scholarly journals Lightweight Gypsum Materials with Potential Use for Thermal Insulations

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5454 ◽  
Author(s):  
Cristina Dima ◽  
Alina Badanoiu ◽  
Silviu Cirstea ◽  
Adrian Ionut Nicoara ◽  
Stefania Stoleriu
Keyword(s):  
Sodium Bicarbonate ◽  
Power Plants ◽  
Methyl Cellulose ◽  
Fgd Gypsum ◽  
Combustion Gases ◽  
Negative Effect ◽  
Desulfurization Process ◽  
Entrained Air ◽  
Thermal Insulations ◽  
Bicarbonate Addition

This article presents the influence of three additions i.e., hydroxyethyl methyl cellulose (HEMC), sodium bicarbonate and flue gas desulfurization (FGD) gypsum on the porosity of gypsum-based materials. The specific microstructure for a material with good thermal insulation properties i.e., numerous closed pores distributed in the binding matrix, was achieved using HEMC (0.3 wt.%) and sodium bicarbonate (0.5–2 wt.%). The addition of HEMC to the gypsum binder determines, as expected, an increase of the porosity due to its ability to stabilize entrained air. In the case of a sodium bicarbonate addition, the pores are formed in the binding matrix due to the entrapment of the gas (CO2) generated by its reaction. Sodium bicarbonate addition delays the setting of gypsum binder therefore in this study FGD gypsum (waste produced in the desulfurization process of combustion gases generated in power plants) was also added to the mixture to mitigate this negative effect. The decrease of geometrical density (up to 13%, in correlation with the additive nature and dosage) correlated with the increase of the porosity, determines, as expected, the decrease of flexural and compressive strengths (33–75%), but improves the thermal properties i.e., decreases the thermal conductivity (9–18%).

The Effects of Corn Silage Dry Matter Content and Sodium Bicarbonate Addition on Nutrient Digestion and Growth by Lambs and Calves

1986 ◽  
Vol 63 (6) ◽  
pp. 1728-1736 ◽  
Author(s):  
R. R. Worley ◽  
J. A. Paterson ◽  
K. P. Coffey ◽  
D. K. Bowman ◽  
J. E. Williams
Keyword(s):  
Sodium Bicarbonate ◽  
Dry Matter ◽  
Matter Content ◽  
Corn Silage ◽  
Dry Matter Content ◽  
Nutrient Digestion ◽  
Bicarbonate Addition

scholarly journals Development and Optimization of Gastro-Retentive Formulation of Hydralazine HCl

2016 ◽  
Vol 8 (05) ◽  
Author(s):  
Himanshu Acharya ◽  
Rakesh Patel
Keyword(s):  
Drug Release ◽  
Sodium Bicarbonate ◽  
Methyl Cellulose ◽  
Optimization Procedure ◽  
Fickian Diffusion ◽  
Release Mechanism ◽  
Wet Granulation ◽  
Floating Tablets ◽  
Hydralazine Hydrochloride ◽  
Predicted Values

Hydralazine hydrochloride has a half-life of 2 to 4 hours with an oral bioavailability of 26-50%. Since hydralazine has a demethylating effect on various suppressor genes, it can be used in various types of cancer to support chemotherapy. The purpose of this study was to optimize and evaluate floating tablets of hydralazine hydrochloride designed to prolong the gastric residence time and to provide controlled release of the drug for 24 h. The floating tablets of hydralazine hydrochloride were prepared by the wet granulation method. Polymers of hydroxy propyl methyl cellulose (HPMC K100M), HPMC K15M, carbopol 940 and sodium bicarbonate were used as the release retarding agents. This study investigated utility of a 3-factor, 3-level Box-Behnken design and optimization process for floating tablet of Hydralazine with 5 replicates of center points. Amount of HPMC K4 (Hydroxy Propyl Methyl cellulose), amount of sodium bicarbonate were selected as the independent variables whereas total floating time (TFT), T90, % cumulative drug release at 24 hours, and T20, Q1 were selected as dependent variables. Non-Fickian diffusion release transport was confirmed as the release mechanism for the optimized formulation and the predicted values agreed well with the experimental values. Drug excipient compatibility studies were investigated by FTIR, DSC and XRD. The produced tablets exhibited good floating time and controlled drug release over a period of 24 h. The resultant data were critically analyzed to locate the composition of optimum formulations. All predicted values of response variables of optimized formulation demonstrated close agreement with the experimental data during optimization procedure.

