Effluent recycle

Liquid Effluents. Recycling of acid, soda, and zinc have long been necessary economically, and the acid—soda reaction product, sodium sulfate, is extracted and sold into other sectors of the chemical industry. Acid recovery usually involves the degassing, filtering, and evaporative concentration of the spent acid leaving the spinning machines. Excess sodium sulfate is removed by crystallization and then dehydrated before sale. Traces of zinc that escape recovery are removable from the main Hquid effluent stream to the extent that practically all the zinc can now be retained in the process. 

Low concentrations of oil can be removed by dissolved air flotation (DAF). In this process, an effluent recycle is pressurized in the presence of excess air, causing additional air to go into solution, in accordance with Henry s Law. When this water is discharged to the inlet chamber of the flotation unit at close to atmospheric pressure, the dissolved air comes out of solution in the form of tiny air bubbles which attach themselves to and become enmeshed in suspended solids and oil globules. The primary design criteria is the air/solids ratio, which is defined as the mass of air released divided by the mass of solids fed. Sufficient air must be released to capture the solids in the influent wastewater. The performance of DAF for the treatment of several... 

In a steam stripper, steam is introduced into a packed tower, which causes volatiles to be removed in the vapor phase. An a2eotropic mixture is formed, resulting in a separation of the volatiles from the water. An effluent recycle is usually employed to reduce volatiles in the Hquid effluent. 

Reformer charge Reformer effluent Hydrocracker charge effluent Recycle gas... 

There are three common flotation system configurations (a) full-flow pressurization (b) partial flow pressurization without effluent recycle and (c) recycle flow pressurization, which have been graphically illustrated in Figures 27.8 through 27.10, respectively. 

Stillian, J., Barreto, V., Friedman, K., Rabin, S. and Toofan, M. Ion Chromatography System Using Electrochemical Suppression and Detection Effluent Recycle, US Patent 5,352,360, 1994. 

Anonymous. Effluent recycling plant expands to provide boiler feedwater to Chevron refinery. Civil Eng. 2000, 70(7), 14. 

Figure 3.10 Closed-loop response for a 15% increase in production rate and 1.5% decrease of the product-purity setpoint. Process flow rates in the nominal case with no modeling errors (a) product flow rate and (b) reactor effluent, recycle, and column boilup flow rates.

Inspecting Equation (5.29), we notice that three of the state variables (namely, Mr, My, and Ml) are material holdups, which act as integrators and render the system open-loop unstable. Our initial focus will therefore be a pseudo-open loop analysis consisting of simulating the model in Equation (5.29) after the holdup of the reactor, and the vapor and liquid holdup in the condenser, have been stabilized. This task is accomplished by defining the reactor effluent, recycle, and liquid-product flow rates as functions of Mr, My, and Ml via appropriate control laws (specifically, via the proportional controllers (5.42) and (5.48), as discussed later in this section). With this primary control structure in place, we carried out a simulation using initial conditions that were slightly perturbed from the steady-state values in Table 5.1. 

For a plug flow reactor with effluent recycle, Fu et al. (1971) derived the residence time distribution ... 

Mobil Solvent No. Hydrogenated SRC I Recycle (92-26-019) Effluent Recycle (92-03-035)... 

SOLVENT 1 SRC-1 PREHEATER EFFLUENT RECYCLE 92-03-35 HYDROGENATED SRC-1 RECYCLE (CONOCO) -.92-26-019... 

The systems using the larger packing are used in the treatment of relatively strong, low-suspended-solids industrial waste. These systems are closed columns usually run in an upflow mode with a gas space at the top. These are operated under anaerobic conditions with waste conversion to methane and carbon dioxide as the goal. Effluent recycle is often used to help maintain the pH in the inlet zone in the correct range 6.5-7.5 for the methane bacteria. Some wastes require the addition of alkaline material to prevent a pH drop. Sodium bicarbonate is often recommended for pH control because it is easier to handle than lime or sodium hydroxide, and because an overdose of bicarbonate will only raise the pH modestly. An overdose of lime or sodium hydroxide can easily raise the pH above 8.0. Table 22-48 gives... 

