Managing your process hazards as a means of conforming to ohsa requirements

There is considerable evidence that improper changes have directly caused or through the “domino sequence” led to many of the major accidents that have occurred in the chemical process industry and related industries that use hazardous chemicals and technology. Central Government has recognised the importance of careful management of change(MOC) for ensuring the safety of chemical operations and the quality of manufactured goods by the proposed adding of the Major Hazardous Installation Regulation to the OHSA (Act 85 of 1993).

The concept and the need to properly manage change are not new; many companies have adopted MOC procedures. It is common practice nowadays to perform detailed risk assessments on any new or intended project to ensure safety and reliability of the project. Yet, incidents and near misses attributable to inadequate management of changes on existing systems and processes continue to occur. To improve the performance of MOC systems throughout industry, managers need advice on how to better institutionalise MOC systems within their companies and plants.

The purpose of this paper is to define the important features of MOC systems and to assist in the implementation and management of process hazards. MOC systems help ensure that changes to design and operation of company facilities will not adversely affect employees, the public, or the environment. This document outlines a process that can be used for designing, developing, installing, operating, and maintaining MOC systems at individual company sites.

This paper is intended for an audience ranging from plant and corporate managers of process safety to workers who have differing levels of knowledge about the principles of safely managing change. It is primarily designed to equip people responsible for MOC systems with new ideas for implementing and improving MOC systems. It was indeed a privilege to have met the personnel of JBF Associates, Inc. and Process Safety Institute in Knoxville, Tennessee, USA, without whose lectures and study material (including the book “Managing process changes”) this paper would never have seen the light. They have succeeded in putting me firmly on the “process safety road”.     

On the recovery of LNG physical exergy by means of a simple cycle or a complex system

The maximum and minimum temperatures available limit the usable fraction (or Carnot efficiency) of a power cycle. The construction of LNG terminals and the need to vaporize LNG offers a thermal sink at a very much lower temperature than seawater. By using this thermal sink in a combined plant, it is possible to recover power from the vaporization of LNG.To this purpose, in this paper combined systems using LNG vaporization as low-temperature thermal sink are considered and their pros and cons are presented. A system utilizing waste energy as heat source and with a single working fluid is analyzed in detail. However, the use of a single fluid is not the best solution from a thermodynamic point of view. Thus, a series of cascading cycles is also outlined. In these systems, both the thermal source and the thermal sink are exploited as exergy sources.     

An evaluation of the life cycle cost of rapeseed oil as a straight vegetable oil fuel to replace petroleum diesel in agriculture

The use of straight vegetable oil (SVO) as biofuel has been recognized as a valid substitute of diesel fuel in the agricultural sector under specific circumstances. Its direct use reduces most of the chemical processes involved when converting it into biodiesel, thus lowering harmful emissions. This study presents the economic analysis of a self-supply farming model that uses rapeseed as its fuel base. This model addresses agricultural environmental concerns and can even minimize dependence on the fluctuating costs of diesel fuel. The use of SVO in agriculture can help reduce farmers’ vulnerability to fossil fuel prices. The economic evaluation of the model proposed in this study shows clear economic benefits of introducing rapeseed to the traditional crop rotation of wheat and barley. The key factors analyzed in this model are diesel fuel price, diesel fuel grants and crop aids. The current situation in Spain favors the use of diesel fuel in agriculture rather than rapeseed SVO due to an 8% profit difference. However, results show that changes in key factors slightly affect the profit margin, calculating a difference of only 3.7% for particular factor combinations. Combined environmental-friendly agriculture supporting policies are necessary to cover this slight profit difference to promote this biofuel.     

Lessons learnt during the design,construction and start-up phase of a molten salt testing facility

In 2010, CIEMAT (Centro de investigaciones energéticas medioambientales y tecnológicas) signed a turn-key contract to have an experimental plant for thermal storage using molten salts at its PSA (Plataforma Solar de Almeria) facilities. This plant was designed to evaluate components, instrumentation and operation strategies and to give support to the industry in the qualification and evaluation of components.During the design, construction and start-up phases of this plant, many different aspects regarding design, construction and commissioning have been learnt and these will contribute to the improvement of other plants.Among other tips explained in the paper, we recommend the use of venting valves to eliminate the water present in the system after the pressure test or released by the salts during the first melting. The selection of instrumentation with no electronic components near a heat source, thus preventing them from overheating, is also advisable. The heat exchanger design and dimensioning should take into account not only the thermal losses to the atmosphere and through pipes and supports, but any possible reduction in the heat exchange surface that could have detrimental consequences in the thermal performance.Special attention must be paid when dimensioning and installing the EHT and insulation because both components are decisive in the avoidance of plug formation. Its correct installation in valves and supports and the proper positioning of the temperature control sensors, i.e. where no other heat source can distort the readings, are crucial.Recommendations and strategies for the operation and shutdown of this experimental plant are being gathered for a future paper.     

