Energy efficiency investments in Kraft pulp mills given uncertain climate policy

Energy efficiency measures in pulp mills can potentially reduce the consumption of biofuel, which can instead be exported and used elsewhere. In this paper a methodology is proposed for analysing the robustness of energy efficiency investments in Kraft pulp mills or other industrial process plants equipped with biofuelled combined heat and power units, given uncertain future climate policy. The outlook for biofuel and electricity prices is a key factor for deciding if energy efficiency measures are cost competitive. CO ₂ emission charges resulting from climate policy are internalized and thus included in electricity and biofuel prices. The proposed methodology includes a price-setting model for biofuel that assumes a constant price ratio between biofuel and electricity in the Nordic countries. Thirteen energy efficiency retrofit measures are analysed for an existing Swedish Kraft pulp mill. Special attention is paid to heat-integrated evaporation using excess process heat. Four possible energy market development paths are considered that reflect different climate policies. Pulp mill energy efficiency investments considered are shown to be robust with respect to uncertain climate policy. Copyright © 2006 John Wiley & Sons, Ltd.     

Analysis of energy efficiency and carbon dioxide reduction in the Chinese pulp and paper industry

Pulp and paper production, an energy-intensive process, is among the main light industries contributing to energy saving and pollution emission reduction in China. The improvement of energy efficiency is essential for energy consumption and sustainable development. This study analyzes the negative factors in the pulp and paper sector by calculating energy efficiency from the lengthways time and investigating the gap between China and foreign countries through a horizontal comparison. Accordingly, energy efficiency has increased in the Chinese pulp and paper industry with years of efforts, but its transformation remains unclear. Furthermore, the energy-saving potential, energy cost saving, and carbon dioxide emission reduction in the pulp and paper industry are evaluated according to the Twelfth Five-year Plan (2011–2015). The results show that the pulp and paper industry has further capabilities for energy-saving and carbon dioxide emission reduction by improving energy efficiency in China, resulting in great economic benefit. In brief, new technology and energy structure adjustment are long-term strategies for energy conversation, with changes in the scale of mills expected to provide huge opportunities to improve energy efficiency in China within a short period.     

Excess heat from kraft pulp mills: Trade-offs between internal and external use in the case of Sweden—Part 1: Methodology

Excess heat from a kraft pulp mill can be used either internally to increase the level of efficiency in the mill, or externally for example as district heating. This paper presents an approach to investigate the competition between external and internal use through modelling the pulp mill and an energy company (ECO) within the same system boundary. Three different sizes of ECOs with different district heating demands are studied. To investigate the competitiveness of using industrial excess heat as district heating compared with other heat production techniques, the option of investing in excess heat use is introduced, along with the possibility for the ECO to invest in biomass combined heat and power (CHP), waste CHP and natural gas combined cycle (NGCC). To evaluate the robustness of the model, alternative solutions are identified and will be used as a comparison to the optimal solutions. The model has been verified by comparing the results with previous studies concerning kraft pulp mills and with related studies regarding district heating and real ECOs. Finally, the approach presented in this part of the study will be used in the second part in order to investigate the trade-off between internal and external use of excess heat under different future energy market scenarios.     

Excess heat from kraft pulp mills: Trade-offs between internal and external use in the case of Sweden—Part 2: Results for future energy market scenarios

In this paper the trade-off between internal and external use of excess heat from a kraft pulp mill is investigated for four different future energy market scenarios. The work follows the methodology described in Svensson et al. [2008. Excess heat from kraft pulp mills: trade-offs between internal and external use in the case of Sweden—Part 1: methodology. Energy Policy, submitted for publication], where a systematic approach is proposed for investigating the potential for profitable excess heat cooperation. The trade-off is analyzed by economic optimization of an energy system model consisting of a pulp mill and an energy company (ECO). In the model, investments can be made, which increase the system's energy efficiency by utilization of the mill's excess heat, as well as investments that increase the electricity production. The results show that the trade-off depends on energy market prices, the district heating demand and the type of existing heat production. From an economic point of view, external use of the excess heat is preferred for all investigated energy market scenarios if the mill is studied together with an ECO with a small heat load. For the cases with medium or large district heating loads, the optimal use of excess heat varies with the energy market price scenarios. However, from a CO₂ emissions perspective, external use is preferred, giving the largest reduction of global emissions in most cases.     

Exergy analysis of a pulp and paper mill

Different energy and exergy concepts and methods are presented and applied to a Swedish pulp and paper mill. Flow diagrams show that the exergy content is mostly much less than the energy content of the flows. The largest exergy losses appear in the boilers. Heating processes are highly exergy inefficient. A limited Life Cycle Exergy Analysis (LCEA) shows that the exergy output amounts to over 3 times the spent exergy as non‐sustainable resources. By replacing the present use of non‐sustainable resources, mostly fuel oil, the mill could move towards a truly sustainable process. Copyright © 2005 John Wiley & Sons, Ltd.     

