Case study in Alcohol Processing
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1. Type
Case study
2. Industry Sector
Alcohol industry
3. General description of the industry
The alcohol industry is known as an important raw material industry which provides products for chemical, food and pharmaceutical industry as well as commodity field. But it has also its negative sites: the high consumption rate of water and energy, the production of several organic pollutants which cause serious contamination…
Cleaner Production is a useful method to reduce pollution already during production.
4. The alcohol industry in China and its problems
In the last years the alcohol industry in China grew rapidly. Reasons are the growth oft the population and the bloom of economy. Today we find more than 900 companies in the country; most of them are small-scale ones with scarce technologies.
The alcohol industry represents the largest pollution source of brewage industry in China. It notes the largest discharge of wastewater (10% of the total industrial rate) and because of old and lacking technologies the consumption of energy is extremely high. To produce one ton of alcohol 700-1000 kg of coal are needed (in developed countries: just 600-700 kg).
The most commonly used material for the alcohol production is yam (60%), followed by maize (20%) and sugar (20%). The utilization of raw material can reach more than 90% with advanced technologies in developed countries while in China just values around 50% are common.
Furthermore the industry is one of the largest pollutants sources. The amounts of produced BOD and COD during production are 1.15 million tons respectively 2.2 million tons which represents 18% and 12.5% of the total industrial discharge.
Different technologies of CP are known and also implemented in China since 1990 and improvements in pollution mitigation and several benefits on social, economic and environmental aspects were obtained, but there are still more effective CP systems needed. There is still a lack of implementation and optimization of CP technologies- a factor which has to be changed.
5. Description of the study factory
The CP assessment study was carried out in one of the oldest companies in China with 1500 workers including 260 technicians. The production of tipple is 50.000 tons per year and the factory has a production capacity of alcohol of 10.000 tons. The used raw material is dry.
Figure 1: Flow diagram of the principle procedures
Objectives of the study:
- to propose a series of optimized options of cleaner production system for alcohol production;
- to apply the proposed options for a realworld case, which will be targeted on the
Alcohol Factory;
- to assess the proposed options by evaluating their effects on water
saving and waste reduction; and
- to identify the optimum cleaner production system which will be recommended for implementation in the alcohol industry in China.
6. Planning and organisation
Analysis of waste generation and discharge
103 tons of water is consumed for the production of one ton of alcohol. The generated wastewater (55.8 * 10^4 ton) are discharged to a river within vicinity. Concurrently other liquid wastes such as alcohol lees are generated. After discharging the digestive juice of methane to the river, the left alcohol lees are further extracted. The solid part is then sold as fertilizer; the liquid phase is later reused in methane pool. The COD concentration in the alcohol lees liquid is very high and could reach values up to 3.8*10^4 mg/l. After simple treatments the wastewater is discharged directly into ambient bodies. Approximately 2.900 tons of slag are generated annually which is sold to local brickyards. The generated cullet is given to glassworkers for reuse. The emitted waste gas is discharged through chimneys after its treatment by cyclone dust extractor and water film dust extractor. Cleaner production options
Five different technologies were screened for designing the CP options:
- Good operating practices/housekeeping
Efficiency improvements and good management practices can lead to a minimization of waste and emissions. The implementation is possible in most areas and requires relatively low costs.
- Raw materials improvements
It refers to the reduction or elimination of hazardous materials like using maize as raw material instead of yam.
- Technology modification
Changes in the processes and/or the equipment are necessary to minimize waste and emission generation. The costs can range from small options to high options with high investment costs. An example would be the optimization of process conditions such as temperatures to save resources and energy.
- Product changes
It refers to modify quality standards, product composition etc.
- Reuse/recycling
The return of waste material to the process as a substitute for another input material is another option of CP.
After screening four CP options for alcohol production were suggested:
- 1. Fermenting with thick wort
This option should be combined with other CP techniques like reformation of raw material comminuted system or reconstruction of two level cooling systems. It just needs the modification of the worts concentration and the wanted microzyme to endure thick word has to be choosen.
- 2. Reusing CO2
CO2 is released to the ambient atmosphere and is known to cause climate changes. To reuse CO2 means to produce commercial products like gas, solid or liquid and to sell them on the market instead of discharging.