Availability Balance of Steam Power Plants

1959 ◽  
Vol 81 (1) ◽  
pp. 35-42 ◽  
Author(s):  
C. A. Meyer ◽  
G. J. Silvestri ◽  
J. A. Martin
Keyword(s):  
Thermal Efficiency ◽  
Power Plants ◽  
Heat Rate ◽  
Development Effort ◽  
Combustion Gases ◽  
Steam Power Plants ◽  
Reheat Steam ◽  
Temperature Combustion ◽  
The Difference ◽  
Average Plant

The well-known expression for availability, b = h − T0s, is developed in a simple yet general manner. The changes in availability throughout several typical single and double reheat steam plants having different steam conditions have been calculated. Balances of availability are presented for each of the several plants. These balances show the net plant output as the difference between the availability added in the boiler and the various losses in availability throughout the plant. The maximum plant thermal efficiency (or minimum heat rate) is easily obtained from the ratio of the increase in availability to the heat added in the boiler. The availability balances present in fine detail the loss distribution throughout the plant. Some very interesting results are obtained. For example, an assumed average plant will have a calculated maximum thermal efficiency of about 75 per cent based on the ratio of the availability and the heat in the high temperature combustion gases. Due to the heat transfer through a temperature difference, this value is reduced to 50 per cent when based on the ratio of the availability and the heat added to the steam in the boiler. This average plant will lose an additional 10 points in thermal efficiency, due to internal losses in availability, resulting in a 40 per cent thermal efficiency (excluding boiler and auxiliary losses). These latter 10 points due to internal losses are roughly divided as follows: Pressure drop: 0.9 Turbine blading: 5.0 Turbine leakage: 0.6 Turbine leaving and hood: 1.0 Mechanical and generator: 0.7 Feed and healing system: 1.3 and Feed pump and motor inefficiency: 0.5 Total: 10.0 An availability balance enables one to make an accurate assessment of the losses in any power plant and therefore serves as a very accurate guide in directing development effort toward reducing the more significant losses.

CO2 Emission Abatement in IGCC Power Plants by Semiclosed Cycles: Part B—With Air-Blown Combustion and CO2 Physical Absorption

1999 ◽  
Vol 121 (4) ◽  
pp. 642-648 ◽  
Author(s):  
P. Chiesa ◽  
G. Lozza
Keyword(s):  
Power Plants ◽  
Pressure Ratio ◽  
Co2 Concentration ◽  
Absorption Process ◽  
Combustion Gases ◽  
Additional Equipment ◽  
Physical Absorption ◽  
Previous Solution ◽  
The One ◽  
The Impact

This paper analyzes the fundamentals of IGCC power plants with carbon dioxide removal systems, by a cycle configuration alternative to the one discussed in Part A (with oxygen-blown combustion). The idea behind this proposal is to overcome the major drawbacks of the previous solution (large oxygen consumption and re-design of the gas turbine unit), by means of a semiclosed cycle using air as the oxidizer. Consequently, combustion gases are largely diluted by nitrogen and cannot be simply compressed to produce liquefied CO2 for storage or disposal. However, CO2 concentration remains high enough to make separation possible by a physical absorption process. It requires a re-pressurization of the flow subtracted from the cycle, with relevant consequences on the plant energy balance. The configuration and the thermodynamic performance of this plant concept are extensively addressed in the paper. As in the first part, the influence of the pressure ratio is discussed, but values similar to the ones adopted in commercial heavy-duty machines provided here acceptable performance. Proper attention was paid to the impact of the absorption process on the energy consumption. The resulting net overall efficiency is again in the 38–39 percent range, with assumptions fully comparable to the ones of Part A. Finally, we demonstrated that the present scheme enables the use of unmodified machines, but large additional equipment is required for exhausts treatment and CO2 separation. A final comparison between the two semiclosed cycle concepts was therefore addressed.

