الفهرس 
acknowledgmentOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
Abstract
I. INTRODUCTION
Water and energy are interrelated, as, in order to convert no usable water into fresh water, energy has to be consumed, whereas water, on the other hand, is by itself a powerful source of energy. Water is also a powerful matter of life, as no life without water is possible. The importance of water as a matter of life is quoted as back as there are records in history. Water and civilization are also two inseparable conceptions, as towns and countries have developed and flourished along rivers and lakes, as water is a source of life (1). Ancient Egypt is a typical historical example of the influence of a river’s water to the birth and development of a civilization. Herodotus (484–425 BC) the Greek historian and Hecateaus of Militus (about 500 BC), Greek historian and geographer, the founder of the study of geography, considered Egypt as “the gift of the river”, because by observing the behavior of the river Nile the Egyptians learned to determine the seasons of the year, creating thus the first calendar from which the modern one arose. However, history presents also many examples where lack of water is the cause of no progress in evolution, or of illness suffering and death, a situation nowadays still encountered in large parts of our world.
Water is an abundant natural resource that covers three quarters of the earth’s surface. The oceans represent the earth’s major water reservoir. About 97% of the earth’s water is seawater while another 2% is locked in icecaps and glaciers. Available fresh water accounts for less than 0.5% of the earth’s total water supply. Vast reserves of fresh water underlie the earth’s surface, but much of it is too deep to access in an economically efficient manner. Additionally, seawater is unsuitable for human consumption and for industrial and agricultural uses (2). Desalination of sea and brackish water is therefore attracting considerable attention in the scientific and engineering communities where the availability of water cannot be increased by using conventional resources or by recycling or cannot be made available by demand management methods. Its commercial application is changing the face of regions such as the Middle East, North Africa and some islands of the Caribbean.
Thirty-four countries in Africa, Asia, and the Middle East are currently classified as ”water stressed”, which means that their renewable water resources have dropped below about 1700 m3/capita. Furthermore, about 470 million people currently live in regions where severe water shortages exist, e.g., northern China, northern Africa, the Middle East, northern India, parts of Mexico and western United States. By 2025, the number of people living in water stressed countries is projected to increases to three billion more than a six fold increase (3) and four billion people by 2050 (4). In Egypt, rapid industrial growth and the population increase in rural areas has resulted in a large escalation of demand for fresh water. According to some studies, the demand for potable water in Egypt is estimated to be 12.9 x109 m3/year in the year 2025, i.e., it is expected to be about 3.5 times the present demand of 3.7x109 m3/year (5). where water is scarce in remote areas and deserts, small communities still practice primitive local techniques for harvesting and/or water mining.
Desalination nowadays is a mature techno-economic application. This technological achievement started early, immediately after World War II, in the beginning of 1950, by scientists and engineers, the desalination pioneers, who established the desalination applications of today (1). Desalination is becoming a solution for water scarcity in most arid countries where structural water shortage is a permanent phenomenon. Such countries are the Arabian Gulf States, which have 50% of the total installed plant desalination capacity and other small islands all over the world. Countries that have exploited their limited natural water resources with no more sources to develop turn to desalination as an alternative. Such countries are Israel, Cyprus, and Jordan.
Desalination, as a general definition, is the process of removing salt from saline water in order to bring salinity to levels consistent with needed standards. The major function of the process is to remove essentially salt content or salinity of water. However, the desalination process separates nearly salt-free water from sea or brackish water. The salinity of water source is measured in terms of “total dissolved solids” (TDS), which is commonly reported in milligrams per liter (mg/l). Freshwater normally has less than 1,000 mg/l TDS. Raw water for desalination can be seawater from ocean or from shallow beach wells, brackish water (surface or aquifer), wastewater, and even water produced by oilfields. Water can be classified into four categories based on the salt content in it. They are:
• recycled water with less than 1,500 mg/l TDS;
• slightly saline water with 1,000–3,000 mg/l TDS;
• moderately saline water with 3,000–10,000 mg/l TDS;
• highly saline water with over 10,000 mg/l TDS.
