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Ethylene Manufacture Technology Description

Online Ethylene Data: Manufacture, Uses and Applications

Intratec Chemical Process Library is the first free online encyclopedia of chemical process technologies. Our Library covers not only processes description themselves, but also the economics surrounding chemicals production, providing real-world knowledge on the production of several chemical commodities. Click here to check all chemicals covered.

In this page you will find free data about Ethylene, including:

  • What is Ethylene
  • How to make Ethylene
  • Ethylene uses and applications

This page presents brief synopsis of Ethylene production technology, describing, in a concise way, relevant technical and economic aspects. Each manufacturing process description will consist of:

  • Major process steps
  • Simplified, schematic flow diagram & key equipment
  • Important safety or environmental considerations
  • Economic perspective, comprising capital expenditures and/or operating expenses

All content from Intratec's Chemical Process Library was produced based on reports published by Intratec. To learn more about Ethylene production processes presented below and others examined in Intratec reports, click here.

Ethylene Manufacture via Ethanol Dehydration - Similar to a BP Chemicals Technology

Ethylene is arguably the most important building block of the petrochemical industry, frequently produced via steam cracking of a range of petroleum-based feedstocks. Concerns about global warming have motivated research into ethylene manufacture from renewable sources.

The “green” ethylene made from ethanol (for example, from corn, sugarcane or lignocellulosic biomass) represents a chemically identical alternative to its petrochemical equivalent, and can contribute to the overall reduction of greenhouse gas emissions.

Technology Description

The polymer-grade (PG) ethylene production via ethanol dehydration process depicted in the figure below was compiled based on a U.S. patent published by BP Chemicals (London, U.K.; www.bp.com; U.S. patent no. 8,426,664). Since 2008, BP has established more than ten patents on this subject.

Ethylene Manufacture via Ethanol Dehydration - Block Flow Diagram

Ethanol Dehydration has an overall endothermic equilibrium. The ethylene yield is favored by higher temperatures, while lower temperatures favor production of diethyl ether (DEE). The major process steps are outlined below.

Treatment

Fresh ethanol is combined with the recycled ethanol and DEE from the ethylene column and sent to the aldehyde removal column, which removes the aldehydes that came from the fresh ethanol feed, as well as the aldehydes and C4 hydrocarbons generated in the reaction step.

Reaction

The bottom stream from the aldehyde removal column is sent to the feed vaporizer and superheater before being sent to the reactors. The process uses fixed-bed reactors with a heteropolyacid catalyst supported by silica. The product stream from reaction is cooled and sent to the purification section.

Purification

The reactor’s outlet stream ...

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Ethylene Manufacture via Ethanol Dehydration - Similar to a Chematur Technology

With a global nominal capacity of about 140 million ton/yr, ethylene is among the main petrochemicals produced worldwide, and is a key building block for the industry. It is a raw material for the manufacture of polyethylene, polyvinyl chloride (PVC), ethylene oxide and many other products. Ethylene is produced mostly via steam cracking of petroleum-based feedstocks, such as naphtha.

Global concerns about sustainability and global warming have prompted the chemical industry to develop production routes for ethylene that utilize non-petroleum resources. Renewable ethylene-production alternatives have begun to emerge in this context.

“Green” ethylene can be produced by the dehydration of ethanol, which can be produced from renewable feedstocks such as sugarcane and corn. Ethanol-derived ethylene is chemically identical to traditional ethylene, so downstream processing is equivalent.

Technology Description

A process for ethylene production via ethanol dehydration similar to the processes developed by Chematur Technologies AB and Petron Scientech Inc. is depicted in the figure below. The reaction occurs in four fixed-catalyst-bed adiabatic reactors.

Reaction

Ethanol is vaporized, heated in a furnace and fed to the first reactor. During reaction, the temperature drops and the output stream must be re-heated before entering the next reactor. This is repeated until the fourth reactor, where ethanol reaches 99% conversion. Next, the reactorproduct stream is cooled in a wasteheat boiler, generating steam.

Quenching, compression, caustic washing and drying

After reaction, the product stream’s water content is reduced in a quench column. The ethylene stream leaves by the overheads and is compressed before entering the washing column, where impurities are removed with a caustic solution. Process water is also supplied to this column to avoid caustic entrainment along with the ethylene overhead stream, which is cooled by interchange with the ethylene product stream. Water separated in the compression and cooling stages is recycled to the quench column. Next, the gas stream is dehydrated in a molecular sieve unit.

Purification

After cooling by interchange ...

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Ethylene Manufacture via Cracking of Ethane-Propane

The process shown in figure below is a steam-cracking process for ethylene production from an ethane-propane mix. The process can be divided into three main parts: cracking and quenching; compression and drying; and separation.

Cracking and Quenching

Initially, an ethane-propane mix is fed to furnaces in which, under high-severity conditions, it is cracked, forming ethylene, propylene and other byproducts. The furnace outlet stream is subsequently fed to a water-based quench, to prevent further reactions and formation of undesirable byproducts.

From a decanter downstream from the quench tower, heavies, condensed dilution steam, tar and coke are removed. Cracked gas from the quench is then directed to compression and separation.

Compression and Drying

The compression of the cracked gas is performed across five stages. After the third stage of compression, carbon dioxide and sulfur are removed from the cracked gas by caustic soda and water washes in a caustic scrubber. The compressed cracked gas is cooled and subsequently dried in molecular sieves that remove most of the water.

Separation

The dried cracked gas is fed to a cold box for the removal of hydrogen and light hydrocarbons, while minimizing ethylene losses.

At this point, condensates from the chilling train are fed to a series of separation columns. In the first column (demethanizer), methane is obtained from the top and further used in the cold box, while the bottom stream is fed to a second column (deethanizer).

The top of the deethanizer, composed primarily of ethylene and ethane, is fed to an acetylene converter and then fractionated in the C2-splitter. In this column, lights are removed from the overheads and recycled to the compression system, while polymer-grade (PG) ethylene is drawn from the column as a side stream. Ethane, from C2-splitter bottoms, is recycled to the cracking furnaces.

The deethanizer bottom stream ...

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Methanol-to-Olefins Process

Ethylene and propylene are mainly produced by steam cracking of hydrocarbons, such as naphtha, propane and ethane. The methanol-to-olefins (MTO) process is an alternative approach to producing these light olefins from methanol feedstock, which can be derived from other raw materials, including natural gas, coal or biomass.

The figure below illustrates an MTO process similar to one developed jointly by UOP LLC and Norsk Hydro A/S. This process synthesizes olefins from methanol using a SAPO-34-type zeolite catalyst in a fluidized-bed reactor. The process can be divided into three main areas: reaction and regeneration; quench, compression and caustic wash; and product fractionation.

Reaction and regeneration

Methanol feed is vaporized, mixed with recovered methanol, superheated and sent to the fluidized-bed reactor. In the reactor, methanol is first converted to a dimethylether (DME) intermediate and then converted to olefins with a very high selectivity for ethylene and propylene. During the reaction, coke accumulates on the catalyst, which is circulated to the fluidized-bed regenerator system. In the regenerator, the coke is removed by combustion with air to maintain the catalyst activity. After leaving the reactor, the reacted stream exchanges heat with the reaction feed, in order to recover the heat generated by the exothermic reaction.

Quench, compression and caustic wash

The output from ...

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