1. System advantages:

Energy conservation and consumption reduction in industrial enterprises is an important basic national policy of the country and a key measure for enterprises to reduce costs. In pulp and paper enterprises, the steam consumption of the drying section of the paper machine accounts for more than half of the entire paper machine operating costs. How to reduce the steam consumption index is an important way for enterprises to reduce costs and gain benefits. Gaoda Technology uses its own successful transformation and application of the drying section of paper machines for many years to provide pulp and paper enterprises with a full range of steam and condensate solutions for various products of various paper machines.

The steam and condensate control system of the paper machine of Gaoda Technology includes an intelligent control system that can monitor the drying process of the paper machine in real time, and automatically adjust the parameters of the steam and heat pump according to the production situation to make it operate in the most efficient working state. At the same time, with the help of advanced algorithms and data analysis technology, it can accurately predict the energy consumption of steam and heat pumps, make the best decision, achieve the minimum energy consumption and meet the coordinated control of different product quality requirements.

According to the user's working conditions, we can provide multi-stage ventilation or heat pump (fixed or adjustable) to solve the problem of energy saving in paper machine drying. It is now widely and reliably operating on hundreds of paper production lines at home and abroad.

2. Solution Types

3. Paper Machine and Steam

1) Paper machine drying section The drying section accounts for more than half of the total equipment investment and operating costs of the paper machine.

Importance of reasonable design (steam and condensate system, ventilation, drying network) Drying rate and steam consumption are two important indicators for evaluating the performance of the drying section to ensure uniform evaporation and removal of moisture from the paper sheets in the transverse direction of the paper machine. The relative costs per ton of paper are: Forming section: 10% Pressing section: 12% Drying section: 78% From the cost point of view, a 1% increase in pressing dryness is equivalent to a 5% increase in drying efficiency.

2) Paper machine drying curve

It is determined according to the characteristics of the paper type produced. Generally, it gradually rises at the beginning, then becomes flat, and finally, it slightly decreases. Drying curve of the drying cylinder with surface sizing: It is determined according to the characteristics of the paper type produced. Before surface sizing, it is generally 80~85℃. After chrome plating, in order to prevent the paper from sticking to the cylinder, the temperature is generally 60~80℃. Before the paper is rolled up, it is generally 55~70℃. The larger the paper weight, the larger the number of medium temperature sections should be. In general, the drying of paper has a cycle of heating up, cooling down, and heating up again.

3) The function of the cold cylinder is to reduce the temperature of the paper (from 70-90 degrees to 50-55 degrees), increase the water content of the paper (usually 1.5%-2.5%), improve the plasticity of the paper, and through subsequent calendering, improve the tightness and smoothness of the paper, and reduce the static electricity of the paper. When the paper is dried to a moisture content of 4-6% and a temperature of 70-90 degrees, it passes through 1-2 cold cylinders. The temperature is controlled by cooling water, and the cooling water consumption is 3-5kg water/kg paper.

4) Drying cylinder requirements for steam When clean dry steam enters the drying cylinder, almost all of the latent heat released by the steam is used for heat transfer in the drying cylinder, which is an ideal effect. When wet steam with a large water content enters the drying cylinder, part of the latent heat released by the steam is used for heat transfer in the drying cylinder, and part is absorbed by the water, which is not good for paper machine drying. Superheated steam does not produce condensed water during transportation, which is conducive to transportation. However, it can only produce very little heat energy in the process of changing from superheat to saturation, so it is not conducive to directly entering the drying cylinder. In theory, the steam that enters the drying cylinder to complete the heat exchange should be saturated dry steam.

5) Drying Cylinder and Condensate Drainage The drying cylinder needs to drain condensate. When steam meets condensate that is cooler than steam, another type of water hammer will occur, called thermal shock. The volume occupied by steam is much larger than that of condensate. When the volume of steam suddenly decreases, it will send shock waves to the entire system. The formation of this water hammer can damage the pipes and the inner wall of the drying cylinder and wear the siphon. In addition, the presence of condensate will consume the latent heat generated by steam condensation and reduce the surface temperature of the drying cylinder.