Policy issues in improving energy efficiency

Today many urgent policy issues need addressing within the overall topic of improving energy efficiency. Also, they need to be addressed at many levels in society, each level possibly requiring a different approach: the overall national economy; the national energy sector; the energy utility; and the energy consumer. This article looks at some of the more important common issues, which apply at all levels, and gives some options on how these issues might be addressed.     

Integration of absorption heat pumps in a Kraft pulp process for enhanced energy efficiency

A preliminary feasibility study of the implementation of various absorption heat pump configurations in a Kraft pulping process has been performed. Three different cases were considered: (i) integration of a double lift heat transformer into the heat recovery circuit of the wood chips digesters to produce low pressure steam equivalent to 25% of the steam demand of the chemical pulping plant, (ii) a double effect chiller installed in the bleaching chemicals making plant to chill cooling water and produce middle pressure steam and, (iii) a heat pump installed on the steam extraction line of a turbine which, combined with the addition of a condensing unit, increases substantially the power output. The simple payback time and net present value were used to compare the three cases. Both indices are highly dependant upon steam prices. The net present value is, in all cases, positive, which indicates that the equipment is viable using the assumed cost and efficiency data in this study. Absorption heat pumps are increasingly attractive options for energy upgrading and conversion in a context of increasing energy costs.     

Comparison of performance of heat regenerators: Relation between heat transfer efficiency and pressure drop

Heat regenerators transfer heat from one gas to another, with an intermediate storage in solids. The heat transfer surface for gas flow application should provide at the same time high surface area and low friction factor. Three geometries of heat transfer surface, monolith, stack of woven screens and bed of spheres, have been compared. Their performance was evaluated from the pressure drop of the heat regenerator working at a given heat transfer efficiency. The comparison was performed using numerical simulation and published measurements of heat transfer and flow friction characteristics. By adjusting the length and the period of the exchanger, it is possible to obtain the same heat transfer efficiency with the three geometries. Beds of spheres give very short and compact heat regenerators, working at high pressure drop. At the opposite, monoliths form long regenerators working at low pressure drop. Stacks of woven screens cover a wide range of performance: low porosity woven screens give high heat transfer efficiency and high pressure drop, while high porosity woven screens offer performance similar to that of the monoliths. Copyright © 2001 John Wiley & Sons, Ltd.     

Systems interactions analysis for the energy efficiency improvement of a Kraft process

Several techniques are available to improve the energy performance of a process (internal heat recovery, water reutilization, condensates return, energy upgrading and conversion, elimination of non-isothermal mixing). They are applied to specific energy systems on the utility or process side (steam production and distribution, hot or cold water networks, process heat sources and sinks). Since those systems are interconnected, actions taken on one of them may have effects on another. These effects can be positive (synergies) or negative (counter-actions). A systematic, stepwise methodology has been developed to ensure that synergies are exploited and counter-actions avoided, and is presented. It has been validated by application to an existing Kraft pulping mill. Key performance indicators and the evolution of the thermal composite curves were used to monitor progress as the successive steps of the methodology were implemented. It was found that the combined direct and indirect effects of water reutilization constituted the most important source of potential energy savings. Water reutilization also reduced the need for additional purchased heat exchanger area. Overall, the water intake by the mill could be reduced by 33% and steam savings could be 26% of current production. This would liberate sufficient steam production capacity for the installation of a 44.4 MW cogeneration unit.     

Energy flow analysis in pulp and paper industry

This work analyzed the energy flow of the pulp and paper industry in Taiwan. The potential technology options that were examined focus on how to capture some of the energy currently lost in the processes and then identifying the areas with energy-saving potential that could also have large impacts across a variety of industries. In addition, the energy-saving potential of these options was evaluated. The energy-saving potential of the pulp and paper industry would be around 6939.9 KLOE/M. The greatest energy-saving potential lies with improving energy distribution and equipment efficiency, which would together potentially comprise 86.8% of total energy conservation. This analysis can serve as a benchmark for current pulp and paper making operations, and as a base case for stimulating changes toward more efficient energy utilization in the pulp and paper industry.     

