BR102019015247A2 - energy-efficient pressure control system and method using pressure reducing turbine - Google Patents

Abstract

the present invention relates to a system and method for energy reuse in steam systems linked to industrial processes, using steam turbines for lowering pressure and / or replacing pressure reducing valves. as a main feature of the tank, the control to maintain the steam outlet pressure of the fixed turbine system, similar to that of a reducing valve, varying the power of reused electrical energy (and other parameters) as a function of pressure variations and flow rates. steam required by the industrial process.

Description

“PRESSURE CONTROL SYSTEM AND METHOD WITH ENERGY REUSE USING PRESSURE REDUCING TURBINE”

Field of the Invention [0001] The present invention relates to a pressure control system and method using pressure reducing turbines with energy reuse. The present invention is located in the fields of Mechanical Engineering, more specifically in the field of hydraulic, gas and steam turbines.

Background of the Invention [0002] Currently, some industrial and government customers with extensive use in energy, with emphasis on thermal systems with steam, such as petrochemicals, paper and cellulose, steel, thermoelectric, food, shops, hotels and hospitals have waste of energy, causing process inefficiency, increasing operating costs and decreasing competitiveness. A major source of energy waste is pressure reduction processes in process fluids. The steam produced by boilers is one of the main fluids used in thermal systems. The lowering of steam pressure in processes is a common and necessary operation for the system to function. These pressure reductions, which are currently carried out by reducing valves, generate a great loss of energy in the form of heat (loss of pressure). To solve this problem, a pressure control system and method is proposed that employs a Pressure Reducing Turbine (TRP), a compact steam turbo-generator and developed specifically to control the pressure, which

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2/17 performs the same operational function as the valve and has the benefit of taking advantage of the waste of energy for the generation of electrical energy (enthalpy difference between the input and output of the TRP steam), promoting renewable energy generation, energy efficiency , sustainability, knowledge of the process and reduction of operating costs.

[0003] According to the EPE, 2014, it is estimated that in Brazil about U $ 3.8 billion / year is spent on processes that involve heat. According to ABESCO, 2016, the Brazilian energy efficiency market has an estimated business potential that can exceed R $ 60 billion. In Brazil, approximately 20% of the industries use thermal systems with steam, that is, more than 70,000 thousand industries. Of these industries, most have more than one reducing valve in their process. At a global level, no company is only dedicated to the replacement of reducing valves by TRP, operating in this niche market that requires knowledge of turbines and industrial processes.

[0004] Currently, large manufacturers are focused on the manufacture of large equipment for power generation, with powers above 1 MW. Companies with an exclusive focus on energy use have not been mapped, more precisely replacing pressure reducing valves. These manufacturers could enter the TRP market, but this would require a complete change of focus and strategic planning, since it would be necessary to develop a specific product project to control the pressure, the project requirements would be totally different (new portfolio of customers) and would also be

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3/17 it is necessary to change its productive structures from a few large equipment to several small equipment.

[0005] At world level, the helical screw turbine developed by the Chinese company HD is known, which operates exclusively with steam and replacing reducing valves, having a dedicated solution for pressure reduction and control. This turbine model is used in several applications, such as contaminated liquids, contaminated vapors, hot air, saturated steam, natural gas, etc. However, industrial processes that use the reducing valve, most of them present variations in steam flow, variation of pressure at the inlet and need control of the outlet pressure, situations that the screw turbine does not satisfactorily meet.

[0006] Distributed Generation (DG), characterized by small generations, typically less than 30 MW (GAS RESEARCH INSTITUTE, 1999) has been gaining prominence in contemporary society, in which energy waste is less and less tolerated. Within GD there is a great potential for energy use for electric generation on a scale classified as micro (below 75 kW) and mini (between 75 kW and 1 MW). In many cases, these uses are not feasible for economic reasons, but currently several countries seek to encourage their use. In Brazil, for example, ANEEL approved regulatory resolution No. 482/2012 and 687/2015.

[0007] Few studies were found during the development period of the control system using

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4/17 the pressure reducing turbine, related to the use of steam turbines replacing valves.

[0008] The article entitled: “The Role of Distributed Generation in Competitive Energy Markets” in the Distributed Generation Forum, Chicago, 1999, describes the rule of distributed generation in current and emerging energy markets. The discussion focuses on the following topics: distributed generation technologies, applications for distributed generation, benefits of distributed generation, restructuring of the electrical industry and responsibilities and perspectives of stakeholders.

