INGOLD Leading Process Analytics pH Control Allows Higher Profitability Due to Optimized Use of Raw Material Soda ash is produced on a large scale using the Solvay process. To offset the rising energy and metallurgical coke, focus has turned to tighter control of feedstock consumption. Precise and reliable pH measurement plays a major role in optimization of the reaction process. Success Story The customer Soda ash production Shandong Haihua Group, Weifang, in In the industrial production of soda ash the province of Shandong in North-East (sodium carbonate), the Solvay Pro- China, is the largest soda producer in cess is the one most commonly used Asia with an output of two million tons worldwide. It centers around a large of soda ash per year. The Shandong cylindrical hollow tower. At the bottom, Haihua Group employees nearly 3000 calcium carbonate (limestone) is hea- people. Shandong Haihua Group is ted to release carbon dioxide. At the mainly engaged in the production of top, a concentrated solution (brine) of chemicals based on salt, coal and sodium chloride and ammonia enters petroleum, but is also active in both the tower. As the carbon dioxide bubb- import and export of other products. les up through it, sodium bicarbonate Lime + Ammonium Chloride Calcium Chloride + Ammonium + Water Ca(OH)Ca(OH)2 +2 NH 4CICI CaCI2 +2 NH 3 +2 H 2O pH measurement precipitates. The sodium bicarbonate is Superior product means then converted to sodium carbonate by a longer lifetime heating it, releasing water and carbon The customer first tried a solution dioxide. Meanwhile, the ammonia is re- utilizing a compeditor's probe but this generated from the ammonium chloride did not work satisfactorily because the byproduct by treating it with the lime electrode’s lifetime of less than 10 (calcium hydroxide) left over from car- days this was unacceptable by Mr. bon dioxide generation. Because the Shan Yuelong. Solvay process recycles its ammonia, it consumes only brine and limestone, The measuring system suggested by and has calcium chloride as its only METTLER TOLEDO, and subsequently waste product. successfully installed, was comprised of: Industry applications ■ pH electrode InPro 4250 Sodium carbonate is used in the manu- ■ Housing: InFit 761/WS/70 and facture of glass, pulp and paper, deter- later InTrac 777M/070 gents, and chemicals such as sodium ■ Transmitter: pH 2100/2H silicates and sodium phosphates. It is also used as an alkaline agent in many After understanding the process speci- chemical industries. fics, the solid polymer electrolyte elect- rode InPro 4250 was proposed as it is Meeting the customer needs less subject to diaphragm clogging due Mr. Shan Yuelong, the instrument direc- to direct contact of electrolyte with tor of Shandong Haihua Group needed media through an open junction. This pH Control with InPro 4250 to optimize the production process of would reduce contamination by the soda ash in terms of controlling the solids (Ca(OH)2->Ca CO3) present in use of raw materials. Mr. Shan Yuelong the process medium. Initially, a static complained that large amounts of ab- InFit housing was used to test the sui- rasive granulars, such as sand, resul- tability of the electrode. As the customer ted in a high consumption of elect- still wished to be in a position to clean rodes. Since pH is one of the key para- the electrode frequently at will, it was meters in the step of ammonia regene- necessary to have an expedient means ration (see arrow in the reaction), it of withdrawing the electrode from the was requested to optimize this reaction. ongoing process without stoppage. To avoid downtimes for cleaning, this led pH measurement to subsequent installation of a retrac- The conditions of the process table housing type InTrac 777M. were as follows: Temperature: 90 to 95 °C (194 to 203 °F) Pressure: 1 bar / 14.5 psi pH values: 9 to 11 Batch mode: continuous The current situation was not at all satisfactory. 2 METTLER TOLEDO Success Story METTLER TOLEDO solution Broader implementation planned leads to monetary benefit Due to the success of the initial instal- The transmitter transferred the pH signal lation, up until now a total of seven from the very dependable and robust measurement points have been put electrode to the Process Control System into operation by this customer. It is which allowed control of the input of planned to go ahead with further raw materials. Compared to before, sa- installations within the Haihua Group vings were considerable. According to in the near future. Mr. Shan Yuelong, the company saved about US$ 5,700 per year on each loop, and required 3 % less raw ma- terial (about 450 US$)! Moreover, the quality of the byproducts of the reaction also improved. NH3 and Ca(OH)2 included in the waste was substantially reduced. METTLER TOLEDO – the supplier of choice On asking the customer why our com- pany was selected, Mr. Shan Yuelong stated that he had received very profes- sional support, and finally a solution that met his companies needs. He also pH Control with InPro 4250 mentioned the effort and attitudes, and last but not least the open-minded communication of the sales represen- tative, Derek Wang, and his colleagues. This had all been very convincing and was the reason for the confidence established. www.mt.com/pro Mettler-Toledo AG Visit for more information Process Analytics Im Hackacker 15 CH-8902 Urdorf Switzerland – 07 / 06.