Coolers, acid

Acid Coolers. Cast Hon trombone coolers, once the industry standard (101), are considered obsolete. In 1970, anodically passivated stainless steel sheU and tube acid coolers became commercially available. Because these proved to have significant maintenance savings and other advantages, this type of cooler became widely used. Anodic passivation uses an impressed voltage from an external electrical power source to reduce metal corrosion. 

Anodic passivation and its appHcation to sulfuric acid equipment such as stainless steel acid coolers and carbon steel storage tanks has been weU studied (102—104). More recently, sheU and tube coolers made from Sandvik SX or Saramet have been installed in several acid plants. These materials do not requHe anodic protection. 

Anodic Protection This electrochemical method relies on an external potential control system (potentiostat) to maintain the metal or alloy in a noncorroding (passive) condition. Practical applications include acid coolers in sulfuric acid plants and storage tanks for sulfuric acid. 

In sulfuric acid production involving heat recovery and recovery of waste sulfuric acid, acids of various concentrations at high temperatures can be dealt with. Corrosion damage has been observed, for example, in sulfuric acid coolers, which seriously impairs the availability of such installations. The use of anodic protection can prevent such damage. 

Hydrochloric acid Production, purification, recovery, processing Bayonet heaters, heat exchangers, coils, condensers, HCl absorbers, synthetic HCl plants, acid coolers, gas coolers, chlorine burners, strippers, thermometer wells... 

Acid containers, shipping, 23 793 Acid content, of wine, 20 310 Acid coolers, in sulfuric acid manufacture, 23 779-780... 

B. Omberg and P. Crook, A New Nickel Allow and a New Semi-Welded Plate Heat Exchanger The State of the Artfor Tomorrow s Acid Coolers, Sulphur 94 (British Sulphur Conference), Tampa, Fla., Nov. 1994. 

Based on second lau analysis alternatives are worked out for improving overall energy conversion efficiency by recovering thermal energy in acid coolers for pouer generation and for preheating boiler feed uater. 

First lau analysis projects losses in sections 3 and 5 (drying and absorption) as 94.1 and 99.9 uhereas second lau analysis yields 2% and 23.5 respectively. Losses in uartn uater and stack gas are insignificant in the range of 1.4 and 0.5 based on second lau analysis compared to 52 and 1. 5 as projected by first lau analysis. Overall availability analysis of a sulphuric acid plant clearly brings out the fact that availability losses are only 4 and uhat are hitherto considered as heavy losses in acid coolers (52 as given by first lau analysis) are quite insignificant. 

In this system acid at 80°C and gases at 200°C enter cocurrently and leave the intermediate absorption touer at 110°C. This helps in increasing temperature of uarm uater from acid coolers to 75°C thus reducing availability consumption in acid coolers by 0.315 million KJ per hour. 

Boiler feed Water Preheating By preheating 5413 kg/hr of boiler feed uater, required from 100 TPD sulphuric acid plant, to 68°C using part of thermal energy available in acid coolers, 312 kg/hr of additional steam can be generated. This results in an additional availability output of 0.287 x 10° K3/hr. By this,... 

By completely recovering the thermal energy available in acid coolers, 64,400 kg/hr of boiler feed uater can be heated to 68°C. Out of this, only 5413 kg/hr is required in sulphuric acid plant and the rest can be sent to central boiler house in the complex. Availability output from sulphuric acid plant uill increase by (0.28 + 0.69) 10° Ko/hr, resulting in an overall effectiveness of 51. 5. ... 

Even though availability losses are relatively insignificant compared to consumptions, recovery of this availability from acid coolers in the form of pouer generation and boiler feed uater preheating is quite economical. 

Fig. 25.11. Sankey energy flow diagram for a 1000ton/day sulfur-burning double absorption sulfuric acid plant (feed gas 10% S02). A Blower B Sulphur furnace C Waste heat boiler D Catalyst bed 1 E Steam superheater F Catalyst bed 2 G Boiler H Catalyst bed 3 J Intermediate heat exchangers K Intermediate absorber L Converter bed 4 M Economizer N Final absorber O Air dryer P Acid coolers. (Courtsey Lurgi GmbH, Frankfurt, Germany.)...

Input acid temperature is controlled by indirect water cooling in an acid cooler, Figs. 9.5 and 24.6. 

Fig. 9.5. Acid cooler, courtesy Chemetics www.chemetics.com Cool water flows through 1610 internal 2 cm diameter tubes while warm acid flows counter currently (and turbulently) between the tubes. The tubes are 316L stainless steel. They are resistant to water-side corrosion. They are electrochemically passivated against acid-side corrosion by continuously applying an electrical potential between the tubes and several electrically isolated metal rods. Details shell diameter 1.65 m shell material 304L stainless steel acid flow 2000 m3/hour water flow 2900 m3/hour acid temperature drop 40 K. (Green pipes = water metallic pipes = acid.) Fig. 24.6 gives an internal view.

Chemetics (2004) Acid coolers, sulphuric acid technology. Brochure distributed at Sulphur 2004 conference, Barcelona, October 24-27, 2004. www.chemetics.com Also personal communication, 2005. 

Fig. 24.6. Inside an acid cooler. Fig. 9.5 gives an external view. Tubes start through the tube sheet , shown here. They extend almost to the far end of the cooler where there is another tube sheet . Cool water enters at this end and flows through the tubes to the far end. Between the tube sheets , the tubes are surrounded by warm acid moving turbulently around them. Heat transfers from the warm acid to the cool water (through the tube walls). The tube entering from the right contains a thermocouple. The polymer tubes in the foreground surround metal rods. The rods are bare between the tube sheets. An electrical potential applied between them and the water tubes anodically protects the tubes against acid side corrosion.

The cooled acid is recycled to the H2S04 making tower or sent to product storage. The warmed water is cooled with atmospheric air and recycled to the acid coolers. 

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