Sprayed product moisture content

Product moisture content during spraying (dependent variable) Atomizing air volume/pressure Batch size Outlet filter shake (pulse) interval/time... 

In the Swift process (Figure 12.14), phosphoric acid (50% P2O5) and liquid ammonia react in a two-fluid nozzle, which discharges into a reactor pipe. The mixture of finely divided MAP and steam is injected into a cooling tower where a countercurrent airstream carries away the water vapor formed by the heat of reaction and cools the product, The product moisture content is 3%-5%. The Nissan process is also a spray tower process, in which droplets of phosphoric acid react with ammonia in an ascending airstream. 

Pan and cascade burners are generally more limited ia flexibiHty and are useful only where low sulfur dioxide concentrations are desired. Gases from sulfur burners also contain small amounts of sulfur trioxide, hence the moisture content of the air used can be important ia achieving a corrosion-free operation. Continuous operation at temperatures above the condensation poiat of the product gases is advisable where exposure to steel (qv) surfaces is iavolved. Pressure atomiziag-spray burners, which are particularly suitable when high capacities are needed, are offered by the designers of sulfuric acid plants. 

Figure 2.13 Influence of moisture content on the temperature of powder in a spray dryer (tp), dryer outlet temperature (f0) and sticking temperature (rs). The minimum product tempera-tured required to avoid problems with sticking is at TPC with the corresponding dryer outlet temperature TOC. (Modified from Hynd, 1980.)...

Table VI. Moisture Content of Spray Dried Products...

Spray dried products, in general, are expected to meet a number of requirements. Properties of interest include size and size distributions, bulk density, moisture content, friability, appearance, reactivity and, with food products, aroma and flavour. Control of these properties requires close attention to all four unit processes described in Section 1.1. 

Sulfur mustard can be very persistent in soil (Rosenblatt et al., 1995). Persistence depends on the soil type, pH, moisture content, and whether the agent is at the soil surface or buried. Small (1984) reported that when HD was applied to the soil surface, volatilization would be the main route of HD loss (half-life about 30 min), but if the soil was wet, hydrolysis would be the main loss pathway. When sprayed onto soil, a vesicant action was still apparent after about 2 weeks when the agent leaked into the soil, however, a vesicant action was still present after 3 years (DA, 1974). Rosenblatt et al. (1995) state that the persistence of sulfur mustard in soil is due to the formation of oligomeric degradation products that coat the surface of the mustard agent and that are resistant to hydrolysis. 

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