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The required level of a sector specific CO2e-cost in the transport sector to make the net annual profit (NAP) of three different gasification based biofuel production systems positive (systems profitable) is investigated. The analysis is made for two different energy market scenarios for 2030 and 2040. The results show that the additional required sector specific CO2e-cost (additional to a sector wide general cost) is not higher than the current level of CO2e-tax in Sweden. The required total level of CO2e-cost for the transport sector is in the 450 ppmv scenario in general higher than the current CO2-tax level but not higher than the fuel tax level (including also energy tax). The study also compares the NAP and greenhouse gas (GHG) emission reduction potential of the gasification-based systems to a system where the biomass is used in conventional bio-CHP to produce heat and power and where the power is used in the transport sector (in battery electric vehicles (BEV)). Under the investigated energy market scenarios the bio-CHP and BEV system has higher NAP and higher GHG emission reduction potential. However, the bio-CHP system has a stronger dependency on the availability of large heat sinks and profits from a high price of delivered heat.

In this paper, two ethanol processes integrated with a softwood pulp mill are compared with regard to their steam demand, process integration potential and profitability. The processes differ in the solids loading in the simultaneous saccharification and fermentation step and in the resulting ethanol concentration. The results show that a higher ethanol concentration does not necessarily lead to significant reductions in steam demand. Instead, it is demonstrated that the steam demand for distillation is highly dependent on the design of the distillation plant. Nevertheless, a higher solids loading (high gravity) can be beneficial for the treatment of the stillage from the distillation plant. A higher solids loading results either in a lower steam demand for evaporation of the stillage or possibly in a reduced demand for effluent treatment compared to a conventional solids loading process. While the results show that a higher ethanol concentration leads to advantages in energy costs and investment costs for the distillation plant, they also show that the potential benefits of a high-gravity process are offset by the expected decrease in ethanol yield, which leads to higher raw material costs. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Production of transportation fuels from biorefineries via biomass gasification has been suggested as a way of introducing renewable alternatives in the transportation system with an aim to reduce greenhouse gas emissions to the atmosphere. By co-locating gasification-based processes within heat demanding industries, excess heat from the gasification process can replace fossil or renewable fuels. The objective of this study was to compare the heat integration potential of four different gasification-based biorefinery concepts with a chemical pulp and paper mill. The results showed that the choice of end product which was either methanol, Fischer-Tropsch crude, synthetic natural gas or electricity, can have significant impact on the heat integration potential with a pulp and paper mill and that the heat saving measures implemented in the mill in connection to integration of a gasification process can increase the biomass resource efficiency by up to 3%-points. Heat saving measures can reduce the necessary biomass input to the biorefinery by 50% if the sizing constraint is to replace the bark boiler with excess heat from the biorefinery. A large integrated gasification process with excess steam utilisation in a condensing turbine was beneficial only if grid electricity is produced at below 30% electrical efficiency.

This paper presents a comparison between four gasification-based biorefineries integrated with a pulp and paper mill. It is a continuation of 'Transportation fuel production from gasified biomass integrated with a pulp and paper mill - Part A: Heat integration and system performance'. Synthesis into methanol, Fischer-Tropsch crude or synthetic natural gas, or electricity generation in a gas turbine combined cycle, were evaluated. The concepts were assessed in terms of GHG (greenhouse gas) emissions and economic performance. Net annual profits were positive for all biofuel cases for an annuity factor of 0.1 in the year 2030; however, the results are sensitive to biofuel selling prices and CO2,eq charge. Additionally, GHG emissions from grid electricity are highly influential on the results since all biofuel processes require external power. Credits for stored CO2 might be necessary for processes to be competitive, i.e. storage of separated CO2 from the syngas conditioning has an important role to play. Without CO2 storage, the gas turbine case is better than, or equal to, biofuels regarding GHG emissions. Efficiency measures at the host mill prior to heat integration of a gasification process are beneficial from the perspective of GHG emissions, while having a negative impact on the economy.

Carbon capture and storage may, as a bridging technology, rapidly decrease CO2 emissions in the industrial sector. In this paper, a techno-economic study of a future MEA carbon capture plant implemented at a case study oil refinery is presented. Costs are calculated for six setups of carbon capture at the refinery. Excess heat from the refinery processes is used in the capture plant for regeneration of the absorption fluid, and the stripper reboiler temperature is varied to increase the extractable of excess heat. Supplementary heating is carried out with a heat pump. The number of chimneys to be included in the capture process is also varied, resulting in different CO2 concentrations and amounts of CO2 at the inlet of the capture plant. Results show that the specific cost for carbon capture increases as the amount of captured carbon increases due to the need for heat pumps. The costs are in the range of 41-57(sic)/t for the low-temperature cases (T-Reb =90 degrees C) and 39-44(sic)/t for the high-temperature cases (T-Reb = 120 degrees C).

This study analyses the impact on the GHG (greenhouse gas) emissions of the raw material supply chain, the utilisation of excess heat and CO2 storage for a bio-SNG (biomass gasification-based synthetic natural gas) system by applying a consequential life cycle assessment approach. The impact of the biomass supply chain is analysed by assessing GHG emissions of locally produced woodchips and pellets with regional or transatlantic origin. Results show that the supply area for the gasification plant can be substantially increased with only modest increases in overall GHG emissions (3-5%) by using regionally produced pellets. The transatlantic pellet chains contribute to significantly higher GHG emissions. Utilising excess heat for power generation or steam delivery for industrial use contributes to lower emissions from the system, whereas delivery of district heating can contribute to either increased or decreased emissions. The production technology of the replaced heat and the carbon intensity of the reference power production were decisive for the benefits of the heat deliveries. Finally, the storage of CO2 separated from the syngas upgrading and from the flue gases of the gasifier can nearly double the GHG emission reduction potential of the bio-SNG system. (C) 2015 Elsevier Ltd. All rights reserved.

