Heat exchangers vacuum condensers

A type of shell and tube heat exchanger that condenses exhaust steam and creates a vacuum, improving the efficiency of a turbine. 

Downstream of the reaction zone, the lower static pressure permits the reactor content to boil and applies the thermosyphon effect for circulation. EDC vapor leaves the horizontal vessel and either enters the reboiler of a column (e.g., reboiler of high-boil-heads and/or vacuum column) or a heat exchanger, which condenses the EDC vapor. The reaction heat is transferred to the column indirectly. A fraction of the condensed EDC is fed back to the reactor and the rest is directly sent to the EDC cracker without further distillation. 

Figure 3.16. Process layout for PVMBR system IV. HE heat exchanger C condenser VP vacuum pump. From Groot et al [3.58], with permission from Springer-Verlag.

Heat-transfer equipment in the form of heat exchangers and condensers is a vital part of the chemical process industries. Heat exchangers are used for the cooling or heating of all sorts of process materials, while condensers are used largely for the condensation of vapors from evaporators and consequent production of vacuum, and for the recovery of materials volatilized from stills. 

Typical equipment made from tantalum includes heat exchangers, reaction vessels liners, thermowells, and heating elements or heat shields for high temperature vacuum sintering furnaces. Tantalum fabricated parts are found in the manufacturing of pharmaceuticals, explosives, insecticides, dyes, acidic baskets for silver cyanide barrel platers, and in hydrochloric and hydrobromic acid condensers. 

Dearation can be either vacuum or over pressure dearation. Most systems use vacuum dearation because all the feedwater heating can be done in the feedwater tank and there is no need for additional heat exchangers. The heating steam in the vacuum dearation process is a lower quality steam thus leaving the steam in the steam cycle for expansion work through the steam turbine. This increases the output of the steam turbine and therefore the efficiency of the combined cycle. In the case of the overpressure dearation, the gases can be exhausted directly to the atmosphere independently of the condenser evacuation system. 

Plate and frame e.xchangers (plate heat exchangers)-used for heating and cooling in reactor off-gas quenching, vacuum condensers, desuperheating, and humidification. 

Figure 6-22. Dissolved air released from water on direct contact in vacuum systems. Reprinted by permission. Standards for Direct Contact Barometric and Low Levei Condensers, 4th Ed., Heat Exchange Institute, 1957.

Figure 3-1. Flow diagram of atmospheric and vacuum distillation units (1,3) heat exchangers (2) desalter, (3,4) heater (5) distillation column, (6) overhead condenser, (7-10) pump around streams, (11) vacuum distillation heater (12) vacuum tower.

Applications include reactor off-gas quenching, vacuum condensers, cooler-condensers, desuperheating and humidification. Water-cooling towers are a particular example of direct-contact heat exchange. In direct-contact cooler-condensers the condensed liquid is frequently used as the coolant, Figure 12.65. 

Process documentation 2, drying chamber with shelves 3, operation control 4, ice condenser 5, vacuum pump with exhaust filter 6, refrigeration machine for the ice condenser 7, refrigeration machine for the shelves 8, circulation pump for the brine 9, heat exchanger (Lyovac GT 6, AMSCO Finn-Aqua, D-50354 Hiirth, Germany). 

Fig. 2.49.2. Schema of a freeze drying production plant with approx. 20 m2 shelf area. The chamber and condenser are in the same vacuum chamber, separated by a wall in which the valve is built, providing the shortest possible path for the water vapor. The condenser and the brine heat exchanger are cooled by LN2. The condenser surface is made from plates (Fig. 2.49.3), its temperature can be controlled between -110 °C and -60 °C. The shelves can be controlled by the circulated brine between -70 °C and +50 °C. The trays with product can be automatically loaded and unloaded from a trolley. The shelves can be pressed together in one block and the trays are loaded to the shelves by pushing one shelf after another in front of the trolley.

The bulk of the effluent is run through a cooler (heat exchanger) and a condenser to remove the light ends that include traces of carbon monoxide and carbon dioxide and by-product water. The bottom stream is maleic acid, which is easily dehydrated, as in Figure 20—4, by vacuum distillation or azeotropic distillation with ortho-xylene. See Chapter 3 if youVe forgotten totally everything about azeotropic distillation.) The dehydrated maleic acid is maleic anhydride. Further purification is done by distillation.,... 

Tall oil is a byproduct obtained from the manufacture of paper pulp from pine trees. It is separated by vacuum distillation (50 mm Hg) in the presence of steam into four primary products. In the order of decreasing volatility these are unsaponifiables (US), fatty acid (FA), rosin acids (RA), and pitch (P). Heat exchangers and rcboilers are heated with Dowtherm condensing vapors. Some coolers operate with water and others generate steam. Live steam is charged to the inlet of every reboiler along with the process material. Trays are numbered from the bottom of each tower. 

The fatty adds from the hydrolyzer are collected in the still feed tank and vacuum-dried to reduce moisture to low levels. Then they are flash-distilled at an absolute pressure of 2-5 mmHg. The still bottoms are recirculated through heat exchangers back to the still to carry the heat necessary for vaporizing the fatty acids. The stall bottoms, which contain the zinc soap catalyst and unsplit fat, are removed from the system, acidulated to remove the zinc, and frequently used in animal feeds. The fatty acid vapors from the still pass to several water condensers m series. The condensed fatty acids diop to a singe tank for posthaidening 01 diiectly foi neutialization. 

---