HOW WE STARTED
Sable Chemical Industries Limited (“Sable Chemical” or “Sable”) is the sole manufacturer of Ammonium Nitrate (“AN”) fertilizer in Zimbabwe and one of a handful across Africa. Sable Chemical commenced operations in 1969. At inception, Sable wholly imported its ammonia requirements through Maputo, Mozambique. The imported ammonia was the nutilized as the feed stock to produce AN fertilizer at its Kwekwe factory site.
COMMISSIONING OF THE ELECTROLYSIS PLANT
Taking advantage of the then low costand abundant source of energy from Kariba Dam, the company established an electrolysis plant in 1972, to produce hydrogen for ammonia production on site, catering for up to 70% of Sable’s ammonia requirements at its peak. The plant in itself was unique and ground breaking in many respects and was for many years the largest electrolysis plant in the world.
The development of Sable Chemical played a key catalytic role in the development of Zimbabwe’s agricultural and mining sectors leading to Zimbabwe’s so called ‘Green Revolution’ in the 1970’s and contributing significantly to the country resulting in it being termed the “Bread Basket of Africa.”
Zimbabwe’s agricultural sector has been in a state of transition over the past two decades which has seen new agricultural concepts being developed. However, agriculture still plays a pivotal role in Zimbabwe’s economy providing a source of livelihood for approximately 70% of the population.
To manufacture Ammonium Nitrate fertilizer, Sable historically utilized two plant clusters in an integrated configuration. The first plant cluster in the configuration was an electrolysis plant together with air separation and ammonia synthesis plants that were utilized to produce ammonia gas. The ammonia gas was then fed into the second plant cluster to produce Ammonium Nitrate as end product. This setup had the capacity to produce up to 72600 tonnes of ammonia, or at least 63% of the 115 000 tonnes of ammonia required to produce 240000 tonnes of AN per annum. The balance of 42400 tonnes of ammonia was imported.The production of ammonia gas using the electrolysis-based process was energy intensive requiring the utilization of ~ 105MW of electricity at its peak with 14 Electrolytes. An additional 10MW were required for the rest of the plants, making 115MW the total requirement for the entire facility.
Decommissioning of the Ammonia Making Plants
A persistent energy deficit and escalating tariffs prompted a decision to decommission the ammonia producing plants (being the electrolysis, air separation and ammonia synthesis plants) in October 2015. As a result of this, Sable now imports its entire ammoniagas feedstock requirements by rail from South Africa. The revised plant configuration hasresulted inthe company reducing its electricity consumption level from around 115MW to about 10MW.