Clean-up of sulphur plant tall gas is now a part of the costs of oil and gas production. The Sulfreen Process has been developed by the Aquitaine Group with two main purposes: efficiency and low cost. It is now the cheapest of the proven processes but cannot guarantee a return of the investment.
The cost of the environmental requirements remains high for the producers and is an additional charge in the oil and gas business.
With the increasing prices of the foreign energy resources and the more and more expensive prospecting work in the politically stable areas, the ecological constraints and the attendant costs are often viewed as part of the price of finding oil or gas.
However, when the industrial companies are under the obligation to add new facilities to improve the performance of the existing sulphur recovery units with no guarantee of a return of their investments, they naturally are anxious to find the cheapest way to comply with the required levels.
This paper presents the history of the research of the Aquitaine Group for the reduction of sulphur emission in the last fifteen years. Though higher efficiencies can be obtained with more expensive processes, the Sulfreen is a satisfactory compromise to get the required sulphur recovery with the minimum cost. From the results of existing units we have determined the tribute to the ecology which has to be paid by the oil and gas producers.
With more than 5000 LTD of sulphur, SNPA in Lacq has been the world's largest sulphur producer from natural gas sources. Since the plant was located in a populated area, the reduction of the sulphur dioxide emission was commenced early in the year 1960 though governmental regulations were notestablished yet. People and livestock were incentiveenough to try to improve the sulphur recovery. It became evident quickly, that the incremental recovered sulphur would be very expensive using the traditional CLAUS process. The first idea was to research a way to produce a downstream product which would give an extra-value to the sulphur to insure a minimum return on the investment of a tail gas unit. The fluctuating sulphur market made this impractical.
Jointly with the Danish company TOPSOE, SNJPA developed a process for the production of sulphuric acid from all the sulphur tail gas components of a CLAUS unit. This process has been highly efficient. A 99% overall recovery was achieved regardless of the H2S/SO2 ratio or COS and CO2 content in the tail gas. But, due to the large volume of gas, other than sulphur components, it required huge vessels rind piping. The specific technology of sulphuric acid was difficult to apply and the maintenance costs were significantly in excess of the expected ones.
For a 1100 LTD sulphur unit, the sulphuric acid tail gas unit had a 10 million capital cost and 800,000 S/year operating and maintenance costs.