI. Finally, a correlational analysis was conducted between the Broad Cognitive Ability (BCA) scale from the WJTCA-R and the General Memory Index (GENI) from the WRAML. A high positive correlation ( r = .87) was found between these most global measures from the two batteries. The observed correlation between BCA and GENI was much higher than anticipated. The author concluded that neurological impairment had affected subject memory and intellectual functioning in similar ways. The results do not generalize to children who have not had similar decrements in cognitive functioning. Future research should establish a baseline correlation between the two instruments with a non-impaired population

Seasonal and daily variation in blood and urine concentrations of free-ranging Angolan free-tailed bats (Mops condylurus) in hot roosts in southern Africa

Urine and plasma concentrations and haematocrits were measured in free-ranging Angolan free-tailed bats (Mops condylurus) inhabiting thermally-challenging roosts in the Komatipoort region of South Africa. Samples were collected in both autumn and summer, from bats caught emerging from roosts before feeding (pre-feed- ing), and those returning after foraging (post-prandial). Post-prandial bats exhibited higher body fluid concentrations, but lower haematocrits, than individuals caught prior to feeding, reflecting raised excretory mineral and nitrogenous loads and replenishment of body water pools during nocturnal foraging. Pre-feeding concentrations of both urine (2637 ± 506 mOsm/kg; n = 16) and plasma (331.5 ± 25.9mOsm/kg; n = 24) were significantly higher in summer than autumn (urine: 2157 ± 454mOsm/kg; n = 8; plasma: 294.5 ± 35.2 mOsm/kg; n = 18) reflecting the greater dehydration stresses within hotter roost microclimates, and a moderate kidney concentrating ability in this species. Haematocrits of pre-feeding animals were not, however, influenced by season and in both instances exceeded 53%, indicative of the higher oxygen carrying capacity needed for sustained flight in volant insectivores and also the defense of the rheologica! properties of blood. The ability of Mops condylurus to withstand a thermally-challenging roost milieu reflects, in part, its tolerance to dehydration, rather than the maintenance of water balance through exceptional renal concentrating ability

Apparatus for and method of removing acidic gas from a gaseous stream and regenerating an absorbent solution

An apparatus for and method of removing acidic gas from a gaseous stream and regenerating an aqueous solution allows for the recovery of waste heat of stripping steam and more economical regeneration of the aqueous solution. In at least one embodiment, one or more rich solvent bypasses combine with a rich solvent heat exchanger to recover waste heat. In another embodiment, the apparatus and method include one or more rich solvent bypasses and a heater positioned upstream of the stripper to more economically regenerate an aqueous solution.Board of Regents, University of Texas Syste

Survival tactics within thermally-challenging roosts: heat tolerance and cold sensitivity in the Angolan free-tailed bat, Mops condylurus

We studied roost microclimates, thermal preferences and temperature-related variation in body temperatures and flight abilities of M. condylurus from three roosts in man-made structures in South Africa. Roosts were characterized by marked spatio-temporal variability in ambient temperature and relative humidity on a daily and seasonal basis. Microclimates were thermally challenging, being very hot (>40°C) for several hours daily in summer and autumn, and cold (<10°C) for much of the night in winter Thermal preference tests revealed that the bats actively selected temperature zones (35°- 42°C) in which basal metabolic rate could be maintained, and above the minimum necessary for sustained flight. This presumably allowed them to minimize energy costs of thermoregulation without compromising reproductive activity or their ability to avoid predators. Bats displayed pronounced heat tolerance and hyperthermia in response to prolonged experimental exposure to high temperatures (40°C). They also exhibited cold-sensitivity, characterized by hypothermia and entry into torpor, when exposed to ambient temperatures below the thermal neutral zone. This response to low ambient temperatures would conserve energy in cold periods when the high energetic costs of foraging may not be met owing to reduced insect availability. We hypothesize that this broad roosting tolerance has energetic, ecological and evolutionary benefits that outweigh attendant disadvantages, which are largely compensated for by an unusual physiology

Blends of amines with piperazine for CO2 capture

Compositions and methods related to the removal of acidic gas. In particular, the present disclosure relates to a composition and method for the removal of acidic gas from a gas mixture using a solvent comprising a blend of piperazine and at least one diamine or triamine.Board of Regents, University of Texas Syste

Catalysts and inhibitors for MEA oxidation

AbstractAqueous monoethanolamine (MEA) was subjected to oxidation by O2/CO2 at 55 ∘C. Hydroxyethyl-formamide (HEF) and hydroxyethylimidazole (HEI) are the major oxidation products of MEA. Dissolved metals catalyze oxidation in the order copper > chromium/nickel > iron > vanadium. Inhibitors A, B and ethylenediaminetetracetic acid (EDTA) are effective degradation inhibitors. The addition of the expected inhibitors formaldehyde, formate or sodium sulfite had unintended effects on MEA losses. Total carbon and nitrogen analysis shows a greater than 90% closure of the material balance

Dynamic operation of amine scrubbing in response to electricity demand and pricing

AbstractThis paper examines dynamic operation of CO2 capture with absorption/stripping using 7 m MEA, where the absorber is operated at full capacity with the stripper at reduced load. Depending on the cost of CO2 emissions, doing so in response to variations in electricity demand could improve annual profits by $10–$100 million or more at facilities with CO2 capture. Dynamic scenarios were simulated with a controlled, constant ratio of heat rate and solvent rate. With an 80% load reduction, scenarios that turn CO2 capture off and on affect stripper performance only slightly and reach the steady state in about 90 and 18 minutes respectively