Cooling Tower P&id Drawing

Special Locations, Facilities, and Equipment

Dennis P. Nolan , in Handbook of Fire and Explosion Protection Engineering Principles for Oil, Gas, Chemical, and Related Facilities (Quaternary Edition), 2019

20.sixteen Cooling Towers

Cooling towers provided in nearly process industries are typically constructed of ordinary combustible materials (eastward.g., woods, fiberglass, etc.). Although abundant h2o flows through the interior of the tower, outside surfaces and some interior portions remain totally dry out. During maintenance activities most cooling towers are too not in functioning and the unabridged unit of measurement volition go dry. The principal causes of cooling belfry fires are electric defects to wiring, lighting, motors, and switches. These defects in turn ignite exposed surfaces of the dry combustible structure. On occasion, combustible vapors are released from the process water and are ignited. Water used for cooling flammable gases or ignitable liquids may plant an unusual hazard. The hazard exists when the cooling water force per unit area is less than that of the cloth being cooled. The gas or liquid can mix with the cooling h2o, be transported via the cooling h2o return line, and exist released at the belfry distribution arrangement where it can be ignited. Since cooling towers are designed to circulate high menstruation rates of air for cooling, they will likewise increase the probabilities of an electrical hotspot ignition to a flammable surface of the cooling belfry.

A meaning percentage of fires in cooling towers of combustible structure are caused by ignition from outside sources, such equally incinerators, smoke stacks, or exposure fires. Fires in cooling towers also may create an exposure hazard to adjacent structures, buildings, and other cooling towers. Therefore, distance separation from other structures, buildings, and sources of ignition, protection for the towers, and the use of noncombustible structure are main considerations in preventing these fires.

NFPA 214, Water Cooling Towers, provides guidance on the provision and design of fire protection systems and protective measures for cooling towers constructed of combustible materials. Specific protection for the interior of the cooling tower combustible materials, but also for the likely source of ignition (due east.g., motors), should exist made. Where they are critical to operations, a sprinkler system is usually provided, otherwise hose reels or monitors are installed. Loftier corrosion protection measures must be considered wherever a sprinkler system is provided for a cooling tower due to the interior environment of the cooling belfry, which is ideally suited for corrosion development to exposed metal surfaces.

In that location is an increasing industry trend to use noncombustible materials of structure for the cooling towers due to the high burn hazard characteristics and maintenance costs associated with flammable materials and fire sprinkler inspection and maintenance.

Read full affiliate

URL:

https://world wide web.sciencedirect.com/science/article/pii/B9780128160022000209

Refinery H2o Systems

Surinder Parkash , in Refining Processes Handbook, 2003

COOLING TOWERS

The cooling towers function past direct removal of heat from water by air flow and vaporizing a portion of water. Both forms of cooling are achieved past a counterflow of air and water. The towers are constructed of forest, metallic, or concrete with wood or plastic packing for distribution of the water catamenia. A portion of h2o passing over the cooling belfry is vaporized. Any solid this water contains is left behind and increases the concentration of solids in h2o. To limit the concentration of solids and preclude their deposit on cooling surfaces, it is necessary to accident down a certain percentage of circulating water. Further water loss occurs when water drifts off the tower in the wind, called drift or windage loss.

The initial step in the pattern of cooling water systems is to decide the design temperature and system capacity. The system capacity varies with design temperature equally express past process conditions. The usual cooling range is between 25 and 30°F. The inlet temperature of h2o to cooling equipment is established by ambient conditions, mostly in the range 75–86°F, and the outlet temperature is in the range 104–114°F. The blazon and quality of water set the outlet water temperature. The maximum temperature of water in the estrus exchangers must be limited to preclude corrosion and deposit of solids.

Cooling tower losses are usually evaluated every bit follows:

1.

Evaporation losses are approximately 1% of tower throughput for each 10°F of cooling tower temperature differential.

2.

Drift loss is limited in the blueprint of the cooling tower to 0.2% cooling h2o throughput.

3.

Miscellaneous liquid loss is assumed to equal fifteen% of evaporation losses minus the drift losses.

iv.

