China 
Africa 
Explore chapters and articles related to this topic
Ammonia Synthesis
Published in Martyn V. Twigg, Catalyst Handbook, 2018
The cyanamide route to ammonia is shown in equations (1), (2) and (3). Calcium carbide (CaC2), obtained by fusion of lime and carbon, reacts at 1000°C with nitrogen to form calcium cyanamide (CaCN2). Hydrolysis of the cyanamide yields ammonia, with simultaneous precipitation of calcium carbonate. The first plant was commissioned in Italy in 1906, and other plants using the process were built in Germany and the USA. Somewhat surprisingly, in Germany production by the cyanamide route had reached 140 000 tonnes per year by 1915. However, the process was inefficient in its use of energy, and required 230 GJ tonne−1of nitrogen, but such was the need for explosives that this extreme cost was apparently justified.
Influence of thiourea synthesis with silica fume on the corrosion rate of reinforcement concrete
Published in Geosystem Engineering, 2020
Taher A. Tawfik, Magdy A. El-Yamani, A. Serag Faried, Shimaa M. Mohammed, Gh.M. AbdEl-Hafez
On the other hand, thiourea is formed due to the reaction of calcium cyanamide with hydrogen sulphide in the existence of carbon dioxide. Thus, as thiourea (calcium cyanamide) and C-S-H rise, concrete compressive strength rises until the thiourea value attains 3%. It is recognized that when the thiourea value grows more than 3% the quantity of sulphide rises that reacts with C-H in the existence of water and create gypsum. Therefore, concrete compressive strength falls off as a result of forming and growing size of gypsum (Mertschenk, Beck, & Bauer, 2002). Thus, the previous explained reaction mechanism for the influence adding silica fume and thioureas to cement is illustrated in Figure 6). The improvement in compressive strength was found to be 24 and 31.84% for fresh and salty water respectively in comparing control specimens with 10% silica fume accompanied with 3% thiourea .Similar observations was reported by Kankariya et al. (Kankariya, Patil, Bhamre, & Mhasde, 2017), which coincided with the present work that compressive and flexural strength exhibited the highest enhancement with 10% silica fume replacement. Kadri (Kadri & Duval, 1998) also concluded that the usage at 10% replacement level where the range of compressive strength growth between about 10–17% at various water cement ratio (0.25–0.45). Whereas Sakr (Sakr, 2006)stated that at 15% silica fume content barite concrete, gravel concrete, and limonite concrete illustrated increment in compressive strength by 23.07, 23.33 and 23.52% respectively at 7 days, 20, 21.34, and 22.58% respectively at 28 days, 18.7, 16.5, and 22% respectively at 56 days and 7.14, 18, and 22.80% respectively at 90 days.