Process engineering in circular economy

Particuology 11 (2013) 119–133

Contents lists available at SciVerse ScienceDirect

Particuology journal homepage: www.elsevier.com/locate/partic

Invited review

Process engineering in circular economy Lothar Reh Institute of Process Engineering, Swiss Federal Institute of Technology (ETH), CH-8092 Zurich, Switzerland

a r t i c l e

i n f o

Article history: Received 26 October 2012 Received in revised form 22 November 2012 Accepted 23 November 2012 Keywords: Perspective Process engineering Circular economy Stocks and flows Energy and material efficiency Multi-scale systems Preparation Entropy Time constraints Steel industry Paper industry

a b s t r a c t Driven by increasing global population and by growing demand for individual wealth, the consumption of energy and raw materials as well as the steadily growing CO2 concentration in atmosphere pose great challenges to process engineering. This complex multi-scale discipline deals with the transformation of mass by energy to manifold products in different industrial fields under economical and ecological sustainable conditions. In growing circular economy, process engineering increasingly plays an important role in recovering valuable components from very diffuse material flows leaving the user stocks following widely variable time periods of use. As well it is engaged in thermal recovery of energy therefrom and in environmentally safe disposal of residual solid wastes whose recovery economically is not feasible. An efficient recovery of materials and energy following the laws of entropy is a must. A complex network of mass, energy, transportation and information flows has to be regarded with growing traded quantities of used goods even on global level. Important constraints in time, however, exist for a necessary realization of innovative new processes and communal mobility and industrial infrastructure on medium and large scale. Based on reasonable long term and highly reliable statistics from industrial organizations representing steel and paper industry, some limits and trends of possible developments in processing of those industries with long recycling experience will be discussed. © 2012 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Contents 1. 2. 3. 4. 5. 6.

7.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Main global challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Process engineering tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stocks and flows of energy and raw material resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Time constraints in developing new efficient recycling processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Recycling in industry—challenges and progress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1. Steel industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2. Pulp and paper industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction Once upon a time in 1938 an aluminum smelter was started up at Lünen, Germany by the state-owned Vereinigte Aluminium Werke (VAW). The fully integrated plant from bauxite ore to high quality aluminum had been supplying the German airplane industry. The plant, located at the northern border of the industrial Ruhr

E-mail address: [email protected]

119 120 121 123 125 127 127 128 132 132 132

district survived World War II reasonably well. Quite a number of important process innovations, amongst others, tube digestion of bauxite, circulating fluidized bed (CFB) calcining of aluminum hydroxide and CFB coal combustion with external heat exchanger, then originated or have been first time realized at this plant (Fig. 1). The smelter covering 230 ha was well equipped with sufficient stocks for bauxite ore, other raw materials and for different processing residues like red mud and used electrodes. The operational workforce had been well experienced in the metallurgical field. Increasing costs for electricity, fuels and railway ore delivery

1674-2001/$ – see front matter © 2012 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

http://dx.doi.org/10.1016/j.partic.2012.11.001

120

L. Reh / Particuology 11 (2013) 119–133

Fig. 1. Lippeworks Luenen of REMONDIS AG. Remondis (2012).

from distant harbor led VAW to shut down their smelter operations. In order not to loose 476 jobs, a takeover between VAW and Rethmann KG, a family company active in logistics and waste collection, was arranged in 1987. The family with remarkable investments into process modifications and the available experienced metallurgical processing staff efficiently has developed the site over 25 years into the largest center for industrial environmental services in Europe. The Lippeworks has also become headquarter of the globally operating REMONDIS AG & Co. KG which handled by the end of 2010 with 19,200 employees more than 27 million tons/year of diverse used material flows in 28 countries. The Lippeworks site itself thus has not only been saved from shut-down, but, in contrast, it is steadily growing and the jobs have been about tripled. So it is an outstanding example for reuse of a complete industrial complex in a very different industrial sector and for the growing need for used products processing (Remondis, 2007, 2012; Reh, 2006)! 2. Main global challenges Let us now turn to the challenges our society in general and with it the process industries globally are facing today. There are five key indicators which describe the main constraints posed on our world’s future development: Population growth, CO2 concentration in atmosphere, energy consumption, use of mineral and natural resources and shortage of water. World population is growing steadily! It recently reached 7 billions, about 50% therefrom living in cities with increasing trend of migration from rural sites to city, probably ending up with a percentage of 70% in 2030. In addition, the specific consumption of resources and average wealth of individuals simultaneously will most likely increase too during the years to come (Heilig, 2012; United Nations, 2011) (Fig. 2). CO2 concentration in global atmosphere, measured at Mauna Loa Observatory, as indicator of sustainable energy use is still further steadily increasing (Tans & Keeling, 2012). During last decade the inclination of the growth curve became steeper with an average growth rate of nearly 2%/year! Compared to the period 1990–2000, for which an average growth rate of 1.5%/year with a remarkable decline during first half of that decade had been observed, this certainly is a remarkable draw back in considering the reduction aims of Kyoto protocol! Global primary energy consumption, quite well documented by detailed statistics from reliable sources, continues to grow

