Copyright © 2000 American Chemical Society
Process Description and Sources: Chloroacetylchloride (CAC) is used primarily as an intermediate in the manufacture of monochloroacetic acid (MCAA). Most of the MCAA at Dow-Midland is sold. However, some is used as an intermediate to manufacture the pesticide 2,4-dichlorophenoxy acetic acid, more commonly known as 2,4-D.
Vinylidene chloride and oxygen are
the primary raw materials used to produce CAC (see Figure 1, right). The
oxidation reaction is highly exothermic, generating significant heat.
Currently, the reactor is cooled with water from a cooling tower
system.
The source of all wastes in CAC is the formation of byproducts in the reactor. These wastes exit the process at two primary sources: vent gases from the reactors and overhead tars from distillation. Wastes from these two sources account for about 18% of all wastes addressed in this project.
Pollution Prevention Options and Reductions: Several pollution prevention options were explored, including improved cooling, distillation column optimization, and in-process recycling. The pollution prevention option of choice focused on the fundamentals of the chemical reaction to improve the overall efficiency through improved cooling. All the wastes from the process are generated as byproducts through inefficiencies in the reaction. Lower reaction temperature would decrease the formation of these unintended byproducts and increase yield of CAC product.
Dow determined that additional cooling could be provided through refrigeration instead of the existing cooling towers. Improved refrigeration was estimated to reduce the generation of byproduct wastes by approximately 1.8 million lb, 1.3 million of which were priority chemicals for this project (see Table 3).
Financial Savings/Costs: Savings from the avoided cost of lost raw materials and waste treatment from CAC was estimated to be $375,000 per year.
Costs derived largely from the purchase of new refrigeration equipment. New equipment was estimated to cost $500,000. In addition, $20,000 was requested to enable technical staff to conduct more detailed technical analysis for the project.
In an effort to improve the economics of the project, Dow CAC staff contacted brokers of used refrigeration equipment. A suitable refrigeration unit was identified, which greatly improved the economics of the project. CAC staff then contacted the business leaders who make funding decisions to discuss the new information. Funding was approved in less than one week. Equipment will be fully operational by fall 2000.