[0009] The article entitled EXERGETIC ANALYSIS OF PRESSURE REDUCING VALVES FOR COGENERATION ”, by Geraldo Augusto Camplina França and Lis Nunes Soares, published in Science & Engineering Journal, 2005, develops energy and exergetic analyzes of pressure reducing valves in an oil industry. cellulose, aiming at the use of cogeneration. As results, comparisons are presented between the assessments of energy and exergetic efficiencies of the analyzed processes, as well as a preliminary analysis of the technical and economic feasibility of cogeneration. The study by FRANCE and SOARES, 2005 addressed this application, but in a specific way in a large industry, not mapping the entire potential market and not identifying exclusive manufacturers for the application of the method and system of the present invention.

[0010] No solutions were found in the state of the art for thermal recovery through the replacement of pressure reducing valves with pressure reducing turbines.

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5/17 pressure using a pressure control system as described by the present invention.

Summary of the Invention [0011] Due to TRP's characteristic of taking advantage of thermal waste to generate renewable energy and energy efficiency, its installation is simplified, since the industries already have the entire steam thermal system, requiring only the installation of the TRP, allowing the return on investment of the TRP application to be between 1 and 4 years, depending on the power of the equipment, the operating regime of the industry and the average cost of electricity.

[0012] A preferred embodiment of the present invention relates to a pressure control system with a steam turbine system comprising:

steam inlet valves for a pressure reducing turbine controlled by an actuator driven by a signal from a programmable logic controller;

pressure reducing valves that can be used in series or in parallel with the TRP, aiming to maximize the energy use (As an example of applications, we can mention the reducing valve arranged interconnecting the inlet and outlet pipes for extreme operational situations, such as peak steam flows that have low occurrence; at the exit of the TRP to maximize the generation of electric energy, between stages and etc.).

pressure and steam temperature sensors arranged respectively at the inlet and outlet of the pressure reducing turbine providing data to the programmable logic controller;

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6/17 pressure reduction turbine speed, flow and vibration sensors providing data to the programmable logic controller;

in which the programmable logic controller receives data from pressure, temperature and flow sensors, comparing them with desired values and sending command signals to an actuator of the steam intake valves and / or to an energy export controller;

where the energy export controller selects the electrical power for export to the grid, according to the desired output pressure setpoint, that is, if it is necessary to increase the output pressure, the export controller will receive a signal from the PLC to increase the exported power and a signal to open the turbine intake valve will return to the PLC. To decrease the outlet pressure, the procedure is the opposite;

where the Pressure Reducing Turbine (TRP) consists of a steam turbo generator controlling the pressure of steam, performing the same operational function as a pressure reducing valve and using the pressure drop for the generation of electrical energy based on enthalpy difference between steam inlet and outlet.

[0013] According to an embodiment of the present invention, the system has a second control option, Figure 7, with the use of frequency inverters to replace energy export controllers. This option is used for turbines operating without a speed reducer, with generators coupled directly to the turbine, operating at speeds above 3600 RPM, which comprises:

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7/17 steam intake valves for a pressure reducing turbine controlled by an actuator driven by a signal from a programmable logic controller;

pressure reducing valves can be used in series or in parallel with the TRP, aiming to maximize the energy use.

pressure and steam temperature sensors arranged, respectively at the inlet and outlet of the pressure reducing turbine, providing data to the programmable logic controller;

pressure reduction turbine rotation, flow and vibration sensors providing data to the programmable logic controller;

in which the programmable logic controller receives data from the pressure, temperature and flow sensors, comparing them with desired values and sending command signals to an actuator of the steam intake valves;

in which the frequency inverter receives a setpoint to keep the turbine rotation steady and consequently increases or decreases the energy exported to the electric grid, in which the Pressure Reducing Turbine (TRP) consists of a steam turbogenerator controlling the steam pressure , performing the same operational function as a pressure reducing valve and using the pressure drop for the generation of electrical energy based on the difference in enthalpy between the steam inlet and outlet.

[0014] According to an embodiment of the present invention, the pressure control system further comprises valves arranged between two or more stages of pressure lowering, being controlled by the actuator.

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In accordance with an alternative embodiment of the present invention, the control system further comprises a complementary system having at least one pressure reducing valve to operate in conjunction with the turbine, which can be positioned in parallel or in series with the Turbine. This valve can be allocated at the turbine inlet, at the turbine outlet, between stages and connecting the turbine inlet and outlet.