Blow-down is determined on assumption that makeup water tin be concentrated five to 6 times in the cooling tower. Accident-downward losses can be estimated approximately by the following empirical human relationship:

$B=\frac{10.7\times \Delta T\times R}{100,000}$

where

$\begin{array}{c}B=\text{blow}-\text{downwardly rate},\text{gpm};\\ \Delta T=\text{temperature differential},°\text{F};\\ R=\text{circulation rate},\text{gpm}.\end{array}$

Read full affiliate

URL:

https://www.sciencedirect.com/science/article/pii/B9780750677219500098

Utility and Offsite Systems in Gas Processing Plants

Saeid Mokhatab , ... John Y. Mak , in Handbook of Natural Gas Transmission and Processing (Fourth Edition), 2019

18.2.2.half dozen Cooling Tower Efficiency Calculations

The adding of cooling tower efficiency involves the range and approach of the cooling tower (meet Fig. 18.5). Cooling tower efficiency is express by the ambience moisture bulb temperature. In an ideal case the cold water temperature will be equal to the moisture bulb temperature. This would require a very large tower and yield huge evaporation and drift loss resulting in an impractical solution. In do the cooling tower efficiency volition be between 70% and 75% (Chemic Engineering Site, 2018). In summer the ambient air wet bulb temperature is higher than wintertime thus decreasing the cooling tower efficiency.

Effigy 18.5. Relationship betwixt cooling tower approach and range (Chemical Technology Site, 2018).

(18.1) $\text{Cooling}\text{Tower}\text{Efficiency}=\left(\text{Hot}\text{Water}\text{Temperature}-\text{Cold}\text{H2o}\text{Temperature}\right)\times 100/\left(\text{Hot}\text{Water}\text{Temperature}-\text{Wet}\text{bulb}\text{temperature}\right)$

The difference between the Cold Water Temperature (Cooling Belfry Outlet) and ambience Wet Seedling Temperature is called Cooling Belfry Approach.

(18.two) $\text{Approach}=\text{Common cold}\text{Water}\text{Temperature}-\text{Wet}\text{Seedling}\text{Temperature}$

The difference between the Hot Water (Cooling Tower Inlet) Temperature and Cold water (Cooling Tower Outlet) temperature is called Cooling Tower Range.

(18.iii) $\text{Range}=\text{Hot}\text{H2o}\text{Temperature}-\text{Cold}\text{H2o}\text{Temperature}$

So:

(18.4) $\text{Cooling}\text{Tower}\text{Efficiency}=\text{Range}/\left(\text{Range}+\text{Approach}\right)\times 100$

COC is a dimensionless number.

(18.5) $\text{COC}=\text{Dissolved}\text{Solids}\text{in}\text{Cooling}\text{Water}/\text{Dissolved}\text{Solids}\text{in}\text{Makeup}\text{Water}$

The COC normally vary from 3.0 to 7.0 depending on the process design (Chemical Engineering Site, 2018). Information technology is advisable to continue the COC as high as possible to reduce the makeup water requirement of the cooling tower. At the same time, higher bike of concentration increases the dissolved solids concentration in circulating cooling water, which results in scaling and fouling of process heat transfer equipment.

As the cooling water circulates the cooling tower, role of water evaporates thereby increasing the TDSs in the remaining water. Blow down is a part of COC. Blow down can be calculated from the following equation:

(18.half-dozen) $\text{B}=\text{E}/\left(\text{COC}-1\right)$

where B is the Accident Down (gallons per minute or cubic meters per 60 minutes), Eastward is the Evaporation Loss (gallons per minute or cubic meters per hour), and COC is the Cycles of Concentration.

Evaporation loss in cooling towers is calculated by the following empirical equation (Dark-green and Perry, 2007):

(18.7) $\text{E}=0.00085\times \text{R}\times \text{C}$

where Due east is the Evaporation Loss (gallons per minute or cubic meters per hr), R is the Range in °F, and C is the Circulating Cooling Water (gallons per minute or cubic meters per hour).

Alternatively, the evaporation loss tin exist calculated from the heat balance across the cooling belfry.

(18.8) $\text{E}=\text{C}\times \text{R}\times {\text{C}}_{\text{p}}/\text{HV}$

where E is the Evaporation Loss in gallons per minute, C is the Cycles of Concentration, R is the Range in °F, C_p is the Specific Rut (ane.0 British Thermal Unit of measurement [BTU]/lb-°F), and H_V is the Latent heat of vaporization (970 BTU/lb).

