RU2299916C1 - Rolled bar heat treatment process control method in multisectional thermally strengthening plants - Google Patents

Abstract

FIELD: metallurgy, namely manufacture of rolled bars treated in multi-sectional thermally strengthening plant.

SUBSTANCE: method comprises steps of supplying cooling agent from common main line through individual pipelines to sections with cooling nozzles. Cooling agent is fed from common low-pressure main line by means of high-pressure pumps arranged in individual pipelines. Efficiency of high-pressure pumps is successively lowered from section to section in order to provide supply of cooling agent to each section in mode of its maximum technologically caused load. Inlets of said pumps are communicated through cut-off dampers with low-pressure main line and outlet of said pumps are communicated with inlets of nozzles. Electric motors are mounted with possibility of controlling their revolution number by means of separate transducers to inlets of which task is fed from system for automatic control of thermal strengthening.

EFFECT: energy saving due to minimized electric power consumption for supplying water in sections of plant for thermal strengthening.

2 cl, 2 dwg, 1 ex

Description

The invention relates to the field of metallurgy and can be used in the manufacture of long products processed in a multi-section heat-strengthening plant.

A known method of controlling the process of heat treatment of long products in multi-section heat-strengthening plants, including measuring the temperature of the car and cooler at different points of the installation and regulating, in accordance with these data, the flow rate of water supplied from the high-pressure manifold, using throttling valves installed in front of the cooling sections ( see SU 1676699).

The method involves the use of a common high-pressure manifold, which is created by high-power pumps operating continuously in an uneconomical energy mode.

Closest to the claimed one is a method for controlling the heat treatment process of long products in multi-section heat-strengthening plants, comprising supplying a cooler from a common line through individual pipelines to sections with cooling nozzles. A high pressure collector is also used as a highway, the flow rate of the water in the section is regulated by valves connected to the collector (see RU 2183522 C1, 06/20/2002). The disadvantages of the method include the fact that when using a high pressure collector as a common line and regulating the flow of water in the sections using valves or other throttling devices, energy losses are proportional to the pressure drop on these devices. The issue of energy saving is especially significant when it comes to devices in which there is a need to supply water to individual consumers with different, sharply different needs. Such devices include multisectional plants for heat hardening of rolled products.

The objective of the invention is to save energy by minimizing the consumption of electricity for water supply to the sections of the installation for heat strengthening, having a sharply different need for the amount of water, while maintaining the necessary technological parameters of the processed steel.

The objective is achieved in that in the method for controlling the heat treatment process of long products in multi-section heat-strengthening plants, comprising supplying a cooler from a common line through individual pipelines to sections with cooling nozzles, in accordance with the invention, the cooler is supplied from a common low-pressure line by means of pumps installed in individual pipelines high pressure with successively decreasing power in sections, ensuring the supply of cooler to each section in the mode its maximum technologically determined load, while the pump inlets are connected through shut-off valves to the low-pressure line, and the outputs are connected to the nozzle inlets.

In addition, the cooler can be supplied by means of pumps, the electric motors of which are configured to control the speed of individual converters, the inputs of which serve the task from the automatic control system of heat strengthening.

Energy saving is achieved thanks to the proposed configuration and control algorithm of the water supply system, in which each section receives power from an individual high-pressure pump less than the total pump power sufficient to supply each specific section. The power range of each pump used is calculated in advance, depending on the range of technological parameters of the process, such as water flow, pressure, etc., while eliminating the need for a powerful pumping station.

It should be noted that energy saving techniques by maintaining optimal pressure in the general supply water conduit by a special characteristic, as a function of the flow rate of water in it, are known between the maximum and minimum values (see RU 2224172). However, on separate water supply lines with different water flow rates, energy losses of different sizes will occur, inversely proportional to the water flow in these lines and due to the presence of excess pressure.

The present invention initially provides optimal energy conditions, eliminating overpressure in the common line, and, consequently, energy loss.

The invention is illustrated by drawings, in which Fig. 1 shows a control system for the heat treatment of long products in multi-section heat-strengthening plants, in Fig. 2, comparative configurations of water supply networks: in Fig. 2a, the same corresponds to the method described in document RU 2224172, in Fig. .2b - the same, corresponding to the claimed method, on figv - characteristics that explain the degree of efficiency of the compared methods and schemes of water supply.

Figure 1 marked:

1 - the last mill stand,

2 - rental

3 - sections of the installation of hardening,

4 - high pressure pumps,

5 - pump motors,

6 - individual converters,

7 - water flow sensors in each section

8 - shut-off valves of the pumps,

9 - water temperature sensors at the outlet of the sections

10 - nozzle valves

11 - low pressure manifold,

12 - plums,

13 - winder,

14 - substitution tunnel,

15 - rolling speed sensors,

16 - sensors temperature rental

17 - tasks for the supply of cooling water in the section,

18 - water temperature sensors at the inlet to the pumps.

Each quick cooling section 3 is equipped with an individual high pressure pump 4 with a power sufficient to supply only one section at maximum load. The regulation of the flow of water is carried out by changing the speed of the motors of 5 pumps powered by individual converters 6.

