scholarly journals Tubular Heat Exchanger Fouling in Phosphoric Acid Concentration Process

2020 ◽  
Author(s):  
Rania Jradi ◽  
Ali Fguiri ◽  
Christophe Marvillet ◽  
Mohamed Razak Jeday
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Phosphoric Acid ◽  
Acid Concentration ◽  
Fouling Resistance ◽  
Tubular Heat Exchanger ◽  
Concentration Process ◽  
Phosphoric Acid Concentration

Fouling in phosphoric acid concentration is a persistent operational problem that compromises energy recovery in this process. Progress is hampered by the lack of quantitative knowledge of fouling dynamic effects on heat exchanger transfer. The object of this work is an experimental determination of the thermal fouling resistance in the tubular heat exchanger of phosphoric acid preheated installed in phosphoric acid concentration process. By measuring the inlet and outlet temperatures of phosphoric acid, steam temperature, suction and discharge pressure of the pump and acid density measurement, the overall heat transfer coefficient has been determined. The determination of the overall heat transfer coefficient with clean and fouled surfaces, allowed calculating the fouling resistance. The results from the heat exchanger studies showed that the fouling resistance increased with time and presented an asymptotic evolution in compliant with the proposed model by Kern and Seaton, with the existence of fluctuation. The poorly cleaned heat exchanger implied the absence of the induction period and caused, consequently, high values of the fouling resistance in a relatively short-time period.

scholarly journals Study of fouling in graphite blocks (cross flow) heat exchanger of phosphoric acid concentration process

2020 ◽  
Vol 330 ◽  
pp. 01038
Author(s):  
Rania Jradi ◽  
Christophe Marvillet ◽  
Mohamed Razak Jeday
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Phosphoric Acid ◽  
Transfer Coefficient ◽  
Acid Concentration ◽  
Fouling Resistance ◽  
Concentration Process ◽  
Overall Heat Transfer Coefficient ◽  
Phosphoric Acid Concentration

Fouling in phosphoric acid concentration process of preheat exchangers is a chronic operational problem that compromises energy recovery in these systems. Progress is hindered by the lack of quantitative knowledge of the dynamic effects of fouling on heat exchanger transfer. The subject of this work is an experimental determination of the thermal fouling resistance in the graphite blocks heat exchanger installed in a phosphoric acid concentration process. By measuring the inlet and outlet temperatures and mass flows of fluids, the overall heat transfer coefficient has been determined. Determining the overall heat transfer coefficient for the heat exchanger with clean and fouled surfaces, the fouling resistance was calculated. The results obtained from the heat exchanger studied, show that the fouling resistance increase with time presenting an exponential evolution in agreement with the model suggested by Kern and Seaton, with the existence of fluctuation caused by the instability of the flow rate and the temperature. Bad cleaning of the heat exchanger involves the absence of the induction period and consequently, causes high values of the fouling resistance and of the deposit fouling during a relatively short period of time.

Multiple Regression Corrosion Models and Corrosion Mechanism of High Chromium Cast Iron under Phosphoric Acid Medium Condition

2014 ◽  
Vol 941-944 ◽  
pp. 1367-1371
Author(s):  
Liu Jie Xu ◽  
Bao Yuan Li ◽  
An Heng Si ◽  
Shi Zhong Wei
Keyword(s):  
Weight Loss ◽  
Cast Iron ◽  
Phosphoric Acid ◽  
Acid Medium ◽  
Acid Concentration ◽  
Corrosion Property ◽  
High Chromium ◽  
High Chromium Cast Iron ◽  
Chromium Cast Iron ◽  
Phosphoric Acid Concentration

The corrosion property of high chromium cast iron was test under different phosphoric acid medium concentration. On the base of experimental data, the binary equation model of corrosion weight loss (W) versus phosphoric acid concentration and corrosion time (c, t) was built using multiple regression analysis, which can predict corrosion property of high chromium cast iron effectively. The prediction results show that the corrosion weight loss rises lineally with increasing corrosion time, and the corrosion rate rises quadratically with increasing phosphoric acid concentration. The corrosion failure mechanism is that chromium composite carbides (M7C3) stand out of matrixes surface after the matrixes composed of martensite and austenite are corroded firstly, then the M7C3 carbides drop out of matrixes when the matrixes can not wrap M7C3 carbides, resulting gradual corrosion of high chromium cast iron. The prediction values have sufficiently mined the basic domain knowledge of corrosion process of high chromium cast iron under phosphoric acid medium. Therefore, a new way of predicting corrosion property according to corrosion conditions was provided by the authors.

Synthesis of Mesoporous Zr-P-Al Materials with High BET Specific Surface Area without Calcination

2011 ◽  
Vol 287-290 ◽  
pp. 2094-2101
Author(s):  
Zi Yu Liu ◽  
Yue Qi ◽  
Ying Xu Wei ◽  
Zong Bin Wu ◽  
Zhong Min Liu
Keyword(s):  
Phosphoric Acid ◽  
Specific Surface ◽  
Surface Area ◽  
Long Range ◽  
Specific Surface Area ◽  
Acid Concentration ◽  
Long Range Order ◽  
Bet Specific Surface Area ◽  
Textual Data ◽  
Phosphoric Acid Concentration

A mesostructured zirconium oxide was synthesized hydrothermally using cetyltrimethylammonium bromide (CTAB) as the structure-directing agent and ZrSO4. 4H2O as the reactant. Subsequent post-synthetic treatment with H3PO4followed by the treatment with AlCl3solutions resulted in mesoporous Zr-P-Al materials, which exhibited high BET specific surface area before calcination. The phosphoric acid concentrationaffected the textual data of the resulting Zr-P and Zr-P-Al materials greatly. 0.1-0.5 M H3PO4increased obviously the long-range order of the as-synthesized Zr-P materials while 0.76 M H3PO4decreased it. After calcination at 773 K, the Zr-P materials turned to nonporous materials except the one synthesized by 0.5 M H3PO4, which showed micropores with a BET specific surface area of 147 m2/g. Further treating the Zr-P materials (synthesized from different concentration of phosphoric acid) with the same amount of AlCl3solution resulted in mesoporous Zr-P-Al materials, but the long-range order of which decreased when the H3PO4concentration increased. Similarly, the BET specific surface area of the above-mentioned Zr-P-Al materials decreased from 462 m2/g for 0.25 M H3PO4to 394 m2/g for 0.5 M H3PO4and finally to 332 m2/g for 0.76 M H3PO4after calcination at 773 K, while the pore size increased gradually from 3.0 to 3.5 nm. It was found that about 90% of the CTAB had been removed during the AlCl3treatment and that the as-synthesized Zr-P-Al materials exhibited high BET specific surface area as well as mesopores. The AlCl3amount is another factor affecting the textual data of the uncalcined Zr-P-Al materials besides the H3PO4concentration. With the phosphoric acid concentration of 0.25 M, the BET specific surface area of the as-synthesized Zr-P-Al materials increased from 477 m2/g to as high as 734 m2/g with the increasing AlCl3amount before it decreased from then on.

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