Short Payback Time Research Articles

Strategic simulation of the energy management in a Kraft mill

The economic assessment of an energy enhancement program envisaged for a Kraft wood pulping mill has been performed. The retrofit projects which have been analysed include reduction of the process steam demand, steam exportation to a district heating network and cogeneration. An automated MILP optimisation model has been developed to quantify the economic benefit of the projects independently and in combinations. Three cogeneration systems were considered: single back-pressure steam turbine, single steam condensing turbine and, a two-turbine system. A sensitivity analysis has been conducted for two modalities of key cost parameters (steam demand reduction level, fuel and power purchase costs, steam and power sales price) to determine the impact of those parameters on the economics of co-generation options. Results show that the configuration with the single back-pressure steam turbine has the shortest payback time, but the combination of two turbines produces more power and gives higher benefits in the long term.

Energy from wind – perspectives and research needs

Wind energy will provide a major share of our future energy supply, and, due to the possibility of going offshore, has an immense additional potential for power supply. To use wind energy in a reliable way, much research work still has to be done. One of these fields is the evaluation of wind energy in terms of sustainability. The results of Life Cycle Assessments (LCA) show that wind energy converters have a short energy payback time and low emissions, even in comparison with other renewable energy systems. Another field of research is the creation of optimisation models which can provide answers to questions concerning the future power generation mix. The opportunity exists, now that a great part of the over-aged conventional power plant stock has to be replaced, to adapt the power plant mix to an expanded share of wind energy. Within this mix, electric storage may play a major role. The results of the optimisation models indicate that storage sites alone will not be profi enough to reduce operating costs of the modelled system, and that this will only be possible through the option of energy trading. Hence there are interesting instruments in the deregulated energy market, especially for electric-power commodity exchanges like the EEX.

Glasses for solar energy conversion systems

Solar technologies are projected to increase tremendously over the next 10 years. Glasses are playing an important role as transparent materials of photovoltaic (PV) cells and concentrating solar power (CSP) systems. Glasses are materials of short energy payback time and environmental compatibility suitable for sustainable energy concepts. The paper reviews recent solar applications. Surface structuring and coating of glasses are shown to improve energy efficiency for solar conversion systems substantially. Encapsulated glass-to-glass PV modules and solar photocatalytic glass surfaces are identified as elements of a green architecture combining renewable power generating and destruction of air pollutants of urban environments. Emerging solar technologies for power generation, including transparent PV modules, solar chimney and thermoelectric systems may become significant areas of future solar glass applications.

Biogenic sulphide for cyanide recycle and copper recovery in gold–copper ore processing

Many complex-ore gold deposits with cyanide-soluble copper minerals such as chalcocite, covellite, bornite, cuprite, malachite and azurite are now being considered for processing. In some cases the ore is not currently being mined largely due to the various issues associated with the cyanide-soluble copper minerals in the ore, which results in low gold recoveries and high cyanide consumption and detoxification costs. Moreover, the presence of copper in tailings supernatant tends to stabilize weak-acid dissociable cyanide in a form toxic to wildlife. In the SART process (sulphidization–acidification–recycle–thickening), the cyanide associated with the copper cyanide complexes is released by NaHS dosing to precipitate copper and convert cyanide to HCN gas under weakly acidic conditions, allowing it to be recycled back to the leach process as free cyanide. Copper is also recovered as a valuable, high-grade (∼70% Cu) Cu 2S by-product. Cyanide recycling allows the leach circuit to be operated at higher cyanide levels, maximizing leach efficiency and minimizing copper deportment to gold electrowinning. The first commercial plant is at Telfer in Western Australia. Biogenically-produced hydrogen sulphide can be used to replace chemical sulphide at significantly lower cost and with the added advantage of lowering the acid demand substantially. While the capital cost of a biogenic SART plant will be higher than a cyanide detoxification plant, this will be more than offset by the revenues generated by copper recovery and the savings realized by cyanide recycle, allowing for a short payback time on the incremental capital. BioteQ is currently working with Columbia Metals Corporation Ltd., Canada, to apply its sulphide generating and precipitation technology in a SART circuit at both of Columbia’s gold projects (La Jojoba and Lluvia de Oro) in Northern Mexico. Processing of ores from both mines has presented challenges resulting from the presence of cyanide-soluble copper. This paper reviews the BioteQ biogenic SART process technology, economics and commercial status as well as environmental and operating outcomes.

