Precipitators, cold side

Plant description. Two nearly identical 430-Mw(e), western, conventional pulverized-coal-utility boilers (referred to as plants A and D) were tested. Both units use tangentially fired burners and burn low-sulfur 200-mesh coal of heat content approximately 27 000 J/g. Both units are equipped with cold-side electrostatic precipitators (ESP) of design efficiency of 99.5% or greater, and a modern flue-gas desulfurization (FGD) system consisting of four verticle spray towers. 

Table II. Estimates of the concentrations of selected elements in submicrometer-diameter particles collected upstream of a cold-side electrostatic precipitator, ppm.

With the knowledge that the concentration of sulfur trioxide acts as a control on resistivity of fly ash, it is not surprising that precipitators not meeting design requirements made use of SO3 addition to the flue gas. The injection takes place after the air heater, prior to entering the ESP unit for a cold side precipitator. In some cases, improvement in ESP performance was significant. In others, because of the nature of the fly ash, the improvement was marginal. 

The particulate removal device, such as an electrostatic precipitator, can be placed either before the air preheater (a hot-side electrostatic precipitator) or after the air preheater (cold-side electrostatic precipitator). A fabric filter can be used in place of the electrostatic precipitator. Alternatively, or in addition, a flue-gas-desulfurization (FGD) unit treats the hot gas before it is released to the atmosphere. 

To 2 ml. of the ester in a test-tube add slightly more than the same volume of a cold saturated aqueous copper acetate solution. The blue colour of the latter turns immediately to a pale green. Now shake the tube vigorously in order to produce an emulsion of the ester in the aqueous layer. Scratch the sides of the tube with a rod, and shake vigorously as before. Crystallisation may be delayed for about 5 minutes, but, when once started, rapidly gives a copious precipitate... 

Aliphatic mono-halides, and aromatic hydrocarbons with halogen in side-chain, precipitate silver hdide on treatment with cold aqueous silver nitrate solution. 

In the North American market, water heaters are almost always made with the cold water inlet and hot water outlet lines coming out of the top of the tank. The hot water outlet opens right into the top of the tank and so draws off the hottest water. The hot water has risen to the top of the tank because of its lower density. The cold water on the inlet side is directed to the bottom of the tank by a plastic dip-tube. In some models the dip-tube is curved or bent at the end to increase the turbulence at the bottom of the tank. This is to keep any sediment from settling on the bottom of the tank. As sediment— usually calcium carbonate or lime—precipitated out of the water by the increased temperature builds up, it will increase the thermal stress on the bottom of a gas-fired water heater and increase the likelihood of tank failure. On electric water heaters the sediment builds up on the surface of the elements, especially if the elements are high-density elements. Low-density elements spread the same amount of power over a larger surface of the element so the temperatures are not as high and lime doesn t build up as quickly. If the lower elements get completely buried in the sediment, the element will likely overheat and burn out. 

In this method, first established by Herz and later studied by Hale, hexamine is introduced into fuming nitric acid which has been freed from nitrous acid. The reaction is conducted at 20-30 °C and on completion the reaction mixture is drowned in cold water and the RDX precipitates. The process is, however, very inefficient with some of the methylene and nitrogen groups of the hexamine not used in the formation of RDX. The process of nitrolysis is complex with formaldehyde and some other fragments formed during the reaction undergoing oxidation in the presence of nitric acid. These side-reactions mean that up to eight times the theoretical amount of nitric acid is needed for optimum yields to be attained. 

Hexammino-iridium Chloride, [Ir(NH3)e]Cl3, is prepared by heating chloro-pentammino-iridium chloride, [Ir(NH3)5Cl]CI2, with 25 per cent, aqueous ammonia in a sealed tube to 140° C. The crude product so obtained is evaporated with hydrochloric acid, the residue dissolved in water, and precipitated by means of sodium pyrophosphate. From this the nitrate is formed by treating with dilute hydrochloric and nitric acids, and finally the nitrate is decomposed by repeated evaporation to dryness with concentrated hydrochloric acid. The residue is then treated with ice-cold hydrochloric acid, when the chloride is precipitated. It crystallises in large six-sided colourless prisms belonging to the monoclinic system, and is soluble in water.1... 

To do this, the paper first explained the operation of existing particulate control devices, notably the electrostatic precipitator (ESP). It described how particulate capturability can be improved by chemical treatment and then illustrated how proprietary formulation has led to the treatment of a wide variety of fuels in both cold and hot side ESP units. Evidence was also presented showing fine particulate emissions, i.e., those implicated in health effects, could be significantly reduced. A description was made of the specific marketing problems that had to be solved when a chemical company sought to develop an industrial market where the customer has little or no chemical capability. 

The neutral zinc complexes described in Figure 9.5 are proving to be quite remarkable compounds. Their preparation is simple and the synthetic yields are high (typically 70-90%). When one looks at the crude product, few if any side products are seen. Mechanical losses probably account for the less than perfect isolated yields obtained. The neutral metal complexes are typically freely soluble in various organic solvents (e.g., toluene, CH2CI2, CHClj, THF, dioxane, and acetonitrile) and partially soluble in methanol. They are generally insoluble in hexanes, diethyl ether or cold methanol, and these latter organic solvents can be used to precipitate the... 

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