Comparison of Production Processes

Raschig Process

Rashing process is the most common used process in the world. However, comparison with other processes; this process is older and has lower yields. For this process, dilute solutions and a very high ammonia/hypochlorite ratio are essential in order to obtain reasonable yields. Evaporation costs are therefore high even when steam savings are realized.

Olin-Raschig Process

This is the improved version of Rashing process by Arc Chemicals Corp. In the Olin Raschig process, which is used by Olin to produce anhydrous hydrazine for aerospace applications, the production of sodium hypochlorite is carefully controlled. A low temperature is used to prevent decomposition and chlorate formation, and the excess of sodium hydroxide is kept at a low level.

Ketazine Process

The ketazine process is a variation of the Raschig process and is based on the reaction of chloramine with ammonia in the presence of acetone at pH 12 – 14.

The ketazine process has less energy intensive, an important consideration as energy costs escalate. Disadvantages of the ketazine process are the need to dispose of organic by-products, the loss of acetone, and the problem of handling acetone vapors. Also, it is difficult to remove all the organics from the final product.

Urea Process

In a further modification of the fundamental Raschig process, urea can be used in place of ammonia as the nitrogen source. This process has been operated commercially. Its principal advantage is low investment because the equipment is relatively simple. For low production levels, this process could be the most economical one. With the rapid growth in hydrazine production and increasing plant size, the urea process has lost importance, although it is reportedly being used.

Fisons Process

This process, originally operated by Whiffen and Sons, was developed by Fisons and went on stream in the 1960s. It used methyl ethyl ketone instead of acetone to trap the hydrazine; the

hydrolysis was carried out with sulfuric acid. This process is no longer operated.

Peroxide Process

The most recent hydrazine process, invented by PCUK, is operated by ATOFINA in France and by Mitsubishi Gas in Japan. Hydrogen peroxide is the oxidizing agent in this process. The peroxide process has many advantages compared with other processes: no salt by-product, high yields, low energy consumption, low molar excess, no aqueous effluent treatment.

*In the light of this information, peroxide process is choosen for production method.

The economics of this peroxide process in comparison to the Raschig or hypochlorite–ketazine processes depend on the relative costs of chlorine, caustic, and hydrogen peroxide. An inexpensive source of peroxide would make this process attractive. Its energy consumption could be somewhat less, because the ketazine in the peroxide process is recovered by decantation rather than by distillation as in the hypcochlorite process. A big advantage of the peroxide process is the elimination of sodium chloride as a byproduct; this is important where salt discharge is an environmental concern. Block flow diagram of this process is in Appendix part.