In industrial processes, heat is transferred from the heating utilities to the environment or converted to another form of energy. Process operations and heat exchanges decrease the level of energy quality; i.e., heat is cascaded to lower temperatures. The energy transfer diagram (ETD), which has been recently developed, indicates the flow rate of heat transferred from the utilities to the environment through each process operation and each heat exchanger as a function of temperature. This tool can be used to identify heat savings projects by modification of the process units and the heat-exchanger network (HEN). However, in a larger sense the diagram indicates the flow rate of energy transferred through any system as a function of the level of energy quality, and can be used for the analysis of a complete plant, including the thermal, chemical, mechanical and electrical transformations. This paper presents new developments to consider energy conversion with the ETD, the application to an entire kraft pulp mill, including the HEN, the process operations, and the utility system, and results from site-wide analysis.

Pinch analysis is based on the hot, cold and grand composite curves and is the most commonly-used approach to identify strategies for reducing energy consumption by heat exchanger network retrofit. This method was originally developed for the synthesis of new networks, and there remain certain difficulties for its application to improve existing networks. The advanced composite curves have been developed for retrofit situations specifically, and use data about existing heat exchangers to provide more information about the modifications necessary to achieve heat savings. Bridge analysis, which is based on the energy transfer diagram, is a new method and enumerates the sets of heat transfer modifications necessary to save energy. In this paper, the grand composite curve, the advanced composite curves and the energy transfer diagram have been constructed for analysis of the heat exchanger network of a kraft pulp mill. Links between these methods are made explicit; then results are discussed and compared. It is shown that the information provided by these approaches is consistent; however, the level of detail progressively increases from the grand composite curve to the advanced composite curves until the energy transfer diagram. Fundamentally, reducing the energy consumption implies decreasing the flow rate of heat cascaded through the network from the hot utility until the environment. As a consequence, any heat savings solution includes network modifications bridging coolers to heaters. Traditional pinch analysis does not provide information about the network modifications required after removal of cross-pinch transfers, while the advanced composite curves indicate the heat savings potential attainable through modifications of few existing heat exchanger units. Bridge analysis provides more detail about heat savings modifications, which bridge existing heaters and coolers, than traditional pinch analysis and the advanced composite curves do.

This study evaluates the potential for reducing life cycle greenhouse gas (GHG) emissions of biomass gasification-based methanol production systems based on energy balances. Configurations which are process integrated with a chemical cluster have been compared to stand-alone units, i.e. units with no connection to any other industry but with the possibility to district heating connection. Two different uses of methanol are considered: the use as a vehicle fuel and the use for production of olefins via the methanol-to-olefins process. An added value of the integration can be the availability of excess hydrogen. For the studied case, the methanol production could be increased by 10% by using excess hydrogen from the cluster. The results show that the integrated systems have greater potential to reduce GHG emissions than the stand-alone systems. The sensitivity analysis demonstrated that the references for electricity production and district heating production technology have important impacts on the outcomes. Using excess heat for district heating was found to have positive or negative impacts on GHG emissions depending on what heat production technologies it replaces. The investigated olefins production systems resulted in GHG emissions reductions that were similar in magnitude to those of the investigated biofuel production systems.

The implementation of post-combustion CCS provides an opportunity for the oil refining sector to drastically decrease its CO2 emissions. Previous studies have shown that the largest cost is the heat supply to the stripper reboiler. When performing CCS at an oil refinery it could therefore prove economically beneficial to utilize the excess heat from refinery processes to meet this demand for heat. The present study investigates the heat demand in a stripper reboiler at different temperature levels from 120 degrees C down to 90 degrees C. At temperatures lower than 120 degrees C the heat demand increases, but the availability of excess heat also increases. A case study that connects heat demand results with data from an oil refinery shows that if only excess heat is utilized as a heat source, the amount of CO2 that can be separated is largest when the temperature in the stripper reboiler is 90 degrees C. If, however, CCS with a capture rate of 85% were applied to the four largest chimneys at the refinery, the external heat demand would be the lowest for the standard temperature of 120 degrees C. (C) 2013 Elsevier Ltd. All rights reserved.

A key issue in post-combustion carbon capture is the choice of absorbent. In this paper two different absorbents, monoethanolamine (MEA) and ammonia (NH3), have been modeled in Aspen Plus at different temperatures for possible implementation at an oil refinery. The focus of investigation is the possibilities of heat integration between the oil refinery and the carbon capture process and how these possibilities could change in a future situation where energy efficiency measures have been implemented. The results show that if only using excess heat from the refinery for heating of the carbon capture process, the MEA process can capture more CO 2 than the NH3 process. It is shown that the configuration requiring least supplementary heat when applying carbon capture to all flue gases is MEA at 120 °C. The temperature profile of the excess heat from the refinery suits the MEA and NH3 processes differently. The NH3 process would benefit from a flat section above 100 °C to better integrate the heat needed to reduce slip, while the MEA process only needs heat at stripper temperature.

