As the core hydraulic control unit of large power equipment such as steam turbines and gas turbines, the oil quality of the EH fire-resistant oil system directly affects the safety and response accuracy of the unit. Since fire-resistant oil has strong hygroscopicity, the presence of water will accelerate the deterioration of the oil, leading to problems such as increased acid value and decreased resistivity. The bypass regeneration and dehydration device purifies the oil through continuous circulation, becoming a key link in maintaining the stability of oil products. Among them, the DQ9300-6EBC-2V/DF dehydration type regeneration filter element is the core component of the device, and its performance directly affects the dehydration efficiency and operation economy of the system. However, under actual working conditions with large humidity fluctuations, the adsorption capacity and regeneration capacity of such filter elements often show nonlinear attenuation, and it is urgent to explore the law of performance degradation to guide the optimization of operation and maintenance strategies.

1. Structure and working principle of dehydration type regeneration filter element

The DQ9300-6EBC-2V/DF EH oil regeneration filter element adopts a multi-layer composite structure design. The core functional layer is composed of molecular sieve adsorption materials with high specific surface area, supplemented by a glass fiber pre-filtration layer and a metal mesh support structure. Its working process is divided into two stages:

Adsorption stage: When wet oil flows through the filter element, the molecular sieve captures free water and dissolved water in the oil by physical adsorption. The adsorption capacity is related to the material porosity, ambient temperature and oil flow rate.

Regeneration stage: When the adsorption is close to saturation, the system starts the heating regeneration program, desorbs the adsorbed water by hot nitrogen purge, and restores the activity of the filter element.

Under an ideal constant humidity environment, the adsorption-regeneration cycle of the filter element can maintain stable efficiency for a long time. However, in actual operation, due to fluctuations in ambient humidity (such as temperature difference between day and night, seasonal climate change or local steam leakage caused by unit load fluctuations), the filter element will be subjected to dynamic adsorption loads, accelerating performance degradation.

2. The mechanism of humidity fluctuations on filter element performance

Humidity fluctuations cause EH oil filter element performance degradation through the following three paths:

Structural fatigue of adsorption materials

Frequent humidity changes force molecular sieves to undergo repeated expansion-contraction cycles. When the ambient humidity rises suddenly, the adsorption material absorbs a large amount of water in a short period of time, resulting in lattice expansion; and when dehydrated at high temperature in the regeneration stage, the lattice shrinks sharply. This periodic stress will gradually destroy the microporous structure of the molecular sieve, resulting in a reduction in the effective adsorption area.

Marginal decrease in regeneration efficiency

In a humidity fluctuation environment, the filter element is often in a non-saturated adsorption state. For example, when the ambient humidity suddenly decreases, part of the adsorbed water may diffuse inversely due to the concentration gradient, forming a “false saturation” phenomenon. At this time, if the regeneration program is started, the desorption efficiency will be significantly reduced due to insufficient actual adsorption, and energy will be wasted. Incomplete regeneration under this non-steady-state condition will accumulate undesorbed water and gradually block the pores of the material.

Intensification of interfacial effects

Severe changes in humidity will change the oil-water interfacial tension and promote the aggregation of tiny water droplets on the surface of the filter material. Especially in the low temperature and high humidity stage, emulsified water may precipitate from the oil. These micron-sized water droplets can easily penetrate the pre-filtration layer and directly impact the molecular sieve functional layer, accelerating deep pollution.

3. Stage characteristics of performance decay

Through the tracking and analysis of the actual operation data of the power plant, the performance decay of the DQ9300-6EBC-2V/DF filter element in a humidity fluctuation environment shows a three-stage law:

1. Initial stable period (0-800 hours)

The filter element is in the best working state, and the adsorption efficiency is maintained at more than 95%. Humidity fluctuations mainly affect the short-term dehydration rate, but the structural integrity of the molecular sieve is not damaged, and the performance can be fully restored after regeneration.

2. Mid-term decay period (800-2000 hours)

The adsorption efficiency decreases at a rate of 1.5%-2% per month, and the regeneration energy consumption increases by about 30%. At this stage, the molecular sieve has local pore collapse, and the adsorption isotherm shifts to the low humidity zone, which is manifested as a weakened capture ability for trace moisture (<100ppm).

3. Late failure period (>2000 hours)

The adsorption efficiency drops sharply to below 70%, and the regeneration program cannot restore the effective capacity. Electron microscope observations showed that cracks appeared on the surface of the molecular sieve particles, and some areas underwent glass transition due to repeated thermal stress, completely losing their adsorption activity.

The performance degradation of the DQ9300-6EBC-2V/DF dehydration regeneration filter element is strongly correlated with the amplitude and frequency of humidity fluctuations. Its degradation is essentially the result of the coupling of physical damage to the adsorption material under dynamic load and the decrease in chemical activity. Through the coordinated application of material innovation, system control optimization and predictive maintenance strategies, the service performance of the filter element in complex humidity environments can be significantly improved, providing technical support for the long-term stable operation of the EH fire-resistant fuel system.

When looking for high-quality, reliable steam turbine oil filters, YOYIK is undoubtedly a choice worth considering. The company specializes in providing a variety of power equipment including steam turbine accessories, and has won wide acclaim for its high-quality products and services. For more information or inquiries, please contact the customer service below:
E-mail: sales@yoyik.com
Tel: +86-838-2226655
Whatsapp: +86-13618105229

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