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CN-122015366-A - Condensing pressure reference control method and device for ammonia absorption refrigeration system

CN122015366ACN 122015366 ACN122015366 ACN 122015366ACN-122015366-A

Abstract

The invention discloses a condensing pressure reference control method and device for an ammonia absorption refrigeration system. The method comprises establishing an absolute physical reference-target condensing pressure determined by ammonia physical properties The value is uniquely determined at a given condensing temperature, and the condensing pressure is detected in real time ; To Approach to To achieve this, the operating parameters of the ammonia purification device are adjusted so that the purity of the ammonia vapor entering the evaporator approaches 100%. The device is an electronic control or self-operated machine. Based on the double rigid constraint of ammonia filling amount fixation and condensation pressure determination, the condensation pressure is raised to an active physical reference, so that the system automatically approaches to a theoretical optimal state in a wide temperature area, the rectification fault risks of flooding, a tower flushing and the like are obviously reduced, the energy efficiency is improved, and the method is suitable for industrial waste heat recovery, refrigeration houses and the like.

Inventors

  • ZHANG HUI

Assignees

  • 张晖

Dates

Publication Date
20260512
Application Date
20260315

Claims (10)

  1. 1. A condensing pressure reference control method for an ammonia absorption refrigeration system, comprising the steps of: (1) Determining an absolute physical reference, target condensing pressure, determined by the physical properties of ammonia The target condensing pressure has a uniquely determined value at a given condensing temperature; (2) Detecting absolute pressure in condenser in real time ; (3) At the condensing pressure Approach to For control purposes, the operating parameters of the ammonia purification device are adjusted to bring the purity of the ammonia vapor entering the evaporator to approximately 100%.
  2. 2. The method of claim 1, wherein the target condensing pressure Is determined by the saturated vapor pressure of pure ammonia at the condensation temperature, the designed condensation temperature of the ammonia refrigeration system is not suitable to be higher than 40 ℃ according to the national standard GB50072-2021, and the target condensation pressure is within the range of the standard design working condition Is uniquely determined by the ammonia saturation pressure corresponding to the actual condensation temperature.
  3. 3. The method according to claim 1, wherein the adjusting the reflux ratio of the rectifying column means adjusting the reflux amount or the cooling capacity of the reflux condenser.
  4. 4. A condensing pressure reference controller for implementing the method of any one of claims 1-3, comprising: (a) The pressure detection unit is arranged at the condenser and used for detecting the absolute pressure in the condenser in real time ; (B) A reference unit for providing a target condensing pressure A corresponding reference signal; (c) The comparison unit is connected with the pressure detection unit and the reference unit, receives the pressure signal and the reference signal and outputs a pressure deviation signal; (d) The execution unit is connected with the comparison unit and is used for adjusting working condition parameters of the ammonia purification device according to the pressure deviation signal so as to enable the ammonia purification device to have Approach to 。
  5. 5. The controller of claim 4, wherein the execution unit is any one of: The electric regulating valve is arranged on a cooling water supply pipeline of the reflux condenser, and the flow rate of cooling water is regulated by the PID controller to indirectly change the reflux ratio; the variable frequency pump is used for adjusting the rotating speed of the reflux pump and directly changing the reflux quantity; the self-operated differential pressure driving valve is arranged on a reflux liquid pipeline of the rectifying tower and is respectively communicated with a condenser pressure sampling point and a rectifying tower top pressure sampling point through a pressure guide pipe, a valve core overcomes spring force displacement under the action of differential pressure, reflux liquid flow is directly regulated, and the pre-tightening force of the spring corresponds to the pressure difference between the condenser and the rectifying tower top under the full-load design working condition.
  6. 6. The controller of claim 4, further comprising a purity monitoring unit having an ammonia-water solution thermophysical database built therein, based on real-time condensing pressure And calculating the current ammonia vapor purity by the condensation temperature, and triggering an alarm or assisting the purification device when the calculated purity is lower than a preset threshold value.
  7. 7. An ammonia absorption refrigeration system comprising a controller according to any one of claims 4 to 6, wherein the system automatically adjusts the reflux ratio of the rectifying column based on the condensing pressure as an absolute physical basis such that the purity of ammonia entering the evaporator is always near 100%.
  8. 8. The system of claim 7, wherein the system is a single, dual or multi-stage ammonia absorption refrigeration system or retrofitted with the controller for an inventory unit.
  9. 9. The system of claim 7, wherein the system maintains the ammonia purity through adaptive adjustment over a wide evaporation temperature range, ensuring that the evaporator does not freeze and the rectifying column does not flood.
  10. 10. The system of claim 7, further comprising a real-time on-line monitoring and data output unit that is responsive to real-time condensing pressure And the condensation temperature calculates the current ammonia vapor purity and the system energy efficiency (COP), and continuously outputs the current ammonia vapor purity and the system energy efficiency (COP) through a communication interface to form a traceable operation data record, and provides a real data support for carbon transaction and green building authentication.