Integration of biomass gasification with a pulp and paper mill is a possible route to create more value-added products. This route facilitates, for example, more advanced electricity generation and production of biomass based transportation fuels or chemical feedstock. Each unit operation in such a process affects overall efficiency as well as possibilities for process integration. In this paper, the impact of different dryer types in a biomass gasification combined cycle (BIGCC) has been evaluated in terms of efficiency and economic performance. The BIGCC was sized so that the excess heat would replace the current steam production from bark and oil. The results show that the dryer type can have a significant impact on economic performance and efficiencies. A BIGCC with an integrated belt dryer, utilizing excess heat to heat the drying air from the mill, can result in electrical efficiencies of up to around 40%, while e.g. a steam dryer can reach 36–37%. Choice of oxidant, air or oxygen, in the gasifier affects both capital and operational cost. Air was proven to be the most cost efficient solution for the cases evaluated in this study. The investment of around 100 to 140 million Euros for a BIGCC facility is profitable for most evaluated cases for an annuity factor of 0.1, while the net annual profit is negative for most cases when the annuity factor was increased to 0.2, even when including financial support for renewable electricity.

The impact on CO2 emissions of integrating new technologies (a biomass-to-Fischer-Tropsch fuel plant and a post-combustion CO2 capture plant) with a complex refinery has previously been investigated separately by the authors. In the present study these designs are integrated with a refinery and evaluated from the point-of-view of economics and GHG (greenhouse gas emissions) emissions and are compared to a reference refinery. Stand-alone Fischer-Tropsch fuel production is included for comparison. To account for uncertainties in the future energy market, the assessment has been conducted for different future energy market conditions. For the post-combustion CO2 capture process to be profitable, the present study stresses the importance of a high charge for CO2 emission. A policy support for biofuels is essential for the biomass-to-Fischer-Tropsch fuel production to be profitable. The level of the support, however, differs depending on scenario. In general, a high charge for CO2 economically favours Fischer-Tropsch fuel production, while a low charge for CO2 economically favours Fischer-Tropsch fuel production. Integrated Fischer-Tropsch fuel production is most profitable in scenarios with a low wood fuel price. The stand-alone alternative shows no profitability in any of the studied scenarios. Moreover, the high investment costs make all the studied cases sensitive to variations in capital costs. (C) 2013 Elsevier Ltd. All rights reserved.

The application of post-combustion CO2 capture represents an alternative strategy to reduce significantly CO2 emissions from the oil refining industry. Previous studies have shown that the highest costs are related to the provision and use of energy and that these costs could be reduced by utilising excess heat. In the present study, we investigated whether this principle could be applied to the oil refining industry. Four heat supply alternatives were evaluated: Natural Gas Combined Cycle; Natural Gas Boiler; Biomass Boiler; and Excess Heat. These alternatives were evaluated using future energy market scenarios and two levels of heat demand. The Natural Gas Combined Cycle alternative generated high levels of electricity (with CO2 capture), thereby producing the greatest reduction in global CO2 emissions. However, the avoided CO2 emissions from onsite the refinery were highest when excess heat or a biomass boiler was used. In the present study, the capture avoidance cost ranged from 40 to 263 (sic)/tCO(2) avoided (excluding transportation and storage costs), depending on the heat supply alternative used and the heat demand. Moreover, with a high cost for CO2, CO2 capture using excess heat could be a cost-effective alternative to reduce CO2 emissions for oil refineries.

A conceptual biorefinery, based on repurposing a kraft pulp mill, has been studied. In the process an alkaline pre-treatment unit separates the incoming wood raw-material to a cellulose-rich pulp and a residue liquor containing dissolved lignin. The pulp is sent to an ethanol line, while the liquor is gasified and refined to dimethyl ether. The concept has been designed and assessed from an energy and economic point-of-view. The results of the study indicate that the process can be self-sufficient in terms of hot utility (fresh steam) demand. There will be a deficit of electricity, however. The economic assessment shows that the process can be feasible, but that the economic outcome is highly dependent on the development of biofuel prices, and if the investment in this type of biorefinery is seen as a high risk investment or not. It is also shown that CO2 capture and storage can be interesting in this type of biorefinery due to the low cost of capturing CO2 in the process.

A study has been conducted in ord er to investigate how the sp ecific heat requ irements in the stripp er reboiler of a M EA capture p lant changes with chan gin g temp erature. It was found that the increase in h eat demand is dr amatic when lowerin g the temp erature, ap p roximately 40% when the temp erature chan ges from 120 to 90° C. Heat integration with a ref inery was also studied, and showed that even if the heat demand was lar ger for the lower temp erature the heat integration p ossibilities were also larger for the base case.

While in a conventional kraft pulp mill, most of the hemicellulose and lignin fraction of the wood is burned in the recovery boiler to produce steam, in a biorefinery it can partially be used to produce added-value products. In this paper, the most important consequences of integrating a bioethanol production plant with a model pulp mill are presented in terms of steam and Na/S balances. The model mill represents an average Scandinavian hardwood kraft pulp mill, and the bioethanol plant is based on the "near-neutral" hemicellulose pre-extraction method. Regarding the steam balance, a comprehensive heat integration study is performed. Implementing hemicellulose extraction increases the net steam demand by 48 MW. However, process integration at the mill and the bioethanol plant individually leads to significant steam savings, and a corresponding net increase of steam by only 3 MW. Additional steam savings can be achieved if the total integration of the two processes (between the pulp mill and the bioethanol plant) is considered (3 MW), resulting in a biorefinery with no increase of steam demand. As regards the Na/S balance, it is shown that green liquor export from the mill to the bioethanol plant results in severe disruptions in the sodium and sulphur balance of the mill. Different attempts to solve this problem are discussed, but are very costly and/or negatively affect the water and steam balance of the mill.

