Energy Efficiency in Saudi Cement Industry

Saudi Arabia is the largest construction market in the Middle East, with large development projects under way and many more in the planning stage. The cement industry in the country is evolving rapidly and is expected to reach annual clinker production of 70 million tonnes in 2013 from current figure of 60 million tonnes per year. The cement industry is one of the highest energy-intensive industries in the world, with fuel and energy costs typically representing 30-40% of total production costs. On an average, the specific electrical energy consumption typically ranges between 90 and 130 kWh per tonne of cement. Keeping in view the huge energy demand of the cement industry, the Saudi Arabian government has been making efforts to reduce the energy consumption in the country towards a more sustainable.

Energy Demand in Cement Production

The theoretical fuel energy demand for cement clinker production is determined by the energy required for the chemical/mineralogical reactions (1,700 to 1,800 MJ/tonne clinker) and the thermal energy needed for raw material drying and pre-heating. Modern cement plants which were built within the last decade have low energy consumption compared to older plants.  The actual fuel energy use for different kiln systems is in the following ranges (MJ/tonne clinker):

  • 3,000 – 3,800 for dry process, multi-stage (3 – 6 stages) cyclone preheater and precalcining kilns,
  • 3,100 – 4,200 for dry process rotary kilns equipped with cyclone preheaters,
  • 3,300 – 4,500 for semi-dry/semi-wet processes (e.g. Lepol-kilns),
  • Up to 5,000 for dry process long kilns,
  • 5,000 – 6,000 for wet process long kilns and
  • 3,100–6,500 for shaft kilns.

Energy Efficiency in Cement Industry

With new built, state-of-the-art cement plants, usually all technical measures seem to be implemented towards low energy consumption. So, how to reduce it further?

Energy efficiency is based on the following three pillars

  • Technical optimization
  • Alternative raw materials for cement and clinker production
  • Alternative fuels

In Europe, the new energy efficiency directive from 2011 intends to reduce the energy consumption of the overall industry by 20%, achieving savings of 200billion Euros at the energy bill and with the goal to create 2 million new jobs within Europe. This approach will have a significant influence also on the cement industry. Saving 20% of the energy consumption is a challenging goal, especially for plants with state-of-the-art technology.

In older plants modernizations in the fields of grinding, process control and process prediction can, if properly planned and installed, reduce the electricity consumption – sometimes in a two digit number.

Alternative Fuels

Alternative fuels, such as waste-derived fuels or RDF, bear further energy saving potential. The substitution of fossil fuel by alternative sources of energy is common practice in the European cement industry.The German cement industry, for example, substitutes approximately 61% of their fossil fuel demand. The European cement industry reaches an overall substitution rate of at least ca. 20%.

Typical “alternative fuels” available in Saudi Arabia are municipal solid wastes, agro-industrial wastes, industrial wastes and some amount of crop residues. To use alternative or waste-derived fuels, such as municipal solid wastes, dried sewage sludges, drilling wastes etc., a regulatory base has to be developed which sets

  • Types of wastes/alternative fuels,
  • Standards for the production of waste-derived fuels,
  • Emission standards and control mechanism while using alternative fuels and
  • Standards for permitting procedures.

Alternative Raw Materials

The reduction of clinker portion in cement affords another route to reduce energy consumption. In particular, granulated blast furnace slags or even limestone have proven themselves as substitutes in cement production, thus reducing the overall energy consumption.

To force the use of alternative raw materials within the cement industry, also – and again –standards have to be set, where

  • Types of wastes, by-products and other secondary raw materials are defined,
  • Standards for the substitution are set,
  • Guidelines for processing are developed,
  • Control mechanisms are defined.

Conclusions

To reduce the energy consumption, an energy efficiency program, focusing on “production-related energy efficiency” has to be developed. Substantial potential for energy efficiency improvement exists in the cement industry and in individual plants. A portion of this potential will be achieved as part of (natural) modernization and expansion of existing facilities, as well as construction of new plants in particular regions. Still, a relatively large potential for improved energy management practices exists and can be exhausted by determined approaches.

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Environmental Best Practices for MENA Cement Industry

Cement production in MENA region has almost tripled during the last 15 years, mainly on account of high population growth rate, rapid urbanization, increasing industrialization and large-scale infrastructural development. The growth of cement industry in MENA is marked by factors that are directly connected with sustainability, energy efficiency and raw material supply. Although the factors differ from country to country and cannot be generalized, there are major concerns regarding shortage of raw materials, GHG emissions, dependence on fossil fuels and lack of investment in technological innovations.

For the MENA cement sector, key points for an environment-friendly industry are use of alternative raw materials and alternative fuels, energy-efficient equipment and green technologies. As the use of alternative fuels and raw materials is still uncommon in the Middle East, guidelines and regulatory framework have to be defined which can set standards for the use of alternative or waste-derived fuels like municipal solid wastes, dried sewage sludge, agricultural wastes, drilling wastes etc.

