Monochloroacetic Acid Plant

Brief Overview

Capacity:

18 million lbs/yr or 9,000 TPY

Built:

1976

Status:

The plant has operated every year since its original startup.

Major Upgrades:

$2 millions in 1998 to automate controls

Raw Materials:

Based on lb 96.6% MCA by wt 2.8%DCA (dichloroacetic acid) and 0.6% Acetic acid:
- Chlorine: 0.740 lb/lb MCA
- Acetic Anhydride: 0.105 lb/lb
- Acetic: 0.532 lb/lb

Utilities Consumption:

Based on historical data
- Steam: 2.275lb/lb
- Electricity: 0.144Kwh/lb
- Air: 3.709 lb/lb

Documentation:

Available
 

Major Equipment:

- Chlorine vaporizer
- Chlorine scrubber
- Chlorinators
- Overhead Condenser/Scrubber System
- HCl Absorber
- MCA Still.

Process Description

The manufacturer of MCA (monochloroacetic acid) involves the reacting of the chlorine, acetic acid, and acetic anhydride in the Chlorinators under high temperature (200 to 240 degree F). The chlorine is supplied in liquid form (from tank car), and then turned into vapor by the Chlorine Vaporizer. The chlorine vapor will pass through a knock out pot (to remove the entrained liquid) and a heater (to ensure a high temperature) and enter the bottom of the Chloribators. The acetic acid and acetic anhydride are fed to the Chlorinators in the liquid form.

Several reactions take place inside the Chlorinators. The acetic anhydride reacts with HCl to produce acetyl chloride (the catalyst) and acetic acid. The acetyl chloride reacts with chlorine to produce chloroacetyl chloride and HCl. The chloroacetyl chloride reacts with acetic acid to form MCA and acetyl chloride. Furthermore, the chloroacetyl chloride can also react with another chlorine to form dichloroacetyl chloride and HCl. The dichloroacetyl chloride then reacts with acetic acid to form DCA. MCA can also react with chloroacetyl chloride to form DCA.

The reaction mix leaving the Chlorinators will have 50 - 80% MCA (depending on the desired DCA level in the final product, as requested by the CMC plant at the time), 3 - 5.5% acetyl chloride, and the remaining is acetic acid. The mix overflows the Chlorinators into the Crude Tank. The HCl generated from the reaction, along with acetyl chloride, acetic acid and MCA vapors will go to the Chlorinator off gas (vent) system. These vapors will first pass through the Primary and Secondary Off Gas Coolers (using CTW for cooling), then a new Tertiary Off Gas Cooler (using refrigerated glycol as coolant) to remove most of the condensible vapors. The condensed liquid (MCA, acetyl chloride and acetic acid) will return to the inlet of the Chlorinators. The uncondensed gas then passes through a new Catalyst Scrubber and the Vapor After Cooler (using refrigerated glycol as coolant) to remove the remaining condensible vapors. The gas then enters the HCl Absorber Cooler and HCl Absorber Tail Tower to scrub off the HCl, and be discharged through the Sewer Scrubber into the atmosphere. The weak HCl from the HCl Absorber Cooler is discharged to the Industrial Sewer.

The MCA mix in the Crude Tank has to be sent to the MCA Still for separation. The feed will first pass through the MCA Vaporizers and enter the MCA Still in the vapor form. The MCA Still is operated under vacuum (about 21.5" Hg Vacuum at the top). The vacuum is provided by a steam jet. The distillate of the MCA Still, which contains mostly acetic acid, with a small amont of acetyl chloride and MCA, will be recycled back to the inlet of the Chlorinators. The bottom stream of the MCA Still will be molten MCA product, with 2.9 to 3.8% DCA (depending on the requirement of CMC plant at the time) and a very small amount of acetic acid.