In a previous study by the authors, energy efficiency measures in a conceptual kraft pulp mill converted to a lignocellulosic ethanol plant were investigated. The results suggested a number of different process designs which would give a substantial improvement in steam economy in the ethanol plant, compared to the original design. In the present study the different process designs are evaluated from an economic point-of-view, in order to determine if energy efficiency measures and increasing by-product sales decrease the production cost of ethanol from this specific process, or if the increased costs related to the implementation of these measures overshadow the benefits from increased by-product sales. The different energy efficiency measures are compared with less capital demanding alternatives (i.e. including low or no energy efficiency improvements) in order to assess the economic benefits of different strategies when converting a !craft pulp mill to ethanol production. The study indicates the economic importance of considering energy efficiency measures when repurposing a kraft pulp mill to an ethanol plant. It is also shown that, within the context of this study, a larger investment in measures will give better economic results than less capital demanding alternatives (with less improvement in energy efficiency). From an economic and energy efficiency viewpoint many of the suggested process designs will give approximately similar results, therefore the process design should be made based on other criteria (e.g. low complexity, low maintenance).

A systematic analysis of interrelations between different process steps in the biomass gasification and methanol synthesis chain was made. The energy performance of the system is assessed by reviewing previous studies and analysing a case study. Implications of technology choices and process integration opportunities are in focus. The case study analyses the impact on the energy balance of process-integrated drying compared to import of dried biomass, effects on electricity production due to heat pump integration or district heating (DH) delivery, effect on methanol yield of hydrogen addition and the impacts of adding an methanol-to-olefins (MTO) process. The biomass drying has significant impact on the overall energy balance, the cooling demand increases by 60% for the case study installation when process-integrated drying is not applied for drying the biomass. There is a trade-off between methanol yield, electricity and DH production potential of the system. Heat pumping can increase the electricity yield of the system. Hydrogen addition replacing the water gas shift can increase the methanol yield, in our case study by ∼35%, but in a stand-alone case the electricity demand makes such a system unrealistic. Adding an MTO unit to the system has limited impact on the energy balance.

The Scandinavian mechanical pulp and paper industry has been facing great challenges during the past decades, mainly because of declining demand for newsprint, and higher prices on raw material and energy. One way of increasing profitability is to produce more value-added products besides the production of pulp and paper. In this study, integration potentials of three possible future biomass gasification-based energy mills with an existing thermo-mechanical pulp (TMP) mill, co-located with a sawmill, have been evaluated. The product gas was utilized for electricity production in a gas turbine, for production of methanol or for production of Fischer–Tropsch (FT) liquids. Integration of the energy mills showed good potential as the TMP mill constitutes a heat sink for which the excess heat from the energy mills can be utilized all year round. However, since there is little excess heat from the TMP mill at the required level to be utilized for biomass drying, for example, heat integration is typically one way. It has also been shown that integration of biomass gasification with a TMP mill results in larger CO2 emissions reduction than stand-alone operation. Still, compared to co-firing biomass in a coal power plant, the energy mills all have lower potentials for CO2 emissions reduction.

In this paper an approach for analysing the potential for implementation of different technology pathways for the European pulp and paper industry (PPI) is presented. The approach is based on detailed technical research and aggregates the knowledge from previous studies to incorporate the whole European PPI. Thus, the potential for different technology pathways can be estimated on a European level whilst still considering important characteristics of individual mills. The usefulness of the approach was exemplified by applying it to a case study of the potential for introduction of carbon capture and storage (CCS) within the European PPI. The results from the case study show that for the European PM, CCS has an up-hill road in order to be a viable, large scale alternative for reduction of CO2 emissions. If CCS is to be introduced in large scale within the European PPI, large biomass-based point sources of CO2 emissions need to be included when planning for CCS infrastructure and also the infrastructure needs to be built out for clusters emitting

Petroleum oil refineries account for almost 8% of the total CO2 emissions from industry in the European Union (EU). In this paper, the European petroleum refining industry is investigated and the prospects for future CO2 abatement in relation to associated infrastructure are assessed. A more efficient use of the adjacent infrastructure, e.g., district heating networks, natural gas grids, neighbouring industries, and CO2 transport and storage systems, could provide opportunities for additional CO2 emissions reduction. It is shown that access to infrastructures that can facilitate CO2 abatement varies significantly across countries and between individual refineries. The assessment shows that short-term mitigation options, i.e., fuel substitution and energy efficiency measures, could reduce CO2 emissions by 9–40 MtCO2/year (6–26% of the total refinery emissions). It is further shown that carbon capture and storage offers the greatest potential for more significant emission reductions in the longer term. However, the potential for CO2 capture varies significantly depending on the choice of technology, CO2 source, and scope of implementation (5–80% of the total refinery emissions).

