Focusing on the recycling of washing resources

Head of the Expert Group on Laundry and Dyeing Industry of China General Chamber of Commerce

Chief Engineer of China National Garment Group Corporation
Wen Lisheng

It is well known that since 1993, China's garment production and garment export earnings have both ranked first in the world, a status that continues to this day. What achievements have made this possible? First, the policy of reform and opening up; second, resource advantages. Looking back now, although we are a major garment manufacturing country, due to the lack of high technological content, absence of a clean production industrial structure, and no world-class brands of our own innovation, our garment manufacturing can only be at a mid-to-low level. Producing 100 million pairs of pants in exchange for one Boeing airplane is not something to be proud of, because what we export cheaply is not only pants but also the loss of resources and environment. The production of 100 million pairs of pants through textile printing and dyeing causes serious resource loss and environmental pollution. Therefore, future manufacturing development cannot follow this path. Developing a circular economy and new energy is the only choice and the only way for our economic development and environmental win-win.

Circular economy and knowledge economy are two major trends of economic globalization. Knowledge economy requires optimizing the allocation of intellectual resources as much as possible to replace natural resources; circular economy requires achieving natural resource recycling as much as possible in economic production through new knowledge and new technologies. On March 9, 2003, General Secretary Hu Jintao pointed out at the Central Population, Resources and Environment Work Symposium: "We must accelerate the transformation of the economic growth mode, integrate the development concept of circular economy into regional economic development, urban and rural construction, and product production, so that resources can be used most effectively." On March 10, 2004, Premier Wen Jiabao proposed: "Focus on saving and utilizing resources and vigorously develop the circular economy." This shows the importance and necessity of developing a circular economy in our country.

The term "circular economy" was mentioned by American economist K. Boulding in the 1960s when he proposed ecological economics. He was inspired by the then space shuttle launch to analyze the development of the earth's economy. He believed that the spaceship is a self-contained, isolated system that exists by continuously consuming its own resources and will eventually be exhausted and destroyed. The only way to extend its life is to achieve resource recycling within the spaceship, such as decomposing exhaled CO2 into oxygen, decomposing excreted nutrients for reuse, and minimizing waste discharge. This reveals the meaning of "recycling resources." Therefore, the circular economy can be said to be a large system involving humans, natural resources, and science and technology, continuously improving resource utilization efficiency throughout the entire process of resource input, enterprise production, product consumption, and waste disposal, transforming the traditional extensive linear economy dependent on net resource consumption into an intensive closed-loop economy based on the natural ecological cycle. Circular economy is the highest realm of efficient natural resource utilization.

Traditional economics treats natural ecosystems as both resource extraction sites and waste disposal sites, based on a linear economic model. For example, many industries and projects treat rivers as both "water supply pipes" and "sewers." In contrast, the circular economy is an ecological closed-loop economy that forms a reasonable closed cycle, conforming to the ecological food chain. The differences between the two are shown in the following figure:

The focus of the circular economy is on the efficient and even cyclical use of natural resources. Unlike traditional economics, it requires maximizing the optimization of natural resource allocation, maximizing the efficiency of natural resource use, and maximizing the benefits of natural resource utilization. Before the realization of the knowledge economy, the use of natural resources remained the decisive factor for economic development. The circular economy, starting from a large system analysis perspective, implements total quantity control and solves resource shortages through resource recycling, which is the best approach.

Regardless of the industry, whether manufacturing or service, enterprises must be guided by the concept of circular economy to achieve infinite resource recycling and reuse while developing the enterprise. In the laundry industry, the greatest natural resources used are laundry machinery, water resources, detergents, and auxiliaries. Research and practice on the recycling and reuse of these natural resources are what truly focus on the development of the circular economy and represent enterprises with sustainable development.

1. Recycling and reuse of laundry water

China is one of the countries severely lacking water resources. According to statistics, China's total water resources amount to 2.8 trillion cubic meters, with a per capita of 2200 cubic meters, which is one-fourth of the global per capita level. More than 600 cities nationwide suffer from water shortages, with an annual shortage of nearly 600 billion cubic meters. Water shortage causes an annual economic loss of 200 billion yuan and a grain production reduction of 70 to 80 billion jin, showing how important water conservation is. Developed countries have an industrial water reuse rate of 75%-85%, while our country's industrial water reuse rate is only 5%. Many industrial sectors only know how to use water but not reuse it, let alone recycle it. Currently, there are nearly 200,000 enterprises in China's laundry industry, with an annual water consumption of about 100 million cubic meters for water washing. Because so many enterprises have not realized the recycling and reuse of laundry water, laundry wastewater is directly discharged into municipal sewers, resulting in very low utilization. If through our research efforts, the recycling rate of laundry wastewater can reach 50%, then 50 million cubic meters of water can be saved annually, enough to provide daily living water for 400,000 people.

