Heaters performance

WlMPRESS, N. (1978) Chem. Eng., NY 85 (May 22nd) 95. Generalized method predicts fired-heater performance. WOLVERINE (1984) Wolverine Tube Heat Transfer Data Book—Low Fin Tubes (Wolverine Division of UOP Inc.). 

Preparation of Hydroxylamine Chloride. Dissolve 7 g of sodium hydroxide in 30 ml of water and saturate the solution with sulphur dioxide to an acid reaction, after which pass the stream of gas through the solution for another five minutes (in a fume cupboard ). Add the solution dropwise with continuous stirring to a solution containing 5.5 g of sodium nitrite in 9 ml of water cooled by a mixture of ice and salt. See that the temperature does not rise above 0 °C. Pour the solution into a round-bottomed flask, dilute it to a volume of 150 ml, and heat it to boiling on an electrical flask heater. Perform complete precipitation of the sulphate ions with a solution of barium chloride prepared by dissolving 37 g of barium chloride dihydrate in 45 ml of water. 

R.N. Wimpress, Rating fired heaters. Hydrocarbon Process. 42(10), 115-126 (1963) Generalized method predicts fired-heater performance, Chem. ng., 95-102 (22 May 1978). 

Air requirements for combustion vary with the need to ensure full utilization of the fuel s heating value but not generate excessive air pollutants. The excess air required in practice depends on the type of fuel, the furnace, and the burner. Fuel oil, for instance, requires 5 to 20% excess air depending on burner design. Excess air is recognized as a routine measure of heater performance. 

Because this is an operational system, capital charges for existing equipment are irrelevant. However, it should be noted that other differential costs may be applicable to the deterioration of heater performance. For example, if the cycle efficiency decreases greatly, and if the boiler does not have sufficient overcapacity, the loss of unit efficiency will cause a decrease in maximum output and, hence, could require the expenditure of additional capital. This would result in an added monetary benefit possible through replacement of the feedwater heaters in question. 

Because the heater performance is simulated by means of temperature boundary conditions, the lack of temperature data constitutes a source of uncertainty. Other main uncertainties are related to the initial moisture distribution in the buffer and to... 

Oven Heaters. Each heater s thermal output is sensed via a thermocouple, which is used to close the loop to the heater controller. In larger, production-worthy systems, heaters are located both above and below the plane of the circuit board and are at least as wide as the conveyor. Thermal uniformity across a 60 cm tunnel width can be better than 2°C on top-of-the-line ovens. This is a function of the tunnel insulation, heater performance, heater control, and convective mixing of the heated air or gas. 

Wimpress, N., Generalized Method Predicts Fired-Heater Performance, Chem. Eng., May, 1978. 

Obtaining maximum performance from a seawater distillation unit requires minimising the detrimental effects of scale formation. The term scale describes deposits of calcium carbonate, magnesium hydroxide, or calcium sulfate that can form ia the brine heater and the heat-recovery condensers. The carbonates and the hydroxide are conventionally called alkaline scales, and the sulfate, nonalkaline scale. The presence of bicarbonate, carbonate, and hydroxide ions, the total concentration of which is referred to as the alkalinity of the seawater, leads to the alkaline scale formation. In seawater, the bicarbonate ions decompose to carbonate and hydroxide ions, giving most of the alkalinity. 

While process design and equipment specification are usually performed prior to the implementation of the process, optimization of operating conditions is carried out monthly, weekly, daily, hourly, or even eveiy minute. Optimization of plant operations determines the set points for each unit at the temperatures, pressures, and flow rates that are the best in some sense. For example, the selection of the percentage of excess air in a process heater is quite critical and involves a balance on the fuel-air ratio to assure complete combustion and at the same time make the maximum use of the Heating potential of the fuel. Typical day-to-day optimization in a plant minimizes steam consumption or cooling water consumption, optimizes the reflux ratio in a distillation column, or allocates raw materials on an economic basis [Latour, Hydro Proc., 58(6), 73, 1979, and Hydro. Proc., 58(7), 219, 1979]. 

Convective Heat Transfer Eqnipment nsiug the trne convective mechanism when the heated particles are mixed with (and remain with) the cold particles is nsed so iufreqneutly that performance and sizing eqnatious are not available. Snch a device is the pebble heater as described by Norton (Chem. Metall. E/ig., Jiily 1946). For operation data, see Sec. 9. 

Multiple-Effect Evaporators A number of approximate methods have been published for estimating performance and heating-surface requirements of a multiple-effect evaporator [Coates and Pressburg, Chem. Eng., 67(6), 157 (1960) Coates, Chem. Eng. Prog., 45, 25 (1949) and Ray and Carnahan, Trans. Am. Inst. Chem. Eng., 41, 253 (1945)]. However, because of the wide variety of methods of feeding and the added complication of feed heaters and condensate flash systems, the only certain way of determining performance is by detailed heat and material balances. Algebraic soluflons may be used, but if more than a few effects are involved, trial-and-error methods are usually quicker. These frequently involve trial-and-error within trial-and-error solutions. Usually, if condensate flash systems or feed heaters are involved, it is best to start at the first effect. The basic steps in the calculation are then as follows ... 

Figure 4.6 is interesting because it shows that for the best refining performance we need both a long zone and an impurity that is relatively insoluble in the solid (low k). Unfortunately long liquid zones can be destabilised by convection, and impurities with a low k do not come to order Commercial zone refining processes may therefore involve a large number of passes done one after the other (Fig. 4.7). This obviously adds a lot to the cost of the pure material, but the process can be speeded up considerably by using the multi-heater arrangement shown in Fig. 4.8.

Applications include high-performance insulation for wire and cables (particularly heater cables), and corrosion-resistant linings for pumps, valves, pipes and other chemical equipment. Its availability in the form of film and tubing has led to its demand for both corrosion protection and antistick applications. 

Experiments were performed in tlie SIMULAR calorimeter using the power compensation method of calorimetry (note that it can also be used in the heat flow mode). In this case, the jacket temperature was held at conditions, which always maintain a temperature difference ( 20°C) below the reactor solution. A calibration heater was used to... 

So long as water is present m the adsorbent layer, the temperature does not nse above 100 °C However, microwave heaters will even perform pyrolyses when this has evaporated... 

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