Drift loss (D) of the cooling tower is normally provided past the cooling belfry manufacturer based on the process design. If information technology is not available, it may be assumed as follows:

(18.9) $\text{For}\text{Natural}\text{Draft}\text{Cooling}\text{Tower}=\mathrm{0.iii}\text{to}1.0\times \text{C}/100$

(18.10) $\text{For}\text{Induced}\text{Draft}\text{Cooling}\text{Tower}=\mathrm{0.one}\text{to}0.3\times \text{C}/100$

(18.xi) $\text{For}\text{Cooling}\text{Belfry}\text{with}\text{Drift}\text{Eliminator}=0.01\times \text{C}/100$

The cooling tower mass residue gives an idea about makeup water requirement. Cooling tower makeup substitutes the h2o losses resulting from Evaporation, Drift and Blow down.

(xviii.12) $\text{Thousand}=\text{Due east}+\text{D}+\text{B}$

where M is the makeup water requirement in gallons per minute or cubic meters per hr, E is the Evaporation Loss in gallons per infinitesimal or cubic meters per hour, D is the Migrate Loss in gallons per minute or cubic meters per hr, and B is the Blow Down in gallons per minute or cubic meters per 60 minutes.

Read full chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B9780128158173000186

Concentrating Solar Ability☆

B. Hoffschmidt , ... P. Hilger , in Reference Module in Globe Systems and Ecology Sciences, 2021

two.4.4 Natural draft cooling towers

In the natural draft cooling tower, the necessary air mass catamenia is caused past density differences (buoyancy). Fig. five shows the function of a natural draft cooling tower with closed- and open-circuit cooling systems. The oestrus exchange surfaces are right in the lower part of the tower, producing current by buoyancy. Compared with the mechanical draft system, the advantage is that the natural draft cooling tower does not demand power for the fans. The upshot is a positive touch on on the achieved residual of the whole power station.

Fig. 5. Natural draft cooling towers: closed circuit (left) and open circuit (correct).

The natural typhoon wet cooling tower works in a like fashion as the natural draft cooling tower with airtight-circuit cooling system, but instead of the heat exchanger fill material is installed and the heat transfer mechanism functions in a different way.

Read full affiliate

URL:

https://www.sciencedirect.com/science/article/pii/B9780128197271000893

Solar Thermal Systems: Components and Applications

B. Hoffschmidt , ... P. Hilger , in Comprehensive Renewable Energy, 2012

iii.18.2.4.5 Hybrid cooling towers

The hybrid cooling tower is a combination of a mechanical draft closed-circuit system and a moisture recooling system. The warm coolant is partly injected into the cooling system; the other part is cooled down by an air-driven heat exchanger and can later be injected into the cooling system ( Figure 6 ).

Figure 6. Hybrid cooling tower.

Source: http://www.wetcooling.com.

The cooling tower can be operated according to the change in ambience temperature. At a low-level ambient temperature, only the air driven past heat exchanger is in operation. In case the ambient temperature increases, the moisture cooling system can also be activated, to reach a very low coolant temperature. Hence, issues that occur in winter in the wet cooling systems can be avoided and in summer very low coolant temperatures can exist reached. Moreover, the estrus exchanger decreases fogging caused by the moisture cooling system. When applying the hybrid driving mode, coolant consumption is considerably reduced.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B978008087872000319X

PHYSICAL FUNDAMENTALS

MARKKU LAMPINEN , ... Eric F. Curd , in Industrial Ventilation Design Guidebook, 2001

Case 13

A newspaper manufacture's cooling tower recovers heat from the outlet air. This situation is represented past the following values:

•

Inlet air enthalpy h _kane = 293 kJ/kg

•

Outlet air enthalpy h _ktwo = 208 kJ/kg (saturated 44.3°C air)

•

Outlet water temperature θ _v1 = forty°C

•

Inlet water temperature θ _vii = 5.0°C

•

H2o flow ${\dot{m}}_{\upsilon }=44\text{kg/s}$

•

Air flow ${\dot{\mathrm{1000}}}_i=44\cdot 4.186\cdot \left(40-5\right)/\left(293-208\right)=75.8\text{kg/due south}$

•

Cross-sectional area of the cooling tower A _k = 31 m² and elevation L = 3 m

It is discovered that in the cooling belfry the water moving down from the jets changes its management to up subsequently drop formation. There is an effective estrus transfer process when the drops move upward: heat transfers from the outlet air to the drops through convection and condensation.