Generally, brackish water normally refers to water with salinities between 1,000 and 10,000 mg/l TDS. The salinity of seawater is in the order of 35,000 mg/l TDS (or average salinity 3.5%). The US Environmental Protection Agency (US EPA) and the World Health Organization (WHO) established a TDS guideline of 500 and 1,000 mg/l, respectively, for drinking water (6). In addition, silt density index (SDI) is another important parameter. SDI is a measure of the amount of 0.45-mm filter plugging that is caused by passing a sample of water through the filter for 15 min. It must be determined for water that is considered for reverse osmosis (RO) and electrodialysis (ED)/electrodialysis reversal (EDR) treatment. SDI is also used for the evaluation of product water. The ranges of concentration of TDS in the water to which different desalination processes can be applied economically are shown in Table 1 below:
Table 1: Range of concentrations to which different desalination processes can be applied.
Desalination process TDS concentration range (mg/l)
Ion exchange 10-800
Reverse osmosis 50-50,000
Electrodialysis 200-10,000
Distillation or thermal processes 20,000-100,000
The desalinated water is recovered for consumption where the salts are concentrated in a stream of water called the brine reject, disposed either to the sea or to a saline aquifer or in evaporation ponds. The water desalination processes require significant quantities of energy to achieve the salt separation and to get fresh water. The amount and shape of the energy required differs according to the used technique in water desalination. A typical flow diagram of the process with inputs and outflows is shown in Fig. 1. Desalination of sea (or saline) water has been practiced regularly for over 50 years and is a well-established means of water supply in many countries. It is now feasible, technically and economically, to produce large quantities of water of excellent quality from desalination processes (7). However, increasing environmental cost has motivated the development of new desalination design methodologies that enable a reduction of emissions to the environment. As part of the emissions reduction, water and wastewater minimization to minimize freshwater consumption and wastewater generation have become increasingly important (8).
Desalination of brackish and seawater is expanding rapidly, primarily to support industrial developments in arid and semi-arid areas and in remote areas where water is not available or it is too costly to transfer or develop. The desalination of water has been practiced since ancient times but was not widely used due to technological limitations, the prohibitive high capital costs, high-energy consumption and finally very high unit cost when compared to conventional water. New technological advances in the last 40 years tremendously reduced the capital cost and the energy consumption so that desalination projects can be considered as alternative solutions to water development. However, desalination projects are still not very cheap to be easily accommodated by the economies of many countries, energy consumption is still comparatively high, and acceptance of such projects is questioned by environmentalist, politicians, engineers and other groups of the population on economic, social and environmental issues.
Figure 1: General process for production of fresh water by desalination processes.
Water used in power plants, petrochemicals plants and other industries needs moderate to severe treatment, depending on its quality that needed for specific purpose. Generally, three basic techniques are employed for the high water purity demanded by most industries. Firstly water softening, i.e. the removal of hardness (calcium and magnesium). Secondly, dealkalization, i.e. removal of alkalinity (bicarbonates and carbonates) together with hardness. Thirdly deionization or demineralization, i.e. removal of cations and anions from the raw water.
There are thousands of demineralizer units around the world that provide high purity water for boilers, turbines, industrial and commercial processes. Many of these demineralizers are over 25 years old (9). In almost all cases, raw water composition, flow rates, daily throughput requirement and treated water quality have all changed. Today, these demineralizers are working harder than ever. As expected, the owners are experiencing substantial increase in regeneration chemical costs, increase in waste water volumes, and operation and maintenance costs. Such frustrated owners faced with the task of updating their systems often consider retrofitting or replacing the entire system with newer technologies, which may cost even more in the long run.