steadily year-by-year, too! Following BP global statistics of primary energy consumption it reached 2010 with 12 Gigatons oil equivalent, a new height! Enerdata documents show even slightly higher consumptions. (BP, 2012; Enerdata, 2012) For trend evaluations, however, it is very helpful to compare the statistical values with the prediction of earlier projections, like that of the Future Stresses for Energy Resources (FUSER) Project of World Energy Council from 1986, a first worldwide effort of energy suppliers (Fig. 3) (Frisch, 1986). If one compares the predictions of global primary energy absolute consumption and the consumption per capita with the statistics of BP and Enerdata, one states that real absolute consumption figures during the last two decades developed nearly parallel to prediction ‘C’ of the FUSER projection (called “fairly probable”!) at a slightly lower level (see Fig. 3, left). Average individual consumption in 2010 with 1.74 tons oil equivalent per capita is only marginal higher than the 1980 value of 1.69 toe/capita (see Fig. 3, right)! One may conclude that energy efficiency increase during that period has decoupled primary energy consumption from global gross domestic product development. However, our society is still far from a wishful constant yearly absolute primary energy consumption as well as from a decrease in per capita consumption (scenario ‘Z’ in Fig. 3, right). A steady introduction of many primary energy saving innovations over the last 30 years in energy and process industries by increased consumption seems not to have been rewarded by success! The use of mineral and natural resources due to their high variety and unclear definitions as well as due to many product oriented industries involved by far is not yet as well statistically documented on a global level (Reh, 2006). Intensified research by United Nations, Organisation for Economic Co-operation and Development (OECD) and national environmental institutions during past two decades created more reliable estimates of global material consumptions. Two UN reports show for 2005 global energy and raw material extraction as well as consumption to be close to 60 billion tons/year. They also agree with a roughly 50% increase in material resources use between 1985 and 2005 (Reh & Büssing, 1999; UNEP, 2011a; UNIDO, 2011). The above-mentioned global figure corresponds to an average per capita resource consumption for each world citizen of nearly 9 tons/year. Considering the mining and harvesting residues not accounted statistically and

L. Reh / Particuology 11 (2013) 119–133

121

Fig. 2. Fundamental global developments.

assuming a steady consumption growth over the past years, per capita materials resource consumption may at least have reached today 11 tons/year! To turn this dramatic trend into a more sustainable one will without doubt be the great challenge not only for process engineering but also more for our whole society during the decades to come! In addition, the natural resource clean water, still regarded in our society as a free commodity, with a projected increase of use of 55% between 2000 and 2050 has become increasingly more scarce (Leflaive, 2012)! The global annual average water footprint (WF) related to agricultural and industrial production as well as domestic water supply for the period 1996–2006 was 9087 Gm3 /year, corresponding to 1385 m3 /year/capita (Mekonnen, 2012). So saving water poses a dramatic challenge to process engineering, too!

3. Process engineering tasks Process engineering, in German speaking countries called “Verfahrenstechnik”, originated from the discipline “Chemical Engineering” in the English speaking world. Today besides in chemical industry it is active in nearly all mass transforming industries, like energy conversion, ferrous and non-ferrous metallurgy, stones and earth, pulp and paper, food and nutrition, health care, environmental protection and others. Its basic tasks are the transformation of raw materials by energy under sustainable conditions, explained in Fig. 4 by a simplified scheme. In mass transforming production processes, treating raw materials, intermediate products or used materials as input, mass is being transformed by primary or final energy into high quality products utilizing the “free” commodities water and air as further inputs.

Fig. 3. Comparison of actual and FUSER Scenario*global energy consumptions. (Note: Curve H stands for consumption continued as usual, Z stands for zero growth from 1980 on and C stands for the scenario with credibility degree “very likely”.) Source: World Energy Council (Frisch, 1986).

122

L. Reh / Particuology 11 (2013) 119–133

Fig. 4. Basic tasks of process engineering.

By integrated environmental protection measures for the production step and optionally for combined internal recycle processes, one tries to avoid or to minimize in situ harmful emissions with the off-streams. Due to strict emission control legislation additive destruction or cleaning processes in most cases are a must to achieve acceptable clean off-gas, clean recyclable water or harmless disposable solid residues below legislative limits. Beside the wanted high quality products very often one or more by-products are unavoidable, especially in chemical production processes. They have to be transferred to other production lines or to another market. This then leads to integrating different processes to a resource conservation network (RCN), mainly utilized in large industrial parks (Foo, 2012). Efficient use of both raw materials and energy, simultaneously minimized input of water and air as well as choosing appropriate reactors and unit operations lead to economic and environmentally acceptable processes. This is demonstrated by manifold industrial examples. Nevertheless despite great efforts in many industries following World Business Council for Sustainable Development CO2 emissions between 1990 and 2009 globally have not been reduced, confirming the conclusions in connection with the FUSER projection above (CEPI, 2012; Veolia, 2011, 2012; WBCSD, 2010; WSA, 2012)! The discipline of process engineering in transforming materials today has to bridge many length scales, for instance from atom in nuclear reactions at the low side to erecting water supply and recycling systems for megacities at the high end (Ge, Wang, Ren, & Li, 2008). Main industrial process applications, however, are located in the length ranges from particle to megacity. Investment costs of processing plants often reach the several 100 million EUR range and need careful farsighted project management to minimize economic risks. Process engineering design is strongly based on the basic laws of mass and energy balances, entropy, system science and last but not least mathematics. In addition

