|Home > NETT21 > Technologies for Resource/Energy Recovery from Sewage Sludge|
|Name of Technology||Methane Fermentation System of Sewage Sludge and Raw Garbage, and Carbonization-activation for Utilization|
|Technology Owner||Kawasaki Heavy Industries, Ltd.|
|General Description||This technology aims to achieve two goals:
- To make beneficial use of methane gas recovered via methane fermentation from a mixture of sewage sludge and organic waste, such as kitchen refuse, received from local communities, viewing a wastewater treatment plant as a facility for using local biomass; and
- To promote carbonization-activation and recycling of fermentation residue, or dewatered sludge.
This technology system integrates two processes, which are methane fermentation of sewage sludge-biomass mixture followed by power generation using the resultant biogas and carbonization-activation of fermentation residue.
The use of biomass is under assessment in Japan, but progress is slow regarding the use of wet biomass due to its high water content which accounts for a high weight percentage. Methane fermentation is attracting great interest as a low-cost means of recovering energy from wet biomass. However, one drawback of the process is the treatment cost for filtrate from the dewatering machine after fermentation. In this regard, a wastewater treatment plant has large wastewater treatment equipment and consumes electricity generated within the plant, and so is expected to be a useful facility for making use of wet biomass. Moreover, methane gas can be used as supplementary fuel for carbonization or carbonization-activation of residual dewatered sludge to promote recycling without consuming fossil fuel. Furthermore, in the case of receiving kitchen refuse included in general domestic waste, the refuse incineration plant can be downsized when rehabilitated.
|Components of Technology||The four major components of this technology are: (1) Pretreatment equipment, (2) Methane fermentation tank, (3) Biogas power generating equipment and (4) Carbonization-activation equipment.
These components have the following functions.
(1) Pretreatment equipment
Receives kitchen refuse and other biomass, removes foreign matter and solubilizes the biomass mixed with sewage sludge.
(2) Methane fermentation tank
Performs methane fermentation of the solubilized liquid and another portion of sewage sludge to produce biogas.
(3) Biogas power generator
Refines biogas, generates power by gas engine and supplies electricity to plant facilities.
(4) Carbonization-activation equipment
Dries dewatered digested sludge (dewatered sludge) and produces activated carbon.
Actual conditions may vary depending on the local situation. For example, the type of biomass that the plant can receive may vary or the plant may receive dewatered sludge from other plants for treatment. This technology allows for optimization, such as considering whether or not to incorporate every component or changing the capacity to reduce the final cost
Scopes of both technologies
The difference between Case 1 and Case 2 is whether the wastewater treatment plant has a digestion tank or not. In Case 1, assuming that the plant has no existing digestion tank, the project builds a compact horizontal methane fermentation tank, which is already used in some locations for treating livestock manure. Case 2 assumes that the wastewater treatment plant already has a digestion tank.
|Features of Technology||
This technology is designed to receive wet biomass including kitchen refuse, recover a larger quantity of methane gas and earn revenue from treatment. By producing valuable activated carbon from dewatered sludge without disposing of it as industrial waste and earning revenue from its sales, this technology substantially improves the economy of the overall system.
Schematic diagram of the technology
|Evaluation of Technology||
This technology was developed in the LOTUS Project (Lead to Outstanding technology for Utilization of Sludge Project) and evaluated and reviewed by the Sewerage Technology Development Project Committee under the Ministry of Land, Infrastructure and Transport in Japan in 2008.
Note: This technology was developed by Kawasaki Plant Systems, Ltd. and evaluated in 2008. Kawasaki Plant Systems, Ltd. has been consolidated into Kawasaki Heavy Industries Ltd. since 2010.
|Contact Information||Industrial Plant Sales Department (Chemical Plant), Plant & Infrastructure Company, Kawasaki Heavy Industries Ltd.
For inquiry: http://www.khi.co.jp/cgi-bin/other-q1_e.cgi?form-type=ind-plant&ca_no=30