Management,conversion, and utilization of waste plastic as a source of sustainable energy to run automotive: a review

Increased usage of plastic and absence of an efficient system to address its non-degradability has become a serious issue threatening the human life. On the other hand, increased fossil fuel consumption which led to their depletion necessitates the search for an alternative that could replace the conventional fuels and alongside abate the emissions. Both the non-degradability of plastic and need for an alternative fuel can be addressed by converting the waste plastic to useful energy. The present article reviews about pyrolysis, a chemical treatment to convert waste plastic to energy. It also focuses on its functional feasibility as a fuel in a compression ignition engine. Reportedly, waste plastic oil when used in a diesel engine yields lesser thermal efficiency, higher brake specific fuel consumption, increased emissions of carbon monoxides, and oxides of nitrogen and unburnt hydrocarbons. Irrespective of its disadvantages, it is worthwhile to note that it is waste plastic which is converted to useful energy. However, not much work on the technical feasibility and functional efficacy of waste plastic oil as a fuel in a diesel engine is reported, and hence, research in this application seems to gain its focus in near future.     

Performance parameters analysis of reverse electrodialysis process: Sensitive to the repeating unit pairs,inflow velocity and feed concentration

Reverse electrodialysis (RED) is the most promising technique based on ion exchange membranes for harvesting salinity gradient energy. In the present study aimed to explore the sensitivity of the RED stack performance, different concentrations of NaCl were prepared and used to simulate the salinity of concentrated seawater and that of river water at 298 K. Some major factors including the repeating unit pairs, the flow velocity and the feeding concentration were investigated. When the positive effect by the increase of open-circuit voltage is greater than the negative effect caused by the increase of internal resistance, the electrical performance of RED stack is improved, and the maximum power density is increased. On the contrary, the value of maximum power density is decreased. The maximum power density reached its maximum when eight repeating units were used, and the optimum flow velocity was obtained as 0.71 cm/s. At a same concentration gradient of the feed, a lower internal resistance was observed at a higher total salinity, leading to better energy generation performance.     

Determination of the energy storage efficiency of the photoisomerization of norbornadiene to quadricyclane as a potential means for the trapping of solar energy

The fraction of incident radiant energy stored in chemical form by the photosensitized isomerization of norbornadiene to quadricyclane has been estimated. This reaction has been widely viewed as a potential means for the conversion of solar energy to useful heat. Using a xenon lamp as a radiant energy source in lieu of natural sunlight, 1-M acetophenone-norbornadiene and benzophenone-norbornadiene solutions were irradiated for 2-h periods with 1–5-mW radiant power levels delivered in 4-nm bandwidths centered on 300 nm, 350 nm, 400 nm and 450 nm. In each case the reaction was carried out batchwise at four temperatures in the liquid-phase range of the solutions, namely, 278 K, 298 K, 318 K and 333 K, controlled to within ±2 K. The results indicate that about 8.8% of the total available incident light contained in the region from 300 nm (lower end of the solar spectrum that impinges upon the earth's surface) to 425 nm (approximate absorption threshold of the sensitizers acetophenone and benzophenone; maximum wavelength capable of promoting the reaction under the conditions of this study) can be stored in the chemical bonds of quadricyclane in the acetophenone-sensitized isomerization and about 14.5% when benzophenone is utilized. Based on the entire solar spectrum, these energy storage efficiencies translate into 0.9% and 1.5%, respectively. Efficiency values were estimated by determining the quantum yield of the reaction as a function of wavelength and temperature. While the data show no definitive temperature dependence, it has been established that the functional relationship with wavelength follows the same pattern as the absorption spectra of the sensitizers themselves.     

