Boilers and Condensers

Design a shell and tube heat exchanger to cool 50,000 Ib/h of diethanolamine (DEA) solution (0.2 mass fractions DEA/0.8 water) from 144°E to 113°E by using water at 77°E heated to 100°E. Assume tube inside fouling resistance, = 0.004 ft h °E/ Btu, ignoring shell side fouling resistance. 

The schematic diagram of the 1-4 shell-tube passes the heat exchanger is shown in Eigure 4.1 and the physical properties of the shell side and tube side at average pass temperature is depicted in Table 4.4. 

Assume an appropriate value of the overall heat transfer coefficient (U), the suitable designed overall heat transfer coefficient for DEA solution-water system, U is between 140 and 200 Btu/ft h °E (Table 4.1). 

Process flowsheet for 1-4 DEA-water shell and tube heat exchanger. 

Parameters Tube Side (Hot) DEA Solution (128.5°F) Shell Side (Cold) Water (88.5°F) 

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In particular, corrosion of boiler surfaces may result from the direct reaction with ferric oxide particles entering the boiler. The usual source of ferric oxide is from corroded circulation loops in HW heating boilers and condensate systems, or in pre-boiler sections in steamraising plants. 

N" Vapour handling capacity of boiler and condenser kmol/m2s nl-2t- ... 

For actual Rankine cycles, many irreversibilities are present in various components. Fluid friction causes pressure drops in the boiler and condenser. These drops in the boiler and condenser are usually small. The major irreversibilities occur within the turbine and pump. To account for these irreversibility effects, turbine efficiency and pump efficiency must be used in computing the actual work produced or consumed. The T-s diagram of the actual Rankine cycle is shown in Fig. 2.9. The effect of irreversibilities on the thermal efficiency of a Rankine cycle is illustrated in the following example. 

In our example, we obtained a rather precise fixed-capital cost estimate from a private industry with high-pressure-technology experience. This estimate, updated to year 2000, was of 600,000 EUR for the plant sketched in Fig. 8.3-2, including all costs listed in the above paragraph. In case a distillation tower was needed to obtain pure CO2 for recycling, the chemical plant would be more expensive because a flash-type separator would be substituted with a distillation tower, with boiler and condenser. 

If one wants to maximize the efficiency of the system, one can use temperature difference control, but it costs more and is usually not justified for a private home. If such controls are used, the measured variable would be the AT between the boiler and condenser waters, and one would prepare a three-dimensional plot, where the coordinates are AT, refrigerant flow, and net electricity production. The net electricity produced is the difference... 

Example 82 Determine the thermal efficiency of the power plant shown in Fig. 8.5 assuming turbine and pump efficiencies of 0.75. If its power rating is 80,000 kW wh is the steam rate from the boiler and the heat-transfer rates in the boiler and condenser... 

Although the steam generation rate is higher than was found in Example 8.1, the heat-transfer rates in the boiler and condenser are appreciably less, because their functions are partly taken over by the feedwater heaters. 

A power plant operating on heat from a geothermal source uses isobutane as the wor medium in a Rankine cycle. Isobutane is heated at 3,400 kPa (a pressure just a little below its cri pressure) to a temperature of I40°C, at which conditions it enters the turbine. Isentropic expan- in the turbine produces superheated vapor at 450 kPa, which is cooled and condensed at cons pressure. The resulting saturated liquid enters the pump for return to the heater/boiler. If the rate of isobutane is 75kgs-1, what is the power output of the Rankine cycle and what are heat-transfer rates in the heater/boiler and condenser What is the thermal efficiency of the cy... 

The exergy losses or the work losses are 79% and 21% in the boiler and condenser, respectively. In a Rankine cycle, exergy losses are due to irreversibilities occurring during heat transfer with finite temperature differences in the boiler and condenser. In order to decrease exergy losses, the temperature differences should be made smaller. Regeneration may help to decrease the temperature differences. 

A steam power plant operates on tlie cycle of Fig. 8.4. For one of the following sets of operating conditions, detemiine tlie steam rate, the heat-transfer rates in tlie boiler and condenser, and tlie tliemial efficiency of tlie plant. 