Opportunities for the integration of absorption heat pumps in the pulp and paper process

Implementation of absorption heat pumps (AHPs) in a Kraft pulping process was studied using a new methodology for the optimal integration of those devices in a process. Two generic opportunities were identified for an energy and water optimized mill: (i) integration of a double lift chiller in the bleaching chemical making plant to produce chilled and hot water simultaneously, using MP steam as the driving energy and, (ii) installation of a single stage heat pump to concentrate the black liquor and produce useful hot water by upgrading heat from the bleaching effluent and using MP steam as driving energy. The principles of AHPs operation and their efficient integration into a process are described. The simple payback time (SPB) and net present value (NPV) were used to evaluate the interest of such implementations. Considering 63 $/MWh for the steam price, SPB of 2.7 and 1.7 years have been estimated for the two cases.     

Cogeneration potential in pulp and paper industry of Vietnam

This paper analyses the economics of cogeneration potential in the pulp and paper industry of Vietnam. The analysis focuses on six large existing paper mills, their planned capacity expansion and nine planned new mills up to 2010. The analysis considered five alternative fuels (coal, diesel, fuel oil, natural gas and rice husk), three different technologies (steam turbines, gas turbines and reciprocating engines) and two modes of operation (thermal match and power match) of cogeneration. It also considered the case of sale of excess power to the grid. The analysis indicates that cogeneration is a viable option in the paper and pulp industry in Vietnam and the potential is about 200 MW. IRR in most of the cases ranges between 15 and 30% and the general payback period is between 3 and 5 years. Cogeneration remains a viable option even without sale of power to the grid and under different unfavourable conditions of fuel price, investment and other factors. Copyright © 2005 John Wiley & Sons, Ltd.     

Energy storage efficiency for the ammonia/hydrogen-nitrogen thermochemical energy transfer system

Energy storage efficiency is calculated for the solar thermochemical energy transfer system based on ammonia/hydrogen-nitrogen. the calculation for this system involves generation of thermodynamic data not available in the literature by a method in which use is made of the available phase equilibrium measurements together with application of the criterion that the correct value of separation work for a two-phase mixture must be generated internally by degradation of mixing heat. Energy storage efficiencies for ammonia/hydrogen-nitrogen are derived from the generated thermodynamic data and are shown to increase towards unity as the endothermic reaction approaches completion, with efficiencies greater than 0.90 being obtained for reaction extents exceeding 0.60. the validity of the analysis has been tested successfully by comparison between the thermodynamic predictions and experimental data in the form of measurements of the waste heat rejected from a counterflow heat exchanger operated with liquid ammonia feed and ammonia/hydrogen-nitrogen output.     

The value of flexibility for pulp mills investing in energy efficiency and future biorefinery concepts

Changing conditions in biomass and energy markets require the pulp and paper industry to improve energy efficiency and find new opportunities in biorefinery implementation. Considering the expected changes in the pulp mill environment and the variety of potential technology pathways, flexibility should be a strong advantage for pulp mills. In this context, flexibility is defined as the ability of the pulp mill to respond to changing conditions. The aim of this article is to show the potential value of flexibility in the planning of pulp mill energy and biorefinery projects and to demonstrate how this value can be incorporated into models for optimal strategic planning of such investments. The paper discusses the requirements on the optimization models in order to adequately capture the value of flexibility. It is suggested that key elements of the optimization model are multiple points in time where investment decisions can be made as well as multiple scenarios representing possible energy price changes over time. The use of a systematic optimization methodology that incorporates these model features is illustrated by a case study, which includes opportunities for district heating cooperation as well as for lignin extraction and valorization. A quantitative valuation of flexibility is provided for this case study. The study also demonstrates how optimal investment decisions for a pulp mill today are influenced by expected future changes in the markets for energy and bioproducts. Copyright © 2014 John Wiley & Sons, Ltd.     

A model for improving energy efficiency in industrial motor system using multicriteria analysis

In the last years, several policies have been proposed by governments and global institutions in order to improve the efficient use of energy in industries worldwide. However, projects in industrial motor systems require new approach, mainly in decision making area, considering the organizational barriers for energy efficiency. Despite the wide application, multicriteria methods remain unexplored in industrial motor systems until now. This paper proposes a multicriteria model using the PROMETHEE II method, with the aim of ranking alternatives for induction motors replacement. A comparative analysis of the model, applied to a Brazilian industry, has shown that multicriteria analysis presents better performance on energy saving as well as return on investments than single criterion. The paper strongly recommends the dissemination of multicriteria decision aiding as a policy to support the decision makers in industries and to improve energy efficiency in electric motor systems.     

