Spray-drying powders production

Urea and melamine adhesives represent products of very mature and overaged technologies. Essentially, they are simple reaction products of urea or melamine with formaldehyde they may be Hquids or powders. Liquids are converted to dry powders by "spray drying." Melamine-urea combinations generally are spray-dried powders of co-reacted Hquid melamine and area-formaldehyde resias. 

The introduction of concentrated laundry detergent powders in Japan during 1986-1987 produced a substantial increase in the consumption of LAB in the subsequent 3-4 years as the market changed from low-density, spray-dried powders to the concentrated (compact) products. In these products, which may contain up to 40% surfactant, the cost/performance advantages of LAS are of significance. In addition, LAB sulfonic acid is well suited for the production of high-active, high-density (about 1.0 g/cm3) laundry powders by routes other... 

Fine particle powders can be produced by various methods, such as micronization or spray drying. The physicochemical nature of these fine particles largely defines the stability of the bnlk powder, which in turn is critical to the long-term effective performance of the dry powder product. The section Fine Particles and the Solid State in this article is an introduction to understanding better the fundamental properties that underlie the behavior of bulk powders. Commentary on the various means of producing fine powders follows in the section Powder Production Formulation and Processing. ... 

Controlled optimal particle size and size distribution ensures superior flow properties of coprocessed excipients and reduced reliance on addition of glidants. The volumetric flow properties of SMCC were studied in comparison with those of the physical mixture of its parent excipients (42). The particle size range of the two test samples was found to be similar, but the flow of coprocessed excipient was better than that of the physical mixture. A comparison of the flow properties of Cellactose with its parent excipients was also performed (5) by measuring the angle of repose and Hausner ratio, and Cellactose was found to have better flow characteristics than lactose or a physical mixture of cellulose and lactose. The spray-dried coprocessed product had a spherical shape and even surfaces, which resulted in improved flow properties. On similar terms, mechanically coating the 2% CSD over microfine cellulose powder resulted in improving its flow properties (43). 

Orange terpenes were emulsified in various carrier s and spray-dried. The spray-dried powders were aged for 3 days at 80 C in a draft oven. Beta-pinene is an oxidation product in orange terpenes which can be measured by GC. The beta-pinene level is proportional to the degree of oxidation of the orange terpenes. High levels of beta-pinene content in the spray-dried powders indicate poor oxidation resistance imparted to the encapsulated terpenes by the carrier. 

Instantized milk powder normally exhibits low bulk density but higher water dispersibility than conventionally spray-dried powder. However, the extra heat exposure from the agglomeration and redrying treatments causes additional Maillard reaction, whey protein denaturation, and related chemical and physicochemical reactions that tend to lower product quality. 

Spray drying has become increasingly important in recent years as an alternative to wet scrubbing for sulfur dioxide control. In the spray dryer the sulfur-containing flue gas is contacted with a fine mist of an aqueous solution or a slurry of an alkali (typically Ca(0H)2 or soda ash). The sulfur dioxide is then absorbed in the water droplets and neutralized by the alkali. Simultaneously, the thermal energy of the gas evaporates the water in the droplets to produce a dry powdered product. After leaving the spray dryer the dry products, including the fly ash, are removed with collection equipment such as fabric filters or electrostatic precipitators. 

Spray-dried powders are formulated to give the best overall cleaning performance and flow characteristics at the lowest possible formulation costs. Typical spray-dried detergent formulations are shown in Table 36.6. Slurry preparation is considered to be the single most important factor in spray drying. Control of the raw material order of addition, slurry solids level, slurry temperature, viscosity, and aeration enable manufacturers to deliver the desired final product characteristics. The spray tower itself is simply a contained heat source that removes moisture at a uniform rate dependent upon the quality and the quantity of feed to the dryer. If feed variables are not controlled, variability in the... 

Milk powder (from both skim milk and whole milk) is the other form of milk solids used in confectionery. Skim milk was originally roller dried, but this process has now almost passed out of use and modern milk powders are made by spray drying. This does less damage to the proteins than the older roller process such that the bioavailability of the proteins in spray dried powder is higher than in the roller dried form. In confectionery-making this is not a particular advantage since confectionery products do not (or should not) form a major part of the diet. 

Although excipients are the non-active ingredients, they are indispensable for the successful production of acceptable solid dosage forms. The important roles played by excipients in tablets and capsules, freeze-dried, and spray-dried powders, as well as powder aerosol formulations, were discussed. Some recent applications of excipients in controlled, release formulations for biologicals were also highlighted. Finally, incompatibility problems attributable to excipients were considered with an emphasis on the indirect role of excipients through moisture distribution. 

Copovidone is a product of pharmaceutical purity. It is a white or yellowish-white spray-dried powder that has a relatively fine particle size and good flow properties. It has a typical slight odour and a faint taste in aqueous solutions. 

Use countercurrent spray drying for products which are not heat-sensitive, but may require some degree of heat treatment to obtain a special characteristic, i.e., porosity or bulk density. In this case the final powder temperature may be higher than the dryer outlet temperature. 

The above information is all that is required to perform a preliminary sizing on a spray dryer. The temperature limit of the product is given at 170°F. Using 160 F as the outlet temperature of the dryer should allow us the safety necessary so as not to exceed the temperature limit of the dry powder (product). The fact that we get evaporative cooling while drying the spherically shaped droplets to a similarly shaped powder allows us to use an inlet temperature of about 320°F. Thus the temperature difference (AT) is 160°F. This is the primary driving force in motivating the water to leave the product due to the enormous difference in saturation equilibrium between the wet droplet/dry powder and the very hot dry air. 

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