Sewage Sludge

An attractive disposal method for sewage sludge is to use it as alternative fuel source in a cement kiln. Dried sewage sludge with high organic content possesses a high calorific value. Due to the high temperature in the kiln the organic content of the sewage sludge will be completely destroyed. The resultant ash is incorporated in the cement matrix. Infact, several European countries, like Germany and Switzerland, have already started adopting this practice for sewage sludge management.

The MENA region produces huge quantity of municipal wastewater which represents a serious problem due to its high treatment costs and risk to environment, human health and marine life. Sewage generation across the region is rising by an astonishing rate of 25 percent every year. Municipal wastewater treatment plants in MENA produce large amounts of sludge whose disposal is a cause of major concern.

For example, Kuwait has 6 wastewater treatment plants, with combined capacity of treating 12,000m³ of municipal wastewater per day, which produce around 250 tons of sludge daily. Similarly Tunisia has approximately 125 wastewater treatment plants which generate around 1 million tons of sewage sludge every year. Currently most of the sewage is sent to landfills. Sewage sludge generation is bound to increase at rapid rates in MENA due to increase in number and size of urban habitats and growing industrialization.

The use of sewage sludge as alternative fuel is a common practice in cement plants around the world, Europe in particular. It could be an attractive business proposition for wastewater treatment plant operators and cement industry in the Middle East to work together to tackle the problem of sewage sludge disposal, and high energy requirements and GHGs emissions from the cement industry.

Use of sludge in cement kilns will led to eco-friendly disposal of municipal sewage

Use of sludge in cement kilns will led to eco-friendly disposal of municipal sewage

Sewage sludge has relatively high net calorific value of 10-20 MJ/kg as well as lower carbon dioxide emissions factor compared to coal when treated in a cement kiln. Use of sludge in cement kilns can also tackle the problem of safe and eco-friendly disposal of sewage sludge. The cement industry accounts for almost 5 percent of anthropogenic CO2 emissions worldwide. Treating municipal wastes in cement kilns can reduce industry’s reliance on fossil fuels and decrease greenhouse gas emissions.

Municipal Solid Wastes and Biomass

Alternative fuels, such as refuse-derived fuels or RDF, have very good energy-saving potential. The substitution of fossil fuel by alternative sources of energy is common practice in the European cement industry. The German cement industry, for example, substitutes approximately 61% of their fossil fuel demand. Typical alternative fuels available in MENA countries are municipal solid wastes, agro-industrial wastes, industrial wastes and crop residues.

The gross urban waste generation quantity from Middle East countries has crossed 150 million tons per annum. Bahrain, Saudi Arabia, UAE, Qatar and Kuwait rank in the top-ten worldwide in terms of per capita solid waste generation. Solid waste disposal is a big challenge in almost all MENA countries so conversion of MSW to RDF will not ease the environmental situation but also provide an attractive fuel for the regional cement industry. Tens of millions of tyres are discarded across the MENA region each year. Scrap tyres are are an attractive source of energy and find widespread use in countries around the world.

Agriculture plays an important role in the economies of most of the countries in the Middle East and North Africa region.  Despite the fact that MENA is the most water-scarce and dry region in the world, many countries in the region, especially those around the Mediterranean Sea, are highly dependent on agriculture. Egypt is the 14th biggest rice producer in the world and the 8th biggest cotton producer in the world. Similarly Tunisia is one of the biggest producers and exporters of olive oil in the world. Such high biomass production rates should be welcomed by the cement industry since these materials comprise cotton stalks, rice husks and rice straw which serve ideally as alternative fuels. However it is ironical that olive kernels – the waste from Tunisian olive production – is exported to European power plants in order to save fossil fuel-derived CO2 emissions there, while Tunisia imports approximately 90% of its energy demand, consisting of fossil fuels.

Drilling Wastes as Alternative Raw Material

The reduction of clinker portion in cement affords another route to reduce energy consumption. In particular, granulated blast furnace slags or even limestone have proven themselves as substitutes in cement production, thus reducing the overall energy consumption. The Middle East oil and gas industry has made a lot of effort in order to reduce the environmental impact of their activities. The use of drilling wastes and muds is preferable in cement kilns, as a cement kiln can be an attractive, less expensive alternative to a rotary kiln. In cement kilns, drilling wastes with oily components can be used in a fuel-blending program to substitute for fuel that would otherwise be needed to fire the kiln.

Conclusions

The cement industry can play a significant role in the sustainable development in the Arab countries, e.g. by reducing fossil fuel emissions with the use of refused derived fuels (RDF) made from municipal solid waste or biomass pellets. The cement companies in the Middle East can contribute to sustainability also by improving their own internal practices such as improving energy efficiency and implementing recycling programs. Businesses can show commitments to sustainability through voluntary adopting the concepts of social and environmental responsibilities, implementing cleaner production practices, and accepting extended responsibilities for their products.  

The major points of consideration are types of wastes and alternative fuels that may be used, standards for production of waste-derived fuels, emission standards and control mechanisms, permitting procedures etc. Appropriate standards also need to be established for alternative raw materials that are to be used for clinker and cement production.

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