Multieffect evaporator

The separation of acrylonitrile involves a large amount of water. This is obtained as bottom stream of the distillation columns, with heavy impurities and traces of HCN, ACN and AN. Before reuse, the wastewater is cleaned by multieffect evaporation. The concentrated residual in organics is burned. The water amount produced by reaction is sent to advanced purification in a biological unit. 

A second example is provided by a semiempirical correlation for multi-component activity coefficients in aqueous electrolyte solutions shown in Fig. 2. This correlation, developed by Fritz Meissner at MIT [3], presents a method for scale-up activity-coefficient data for single-salt solutions, which are plentiful, are used to predict activity coefficients for multisalt solutions for which experimental data are rare. The scale-up is guided by an extended Debye-Hilckel theory, but essentially it is based on enlightened empiricism. Meissner s method provides useful estimates of thermodynamic properties needed for process design of multieffect evaporators to produce salts from multicomponent brines. It will be many years before sophisticated statistical mechanical techniques can perform a similar scale-up calculation. Until then, correlations such as Meissner s will be required in a conventional industry that produces vast amounts of inexpensive commodity chemicals. 

A space large enough for an employee to enter and work with restricted activities or movement may have a hazardous atmosphere. The incident occurs because of failure of recognizing the hazards associated with confined spaces. The different kinds of confined spaces for a worker in a plant are tanks, silos, storage bins, vessels, hoppers, pits, and sewer lines. Big fermenters, multieffective evaporators, boilers, and wells are also included in this list. 

A somewhat different furfural stream is obtained when the total waste water of a sulfite plant is submitted to thickening by a multieffect evaporator. In this case, the vapor... 

In the case of diaphragm cells, the cell liquor (10-12 wt% sodium hydroxide and 16-18 wt% unreacted sodium chloride) is concentrated in multieffect evaporators to 50% NaOH. The sodium chloride then is salted out and must be removed, only 1-1.5 wt% remain in the solution. Depending on customers requirements further purification steps will follow, for example, adsorption of salt, chlorate, and carbonate by liquid ammonia or removal of metal impurities by cathodic deposition [18]-... 

Multieffect evaporization This is a classical engineering technique in which a solvent is removed by successive evaporation steps. The solvent removed from the first step is used to heat the liquid which is again fed to the... 

The glycol plant feed, along with any high-aldehyde EO bleeds from the EO purification section, are sent to the glycol reactor (12). A multieffect evaporator train (13, 14, 15) is used to remove the bulk of the water from the glycols. The glycols are then dried (16) and sent to the glycol distillation train (17, 18, 19) where the MEG, DEG and TEG products are recovered and purified. 

Optimal number of stages in a multieffect evaporation system, for which the capital cost is balanced against the cost of heating steam. 

Multieffect evaporator [5]. In an evaporation process, the fluid is heated to its saturation temperature, and then additional energy is applied to start the liquid evaporation. Evaporation occurs at constant temperature and requires a large amount of energy so that the molecules in the liquid state pass to the vapor state. Unlike dryers, what is achieved in the evaporator is concentration, where normally a diluted "juice" with 5-10 % solids is concentrated to 30-50 % solids. Indeed, evaporation is a concentration process and not a dehydration process. Tomato juice will be concentrated in a three-stage multieffect evaporator (Fig. 7.46). 1,000 kg/h of tomato juice are fed to the system with an initial concentration of 6 % solids (w/w). The object of the operation is to obtain a commercial concentrate of 31 % solids (w/w). The outlet solid concentration of stages 1-3 are 13, 21, and 31 % (w/w), respectively, (a) How much water was removed in each stage of the system (b) What is the flow rate of the concentrate at the outlet in kg/h ... 

Multieffect evaporator [5]. In order to design an industrial process to evaporate much of the water present in the product X4, an experiment was conducted in a laboratory-scale evaporator (simple) as shown in Fig. 7.53 ... 

An increased number of effects is now economical for multieffect evaporators. Each evaporator system design will be analyzed more closely to define the nrast economical number of effects. 

All commercial production of PG is by noncatalytic hydrolysis of PO carried out under high pressure and high temperature. A large excess of water is used in the conversion of PO into a mixture of mono-, di-, and tripropylene glycols. Typical product distribution is 90% PG and 10% coproducts. Hydration reactor conditions are 120-190°C at pressures up to 2170 kPA. After the hydration reaction is completed, excess water is removed in multieffect evaporators and drying towers, and the glycols are purified by high vacuum distillation. 

The pure organic chemical produced in the greatest quantity per year is sucrose sugar. The process of converting raw sugarcane or beets into uniform-size sucrose crystals involves extraction, heat transfer, multieffect evaporation, adsorption, crystallization, filtration, and drying—not to mention mass transfer and instrumentation. 

Heat Exchange and Equipment Design Multieffect Evaporators Link Excel with Other Software. 

This process of countercurrent contact of a vapor with a liquid which has been produced by partial condensation of the vapor is termed rectification. Its result is equivalent to a series of redistillations with the consumption of no additional heat and is analogous in this respect to multieffect evaporation. However, it is only the result that is similar and not the mechanism of obtaining it. 

---