- Written by Achim Rott, Yara Industrial GmbH
There is always a potential risk of explosions when handling combustible bulk solids and powders. Process technicians and engineers know how to estimate and minimise this risk. Nevertheless, devastating dust explosions occur too frequently. So-called 'hot-spots,' sudden spontaneous combustion and explosion risks lurk in every stage of the storage, processing and transportation of combustible powders. In the cement industry, this has relevance to coal-grinding systems. Here, Achim Rott from Yara Industrial GmbH explains the different types of inerting systems that can be used to prevent such explosions in the cement industry.
To have an explosion there needs to be oxygen (O2), a fuel source and an ignition source in the same place at the same time. In the case of coal-grinding or storage (as one might find in a cement plant) it is not possible to remove the fuel (coal) or ignition source (grinding energy, heat, static charges) and so one has to concentrate on removing the third necessary component - O2.
This fact has given rise to inerting systems that rely on the use of inert gases. Inert gases have a low level of reactivity and reduce oxygen concentration to below critical levels. By doing this, they prevent the occurrence of critical operating conditions and consequently any resulting explosions or fires. Different inert gases are effective to different extents and it is often not absolutely necessary to replace all of the O2.
Inerting systems are an effective way to satisfy ATEX regulations that cover explosion prevention. In addition the inerting guidelines CEN/TR 15281, VDI 2263-2 and TRBS 2152-2 are used.
Generally, in terms of the European Directive 94/9/EG (Atex 95a) inerting systems are not seen as protection systems and hence are not subject to compliance with the requirements for this directive. An installation not in range of a possible dust explosion zone, in accordance with the European Directive 99/92/EG (Zone 20, 21, 22), is thus strongly recommended.
- Written by Dr Peter Edwards, Global Cement Magazine
The largest country in the world,1 Russia is also in the enviable position of having huge natural resources, including limestone, diamonds, gold, fresh water, minerals and oil.2 Indeed, it ranks top in the CIA World Factbook list of oil producing nations3 and has benefitted from recent increases in the price of fuel. Russia is populous and has seen steady economic growth so far in the 21st Century. Its cement industry is also growing rapidly, although it needs significant investment and consolidation to remove older, inefficient plants. Indeed, FLSmidth recently described Russia as its 'most promising' market because of the need for more efficient plants.4
Introduction
The Cold War thaws
The ideological battle between Communism and Capitalism known as the Cold War was the defining backdrop to the second half of the 20th Century. On one side was the Soviet Union (USSR) and its allies in the Eastern Bloc; on the other, the USA, Western Europe and others opposed to the spread of Communism. Both sides feared the expansion of the other's ideology and sought to contain the other through a variety of means. These included a mixture of military strategy and posturing, a conventional and nuclear arms race, espionage, the provision of aid to venerable allies, proxy wars in Afghanistan, Korea and Vietnam, diplomatic appeals to neutral countries and technological, military and economic one-upmanship.
Following a series of very conservative leaders in the USSR, Mikhail Gorbachev came to power in 1985. By this time, the Soviets were fighting a losing battle against US-supplied resistance fighters in Afghanistan, which had crystallised existing public opposition to the war there. It was also in a period of economic stagnation and widespread corruption in the government.
- Written by Dr Peter Edwards, Global Cement Magazine
With nearly 82 million inhabitants and a GDP of Euro2.5tn in 2010, Germany is both the most populous and richest nation in Europe.1,2 Although its cement production industry has been muted in recent years due to the global economic downturn, the country has a strong industrial background and is a leader in many industrial sectors, including the manufacture of cement production equipment, which has enabled strong exports to developing regions of the world.
Introduction
East and West
Following defeat of Nazi Germany at the end of the Second World War, Germany was split into two sections in 1949, with the western three quarters (Federal Republic of Germany, FRG) under the initial control of France, Britain and the USA. The north-east corner became the German Democratic Republic (GDR) under the Soviet stewardship of the USSR.
While the FRG (West Germany) was allowed to rebuild its market-based economy and become re-established within Western Europe as part of the US's Marshall Plan, the GDR (East Germany), like other Soviet states, was run to a strict planned economy with centralised production targets and wage structures.
- Written by Alan Maries & Mark Tyrer, Mineral Industry Research Organisation, Birmingham, UK
This article, based on a paper presented at the 13th International Congress on the Chemistry of Cement at Madrid in July 2011, describes a radical, step-change approach to reducing CO2 emissions from cement manufacture.
A highly novel method of cement mineral synthesis using a molten salt process yields a fine-grained product that requires little or no grinding. The specific sustainability impacts that may arise from a molten salt route have been assessed and quantified against the conventional manufacturing route in terms of resource efficiency (energy consumption and waste output), supply chain influences and management of the production process.
World-wide, mankind produces over 3Bnt/yr of cement,1,2 most of which is used to make an estimated 10km3 of concrete – more than an order of magnitude greater than the combined volume of all other man-made materials (Figure 2). Although the carbon dioxide (CO2) embodied in concrete is low (0.4t/m3) compared to other common construction materials such as glass (2t/m3), steel (10t/m3) and polymers (40t/m3),3 the sheer volume of cement produced world-wide presents a serious climate change challenge simply because of the amount of CO2 emitted during its manufacture - almost 1t of CO2 per tonne of product.
- Written by Global Cement Magazine staff
Introduction
A cement is any substance which binds together other materials by a combination of chemical processes known collectively as setting.1 Cements are dry powders and should not be confused with concretes or mortars, but they are an important constituent of both of these materials, in which they act as the 'glue' that gives strength to structures. Mortar is a mixture of cement and sand whereas concrete also includes rough aggregates (Figure 1).2,3
Because it is a major component of both of these building materials, cement is an extremely important construction material. It is used in the production of the many structures that make up the modern world including buildings, bridges, harbours, runways and roads. It is also used for facades and other decorative features on buildings. The constant demand for all of these structures, increasingly from the developing world, means that cement is the second most consumed commodity in the world after water.