An economic analysis for post-combustion CO2 capture in a petrochemical industry has been performed. Previous studies have shown that the largest costs are related to the costs for energy supply. In this study we therefore focus on how heat can by supplied to the capture process in the most cost-efficient way. Five different heat supply options have been evaluated by using an energy market scenario tool together with a variation of the specific heat demand (reboiler duty). Three stand-alone options (natural gas combined cycle, natural gas boiler and biomass boiler) and two excess heat options (use of current excess heat and optimal use of excess heat) were analysed. For the stand-alone alternatives, the fuel consumption and co-generation of electricity are important. The best alternatives were the ones using excess heat. Considering that the process integration potential in the process industry generally is high and expecting high future CO2 charges, these options may become profitable. A quantification of the capture costs per CO2 avoided using excess heat shows costs in the range of 37-70(sic)/t CO2, which are comparable to costs reported for oxy-fuel combustion in petrochemical industries as well as for post-combustion in the power sector.

Energy efficiency is an important parameter for the profitability of biochemical ethanol production from lignocellulosic raw material. The yield of ethanol is generally low due to the limited amount of fermentable compounds in the raw material. Increasing energy efficiency leads to possibilities of exporting more by-products, which in turn might reduce the net production cost of ethanol. Energy efficiency is also an important issue when discussing the repurposing of kraft pulp mills to biorefineries, since the mills in question most likely will be old and inefficient. Investing in energy efficiency measures might therefore have a large effect on the economic performance. This paper discusses energy efficiency issues related to the repurposing of a kraft pulp mill into a lignocellulosic ethanol production plant. The studied process is a typical Scandinavian kraft pulp mill that has been converted to a biorefinery with ethanol as main product. A process integration study, using pinch analysis and process simulations, has been performed in order to assess alternative measures for improving the energy efficiency. The improvements found have also been related to the possibilities for by-product sales from the plant (electricity and/or lignin). In a forthcoming paper, which is the second part of this process integration study, an economic analysis based on the results from this paper will be presented.

In this paper, the global CO2 effect of integrating different biomass gasification concepts to meet an increasing demand of hydrogen in an oil refinery is examined and presented in comparison with a conventional steam reformer. The studied refinery is a hydro skimming refinery with a future hydrogen deficit of 16,000 Nm3/h. Three gasification concepts are considered: Entrained Flow (EF), Circulated Fluidised Bed (CFB) and Double Bed (DB). The system analysis is made with respect to global CO2 emissions and primary energy use. The results show that if biomass is considered as an unlimited resource (i.e. sufficient biomass is considered to be available to substitute for all fossil fuels in society), biomass gasification concepts have a potential to reduce CO2 emissions. The EF case shows the largest reduction potential. However, if biomass is considered as a limited resource (i.e. increased use of biomass at the refinery will lead to increased use of fossil fuel elsewhere in society), all concepts show an increase of CO2 emissions. Here, the CFB gasifier shows lowest increase of CO2 emission. The CO2 effect of the different alternatives shows sensitivity to assumptions regarding alternative biomass user.

In this paper, we propose a systematic approach to study how the development in terms of cost and proven functionality of emerging energy technologies affects the optimal choice and timing of investment decisions at an industrial plant today. The methodology used is based on stochastic programming, and all investments are optimized under uncertain energy market conditions. The cost development of the new technology is modeled using scenario analysis where both the cost levels and the timing of the market introduction are considered. Two examples are presented to illustrate the usefulness of the proposed approach. The examples are taken from the pulp and paper industry. In addition to investments in conventional technology for heat and/or power production, the emerging technology of carbon capture is considered as a possible future investment in the first example while lignin separation is considered in the second one. It is shown that possible future technologies can be highly important to consider already in today’s investment decisions.

Significant opportunities for energy savings have been identified in the hot and warm water system of a kraft pulp mill. The energy-saving opportunities found at the mill studied, 15.7 MW of steam savings and 24.8 MW of usable excess heat, correspond to 18% of the mill's total steam use. Short-term variations in the process have been studied in order to identify and quantify the influence of these variations on the energy-saving opportunities. Daily and 10-min averages of measured data were used as varying input data in the retrofitted heat exchanger network. When the short-term variations were considered, the total energy-saving opportunities fell by 8% when daily averages are used and by 11% when 10-min averages are used. At least 65% of the influence of short-term variations was detected when seasonal variations are considered. (C) 2010 Elsevier Ltd. All rights reserved.

In this paper we present a systematic approach for taking into account the resulting CO2 emissions reductions from investments in process integration measures in industry when optimizing those investments under economic uncertainty. The fact that many of the uncertainties affecting investment decisions are related to future CO2 emissions targets and policies implies that a method for optimizing not only economic criteria, but also greenhouse gas reductions, will provide better information to base the decisions on, and possibly also result in a more robust solution. In the proposed approach we apply a model for optimization of decisions on energy efficiency investments under uncertainty and regard the decision problem as a multiobjective programming problem. The method is applied to a case of energy efficiency investments at a chemical pulp mill. The case study is used to illustrate that the proposed method provides a good framework for decision-making about energy efficiency measures when considerations regarding greenhouse gas reductions influence the decisions. We show that by setting up the problem as a multiobjective programming model and at the same time incorporating uncertainties, the trade-off between economic and environmental criteria is clearly illustrated.