However in many heat and mass transfer processes in fluids, condensing or boiling at a solid surface play a decisive role. In thermal power plants water at high pressure is vaporized in the boiler and the steam produced is expanded in a turbine, and then liquified again in a condenser. In compression or absorption plants and heat pumps, boilers and condensers are important pieces of equipment in the plant. In the separation of mixtures, the different composition of vapours in equilibrium with their liquids is used. Boiling and condensing are, therefore, characteristic for many separation processes in chemical engineering. As examples of these types of processes, the evaporation, condensation, distillation, rectification and absorption of a fluid should all be mentioned. 

For section II, optimisation leads to concentrate the sulphuric acid up to 80% before it is converted. Finally a temperature of 850°C at the outlet of tlie converter is required. For section III, a specific column is required. It is composed of 25 theoretical plates, including re-boiler and condenser. Inlet is done at plate n° 22 at a temperature of 316°C. An intermediate partial draught at plate n° 15 is a good compromise from an energetic point of view. The total length of the catalyst bed is adjustable. 

Cold water is supplied to the condenser through e, and as it becomes heated and rises to the top, it is carried off through f. The boiler and condenser are joined. at g. 

In industrial processes heat energy is transferred by a variety of methods, including conduction in electric-resistance heaters conduction-convection in exchangers, boilers, and condensers radiation in furnaces and radiant-heat dryers and by special methods such as dielectric heating. Often the equipment operates under steady-state conditions, but in many processes it operates cyclically, as in regenerative furnaces and agitated process vessels. 

The first consideration is that the distillery be centrally located in a potato-raising country second, that there are railroad facilities for the delivery of raw materials and fuel and the marketing of the finished product at a minimum expense. An abundant supply of cold soft water is of almost equal importance. It is desirable-that the plant be near a creek or stream from which the water may be obtained and into which it may be drained after serving its purpose in the distillery. The character of the water should also be considered, and, if possible, it should be such that it will not deposit a scale.on the boiler and condenser tubes this difficulty can be overcome, however, by treating- the water witii one of the various compounds on the market for relieving such conditions. 

In the mid 1980s, a new thermodynamic power cycle using a multicomponent working fluid as ammonia-water with a different composition in the boiler and condenser was proposed (known as the Kalina cycle). The use of a non-azeotropic mixture decreases the loss of availability in a heat recovery boiler when the heat source is a sensible heat source, and in a condenser when the temperature decreases with heat exchange. Most heat input to a plant s working fluid is from variable temperature heat sources. 

In this example, the boiler and condenser are at 2000 psia and 1 psia. These have saturation temperatures of bSh F and 102 F, respectively. The average of these saturation... 

For super critical boilers, Tbou is the critical temperature. As an example, consider a plant operating at a boiler pressure of 1500 psia and a condenser pressure of 2 psia wifh 4 extraction stages. Tsat for the boiler and condenser are 597°F and 126°F, respectively. Saturation temperatures for extraction should then be, 502.8°F, 408.6°F, 314.4°F, and 220.2°F, which have saturation pressures of 697,272,83, and 17 psia. The T-s diagram for this example is in Figure 23.20. 

Thurston, Robert Henry. A History of the Growth of the Steam-Engine. Ithaca, N.Y Cornell University Press, 1939. Although very old, this book is useful because it provides a comprehensive history of the develoji-ment of steam engines, boilers, and condensers. 

Osborne Reynolds (1842-1912), an English engineer and physicist, is best known for his work in the field of hydrodynamics. His studies on condensation and heat transfer between solids and fluids brought about a revision in boiler and condenser design. He formulated the theory of lubrication, and also Investigated the transition from laminar to turbulent flow. 

Industrial chemical cleaning involves the use of reactive chemicals to remove unwanted deposits from the surfaces of various pieces of process equipment. Included are components of power-generating units such as boilers and condensers, heat exchangers in refineries and petrochemical plants, and other industrial equipment such as digesters in paper mills. The chemical removal of unwanted surface deposits is conducted for many reasons. The first reason is to eliminate scales that contribute to increased corrosion. Examples of these types of deposits include iron oxides and copper found on the watersides of many types of process equipment. The second reason is to increase heat transfer. While steel may have a thermal conductivity of... 

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