**7. Current efforts to solve fouling deposition and corrosion problems**

industry [24]. The corrosion process is affected by various parameters as show in **Figure 5**. Hence, these criteria should take consideration into the design basics of heat exchangers.

Apart from the high cost of heat exchanger fouling, very few work have been reported to accurate determine economic penalties causes by fouling. Therefore, these attribute cost to difference aspect of heat exchanger design and operation. However, reliable knowledge of fouling economics is desirable in order to evaluate the cost efficiency of various mitigation

Excessive surface area required to overcome the heavy fouling conditions, costs for stronger foundation, provision for extra spaces and increased transportation and instal-

Costs for extra fuel required if fouling leads to extra fuel burning in heat exchanging

Costs for removal of fouling deposits, costs for chemicals or other operating costs for

Planned or unplanned plant shutdowns due to fouling in heat exchangers can cause large production losses. These losses are often considered to be the main cost of fouling and

Cost for disposing large amount of chemical/additives used for fouling mitigation.

**GNP (1984) US \$ billion**

3634 0.12–0.22

**Fouling costs % of GNP**

0.28–0.35

**US \$ million**

8000–10,000

**Japan** 3062 1225 0.25 **West Germany** 1533 613 0.25 **UK** 700–930 285 0.20–0.33 **Australia** 260 173 0.15 **New Zealand** 35 23 0.15 **Total industrial world** 26,850 13,429 0.20

**Table 1.** Estimated fouling costs incurred in some countries (1992 estimation) [28].

strategies [26, 27]. The total fouling-related costs involve the following:

equipment to overcome the effect of fouling.

**6. Cost imposed due to fouling**

198 Heat Exchangers– Advanced Features and Applications

**1. Capital expenditure**

lation costs.

**3. Maintenance costs**

antifouling devices. **4. Cost of production loss**

very difficult to estimate.

**5. Extra environmental management cost**

**Country Fouling cost**

**USA** 3860–7000

**2. Energy costs**

A lot of works have been done to reduce fouling formation and control of corrosion. In recent years, numerous methods have been developed to control fouling and corrosion [29]. These methods can be classified as chemical means (inhibitor), mechanical means, changing the phases of the solution, electromagnetic fields, electrostatic fields, acoustic fields, ultraviolet light, radiation or catalytic treatment, surface treatment, green additives, fibre as a suspension, etc. In the past, chromate was a successful chemical agent for corrosion protection and crystal growth control until it was banned. Polyphosphate corrosion inhibitor was introduced for the replacement for chromate-based additives. This inhibitor has a tendency to decompose the foulant in water containing high calcium hardness. Knudsen et al. investigated fouling of high calcium water containing phosphate corrosion inhibitor. Four different copolymers were used to inhibit the deposition of calcium phosphate which includes acrylic acid/maleic anhydride (AA/MA), acrylic acid/hydroxypropyl acrylate (AA/HPA), acrylic acid/sulfonic acid (AA/SA) and sulfonated styrene/maleic anhydride (SS/MA). Studies were carried out by varying the pH, surface temperature and velocities. The investigation reported stated that AA/HPA and (AA/SA) were both very effective in inhibiting deposition of calcium phosphate and corrosion.

On the other hand, catalyst material composed of zinc and tourmaline was studied to mitigate fouling and corrosion. Tijing et al. reported that catalyst material potentially reduces calcium carbonate fouling formation [30]. Teng et al. reported the similar finding of catalyst material on calcium sulphate mitigation [31]. Moreover, Tijing et al. further extended the research by using same catalyst material to mitigate corrosion on carbon steel piping [31].

In the past, most of the methods used, chemical/additives for fouling and corrosion mitigation are hazardous to the environment. So, the days have come to apply green technology method and chemicals approaches benign to the environment [9–11].