4. Heat Pump Control System

1) Heat Pump Mechanism Steam heat pump is a thermal compressor without moving parts. It consists of a nozzle, a receiving chamber, a mixing chamber and a diffusion chamber. After the high-pressure steam passes through the Laval nozzle, the pressure is reduced and the speed is increased to form a high-speed low-pressure airflow, which drives the low-pressure steam to move into the receiving chamber, the mixing chamber and the diffusion chamber. The speeds of the two coaxial steams are balanced. At the same time, the speed of the mixed steam is reduced and the pressure is increased to obtain medium-pressure steam, which is supplied to the papermaking drying cylinder.

2) Typical heat pump control process The heat pump process design is highly personalized according to the differences in paper machine production capacity and products.

3) Design Description The steam inlet design is generally a double circuit, the main purpose of which is to adapt to the fluctuation of the thermal load of the paper machine.

The drainage end design mainly adopts the differential pressure orifice plate method

4) There are three ways to treat tail steam: large-scale high-speed paper machines use surface condensers, steam-water separators and vacuum pumps.

Medium speed paper machine adopts hydraulic ejector

Low-speed paper machine discharges directly into the condensate tank

Professional pulp and papermaking process engineers of GAODA Technology strictly group paper machines according to the drying conditions and product types to ensure that the grouping is reasonable and practical. The segmentation of special product paper machines should fully consider the product performance requirements. For example, the grouping of boxboard and white paper should consider the separate control of the upper and lower drying cylinder pressures to adapt to the adjustment of the smoothness difference between the two sides; the large-weight paper should consider extending the medium temperature section to avoid the phenomenon of burning, etc.

5. Multi-stage steam control system

1) Typical multi-stage steam flow process

The first section: 1# drying cylinder, a total of 1 drying cylinder, independent pressure automatic control steam inlet, drainage using differential pressure control (interlocked with the vacuum pump vacuum). This section is the preheating section after paper feeding, mainly to ensure that the paper does not stick to the cylinder when it just enters the cylinder.

The second section: 2#~3# drying cylinders, a total of 2 drying cylinders, separate pressure automatic control steam inlet, drainage using pressure difference control. This section of pressure is low temperature section.

The third section: 4#~8# drying cylinders, a total of 5 drying cylinders, independent pressure automatic control steam inlet, drainage using differential pressure control. This section of pressure is low temperature section. This section of steam inlet uses three steam sources: new steam, medium temperature section flash steam and condensed water summary flash steam.

The fourth section: 9#~16# drying cylinders, a total of 8 drying cylinders, independent pressure automatic control steam inlet, drainage using differential pressure control. The pressure of this section is the medium temperature section. This section uses two steam sources for steam inlet: new steam and high temperature flash steam.

The fifth section: 17#~34# drying cylinders, a total of 18 drying cylinders, independent pressure automatic control steam inlet, drainage using differential pressure control. This section of pressure is a high temperature section. This section of steam inlet uses a steam source: fresh steam.

The sixth section: 35#~36# drying cylinders, a total of 2 drying cylinders, independent pressure automatic control steam inlet, drainage using differential pressure control. The pressure of this section is the preheating section after glue application. The steam inlet of this section is all flash steam from the upper exhaust cylinder of the conditioning section.

Section 7: 37#~38# drying cylinders, a total of 2 drying cylinders, separate pressure automatic control steam inlet, pressure difference control for drainage. This section is a low-temperature section. The steam inlet in this section is all flash steam from the drying cylinders discharged from the state-adjusting section.

Section 8: 39#～47# lower row drying cylinders, a total of 5 drying cylinders, separate pressure automatic control steam inlet, drainage using differential pressure control. This section of pressure is a state adjustment section. This section uses a steam source: fresh steam.

