Analysis of Screen Printing and Environmental Protection (2)

3.2 Acid, alkaline chemical exhaust

Printed circuit board cleaning, hole metallization, electroplating, etching, “wet film” development peeling, screen cleaning, etc. discharge a large amount of acid and alkali exhaust gas at the same time as the discharge of waste water, in the production line with horizontal operation The side-suction type gas collection pipe is provided with suction exhaust gas, and the treatment effect is obvious, which can effectively reduce the dissipation of acid and alkali waste gas. For the operation in the vertical mode, the same hood as the organic exhaust gas is usually collected to collect the acid and alkali exhaust gas, but the position of the hood device is often set too far or unreasonable from the operation tank, and the suction force trapping speed is insufficiently designed. , resulting in poor gas collection. Therefore, adjust the hood or suction outlet to a suitable position and maintain a certain suction speed. For gas pollution such as pickling tanks and other low-speed emissions, it is recommended that the pumping speed be 0.5 to lm/s to effectively eliminate the acid and alkali exhaust gas emitted during the operation.

At present, most factories use the packed scrubbers for the treatment of acid and alkali chemical waste gas. In order to save equipment investment costs and reduce the occupied space, most of the plants use acid and alkali gases to be introduced into the same scrubber tower at the same time. However, the acid and alkali gases will produce a chemical neutralization reaction and produce fine salt compounds. However, the scrubbing towers have a limited effect on the removal of salt particles. As a result, some salt particles are still released to the atmosphere with the smoke in the scrubber. In the production of white smoke. Therefore, the acid and alkali waste gas should be treated separately so as to effectively treat the exhaust gas and achieve emission standards.

At present, most small and medium-sized factories only set several vertical exhaust fans on the walls of the room to pump acid and alkali waste gas, which often results in poor suction performance. Indoor exhaust gas content is high and the ambient air quality is low.

3.3 Dust emissions

The dust exhaust gas is mainly concentrated on the copper-foil board blanking, drilling, deburring, and edge forming and other processes. The main components of dust are the powders of glass fiber cloth, epoxy resin and phenolic resin that make up the copper-clad board material. Inhalation will cause silicosis. Allergic reactions, itching and redness and ulceration will occur after contact with the skin, impairing the health of the operating staff.

The majority of dust exhaust gas treatment is handled by baghouse dust collectors, but also by suction suction manifold or centralized suction, but some factories lack the correct concept of operation and maintenance, and no differential pressure monitor monitoring equipment is installed. The collection effect is usually also unable to record the change of operating pressure loss, and can not find the abnormality of the dust collection system in time. At the same time, due to the low suction air pressure of the air compressor system, the amount of secondary air carried is insufficient to install the filter. The dust cake on the cloth shakes down and causes clogging, which reduces the dust collection effect. Therefore, it is necessary to incorporate the operational requirements and maintenance methods into the guideline for the operation, and to check regularly or frequently to ensure the effect of the dust collector.

For manual drilling or manual milling operations, some small and medium-sized factories have not adopted centralized suction of the gas gathering pipe. Instead, they use ordinary electric fan suction and set up a direct-ventilation fan suction on the wall, although the operation station is The dust exhaust gas has been reduced, but it has caused dust in the entire operation room to fly. This has the opposite effect.

4. Waste reduction measures

Due to the complexity of the screen printing process in the printed circuit manufacturing industry and the wide variety and large amount of printing materials, pollution emissions will inevitably increase. In the future, under the premise of not affecting product quality or increasing costs, pollution should be reduced and processing costs should be reduced.

4.1 It is advisable to develop materials and process technologies and equipment that have low pollution emission characteristics or that are easy to control and treat, and recycle organic solvents and hazardous chemicals so that it is economical and conducive to environmental protection.

Use non-silver salt photosensitive film, such as using diazo photosensitive film instead of silver salt film; special cleaning agent should be used for screen cleaning.

Using an alkali-soluble printing material, the ink printing material is removed using a dilute alkaline solution of sodium hydroxide or potassium hydroxide without using a solvent.

Promote the use of non-solvent photo-curable various types of inks. Because of the flammability, volatility and toxicity of solvents, it is most likely to cause severe air pollution.

4.2 The type and procedure of the fixed ink printing materials. During the operation, the printing ink and the solvent should be sealed and capped after being used or properly stored and managed. Otherwise, the solvent will not easily volatilize, which will not only make the ink dry, but also cause the ink to dry. Improper discharge of pollutants.

4.3 Ink Division should be sealed and stored in a cool dark place, to maintain the indoor environment temperature. Strengthen the management of inventory materials in the warehouse and track records, and regularly perform inspections. This can not only effectively control and use the inventory of materials and to avoid excessive use of materials, failure and scrap, can also reduce the evaporation loss of unnecessary organic solvents and waste gas.

4.4 For some work areas with poor gas collection effect, the work area should be isolated or sealed with a rubber curtain to improve the gas collection effect and reduce the diffusion of exhaust gas.

4.5 Promote the recycling and recycling of organic solvents to reduce the pollution caused by discarded waste solvents on the surrounding environment, and reduce the consumption and save the production cost.

4.6 Strengthen the maintenance and management of environmental treatment equipment and gas gathering pipelines so that the equipment operates normally to reduce the escape of exhaust gas and ensure the efficiency of treatment.

4.7 Raise the awareness of environmental protection workers and organize the training and education of environmental protection knowledge so that operators can understand in detail the types and sources of air pollutants in process operations and their impact on environmental quality and employees' own health.

5. Clean manufacturing

Cleaner production is the increasing scale of industrial scale in the world, resulting in the rapid depletion of resources and ecological destruction, and it has been proposed in the context of simply relying on end-of-pipe management to effectively prevent pollution. In the past, for a long period of time, there were many drawbacks to putting pollution control at the disposal of the end, such as the expansion of infrastructure investment, high operating costs, and secondary pollution caused by residual pollutants. Years of practice have proved that the economic burden caused by this path is very heavy and it is difficult for enterprises to bear. Enterprises regard economic efficiency as the most important pursuit goal, and end governance is in essence contradicting this goal. This contradiction is the reason why environmental protection and production have always been difficult to combine and coordinate.

Unlike clean-end production, end-of-pipe cleanup usually solves pollution problems in the pursuit of economic efficiency. It requires efficiency, energy conservation, consumption reduction, and pollution reduction in the production process, so as to prevent and reduce pollution at the source and bring economic and environmental benefits to the company.

5.1 Meaning of Cleaner Production

5.1.1 For the production process, it is required to save raw materials and energy, eliminate toxic raw materials and reduce the pollution degree of raw materials to the environment, and reduce the generation of various wastes and waste gas emissions and toxicity.
5.1.2 For the product, the requirements from raw materials to final disposal, that is, the reduction of the impact on the environment and human health during the entire production period of the product are required. 5.2 Clean Production Content
Cleaner production includes:
Clean energy;
Clean production process;
Clean product.

For the screen printing industry, it is mainly a clean production process that develops, develops, and uses various types of plate-making materials and ink printing materials that have low pollution emissions or are easy to control and treat, and recycles and recycles organic solvents and special cleaning agents. The development of advanced application technology and equipment, as well as waste gas and wastewater treatment processes, will reduce the generation of harmful substances from the source to reduce pollution. At present, China is beginning to implement a series of standards for the implementation of ISO14000 environmental management, which will help to achieve cleaner production and achieve environmental protection goals.

Author: Jiangxi printing and Yehong Xun source of environmental protection: "Printed Circuit & Place"

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