PetrochemicalsExhaust Gas Treatment Solutions

(physical works cases)

Industry Introduction


Petrochemical industry is an important part of the chemical industry, has an important role in the development of the national economy, is one of the pillar industry sectors in China. Petrochemical refers to oil and natural gas as raw materials, the production of petroleum products and petrochemical products processing industry. Petroleum products, also known as oil products, mainly include a variety of fuel oil (gasoline, paraffin, diesel, etc.) and lubricating oil, as well as liquefied petroleum gas, petroleum coke, paraffin wax, asphalt and so on.


Pollution Hazards

The production process of petrochemical plants generates a large number of VOC-type exhaust: benzene, toluene, xylene, acrylic acid, ether, lipids, alcohols, ketones and styrene and other organic exhaust. It emits a very strong and big chemical odour. Moreover, most of these chemical odours are very harmful to human body, if not handled properly, they will not only have a great impact on the surrounding environment, but also cause great damage to the health of the employees of the chemical plant and the surrounding residents.


Overview of the treatment programme

Petrochemical industry VOCs emission sources are more, can be broadly divided into: equipment leakage of static and dynamic sealing points; organic liquid storage and reconciliation of volatile losses; organic liquid loading and unloading volatile losses; wastewater collection, storage, treatment and disposal process fugitive; combustion flue gas emissions; process organised emissions; process disorganised emissions; sampling process emissions; flare emissions; non-normal working conditions (including the start, stop and maintenance) emissions; cooling towers, Circulating water cooling system release; accidental emissions and other 12 types of source items.

Exhaust gas emitted from storage tanks is recommended to use absorption, adsorption, condensation, membrane separation and other class A recycling combination technology as well as with regenerative combustion, regenerative catalytic combustion, catalytic combustion and other class B destruction technology, the most commonly used activated carbon adsorption + catalytic combustion combination of governance processes.

Loading and unloading process emissions can be absorbed, adsorption, condensation, membrane separation and other class A recycling combination of technologies and with regenerative combustion, regenerative catalytic combustion, catalytic combustion and other class B destruction of the combination of technologies, the most commonly used activated carbon adsorption + catalytic combustion combination of governance processes.

Grease trap, air flotation tank and other high concentration of waste gas should be used catalytic combustion, incineration and other treatment technologies, should not be used low temperature plasma, UV photolysis and other single — inefficient treatment technology.

Aeration ponds and other low concentration of waste gas can be used biological method, adsorption, incineration and other treatment technologies.

Other waste gas sources are not repeated, in summary, the petrochemical industry VOCs recommended activated carbon / zeolite molecular sieve adsorption desorption + CO catalytic combustion treatment technology.

Process flow
 
This device process is: adsorption concentration — desorption desorption — catalytic combustion process. Take a single gas circuit mode of operation, by two activated carbon adsorption bed, a catalytic combustor (supplemented by low-pressure fans, valves and other components). Exhaust gas after pretreatment to remove dust, particulate matter, sent to the activated carbon adsorption bed A, when the activated carbon adsorption bed A is close to saturation, first of all, the processed gas will be automatically switched to the activated carbon adsorption bed B (the activated carbon adsorption bed A stops adsorption operation), and then the activated carbon adsorption bed A with the hot air flow of desorption and desorption, the organic matter from the activated carbon desorption down. In the desorption process, the organic waste gas has been concentrated, the concentration of the original dozens of times higher, up to 2000ppm or more, concentrated waste gas to the catalytic combustion device, and finally become CO2 and H2O discharge.

After completing the desorption and desorption, the activated carbon adsorption bed A enters into the standby state, and when the activated carbon adsorption bed B is close to saturation, the system automatically switches back to the activated carbon adsorption bed B at the same time for desorption and desorption, and so the cycle works.

When the concentration of organic waste gas reaches 2000ppm or more, the catalytic bed can maintain self-ignition, without external heating. This programme not only greatly saves energy consumption, but also reduces the investment in equipment at the same time because the processing capacity of the catalytic combustor is only 1/10 of the original waste gas processing capacity (3000m3/h). This programme is suitable for both continuous and intermittent work.

Desorption and depayment of a single activated carbon adsorber takes about 2-3 hours.

The adsorption fan is controlled by a frequency converter and can be adjusted according to the required air volume or the net negative pressure at the inlet of the plant.