INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY #259

1.	Headline:  Internal recycling at a chemical manufacturing plant

2.	Background:  Within the framework of its development programme, Grande Paroisse has installed a 
recycling unit of the blown down water coming from the hydrolysis of cyanide acid in the 
ATOCHEM plant. The recycled blown down water is used in its chemical fertilizer plant.  This case 
study was completed in 1990.

3.	Cleaner Production Principle:  Internal recycling

4.	Description of Cleaner Production Application:  

	Information about the process and wastes

	The production of cyanide acid is composed of :  

	--the treatment of urea at 350C, giving an ammoniacal gaseous effluent and raw cyanide acid. The 
gaseous effluent is saturated with nitric acid in order to form ammonium nitrate.
	--the hydrolysis of cyanide acid in an acid environment at 105C.
	--cooling at 60C and drainage of the hydrolysis product in order to separate the pure cyanide acid 
from the mother lye which is recirculated in hydrolysis.
	--The blown down water of the mother lye constitutes the discharge of the unit : 12 to 15 m3/day i.e. 
17 to 22 tons of total nitrogen among which 600 to 800 kg/day of ammoniacal nitrogen.

	The operation concerns the recycling of the blown down water in the manufacture of ammonitrate on 
site.

	The blown down water is conveyed to an annex reactor where hydrolysis is extended to transform 
completely the amelites and the amelines into cyanide acid. After quality control, the cyanide acid 
formed is treated in the saturator with nitric acid and the ammoniacal gaseous discharge of the urea 
heat treatment in order to form ammonitrate continuously.

	Material / energy balance and substitution

						BEFORE			AFTER

Volume of effluents			12 to 15 m3/day	0
Total nitrogen				1.7 2.2 t/day		0
Ammoniacal nitrogen			0.6 to 0.7		0
	
5.	Economics:  

	Cost of direct investment

	Annex hydrolyzing tank 		  360 000
	Civil engineering 			  360 000
	Tank, pumps, piping 		  520 000
	Instrumentation 			  360 000
	Analysis device 			  150 000
	Miscellaneous 				  250 000

	Total 					2 000 000	FF (1990)

6.	Advantages:  Total suppression of discharges.  Re-introduction of the effluents into the process.  
Recovery of nitrogen.

7.	Constraints:  Explosive nature of the ammonium nitrate in presence of the carbon impurities (amelites 
and amelines).  Take care that the cyanide acid content lower than 35 g/l is kept in the recirculated 
effluents in order to prevent its solidification in the pipes.

8.	Contacts:

		Agence de l'Eau Adour-Garonne
		M. GARIADOR
		TEL: 33 61.36.37.38

		M. GELBER
		Engineer, Security and Environment
		GRANDE PAROISSE S.A.
		Atelier Elf Atochem
		143 route d'Espagne
		BP 1166
		31036 TOULOUSE - France
		TEL: 33 62.11.45.00
		FAX: 33 62.11.45.20

	M. Maton
	M. Chatenet
	Office International de l'Eau
	Direction de la Formation et des Etudes
	rue Edouard Chamberland
	87065 Limoges Cedex, France
	TEL:  33  55114770
	FAX:  33  55777115

9.	Keywords:  France, ISIC 3512, chemical, recycling, acid, cyanide, urea, nitrogen

10.	This case study was submitted to UNEP IE in 1994 by the French Office International de l'Eau. It has 
not undergone a formal technical review.