Drops collide with the drop separator and drain downwards to the lower part of the belfry. These drops are large, so their full surface area is pocket-sized and insignificant. The effective oestrus transfer procedure takes place when the drops motility with the air flow, and so this arrangement has to exist treated equally a parallel flow heat transfer.

(a)

Calculate αAp. Co-ordinate to the parallel flow principle, the state of affairs is as shown in Fig. 4.xx.

Effigy iv.20. Heat transfer according to the parallel flow principle.

First we summate the logarithmic enthalpy difference:

$\begin{array}{l}{h^{\prime }}_{\mathrm{one\; thousand}}({\theta }_{v\mathrm{ane}})={h^{\prime }}_{\mathrm{1000}}(5{}^o\text{C})=\mathrm{eighteen}\text{k}\text{kJ/kg}\\ {h^{\prime }}_{\mathrm{thou}}({\theta }_{\mathrm{five}2})={h^{\prime }}_{\mathrm{one\; thousand}}(\mathrm{xl}{}^o\text{C})=168\text{kJ/kg}\end{array}$

and

$\Delta {\mathrm{grand}}_{g\text{In}}=\frac{(293-18)-(208-168)}{\text{In}\frac{293-\mathrm{eighteen}}{208-168}}=121.9\text{\hspace{0.17em}kJ/kg}$

The specific heat chapters of humid air calculated per kilogram of dry air is

$\begin{array}{l}{c}_p\mathrm{grand}=c{p}_i+x{c}_{ph}=\mathrm{one.006}+08\cdot 1.85=\mathrm{one.154}\text{\hspace{0.17em}kJ/kg}{}^o\text{C}\\ {\text{c}}_p=\frac{{\rho }_i}{\rho }{c}_p\mathrm{thousand}=1.154(\text{kJ/kg}{}^o\text{C})\end{array}$

From Eq. (4.153),

$\begin{array}{l}\alpha A=-\frac{c_p}{\Delta h_{\text{kIn}}}{\dot{m}}_v{c}_{pv}(t_{5\mathrm{i}}-t_{v\mathrm{two}})=\frac{1.154}{121.9}\cdot 44.0\cdot \mathrm{four.186}\cdot (\mathrm{five}-40)\\ =61.0\text{\hspace{0.17em}one thousand}W\text{/}{}^o\text{C}\end{array}$

On the other paw, AA_p A _k L, and therefore

$\alpha Ap=\frac{61.0\text{\hspace{0.17em}k}\mathrm{West}\text{/}{}^{\text{o}}C}{A_{\mathrm{thousand}}-L}=\frac{61.0}{31.3}=0.656\text{\hspace{0.17em}m}\mathrm{Westward}\text{/}{}^{\text{o}}C{\text{\hspace{0.17em}thou}}^3$

(b)

The same cooling belfry is to function as a water cooler. Let the outdoor air exist 24°C, φ = 50%, and the air period 100 kg/south (dry out air). The water inlet temperature is 24°C and the water flow xxx kg/s. What is the cooling capacity if we presume that $\alpha -\sqrt{{\upsilon }_i}$ and $A_p\sim {\dot{\mathrm{1000}}}_{\upsilon }$ , or $\alpha A_p=\mathrm{thou}\sqrt{v_i}{\dot{g}}_v$ and also that the active cooling process is parallel-flow heat transfer?

For instance (a) was 44 kg/southward and the air menstruum velocity = (75.v/i.0)/31 = 2.44 grand/south. Therefore the heating capacity (or cooling capacity, depending on the sign) can be presented as

$\varphi =\frac{\alpha A_p{A}_{k}L}{c_p}\Delta h_{\text{kIn}}=\frac{\mathrm{chiliad}\sqrt{5_i}{\dot{\mathrm{one\; thousand}}}_v}{c_p}{A}_k\mathrm{50}\Delta h_{\text{kIn}},$

and solving factor one thousand out of this equation,

$\mathrm{thousand}=\frac{c_p\varphi }{\sqrt{{\mathrm{five}}_i}{\dot{\mathrm{thousand}}}_v{A}_{k}L\Delta h_{\text{kIn}}}=\frac{1.154\cdot (44.0\cdot 4.186\cdot (\mathrm{twoscore}-5))}{\sqrt{\mathrm{ii.44}}\cdot 44.0\cdot 31.0\cdot \mathrm{three}\cdot 121.9}=\mathrm{nine.55}\cdot {10}^{-3}\cdot$

