Designing hollow spray scrubbers for evaporative gas cooling. Part 2. Determining scrubber geometry

Abstract

The design is based on empirical formulas proposed for determining the bulk heat-transfer coefficient. Results are given on the height of the scrubber as indicated by various models: volume heat-transfer coefficient (empirical model), evaporation time given by an interval iteration method (iteration model), and without allowance for the time needed for the droplets to attain the suspension velocity (simplified model).A method has been given [1] for designing a direct-flow hollow spray scrubber involving complete evaporation of the irrigating liquid, which enables one to determine all the input and output parameters of the two-phase gas-liquid system in the apparatus.The second part deals with designing the geometrical parameters, particularly the height H. The simplest way of solving this is based on empirical formulas [2] proposed for the bulk heat-transfer coefficient K in kW/(m 3 ·K).In that case, the working volume V of the scrubber in m 3 is defined byin which Q is the thermal load (kW), whose calculation has been given in [1], and ∆t is the temperature difference in K. For the forward flow,in which t g ′ and t g ″ are the gas temperatures at the inlet and outlet in °C; while t w is the wet-bulk thermometer temperature in °C. This t g ′ is given, while t g ″ and t w are determined during the calculations [1]. Thus one determines V and defines the diameter of the apparatus D in m to derive quite simply the working height H in m.The literature has no clear-cut recommendations on gas speed in an evaporative scrubber, but a choice must be made in order to determine D, and the literature gives only the recommended ratio of the diameter and height H/D ≈ 2.5.More accurate calculation on the working height requires one to determine the time for complete evaporation of droplets of the irrigating liquid (water).

Eco-Intensity Analysis for a Chip-Fuelled Boiler House / Ekologinio Intesyvumo Namą Šildant Skiedromis Analizė

“…In turn, heat loss through the flue gases is defined by the change in the parameters of these gases− the temperature after the boiler unit and the air consumption coefficient. Therefore, in the second equation (2) both parameters, which are assumed to be the input data for characterizing the gas condenser operation, are included: the flue gas temperatures, velocities, flows, and other characteristic factors of the eco-efficiency of the gas condenser (Val'dberg, Zhigun 2008a, 2008b.…”

Heat and Mass Transfer Processes in Scrubber of Flue Gas Heat Recovery Device

“…It should be pointed out that, in the frameworks of elementary stages, there are the same flue gas temperature changes and their geometric dimensions can be different. Data on the heat and mass transfer ratio or spraying water drops evaporation process are required for transfer to the geometric dimensions [5]. If the spraying water temperature is higher than the corresponding position of the gas dew point temperature and below the wet-bulb temperature t ū > t r > t m , then the water will evaporate and the gas moisture content will increase.…”

Analysis of Flue Gas Condenser Operation

“…The simultaneity and interaction of all these processes in combination with various factors influencing the amount of energy produced − all this adds complexity when designing the required equipment and defining its parameters [4][5][6]. This explains the great variety of devices intended to raise the efficiency of energy resources.…”