To achieve the recycling and reuse of laundry wastewater, it is necessary to install wastewater treatment equipment. This is feasible for large-scale and branded laundry enterprises, but difficult for many small enterprises with front shops and back factories located in towns. Numerous small enterprises in urban areas must form alliances to jointly build laundry wastewater treatment and recycling systems to achieve this.

Because a large amount of detergent and various auxiliaries are used when washing clothes, the laundry wastewater after washing contains dust, dirt, short fibers, animal and vegetable oils, alkaline detergent liquids, and various auxiliaries such as bactericides, preservatives, bleaching agents, softeners, and color fixatives residues, as well as some insoluble impurities. To achieve the recycling and reuse of this laundry wastewater, it must be treated. The process is as follows:

Physical and chemical treatment refers to the use of coagulation and sedimentation technology, membrane filtration technology, activated carbon adsorption technology, etc., while biochemical treatment technology uses microorganisms in water to adsorb and oxidatively decompose dissolved organic matter. Because laundry wastewater contains a large number of bacteria, disinfection and sterilization must be performed for recycled water, which can be done using chlorine-containing disinfectants.

Biological sludge and solid impurities generated during wastewater treatment must be further treated to avoid secondary pollution to the environment. There are specialized technologies and equipment for treating these materials (for example, biological sludge treatment technologies and equipment from Belgium's Siges company, Shanghai Shivei company, and Sea Lion Environmental Protection Technology company).

2. Recovery and recycling of tetrachloroethylene

Tetrachloroethylene (Tetrachloroethylene), also known as Perchloroethylene. Typically, trichloroethylene is used as the raw material, chlorinated to produce pentachloroethane, which then reacts with sodium hydroxide to generate tetrachloroethylene. After further purification and stabilization, the tetrachloroethylene product is made.

Tetrachloroethylene is a non-polar solvent, insoluble in water, but soluble in toluene acid, water-yang acid, and many organic substances such as fats, oils, and resins; it is miscible with various other organic solvents; however, it cannot dissolve sugars, glycerol, proteins, cheese, etc.; it has varying degrees of dissolving effects on rubber and plastics.

Tetrachloroethylene has relatively stable chemical properties. Without catalysts, air, or moisture, it remains stable below 500°C. In dark, light-free conditions, tetrachloroethylene is not affected by oxygen. Under ultraviolet light, tetrachloroethylene undergoes oxidative decomposition when exposed to air and oxygen. Prolonged contact with water causes slow decomposition producing trichloroethylene and hydrochloric acid.

Therefore, a certain amount of stabilizer is generally added to tetrachloroethylene to inhibit its decomposition, usually more than 0.01%. Treated tetrachloroethylene can operate stably under conditions of light, air, moisture, and contact with certain metals, with an operating temperature around 140°C.

Domestic and international dry cleaning industry practice has proven that using tetrachloroethylene as a dry cleaning agent results in clothing, fur, and fabrics that feel comfortable, soft, bright, do not fade, deform, or damage fibers after dry cleaning.

Currently, there are about 200,000 laundry enterprises in China. The annual consumption loss of tetrachloroethylene dry cleaning agent is about 10,000 tons. Losses occur due to evaporation and leakage during the washing process, as well as adsorption loss from residuals and short fibers on washed clothes. This has driven modern research and development to continuously improve the recovery rate of tetrachloroethylene. Standards require that the recovery rate of tetrachloroethylene in open-type dry cleaning machines be greater than 92%, and in fully automatic closed dry cleaning machines be greater than 97%. Modern fully automatic closed dry cleaning machines have evolved from the third and fourth generations to the fifth and sixth generations, focusing on tetrachloroethylene recovery rates. Through forced refrigeration, carbon adsorption, secondary carbon adsorption, and automatic detection and control of residual amounts inside the cage, recovery rates can now reach 99%, greatly extending the reuse lifespan and saving detergent resources. Solid residues containing tetrachloroethylene after dry cleaning must undergo environmentally friendly incineration and granulation treatment and must never be discarded casually to avoid environmental pollution.

3. Recovery and reuse cycle of washing machinery

Washing machinery equipment is one of the major resources of laundry enterprises. From the perspective of a circular economy, its development must differ from traditional washing machinery. As a product, efforts must be made to enable recovery and reuse cycles. To achieve recycling and reuse of washing machinery, its design and manufacturing must differ from traditional products and incorporate recycling and reuse design.

