Slurry density meter · PS7000

Online Density Measurement for the AFT Tower (High-Concentration Desulfurization Slurry Processing Tower)

Flue-gas desulfurization in power plants

In the AFT tower, measuring the density of high-concentration, high-viscosity, and easily crystallizing slurries has long been a challenge. The PS7000 acoustic impedance concentration meter, employing non-contact measurement, overcomes the failures of conventional instruments caused by clogging, wear, and crystallization, enabling real-time, continuous monitoring of slurry density and automated control of the discharge process, thereby ensuring stable system operation.

Applicable industries
Power Emission Control
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Online Density Measurement for the AFT Tower (High-Concentration Desulfurization Slurry Processing Tower)

I. Process Background

The AFT tower is a key piece of equipment in power plant flue-gas desulfurization and deep treatment systems for desulfurization wastewater, commonly used for the circulation, absorption, and concentration of high-concentration desulfurization slurry, as well as for pretreating by-product salt crystallization. In a typical process, high‑temperature flue gas (or process gas) enters from the bottom of the tower and comes into countercurrent contact with the slurry sprayed down through multiple stages inside the tower. The slurry at the tower bottom is repeatedly pumped back to the spray layer by a circulation pump, creating intense gas–liquid mass transfer that gradually concentrates the slurry to a high‑density range of 30% to 60%. When the slurry density at the tower bottom reaches a set value, it must be promptly discharged to downstream crystallizers and centrifuges to precipitate and remove the by‑product salt crystals.

The slurry in this section exhibits extreme characteristics—high concentration, high viscosity, high abrasiveness, and a strong tendency to crystallize at the measurement interface. Real‑time, continuous, and reliable monitoring of the slurry density in the tower bottom circulation loop is the core basis for the safe operation of the AFT tower and the automation of the discharge process.

II. Pain Points of Traditional Density Measurement Solutions

• High‑viscosity slurry: Differential pressure instruments’ impulse lines are highly prone to blockage, making stable operation nearly impossible.

• Crystallizing media: The slurry rapidly forms crystals at the measurement interface when the temperature changes, coating the sensor surface and causing “false high” readings or even complete failure.

• Highly abrasive conditions: Hard, suspended particles in the slurry quickly wear down contact probes, resulting in extremely short service lives.

• Wide measurement range: From about 20% at the start of circulation to around 60% during discharge, a single instrument must cover this broad span, a challenge traditional meters struggle to meet while balancing accuracy and range.

• Gamma‑ray concentration meters face mounting safety, compliance, and maintenance‑cost pressures; power plants generally prefer non‑nuclear solutions for new projects.

III. PS7000 Solution

The PS7000 is installed on the discharge line of the AFT tower’s bottom slurry circulation pump, using a non‑contact acoustic impedance method to measure slurry density. When the PS7000 detects that the tower bottom density has reached the process setpoint (e.g., 50%), it sends a discharge‑trigger signal to the DCS, automatically opening the discharge valve to send the high‑density slurry to downstream crystallizers. Once the density drops back to the process lower limit, discharging ceases, achieving fully automated closed‑loop control of slurry circulation and discharge.

Online Density Measurement for the AFT Tower (High-Concentration Desulfurization Slurry Processing Tower)

Figure 4: Schematic diagram of online density measurement and discharge control in an AFT tower (high‑concentration desulfurization slurry treatment tower)

Key Technical Advantages of the PS7000 in This Process Condition

▸ The linear frequency-modulated Chirp algorithm maintains stable echo‑analysis performance even for highly viscous, high‑concentration slurries;

▸ A single unit covers the entire range from 0 to 3,000 kg/m³ (approximately 0 to 80% concentration), eliminating the need for multiple instruments operating in tandem;

▸ The non‑contact ceramic probe fundamentally addresses the three major challenges of crystallization encrustation, wear, and clogging;

▸ The high‑temperature model can accommodate medium temperatures up to 120°C, making it suitable for applications in the AFT tower sump where medium temperatures are relatively high;

▸ An explosion‑proof ExdⅡCT6Gb option is available, meeting the explosion‑proof requirements for flue‑gas desulfurization wastewater treatment and areas containing SO2, NH3, and other hazardous substances;

▸ Slurry density data drives the discharge valve interlock logic, ensuring stable feed density into the crystallizer and significantly improving the separation efficiency of downstream centrifuges.

IV. Customer Value

Comparison Dimensions

Conventional/Nuclear Source Solutions

PS7000 Solution

Measurement Range Coverage

Multiple instruments are required for segmented measurement

0–80% single-unit coverage

Crystallization/Blockage Mitigation

Frequent crystallization failures

Non-contact · Unaffected

Automated Discharge

Reliance on human experience-based judgment

Density interlock automatic discharge

Operational Safety

Radiation safety management and control

Intrinsically safe with no radiation

Mold Feed Stability

Large fluctuations · Affect crystal particle size

Stability · Improved by-product salt quality

In a certain salt chemical–power plant cogeneration project in Qinghai, the potassium chloride slurry in the AFT tower bottom was near saturation, with a crystal content of 30% to 40% and a temperature fluctuating between 5°C and 20°C. After the PS7000 was put into operation, two weeks of continuous comparative testing showed that its readings consistently agreed with laboratory measurements within a deviation of 0.5% to 0.8%, with no anomalies even during peak concentration periods, fully validating its high accuracy and reliability under extreme conditions such as those in the AFT tower. This solution has now been adopted by several power plants in similar projects as a standardized approach for density measurement in high‑concentration desulfurization slurry treatment towers.