interdisciplinary information exchange between all industrial and societal sectors involved is vital for successful project performance. Another extremely important factor in process engineering and development is expressed by the time axis in the center of Fig. 5. It poses severe constraints to wanted and needed short process plant realization time. This point will be discussed later in more detail (Fig. 6). Laws of process integration also apply for the largest scale of possible circular economy, our idealized technically shaped environment with the sectors of industry, transportation and living (Reh, 2006). These laws are mass and energy conservation “more in-more out”, entropy based pinch methods, optimization and resource conservation network (RCN) (Foo, 2012). The more gaseous, liquid and solid resources of any kind are being used, the more off-gas, waste water and solid residues following varying times of use have to be treated to protect the natural environment. The 3R principle: Reduce, Reuse and Recycling, may reduce the stress on different global resources considerably. Its quite complex application is already growing steadily with statistical difficulty to measure progress. How to analyze the degree of reduction in global primary raw materials consumption by recycling will certainly be an important discussion topic for the World Resources Forum over the years to come! Recycling of used water in industries and cities is developing slowly into an increasing business activity already with further great potential in growth and innovation (Remondis, 2007; Veolia, 2011, 2012). Off-gas cleaning for all kinds of harmful species has to be performed in situ at the individual sources by adapted and well proven equipment. Global amounts of those gases are not to assess. Therefore in the following mainly the global cycles of energy and raw material resources will be discussed. Both are reasonably well covered by coordinated production statistics over periods of at least two decades (BP, 2012; CEPI, 2012; Enerdata, 2012; UNEP, 2011a; UNIDO, 2011; WSA, 2011).

L. Reh / Particuology 11 (2013) 119–133

123

Fig. 5. Process engineering in complex multi-scale systems.

4. Stocks and flows of energy and raw material resources To illustrate the very complex flows of energy and raw materials including their many stocks, a very simplified flow scheme of global economy helps, as shown in Fig. 7. In reality today production and transport steps are hardly to separate from each other because of an international just-in-time network, where containers and bulk carriers are simultaneously used as transport vessels and stocks. Huge container terminals in international harbors replace temporary stocks in magazines at production sites. Reducing the number of stocks to the most relevant ones leaves us with the supply stock of resources in nature (Fig. 7, bottom), the user stock in our technical shaped society (Fig. 7, top) and with three disposal stocks for unaccounted losses, reacting landfills and the most wanted disposal site of not leachable residues (Fig. 7,

right). The triangles, symbolizing resources in “supply stock nature” and “depreciating materials user stock”, indicate short average retention time in the apex and extremely long average retention time at the bottom. The time range in the supply stock extends from fractions of a second for photovoltaic energy to the geological age of an ore mine. The more we will use renewable energy and biomass, the more we will rely on shorter averaged mean retention time resources in the supply stock nature. Supply security will suffer! The retention time range for materials in the user stock, where all product inputs depreciate with time until being disposed of, is certainly smaller, but in the cases of buildings and infrastructure it may reach centuries, too. The united flow of fossil raw materials and biomass out of the supply stock nature splits into two flows, one being ores, minerals and fossil energy resources, going into raw materials

Fig. 6. Idealized circular economy.

124

L. Reh / Particuology 11 (2013) 119–133

Fig. 7. Simplified global cycle of material and energy stocks and flows. (For interpretation of the references to color in the text, the reader is referred to the web version of the article.)

preparation close to the site of mining, bringing discards back to mine (not shown here) or biomass into pulp industry. The second flow, mainly energy raw materials, will be transformed in refineries to transportation fuels, still remaining thermodynamically a primary energy, or it will be converted in fossil or nuclear power plants with high losses of low temperature heat into the thermodynamically higher valued final energy electricity. The output of the raw materials preparation plants, mainly located in remote areas, will be transported overseas in huge bulk carriers or over long land distances by long railway trains to large capacity metallurgical smelters, chemical plants etc. Those then deliver a huge variety of intermediate products to manifold manufacturing industries. There again by means of energy the intermediates are combined to more and more complex final consumer goods like cars and electronic devices. Furthermore, combining different materials to such complex systems leads to increasing positive entropy, known as devaluation of heat. The final products then are distributed by energy consuming trucks or by rail into the user stock. With yearly increasing production flows this user stock in our technical shaped environment is steadily enlarged. This is especially true for durable products like steel, aluminum and concrete, because their disposal flows only grow with a long time delay measured in decades (CEPI, 2012; Georgescu-Roegen, 1971; Hornbogen, 2002; Reh, 2006; UNEP, 2011b)! In 1998 the output flow of old aluminum scrap was about half of the primary aluminum input flow to the user stock (Reh, 2006). In 2010 with 41 million tons primary production and 20 million tons collected old scrap the primary aluminum flow to old scrap flow ratio remained unchanged. A rough estimate of average time delay of aluminum flow through user stock amounts from 30 to 40 years! About 75% of 955.8 million tons aluminum

ever produced are estimated to be still in the users stock (Knapp, 2012)! For the total global flow of depreciated materials out of the user stock no reliable statistics exist! An assessment in 2006, excluding wastes from construction and demolition, mining and agriculture, estimated only the material flow collected to 2.5–4 billion tons/year. The so-called municipal waste was estimated to 1.2 billion tons/year (Lacoste, Chalmin, Cyclope, & Veolia Environmental Services, 2007). In addition, no reliable data are available concerning the split of the total global output flow into five main branches: unaccounted losses to nature (such as plastics in sea), reacting landfills, incineration, separation for recycling and reuse of products (area in Fig. 7, top right). Depending on widely varying retention times of the many materials in the user stock, predictions about composition and flow rates for separation plant inputs are very vague, making planning and investments for such plants economically extremely risky. Unaccounted flows of losses should be avoided by legislation; flows to reacting landfills because of long-term danger of dangerous species release in some countries are forbidden by law and must remain intermediate solutions. The flow of reused products will be regulated by market forces. So interest in used product processing has to concentrate on separation and combustion technology. The ratio of separation to combustion flow rates, by resource saving reasons should be maximized. It is and will be for some time in future the great challenge for 3R! Before leaving the discussion of Fig. 7, the very strong interconnection between material and energy cycle (yellow arrows) has to be emphasized, indicating that both material and energy efficiency simultaneously define the sustainability of production and recycling processes.