Then the capacity ϕ is

$\varphi =\frac{m}{c_p}\cdot A_{\mathrm{grand}}L\cdot \sqrt{v_i}{\dot{m}}_v\Delta h_{\text{kIn}}=\frac{9.55\cdot {10}^{-3}}{1.154}\mathrm{.31.three}\cdot \sqrt{v_i}{\dot{m}}_{\mathrm{five}}\Delta h_{\text{kIn}}$

and after calculations,

$\varphi =0.770\cdot \sqrt{5_i}\cdot m_v\cdot \Delta h_{\text{kIn}}$

where v _i is in m/s, ${\dot{\mathrm{thou}}}_{\upsilon }$ in kg/s, Δh _kln in kj/kg, and ϕ is in kW. It was institute that ${\dot{m}}_{\upsilon }=30\text{kg/south}$ and ${\dot{m}}_i=100\text{kg/s}$ , and at present five _i , ≅ (100/one.two)/31 =2.69 m/due south. Thus

$\varphi =0.770\cdot \sqrt{2.69}\cdot \mathrm{thirty.0}\cdot \Delta h_{\text{kIn}}=37.9\cdot \Delta h_{\text{kIn}}$

The cooling belfry operation in an air cooling state of affairs is illustrated in Fig. 4.21. Considering of the logarithmic enthalpy difference the solution must be iterated:

FIGURE 4.21. Water cooling In a cooling tower, which operates according to the parallel flow principle; In other words, the water spray turns In the management of the air flow.

one.

Guess:

$\begin{array}{l}{\theta }_{v\mathrm{ii}}=20{}^{\text{o}}C\text{;}{h^{\prime }}_{\mathrm{one\; thousand}}\left(20{}^{\text{o}}C\right)=57.9\text{kJ/kg}\\ \varphi \text{=30}\cdot \text{4}\text{.186}\cdot \left(24-20\right)=502\text{kW}\\ h_{k2}-h_{k\mathrm{one}}=502/100=5.02\text{kJ/kg;}{h}_{k2}=53.3\text{kJ/kg}\\ \Delta h_{\text{kIn}}=\frac{24.1-\left(57.9-53.3\right)}{\text{In}\frac{24.1}{\mathrm{57.ix}-53.3}}=11.8\text{kJ/kg}\\ \varphi \text{=37}\text{.9}\cdot \text{eleven}\text{.8=446}\text{kW}\\ h_{k2}=24-446/\mathrm{xxx}\cdot 4.186=20.4{}^{\text{o}}C\end{array}$

2.

Nosotros choose

$\begin{array}{l}{\theta }_{52}=\left(20.0+20.4\right)/2=\mathrm{xx.2}{}^{\text{o}}C\text{;}{h^{\prime }}_k\left(20.2{}^{\text{o}}C\right)=\mathrm{58.vi}\text{kJ/kg}\text{.}\\ \varphi \text{=xxx}\text{.4}\text{.186}\cdot \left(24-\mathrm{xx.two}\right)=477\text{kW}\\ h_{k2}=48.3+477/100=53.1\text{kJ/kg}\\ \Delta h_{\text{kIn}}=\frac{24.1-\left(\mathrm{58.vi}-53.1\right)}{\text{In}\frac{24.1}{58.6-53.1}}=\mathrm{12.half-dozen}\text{kJ/kg}\\ \varphi \text{=37}\text{.9}\cdot \text{12}\text{.6=477}\text{kW}\end{array}$

Now θ _v2 = 20.2°C and cooling capacity ϕ = 477 kW.

When the cooling tower was operating as a rut recovery device, its capacity was considerably higher because of the high temperatures and humidities. In case (a) we had

$\varphi =44\cdot (40-\mathrm{v})\cdot 4.186=6450\text{\hspace{0.17em}thousand}\mathrm{Westward}\cdot$

If we assume that the outlet air is saturated, the air state alter process is as presented in Fig. 4.22. The verbal determination of the air humidity at the end of the procedure would need carve up mass and rut transfer examinations.

FIGURE 4.22. H2o cooling in a cooling tower.