[0016] The present invention also relates to a pressure control method with a steam turbine system comprising:

- detect a pressure value measured at the turbine output terminals using a pressure sensor;

- compare the pressure value measured at the outlet with a desired pressure value at the outlet using a controller (PLC);

- adjust through an energy export controller in communication with the controller (PLC) an exported power value based on the pressure difference obtained by the PLC controller;

- send a signal to the PLC controller through the energy export controller, which in turn sends a signal to an actuator coupled to the turbine steam inlet valve and if necessary to steam regulating valves between stages of the turbine, adapting the signal from the PLC controller and the desired pressure at the output; and

- keep the turbine rotation constant through the energy export controller by changing the energy export phases.

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9/17

- For the control option with frequency inverter, the PLC acts directly on the turbine intake valve;

- Use auxiliary turbine systems, with the presence of small pressure reducing valves to compensate for peak steam flows (which have low occurrence) and abnormal flow rates to the system;

[0017] According to an embodiment of the present invention, a method is provided in which the step of detecting a measured value at the turbine outlet further comprises detecting the temperature or flow of the steam.

[0018] The control system and method using the pressure reducing turbine of the present invention is a solution focused on the little-exploited thermal energy niche, with powers below 990 kW (small steam turbines, micro and mini generation) and replacing valves reducers in processes that already have steam, in industrial and government customers. It is an alternative to distributed generation and energy efficiency projects.

[0019] One of the benefits of using the control system and method using a pressure reducing turbine is the fact that it takes advantage of the existing steam infrastructure for cogeneration, causes the reduction of operational / energy costs and allows efficiency to be achieved of 5% to 20% of electricity consumption. In addition, as it is a renewable energy generation, it contributes to the CO2 emission target.

Brief Description of the Figures

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10/17 [0020] The objectives and advantages of the present invention will become clearer through the following detailed description of a preferred, but not limiting embodiment of the invention, in view of the attached figures, in which:

[0021] Figure 1 illustrates a basic diagram of a state of the art pressure reducing system that uses a pressure reducing valve;

[0022] Figure 2 illustrates a basic diagram of a pressure control system that uses a pressure reducing turbine, according to the preferred embodiment of the present invention;

[0023] Figure 3 illustrates a perspective view of a pressure reducing turbine containing a pressure reduction stage;

[0024] Figure 4 illustrates a perspective view of a pressure reducing turbine containing two stages of pressure reduction; and [0025] Figure 5 illustrates a block diagram with the components of the pressure control system, according to the preferred embodiment of the present invention.

[0026] Figure 6 illustrates an alternative embodiment in which the pressure control system further comprising a complementary system having at least one small pressure reducing valve.

Detailed Description of the Invention [0027] Figure 1 illustrates a basic diagram of a state of the art pressure reducing system using pressure reducing valve. As shown in figure 1, the state of the art pressure reduction system is

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11/17 disposed at the boiler outlet that generates steam. In the illustration of figure 1, a boiler is shown that generates a flow of 10 t / h of saturated steam with a pressure of 10 barg. This saturated steam with a pressure of 10 barg feeds the pressure reducing valve, which transforms it into a saturated steam for the process with a pressure of 5 barg. However, the use of the pressure reducing valve generates a great loss of heat, and thus, of energy that could be reused for the process.

[0028] Figure 2 illustrates a basic diagram of a pressure control system that uses a pressure reducing turbine, according to the preferred embodiment of the present invention. As shown in figure 2, the pressure control system is arranged at the outlet of the boiler that generates steam. In the illustration of figure 2, a boiler is shown that generates a flow of 10 t / h of saturated steam with a pressure of 10 barg. This steam saturated with pressure of 10 barg feeds the pressure reducing turbine, which transforms it into a saturated steam for the process with pressure of 5 barg. The difference with respect to the use of the pressure reducing valve is that there is no heat loss in this system. The heat that would be wasted is reused by converting mechanical energy into electrical energy to feed the plant or the electrical network.

[0029] Figure 3 illustrates a perspective view of an exemplary pressure reducing turbine containing a pressure reduction stage, to be used in the pressure control system.

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12/17 [0030] Figure 4 illustrates a perspective view of an exemplary pressure reducing turbine containing two pressure reduction stages, to be used in the pressure control system.

[0031] Therefore, the pressure reducing turbine may contain one or more stages of pressure lowering, according to requirements and / or demand of the plant where it is installed.

[0032] Figure 5 illustrates a block diagram with the components of the pressure control system, according to the preferred embodiment of the present invention.

[0033] As already known in industrial processes, boiler 10 generates saturated or overheated steam. This saturated steam is conducted to the pressure reducing turbine inlet through ducts and valves 11 which are controlled by an actuator 12. In the pressure reducing turbine inlet 13, pressure sensors 14 and temperature 15 are provided that provide data on the pressure and saturated steam temperature to a programmable logic controller (PLC) 16 capable of controlling the actuator 12 for opening and closing the steam supply valve 11 for the pressure reducing turbine 13. In this way, the steam flow delivered to the turbine is controlled.