Exergy destruction during the combustion process as functions of operating and design parameters for a spark‐ignition engine

The second law of thermodynamics provides different perspectives compared with the first law, and provides the property exergy. Exergy is a measure of the work potential of energy from a given thermodynamic state. Unlike energy, exergy may be destroyed, and for reciprocating engines, the major source of this destruction is during the combustion process. This paper provides an overview of the quantitative levels of exergy destruction during the combustion process as function of engine operating and design parameters, and for eight fuels. The results of this study are based on a spark‐ignition, automotive engine. The amount of exergy destroyed during the combustion process has been determined as functions of speed, load, equivalence ratio, start of combustion, combustion duration, combustion rate parameters, exhaust gas recirculation (EGR), inlet oxygen concentration, and compression ratio. In addition, design parameters that were examined included expansion ratio and the use of turbocharging. The fuels examined included isooctane (base), methane, propane, hexane, methanol, ethanol, hydrogen and carbon monoxide. For the part load base case (1400 rpm and a bmep of 325 kPa) using isooctane, the destruction of exergy was 20.8% of the fuel exergy. For many of the engine operating and design parameter changes, this destruction was relatively constant (between about 20 and 23%). The parameters that resulted in the greatest change of the exergy destruction were (1) equivalence ratio, (2) EGR, and (3) inlet oxygen concentration. For the base case conditions, the exergy destruction during the combustion process was different for the different fuels. The lowest destruction (8.1%) was for carbon monoxide and the highest destruction (20.8%) was for isooctane. The differences between the various fuels appear to relate to the complexity of the fuel molecule and the presence (or absence) of an oxygen atom. Copyright © 2011 John Wiley & Sons, Ltd.     

Fatty acids composition as a means to estimate the high heating value (HHV) of vegetable oils and biodiesel fuels

High heating value (HHV) is an important property which characterises the energy content of a fuel such as solid, liquid and gaseous fuels. The previous assertion is particularly important for vegetable oils and biodiesels fuels which are expected to replace fossil oils. Estimation of the HHV of vegetable oils and biodiesels by using their fatty acid composition is the aim of this paper. The comparison between the HHVs predicted by the method and those obtained experimentally gives an average bias error of −0.84% and an average absolute error of 1.71%. These values show the utility, the validity and the applicability of the method to vegetable oils and their derivatives.     

循环流化床锅炉改造为链条炉的炉拱与配风研究

某循环流化床锅炉因不能适应生产调荷的需要而改造为链条炉。为使链条锅炉在烧劣质煤的情况下提高出力、热效率和经济效益,改造了锅炉的前、后拱,以改善煤的引燃和提高燃烧区的燃烧强度;改进了配风方式,使配风更加合理。     

Application of optimization techniques and the enthalpy method to solve a 3D-inverse problem during a TIG welding process

Tungsten inert Gas (TIG) welding takes place in an atmosphere of inert gas and uses a tungsten electrode. In this process heat input identification is a complex task and represents an important role in the optimization of the welding process. The technique used to estimate the heat flux is based on solution of an inverse three-dimensional transient heat conduction model with moving heat sources. The thermal fields at any region of the plate or at any instant are determined from the estimation of the heat rate delivered to the workpiece. The direct problem is solved by an implicit finite difference method. The system of linear algebraic equations is solved by Successive Over Relaxation method (SOR) and the inverse problem is solved using the Golden Section technique. The golden section technique minimizes an error square function based on the difference of theoretical and experimental temperature. The temperature measurements are obtained using thermocouples at accessible regions of the workpiece surface while the theoretical temperatures are calculated from the 3D transient thermal model.     

Energy efficiency as a credence good: A review of informational barriers to energy savings in the building sector

Information problems have early been suspected to be the main barrier to energy-efficiency investment. I review the vast yet piecemeal research that has been carried out since. Focusing on energy efficiency in buildings, I organize the review around the concept of credence good: just like that of auto repairs or taxi rides, the quality of energy-efficiency measures is never fully revealed to the buyer; as a result, it is subject to multiple information asymmetries. My first contribution is to distinguish symmetric-information problems from information asymmetries. The former arise when information is either incomplete or imperfect, but equally shared by contracting parties; as non-market failures, these can be addressed by technological progress and insurance markets. My second contribution is to give structure to the information asymmetries associated with energy efficiency by disentangling screening, signalling, moral hazard and price discrimination within a variety of contractual relationships involving buyers and sellers, owners and renters, borrowers and lenders, and regulators and policy stakeholders. I find evidence of information asymmetries to be compelling in utility-included rental contracts, unclear in home sales and rentals, and scarce in retrofit contracting and financing. I conclude by discussing the intricacies between informational and behavioural problems in energy-efficiency decisions.     