Read full affiliate

URL:

https://www.sciencedirect.com/science/article/pii/B9780122896767500072

Reliability, Availability, and Maintainability (RAM Analysis)

Dr Eduardo Calixto , in Gas and Oil Reliability Engineering (Second Edition), 2016

Electric System Modeling

The electric subsystem includes a set of gas-powered motor generators, Lite supply, and diesel oil-powered motor generators, with at least one of the generation subsystems operating for electrical power supply. The components of the distribution organization are transformers, excursion breakers, cables, and buses, equally shown in Fig. 4.threescore.

Figure iv.lx. Electrical subsystem modeling.

Electric system availability is 100% in 200,000   hours of operation, programmed maintenance and inspection hours not included. This means that the system is available 100% of the time throughout 200,000   hours. Organisation reliability was R(200,000)   =   99%. This ways that the probability that the system volition piece of work in accord with its established tasks is 99%. It is worth mentioning that the availability reached is owed to system redundancies and maintainability, where repairs are conducted within expected times and components are available with a high caste of restoration, so that equipment operating conditions after interventions are as skilful every bit new.

Studying the reliability alphabetize, Light and diesel subsystems offering a dandy opportunity for reliability comeback. For each 1% improvement in the Light subsystem there volition be 0.995% of system improvement.

Mathematically, the reliability index is:

$\frac{\partial R\left(\text{CIPD}\right)}{\partial R\left(\text{Light}\right)}=\text{RI}$

Water Cooling Subsystem Modeling

The water cooling subsystem includes the cooling tower, pumps, and components going all the way upwards to the chillers. This system is responsible for keeping chillers at an ideal operating temperature. Thus, upon failure of this subsystem, chillers volition stop because of overheating, causing unavailability of the cold h2o system and of the CIPD.

The cooling subsystem is a closed h2o circuit between the cooling towers and chillers. The sets of belfry equipment and components, pumps, and chillers are in serial, and it is essential that these components work as good as required to avoid organization unavailability. Fig. 4.61 shows four lines of equipment going from the cooling belfry to the fix of pumps and from there to the chillers.

Figure 4.61. Water-cooling subsystem modeling.

Availability for 200,000   hours (A(200,000)   =   one) is 100%, that is, the arrangement will exist available all 200,000   hours. System reliability is 91% (R(200,000)   =   91.2%). This proves that system redundancies allow for high availability even if in that location is a failure.

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B978012805427700004X

Industrial waters

In Membranes for Industrial Wastewater Recovery and Re-employ, 2003

Biological growth

The warm, moist environment in cooling towers coupled with the availability of nitrogen, phosphorus, and organics provides an platonic environment for microbial growth. Typically, microbial growth results in biofilm formation and fouling, in which microbial products encourage the attachment and growth of heterogeneous deposits containing both microorganisms and inert materials, on rut exchanger surfaces. These biofilms then interfere with rut transfer and water menses. During extended operating periods, portions of the biofilm slough off of the surface. This microbial biomass contains particles and other droppings that can settle, further inhibiting effective heat transfer. Some types of microorganisms release corrosive by-products during their growth such as organic acids (e.g. acetic) or inorganic acids (e.g. hydrogen sulphide) leading to microbially induced corrosion (MIC), a phenomenon exacerbated by standing water conditions.

Bacteria that may be present in cooling water include Pseudomonas, Klebsiella, Eneterobacter, Acinetobacter, Bacillus, Aeromonas, and Legionella (Adams et al., 1978; Wiatr, 2002). Once a biofilm forms, it provides a protective habitat for microorganisms (Fig. 3.xiv). Biocides can be used to control biofilms equally office of the internal chemical treatment process, the blazon and required dosage depending on the organic and nutrient content of the make-upward water. The most normally used biocide is chlorine, though other chemical approaches are also effective. Ozone is a powerful biocide effective for control of bacteria, viruses, and protozoa, but tin exacerbate issues of scale adhesion since by-products from the oxidation of biofilms tin serve equally bounden agents for scale on heat exchanger surfaces.