[0034] Similar to the inlet, pressure sensors 17 and temperature 18 are arranged at the outlet of the turbine

13. The data detected by the pressure sensors 17 and temperature 18 at the turbine output are supplied to the programmable logic controller 16, which compares the values

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13/17 detected by the turbine outlet sensors with desirable values.

[0035] Programmable logic controller 16 is connected to a power export controller (DEIF) 19 connected to the power supply input for the plant or to the electrical network 20. In the case of the values detected by sensors 17, 18 at the output of the turbine are different from the desired values, the programmable logic controller 16 sends a signal to the energy export controller (DEIF) 19 which reduces or increases the value of the exported power to suit the required steam pressure. To control power, the energy export controller 19 sends a signal to programmable logic controller 16, which in turn sends a signal to an actuator 12 that drives the turbine's steam inlet valve 11, increasing or decreasing the steam flow through the turbine, which results in a higher or lower reused electrical power, adapting to the signal from the programmable logic controller and the desired pressure at the output. In addition to the energy export controller 19 controlling the actuator 12 and steam inlet valve 11, it is responsible for keeping the turbine rotation 13 constant by changing the energy export phases.

[0036] In addition to the pressure and temperature sensors, the control system of the present invention also comprises rotation, flow and vibration sensors to measure these parameters of the pressure reducing turbine. The data collected by these sensors are sent to the logic controller

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Programmable 14/17 16 and used to control energy exports.

[0037] The pressure reducing turbine is connected to a three-phase electric energy generator 21 known in the state of the art, capable of generating electrical energy from the mechanical energy established in the turbine due to the difference in enthalpy of the steam at the entrance and at the steam output as a function of steam flow at the outlet of the pressure reducing turbine 13.

[0038] In an alternative embodiment, a generator is connected directly to the turbine axis (high speed). The high speed generator can operate above 3600 RPM. The voltage is rectified and sent to the grid tie frequency inverter (similar to that of solar energy). A turbine valve is arranged to control the outlet pressure via the PLC Simens signal. Finally, a frequency inverter varies the exported power to keep the turbine rotation constant.

[0039] Figure 6 illustrates a pressure control system that further comprises a complementary system having at least one small pressure reducing valve 22 for extreme operational situations.

[0040] In addition to the components mentioned in the description above, it is evident that a person skilled in the art may require the use of other components such as: directional power relay module, circuit breakers, speed reducers with bushings with forced lubrication, complete oil lubrication, electrical panels as well as protection for them and interface software

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15/17 user graphics capable of managing the components of the pressure control system.

[0041] The following are the topics of variations that may occur in relation to the basic description above:

a) Systems with high speed generator (high frequency) and use of grid tie frequency inverter (the same equipment as solar energy). In this situation, the inverter plays the role of the energy export controller;

b) Turbines that can operate with a frequency inverter and variation in turbine rotation;

c) Turbine with two stages and steam control only in the 1st stage;

d) Turbine with two stages and steam control in two stages;

e) Turbine system with pressure reducing valve, for actuator in conditions of steam operation in the process with operating peaks or to stabilize the system;

[0042] According to the embodiment of the present invention, the temperature of the pressure reducing turbine is between 150 ° C and 400 ° C.

[0043] According to the embodiment of the present invention, the maximum pressure of the pressure reducing turbine is between 1.5 and 30 barg.

[0044] According to the embodiment of the present invention, the power range of the pressure reducing turbine is normally between 3 kW and 990 kW.

FUNCTIONALITY TEST [0045] To measure the pressure reducing turbine's efficiency, the following

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16/17 information, which will be obtained through sensors installed in the system and controllers:

[0046] After starting the pressure reducing turbine, the equipment is kept in operation for at least 3 hours to stabilize all the transient processes of the equipment (to reach the steady state). Each data collection contains information of at least one hour, seeking a constant (stable) stage of the production process. These procedures are carried out at different stages of the production process in order to survey the efficiency scenarios of the pressure reducing turbine according to the process variation (flow variation and steam pressure);

- Measurement of vapor pressure at the entrance of the TRP;

- Measurement of the steam temperature at the entrance of the TRP;

- Measurement of vapor pressure at the TRP outlet;

- Measurement of the steam temperature at the exit of the TRP;

- TRP rotation measurement;

- Vibration measurement;