Opportunities and challenges of using ultrafiltration for the concentration of diluted coating materials

The use of cross-flow ultrafiltration for the recovery of coating material from aqueous streams started about 30 years ago with electro-deposition paint in the automotive industry. This early success can be related to both environmental and economical advantages of using ultrafiltration. Ultrafiltration recovers and concentrates electro-deposition paint on the retentate side and produces purified water on the permeate side. Based on this success, the focus more recently moved to other coating materials, such as paper coatings, latex and flexographic ink. Similar to electro-deposition paint, the concept is to recover the diluted coating materials with ultrafiltration to obtain a solid-free permeate stream, which can be either recycled or easily treated, and a retentate stream, which contains the coating materials preferably at concentrations suitable for recycling or disposal. The advantages can be directly translated into very short payback times for ultrafiltration systems of typically less than two years. Application studies focusing on the coating recovery in a paper mill, the concentration of latex from the tank wash at a latex producer and the recovery of flexographic ink at a producer of printed cartons will highlight these benefits.

Automation Development in Water and Wastewater Systems

Advanced control is getting increasingly demanded in water and wastewater treatment systems. Various case studies have shown significant savings in operating costs, including energy costs, and remarkably short payback times. It has been demonstrated that instrumentation, control and automation (ICA) may increase the capacity of biological nutrient removing wastewater treatment plants by 10-30% today. With further understanding and exploitation of the mechanisms involved in biological nutrient removal the improvements due to ICA may reach another 20-50% of the total system investments within the next 10-20 years. Disturbances are the reason for control of any system. In a wastewater treatment system they are mostly related to the load variations, but many disturbances are created also within the plant. In water supply systems some of the major disturbances are related the customer demand as well as to leakages or bursts in the pipelines or the distribution networks. Hardly any system operates in steady state but is more or less in a transient state all the time. Water and energy are closely related. The role of energy in water and wastewater operations is discussed. With increasing energy costs and the threatening climate changes this issue will grow in importance.

Cleaner technology transfer in the Italian galvanic industry: economic and know-how issues

The paper, providing a technical and economic assessment of the available technologies in the Italian galvanic industry, highlights critical factors influencing strategic decisions on the adoption of BATs (Best Available Technologies) in the light of IPPC (Integrated Pollution Prevention and Control) Directive. A broad-based survey of the galvanic industry is presented revealing a considerable gap between the proposed BATs and the technological solutions currently installed. Then, BATs included in the EC Reference Report [BREF – reference document on best available techniques surface treatment of metals and plastic materials using electrolytic or chemical process (volume of treatment vats > 30 m 3). In: Surface treatment of metals and plastic materials using electrolytic or chemical process. European Committee for Surface Treatment; 2001] are analyzed and classified according to their documented economic performance and the complexity of implementation. Even if the analysis confirms the potential of BATs to generate significant cost savings with a short pay-back time, it is difficult for Italian small-medium enterprises (SMEs) to access the know-how needed to make strategic decisions regarding the implementation of BATs.

Handbook of Water Use and Conservation

Review: Handbook of Water Use and Conservation By Amy Vickers Reviewed by Russell A. Cohen Massachusetts Department of Fisheries, USA Amy Vickers. Handbook of Water Use and Conservation. Amherst, MA: WaterPlow Press, 2001. 446 pp. ISBN 1-931579-07-5 (hardcover). US$99.95. Recycled paper. paper. 'Water is our most precious resource' is a refrain expressed by many-from engineers and poets to politicians-yet humanity's actions have often belied those words. Amidst the world's growing population and increasing demand for more water, many regions around the globe are facing the hard realities of groundwater depletion, chronic drought, dried-up rivers, poor water quality, mounting infrastructure costs, and diminishing alternatives for additional supplies. As we peer into the 21st century, water conservation is looking far more like an imperative than an option (p. xv). So begins Amy Vickers' Handbook of Water Use and Conservation, to date the most authoritative, encyclopedic reference work available on this subject. The Handbook contains detailed descriptions of hundreds of water-efficiency technologies and practices for all customer groups-residential, landscape, industrial, commercial, institutional, and agricultural. Vickers backs up her claim that water conservation represents The Great Untapped Water Supply (p. xv) by presenting hundreds of proven water efficiency measures that reduce and control both short-term water demand (such as during drought and peak conditions) as well as long-term demand for each type of customer. Potential water savings and related costs are provided too, so you can know which measures will provide the best benefit/cost ratio for any type of customer. Vickers points out that many, if not most, water conservation measures have a relatively short payback time, often two years or less. As someone from a densely populated state where profligate household water use increasingly threatens the natural integrity of our streams and other hydric ecosystems, I found the Handbook's sections on domestic water use (and abuse) particularly valuable. Here's a brief example: The American obsession with lawns and lawn care products has come under scrutiny in recent years because of concerns about wasted water and the burdens of time, cost, and pollution that a well-manicured green lawn exacts from its owner and the natural environment (p.145). Vickers points out that lawn watering represents one of the biggest non-essential uses of water in many communities as well as the fact that keeping a lawn green with no brown spots during midsummer is often a costly, losing battle, even with regular