L. Reh / Particuology 11 (2013) 119–133

125

Fig. 8. Life cycle approach—end of life scenarios (Brimacombe, 2012).

Fig. 8, originating from TATA STEEL, shows as an example, how much of three different main building components, concrete, timber and steel from a demolished structure, actually are separated and distributed to the different flows of reuse, incineration, down cycle and landfill. Achieving high recycling flows simultaneously for the three materials remain a dream. So maximal recovery has to concentrate on the higher valued materials, such as steel in this case. The more different materials have been combined during manufacturing and as such being stored in the depreciated goods stock, the more process options for recovery in planning have to be investigated. The choice of the optimal recycling process becomes extremely more complex, but to finally release the burden in many cases makes it worthwhile. Life-cycle processing should follow lifecycle analysis! The dust of automobile shredder plants contains quite a number of usable materials. By optimally combining a variety of subsequent sorting process units in a first industrial plant, Toyota Motor Corporation (2012) has succeeded in treating industrially automobile shredder residue (ASR) from about 15,000 cars per month to recover all valuable materials without any remaining residue, as shown in Fig. 9. Seven different intermediate recyclable materials are recovered in comparable small flows by the ASR process as compared to the two large flows of ferrous and nonferrous scraps from shredding operation itself. High value electric energy is applied in the different process steps for decreasing the entropy of mixing created during production. The heating value of final carbon containing material at the end of the sorting line directly substitutes as primary energy high value final energy electricity in an electric arc furnace for production of steel from iron scrap. Process technology and products have been successfully tested since start-up in 1998 to gain operational knowhow and to demonstrate technological as well environmental feasibility (Toyota Motor Corporation, 2012). The global car population, estimated to have exceeded one billion cars in 2010, will create increasing flows of those materials, when being recycled!

The TU Bergakademie Freiberg, Germany, historically for centuries oriented to mining and preparation technology, recently has initiated a “Declaration of a World Forum of Universities of Resources on Sustainability”, signed in June 2012 by representatives of 58 universities of resources from 39 countries to improve international cooperation in scientific research and education in the field of raw material resources and resource recovery (WFURS, 2012). 5. Time constraints in developing new efficient recycling processes As already mentioned, processing plants and their products are closely connected in many aspects. As we see from the Toyota example, developing new processes and creating new quality raw materials therewith usually take several years from idea to start-up of a first production. The different development steps to be performed optimally in simultaneous and adjusted timely cycles shown in Fig. 10, necessary to introduce successfully new processes (left) and products (right), are quite self-explanatory. Producing innovative high quality products requires also the combination with an innovative sustainable process to assure successful economic and ecologic performance of a new industrial mass transforming plant. During plant operation they are combined as narrowly as two sides of a coin do! Both remain closely combined during the long lifetime of the plant, where new knowhow for product or process may be steadily gained. These, by a continuous reflux of experience via information network indicated with green arrows, initiate or contribute to innovations in the different responsible departments (Reh, 1996; Wintermantel, 1992). For separation of used products in recycling, the input flows of different materials are mandatory and their timely varying compositions require different or flexible processing schemes. Compared to off-mine ore separation, much more efforts are needed however in serving the acceptance

126

L. Reh / Particuology 11 (2013) 119–133

Fig. 9. New Toyota automobile shredder residue (ASR) recycling plant. Toyota Motor Corporation (2012).

specifications of the different production industries, which convert the recovered output flows into useful products again, as well as in marketing the multiple outputs. The re-user industries have to adapt their own processes to cope with the somewhat minor

quality recycled resource flows accordingly, of course! All these steps additionally need longer planning and realization periods Processing plants due to high capital investments during their development, planning and construction stage by economical

Fig. 10. Connected life-cycles of process and product.

L. Reh / Particuology 11 (2013) 119–133

127

Fig. 11. Idealized development of accumulated cost and revenue of a processing plant.

reasons have to be operated for long periods, up to 10 fold of a political election period or two life generations. During the first 2–5 years, depending on type and capacity of the plant under planning, only costs accumulate. During about the same length of period of operation then all revenues of the successfully started and operating plant are recovering the costs of the construction period. Having reached this return of investment (ROI) point of time, undisturbed marketing of its products and stability of operational costs provided, the plant earns steadily money above the coverage of its investment and operational costs. Toward the end of lifetime, repair and other operational burdens as well as market competition or emission legislation make operation unprofitable. With extra costs the plant has to be dismantled in an ecologically friendly way, with itself becoming an object of recycling or modified reuse. As indicated in Fig. 11, in normal operation typical life times of plant and building projects extend to more than 40 years. If plant life were shortened by unexpected or force majeure events, huge losses of capital for future projects would occur. This capital will be lacking for the urgently needed future investments. So even risk-taking entrepreneurs take their time in preparing new plant projects properly. Legislative and political stability will ease their actions and decisions! 6. Recycling in industry—challenges and progress 6.1. Steel industry Steel is a key driver of world economy. Global crude steel production in 2011 reached 1518 million tons/year contributing 6.5% of global CO2 emissions. Over the last 10 years, crude steel production rate has nearly doubled. Material efficiency in 2010 was 97.7%! Compared to 2005, following a steady decrease in the earlier years, global average specific energy input of 20.7 GJ/ton crude steel cast in 2010 showed no further reduction. Consequently specific CO2 emission of 1.8 tons CO2 per ton crude steel cast from 2007 to 2010 remained nearly constant, too. Global average per

