CEE Jan-Mar 2012

containing limestone, clay, MgO and CaCI 2 (6 - 18 wt %) by burning it to temperatures of 1000 - 1300°C. A variety of industrial waste products, such as fly ash, magnesite dust, steel plant wastes or municipal waste with a significant amount of chlorine-containing materials may also be utilized as raw meal constituents [Pradip and Kapur, 1990]. The overall saving in energy in the production of alinite cements is - 1250kg, amounting to a 30 per cent saving [Locher, 1986]. Some chloride evaporates in the kiln and may give rise to a chloride cycle in the kiln. Alinite phase is stable at a temperature range of 900 - 1150°C and the actual clinkerization is carried out at a temperature range of 1150 - 1200°C with heat consumption of about 535 kcal/kg clinker (2239 kg clinker) [Benstend and Barnes, 1994]. Alinite cement contains lesser amount of GaO and larger amount of Al 2 0 3 and Fe 20 3 than Portland cement. The clinker may also contain limited amounts of belinite, calcium chloride orthosilicate, calcium ferrite (CF), Periclas (MgO), alite (C3S) and 0 -C2S. If the burning temperature is increased to 1370°C and above, some of the alinite formed at lower temperatures converts to alite and at the same time the calcium chloroaluminate content is increased [Tsuchida et al. , 1996]. Alinite is defined as a calcium oxy-chloro– aluminosilicate. Whereas in alite (3CaO.Si0 2 ), the main phase of Portland cement, the Ca 2 + cations are balanced by Si04 4. and 0 2 • anions, the structure of al inite consists of Ca 2 + and Mg 2 + cations balanced by Si04 4 ·, AI0 4 s-, 0 2 • and Cl" anions. Crystallographic studies have revealed that the main feature of 700 ""... - - 4 -- - - ... - - - - ... ...., - - ....... -- .. _ ·--- ---· --- - - - - :Socii Solid w... ' counl•t .oj C I ••• 1 I 500 , ... ~ I l ' p c. Clldlll P-~e ::: l~~L~~~JJ~JlL~~~~~ to zo .so •o so 10 Figure 1. XRD pattern of solid soda waste alinite is the peculiar position of the chlorine atoms su rrounded by eight calcium ions [Noudelman and Gadaev, 1986]. There are many suggested chemical formulas for alinite by different investigators [Gdler, 2000]. Simply, the formula is Ca,,[3(Si04).(AI04) .02.CI ]. In reality alinite may be stable only if some Mg 2 + is also present in the crystalline lattice, substituting for Ca 2+. The proportions of Si04/AI04 in alinite are not constant and may vary between 3.35/0.65 and 3.45/0.55 [Noudelman et al. , 1980]. Thus, the actual composition of alinite may be most accurately expressed by the foll owing formula ; Ca10Mg(1-xl2l x12 [(Si04htx{AI04)1-x 0 2CI] {1) Where 0.35<x<0.45, and refers to a lattice vacancy. Experimental Study Raw materials In this study the main raw materials used for alinite cement are soda solid waste, clay and iron ore in minor amounts. Solid waste obtained as a result of the solvay process, was acquired from Mersin Soda Plant . The soda waste was wet and in agglomerated from when received. There was an option to reduce the chlorine content of the waste from 6 wt% down to I wt%. However, for the case of alinite clinker chlorine is required to form the alinite phase properly. Therefore, the waste with high chlorine content of about 6 wt% was utilized throughout this study. The mineralogical analyses reveal that the soda waste contains both CaC0 3 and Ca(OHh as presented in Figure 1. The results of the raw materials' chemical analysis are presented in Table 1. Chemical analyses of the soda solid waste and other raw materials were conducted by Atomic Absorption Spectroscopy (AAS). Loss on ignition and c1· amounts were detected by wet chemical analyses following the EN 196-2 standard . Raw feed preparation During the preparation of the raw mix, the acquired solid soda waste was first dried and ground leading to a suitable powder form of approximately of 90 m. Then the raw mix is prepared using the recipe provided in Table 2. The raw mix of alinite clinker does not include any natural limestone from quarry, in order to maximize the soda 15