The energy intensive industry can be a major contributor to CO2 emissions reduction, provided that appropriate investments are made. To assess profitability and net CO2 emissions reduction potential of such investments, predictions about future energy market conditions are needed. Energy market scenarios can be used to reflect different possible future energy market conditions. This paper presents a tool for creating consistent energy market scenarios adapted for evaluation of energy related investments in energy intensive industrial processes. Required user inputs include fossil fuel prices and costs associated with policy instruments, and the outputs are energy market prices and CO2 consequences of import/export of different energy streams (e.g. electric power and biomass fuel) from an industrial process site. The paper also presents four energy market scenarios for the medium-term future (i.e. around 2020) created using the tool.

Significant energy savings can be achieved in the pulp and paper industry through process integration. The aim of this paper was to investigate how much seasonal variations in the process influence the potential for making energy savings. The hot and warm water system in a market pulp mill has been evaluated from an energy point of view, using pinch analysis. Considerable energy-saving potential was found, 40.7 MW, of which 16.5 MW was in the form of steam savings. The steam savings represent 7% of the total steam consumption at the mill. New heat exchanger networks were redesigned using different approaches. The influence of seasonal variations was estimated from the calculated energy savings when monthly averages were used in the new heat exchanger networks. When seasonal variations were taken into account, the energy-saving opportunities fell by 2.5–5.0 MW, depending on heat exchanger network design, compared with a steady-state scenario. Consequently, 88–94% of the theoretical energy savings could be realised. An economic evaluation indicates positive earnings from investment in a new heat exchanger network when seasonal variations were taken into account, even with low prices for the extracted steam and excess heat (5 €/MWh) and with an annuity factor of 0.2.

This paper presents a case study on the optimization of process integration investments in a pulp mill considering uncertainties in future electricity and biofuel prices and CO2 emissions charges. The work follows the methodology described in Svensson et al. [Svensson, E., Berntsson, T., Strömberg, A.-B., Patriksson, M., 2008b. An optimization methodology for identifying robust process integration investments under uncertainty. Energy Policy, in press, doi:10.1016/j.enpol.2008.10.023] where a scenario-based approach is proposed for the modelling of uncertainties. The results show that the proposed methodology provides a way to handle the time dependence and the uncertainties of the parameters. For the analyzed case, a robust solution is found which turns out to be a combination of two opposing investment strategies. The difference between short-term and strategic views for the investment decision is analyzed and it is found that uncertainties are increasingly important to account for as a more strategic view is employed. Furthermore, the results imply that the obvious effect of policy instruments aimed at decreasing CO2 emissions is, in applications like this, an increased profitability for all energy efficiency investments, and not as much a shift between different alternatives.

This paper presents the theory and concepts of a graphical method for heat exchanger network (HEN) retrofit that gives new insights about the complexity and possible solutions of different retrofit alternatives. The method uses knowledge about the placement of heaters/coolers in the existing HEN to evaluate the potential for cost-effective retrofit. One general result this method predicts is that the closer to the pinch the existing heaters/coolers are located, the higher the potential for cost-effective retrofit. Networks that are badly engineered from a grass-root perspective, prove to be a good basis for cost-effective retrofits.

This paper presents the theory and concepts of a graphical method for heat exchanger network (HEN) retrofit that gives new insights about the complexity and possible solutions of different retrofit alternatives. The method uses knowledge about the placement of heaters/coolers in the existing HEN to evaluate the potential for cost-effective retrofit. One general result this method predicts is that the closer to the pinch the existing heaters/coolers are located, the higher the potential for cost-effective retrofit. Networks that are badly engineered from a grass-root perspective, prove to be a good basis for cost-effective retrofits.

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.

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.

Significant energy savings can be made in the pulp and paper industry by implementing process-integrated evaporation (PIvap). The aim of this paper was to evaluate the concept of PIvap for a existing hardwood mill producing kraft pulp and compare the results with the ones from an earlier study of a softwood model mill. Using pinch tools, we found a solution where 1.3 GJ/ADt of pinch violations are solved and 1.1 GJ/ADt of excess heat is extracted. If the excess heat is used in an efficient PIvap, steam savings of 2.7 GJ/ADt could be made in the evaporation plant. Together with the pinch violations and improved soot blowing, the total steam savings were 4.6 GJ/ADt or 36% for an investment cost of 6.6 M€. Compared with the softwood model mill, the configuration of the hardwood mill offered about the same savings with 2.7 M€ lower investment cost, making PIvap more interesting in the hardwood mill. As an alternative to implementing PIvap, more pinch violations can be solved. The PIvap approach gives more steam savings to approximately the same specific cost.

Earlier work has shown that capturing the CO 2 from flue gases in the recovery boiler at a pulp mill can be a cost-effective way of reducing mill CO 2 emissions. However, the CO 2 capture cost is very dependent on the fuel price. In this paper, the potential for reducing the need for external fuel and thereby the possibility to reduce the cost for capturing the CO 2 are investigated. The reduction is achieved by using thermal process integration. In alternative 1, the mill processes are integrated and a steam surplus made available for CO 2 capture, but still there is a need for external fuel. In alternative 2, the integration is taken one step further, the reboiler is fed with MP steam, and the heat of absorption from the absorption unit is used for generation of LP steam needed at the mill. The avoidance costs are in both cases lower than before the process integration. The avoidance cost in alternative 1 varies between 25.4 and 30.7 EUR/tonne CO 2 depending on the energy market parameters. For alternative 2, the cost varies between 22.5 and 27.2 EUR/tonne CO 2 . With tough CO 2 reduction targets and correspondingly high CO 2 emission costs, the annual earnings can be substantial, 18.6 MEUR with alternative 1 and 21.2 MEUR with alternative 2.

