Cracking furnace

Propylene Dimer. The synthesis of isoprene from propjiene (109,110) is a three-step process. The propjiene is dimeri2ed to 2-methyl-1-pentene, which is then isomeri2ed to 2-methyl-2-pentene in the vapor phase over siUca alumina catalyst. The last step is the pyrolysis of 2-methyi-2-pentene in a cracking furnace in the presence of (NH 2 (111,112). Isoprene is recovered from the resulting mixture by conventional distillation. 

Limitations in the material of constmction make it difficult to use the high temperature potential of fuel hiUy. This restriction has led to the insertion of gas turbines into power generation steam cycles and even to the use of gas turbines in preheating air for ethylene-cracking furnaces. 

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). 

The second law can also suggest appropriate corrective action. Eor example, in combustion, preheating the air or firing at high pressure in a gas turbine, as is done for an ethylene (qv) cracking furnace, improves energy efficiency by reducing the lost work of combustion (Eig. 4). 

Fig. 4. Use of gas turbine air preheat for ethylene cracking furnace. The gas turbine exhaust duct contains 17% oxygen at 400°C.

Most gas turbine appHcations in the chemical industry are tied to the steam cycle, but the turbines can be integrated anywhere in the process where there is a large requirement for fired fuel. An example is the use of the heat in the gas turbine exhaust as preheated air for ethylene cracking furnaces as shown in Figure 4 (8). 

The Cj plus bottoms from the demethanizer then go to the deethanizer. A propylene-propane bottoms product containing 90-92% propylene is obtained which may either be sold, used directly as propylene- 90, or further purified. The ethylene-ethane overhead from the deethanizer is separated in the splitter tower yielding a 99.8% overhead ethylene product at -25°F. The ethane bottoms at -l-18°F may either be sent to fuel gas or used as feed to an ethane cracking furnace. Overall ethylene recovery in these facilities is about 98%. The product is of very high purity with less than 50 parts per million of non-hydrocarbon contaminants and a methane plus ethane level below 250 ppm. 

Commercial Yields from a Cracking Furnace Used in Production of Ethylene... 

As a general rule difficult or expensive separations should be performed last, since by that time less total material will be involved. Consider Table 4-1, which gives the product mix obtained in a cracking furnace of an ethylene plant and the normal boiling points of the compounds. Suppose it is desired to separate the six groups listed in the table using distillation. The separation of ethylene from ethane and propylene from propane will be the most difficult because they have the smallest boiling-point differences. Therefore, these steps should be performed last. 

PYROCAT A steam cracking process for converting petroleum into light olefins in which a catalyst is deposited on the walls of the heat-exchanger coils in the cracking furnace. The... 

Optimal flow rates for cracking furnace for different restrictions on ethylene and propylene production... 

Gas chromatography-mass spectrometry (gc/ms GC-MS), 4 616 6 381, 431 archaeological materials, 5 743 use in forensic toxicology, 12 91 Gas-controlled heat pipe, 73 234—235 Gas cracking furnaces, additives to, 10 609-610 Gas diffusion... 

In an olefins plant, the feed is subjected to very high temperatures in cracking furnaces for a few moments and then cooled rapidly to stop the cracking. Elaborate separation facilities are necessary to separate the olefins. from the by-products of the cracking process. 

The reaction relies on the brute force of high temperatures and pressures and must be carried out in hardware much like the cracking furnaces described in the ethylene chapter. As always with cracking, undesirable reactions occur, resulting in the formation of CO2 and carbon. The latter is particularly a nuisance because it sets down on the catalyst and deactivates it. 

A gas oil cracking plant consists of two cracking furnaces, a soaker, a main fractionator, and auxiliary strippers, exchangers, pumps, and drums. The main fractionator (150 psig) consists of four zones, the bottom zone being no. 1. 

Figure 17.15. A fired heater as a high temperature reactor, (a) Arrangement of tubes and burners (1) radiant tubes (2) radiant panel burners (3) stack (4) convection chamber tubes (Sukhanov, Petroleum Processing, Mir, Moscow, 1982). (b) Radiant (surface-combustion) panel burner (1) housing (2) ceramic perforated prism (3) tube (4) injector (5) fuel gas nozzle (6) air throttle Sukhanov, Petroleum Processing, Mir, Moscow, 1982). (c) Fired tubular cracking furnace for the preparation of ethylene from naphtha.

The EDC cracking is an integral part of this process. Key points in the plant design include the cracking furnaces, which utilize alloy tubes such as Inconel or Incoloy, a quench tower for lowering process tempera-... 

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