Formulation and Evaluation of Gastro Retentive Drug Delivery System for Ofloxacin

2009 ◽  
Vol 2 (1) ◽  
pp. 428-434
Author(s):  
Dumpeti Janardhan ◽  
Sreekanth Joginapally ◽  
Bharat V. ◽  
Rama Subramaniyan P.
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Sodium Bicarbonate ◽  
Drug Delivery System ◽  
Delivery System ◽  
Release Kinetics ◽  
Methyl Cellulose ◽  
Alkaline Media ◽  
In Vitro Dissolution ◽  
Physical Parameters

The purpose of this investigation was to prepare a gastroretentive drug delivery system of Ofloxacin. Ofloxacin is a fluoroquinolone antibacterial which acts by inhibiting the topoisomerase enzyme which is essential in the reproduction of the bacterial DNA. It is highly soluble in acidic media and precipitates in alkaline media thereby losing its solubility. Hence, a gastroretentive system was developed to enhance the bioavailability by retaining it in the acidic environment of the stomach. Different formulations were formulated using various concentrations of hydroxy propyl methyl cellulose, sodium carboxy methyl cellulose, sodium bicarbonate and citric acid. The formulations were evaluated for quality control tests and all the physical parameters evaluated are within the acceptable limits of Indian Pharmacopoeia. All the formulations were subjected to in-vitro dissolution studies and compared with the marketed formulation. The floating lag time was below 15 seconds for all the formulations except F1 and F2. The floating duration was found to be more than 24 hours in all except F1, F2 and F10. Formulations F7 and F8 were used to study the effect of sodium bicarbonate and formulations F9 and F10 for the effect of hardness on the drug release. Drug release kinetics was studied for prepared formulations and optimized formulation F5 was found to follow zero order kinetics with r2 =0.993. The statistical analysis of the parameters of dissolution data obtained before and after storage for 3 months at 25°C/ 60%RH and 40°C/75%RH showed no significant change indicating the two dissolution profiles were similar.

Chlorine Sources, Sinks, and Impacts in WTE Power Plants

2010 ◽  
Author(s):  
Nickolas J. Themelis
Keyword(s):  
Air Pollution ◽  
Fly Ash ◽  
Corrosion Rate ◽  
Polyvinyl Chloride ◽  
Pollution Control ◽  
Power Plants ◽  
Air Pollution Control ◽  
Combustion Gases ◽  
The U.S ◽  
Stack Gas

The principal sources of chlorine in the MSW feed to WTE power plants are food wastes (e.g., wheat, green vegetables, melon, pineapple), yard wastes (leaves, grass, etc.), salt (NaCl), and chlorinated plastics (mostly polyvinyl chloride). Chlorine has important impacts on the WTE operation in terms of higher corrosion rate than in coal-fired power plants, formation of hydrochloric gas that must be controlled in the stack gas to less than the U.S. EPA standard (29 ppm by volume), and potential for formation of dioxins and furans. Past Columbia studies have shown that the chlorine content in MSW is in the order of 0.5%. In comparison, chlorine concentration in coal is about 0.1%; this results in much lower HCl concentration in the combustion gases and allows coal-fired power plants to be operated at higher superheater tube temperatures and thus higher thermal efficiencies. Most of the chlorine output from a WTE is in the fly ash collected in the fabric filter baghouse of the Air Pollution Control system. This study examined in detail the sources and sinks of chlorine in a WTE unit. It is concluded that on the average MSW contains about 0.5% chlorine, which results in hydrogen chloride concentration in the WTE combustion gases of up to 600 parts per million by volume. About 45% of the chlorine content in MSW derives from chlorinated plastics, mainly polyvinyl chloride (PVC), and 55% from salt (NaCl) and chlorine-containing food and yard wastes. An estimated 97–98% of the chlorine input is converted to calcium chloride in the dry scrubber of the Air Pollution Control (APC) system and captured in the fly ash collected in the baghouse; the remainder is in the stack gas at a concentration that is one half of the U.S. EPA standard. Reducing the input of PVC in the MSW stream would have no effect on dioxin formation but would reduce the corrosion rate in the WTE boiler.

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