Water chemically bound

The resulting sludge contains less chemically bound water and can be more easily dewatered. 

Fired ceramic spheroids have been described for use as a well proppant [1051], Each spheroid has a core made from raw materials comprising mineral particulates, silicium carbide, and a binder. The mixture includes a mineral with chemically bound water or sulfur, which blows the mixture during firing. Therefore the core has a number of closed air cells. Each spheroid has an outer shell surrounding the core, comprising a metal oxide selected from aluminum oxide and magnesium oxide. The fired ceramic spheroids have a fired density less than 2.2 g/cm. ... 

Chemically bound water, or water of crystallization, is divided into two main categories, bound water and zeolite water. They are distinguished by the effect upon... 

Silica used as a filler for rubbers is silicon dioxide, with particle sizes in the range of 10-40 nm. The silica has a chemically bound water content of 25% with an additional level of 4-6% of adsorbed water. The surface of silica is strongly polar in nature, centring around the hydroxyl groups bound to the surface of the silica particles. In a similar fashion, other chemical groups can be adsorbed onto the filler surface. This adsorption strongly influences silica s behaviour within rubber compounds. The groups found on the surface of silicas are principally siloxanes, silanol and reaction products of the latter with various hydrous oxides. It is possible to modify the surface of the silica to improve its compatibility with a variety of rubbers. 

Concretes made with Portland cement have a specific weight of 140 to 150 Ib/ft (2,242 to 2,400 kg/m ). Concrete absorbs the heat of a fire when chemically bound water is released from a crystalline structure and is reduced to lime. Dense concretes can be formed in place, or pneumatically sprayed to the required thickness using steel reinforcement. The corrosive effect of chlorides on the steel surface in moist saline environments (coastal or other chloride environments) dictates the use of protective primers and topcoat sealers. Major advantages of dense concrete are ... 

Moisture in coal takes three forms (l)free or adherent moisture, essentially surface water (2) physically bound or inherent moisture (thai moisture held by vapor pressure and other physical processes) and (3) chemically bound water (water of hydration or combined" water). The ASTM defines total moisture as a loss in weight in an air atmosphere under rigidly controlled conditions of temperature, time, and air flow. Total moisture represents a measurement of all water not chemically combined. Total moisture is determined by a two-slep procedure, involving air-drying for removal of surface moisture from the gross sample, division and reduction of Ihc gross sample, and determination of residual moisture in the prepared sample. An algebraic calculation is used to obtain the total moisture value. 

The physically bound water in the raw material clay is determined by drying the sample at 105 °C until it has a constant mass. In order to determine the chemically bound water it is necessary to heat the sample to 1100 °C. Remember that between the clay sheets water molecules are bound to the ions of the sheets an ionic dipole bond. In addition some molecules are interconnected by means of H-bridges,... 

All electrical property values are strongly dependent on water content for water, the dielectric constant is approximately 81 and resistivity is about 106 2 cm. The dielectric constant has been used as a measure of moisture in coal (Speight, 1994, and references cited therein). However, it should be noted that the effect is not considered to be additive due to the different electrical properties of physically and chemically bound water. With an increase in moisture content, electrical conductivity and dielectric constant increase, whereas resistivity and dielectric strength decrease. Hence, except for special purposes (e.g., dielectric strength measurements of underground coal blocks), electrical measurements require the meticulous drying of coal prior to experiments. 

The normal free, i. e., not chemically bound water content of bricks in dry rooms (20°C) is in the area of one volume percent, but it can rise up to 4% at a relative humidity of over 90%.395... 

Dehydration. This step is carried out between 670 and 1070 K to drive off the organic residues and chemically bound water, yielding a glassy metal oxide with up to 20%-30% microporosity. 

The tar and liquor plant handles the flushing liquor that circulates between the byproduct plant and the primary cooler. It also processes the wastewater that results from recovery of the coal moisture and chemically bound water in the coal. The flushing liquor flows into tar decanters, where the tar separates from the water and is pumped to storage for later sale. Heavier solid particles separate from the tar and are removed as tar decanter sludge. After withdrawal of a bleed stream that contains ammonia, the aqueous liquor is pumped back to the primary cooler. Following removal of tar particles, the wastewater stream is steam stripped. An alkali, such as sodium hydroxide, is added to decompose ammonia compounds dissolved in the liquor. The ammonia vapor is recovered and combined with the rest of the ammonia recovered from the coke-oven gas. 

