Green treatment process for cleaning exhaust gas generated in air oxidation of benzene homologs

Patent metadata

Field	Value
Publication number	US-9322359-B2
Application number	US-201113702099-A
Country	US
Kind code	B2
Filing date	Mar 11, 2011
Priority date	Oct 20, 2010
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

A green treatment process for cleaning exhaust gas generated in the air oxidation of benzene homologs is disclosed. It takes the hot pressurized exhaust gas generated in the benzene homolog air oxidation process as driving power and heating source: firstly, introducing the said exhaust gas into a turbine refrigerator so that it can drive the refrigerator to generate the cooling capacity that will be utilized for condensing the gas phase in the upper part of the flash evaporator and for trapping organics entrained in the exhaust gas; then, leading the exhaust gas with lowered temperature and pressure into corresponding heat exchangers to provide a part of heating source for the flash evaporator and to preheat the reaction raw materials. Furthermore, introducing the condensed exhaust gas into a water absorption scrubber for further removal of trace organics entrained therein.

First claim

What is claimed is:

1. A green treatment process for cleaning exhaust gas generated in air oxidation of benzene homologs comprising the following steps:
step 1. introducing benzene homologs, solvents and catalysts into a reactor in accordance with the requirements of an oxidation process, mixing the benzene homologs, solvents and catalysts and heating the benzene homologs, solvents and catalysts to a pre-set temperature and compressing the benzene homologs, solvents and catalysts to a pre-set pressure, and then introducing purified air through an air compression system into the reactor at a pre-set flow rate;
step 2. starting up an air oxidation process of benzene homologs when the reactor reaches the pre-set pressure; opening an exhaust gas outlet valve at a top of the reactor and controlling the emission of a gas phase generated in the air oxidation process at a certain flow rate so that the pressure in the reactor is maintained at a required operating level; transporting a product, of intermediate products, solvents and unreacted raw materials of the air oxidation process of benzene homologs by a pump into a flash evaporator for flash evaporation; introducing said gas phase, which is hot and pressurized after the air oxidation process, channeled out via the outlet at the top of the reactor into a turbine refrigerator to drive the turbine refrigerator for generating a cooling capacity;
step 3. after doing work in the turbine refrigerator for generating the cooling capacity, firstly introducing the hot pressurized gas phase into a gas-liquid separator, wherein most of the benzene organics contained therein condensed into liquid and collected in a lower part of a separator; transporting the condensed liquid through corresponding valves and pipes into the flash evaporator for separation; introducing the uncondensed gas phase from the gas-liquid separator through a pipe at a top of the separator into a heating coil at a bottom of the flash evaporator so that said uncondensed gas phase from the gas-liquid separator provides part of thermal energy required for the flash evaporation process of the flash evaporator; after coming out of the heating coil at the bottom of the flash evaporator, introducing the gas phase from the gas-liquid separator through pipes into a heat exchanger to preheat the reaction raw materials, which enables the residual heat contained in said uncondensed gas phase from the gas-liquid separator to be further utilized;
meanwhile, transporting the cooling capacity generated by the turbine refrigerator by a coolant, wherein the coolant is salt water or ethylene glycol, via a pump into a condenser so that said coolant can condense an uncondensed gas phase that has been channeled out from a top outlet of the flash evaporator; introducing the liquid that is obtained through the condensation process in said condenser through a pipe into a rectification system for separation; the coolant coming out from the condenser is then introduced into a cold trap to deep freeze the uncondensed gas phase that is generated in the gas-liquid separator and has been channeled into the cold trap via the heat exchanger; wherein in comparison with the hot pressurized gas phase originally generated in the air oxidation process, said uncondensed gas phase out of the heat exchanger bears lowered temperature and pressure; after being further deep frozen by said coolant in the cold trap, further trapping the benzene organics entrained in said uncondensed gas phase out of the heat exchanger;
step 4. the temperature of the uncondensed gas phase from the gas liquid separator being close to the air temperature at the outlet of the heat exchanger as the residual heat contained in said uncondensed gas phase from the gas-liquid separator has been fully utilized; wherein when the uncondensed gas phase from the gas-liquid separator is introduced through a pipe into the cold trap and is cryogenically frozen below 10° C. by the coolant in the cold trap, more than 99% of the benzene organics in the uncondensed gas phase from the gas-liquid separator have been condensed into liquid and collected to be separated in the rectification system; subsequently, introducing the remaining gas phase that contains only a trace amount of benzene organics through a top outlet of the cold trap into a water absorption scrubber system so that the residual benzene organics can be further removed; and
step 5. after the heat exchange process carried out in the cold trap, flowing the coolant out of a outlet of the cold trap and back into the turbine refrigerator for regaining cooling capacity for another round of circulation.

2. A green treatment process for cleaning exhaust gas generated in air oxidation process of benzene homologs as defined in claim 1 , wherein the refrigeration process is operated by pressure energy; wherein the hot pressurized exhaust gas generated in the air oxidation reaction is introduced into a specially designed turbine, which, under the function of the pressurized exhaust gas, drives the refrigerator to do work for generating cooling capacity.

Assignees

• Zhang Zhibing
• Wang Guannan
• Dai Yue
• Li Lei
• Meng Weimin
• Nanjing University Of Technology

Inventors

• Zhang Zhibing
• Wang Guannan
• Dai Yue
• Li Lei
• Meng Weimin

Classifications

• B01D3/007 Primary

  Energy recuperation; Heat pumps · CPC title

• B01D53/002

  by condensation · CPC title

• B01D2257/70

  Organic compounds not provided for in groups B01D2257/00 - B01D2257/602 · CPC title

• B01D3/06

  Flash distillation · CPC title

• C07C51/16

  by oxidation (C07C51/145 takes precedence) · CPC title