Preparation and the use of demineralized water for reciprocating engine-driven power plants in Azerbaijan

Abstract

Production of electric and thermal power on the basis of reciprocating engines finds an increasingly wide application in many countries of the world. These power plants equipped with internal combus� tion engines can be constructed rapidly (usually within several months). For example, a 10�MW module based on three engines can be made by Finn� ish manufacturer Wartsila in about 80 days, and its installation takes 12 days. The payback time for a power unit with the output of 1 MW and 8000 oper� ating hours per year is 2.3 years. The efficiency of reciprocating gas engines with the power capacity from 2 MW to 6 MW is 39-42% (1). In cooling systems of reciprocating engines there are also used, besides air (fan) cooling, water (closed� cycle) cooling by a mixture of desalted water, anti� freeze, and a corrosion inhibitor. It is most econom� ically advantageous and environmentally safe to produce and use demineralized water for power plants by the membrane technology. In this case the quality of desalted water meets the requirements contained in the Russian standards "Service Instruc� tion Related to Power Plants," (2, 3) which Azerbaijan adheres to as well. The cost of production of desalted water at mem� brane units is lower than when using chemical desali� nation (3, 4). Capital costs of preliminary water puri� fication prior to membrane desalination are about 60- 70% of the cost of a desalination plant, or 25-29% of the cost of process equipment needed for a water treat� ment plant (5). The volume of waste water at mem� brane desalination is equal to 25-40% of the plant capacity. In its composition the source water is con� centrated by a factor of 2 or 3, and is not corrosive. The "brine" (or effluent) is inadmissible to be discharged in sewerage (5, 6). Reagents used for membrane water purification are lowoxic, permitted to be used for potable water supply, and they are included in to the list of pollutants permitted to be discharged into water bodies, while expenditures for discharge do not exceed 0.5-1.0% of the total operation costs (6). In Azerbaijan six reciprocating gas enginedriven power plants are in successful operation (Table 1); in their cooling systems, water is demineralized by the membrane technology at the largest of them—the Sangachaly power plant. This water transported by tanker trucks is also used at the remaining five power plants.