Figure three.14. Electron micrograph of biofilm structure. The length of the white bar represents 10 μm

When reclaimed water is used for cooling, the assurance of adequate disinfection is a primary business concern to protect the wellness of workers and individuals exposed to aerosols from the cooling towers. The disinfection requirements for the use of reclaimed h2o in cooling towers are site specific and based on the potential for exposure to aerosols from cooling operations and prevention of biofilm growth. Limited data are available on relative quantities of microorganisms in recirculating cooling systems. Pathogen survival depends on the source water quality, pretreatment mechanisms, and the type and dosages of biocides used in the facility (Levine et al., 2002). While in that location are no universal standards, the most frequently monitored leaner include full and faecal coliforms and Legionella Pneumophilia. Typically affliction outbreaks are associated with levels over grand cfu (colony forming units) per ml in cooling towers. A comparison of the levels of Legionella Pneumophilia in recirculated cooling water is shown in Fig. 3.15. This facility uses a pro-active approach by conducting quarterly monitoring. Typical values range from non-detectable to 300 cfu ml^−one. Monitoring can provide insight into the effectiveness of disinfection practices.

Effigy 3.15. Seasonal variations in Legionella Pneumophilia in cooling water

(data from Raytheon Corporation in Petrograd, Florida)

Water velocities beneath 0.3 thou due south⁻¹ and temperatures over 50°C tend to promote biofilm formation and the associated fouling reactions. Control of fouling is accomplished by the addition of chemical dispersants to preclude particles from accumulation and subsequently settling. Also, a secondary benefit of chemical coagulation and filtration processes is the removal of some contaminants that contribute to fouling.

The critical function played by biofouling in determining wastewater reuse capability has been recognised in all-encompassing studies carried out in Grangemouth, Scotland (Glen, 2002). Grangemouth is one of the largest industrial complexes in the Great britain, with major petrochemical industries concentrated in a small surface area. H2o consumption is 26 one thousand thousand m^three per year, costing business around $24 m per annum at (2002 dollars), with ane of the main uses beingness for heat commutation systems. To appraise fouling propensity of possible feedwater sources the National Engineering Laboratory based at Grangemouth have developed device for assessing biofilm formation through thermal resistance measurements. Results so far have revealed fouling rates of recovered municipal effluent to be generally higher than other sources, such as culvert h2o, and highly dependent on period velocity. On the other paw, examples be of employing membrane treatment for the production of boiler feedwater from secondary municipal effluent (Department 5.1).

Read total chapter

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B9781856173896500047

Effects of Toxic Chemicals and Other Pollutants on Aquatic Ecosystems

Walter K. Dodds , in Freshwater Ecology, 2002

THERMAL POLLUTION

Research has been conducted on the influence of cooling tower effluent (warm h2o) on aquatic communities. In addition, some reservoirs artificially warm downstream waters when outflow is from the epilimnion or the reservoir is shallow. Reservoirs with deep hypolimnia and hypolim-netic release tin yield colder water than would be natural. Hot springs are discussed later. The data on thermal furnishings may prove useful when considering the effects of global warming on aquatic ecosystems.

Increases in temperature cause an increase in growth charge per unit up to a indicate. Above some threshold, damage occurs. When thermal pollution is released into wetlands, copse can exist killed. As temperatures increase, green algae and diatoms are replaced by cyanobacteria. One of the central issues in thermal pollution is the replacement of cold-water fishes with warm-h2o fishes. Finally, rapid changes in temperature associated with ability plant operations can kill fish by thermal shock (Ottinger et al., 1990). Mitigating the thermal effects of power establish effluent obviously has a meaning fiscal cost.

Read total affiliate

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B9780122191350500155

Waste product Minimization Data/Information Requirements—A General Approach For Manufacturing

Paul N. Cheremisinoff P.E., D.East.Eastward. Professor , in Waste Minimization and Toll Reduction for the Process Industries, 1995

Cooling H2o

□

One time–through or recirculating blazon

□

Number of cooling towers and the following details of each cooling tower

□

Servicing plant

□

Recirculation charge per unit

□

Brand upward

□

Blow down

□

Concentration factor

□

Temperature drop

□

Workout chemicals

inhibitors

biocides

□

Holding chapters of basin and loop

□

Contagion of cooling water by leakage in the process contaminants

concentration of contaminants in cooling water mg/l.

□

Circulating h2o analysis of all the cooling towers (range)

□

Side stream filters are provided

which h2o is used for filter dorsum–launder

frequency

quantity

Analysis – particularly suspended solid content of discharged dorsum–launder water (range)

Read total chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780815513889500051

agnewtrater83.blogspot.com

Source: https://www.sciencedirect.com/topics/earth-and-planetary-sciences/cooling-tower

Share this post