- 3. Reconstruction of distillation system
The option belongs to the final stage of production. Generally two-tower half distillation under normal pressure is common for the alcohol production. But therefore large amounts of steam and cooling water are required. As an alternative a multi-towers distillation under different pressures is used. In the factory a four- tower concept was realized. The evaporation point is changed and the waste heat can be used in the procedure. Furthermore cooling water and steam is spared; this leads to less waste generation. It is not an independent option and has to be combined with other techniques such as the reuse of waste heat of the lees liquid, automatic control by computer or the training of workers.
- 4. Producing organic feritlizer and methane with alcohol lees liquid
The leed liquid needs treatment before it is discharged. It can be seen as a renewable source which can be used for the production of methane and organic fertilizer. Economical benefits can be obtained by selling it. COD and BOD can be removed easily and impacts to the environment can be minimized or avoided.
7. Evaluation of Cleaner Production
- 1. Fermenting with thick wort
Large quantities of water are required for separation of the lees. The available techniques are already mature and technically sound. No additional workers are required and there is no impact of the products quality. Frequently it can be operated with the existing equipment, so no further investment costs are necessary. The implementation is very easy and leads to higher ratio of equipment use and an increasing of the amount of final products. Furthermore the transforming period is relatively short.
Savings:
- 53 tons of water per day
- 18% reduction of steam consumption
- Discharge of pollutants decreases (25%)
- Amount of generated waste lees liquid is reduced by 50%
- Pollution problems can be controlled
- 2. Reusing of CO2
More than 2.000 ton per year of CO2 can be saved by reusing it. Concurrently the utilization of raw material increases by 20%. But the implementation shows also some difficulties: new equipment is required and trainings and seminars for workers are also needful.
- 3. Reconstruction of distillation system
It represents a new trend of the technical evolution. It has low technical requirement for the implementation and can increase the efficiency of the use of heat energy. The product quality can be improved and the generation of waste lees liquid can be lowered which has positive effects on the environment. Savings can be made in the consumption of steam and cooling water (30%) and furthermore in the discharge of wastewater, waste gas and boiler dregs.
- 4. Producing organic fertilizer and methane with alcohol lees liquid
This kind of option is a practical and very attractive technology. The digest liquid from the first step of the methane production is used for the production of fertilizer by aerobic biochemistry, in total 5.500 tons per year.
Savings:
- 6.000 tons of lees liquid can be reclaimed
- 15.000 tons of coal is saved per year
- The discharge of BOD and COD during the methane production can be reduced by 80%.
8. Economic benefits
In this part of the study different parameters of the CP options such as gross investment, increased cash flow and cost saving during the production are compared. It turned out that the gross investment and the rate of return are the most critical factors, because they have a strong affect on the managers of the companies and their decision to implement CP options or not.
Option 4 (Producing organic fertilizer and methane with alcohol lees liquid) has the highest operation costs savings and net present value while having also the highest gross investment costs and a very low inner rate of return on investment.
Option 2 (Reusing CO2) is better than option 1 and option 3 in economic aspects but it has the disadvantage of relatively high investment cost (new equipment, trainings for workers).
Option 1 (Fermenting with thick wort) and option 3 (Reconstruction of distillation system) have similar profiles for all factors but option 1 has higher investment costs and lower net present value.
9. Implementation
- Integrated assessment
All options can be easily implemented and operated and all of them appeared to be environmentally friendly because of a reduction of pollutant discharge. Nevertheless option 2 is not recommended for implementation because of the high investment costs and the stagnate market of CO2 and the decreasing benefits from its sale. In the company the options 1, 3 and 4 are combined in a CP system. With systems more benefits can be reached than with individual option implementation. Examples for benefits are the saving of water and energy and the reduction of waste. Option 2 is still available for future response and can be integrated after earning more benefits through the existing system.
- Effects of implementation
The plan was divided into two stages. The first stage was the implementations of the systems while the second stage deals with the utilization of the benefits for the implementation of option 2.
10. Results
After four years all debts were paid and the collected data show that the discharge of wastewater and COD per ton alcohol and the consumption of water and coal are lower than the planned values. The quality of the environment in surrounding has been improved by reduced amount of generated waste.
Reference: Guoa, H.C., Chen, B., Yuc, X.L., Huangb, G.H., Liud, L., Nieb, X.H.: Assessment of cleaner production options for alcohol industry of China: a study in the Shouguang Alcohol Fact ory, published in the Journal of Cleaner Production (14), 2006