In the study presented in this paper different energy efficiency measures that can be carried out in a slaughter and meat processing (SMP) plant were evaluated both in terms of economy and CO2 emission reduction for four different future energy market developments. It was found that it is economically interesting to invest in an increased heat exchanger network or heat pumps in the fictitious non-integrated plants studied and that between 5% and 35% of the total CO2 emissions can be saved. The most cost effective way of reducing CO2 emissions was found to be switching fuel from heavy fuel oil to natural gas or wood chips. For the studied plants that are already heat integrated it was shown that investing in a new heat pump can be economically interesting and can reduce CO2 emissions. The profitability of investing in a combined heat and power (CHP) unit for the SMP plants was also investigated and found to be smaller than extended heat recovery or new heat pumps in the studied plants. However, the payback period for CHP units installed at an ecocyclic industrial park, consisting of an SMP plant and for example a Swedish dairy, was found to be short enough to be interesting. © 2005 Elsevier Ltd. All rights reserved.

Pulp mills use significant amounts of biofuels, both internal and purchased. Biofuels could contribute to reach greenhouse gas emission targets at competitive costs. Implementing process integration measures at a pulp mill in order to achieve pulp production with less use of energy (biofuels) has not only on-site consequences but also off-site consequences, such as substitution of fossil fuels elsewhere by the saved pulp mill biofuels, and less on-site electric power generation. In this paper a method, a linking model, is suggested to analyse pulp mill biofuel saving measures when carbon dioxide (CO2) external costs are internalised. The linking model is based on equilibrium economics and links information from CO2 constrained energy market future scenarios with process integration measures. Pulp mill economics and marginal energy market CO2 response are identified. In an applied study, four process integration measures at a Swedish pulp mill were analysed using five energy market future scenarios emanating from a Nordic energy model. The investigated investment alternatives for biofuel savings all result in positive net annual savings, irrespectively of the scenario used. However, CO2 emissions may increase or decrease depending on the future development of the Nordic energy market.

In this paper, process integration methods are used to investigate the potential to decrease the energy usage in the slaughtering and meat processing industry. Above ambient temperatures, heating of water with different target temperatures is a large heat demand in a plant, while at subambient temperatures the refrigeration plant needs almost all of the shaftwork used at the site. Interaction between, on one hand, energy demands above ambient temperature and, on the other, cooling needs below ambient temperature can take place with freezing compressors or heat pumps. By using process integration methods above and below ambient temperatures, potentials for saving both shaftwork and external heat demand in food plants can be identified. A case study at a modern plant illustrates that even though many energy-saving measures have been taken there is still a technical potential for saving 30% of the external heat demand and more than 10% of the shaftwork used in the plant. The economic potential for the savings is dependent on the conditions at the plant.

The goal of this study is to evaluate co-firing of gasified CO2 neutral biofuel in a retrofitted natural gas combined cycle (NGCC) combined heat and power (CHP) unit designed for natural gas operation. This type of situation may be particularly relevant if future CO2 abatement policies require that owners of natural gas fired CHP units reduce CO2 emissions. The study investigates the technical, economic and environmental performance of the CHP unit for different fractions of gasified biofuel in the unit’s fuel mix. The power plant simulation program GateCycle was used for plant performance evaluation. The calculations are based on a large size (about 300 MWe) NGCC CHP plant that is planned to be built on the West coast of Sweden, producing electricity and district heating for the local energy utility company. The results from this study show that it is possible to co-fire up to 40% (energy basis) biofuel product gas in the CHP unit. At this level of product gas co-firing, the unit’s electrical and total efficiencies decrease by approximately 2%-points, compared to operation on natural gas only. Global CO2 emissions can be reduced by approximately 400,000 tonnes/year. The total costs for the local utility company depend on the prevailing CO2 taxation rules, and on the assumed premium value of the renewable power produced. For the base case conditions assumed in the study, the cost of electricity (COE) for a natural gas fired NGCC CHP unit is 253 SEK/MWh, increasing to 306 SEK/MWh when a biofuel gasifier is integrated to the unit. A premium value for renewable electricity of 285 SEK/MWh is required for equal COE values to be achieved by the two systems.

This paper presents and evaluates different energy efficient options for integrating drying and pelletising of biofuel with a modern energy efficient pulp mill process. When drying biofuel, a large amount of the heat input can often be recovered. One option for heat recovery is to cover low-temperature heat demand in the pulping process. Alternatively available excess heat from the pulp mill can be used for drying. Both alternatives will contribute to a better energy efficiency for the combined pulp mill and biofuel upgrading facility. Pinch analysis tools can be used to estimate the excess heat potential at different temperature levels in the pulp mill. Three different technologies for pulp mill integrated biofuel drying were chosen for the study, namely steam drying, flue gas drying and vacuum drying. The different technologies are evaluated on the basis of energy usage, global CO 2 emissions and resulting pellets production cost, using stand-alone pellets production as a reference. The pulp mill assumed for the calculations is the Eco-Cyclic reference pulp mill. The results of the study indicate that the most attractive integrated drying technology option is the flue gas dryer, using flue gases from the black liquor boiler. With the available flue gas stream at the reference pulp mill, a potential pellets production of 70,000 ton/yr could be achieved at a cost of 24.6 €/ton. The associated reduction in CO 2 emissions compared to stand-alone pellets production is 31–36 kg/MWh pellets .