The desalination experience in Egypt is relatively new compared to other countries, especially in the Gulf States. Egypt’s desalination experience began a long time ago with a large distillation pond for domestic uses in Helwan (south Cairo), then in the period 1975 to 1982, three different models of Electrodialysis (ED) plants were installed in Egypt (7), and they differed in capacity (from 50 to 1000 m³/day), and salinity levels (between 2000 to 10000 ppm) of the feedwater (i.e. the water being fed into plants for desalination), and recently thereafter RO became more common, attractive and cost effective. Most of the private sector use RO plants in resort areas. The Egyptian experience is rapidly building up in this field, but more efforts are needed to cope with the world trend to reduce the cost of desalination to a minimum. Seawater desalination is still given low priority when considering alternative methods of increasing Egypt’s water supply. This is mainly due to the high cost of seawater treatment compared to non-conventional water resources (e.g. drainage reuse), where the average cost of desalination of one cubic meter of seawater ranges between L.E 3 to L.E. 7. In some cases, it is more feasible to use desalination to provide domestic water, especially in remote areas where the water supply networks construction and maintenance costs required to transfer Nile water is relatively high. Also, brackish groundwater having a salinity of about 10,000 ppm can be desalinated at a reasonable cost providing a possible potential for using desalinated water in agriculture, and hence desalination is most attractive in remote areas in Egypt where either seawater and/or brackish water exist (10). In addition, most of power plants, petrochemicals plants, fertilizers plants and other industries in Egypt are based on desalination of brackish water for industrial applications such as steam generation through boilers and for different cooling purposes. The amount of desalinated water in Egypt now is in the order of 50 millions of m3/year.
Abu Qir Fertilizers and Chemical (AFC) Industries Co. is an Egypt-based Company engaged in the agricultural chemicals sector. AFC was established in 1976 as a public enterprise company and is based in Alexandria, Egypt. Recently it followed Law No.159 for year 1996 as an Egyptian Joint Stock Company. The Company focuses on the production, distribution and export of chemical fertilizers and related products. The Company’s products include Prilled Urea, Prilled Urea treated with Zinc Sulphate, Granular Ammonium Nitrate, Granular Urea, Granular Urea treated with Ammonium Sulphate, Granular Urea treated with Magnesium Sulphate, nitrogen, phosphorous and potassium (NPK) products, liquid mixture of urea and ammonium nitrate (UAN) and liquid ammonia. The company also operates a training center that provides vocational training and human development services for fertilizers and petrochemical companies in Egypt and the Middle East. The company operates three manufacturing plants, namely Abu Qir Plant I (AQ-I), Abu Qir Plant II (AQ-II) and Abut Qir Plant III (AQ-III). In 1979 AQ-I commenced operations for the purpose of upgrading ammonia into urea. Then, in 1991 AQ-II was established to produce ammonium nitrate and finally, in 1998, AQ-III. Data for each of the process plants are summarized in Table 2. Abu Qir Fertilizer dominates the domestic market with a share of 70% and in addition has vast export potential to international markets. AFC for ammonia/urea becomes more and more known in the fertilizer industry. Projects in the past have shown production increases, energy savings and steam export increases. AFC not only pushes the plants to the operational limits but also stabilizes the plant so that less operator interventions are needed, less alarms are generated. This means that operators can focus on more things besides ‘keep the plant running’.
Table 2: The main chemicals of fertilizers production capacities in AFC.
Abu Qir I plant, (AQ-I):
Ammonia output
Urea output
Process licensors
Main product
Date on-stream
1,100 mtpd
1,550 mtpd
Krupp Uhde (Ammonia) & Stamicarbon (Urea)
Prilled Urea 46.5%-N
1979
Abu Qir II plant, (AQ-II):
Ammonia output
Nitric acid output
Ammonium nitrate (AN) output
Process licensors
Main product
Date on-stream
1,000 mtpd
1,800 mtpd
2,400 mtpd
Krupp Uhde (Ammonia) & Hydro Agri
Fertilizer grade AN 33.5%-N
July 1991
Abu Qir III plant, (AQ-III):
Ammonia plant output
Urea plant output
Process licensors
Main product
Date on-stream
1,200 mtpd
2,000 mtpd
Krupp Uhde, Stamicarbon & Hydro Agri
Granulated Urea 46.5%-N
January 1999
(mtpd, metric ton per day)
The assessment of the water treatment and desalination techniques for steam generation in AFC has been studied. The design of treatment and desalination units (water utilities units) are similar for the three plants in AFC except that AQ-I plant have electrodialysis reversal unit (EDR) which not installed in the other two plants (AQ-II and AQ-III plants). Thus the study will focus on the water processes at AQ-I site only because it is the oldest commenced plant as well as to evaluate the efficiency of treatment and desalination units after this long period of operation (since 1979).