4,607 research outputs found
Catalytic production of petrochemical products from bio-alcohols
Large-scale petrochemicals are typically produced using petroleum olefins as
a feedstock. The desire to move toward a sustainable and environmentally
friendly chemical industry has lead to interest in the use of bio-derived
feedstocks such as alcohols which are currently being produced on an
increasingly large scale by fermentation or from synthesis gas.
The research investigated the direct catalytic production of ethylene,
acetaldehyde, ethylene dichloride (EDC), and ethylene oxide (EO) from
ethanol. Two approaches were considered: a) the use of a bi-functional
catalyst that combines the dehydration capability with ethylene conversion
and b) the use of a double catalytic bed system where ethanol was dehydrated
over the 1st bed and the product ethylene was converted over the 2nd bed to
yield the desired petrochemical product.
The dehydration of ethanol was carried out over several zeolites at different
operating temperatures, producing mainly ethylene and diethyl ether.
The catalytic selective oxidation of ethanol was tested over silver and/or
copper compounds supported on several zeolites. The effects of operating
conditions, metal loading, and zeolite acidity were determined. High
selectivity to acetaldehyde was achieved. Unfortunately, the direct production
of EO from ethanol could not be achieved.
The catalytic oxychlorination of ethanol was investigated using CuCl2 as the
active compound and zeolites were used as either a support or as a pre-bed.
EDC was produced via ethylene oxychlorination as well as the
oxychlorination and disproportionation of ethyl chloride. The effects of
operating conditions and CuCl2 loading were determined. Higher EDC yield
was achieved over the dual-bed system compared to the bi-functional catalyst
Carbon dioxide capture from Flue gases
Global warming and climate change are believed to be caused by the greenhouse effect. CO2 has been regarded as the main contributor to global climate change which directly results in serious environmental problems. Half of the anthropogenic CO2 emission sources are emitted from the combustion of fossil fuels in industries and power plants worldwide. The absorption behavior of Carbon dioxide from flue gases can be studied using conventional absorber and polymeric hollow fiber membrane contractors. An industrial absorber data was compared with simulated data using hollow fiber membrane contractor using the gPROMs software package. In this analysis, with the absorbent solution flowing in the inner side of the fiber bore and the pure gas in the shell, the module was operated in a non-wetted mode. The derived coupled, non-linear partial differential equations were solved by backward finite difference method. The Diethanolamine (DEA) was used as absorbent. The outlet absorbed Carbon dioxide concentration was simulated and studied with respect to the liquid velocity, initial amine concentration and external mass transfer coefficient. The analysis includes the effects of the diameter and length of the fibers on the liquid outlet gas concentration as a function of the liquid velocity in the fiber. It was found that the liquid velocity and initial absorbent concentrations, as well as the fiber inner diameter and length, have a tremendous effect on the Carbon dioxide removal performance
Private sector participation in the water and sanitation sector: alternative options and measurement issues
This paper studies various aspects of the increasing role of private investment in the water services and sanitation (WSS) sector in developing countries. We start by surveying the different types of private sector participation (PSP) in the WSS sector, and the share of public and private responsibilities under each scheme. We then proceed by empirically testing the impact of PSP in the provision of water and sanitation on the average individuals’ welfare with regard to water and sanitation. This paper shows that the private sector has the potential to generate a number of social and environmental benefits for a number of reasons, including its potential to increase efficiency within the sector and increase much-needed levels of investment. Poorer households gain access to affordable services from which they have long been excluded. Furthermore, adverse public health effects of inadequate service provision may be mitigated, and wastewater collection and treatment levels may be increased. The paper also illustrates actual case studies involving PSP in developing countries to present some of the actual improvements that the private sector has already generated, particularly the increased access to water and sanitation, and the rise in water use as suggested by our empirical part.Water demand, public-private partnership, conservation
Polymer Retention during Flow of Polymer Solutions through Porous Media
Polymer solution flow and retention through porous media is of interest to many applications
in the oil industry such as drilling, water shut-off and enhanced oil recovery. Operators of
mature oil and gas fields are faced with the problem of excessive water production (EWP),
which can cause a premature abandonment of some oil and gas wells. It has been found that
the injection of high molecular weight polymer solutions through the pay zones of the oil and
gas wells would induce a sharp decrease of the water production without affecting the oil and
gas production. This effect is called disproportionate permeability reduction (DPR) and the
polymer solutions inducing such an effect are called relative permeability modifiers (RPM).