capita steel consumption increased to 220 kg per year. Construction industry with 51.2% of total steel consumption was the main global steel consumer. However, recycling in steel industry has a long tradition with 22 billion tons recycled since 1900. With a recycling rate of 500 million tons/year today steel is the most recycled industrial material (WSA, 2011). Two main process routes as shown in Fig. 12 are used today in steel industry: blast furnace-basic oxygen furnace (BF-BOF) with 69.8% and electric arc furnace (EAF) with 29.0% of total crude steel production in 2010. According to World Steel Statistical Yearbook between 2001 and 2010 the BF-BOF fraction increased from 62.2% to 69.8%, whereas the EAF fraction decreased from 33% to 29%. Despite an increase of 44% EAF steel produced from scrap, there is still an 86% increase of steel produced by the less energy efficient and more CO2 emitting BF-BOF route, compensating possible improvements in specific energy efficiency. Both routes differ in mode of operation and unit capacities of a single line. While a continuously operating BF-BOF unit today is able to produce 14,000 tons/day or 5 Mtons/year crude steel, discontinuously operated EAF units have lower maximal production rates, but are more flexible in operation. Very commonly, EAF units are used for mini steel mills, too. Direct reduced iron (DRI), mainly produced with gaseous reducing agents methane (CH4 ) or hydrogen (H2 ), amounted in 2010 to about 5% of total crude steel production and is mainly converted alone or as a refining component together with scrap in electric arc furnaces to steel. A scrap to DRI ratio of 9:1 is quite common for EAF. Today’s infrastructure of steelmaking from mine to steel product contributes to large environmental burdens, since huge bulk carrier long distance sea shipments (blue area) consume large amounts of fossil fuels and separate mining and iron ore preparation and agglomeration processes (upper area) from the metallurgical steel smelting processes (lower area), as shown in Fig. 12. Minimizing transportation tonnages and distances during planning of process and infrastructure for mine to steel could more likely influence future innovative process developments.

128

L. Reh / Particuology 11 (2013) 119–133

Fig. 12. Processing routes from ore to steel. (For interpretation of the references to color in the text, the reader is referred to the web version of the article.)

The well established BF-BOF route is under strong economical and environmental pressure due to increasing shortage of metallurgical coke, high CO2 emissions, large quantities of slag and dust from blast furnace gas cleaning. The systematically improved technology in modern plants uses today only the small amount of 0.49 kg carbon containing reducing agents per kg metal produced and operates at the possible limits set by physics (NAB, 2011; ULCOS, 2012; WSA, 2012). The process steps of iron ore mining and preparation, as shown in Fig. 12 in reality are a long sequence of energy consuming processing steps. Typical downstream processing for a large magnetite ore mining project in remote Western Australia, still excluding supporting infrastructure power plant, water desalination, new harbor and trans-shipment, is illustrated in Fig. 13. By transporting highly concentrated pelletized magnetite ore with 67% iron content instead of lower concentrated hematite ores, shipment tonnages and therewith energy consumption and emissions of shipment are considerably reduced (CITIC Pacific, 2012). In many mine locations on the globe exist large stocks of discarded, mostly fine preparation tailings, from which useable ores may be recovered by modern separation processes (Dworzanowski, 2012)! Several options for new steelmaking processes are under investigation in the ULCOS joint development project of European steel industry to improve sustainability. Already industrially realized processes for producing steel from fine ores completely eliminating coking and agglomerating plants using fluidized bed processing should be considered. Since 2007 a 1.5 million tons/year plant has operated successfully applying the FINEX process at POSCO steel works in Korea (see Fig. 14, bottom right). The process jointly developed by Siemens VAI Metals Technologies, Austria, and POSCO, Korea, uses coal instead of coke as reducing agent in a final melting step (Schenk, 2011). With the further new development of large fracking gas resources, the Circored® process for low

temperature hydrogen reduction developed by OUTOTEC and first realized in a 0.5 million tons/year plant at Trinidad (see Fig. 14, top left), may become an interesting option (Elmquist, Weber, & Eichberger, 2002). Combined with new revolutionary continuously operated electric arc furnace technology developed by SIEMAG, Germany, which recently has been demonstrated first in industrial scale, there exists quite a variety of innovative process options for more energy efficient and CO2 emission reduced steel production (SMS Siemag, 2012)! Even when combining innovations with proven technology, the need for high capital investments and a lack of sufficiently educated engineering personnel pose high timely constraints for creating reliable new steel making processes! Simultaneously increased demand of steel has to be fulfilled, also binding trained man power! So development of change takes time! 6.2. Pulp and paper industry Not only steel and non-ferrous metal industries are successful recyclers. The paper and board industry is an example for successful sustainable production from biomass, mainly wood. In 2010 it produced globally 386 million tons/year paper and board of different product qualities. Under strong pressure by environmentalists at the beginning of last quarter of past century, the paper mills in Europe organized themselves in the Confederation of European Paper Industries (CEPI) and started early voluntary activities to reduce the consumption of raw material wood as well as to develop ways for sustainable processing. Selected collection of used paper and increasingly developed processing technologies of used recycling paper, such as sorting, dissolving in water, eliminating impurities and short fibers as well as deinking by flotation and bleaching finally deliver a pulp as raw material for white recycled paper.

L. Reh / Particuology 11 (2013) 119–133

129

Fig. 13. Downstream processing of iron ore.

In contrast to metals, which are unlimited in manifold recycling, cellulose fibers may pass the recycling process 4–6 times. Then they are sorted out as short fiber and combusted for power and heat co-generation. CEPI, consisting of 520 pulp, paper and board

producing companies in 19 EU countries together with Norway and Switzerland, represents 95% of European as well as 25% of global paper and board production. It is leading the European Recovered Paper Council, which has published as a vision “European

Fig. 14. Steel production without coke.

