Salt In, Salt Out

chapter 2 Salt In, Salt Out Following their organizational meeting in November 1917, Yongli’s promoters began work on two Herculean tasks: searching for a plant design while raising the needed capital. In the process, problems of technology transfer, shifting government policy, and limitations of China’s capital market plagued them. Yongli’s challenge of Brunner, Mond’s formidable hold on the “well regulated” market and technology was both risky and difficult, which in turn made the task of raising the necessary capital even more daunting as it battled the Rev- enue Inspectorate over the gabelle waiver. Problems of Technology Transfer As Chen Diaofu and his colleagues demonstrated in Fan Xudong’s backyard, the chemistry behind the Solvay process was a public good. However, the engineering to make it work on an industrial scale was not.1 Sodium chloride (salt), one of the three main raw materials for the process, must be purified as a solution cleared of dirt, magnesium, and other impurities. The other essential chemical, ammonia, could be generated through burning coke, or added in liquid form. Reaction is then carried out by passing the concentrated and purified brine through the first of two absorption towers. Ammonia bubbles up to saturate the brine (NaCl + NH3, Step I). Separately, carbon dioxide is produced by heating limestone in a kiln at 950–1100°C. The calcium carbonate (CaCO3) in the limestone, the third main ingredient, is partially converted to quicklime (calcium oxide, CaO) and carbon dioxide: CaCO 3 → CO 2 + CaO ( Step II) The carbon dioxide and ammoniacal brine are then fed into a second tower for carbonation. As the hot solution reacts with carbon dioxide and cools, sodium bicarbonate (NaHCO3) precipitates out of the ammonium chloride mother liquor and settles into a thick sludge. By calcination (160–230°C), the precipitate 1 Chen Diaofu (1946), 28–38. The process and technical problems as described below is drawn from Hou Te-pang (Hou Debang), Manufacture of Soda (1st ed., New York: The Chemical Cat- alog Co., 1933; 2nd ed., New York: Reinhold Publishing Corp., 1942), passim. © koninklijke brill nv, leiden, ��7 | doi �0.��63/9789004336384_004 <UN> Salt In, Salt Out 27 is then converted to the final product, sodium carbonate (Na2CO3), or soda ash, producing water and carbon dioxide as by-products: 2 NaHCO 3 → Na 2 CO 3 + H 2 O + CO 2 ( Step III) Quicklime left over from heating the limestone is then introduced into the left- over mother liquor to yield free ammonia, water, and calcium chloride: 2 NH 4 Cl + CaO → 2 NH 3 + CaCl 2 + H 2 O ( Step IV) The recovered ammonia could then be fed back to the initial brine solution in step (i), and the carbon dioxide from step (iii) recycled for step (ii). When properly designed and operated, a Solvay plant can reclaim almost all its ammonia. The only major consumable inputs to the Solvay process are salt, limestone and thermal energy. Continuous operation with relatively cheap raw materials and generating less troublesome by-products and environmental damage, the Solvay process rendered obsolete the Leblanc batch process using sulphur and hydrochloric acid.2 As the modern industrial standard, however, a Solvay plant is also expensive to erect and demanding in engineering. The continuous process required moving large volume of gases and liquids with precise calibration of the amount, pressure, and temperature of input and output at each stage, especially during precipitation. The absorption towers and piping must be designed and engineered to specification, air-tight and strong enough to resist corrosion. The final step—decomposing the sodium bicarbonate by heat into soda ash, carbon dioxide, and water might be simple, but it was “one of the most difficult parts of the whole process” because of the tendency of wet sludge to lump, resulting in uneven heat absorption, scaling of the drying pan, and plugged airflow. Any bottleneck or disruption would bring the entire factory to a standstill. Even with Solvay’s license and assistance, Brunner, Mond spent years commissioning its Winnington plant: “Everything that could burst did, and anything that could break did.”3 To protect their trade and share of the market, engineering service and operational parameters were kept as industrial secrets by the 2 On acidic fumes and calcium sulphate waste from the Leblanc process, see John Graham Smith, The Heavy Chemical Industry in France (Oxford: Clarendon Press, 1979), 285–87. Cal- cium chloride, useful for deicing and desiccation today, was then the only “waste” product from the Solvay process. 3 Watts (1923), 27; and Technical Director’s Department, Northwich, “A short history of Brun- ner, Mond & Co.” dated 6 January 1946, 2. <UN>.

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