Ethane cracking furnace

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. 

In the work reported here the coil and the fire box were simulated simultaneously by means of an optimized computer package in which the design of the radiant section of the furnace is an extension and refinement of Hottel s zone method (3 ). In this paper the approach is applied to the simulation of an industrial ethane cracking furnace. The only adaptable parameter left in the simulation model is a burner design factor, namely the fraction of the heat generated in the burner that is transferred to the burner cup. The parameter is determined by matching the exit conver s ion. 

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. 

Commercial plants Technip has been awarded four ethylene plants ranging from 500 kty up to 1,400 kty using either ethane or liquid feedstocks. While over 300 cracking furnaces have been built, and 15 units operate worldwide, numerous expansions over the nominal capacity based on progressive separation techniques are under way, with up to an 80% increase in capacity. For ethane cracking, front-end hydrogenation scheme is also available. 

Technip Ethylene/cracking furnaces Ethane to HVGO Thermal cracking of hydrocarbons in the presence of steam by highly selective GK and SMK cracking furnaces 500 2001... 

Ethane enters the pyrolysis section, which comprises a series of cracking furnaces. The ethane is heated as quickly as possible to the cracking temperature and maintained at this temperature for the minimum residence time. In order to lower the hydrocarbon partial pressure and mitigate coke forming in the pyrolysis tubes, steam is added to the ethane prior to entering the pyrolysis section (not shown). 

Ethane cracking produces a range of by-products as well as ethylene. However, relative to other feed stocks, the amount of byproducts is small and in many small-scale ethane cracking operations these are used as fuel in the pyrolysis furnace. 

In larger-scale ethane cracking operations, or those integrated into large chemical complexes, the useful by-products can be separated and used. In this instance the pyrolysis furnace is fired by fuel oil. Note that different process licensors have differing approaches to the layout of the unit operations. A typical situation is illustrated in Figure 7.2. 

Because the formation of heavy liquid products is low, LPG is cracked in a very similar process to ethane cracking. Often LPG can be co-fed to the pyrolysis furnace with ethane and there is no need for an additional process plant. 

A less effective, but more economically viable method, would be to recycle all low-value hydrocarbon by-products to the cracker furnace. This particularly focuses on methane which within the confines of an operation is typically valued relative to the fuel oil price. However, this equally applies to ethane and propane which are generally recycled to the feedstock side of the cracking furnace. Depending on the relative value, it may be optimal for minimising carbon emissions in some operations to use ethane as a fuel rather than a feedstock. 

Lead Photo KBR s SCORE (Selective Cracking Optimum REcovery) technology is used at the Olefins Plant of Saudi Kayan Petrochemical Complex (A project of SABIC) in Al Jubail, Kingdom of Saudi Arabia. The photo shows the ethane/ butane cracking furnaces, which are part of this 1.35 million tpy cracker scheduled to startup in second quarter 2010. Photo courtesy of Saudi Kayan. 

Conversion and yield of the cracking furnace is 87.6% and 67.1% respectively. The selectivity is 76.60% based on yield and conversion. Feed compositions to furnace are mainly ethane and steam. The gas to steam ratio in the feed is 3 [6]. 

However, carburization is more common in the petrochemical processing industry. A notable problem area has been the radiant and shield sections of ethylene cracking furnaces, due to high tube temperatures up to 1150°C. Apart from temperature, an increase in carbon potential of the gas mix is responsible for a higher severity of damage. High carbon potentials are associated with the ethane, propane, naphtha, and other hydrocarbons as reactants that are cracked. Carburization has been identified as the most frequent failure mechanism of ethylene furnace tubes. 

Overhead from the depropanizer is fed to the 03 splitter, after hydrogenation to convert the highly unsaturated methyl acetylene and propa-diene to propylene. The primary function of this tower is production of polymer grade or, in some cases, chemical grade propylene. A secondary function is propylene recovery because the bottoms from this column either is recycled to an ethane/propane cracking furnace or is used as propane fuel. 

Ethylene is produced using ethane in a steam cracking furnace at 800°C. Assume that the reaction takes place in an isothermal conversion reactor where ethane single-pass conversion is 65%. Develop a process flow sheet for the production of ethylene from pure ethane. Use existing software package in your university to perform the material and energy balance of the entire process. 

Olefins are produced primarily by thermal cracking of a hydrocarbon feedstock which takes place at low residence time in the presence of steam in the tubes of a furnace. In the United States, natural gas Hquids derived from natural gas processing, primarily ethane [74-84-0] and propane [74-98-6] have been the dominant feedstock for olefins plants, accounting for about 50 to 70% of ethylene production. Most of the remainder has been based on cracking naphtha or gas oil hydrocarbon streams which are derived from cmde oil. Naphtha is a hydrocarbon fraction boiling between 40 and 170°C, whereas the gas oil fraction bods between about 310 and 490°C. These feedstocks, which have been used primarily by producers with refinery affiliations, account for most of the remainder of olefins production. In addition a substantial amount of propylene and a small amount of ethylene ate recovered from waste gases produced in petroleum refineries. 

The separation train of the plant is designed to recover important constituents present in the furnace effluent. The modem olefin plant must be designed to accommodate various feedstocks, ie, it usually is designed for feedstock flexibiUty in both the pyrolysis furnaces and the separation system (52). For example, a plant may crack feedstocks ranging from ethane to naphtha or naphtha to gas oils. 

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