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The textile printing and dyeing industry is a high-tech, energy intensive sector. In an effort to reduce energy bills， many companies have introduced innovative thermal initiatives such as saving on fuel costs by operating existing boilers less frequently !
In fact, the printing and dyeing industry can save energy from the following four aspects.
1. Energy saving of boiler system
2. Energy saving of heating system
3. Energy saving of heat-consuming equipment
4. Waste heat utilization
In textile printing and dyeing enterprises, boiler systems can be divided into steam boilers and heat carrier boilers. The fuels used in boilers include coal, oil, and natural gas. Due to cost problems, most of them are coal-fired, and some are Sawdust for fuel.
In textile printing and dyeing enterprises, most of the steam is used once and some are used twice, for example, enterprises with cogeneration units. After use, the steam is condensed into water, and the waste heat contained in the steam cannot be utilized, which reduces the utilization efficiency of the steam heat energy.
The multi-stage utilization of steam can improve the utilization efficiency of heat energy, especially some enterprises with cogeneration units can use steam in multiple stages to improve the utilization rate of steam enthalpy.
In the actual situation, to achieve multi-stage utilization of steam, it is necessary to generate high-grade steam, and then reduce the temperature and pressure during the classification utilization process, so that the thermal energy can be fully utilized. The following factors should be considered in the multi-stage utilization of steam:
(1) The distance of steam supply;
(2) Whether the configuration of the heat setting machine equipment is suitable;
(3) The demand and pressure of various steam;
(4) Site conditions of various equipment.
In addition to the above factors, the availability of personnel and auxiliary equipment should also be considered.
The medium heated by the heat carrier boiler is high temperature heat transfer oil. The use of high temperature heat transfer oil as the heat transfer medium has certain advantages, that is, the waste heat of the medium can be better utilized. At the same time, the high-temperature heat transfer oil will not condense, and the heat supply is stable and easy to control. Some enterprises need both steam and high-temperature heat transfer oil for heating. In order to reduce the number of boilers, heat carrier boilers are used to generate steam.
The control of boiler air coefficient has not been paid much attention by most enterprises. Most enterprises believe that there are many technical difficulties in the control of boiler air coefficient. In fact, what is more important is that most managers fail to realize the significance of air factor control. Practical experience shows that a 5% reduction in excess air yields a 1% increase in boiler efficiency.
Unstable steam consumption in production workshops is a feature of steam consumption in textile printing and dyeing enterprises. However, uneven steam consumption will lead to lower combustion efficiency and lower thermal energy utilization. It may not be realistic to completely solve the problem of balanced steam supply. However, it is possible to reduce the unevenness of the steam supply through management, especially through production planning and scheduling.
The main methods are: the production sequence of the whole machine: in the dyeing and finishing production, especially in the intermittent dyeing production, the steam consumption is also intermittent. Therefore, through a certain method, the steam consumption peak of each production process is staggered to balance the steam consumption.
The heating system refers to the steam transmission pipe network or the transmission pipe network of high temperature hot oil. Thermal energy is dissipated during transmission. Therefore, reducing the loss of heat energy in the transmission process is the work of the heating system to save energy.
1. Insulation: The insulation of the pipeline is the main method to prevent or reduce the dissipation of heat energy during the transmission process.
There are several issues with regard to insulation:
(1) Insulation part: In textile printing and dyeing enterprises, the temperature of the steam delivered is above 150°C, and the temperature of the high-temperature hot oil is 200-240°C, which is quite different from the room temperature.
Therefore, in addition to the pipes, the heat preservation of the heating pipe network should also be carried out on the valves.
According to the budget, if a valve is not insulated, the annual heat loss is equivalent to 1-3 tons of standard coal.
(2) Pipeline insulation: Most companies will pay attention to the insulation of pipes.
However, some enterprises still do not pay enough attention to the thermal insulation of steam pipelines and high-temperature heat-conducting oil pipelines, and do not repair damaged thermal insulation layers in time. Failure to insulate the heating pipes will result in a certain amount of heat loss. For example, a 100m long steam pipe with a diameter of 150mm is not insulated, and when the pressure is 8kg, 25000L of fuel oil will be wasted every year.
(3) Outer protective layer of the thermal insulation layer: The thermal insulation effect of the pipe network is not only related to the material of the thermal insulation layer, but also to the material of the outer protective layer of the thermal insulation layer.