130

L. Reh / Particuology 11 (2013) 119–133

Fig. 15. From raw material to paper. CEPI (2012).

Fig. 16. Development in European pulp and paper industry over last two decades. CEPI (2012).

L. Reh / Particuology 11 (2013) 119–133

131

Fig. 17. Global flows of used paper 2010. Küffner (2012).

Declaration on Paper Recycling 2011–2015” (CEPI, 2011, 2012; UPM, 2011). The very detailed excellent statistics from voluntarily delivered data over two decades by the CEPI members allow drawing a clear picture of the development status of the cooperative. Fig. 15 shows that less than half of the raw material for paper and board production stems from pulp produced from wood; 52% of fibers containing raw material is recycled paper, either collected in the cities separately or from paper sorted automatically and/or by hand out of mixed communal wastes. 95 million tons of paper and board of wide specifications in quality are produced by the European companies as shown in Fig. 15, most of the recycled paper ending up as newspaper resource! Also in USA and Canada efforts in sustainable production of paper are coordinated by an Environmental Paper Network (2011). The different process of paper processing steps is quite well described by Wikipedia (n.d.). There has been a trend for increasing plant capacity, indicated by the decreasing number of paper and board mills and the simultaneously from 1991 to 2011 growing total production rate. The averaged yearly increase of production rate amounted to 1.8% (Fig. 16, left). These results, originating from a large extension by increased input of used paper, have been achieved by simultaneously reducing primary energy and electricity consumption by co-generation of heat and power (CHP) and decreasing water input by using process water recycling. Gaseous CO2 , SO2 and NOx emissions and water emissions, characterized by COD (chemical oxygen demand), BOD (biological oxygen demand) and AOX (adsorbable organic halogen compounds) have been steadily decreased, too. The indexed values of increasing production and decreasing emissions are shown in the right figure of Fig. 16. Whereas in the mid of last century, nearly all paper and board were produced from wood and other natural fibers and recycled paper used to be more or less gray, today high quality white paper for different applications is being produced. Only high valued very special papers rely only on natural pulp.

One of the most modern European paper mills based on recycling paper with a yearly output of 550,000 tons at Perlen, Switzerland is based on an input of 400,000 tons pre-sorted household collection paper together with thermo-mechanical pulp derived from sawing mills and wood chopping from native spruce as raw material input as the rest (Perlen Papier AG, n.d.). In wood rich countries, in order to secure their plant sites against loosing pulp production, paper mills use surplus wood increasingly for energy production in the form of electricity and waste based ethanol production. They change their infrastructure accordingly (IEA Bioenergy, 2002; Sipilä, Vehlow, Vainikka, Wilén, & Sipilä, 2009). Not only in steel industry but also for the paper and board industry, energy consumption, emissions and cost of transportation play an important role. Large paper mills by economy of scale have lower specific operating costs and fulfill environmental requirements more easily. The collection of used papers from an increased collection area to provide the larger inputs leads to more and longer road bound traffic with increased energy consumption and emissions. Sustainable footprint of transport again has to be included in energy and emission balances and infrastructure planning. Used paper not only is transported regionally. Today but it also becomes a globally traded commodity! Countries lacking wood resources or countries in development for future may increasingly import used paper from countries with surplus in order to cover their needs. So China in 2010 imported 22.6 million tons used paper from surplus countries like USA and Europe (see Fig. 17) (Küffner, 2012). To cope with the yearly production of 92.7 million tons about another 27.8 million tons resulted from own recycled paper. So the coast near areas, equipped in the recent past with quite a number of paper mills for treating 400,000 tons/year used paper, save valuable forest resources and build up a user stock of raw material for future use (EUWID Pulp & Paper, 2011).

132

L. Reh / Particuology 11 (2013) 119–133

7. Concluding remarks What are the final conclusions for process engineering in further improving sustainability in resources? First in view of the ongoing battle during the coming decades to minimize the increases of global atmospheric CO2 concentration and of primary energy consumption, rational use of all resources in process industries as well as in other parts of our technically shaped environment is an ongoing must! High energy and material efficiency in production as well in recycling processes save valuable resources and are the way into a sustainable future. Besides improving single unit operations or plants only, complex industrial processing clusters should be optimized and designed for reduced waste of resources. Additionally there will be a chance to recycle a large number of valuable components with increasing quantity for high quality re-use. However, recycling of all components of used products with high recycling rates will remain a dream. Methods for selecting the most valuable components for recovery need to be established. To develop recycling of used products into a successfully expanding industry, research in basic laws of entropy in engineering and economy should be supported, projecting of industrial complexes for optimal use of resources should be given more attention in academic teaching. Continuation and extension of statistics for resource stocks and flows as measures of progress will be of great help. Even then the time period needed for a turn around or stabilization in global primary energy and raw materials consumption with corresponding decrease of CO2 concentration in atmosphere will be long. Under the present auspices of growing resource consumption also important individual as well as communal contributions in efficiently using energy and raw materials resources will become necessary.