An analysis of the heat transfer rate and efficiency of TE (thermoelectric) cooling systems

The heat transfer rate and efficiency of TE (thermoelectric) cooling systems were investigated. The emphasis of the present study is focused on the use of large-scale TE refrigerators for air conditioning applications. A one-dimensional heat transfer analysis was performed to determine the cooling power and electricity consumption of the TE elements. The constant-property results are in good agreement with the variable-property solutions for TE materials and temperatures typical for air conditioning applications. A heat transfer analysis was also carried out for TE refrigerators equipped with a heat exchanger. Both parallel- and counter-flow heat exchangers were considered. Fluid temperature variations of these two flow arrangements were found to be quite different, but the efficiencies and cold fluid exit temperatures differed only slightly when a uniform current was used for all TE elements. If the length of the heat exchanger exceeds an optimal value, the cold fluid temperature begins to rise and the efficiency drops for both parallel- and counter-flow arrangements. The second law of thermodynamics was applied to the optimization of TE refrigerators operating between two constant-temperature reservoirs and between two flowing fluids. It was found that if a TE cooling system incorporates a heat exchanger, a nonuniform current distribution should be used to achieve the maximum efficiency and the lowest cold fluid temperature. The optimization results for TE refrigerators operating between two constant-temperature reservoirs are not applicable to TE cooling systems between two flowing fluids. The most energy-efficient current distribution for the parallel-flow arrangement is the one which increase in the direction of the cold fluid.     

Dedicating new real estate transfer taxes for energy efficiency: A revenue option for scaling up Green Retrofit Programs

As the labor market in the U.S. remains weak, with high unemployment and sluggish job growth, policymakers at various levels of government are looking for new ways to support job growth and investment during an increasingly tight fiscal climate. Policies that promote the “Green Economy” in general and energy efficiency in particular remain politically popular as potential win–win solutions that will create jobs and curb greenhouse gas emissions. Yet, efforts to promote energy efficiency in the residential sector through rebates and incentives alone have yet to reach critical mass. This paper outlines a policy option for state and local governments to use real estate transfer taxes to generate stronger incentives for home buyers to undertake significant retrofit projects at the time of sale. The economic impact of the proposed energy efficiency transfer tax (EETT) is then modeled for the State of North Carolina, using standard input–output techniques. Ultimately, based on housing sales figures from 2010, a new EETT of 2.5 percent on home purchases would generate a net positive increase of approximately 3485 direct construction jobs and 5900 annually total jobs for the state.     

Theoretical and experimental study of efficiency factor,heat transfer and thermal heat loss coefficients in solar air collectors with selective and nonselective absorbers

The thermal heat performance of a solar air collector depends strongly on the thermal heat loss and the efficiency factor. In order to increase these performances, it is necessary to use a solar air collector which is well insulated and where the fluid flow is fully developed turbulent flow. It needs a high heat transfer between the absorber plate and the fluid to decrease the absorber‐plate temperature and hence the heat loss by radiation from the absorber to the ambient. This increases the efficiency factor. In the present paper, the heat loss and efficiency factor are treated for solar air collectors with selective and nonselective absorber plate. It is shown that the selectivity of the absorber plate cannot play an important role in a well‐insulated solar collector with a fanned system which permits a fully developed turbulent flow and, in consequence, high heat transfer. Copyright © 1999 John Wiley & Sons, Ltd.     

壳管式相变蓄热器传热效率研究

设计了一套定量测试不同工况下壳管式相变蓄热器传热效率装置。采用壳管式相变储热,石蜡填充入壳管间,管内通入冷、热载流体,模拟吸热放热过程。测试发现:相同入口条件下,单位时间传热量随入口水温增加呈线性增加;管内载流体流量加大有助于提高传热水平,15~60 L/h流量内单位时间传热量增速随流量增加放缓;不同材质传热管单位时间传热量变化并不明显,表明管道热阻在相变蓄热器总热阻中所占份额较小;相同工况下的蓄热过程,热载流体由下向上流动传热形式明显优于由上向下管排形式;尝试在封装相变材料中添加金属网状结构,强化相变材料内部热传导速率,对比发现相同工况下相变材料中添加金属网状结构,可提高10%~15%左右传热量。     

Sensitivity analysis of investments in the pulp and paper industry On investments in the chemical recovery cycle at a board mill

In the pulp and paper industry, energy costs represents a relatively large proportion of the value of production. When investing in new equipment, considerations concerning boundary conditions, such as electricity and oil prices, are therefore of great importance. A vital requirement is the identification of other key parameters influencing production costs as well as possible interaction between these parameters. In this paper, a sensitivity analysis is accomplished by using an optimization model that minimizes the system cost combined with a systematic approach involving a statistical method. The paper analyses the possibilities of investing in a new chemical recovery cycle, including a new recovery boiler and evaporation plant, at a Swedish board mill. The study includes a survey of future changes, together with forecasts of boundary conditions, such as changes in the price of electricity and oil. Interactions between different parameters are also examined. Copyright © 2002 John Wiley & Sons, Ltd.