Chlorides process fluids

Chloride Process. A flow diagram for the chloride process is shown in Figure 1. The first stage in the process, carbothermal chlorination of the ore to produce titanium tetrachloride, is carried out in a fluid-bed chlorinator at ca 950°C. If mineral rutile is used as the feedstock, the dominant reaction is chlorination of titanium dioxide. 

In addition to the potential for SCC from the inside as a result of the process fluids, austenitic SS s can experience SCC from the outside, if the austenitic SS is neither low carbon nor stabilized, intergranular SCC can occur as low as at room temperature as a result of either chlorides or sulfur dioxide in the atmosphere. In the 140 to 220°F (60 to 104°C) range, transgranular SCC of stabilized, low carbon, and regular grades of austenitic SS s has occurred as a result of chlorides from seacoast atmospheres. 

The best bioelectric interfaces are combinations of metals and their metallic salts, usually chlorides. The metal salt is used as a coating on the base metal and acts as an intermediary in the electrode-electrolyte processes. Silver in combination with a chloride coating is the most widely used biopotential recording electrode. Silver chemically reacts in chloride-bearing fluids such as saline, skin sweat, and body fluids containing potassium and sodium chloride. After a few hours of immersion, a silver electrode will become coated with a thin layer of silver chlorides. This occurs by the spontaneous reaction ... 

Process fluids may be used for hydrostatic testing in some special cases, but water is the almost universal choice. The quality of the water is an important consideration. Residues from hydrostatic testing often lead to corrosion. Chloride ions in the water are frequently a problem in apparatus or piping that is vulnerable to stress corrosion. Scrupulous removal of test water may be important for this reason or may be necessary because of interactions of water or rusted surfaces with process fluids. 

Industrial manufacturers use replacement reactions to remove dissolved mineral ions from process water. A number of dissolved minerals can be found in process fluids for example, a compound commonly found in process water is calcium chloride. Calcium chloride (CaCl2) forms positive calcium (Ca ) ions and negative chloride (Cl2 ) ions when it is dissolved in water. 

Ions migrate from areas of high to low concentration by diffusion. As ions move into the porous junction of the reference electrode, they establish a voltage known as the "liquid junction potential" or "diffusion potential" (Eg). The more mobile ions accumulate in the junction faster and build up an excess charge that slows down the further accumulation of these ions. The potential Eg and consequently the pH reading shifts until an equilibrium is reached. The potential 5 for the standard KCl reference electrolyte is relatively small because the potassium (K ) and chloride (Cr) ions electrolyte have about the same mobility, which means they accumulate in the junction at about the same rate. However, a KCl electrolyte is not normally used in process fluids with compounds such as... 

AletabolicFunctions. The chlorides are essential in the homeostatic processes maintaining fluid volume, osmotic pressure, and acid—base equihbria (11). Most chloride is present in body fluids a Htde is in bone salts. Chloride is the principal anion accompanying Na" in the extracellular fluid. Less than 15 wt % of the CF is associated with K" in the intracellular fluid. Chloride passively and freely diffuses between intra- and extracellular fluids through the cell membrane. If chloride diffuses freely, but most CF remains in the extracellular fluid, it follows that there is some restriction on the diffusion of phosphate. As of this writing (ca 1994), the nature of this restriction has not been conclusively estabUshed. There may be a transport device (60), or cell membranes may not be very permeable to phosphate ions minimising the loss of HPO from intracellular fluid (61). 

In one modification of this procedure, the starting material is pyroly2ed rice hulls in place of more conventional forms of sihcon dioxide (31). Another unique process involves chlorination of a combination of SiC and Si02 with carbon in a fluid-bed reactor (32). The advantages of this process are that it is less energy-intensive and substantially free of lower sihcon chlorides. 

Trichlorosilane. The primary production process for trichlorosilane is the direct reaction of hydrogen chloride gas and sihcon metal in a fluid-bed reactor. Although this process produces both trichlorosilane and sihcon tetrachloride, production of the latter can be minimi2ed by proper control of the reaction temperature (22). A significant amount of trichlorosilane is also produced by thermal rearrangement of sihcon tetrachloride in the presence of hydrogen gas and sihcon. 

Manufacture. Titanium chloride is manufactured by the chlorination of titanium compounds (1,134—138). The feedstocks usually used are mineral or synthetic mtile, beneficiated ilmenite, and leucoxenes. Because these are all oxygen-containing, it is necessary to add carbon as well as coke from either coal or fuel oil during chlorination to act as a reducing agent. The reaction is normally carried out as a continuous process in a fluid-bed reactor (139). The bed consists of a mixture of the feedstock and coke. These are fluidized by a stream of chlorine iatroduced at the base (see Fluidization). The amount of heat generated in the chlorination process depends on the relative proportions of CO2 or CO that are formed (eqs. 1 and 2), and the mechanism that... 

Extraction from Aqueous Solutions Critical Fluid Technologies, Inc. has developed a continuous countercurrent extraction process based on a 0.5-oy 10-m column to extract residual organic solvents such as trichloroethylene, methylene chloride, benzene, and chloroform from industrial wastewater streams. Typical solvents include supercritical CO9 and near-critical propane. The economics of these processes are largely driven by the hydrophihcity of the product, which has a large influence on the distribution coefficient. For example, at 16°C, the partition coefficient between liquid CO9 and water is 0.4 for methanol, 1.8 for /i-butanol, and 31 for /i-heptanol. 

---