Facile process to utilize carbonaceous waste as a carbon source for the synthesis of low cost electrocatalyst for hydrogen production

Low cost non-noble metal electrocatalysts are highly desirable for the sustainable production of hydrogen as a renewable energy source. Molybdenum carbide (Mo₂C) has been considered as the promising non-noble metal electrocatalyst for the hydrogen production via hydrogen evolution reaction (HER) through water splitting. The nanostructured nitrogen (N) incorporated carbon (C) coupled with Mo₂C is the potential candidate to boost the HER activity and electrode material for the energy conversion applications. In this work, nitrogen incorporated carbon coated Mo₂C (Mo₂C@C/N) has been synthesized in an eco-friendly way using waste plastic as the carbon source. The pure phase Mo₂C@C/N has been synthesized at 700 and 800 °C for 10 h. The relatively higher temperature synthesized phase shows enhanced HER activity with lower Tafel slope (72.9 mVdec⁻¹) and overpotential of 186.6 mV to drive current density of 10 mAcm⁻². It also exhibits stability up to 2000 cyclic voltammetry (CV) cycles and retains the current density with negligible loss for 10 h. The higher temperature synthesized phase exhibits higher electrochemical active surface area (ECSA) and enhanced HER kinetics.     

Cyclic behavior of a pipe section subjected to bending, ovalization or torsion loads in the case of a perfectly plastic material

The work presented is a stage in the development of a global inelastic calculation method for thin pipes and includes an incremental formulation for handling nonmonotonic bending, ovalization and torsion loads in piping in the case of a perfectly plastic material. Each load is dealt with separately and the global variables used are moments and curvatures.     

Wind energy as an alternative source to alleviate the shortage of electricity that prevails during the dry season: a case study of Tanzania

Currently, hydroelectric power supply systems in Tanzania are faced with drought, site and water management problems hindering efficient and reliable power supply from this source. Thermal power systems that were intended to alleviate the shortage of hydroelectricity that arise during the dry season are themselves expensive due to high operational and running costs as a result of the increasing prices of petroleum and spare parts.Wind speed data from two prospective sites indicate that during the dry season, wind speed is sufficiently high and steady to generate electricity. The wind speed at these sites from August to October is well above 7.0 ms as measured at a height of 10 m above ground level. A combined hydro-generator and wind-turbine system is suggested as a possible alternative of electric power supply in Tanzania. The use of wind energy in generating electricity will reduce the large dependence on fossil fuel sources that are expensive and also harmful to our environment.     

Effect of combining Al,Mg, Ce or La oxides to extracted rice husk nanosilica on the catalytic performance of NiO during COx-free hydrogen production via methane decomposition

Amorphous nanosilica powder was extracted from rice husk and used as a catalyst support as well as a starting material for the preparation of different binary oxides, i.e., SiO₂Al₂O₃, SiO₂MgO, SiO₂CeO₂ and SiO₂La₂O₃. A series of supported nickel catalysts with the metal loading of 50 wt % were prepared by wet impregnation method and evaluated in methane decomposition to “CO_x-free” hydrogen production. The fresh and spent catalysts were extensively characterized by different techniques. Among the evaluated catalysts, both Ni/SiO₂Al₂O₃ and Ni/SiO₂La₂O₃ catalysts were the most active with an over-all H₂ yield of ca. 80% at the initial period of the reaction. This distinguishable higher catalytic activity is mainly referred to the presence of free mobile surface NiO and/or that NiO fraction weakly interacted with the support easily reducible at low temperatures. The Ni/SiO₂CeO₂ catalyst has proven a great potential for application in the hydrogen production in terms of its catalytic stability. The formation of Mg_xNi_(1?x)O solid solution caused the Ni/SiO₂MgO catalyst to lose its activity and stability at a long reaction time. Various types of carbon materials were formed on the catalyst surface depending on the type of support used. TEM images of as-deposited carbon showed that multi-walled carbon nanotubes (MWCNTs) and graphene platelets were formed on Ni/SiO₂, while only MWCNTs were deposited on all binary oxide supported Ni catalysts.     