Of course, designing for product reuse does not mean completely overturning traditional product design. Traditional design is the foundation for reuse design. Reuse design supplements and improves traditional design. Only by adding environmental attributes as one of the design goals on top of the original design objectives can the designed product meet reuse performance requirements and maintain market competitiveness. A comparison between reuse design and traditional design is shown in the table:

It can be seen that reuse design is essentially an ecological design with several characteristics: ① Reuse design extends the product lifecycle. Traditional product lifecycle is from production to use, commonly called "cradle to grave," while reuse design extends the lifecycle to include post-use recovery, reuse, and disposal, i.e., "cradle to rebirth." ② Reuse design is a parallel, circular closed-loop design. Traditional design is a serial open-loop design, considering only design, manufacturing, and disposal stages, rarely addressing post-disposal recovery and treatment, thus an open loop. Reuse design includes all traditional stages plus disassembly, recovery, and treatment after disposal, achieving a closed-loop lifecycle, with some processes considered in parallel during design. ③ Reuse design fully analyzes and considers ecological environmental needs, reducing waste generation at the source, thus protecting the environment and maintaining ecosystem balance. ④ Reuse design ensures full and effective use of component materials, reducing demand for material resources and energy, preventing depletion of Earth's mineral wealth. ⑤ Reuse design eliminates waste generation at the source, minimizing waste quantity and greatly alleviating waste disposal conflicts.

The reuse design method for washing machinery products is based on traditional product design but includes ecological environment and resource recovery considerations at all design stages. For example, material guidelines for reuse design include: ① Use less scarce or rare raw materials, more waste, surplus, or recycled materials as raw materials. ② Minimize the variety of materials used to facilitate effective recovery after disposal. ③ Avoid materials that are difficult or impossible to recycle. ④ Use little or no toxic or harmful raw materials. ⑤ Prefer reusable or recyclable materials. Structural design guidelines for reuse design include: ⑴ Design structures to make products as small and refined as possible, saving resources. ⑵ Minimize the number of components, facilitating assembly, disassembly, reassembly, maintenance, and disposal after scrapping. ⑶ Modularize product functions to aid assembly, disassembly, and recovery. ⑷ Ensure reasonable durability and service life. ⑸ Emphasize variety and serialization in product structure. ⑹ Simplify disassembly processes, use easy-to-disassemble connections, reduce fasteners, and avoid destructive disassembly methods. ⑺ Use simplified packaging that is reusable or easy to recycle.

Recyclable design typically uses a modular design approach. Modular design means dividing and designing a series of functional modules based on analyzing different functions or the same function with different performances and specifications within a certain scope; by selecting and combining modules, different products can be formed to meet various market needs. Modular design effectively resolves the conflict between product variety, specifications, design and manufacturing cycles, and production costs. It facilitates rapid product updates, improves product quality, eases maintenance, aids disassembly and recycling after product disposal, and enhances market competitiveness. Do not confuse modular design in recyclable design with common combined machine tools, series general-purpose designs, or building-block style mechanical designs. Here, a module's function is not necessarily a single component; modules with the same function can be used in base models, variants, or even across series and product categories. Modular design in recyclable design aims to make functional units into smaller standard modules and standardize the connection methods and structural elements between directly related modules to facilitate assembly, disassembly, and interchangeability. Modular design is economically suitable for multi-variety small batch production, especially designs with detachable structures.

The modular design process critically involves determining, selecting, and combining product functional modules based on user requirements. For example, the modular design of dry cleaning machines in laundry equipment can be divided into washing function device modules (inner and outer cages and their transmission structures), solvent supply device modules, solvent recovery device modules, electronic control system modules, pneumatic system control modules, and frame panel device modules; the modular design of garment pressing machines can be divided into steam generator and control system modules, air heater and control system modules, pressing mannequin device modules, and cabinet device modules. With modules, the use and disposal of laundry machines include a process of mechanical resource recycling that meets environmental and ecological requirements, making the service life of laundry machines, in a sense, "infinite" and long-lasting.

The Dutch company Goudkuil is the world's earliest and largest second-hand laundry equipment company. Their motto is "Our work is not just spraying paint — it is genuine remanufacturing!" This shows that their remanufacturing is true recycling and reuse, a typical example of resource circulation and conservation.

Goudkuil's remanufactured products range from 15-kilogram washing and spin-drying machines to tunnel washers with a capacity of 1600 kilograms of laundry per hour. Later, they included dryers, flat irons, and other types of dry cleaning machines in their remanufacturing projects.

The second-hand machines sold by Goudkuil have undergone genuine "remanufacturing." The first stage of remanufacturing is to completely disassemble the entire machine and carefully inspect each modular component. Then, all unusable parts are replaced with new ones, and known defects are modified. At this stage, before final assembly, remanufacturing is carried out according to all special user requirements. Electrical systems are entirely replaced with modern PLCs and microprocessors. After completing this stage and painting, the machines undergo actual operational testing by engineers before shipment. Goudkuil's warehouse, covering more than 20,000 square meters, stores various models of laundry equipment you may need. Where there are remanufactured products, there is remanufacturing manufacturing, and resource recycling can be experienced here.

To date, no company in our industry matches Goudkuil as a full-industry resource recycling company. I believe that with the development of the circular economy in our country, the inconspicuous laundry industry will surely embark on the path of resource recycling and reuse.

2007-1-29