Description

Condensing pressure reference control method and device for ammonia absorption refrigeration system Technical Field The invention relates to the technical field of control of absorption refrigeration systems, in particular to a control method and a device for realizing purity self-adaption by adjusting reflux ratio of a rectifying tower by taking condensing pressure as a physical reference. Background The ammonia absorption refrigeration system is driven by heat energy, can utilize low-grade waste heat, has wide refrigeration temperature range, and is widely applied to refrigeration houses, petroleum smelting and other chemical processes. Unlike lithium bromide-water systems, ammonia-water systems present a fundamental technical challenge in that the vapors generated during the generation must contain water vapor due to the standard boiling point difference of ammonia (boiling point-33 ℃) and water (boiling point 100 ℃) of only 133.4 ℃. The residual water content in the distillate determines the evaporation/absorption pressure, and if the water content is too high, the system COP is reduced, and serious faults such as evaporator icing, rectifying tower flooding (flooding, flushing tower) and the like are even caused. In the prior art, the purification of ammonia vapor is mainly realized through a rectifying tower. The rectifying tower is a multivariable strong coupling system, the separation effect of which is influenced by a plurality of factors such as cooling water temperature, reflux ratio, feeding flow, feeding concentration, tower plate number, generating temperature and the like, and the control is extremely complex. Studies have shown [1-3] that the performance of the rectification column directly affects ammonia vapor purity and overall system efficiency, and that there is an optimal reflux ratio and optimal generation temperature to maximize system COP. However, the existing researches only disclose the rule of influence of each parameter on the system performance, and a control method capable of adaptively adjusting the system parameters in actual variable working condition operation is not provided. In actual operation, the system deviates from the design working condition due to the change of the heat source temperature, the cooling water temperature and other factors, so that the rectifying tower cannot always operate in an optimal state, and faults such as flooding and the like are caused, thereby seriously affecting the system efficiency and stability. Therefore, the ammonia absorption refrigeration system control method taking physical parameters as absolute physical references is provided, so that the system can adapt to heat source and environmental changes, the ammonia purity is fundamentally ensured, rectification faults are avoided, and the method has important theoretical value and engineering significance. Disclosure of Invention The invention provides a condensing pressure reference control method and device for an ammonia absorption refrigeration system, and aims to solve the problems that in the prior art, a rectifying tower is difficult to control by multivariable coupling, flooding faults are easy to occur, and system efficiency is greatly influenced by working condition fluctuation. 3.1 Physical basis of the invention The physical basis of the present invention lies in two rigid constraints: Restraining the first step, fixing the filling amount of ammonia. The ammonia quantity injected at one time can not be changed in operation during system installation, which is a rigid constraint on the material conservation level, so that the condition of the purification device can be regulated to influence the system state. And secondly, the condensing pressure is determined by the temperature of cooling water. The saturation vapor pressure of pure ammonia is uniquely determined at a given condensing temperature. When water is mixed into the ammonia vapor, the partial pressure of ammonia decreases, resulting in a decrease in condensing pressure. Therefore, the level of condensing pressure directly reflects the purity of the ammonia vapor. Under these two constraints, the present invention proposes that the condensing pressure is taken as an absolute physical reference when the condensing pressureBelow a reference valueWhen the ammonia vapor is mixed with water and has insufficient purity, the ammonia vapor is mixed with waterBack up toAnd when the purity reaches the standard, the purity is indicated. 3.2 Design-operation unified control concept The invention follows the core concept of 'design decision basis, running self-adaption'. In the system design stage, determining the reflux ratio of the rectifying tower for optimizing the system performance according to the target working conditions (such as the condensation temperature of 40 ℃ and the evaporation temperature of-15 ℃), and the likeAnd obtain the corresponding reference value of condensing pressure under the working condition(Det