The method is implemented as follows.

Hot rolled 2 (wire rod, reinforcing bars, etc.) comes out of the last stand of mill 1, sequentially passes through the cooling sections 3, while acquiring increased mechanical strength. Next, the wire rod is reeled up by a coiler 13, and the reinforcing bars go to the refrigerator (not shown).

From the low pressure manifold 11, water is supplied to the pumps through the shut-off valves 8, which serve only to connect the pump to the water source and do not lead to energy losses during pump operation, since they are fully open. High pressure pumps 4 supply each individually to its own quick cooling section to nozzles forming water jets at a speed of 1.5-2 times greater rolling speed, as well as to shut-off nozzles creating water jets in the opposite direction at a lower speed (for eliminate the release of water through the holes for the passage of the rental). Water from the cooling sections is discharged through drains 12 into a substitution tunnel 14. The speed of the water in the shut-off nozzles is controlled by valves 10 when setting the operating mode of the installation.

In the control system of the process of hardening (SAUT) information is supplied from the sensor 15 of the rolling speed, the sensor 16 of the rental temperature, the sensor 17 tasks for the supply of cooling water in the section, the sensor 18 of the water temperature at the inlet to the pumps. The operator enters tasks corresponding to the calculated cooling schedule for water supply to each section. In accordance with a predetermined algorithm (for example, maintaining a predetermined balance of heat removal in each cooling section), SAUT changes the rotational speed of the motors 5 of pumps 4 by affecting the inverters 6 feeding them, thereby individually regulating the given flows of cooling water in the optimal energy mode, excluding throttling energy loss.

For comparison (Fig. 2), let us assume that in Fig. 2a the sections have the same water flow Q, at a pressure of P4 on them, while the total water flow from pump H5 will be 4Q, pump H5 will develop pressure P2, and the engine will consume it from network power proportional to the area of the rectangle 0.4Q, P2, P2. Energy proportional to the area of 0.4Q, P4, P4, is useful in sections, and energy proportional to the area of P4, P2, P2, P4 (equal to 4ΔP1, hatched by sloping to the right by hatching), displays the losses due to throttling in the throttle controllers ДР1, ДР2, DR3, DR4. If we assume that in section 4, the water flow decreased by a third and became 2 / 3Q, then at its inlet the pressure decreased to P5 due to an increase in the pressure drop on the throttle control valve ДР4. In this case, the energy losses on DR4 will be proportional to the area shaded by slanting to the left by hatching, they will be more than the useful power consumed proportional to the area Q, 2 / 3Q, P5, P5. The regulator on the H5 pump, according to the ХН5 characteristic, will slightly lower the pressure in the high-pressure water supply duct of the VVD to the value P3, thereby slightly reducing the energy consumption from the network, and the regulators ДР1, ДР2, ДР3 will keep the set pressure on their sections. Thus, this scheme does not effectively reduce energy losses due to throttle control at individual end users.

From the diagram in fig.2b (the claimed method) it is obvious that by adjusting the speed of the motors of the pumps H1, H2, H3, H4, you can provide any given value of the flow rate in the sections, while there is no throttling loss.

Example.

Hot rolled metal leaves the last stand of the rolling mill and is sent to a heat-strengthening unit for sequential processing in the cooling sections. According to the technological conditions, a large (maximum) flow of cooler is supplied to the first section; the power of the pump installed in this section is 350 kW. The metal that has passed this section is cooled, however, the temperature of its outer surface increases due to heating from the inside. In the second section along the metal, in accordance with technological expediency, a pump of lower power is installed, namely a power of 300 kW, in the third - 250 kW, in the fourth - 200 kW, etc. In the last section, as a rule, 3-4 times less cooler is required than in the first, respectively, and the power of the pumps used in the first and last sections are in the same range of ratios. Energy losses due to the regulation of pressure and water flow in the cooling sections do not occur. Only insignificant natural losses of pressure and, consequently, energy in the pipes take place.

When the sections of the common high pressure collector were supplied with the cooler at the inlet to the last section, it would be necessary to reduce the pressure of the cooler by 15-70% compared with the first section, which would mean the loss of the corresponding amount of energy. When using the claimed method, energy losses are practically absent. Energy savings can reach an average of 30-40%.

Claims (2)

1. A method of controlling the heat treatment process of long products in multi-section heat-strengthening plants, comprising supplying a cooler from a common line through individual pipelines to sections with cooling nozzles, characterized in that the cooler is supplied from a common low-pressure line by means of high pressure pumps installed in individual pipelines with gradually decreasing in sections with a power supplying a cooler to each section in the mode of its maximum, technologically copulating load, the inlet of the pump is connected via shut-off valves on the low pressure manifold, and outputs - to the inputs of the nozzles. 2. The method according to claim 1, characterized in that the cooler is fed through pumps, the electric motors of which are configured to control the speed of individual converters, the inputs of which serve as a task from the automatic control system of heat strengthening.

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