Many pulp mill hot and warm water systems are overdimensioned and produce more hot and warm water than demanded. This overproduction could be used for other applications, if heat could be released at high enough temperatures. In this paper a new method to release as much excess heat of a high temperature as possible in the secondary heat system has been developed. A case study of a Swedish kraft pulp mill showed that 5-6 MW excess heat with a temperature above 90oC could be released if the system were rebuilt. Two different alternatives for using the excess heat have been investigated.

An existing pulp and paper mill has been studied regarding the reduction of water consumption, and the resulting increased potential for energy integration. When the mill’s hot water consumption is decreased, the live steam demand for the mill also decreases. Also when decreasing the hot water consumption, the quantity and temperature of available excess heat increases. This excess heat can be used for evaporation, thereby reducing the live steam demand further by up to 1.5 GJ/t. A pinch analysis was performed and it was found that when removing pinch violations the hot water consumption is not an important factor any more. Removing all the pinch violations and using the remaining excess heat for evaporation yields a significantly larger energy savings for the mill (4.0 GJ/t). From an economic optimum perspective it is probably most profitable to do a combination of reducing water consumption, removing pinch violations, and use the remaining excess heat for evaporation.

Fuel combustion for heat and/or electric power production is often the largest contributor of greenhouse gas (GHG) emissions from an industrial process plant. Economically feasible options to reduce these emissions include fuel switching and retrofitting the plant's energy system. Process integration methods and tools can be used to evaluate potential retrofit measures. For assessing the GHG emissions reduction potential for the measures considered, it is also necessary to define appropriate GHG emission baselines. This paper presents a systematic GHG emission calculation method for retrofit situations including improved heat exchange, integration of combined heat and power (CHP) units, and combinations of both. The proposed method is applied to five different industrial processes in order to compare the impact of process specific parameters and energy market specific parameters. For potential GHG emission reductions the results from the applied study reveal that electricity grid emissions are significantly more important than differences between individual processes. Based on the results of the study, it is suggested that for sustainable investment decision considerations a conservative emission baseline is most appropriate. Even so, new industrial CHP in the Northern European energy market could play a significant role in the common effort to decrease GHG emissions.

The economics of biofuel combined heat and power (CHP) depend on many technical, economic and political factors. The goal of this study is to investigate how combined supply of process steam and district heating can improve profitability of biofuelled CHP plant investments in small to medium-sized applications. Focus is placed on advanced biofuel gasification combined cycle technologies with high electric power production potential, compared to conventional steam turbine technology. The study assesses biofuel CHP options in a Swedish municipality that includes both an industrial process steam consumer and a district heating network. The results show the clear economic advantage of this type of co-operation. Under the assumed conditions for the study, an optimally sized conventional steam turbine CHP unit achieves the lowest cost of electricity. However, gasification-based CHP technologies generate significantly more electricity than conventional steam cycle technology, which results in higher net CHP plant revenue for a pressurised gasification CHP plant.

In this paper, novel evaporation plant designs that use medium-pressure steam and deliver low-pressure (LP) steam to the steam network as well as conventionally designed plants are simulated and evaluated from a technical and economic point of view. Both evaporation of black liquor only and combined evaporation of black liquor and wastewater are analyzed. The results show that the novel designs suggested in this work all have large potential to save live steam and that an additional 8 m3 of wastewater/ADMT (air dry metric ton) can be evaporated without increasing the mill’s total live steam demand. They also indicate that the demand for LP steam in the rest of the process is less important for the savings in live steam. The total cost for the novel designs and the relationship between that cost and the cost for conventional designs depend on the economic conditions assumed. If the investment in a more energy efficient evaporation plant is considered from a strategic point of view using an annuity factor of 0.1 and if the cost of the saved fuel is rather high in comparison to the electricity price, the total cost for the novel designs will have a lower total cost than the traditional designs.

The potential for greenhouse gas (GHG) reduction in industry through process integration measures depends to a great extent on prevailing technical and economic conditions. A step-wise methodology developed at the author's department based on pinch technology was used to analyse how various parameters influence the cost-optimal configuration for the plant's energy system, and the opportunities for costeffective GHG emissions reduction compared to this solution. The potential for reduction of GHG emissions from a given plant depends primarily on the design of the industrial process and its energy system (internal factors) and on the electricity-to-fuel price ratio and the specific GHG emissions from the national power generation system (external factors).

Heat sources for heat pumps in buildings as well as in industry are discussed. Furthermore, some environmental aspects concerning choice of heat source are highlighted. Only systems for heat pumping are included, i.e. air-conditioning types which can also partly work as heat pumps are excluded. Recent heat pump installations in Sweden are mainly in small systems. Ambient air, exhaust air, soil and rock are the most common heat source types. Data on COP, investment costs, working fluids, present Swedish market etc. for these types of heat sources are given. Data on industrial heat pump installations in some countries and distribution of these according to heat pump type and industry sector as well as heat source temperatures are reported. Process integration aspects when choosing heat source size and temperature are also discussed as well as the relation between these parameters and the choice of heat pump type. Finally, the influence on the economy of the heat source temperature is presented. The cost-effectiveness of heat pumps for reducing CO2 emissions compared with other heating technologies is discussed. The main results are: (1) heat pumps can in many cases in the future contribute to a reduction of CO2; (2) there is a rather big difference, for larger systems a major difference, between the water-based and the ambient air-based heat pumps in terms of efficient reduction of greenhouse gas emissions.