What achievements have been made in the flue gas treatment of the setting machine? What problems still exist? What is the technical direction of the flue gas treatment of the setting machine?
The problem of environmental pollution caused by the exhaust gas of the setting machine has attracted people's attention. In recent years, in some cities along the southeast coast of China, the special treatment of printing and dyeing machine smoke has achieved certain results.
Taking Shaoxing County of Zhejiang Province as an example, the county has been promoting the "dyeing and finishing revolution" since 2006, organizing and carrying out a special remediation action called "blue sky action" for the exhaust gas of the finalizing machine in the printing and dyeing industry, so as to realize a major transition from "water control" to "gas control". The action requires that the waste gas purification device installed by dyeing and finishing enterprises must comply with the specifications and inspection standards of environmental protection, quality supervision, safety supervision and other departments, with the waste gas collection rate of more than 90%, the total particulate matter removal rate of 80%, and the oil fume removal rate of 75%. Moreover, the waste water and waste oil after purification shall be subject to the prevention and control of secondary pollution. Up to now, the finalizing machines in the county have been basically installed with waste gas purification devices, and the regional atmospheric environment quality has been significantly improved.
The special treatment of the exhaust gas of the finalizing machine has achieved certain results. Because of the supporting foreign heat recovery and flue gas treatment equipment, there are some disadvantages such as high price and inconvenient maintenance; Most enterprises adopt domestic self-developed treatment methods, including single processes such as mechanical purification, wet washing, electrostatic capture and incineration purification, combined processes such as water / gas heat recovery electrostatic precipitation and gas / gas heat recovery spray washing.
Compared with the technical requirements of "effective recovery of heat energy, up to standard emission of flue gas, stable and reliable operation", the existing exhaust gas treatment project of finalizing machine has some problems, such as low efficiency of flue gas purification, huge potential of heat recovery, hidden danger of fire accidents, etc. In addition, due to the lack of relevant emission standards and corresponding detection methods, it is difficult to effectively implement the environmental supervision of flue gas emission of finalizer.
Safe production and stable operation
In the process design and equipment modeling of exhaust gas treatment of finalizing machine, safety factors shall be fully considered to prevent the occurrence of fire and explosion accidents from the source, and long-term stable operation of the equipment shall be fully emphasized.
When the dyeing and finishing machine processes the inflammable textiles under high temperature conditions, there is a certain fire risk in itself. The waste gas contains a large number of flammable oil mist particles and fiber particles, which are easy to deposit in the transmission pipeline and purification equipment and block the air flow. When the electrostatic dust removal technology is used for waste gas purification, the oil fume particles deposit on the electrode and become oil dirt, which may lead to the phenomenon of "ignition" and fire accidents due to the uneven electrostatic field.
There are also hidden dangers in the exhaust gas purification equipment of the setting machine to varying degrees. Due to the untimely cleaning of the filter screen, the obstruction of the oil dirt condensation pipeline, and the static ignition, fire and explosion accidents occur frequently due to the overheating of the setting machine. In addition, the exhaust gas of the setting machine contains high humidity, and the moisture condenses on the high-voltage insulator, resulting in the failure of the electrostatic field due to the phenomenon of "creepage", which also affects the normal operation of the equipment.
Factors such as nonstandard equipment manufacturing and installation, untimely maintenance, lack of strict training for operators, lack of safety awareness and failure to implement enterprise operation management responsibilities all affect the operation effect of waste gas treatment equipment.
From the domestic and international development of green dyeing and finishing technology achievements and experience, dyeing and finishing set machine flue gas treatment technology has the following four obvious development trends.
Heat energy utilization and oil recovery
The utilization of heat energy and the recovery of oil and fat in the waste gas treatment project of setting machine can produce significant economic benefits, which is the driving force for enterprises to turn "passive" into "active" and carry out the waste gas treatment of setting machine.
Heat utilization. Setting machine is a key energy consumption equipment, its energy consumption usually accounts for more than 40% of the total energy consumption of dyeing and finishing enterprises, which is an important part of energy conservation and emission reduction of dyeing and finishing enterprises. The exhaust gas of the setting machine has high temperature and large gas volume, which directly causes a large amount of energy waste. High temperature of waste gas is not conducive to subsequent purification. High efficiency operation of the unit, heat recovery is an essential pretreatment unit for waste gas treatment.
Using heat exchange to recover part of the heat contained in the waste gas can produce good economic benefits. The heat recovered by the water / air heat exchanger is mostly stored in the form of hot water, which can be used in the boiling and refining process in the printing and dyeing industry; the air / air heat exchanger is used to preheat the fresh air and then use it in the heat setting process, which can reduce the fuel consumption of the boiler by more than 100000 yuan per year.
Oil recovery. There are many organic compounds in the high-temperature waste gas from the setting machine, which is very harmful to human health and ecological environment; the waste gas from the heat setting process of the processing of chemical fiber fabric has a high content of oil compounds with high boiling point and viscosity. In the process of waste gas purification, the black brown oil (commonly known as "chemical fiber oil") is separated and can be used as a good industrial building membrane mold agent, with a price of 3500-4000 yuan per ton; based on the recovery of 50kg waste oil per day for each set of setting machine, tens of thousands of yuan of economic benefits can be generated in one year.
Combined process and deep purification
The composition of the waste gas of the setting machine is complex, often contains a large number of submicron viscous particles, and the treatment efficiency of a single conventional process is not high. It is necessary to adopt a combined process including high-voltage electrostatic precipitator technology to conduct a deep treatment of the flue gas, so as to achieve a good purification effect