Objective
Purification and upgrading of landfill gas up to natural gas quality on an economic basis, bringing the CH4 content from approx. 55% up to approx. 87,5%
At nominal capacity, the plant will produce 735 m3/h PNG (pseudo-natural gas) from 1200 m3/h landfill gas. The PNG is fed into the natural gas grid.
The Carbio plant has come into operation July 1990. The start-up has known a lot of problems, both technical problems with the installation itself as well problems with the supply of landfill gas. For both reasons the up-time of the factory was low. (approx. 50%). Due to lower landfill gas supply than forecasted the production of PNG during operation was also less than expected. In 1990 559310 m3 PNG was delivered to NRE. The production in 1991 was 3466658 m3. The expectation is that the factory will produce approx. 5 to 6 million m3 PNG per annum. Evaluation of the performance of the factory shows that the design goals are reached for the greater part. Only the expected removal of N2 in the PSA process is much less than calculated. Some important problems met during the starting period :
- The sensitiveness of the system for extreme temperatures i.e. temp. under 0 deg. C and above 30 deg. C. The problems are solved with extra insulation of vessels and piping while in addition to that more heattracing is build in.
- The landfill gas contains more contaminating components than the original analysis of the gas indicated. With the moisture in the gas also a part of the pollution enters the purification process. The unexpected parts gave rise to extra pollution of the carbon sieves and unexpected wear of valves. Solutions are found by adding filters and use valves which can stand the more aggressive environment.
- Difficulties with the tuning of the PSA control system.
Due to higher operating costs (more supervision) and a higher investment level (see above) the economics of the operation is somewhat less than estimated. Now a production of some 600 to 700 m3/h PNG is needed for being profitable, whilst 500 m3/h was estimated to be sufficient.
The estimated payback time for a replication of the project amounts to 4,7 years. Several offers are made for delivery of installations of this kind by CIRMAC BV.
The system of upgrading landfill gas up to PNG is based on a technique of separation of different gas components by adsorption on carbon molecular sieves.
The system is discontinuous. The regeneration of the CMS is accomplished just by depressurization, without a secondary medium. Because of this process characteristic the system is called PRESSURE SWING ADSORPTION SYSTEM.
Bergbau-Forschung GmbH in Essen, B.R.D. invested much efforts in this process and developed a working system for purification and upgrading landfill and equivalent gases. The purification is done in several steps:
- Drying of the landfill gas is executed by cooling the gas to 5 deg. C and catching the moisture with help of demisters. Together with the moisture a lot of (chemical) pollutions are removed.
- The H2S is removed from the gas via carbon sieves impregnated with Potassium-Iodide. The Sulfur is kept by the carbon. Depending of the amount of H2S in the landfill gas the contaminated carbon has to be replaced.
- The removal of the halogenated hydrocarbons (HHC) is executed with the help of activated carbon. The heavy HHC molecules are catched by the activated carbon while the light gas molecules pass the activated carbon. The contaminated can be cleaned via a regeneration process that removes the compiled HHC components.
Many of the used techniques and methods are patented by Bergbau-Forschung.
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
8500 AD Journe
Netherlands