Heat recovery from process effluents

Textile processing houses discharge a lot of contaminated hot waste water and emit smoke, which are sources of water and air pollution. There is an inter-relationship of energy recovery and environmental protection. Increased temperature have negative effect on the organisms living in water and destroy the ecological system. The waste water and exhaust gas can be used to heat up clean, cold water and this can be returned to the production process. 

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From the reactor, the effluent flows through a separator (for the separation of inorganic salts precipitated during the process), a heat exchanger (with the influent), a heat recovery unit, an effluent cooler, and a letdown system to return the effluent to the ambient pressure. Then, a liquid/gas separator sep-... 

Understand Process Characteristics H2, H2S, and NH3 and light ends are removed from reaction effluents through a series of separation and flashes, resulting in the reaction products in a liquid form, which goes to the stripper, the feed heater, and then to the main product fractionator. The task of the product fractionation is to separate different products based on their product specihcations such as distillation endpoint, ASTM D-86 T90% or T95% point, and so on. Side draws from the column go to the product strippers where kerosene and diesel products are made. The net draw from the column bottom is called unconverted oil (UCO), which is recycled back to the reaction section for nearly complete conversion. There are two pump-arounds, namely, kerosene and diesel pumparounds, as a main feature of heat recovery from the main fractionation column. 

Selection of the high pressure steam conditions is an economic optimisation based on energy savings and equipment costs. Heat recovery iato the high pressure system is usually available from the process ia the secondary reformer and ammonia converter effluents, and the flue gas ia the reformer convection section. Recovery is ia the form of latent, superheat, or high pressure boiler feedwater sensible heat. Low level heat recovery is limited by the operating conditions of the deaerator. 

Although there are minor differences in the HCl—vinyl chloride recovery section from one vinyl chloride producer to another, in general, the quench column effluent is distilled to remove first HCl and then vinyl chloride (see Eig. 2). The vinyl chloride is usually further treated to produce specification product, recovered HCl is sent to the oxychlorination process, and unconverted EDC is purified for removal of light and heavy ends before it is recycled to the cracking furnace. The light and heavy ends are either further processed, disposed of by incineration or other methods, or completely recycled by catalytic oxidation with heat recovery followed by chlorine recovery as EDC (76). 

In early days of Phase I, the predominant feedstock for ammonia synthesis was coke. Synthesis gas was either produced at atmospheric pressure in water-gas shift units or prepared by purification of coke oven gas. In these early plants, the process effluents from the ammonia converter were cooled without recovery of heat. Due to the lack of technology regarding the attainable size of the converter pressure shell, the physical dimensions of the converter were limiting factors for the achievable production capacity. Therefore, a particular emphasis was placed on maximization of the production capacity for a given volume [139]. During World War II, several plants were built in the United States, based on natural gas feedstock. Since then, natural... 

Description If feed is crude methanol, water is separated out in the methanol column (1). The treated feed methanol is sent to a DME Reactor (2) after vaporization in (3). The synthesis pressure is 1 MPaG-2 MPaG. The inlet temperature is 220°C-275°C, and the outlet temperature is 300°C-375°C. This process is a one-pass conversion from methanol to DME. DME reactor yields are 70%-80%. The reactor effluents— DME with byproduct water and unconverted methanol—are fed to a DME column (4) after heat recovery and cooling. 

Figure 2.10 Schematic of hybrid vapor stripping-membrane vapor permeation process ("membrane-assisted vapor stripping") process for recovering and drying aicohois from water. Feed/ effluent heat recovery exchanger on stripping coiumn not shown.

The SUPERFLEX FCC system is similar to that of a conventional FCC unit and consists of riser reactor, regenerator vessel and units for air compression, catalyst handling, flue gas handling and feed and effluent heat recovery. The SUPERFLEX system should be integrated into an ethylene plant in order to minimize capital investment, with the feedstock obtained directly from the steam cracker and shared common product recovery. The cooled reactor effluent can be processed in a nearby existing ethylene plant recovery unit. Alternatively, the effluent can be processed in a partial recovery unit to recover recycle streams and olefin-rich streams concentrated for further processing in a nearby ethylene plant. 

The effluent from the reactor is cooled in a heat exchanger. The EO, byproducts, and unreacted ethylene are separated in a water-wash column in a manner just like the solvent recovery process described in Chapter 2. The EO is absorbed by the water while the by-products (mainly CO2, plus the everpresent cats and dogs in small quantities), and unreacted ethylene are not. The EO/water solution is then steam-stripped and purified by fractionation. 

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