Note from Author—In memory of Prof. Mooson Kwauk

author with invited lectures about fluidization dates to this period. Mooson Kwauk early recognized the importance of particle technology to China! As first President of “Chinese Society of Particuology” he acted as highly estimated member in advisory boards of global conferences, such as “Fluidization” and “Circulating Fluidized Beds”. He initiated and chaired quite a number of bi-lateral research exchange meetings and conferences between China and the US, Japan and Germany. His early contacts to Switzerland paved the way for a long term cooperation in fluidization research as well as in circular economy. With his beloved wife Huichun Kwei, who always gave him great support, he highly enjoyed fine arts and classical music. Designing complex mobiles was his hobby! Like his steadily moving mobiles Mooson Kwauk’s visions in future quite long will inspire his colleagues and coworkers, his former students and his many friends around the globe! Note from Editor On October 21, Prof. Mooson Kwauk, the Editor in Chief of Particuology, attended the last time in his life an international conference, the World Resources Forum 2012. Prof. Mooson Kwauk listened to Prof. Lothar Reh’s plenary lecture and was deeply impressed by the comprehensive information and strategic viewpoints on process engineering. There, he made his last invitation for this contribution, hoping this paper may enlighten our readers, who have been devoting their knowledge of particle science and technology to benefiting process industries.

Acknowledgements The author thanks all individuals and organizations, who elaborated the statistics and process developments described, for enabling this review article and for their valuable contributions to sustainable processing! References

During presentation of the preceding paper in the opening session of the World Resources Forum 2012 at the China National Convention Center, Beijing on October 21st , 2012, the author gave credit to Prof. Mooson Kwauk, with whom he has been bound up in deep friendship since 1984. The brief, but intense discussions during the break of the session unexpectedly became a last contact. Prof. Mooson Kwauk unfortunately passed away on November 20th, 2012, having been actively editing his creation “Particuology” until the last day! With him the international science community in the fields of metallurgical, chemical and process engineering looses a leader with highest integrity, always strong engagement and gentle personality! As Director of the Institute of Chemical Metallurgy of Chinese Academy of Sciences (CAS) he investigated liquid/solid and gas/solid particle systems, successfully developed them into new process applications and led the institute through difficult times. During the beginning of the 1980s he early opened the institute to international science exchange by inviting researchers from abroad. The first personal contact of the

British Petroleum (BP). (2012). BP statistical review of world energy June 2012. Retrieved August 30, 2012 from: http://www.bp.com//statisticalreview, pp. 41–45 Brimacombe, L. (2012). A life cycle approach to sustainable construction. In Presentation at LCA and steel seminar of world steel association July, Beijing, China. Confederation of European Paper Industries (CEPI). (2011, November). CEPI sustainability report 2011. Retrieved September 25, 2012 from:. http://www. cepi-sustainability.eu/uploads/Sustainability Report WEB.pdf Confederation of European Paper Industries (CEPI). (2012). Key statistics 2011. Retrieved July 28, 2012 from:. http://cepi.org/system/files/public/documents/ publications/statistics/Key%20Statistics%202011%20FINAL.pdf CITIC Pacific. (2012). The Sino iron project. Retrieved September 20, 2012 from:. http://www.citicpacific.com/en/our-business/iron-ore-mining-facts-andstatistics.html Dworzanowski, M. (2012). Maximizing the recovery of fine iron ore using magnetic separation. Journal of the Southern African Institute of Mining and Metallurgy, 112(3), 197–202. Elmquist, S. A., Weber, P., & Eichberger, H. (2002). Operational results of the Circored® fine ore direct reduction plant in Trinidad. Stahl und Eisen, 122(2), 59–64 (in German). Enerdata. (2012). Global statistical yearbook 2012. Retrieved September 04, 2012 from:. http://yearbook.enerdata.net/energy-consumption-data.html Environmental Paper Network. (2011). The state of the paper industry 2011. Retrieved September 25, 2012 from:. http://environmentalpaper.org/our-resources/ 2011-state-of-the-paper-industry/ EUWID Pulp and Paper. (2011). Paper production and consumption in China further increases in 2010. Retrieved October 1, 2012 from:. http://www. euwid-paper.com/news/ Foo, D. C. Y. (2012). Process integration for resource conservation. Boca Raton: CRC Press. Frisch, J.-R. (1986). Future stresses for energy resources: Energy abundance, myth or reality? London: Graham & Trotman. Ge, W., Wang, W., Ren, Y., & Li, J. (2008). More opportunities than challenges—Perspectives on chemical engineering. Current Science, 95(9), 1310–1316.