Direct water balance analysis on a polymer electrolyte fuel cell (PEFC): Effects of hydrophobic treatment and micro-porous layer addition to the gas diffusion layer of a PEFC on its performance during a simulated start-up operation

Effects of hydrophobic treatment and micro-porous layer (MPL) addition to a gas diffusion layer (GDL) in a polymer electrolyte fuel cell (PEFC) have been investigated from water balance analysis at the electrode (catalyst layer), GDL and flow channel in the cathode after a simulated start-up operation. The water balance is directly analyzed by measuring the weight of the adherent water wiped away from each the component. As a result, we find that hydrophobic treatment without MPL leads to the increase in liquid water accumulation at the electrode which limits the oxygen transport to the catalyst and then lowers the cell voltage rapidly during start-up, whereas the treatment decreases the water at the GDL. The water accumulation at the electrode also decreases the cumulative current that represents the power generation and calorific power indispensable for warming up at a temperature below freezing point. On the other hand, we directly find that the hydrophobic treatment with MPL addition suppresses the water accumulation at the electrode, which increases the cumulative current. In addition, it is found that increase in air permeability of a GDL substrate by its coarser structure increases the cumulative current, which is explained by enhancing the exhaust of the product water vapor and liquid as well as by enhancing the oxygen transport directly. Thus, the hydrophobic treatment with MPL addition and larger air permeability of a GDL substrate improve the start-up performance of a PEFC.     

Findings to improve the performance of a two-phase flat plate solar system,using acetone and methanol as working fluids

An indirect two-phase water heating solar system was tested using acetone and methanol as working fluids. The working fluid circulates in a closed circuit that extends from the solar collector to a coil heat exchanger in the thermo tank. The working fluid evaporates in the solar collector and condensates in the thermo tank coil. This Phase Change System (PCS) prevents freezing, scaling, corrosion, and fouling; these advantages increase the lifetime of the system. The objective of this work is to characterise the performance of the PCS using different filled fractions of acetone and methanol, with two kind of initial pressures (atmospheric pressure, and partial vacuum), in order to find the appropriate conditions for a good performance of the system. For this purpose, the useful heat was determined, as well as the increment of temperature in the water of the thermo tank, and the experimental efficiency. Results are compared to a witness conventional Domestic Solar Water Heating System. The witness has the same characteristics (materials and dimensions) than the PCS, except for the coil heat exchanger presented in the PCS. The instrumentation set throughout the system includes temperature sensors, pressure transducers, a pyranometer and an anemometer, that permit to characterise and understand the performance of the system under different working conditions. By knowing the phenomenology of the working fluid in the closed circuit, the stratification profile of the water in the thermo tank, and the thermal performance of the solar collector, projections to improve the PCS can be formulated. The performance of the system is the result of several variables working together in combination: the working fluid, filled fraction, partial vacuum, coil length, as well as the working and ambient conditions. The appropriate combination of these variables is investigated to improve the performance of the PCS. Experimental results showed that the partial vacuum conditions at the beginning of the test led, as expected, to an improved performance of the PCS. Tests were carried out under the actual field conditions of Temixco, México.     

Fluidised bed studies of: (i) Reaction-fronts inside a coal particle during its pyrolysis or devolatilisation, (ii) the combustion of carbon in various coal chars

An approximately spherical particle of coal (diam. 13–14 mm) was made by filing a larger piece. Next a hole (diam. 0.6 mm) was drilled through the centre of the sphere to end at 3 mm from the opposite face. Into this hole a fine thermocouple (o.d. 0.2 mm) was cemented. The coal was immersed into an electrically heated bed of sand, fluidised by nitrogen at 850 °C. During the subsequent pyrolysis, the temperature was measured at 3 mm inside the coal. Minima were found in the local internal rate of increase in temperature, when plotted against either time or this measured internal temperature. Here is new evidence for large coals thermally decomposing by a sequence of “endothermic waves” moving radially inwards through the coal to release volatile matter. These minima are each associated with a particular temperature and 21 of them were found (apart from that for drying) between 160 and 820 °C. Altogether four bituminous coals and one lignite were studied. Some “decomposition temperatures” were common to them all. Lower rank coals have major losses of volatile material at lower temperatures. These experiments thus support the modelling of pyrolysis using a suite of approximately 20 parallel reactions, each contributing to different extents and with different kinetic parameters and ΔH.Experiments in an identical bed, but fluidised by air, revealed endothermic waves in a coal. In this case, some of the volatiles burned in a counter-flow flame in the recently discovered cushion of air underneath such a relatively large coal particle. Also, towards the end of devolatilisation, the resulting char started to burn; different chars burned at different temperatures, all above that of the bed, even though burning was controlled by external mass transfer of O₂ to the char particle. It appears that underneath a char particle, there is again a counter-flow flame, where CO (from burning the char) is oxidised by OH radicals to CO₂ at ～900 °C. Most probably the carbon in the char is also oxidised by OH radicals to CO. The temperature at which a char burns is partly controlled by how much CO is oxidised by OH radicals close to the underside of the char particle. The oxidation of both CO and carbon in a char accordingly appears to be catalysed by hydrogen from the char.