Agroeconomic Analyses of Drip Irrigation for Sugarbeet Production

Sugarbeet (Beta vulgaris L.) is a major cash crop in Wyoming where overuse of water and agrochemicals is a concern in furrow‐irrigated areas. Drip irrigation, an alternative technology, is not well developed for row crops within the state. Therefore, our objective was to evaluate the economic feasibility of implementing drip irrigation practice for sugarbeet production. Capital budgeting analyses, including net present value (NPV) and rate of return (ROR), were used for 10 to 40 ha. Sensitivity analyses were conducted with drip system size and life span, interest rate, water price, and weed control cost. Sugarbeet and sugar yields were higher under drip irrigation than furrow irrigation at P = 0.05. The drip system investment cost decreased with increasing size. Total variable costs for drip irrigation were lower than those for furrow irrigation. Sugarbeet returns were $2080 and $2310 ha−1 for furrow and drip irrigation practices, respectively. Higher returns and shorter payback time were observed for large conversion areas. The sensitivity was more pronounced with small‐scale farming. Increasing interest rates caused delays in positive return and profit and contributed to larger differences in payback time between drip system sizes. For all conversion sizes, ROR increased with system lifetime. Higher profitability was observed for areas with increased water prices and weed control costs. The overall findings indicated that sugarbeet production under drip irrigation would be most profitable for a 40‐ha area with payback periods ranging from 7 to 10 yr.

Repair and replacement of reactor internals for plant life extension

Recent experience from early Swedish BWRs corroborate that all components in a nuclear power plant can be repaired or replaced with new ones. Oskarshamn 1 has gone through a thorough refurbishment project. A number of internals were repaired or replaced including the core shroud support which was welded to the bottom of the reactor pressure vessel. The project verifies that it is fully possible to carry out complicated inspection and repair work inside a nuclear pressure vessel which has been in operation for more than 20 years. Along with increased capacity factor, operating nuclear power plants get the financial conditions needed for extensive repair and modernization projects. Large power output leads to short pay-back times for the investments. The FENIX project at Oskarshamn 1 is such a project. There are utilities whose policy is to keep their plants in as-new condition for an unlimited length of time.

Model-based control of a partial burn fluid catalytic cracking unit

A dynamic matrix controller (DMC) has been successfully installed on the fluid catalytic cracking reactor/regenerator section at RVI's Vohburg Refinery in Germany. A very short payback time was achieved based on increased feed processing and more stable regenerator operations (reduced catalyst addition rates). The controller has 6 inputs (manipulated variables) and 13 outputs (controlled variables). The application provides an excellent example of the importance of controlling processes at constraint limits. From the initial day of commissioning, the controller has stayed online and sustained a service factor of between 95% and 98% over an 11 month operating period. The limiting factor at the moment is the performance of the CO analyser. The controller has proved to be robust and operated well with constraints; it has handled disturbances effectively.

Residential cool storage: peak load reduction alternatives

The authors investigate alternatives for achieving a peak load reduction in the residential airconditioning sector from a technical and economic point of view. Several thermal energy storage technologies are assessed, considering different types of houses and storage schemes. If the utility offered an incentive of $300-400/kW of deferred peak, residential thermal energy storage would have a short payback time for new installations. The payback time for retrofits is unacceptable. Two-stage evaporative coolers can reduce peak power by 60%, with an extra cost of about one-fifth that of new peaking facilities. They can totally replace conventional air conditioning in some climates without any loss of comfort. High efficiency air conditioners can also reduce peak power but their incremental cost over standard units is higher than that of new peaking facilities.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Laboratory Computers: Tools for Increased Productivity

Revolutionary changes in the computer industry brought about in part by the introduction of personal computers are now reaching into clinical laboratories everywhere. Although the true justification for any computer tool may be an intangible one such as improvement in service, such tools can typically be cost justified by increases in productivity alone. A broad spectrum of applications software useful in the medical laboratory is now available in any scale required to meet the needs of any size of laboratory. Perhaps one of the most dramatic changes in this field in the last several years has been the introduction of small-scale integrated laboratory systems that are true small-scale laboratory information systems. As a result, smaller laboratories can now acquire laboratory information systems appropriately scaled to their workload for a fraction of the cost of the large systems. These small laboratory information systems are typically more easily cost justified than larger ones. Achieving productivity gains using computer tools in the laboratory is a management-intensive process requiring careful analysis and thorough planning. Laboratory managers who eschew computer tools are now an anachronism; extinction of this species is imminent.