For Sludge – Large Scale – Low Running Cost Composting Example￼
|Processed Material and Amount:||Sludge, 9,000 tons/year (maximum)|
|Overview:||Efficiently composts sludge discharged from a sugar factory. Operates with few personnel and few heavy machines by reducing heavy machinery work as much as possible. A facility with reduced running costs.|
Measures and Effects
|Expanding equipment:||New equipment was installed in order to compost and recycle 9,000 tons of sludge per year.|
|Reducing processing time:||It is expensive and time consuming to mix sludge and auxiliary materials with heavy machinery, so a mixing device was used to shorten the processing time and reduce running costs to one tenth of what it was before.|
|aising fermentation temperature through optimal aeration:||By combining high-pressure aeration with blowers, a fermentation temperature of 80˚ C or higher was achieved even in the cold Hokkaido winter.|
|Reducing auxiliary materials used:||Determined the appropriate mixing ratio for wood chips and return compost, as a way to reduce the cost of buying auxiliary materials.|
|Saving labor:||Succeeded in reducing operating costs including fuel costs by reducing turn over work with heavy machinery as much as possible.|
Hokkaido is a center for sugar production, making more than 80% of the sugar produced in Japan. However, recycling sludge discharged in the sugar production process is an issue.
This facility was built in order to efficiently compost sludge discharged by sugar factories, and recycle it for use in the local area as high quality fertilizer.
When composting sludge, the dehydrated cakes made in recent years contain polymer flocculant, so they are difficult to mix with auxiliary materials.
Especially when mixing with heavy machinery (shovel loaders), large chunks are formed. This causes problems such as anaerobic fermentation inside chunks, generating foul odors, and resulting in low quality finished fertilizer that cannot be distributed.
At this facility, we decided to eliminate preparation work using heavy machinery (mixing sludge with auxiliary materials), and mix mechanically with a mixing device.
This made it possible to mix materials uniformly in a much shorter time than with heavy machinery. As a result, it was possible to make the fermentation period shorter and save labor, thereby drastically reducing costs, and produce high quality compost.
By using a high pressure aeration system at the start of fermentation, turn over work can be reduced, realizing higher fermentation temperature and reduced foul odors.
By saving labor involved in turn over work, it reduced the number of machinery and operation personnel, as well as the running costs.
Two mixers (C-Mode) were introduced in order to treat a high volume of sludge.
This mixer only requires the operator to insert sludge as materials and auxiliary materials into the hopper. After that, it operates automatically from mixing to discharging, allowing the operator to do other work in between.
The operation status is displayed with rotating lights, so it can be checked from far away in the facility while still operating heavy machinery. This makes it possible to know the next time to input materials and do work smoothly.
Compared to mixing (preparation) work using heavy machinery, it is possible to reduce running costs by more than 90%, demonstrating tremendous benefits in reducing facility costs.
This is the compressor room, which supplies high pressure air. When doing fermentation of highly viscous materials including sludge, if blower aeration is done from the first stage of fermentation, then the temperature of materials cools down.
With the high pressure aeration system, clogging is reduced and the initial fermentation temperature rises very quickly.
By saving labor for turn over work, it also reduces the number of heavy machines and workers, effectively reducing initial investments and maintenance costs.
This is the initial fermentation period. Materials mixed with auxiliary materials are deposited in a high pressure aeration fermentation tank, and after 2 days, the temperature reached about 80˚ C.
It can operate without heating even in the harsh Hokkaido winter. After deposition into the primary fermentation tank for approximately 1 week, materials are moved to the blower fermentation tank.
Part of the fermented materials are shipped as compost, while most are used as return compost.
This is used to reduce the cost of buying auxiliary materials.