| Reducing waste in polyester production | Indonesia |
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Full scale |
MANUFACTURE OF CHEMICALS AND CHEMICAL PRODUCTS # 19
Background:
Synthetic fiber (polyester) plays an important role in the textile industry in Indonesia. The first step in polyester production is the production of chips through a polymerization process in which raw materials -including ethylene glycol, terephtalic acid, additives and a catalyst - are combined. This process produces two types of wastes (i) liquid waste that is treated in the wastewater treatment plant and (ii) solid waste, known as RG-Residue. Before the implementation of cleaner production technologies, in this sector the RG-Residues was disposed by incineration.
The present case study was implemented in one such polyester producing company viz., P.T.TIFICO. This company was founded in 1973 with two shareholders, Teijin Ltd and Toyo Menka Kaisha (Japan); the company went public in 1980. P.T.TIFICO consists of 14 departments, including one dedicated to safety and environmental concerns. The company produces staple fiber and filament yarn polyester. Seven boilers provide power for the process of polyester production at P.T. TIFICO. Of these, three use heat recovered from the diesel engines, two industrial diesel oil, one natural gas and one diesel fuel.
Cleaner Production Principle:
Recovery, reuse and recycle; Process Modification.
Cleaner Production Application:
Cleaner production initiatives at P.T.TIFICO included
| the reuse of RG-Residue, |
| industrial water recirculation |
| substitution of industrial diesel oil with natural gas and |
| heat recovery. |
These cleaner production initiatives described in greater detail below, have increased process efficiency.
Reuse of RG-Residue: The RG-Residue was previously disposed of in an incinerator with a 1.5 ton/day capacity. This process was costly and produced substantial air pollution. It was therefore decided to evaluate the reuse of RG-Residue as an additive in the production of carpet sheet for roofing. The additive was found to improve the characteristics of the carpet sheet, and incineration was stopped. This reduced air pollution substantially and produced economies in savings on incinerator fuel, which decreased production costs. The plant produces about 35 tons a month of RG-Residue but since demand exceeds production there are no storage problems.
Industrial water recycling: In the wastewater treatment plant, liquid wastes are treated by activated sludge. Before treatment, chemical oxygen demand (COD) levels were 10,000-12,000 parts permillion (ppm). Following treatment, COD levels were reduced to 20-40 ppm, a level which easily meets the government standard for wastewater of 200 ppm (class II). Approximately 32 per cent of the wastewater is now reused in the process, reducing the need for fresh water by about 2450 liters/minute.
Natural gas utilization: One boiler running off industrial diesel fuel oil was converted to run off natural gas, reducing air pollution and energy costs.
Exhaust gas recovery: Waste heat from the diesel engine is used to produce 12 tons of steam /hour.
Environmental and Economic Benefits:
The project benefits include,
| Reduced air pollution and produced economies in savings on incinerator fuel due to reuse of RG-Residue: |
| Reduced air pollution and energy costs due to utilization of natural gas. |
| Reduction of pollution load due to industrial water recycling. Before treatment, chemical oxygen demand (COD) levels were 10 000-12 000 parts permillion (ppm) which reduced to 20-40 ppm after treatment. |
| Approximately 32 per cent of the wastewater is now reused in the process, reducing the need for fresh water by about 2450 liters/minute. |
| Waste heat from the diesel engine is used to produce 12 tons/hour of steam. |
Cost savings are as follows:
| Natural gas utilization: | |
| Net savings | 387 000 US$/year |
| Capital investment | 637 700 US$ |
| Payback period | 1.7 years |
| Industrial water recycling: | |
| Net savings | 53 408 US$/year |
| Capital investment | 12 074 US$ |
| Payback period | 3 months |
| Exhaust gas boiler: | |
| Net savings | 601 843 US$/year |
| Capital investment | 1 105 990 US$ |
| Payback period | 1.84 years |
| Reuse of RG-Residue: | |
| Energy savings | 390 US$/year |
| Labor savings | 1 100 US$/year |
| Sales of wastes | 5 530 US$/year |
| Total savings from reuse of RG residue | 7 020 US$/year |
Constraints:
None reported.
Contacts:
Review Status:
This case study was originally published in the UNEP IE document "Cleaner Production in the ASIA and Pacific Economic Corporation (APEC) Region. In the process of preparing the document the case study underwent a technical review. Subsequently in September 1998, Dr. Prasad Modak conducted a technical review of this case study.