L. Reh / Particuology 11 (2013) 119–133 Georgescu-Roegen, N. (1971). Stocks and flows. In The entropy law and the economic process. Massachussetts: Harvard University Press., pp. 219–224. Heilig, G. H. (2012). World urbanization prospects—The 2011 revision. In Presentation at the Center for Strategic and International Studies (CSIS) June, Washington, DC. Hornbogen, E. (2002). A definition of “sustainability” based on entropy production by matter and energy. In Proceedings of R’02—6th world congress on integrated resources management (CD-ROM) February, Geneva, Switzerland. IEA Bioenergy. (2002). Position paper: Sustainable production of woody biomass for energy. Retrieved September 25, 2012 from:. http://ieabioenergy.com/ LibItem.aspx?id=157 Knapp, R. (2012). Aluminum recycling: Closing the loop for a sustainable future. In Paper presented at the International Aluminum Institute, Asian Recycled Aluminum Conference July, Bangkok, Thailand,. Retrieved September 20, 2012 from:. http:// recycling-world-aluminum.org/ Küffner, G. (2012, June). Recycling: Die papiertiger schlagen zu. FAZ Frankfurter Allgemeine Zeitung. Retrieved October 1, 2012 from:. http://www.faz.net/ aktuell/technik-motor/recycling-die-papiertiger-schlagen-zu-11766013.html Veolia Environmental Services. (2007). In E. Lacoste, P. Chalmin, & C. Cyclope (Eds.), From waste to resource—2006 world waste survey. Paris: Economica. Leflaive, X. (2012). Water outlook to 2050: The OECD calls for early and strategic action. Retrieved September 05, 2012 from:. http://www.globalwaterforum.org Mekonnen, M. M. (2012). The water footprint of humanity. Retrieved September 05, 2012 from:. http://www.globalwaterforum.org/wp-content/ uploads/2012/04/The-water-footprint-of-humanity-GWF-1214.pdf?9d7bd4 National Australia Bank (NAB). (2011, February). Bulk commodities monthly update. Retrieved September 20, 2012 from:. http://emergingmarkets.ey.com/ wp-content/uploads/downloads/2012/04/Global-Steel-Report-2010-trends2011-outlook April2011.pdf Perlen Papier AG. (n.d.). We are “recycler”. Retrieved August 16, 2012 from: http://www.perlenpapier.ch/en/company/environment/recycler.htm Reh, L. (1996). Servicing processing plants—Cost factor or chance? Technology, Law and Insurance, 1, 75–83. Reh, L. (2006). Challenges for process industries in recycling. China Particuology, 4(2), 47–59. Reh, L., & Büssing, W. (1999). Global cycle of basic materials—A growing challenge. In Proceedings of the conference R’99, vol. II Geneva, Switzerland, pp. 81–86 Remondis. (2007). Company brochure 2007. Retrieved August 30, 2012 from:. http://www.remondis.de/downloads 46451/ Remondis. (2012). Remondis profile. Retrieved August 30, 2012 from:. http://remondis.com Schenk, J. L. (2011). Invited paper—Recent status of fluidized bed technologies for producing iron input materials for steelmaking. Particuology, 9(1), 14–23. Sipilä, E., Vehlow, J., Vainikka, P., Wilén, C., & Sipilä, K. (2009). Market potential of high efficiency CHP and waste based ethanol in European pulp and paper industry. VTT Tieotteita – Research Notes 2500, VTT Technical Research Centre of Finland., ISBN 978-951-38-7320-2. Retrieved September 25, 2012, from:. http://www.vtt.fi/publications/index.jsp

133

SMS Siemag. (2012, June 21). New electric arc furnace S/EAF® for continuous operation—A revolutionary new development. Press release, Düsseldorf. Retrieved September 25, 2012, from: http://www.sms-siemag.com/ download/esmssiemag 2012-06-26.pdf Tans, P., & Keeling, R. (2012). Trends in atmospheric carbon dioxide, Mauna Loa observatory. Retrieved August 30, from:. http://www.esrl.noaa.gov/gmd/ccgg/trends/ Toyota Motor Company. (2012, April). Vehicle recycling. Brochure: Environmental Affairs Division. Retrieved July 28, 2012 from:. http://www.toyota-global.com/ sustainability/report/vehicle recycling/pdf/vr p10-p20.pdf ULCOS. (2012). Steel and CO2 : Reaching the limits. Retrieved September 20, 2012 from:. http://www.ulcos.org/en/steel/CO2 limits.php United Nations Environment Programme (UNEP). (2011a). Decoupling natural resource use and environmental impacts from economic growth. Retrieved August 30, 2012 from:. http://www.unep.org/resourcepanel/decoupling United Nations Environment Programme (UNEP). (2011b). Recycling rates of metals—A status report. A report of the Working Group on the Global Metal Flows to the International Resource Panel. , ISBN 978-92-807-31613. Retrieved September 20, 2012 from:. http://www.unep.org/resourcepanel/ Portals/24102/PDFs/Metals Recycling Rates 110412-1.pdf United Nations Industrial Development Organization (UNIDO). (2011, April). Green industry for a low-carbon future: Resource use and resource efficiency in emerging economies—A pilot study on trends over the past 25 years. Commissioned by UNIDO under the “Green Industry” program. Retrieved August 29, 2012 from:. http://www.unido.org/fileadmin/user media/Services/Green Industry/1256 11 Onscreen Green%20Industry.pdf United Nations. (2011). World population prospects, the 2010 revision. Retrieved September 04, 2012 from:. http://esa.un.org/wpp/excel-Data/population.htm UPM. (2011, May). Paper—The sustainable alternative. Retrieved September 25, 2012 from:. http://www.upmpaper.com/en/Papers/downloads/brochures/ Documents/ Veolia. (2011). Business overview 2010—Veolia water. Retrieved September 05, 2012 from:. http://www.veolia.com/en/medias/publications/ Veolia. (2012). 2011 annual and sustainability report. Retrieved September 05, 2012 from:. http://www.veolia.com/en/medias/publications/ Wikipedia. (n.d.). Paper recycling. Retrieved September 25, 2012 from: http://eu.wikipedia.org/wiki/paper recycling Wintermantel, K. (1992). Trends in der Verfahrenstechnik. In Presentation at an internal meeting of university professors and industrial managers April, BASF Breitnau, Germany, World Business Council for Sustainable Development (WBCSD). (2010). Vision 2050—The new agenda for business. Geneva, Switzerland: WBCSD. World Forum of Universities of Resources on Sustainability (WFURS). (2012, June 12). Declaration of the world forum on sustainability. Germany: Technical University Freiberg. Retrieved September 20, 2012 from:. http://www.worldforum-sustainability.org/?page id=4 World Steel Association (WSA). (2011). Statistical yearbook 2011. Retrieved July 28, 2012 from:. http://www.worldsteel.org/statistics/statistics-archive.html World Steel Association (WSA). (2012, June). Sustainable steel—At the core of a green economy. , ISBN 978-2-930069-67-8. Retrieved September 20, 2012 from:. http://www.worldsteel.org/dms/internetDocumentList/