Hence, the DPR effect has been utilized in the water shut-off or conformance control of oil
and gas wells suffering from EWP. In spite of the extensive research of the DPR effect, there
is still a lack of agreement on the mechanisms controlling such an effect and relatively high
percentage failures are observed during conformance control field applications. Polymer
retention in porous media has been attributed to mechanisms such as bridging-adsorption,
adsorption-entanglement, and flow-induced adsorption. These mechanisms have been
proposed to account for the increase in flow resistance during or after the flow of polymer
solutions through porous media. The DPR effect has been attributed to effects induced by this
retained polymer such as steric and lubrication effects, wettability change, segregated oil and
water pathways, and swelling and shrinking of the adsorbed polymer layer. The aim of this
study is to add knowledge on the effect of polymer solution flow on polymer retention in
porous media.
In this study, the rheology of high molecular weight polymer solutions was studied
using a cone-and-plate setup. Moreover, the characteristics and the effective hydrodynamic
thickness of adsorbed polymer layers on glass from these polymer solutions under static
conditions were investigated using atomic force microscopy (AFM). Also, quartz crystal
microbalance with the dissipation monitoring (QCM-D) was used to investigate the effect of
increasing the flow rate of polymer solutions on the adsorbed amount on silica and gold
surfaces. Additionally, the mobility reduction and the residual resistance as a result of
polymer solution flow through single glass capillaries, 2D and 3D models of porous media
were studied. The implementation of the above techniques was used to relate the microscopic
effect of the flow of the polymer solutions to the polymer retention in the porous media. The
anti-thixotropic behaviour of the polymer solutions, which can be attributed to the shearinduced
formation of micron-size transient entanglement networks (TEN), is expected to play
a major role in the polymer retention in porous media. These microscopic structures can
adsorb on the solid surfaces if the adsorption energy of the polymer/solid system is sufficient.
Also, in porous media in which mechanical entrapment is possible, these structures can be
entrapped in the small pores and pore throats. Two new mechanisms for polymer retention
are proposed in this study: transient-entanglement networks adsorption (TENA) and
transient-entanglement networks entrapment (TENE). The TENA is the retention mechanism
of the TEN structures in flow systems in which mechanical entrapment is not possible
provided that the adsorption energy is sufficient. If mechanical entrapment is possible, then
the retention by adsorption and mechanical entrapment are lumped in the TENE mechanism.
The results from this study have given a new insight on the flow and retention of
polymer solutions through porous media. Hence, it is believed that the improved
understanding will improve the design of high molecula
A BIOECONOMIC ANALYSIS OF THE NORWEGIAN SPRING SPAWNING HERRING (NSSH) STOCK
A biological model belonging to the Beverton-Holt age-structured family for the Norwegian spring spawning herring (Clupea harengus) (NSSH) is simulated, the outcome of which compares well with actual data on the fishery. This model is then combined with an economic model to help investigate how optimal a management policy of constant fishing mortality will be for a fishery such as the NSSH, which has a highly fluctuating stock biomass. For the range of constant values of fishing mortality explored, and a simulation time horizon of 20 years, a constant fishing mortality of 0.15 turns out to be economically optimal. It should be noted that this result is sensitive to variations in the assumptions underlying key variables of the fishery. For example, when a constant rather than variable recruitment was assumed, a different optimal fishing mortality rate was obtained.bioeconomic model, herring optimal management, Resource /Energy Economics and Policy, Q57, Q22, Q28,
- …