If the outer protective layer is soft and absorbent, the water in the air will be absorbed by the insulation layer and transmitted to the vicinity of the pipe, and the absorbed water will cause heat loss. In general, 5-10% of the total heat loss can be achieved. Therefore, non-absorbent materials such as stainless steel and engineering plastics can be used as the outer protective layer.
2. The connection method of the steam pipeline: There are many ways to connect the steam pipeline.
3. Steam conveying pressure: During the conveying process of steam, there will be losses. When the steam delivery volume is constant, the smaller the radius of the steam pipeline, the greater the pressure required during the transportation process, the resistance of the steam during the transportation process, and the loss increase. Therefore, appropriately increasing the radius of the steam pipeline and reducing the pressure during the steam transportation process is beneficial to reduce the loss during the transportation process.
4. Leakage of steam pipeline: Leakage of steam pipeline is the main part of steam loss in the enterprise. Some employees of printing and dyeing enterprises think that it is impossible to eliminate the leakage of steam, and this wrong understanding must be overcome. For example, with a vapor pressure of 7kg, a hole with a diameter of 3mm would waste 32,650L of fuel oil per year.
The heat-consuming equipment here refers to the production equipment that uses steam or high-temperature hot oil as the heat source.
In practice, it is found that the heat utilization rate of heat-consuming equipment is often only 30-42%. Therefore, the energy saving of heat-consuming equipment is of great significance for enterprises to reduce the consumption of heat energy.
The insulation of heat-consuming equipment, especially the high temperature and high pressure dyeing machine, is of great significance to reduce the consumption of heat energy. Taking polyester dyeing as an example, thermal insulation of the high-temperature and high-pressure dyeing machine can reduce heat consumption by about 1/3.
The thermal insulation materials currently available in the market can meet the thermal insulation requirements of various heat-consuming equipment.
For example, the normal temperature and normal pressure dyeing machine and the airflow dyeing machine have large volume and large shape change, and can be insulated with coating paint.
The insulation of heat-consuming equipment can not only directly reduce the consumption of heat energy, but also improve the environment of the production workshop and reduce the electricity consumed by the cooling of the workshop. Now, in some production sites, on the one hand, the heat-consuming equipment emits a lot of heat energy, and on the other hand, in order to reduce the temperature of the workshop, fans or even ice are used to cool down. The result is increased thermal energy losses.
There are many reasons for the low heat utilization rate.
However, some devices do not control the amount of air intake or exhaust, resulting in excessive heat loss is one of the reasons. For example, heat setting machines and dryers have excessive air intake or exhaust air volume, resulting in a large amount of heat loss. Therefore, in order to improve the heat utilization rate of such equipment, it is necessary to control the exhaust air volume or the air intake volume.
At present, some enterprises are still using production equipment with low heat utilization rate, for example, vertical cylinder dryer and open jigger have low heat utilization efficiency of. The thermal energy utilization rate of the vertical cylinder dryer is generally below 30%. Therefore, in the case of meeting the production needs, these production equipment with low heat utilization rate should be eliminated.
For textile printing and dyeing enterprises, it is necessary to do a good job of waste heat utilization in order to greatly improve the utilization rate of heat energy. In general enterprises, unused waste heat accounts for 40-30% of the total heat consumption.
For the waste heat of boiler flue gas, many enterprises utilize the waste heat by using economizers and air preheaters.
There is still some room for the utilization of waste heat from flue gas in some enterprises. For example, insulate economizers and air preheaters to increase water and air temperatures. In addition, the heat exchange area of economizers and air preheaters of some enterprises is too small, and the utilization rate of flue gas waste heat is too low. In addition, the flue gas passing through the economizer and air preheater still has a temperature of 100-120 °C, and the utilization of this part of the waste heat should be considered under conditions. Such as: waste heat refrigeration. It is calculated that the flue gas temperature decreases22℃, the boiler efficiency increases by 1%.
During the printing and dyeing process, the water temperature of part of the discharged waste water is 60-95 ℃, which contains a lot of waste heat. The waste heat of the wastewater can be used to heat fresh cold water through a heat exchanger to utilize the remaining heat. Among various heat exchangers, the plate heat exchanger has the best effect and higher recovery efficiency.
In order to further save energy and promote the healthy development of textile printing and dyeing enterprises, some operable and practical thermal energy saving techniques and methods are introduced in this paper. Some problems existing in the current energy saving work of textile printing and dyeing enterprises are given opinions on.
We hope these measures can provide reference for your company’s thermal energy conservation work. Which industry are you in? Choose a boiler for your industry now!
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