We denote by Vr the volume of regenerant effluent recycled from one cation exchange cycle, and by Vea the volume of acid necessary for regeneration if it were used at the same concentration as in the production of ammonium nitrate or ammonium sulfate (55% for nitric acid and 98% for sulfuric acid). The acid is actually diluted twice, firstly when the regenerant solution is prepared and secondly in the resin bed by longitudinal diffusion wbich broadens the concentration profile at the front and tail. 

Recycle Percentage This applies to a flotation unit operating with effluent recycle. The recycle percentage is the percentage of the influent flow that is recycled. 

Transition metal oxidants such as manganese and chromium oxidants have been widely used in the chemical industry over the years. They have a major disadvantage in that they produce large volumes of effluent containing the transition metals which are subject to more and more strenuous controls on discharge levels. Supported reagents or effluent recycle could be considered but neither is easy on an industrial scale and they are cures rather than prevention of the problem. 

As has been demonstrated in this paper in the high Peclet number limit, continuous effluent recycle with shift allows binary separation of solutes to arbitrarily high purities with essentially complete recovery of products. In addition, products can be recovered at or above their feed concentrations and, because the electric field can be significantly reduced when solutes are repeatedly cycled through the chamber, the transverse thickness of the chamber can be increased proportionately. 

In step 3 approximately one bed volume of recycle eluate displaces the solution remaining in the bed into the feed tank, for recovery of any uranium that may have started to appear in the effluent. Recycle eluate contains approximately 30 g NOs "/liter and 25 g free acid/hter, expressed as H2SO4, and a low concentration of UsOg. 

M. Paleologou, R.M. Berry, R. Thompson, and J.T. Wearing, Electromembrane process for the treatment of Kraft mill electrostatic precipitator catch, US Pat. 5,567, 293 H.-J. Rapp and P.H. Pfromm, Electrodialysis for chloride removal from the chemical recovery cycle of a Kraft pulp mill, J. Membr. Sci., 1998, 146, 247-261 P.H. Pfromm, S.-P. Tsai and M.P. Henry, Electrodialysis for bleach effluent recycling in Kraft pulp reduction Simultaneous control of chloride and other no-process elements, Can. J. Chem. Eng., 1999, 77, 1231-1238. 

When the cost of the equipment for separation of the reactor effluent, recycle, and purification of the products is of a higher order of magnitude than for the reactor itself. 

Most PTC reactions are carried out on an industrial scale in the batch mode in mixer-settler arrangements. In view of the reactor design in the liquid-solid-liquid PT-catalyzed reaction, Ragaini and coworkers [147-149] reported the use of fixed-bed reactors with a recycling pump or with a recycling pump and an ultrasonic mixer, and emphasized the importance of effluent recycle concept. Schlunt and Chau [150] reported the use of a cyclic slurry reactor, which allowed the immiscible reactants to contact the catalyst sites in controlled sequential steps. However, for triphase reactions in liquid-liquid systems where... 

Most bioreactor effluent recycled without treatment No clarifer. Remaining effluent processed through brine concentrator and evaporatOT/crystalUzer. 

Digestion With Product Qas and Posttreated Effluent Recycling... 

S. Judd, B. Jefferson, Industrial effluent recycling in the power indiastry, Ultrapure Water 21 (4) (2004) 37-42. 

Recycle Pressurization. The rectangular unit in Fig. 4.75 illustrates the use of recycle pressurization. Air is injected into the effluent recycle stream before it discharges into the inlet compartment of the flotation unit. There it is mixed with the incoming raw waste and releases the required air for flotation. The amount of effluent recycled varies from 25 to 50 percent of the forward flow. This approach has advantages when the raw waste is highly variable in composition or contains large amounts of solids. 

Makeup washwater for hydrotreater effluent recycle wash-water to remove ammonia sulfide salts that plug downstream condensers and heat exchangers... 

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