- Measurement of steam flow;

Thermodynamic calculations are performed to determine the energy available for energy use and efficiency calculation;

P ^ t _and electric

- ( _ftl - h _2s ) * Q (D

Where:

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17/17

Pot. electrical = Electrical power generated and measured in the energy exporting controller [kW] - energy efficiency indicator (valves do not generate energy);

h1 = Enthalpy (tabulated thermodynamic property) of steam at the turbine inlet, as a function of T1 (inlet temperature) and P1 (inlet pressure), considering 100% - [kJ / kg];

h2 = Enthalpy (tabulated thermodynamic property), considering P2 (TRP output pressure) and s1 = s2 (isentropic system) - [kJ / kg];

Q = Steam flow at the TRP outlet [kg / s]

The denominator of the above equation (Ai - Λ2). Q represents the energy that is not used by the reducing valve and that is available for use in the TRP. As the reducing valve does not generate any energy, all energy exported and registered in the export controller (electrical power) will be the benefit of TRP compared to the valve.

- Measurement of exported electrical energy: Energy export controller;

- Comparison of the calculation of the available energy with the exported electrical energy to determine the efficiency of the pressure reducing turbine.

[0047] Although the present invention has been described in connection with a preferred embodiment, it should be understood that it is not intended to limit the invention to that particular embodiment. On the contrary, it is intended to cover all possible alternatives, modifications and equivalents within the spirit and scope of the invention, as defined by the appended claims.

Claims (10)

1. Pressure control system using pressure reducing turbine (13) characterized by the fact that it comprises: steam inlet valves (11) for a pressure reducing turbine (13) having at least one pressure lowering stage controlled by an actuator (12) driven by a signal from a programmable logic controller (16); pressure (14, 17) and temperature (15, 18) vapor sensors arranged respectively at the inlet and outlet of the pressure reducing turbine providing data to the programmable logic controller (16); pressure reduction turbine rotation, flow and vibration sensors (13) providing data to the programmable logic controller (16); where the programmable logic controller (16) receives data from the pressure, temperature and flow sensors, comparing them with desired values and sending control signals to an actuator (12) of the steam intake valves (11) and to a controller energy export (19); where the energy export controller supplies electrical power to the power input of the control system or electrical network; in which the pressure reducing turbine (TRP) (13) consists of a steam turbine generator controlling the steam pressure, performing the same operational function as a pressure reducing valve and using the pressure drop for the generation of Petition 870190070572, of 7/24/2019, p. 30/37 2/3 electrical energy based on the enthalpy difference between the steam inlet and outlet. 2. Control system, according to the claim 1, characterized by the fact that it also comprises valves arranged between two or more pressure lowering stages, being controlled by the actuator (12). 3. Control system, according to the claim 1, characterized by the fact that it also comprises a complementary system with at least one pressure reducing valve to act in parallel or in series with the turbine, aiming to maximize the energy reuse (22). 4. Control system, according to the claim 1, characterized by the fact that it comprises a second control option, in which the energy export controller is replaceable by a frequency inverter, in turbines operating without a speed reducer, with generators operating at speeds above 3600 RPM. 5. Control system, according to the claim 1, characterized by the fact that the maximum temperature of the pressure reducing turbine is between 150 ° C and 400 ° C. 6. Control system, according to the claim 1, characterized by the fact that the maximum pressure of the pressure reducing turbine is between 1.5 and 30 barg. 7. Control system, according to the claim 1, characterized by the fact that the power range of the pressure reducing turbine comprises the range between 3 kW and 990 kW. 8. Control system, according to the claim 1, characterized by the fact that the Petition 870190070572, of 7/24/2019, p. 31/37 3/3 pressure is arranged in parallel or in series with a pressure reducing valve. 9. Pressure control method in a pressure control system as defined in any of the claims 1 to 8 characterized by fact in what comprises the steps of: - to detect a value pressure measured in terminals in turbine outlet through of a pressure sensor o (17 ); - to compare the value pressure measured at output with one desired pressure value at the outlet through a controller (PLC) (16); - adjust through a power export controller (19) in communication with the controller (PLC) (16) an exported power value based on the pressure difference obtained by the PLC controller; - send through the energy export controller (19) a signal to the PLC controller (16), which in turn sends a signal to an actuator (12) coupled to the turbine steam inlet valve (11) (13) , adapting to the signal from the PLC controller (16) and the desired pressure at the output; and 10. Method, according to claim 9, characterized by the fact that the step of detecting a measured value at the turbine outlet further comprises detecting the temperature or flow of the steam.