Candle filtration

Once filling is complete, filtration begins [Fig. 22.3(b)]. Treated brine is pumped into the vessel at the desired flow rate through an automatic control valve. The flow of brine is from the outside to inside of the filter candles. Filtrate clarity is achieved immediately no recycling of flow is required. As the filtration proceeds at constant flow, solids accumulate as a filter cake on the outside surface of the filter socks. While... 

Air exhausted from the oven carries with it significant quantities of vapour (plasticizer, solvent, and products of oxidative decomposition) nowadays most ovens are fitted with some form of equipment to remove or reduce this—such as glass fibre candle filtration systems and electrostatic precipitators (which can remove up to 95% of plasticizer vapour but do not arrest white spirit and... 

Rapagna, S Gallucci, K Di Marcello, M. et al. (2009) In situ catalytic ceramic candle filtration for tar reforming and particulate abatement in a fluidized- bed biomass gasifier. Energy and Fuels, 23, 3804-3809. 

Cylindrica.1 Element Filters. These filters, often referred to as candle filters, have cylindrical elements or sleeves mounted vertically and suspended from a header sheet, which divides the filter vessel into two separate compartments (Fig. 16). The filtration takes place on the outside of the sleeves. The inlet is usually in the bottom section of the vessel and the filtrate oudet in the top section above the header sheet. A less usual design is to locate the filtrate outlet at the bottom of the elements and thus allow the top chamber to be opened for each inspection of the elements during operation. 

The advantage of candle filters is that as the cake grows on the tubular elements the filtration area increases and the thickness of a given volume of cake is therefore less than it would be on a flat element. This is of importance where a thick cake is being formed the rate of increase in the pressure drop is less with tubular elements. 

The purity of oxygen from chlorate candles before and after gas filtration is indicated in Table 2. A particulate filter is always used. Filter chemicals are HopcaUte, which oxidizes CO to CO2 molecular sieves (qv), which remove chlorine compounds and basic materials, eg, soda lime, which removes CO2 and chlorine compounds. Other than H2O and N2, impurity levels of <1 ppm can be attained. Moisture can be reduced by using a desiccant (see Desiccants). Gas purity is a function of candle packaging as well as composition. A hotter burning unit, eg, one in which steel wool is the binder, generates more impurities. 

Preparation of Sodium 1-Methyl-5-Allyl-5-(1-Methyl-2-Pentynyl) Barbiturate A solution of 61 g of 1-methyl-5-allyl-5-(1-methyl-2-pentynyl) barbituric acid in 100 ml of ether was extracted with 465 ml of 2% aqueous sodium hydroxide solution. The aqueous extract was washed with successive 75 ml and 50 ml portions of ether. The pH of the aqueous solution was adjusted to 11.7, using 5% aqueous sodium hydroxide solution. 5 g of decolorizing carbon were added to the solution with stirring the mixture was permitted to stand for 20 minutes at room temperature, and the carbon was removed by filtration. A solution containing 4 g of sodium carbonate in 25 ml of water was added to the aqueous solution, and the mixture was filtered sterile through a porcelain filter candle of 02 porosity into sterile bottles. The aqueous solution was then dried from the frozen state, whereupon a sterile residue of sodium 1-methyl-5-allyl-5-(1-methyl-2-pentynyl) barbiturate, weighing about 62 g was obtained. 

Pall Process Filtration Ceramic Candle Filter 1000°C (max.) 99.99% Supported both sides clay bonded silicon carbide filter... 

Lachman s recommendations for wines for the market still stand Wines should never be put on the market unless they are perfectly clear that is, they should hold clear and show brilliant before a candle. His recommendation that wines be aged at least eighteen months before bottling simply reflect the inadequacy of the clarification and filtration procedures of his time. 

Phillips J.N. and Dries H.W.A., Filtration of flyslag from the Shell coal gasification process using porous ceramic candles, in Gas Cleaning at High Temperatures, Clift R. and Seville J.RK., eds.. Chapman Hall, London, (1993), p. 127,... 

The ceramic filter showed good filtration efficiency, with stable pressure drop. However, after more than 1200 hours of trouble free operation suddenly two ceramic candles broke. The difficulty to detect a relatively small failure in a hot gas filter was then noticed in practice even though no serious damage was caused. 

Dry cake discharge can be achieved with a Fundabac candle-type filter manufactured by DrM, Dr. Muller, AG, of Switzerland. This filter uses a candle made up of six small-diameter tubes around a central filtrate delivery tube. This design allows the filter cloth to be flexed outward upon blowback, easily achieving an effective dry cake discharge (Fig. 18-129). 

Tuhtdar Presses As the name implies, this press is composed of a candle filter inside a cyhndrical hydrauhc casing (Fig. 18-192). The filter cloth is wrapped around the filter candle, and a diaphragm is attached to the inner side of the outer casing. During the filtration step, the space in between two cylinders is filled with slurry, and pressure filtration is conducted. At the end of the filtration step, the diaphragm is inflated to squeeze the cake around the filter candle. At the end of expression, the bottom of the hydrauhc casing tube is opened and the filter assembly is lowered. Air is then introduced to pulse the cake off the candle. Alter the cake is discharged, the inner filter candle moves back, and the bottom is closed for the next filtration cycle. 

Membrane processes are used to filter liquids. Instead of conventional filter materials (e.g. filter cloth, filter candles,) microporous membranes are employed with molecular size pores. First the industry had to learn how to manufacture membranes with controlled pore sizes. To optimise the filtration capacities specific filter structures had to be designed in which the liquid followed well defined flow patterns on one side of the membrane. Many different systems were developed for the varied applications, all having their advantages and also disadvantages, i.e. plate modules, tubular modules, spiral wound membranes, etc. Research and development in this field is far from being exhausted. Today membrane systems are available which are sufficiently resistant to chemical, mechanical and thermal stress. They are produced from plastic... 

Candle FilterS Tubular filter elements contained in a matching vessel are known as candle filters. The actual filter vessel may contain one or more filter candles, and may be used as pressure or suction filters for the filtration of liquids and gases. A particular advantage offered is that candles may readily be changed to different types, to suit particular requirements or applications. A typical candle filter is shown in Fig. 11. Materials of candles are selected to fit a particular process. 

The candle filter element can be textile cloth over a supporting tube, sintered metal, ceramic or spaced rings. It can also be used for air or gas filtration. Metallic candles are particully suited for high temperature applications. 

Tiller, F.M., and Wenping Li. 2001. Optimizing candle filters for super-compactible materials. Advances in Filtration and Separation Technology 15. 

Sintered membranes are made on a fairly large scale from ceramic materials, glass, graphite and metal powders such as stainless steel and tungsten.9 The particle size of the powder is the main parameter determining the pore sizes of the final membrane, which can be made in the form of discs, candles, or fine-bore tubes. Sintered membranes are used for the filtration of colloidal solutions and suspensions. This type of membrane is also marginally suitable for gas separation. It is widely used today for the separation of radioactive isotopes, especially uranium. 

---