The ninth section: 40#～48# upper row drying cylinders, a total of 5 drying cylinders, separate pressure automatic control steam inlet, drainage using pressure difference control. This section of pressure is a state adjustment section. This section uses a steam source: fresh steam.

Section 10: 49#~50# drying cylinders, cooling cylinders. The purpose is to reduce the temperature of the paper (from 70~90 degrees to 50~55 degrees), increase the water content of the paper (usually 1.5%~2.5%), improve the plasticity of the paper, and through subsequent calendering, increase the tightness and smoothness of the paper, and reduce the static electricity of the paper.

2) Functional description

In order to fully guarantee the user's use, Gaoda Technology has adopted the following convenient operation functions in the multi-stage steam supply system software configuration process: Cylinder warming function: When the paper machine is just started, due to process requirements, the system will automatically enter the cylinder warming program (it can be selected whether to warm the cylinder). At this time, the steam pressure of each section is maintained at about 0.1Mpa (the cylinder warming setting value can be modified), and the cylinder warming time is generally 10 to 15 minutes.

Automatic emptying function: Before the paper machine is fed with steam, the drying cylinder is full of air. When the steam comes, the steam drives the air out until it is emptied. This process takes too long on some paper machines. In order to warm up the cylinder quickly, the software is designed with an automatic emptying function. During the automatic emptying period, all drain valves are fully opened, and the vacuum pump is started in advance, changing passive emptying to active emptying.

Paper break cooling function: When the paper machine breaks, click the paper break command (or introduce the paper break signal), and the system enters the paper break processing program. At this time, the pressure regulating valves of each drying section are fully closed. After the pressure of each drying section is lower than the paper break setting value, the pressure regulation controls the pressure to stabilize at the corresponding paper break setting value. This program can effectively avoid the sudden change of the drying cylinder pressure and cylinder surface temperature caused by the sudden decrease of the condensation rate after the paper break occurs, and avoid unnecessary losses of equipment and dry blankets. This function can be divided into front and rear paper break modes, and the processing methods are different.

VI. Auxiliary measures and related equipment

1) Temperature and pressure reduction device and its working principle

Pressure reducing regulating device: Steam pressure reduction is achieved by a pressure reducing valve and a throttling orifice plate. Two throttling orifice plates can be connected in series according to different parameters.

Desuperheating regulating device: After the desuperheating water is atomized by the nozzle, it contacts with the high-temperature superheated steam to achieve temperature balance. The atomization effect is the key to the use of the desuperheater.

Safety protection device: When the secondary steam pressure exceeds the specified value, the safety valve on the device automatically opens to discharge part of the steam into the atmosphere. The protection device can be selected from impulse safety valve, spring safety valve and lever safety valve according to different parameters.

2) High-efficiency flash tank When water and gas enter the flash tank through the inlet in the middle of the separator, according to the difference in specific gravity, the heavy water is discharged through the lower drainage hole of the separator, and the light gas is discharged through the top exhaust hole of the separator.

3) Hydraulic ejector

The hydraulic ejector is a mechanical device with three effective functions: vacuuming, condensing, and draining. It uses a certain pressure of water to be ejected through nozzles that are symmetrically distributed at a certain inclination and converge at a focus. Since the jet water flow is very fast, a negative pressure is formed around it, which creates a vacuum in the chamber. In addition, since the secondary steam is in direct contact with the jet water flow and heat exchange is carried out, most of the steam condenses into water, and a small amount of uncondensed steam and uncongealed gas are also rubbed, mixed and squeezed with the high-speed jet water flow, and are discharged through the diffuser, so that a higher vacuum is formed in the chamber.

4) Surface condenser

The working principle of the surface condenser: the secondary steam under vacuum state enters the inner cavity of the condenser plate or tube sheet, and is condensed into water after several detours in the plate or tube sheet. The uncondensed non-condensable gas is pumped out by the vacuum pump at the top, and the cooling water passes through the distributor to form a liquid film on the plate or tube sheet, and freely falls to the bottom along the plate sheet.

5) Others