Chemically bound water is most reasonably defined as including that present in interlayer spaces, or more firmly bound, but not that present in pores larger than interlayer spaces. As will be seen in Chapter 8, the distinction between interlayer space and micropores is not sharp water adsorbed on surfaces of pores further blurs the definition. From the experimental standpoint, the determination is complicated by the fact that the amount of water retained at a given RH depends on the previous drying history of the sample and on the rate at which water is removed. An approximate estimate is obtained by equilibrating a sample, not previously dried below saturation, with an atmosphere of 11% RH (F12,F13,F14). Saturated aqueous LiCl HjO gives the required RH (partial pressure of water vapour = 2,7 torr at 25°C). To achieve apparent equilibrium in a reasonable time (several days), the sample must be crushed and the system evacuated the salt solution should be stirred, at least intermittently. Young and Hansen (Y5) found the composition of the C-S-H in C3S paste thus... 

As noted earlier, treatment of C3S pastes with methanol leaves some of the latter strongly sorbed. The methanol is only removable on heating at temperatures at which it reacts with the C-S-H, causing carbonaiion. Flowever, the total weight of volatiles retained in a C3S paste that has been soaked in methanol and then pumped for about 1 h with a rotary pump is near to that obtained on equilibration with saturated LiCl H,0 (T14). Methanol treatment can thus be used as a rapid, though approximate, method of determining chemically bound water. Other organic liquids could possibly be used in a similar way. 

As with calcium silicate pastes, the gelatinous nature of the principal reaction product renders any definition of chemically bound water somewhat arbitrary. The three definitions of water content described in Section... 

Water retained after D-drying, known as non-evaporable water, has often been wrongly identified with chemically bound water. It excludes much of the interlayer water in C-S-H, AFm and hydrotalcite-type phases and much of the water contained in the crystal structure of AFt phases. It is often used as a measure of the fraction of the cement that has reacted, but can only be approximate in this respect, because the clinker phases react at different rates and yield products containing different amounts of non-evaporable water. Fully hydrated cement pastes typically contain about 23% of non-evaporable water, referred to the ignited weight. Copeland et al. (C38) determined the non-evaporable water contents of a series of mature cement pastes and carried out regression analyses on the cement composition. For pastes of w/c ratio 0.8 and aged 6.5 years, they obtained the approximate expression ... 

The content of chemically bound water is approximately that retained on equilibration at 11% RH of a sample not previously dried below saturation. For fully hydrated pastes of typical cements, it is about 32%, referred to thel ignited weight (F13,T35). There are no systematic data relating this quantityi to cement composition. The total content of water essential for completei hydration in a saturated paste is defined as that present in such a pastel having the minimum w/c ratio at which complete hydration is possiblel... 

The primary product of dehydration, which is an oxide phase with low content of chemically bound water, is X-ray amorphous as a rule, and under thermal treatment crystallizes with the formation of nanocrystals of complex oxide. If the composition differs from stoichiometry, then the phase of the excess oxide is also precipitated. 

Thermal decomposition phase up to 270 °C - 280 °C. Characterised by heavy discoloration of the material, and the evacuation of the letnaining chemically bounded water, with simultaneous development of gasification. 

GYP5UM is a common mineral. Calcined at around 150 C most of its chemically bound water is driven off to produce FLA5TEK. Mixing dry plaster powder with water reforms gypsum, firstly as a paste then apanding and hardening into a solid. A good preparation should be evenly mixed. 

Oxygen content is an important fuel property. This is a measure for the amount of chemically bound water in the dry fuel. This has an important bearing upon both the process operation and final gas composition. 

The complete removal of free water from gypsum samples without affecting the chemically bound water, or water of hydration, requires special care and complete understanding of the factors affecting the moisture-solid equilibrium. 

Table 5 shows weight loss of different materials by microwave drying after exposure to 98 and 75% RH and 24°C for different lengths of time. The percent combined water was determined for all the cases shown in Table S and was found to be essentially constant for each sample regardless of the weight loss by microwave treatment (Fig. 3). This indicates that complete drying was achieved and that the chemically bound water was not affected by microwave at any level of free water. 

Vicinal water is defined as water the structure of which is modified by proximity to an interface but excluding chemically bound water directly on the surface. In... 

Calcination is further heat-treatment beyond drying. Several processes occur (1) loss of chemically bound water or COj, (2) changes in pore size distribution, (3) active phase generation, (4) surface conditioning, and (S) stabilization of mechanical properties. 

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