More applications for Slurry density meter

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Online Measurement of Gypsum Slurry Density in Absorption Towers

In the wet flue-gas desulfurization process, real-time monitoring of gypsum slurry concentration is crucial for ensuring the quality of the by-product gypsum and the proper operation of equipment. However, conventional concentration meters—such as mass flow meters, tuning fork sensors, and differential pressure concentration meters—suffer from issues like radiation safety concerns, bubble interference, and scaling. Pisonics’ PS7000 employs ultrasonic technology for non-contact measurement, can penetrate bubble layers to deliver stable and reliable concentration data, and requires no maintenance, with a service life exceeding five years.

Online Density Measurement for Limestone Slurry Preparation

During the preparation of limestone slurry, conventional density-measurement solutions suffer from issues such as wear and scaling, leading to inaccurate data and compromising flue-gas desulfurization efficiency. The PS7000 acoustic impedance concentration meter overcomes these challenges through non-contact ultrasonic measurement, delivering stable, high-precision online density monitoring and ensuring consistent control of slurry concentration.

Online Measurement of Desulfurization Wastewater Density

In the flue-gas desulfurization process at power plants, online monitoring of the slurry density in the underflow from the thickener is critical. Conventional contact-type instruments are prone to scaling and corrosion, making it difficult to meet the demands of long-term, stable operation. Pisonics’ PS7000 acoustic impedance concentration meter employs a non-contact ceramic probe and a corrosion-resistant lining, effectively addressing severe corrosion and fouling while ensuring the accuracy and stability of the measurement data.

Online Measurement of Slurry Density in Non-ferrous Metallurgical Beneficiation Plants

In nonferrous metal concentrators, fluctuations in slurry density directly affect metal recovery rates and energy consumption. The PS7000 concentration meter employs ultrasonic non-contact measurement technology and features a flanged direct‑insertion installation, eliminating the wear and fouling issues common to conventional instruments, ensuring long‑term stable operation, and operating entirely without radiation, thus obviating the need to obtain a Radiation Safety License.

Selection support

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Comparisons

Voices from users of this product

"Our original tuning fork and differential pressure meters on the absorber gypsum discharge main had recurring problems with bubbles and scaling — we had to shut down weekly to clean them. After switching to PS7000, both problems disappeared. Basically maintenance-free now, accuracy is stable, and it fully meets our FGD process control needs."

Thermal Control Foreman Wang
Thermal Control Specialist
A certain thermal power plant in Inner Mongolia

"After switching to the PS7000, our overflow density readings finally stabilized — we stopped tuning reagent dosing by feel. The unexpected win was not having to clean the sensor weekly; our previous radiometric meter needed window-wiping almost daily in the scaling slurry."

Director Li
Mineral Processing Workshop Director
A certain copper mining enterprise

"Our potash blending tank is a harsh environment — KCl near saturation, 30~40% crystal content, temperature swinging 5~20°C. Traditional density meters can't hold up here. After two weeks of PS7000 service, the deviation from manual lab samples stayed in the 0.5~0.8% range, even during concentration peaks. No anomalies."

Director Xie
Process Engineer
A potash fertilizer plant in Qinghai

FAQ

Is the PS7000 ultrasonic density meter a radiometric device? Does it need a radiation license?

The PS7000 is an acoustic-impedance ultrasonic density meter with no radioactive source whatsoever. No radiation license is required. It uses only piezoelectric transducers to send and receive ultrasonic signals — the same physical principle as medical and NDT ultrasound.

If you're currently using a Cs-137 / Co-60 source-based meter and want to remove the regulatory burden, PS7000 is a drop-in alternative. We also offer the PS7500 gamma meter, which uses an exempt-activity Na-22 source (< 1000 KBq) — also requires no radiation license.

Can PS7000 really measure stably in bubbly mining slurries?

Yes.

The PS7000 employs a linear frequency-modulated (Chirp) acoustic impedance algorithm—after transmitting a broadband ultrasonic pulse, the host unit analyzes the echo signal in the frequency domain, and multiple-reflection interference caused by bubbles is identified and eliminated by the algorithm. This is the core difference between the PS7000 and conventional reflective ultrasonic density meters: traditional single-frequency reflection is highly sensitive to bubbles, whereas the PS7000’s Chirp algorithm is virtually immune to them.

At the gypsum discharge line of an absorption tower in a thermal power plant in Inner Mongolia (under conditions of continuous air oxidation that generate dense bubbles), the PS7000 has been operating stably for several years after replacing the original tuning fork concentration meter.

What installation requirements does the PS7000 have?

The installation requirements for the PS7000 flanged direct-insertion type are as follows:

  1. Straight-run pipe sections: ≥5D (upstream) + 2D (downstream), where D is the nominal pipe diameter;
  2. The installation point must operate with a full pipe to avoid stratification of gas and liquid phases;
  3. The applicable pipe sizes range from DN50 to DN1000 (larger sizes can be customized);
  4. The flanges are compatible with ANSI/DIN/JIS standards;
  5. In highly abrasive conditions, it is recommended to use a 316L probe with special ceramics or a 2205 duplex stainless steel probe;
  6. In strongly corrosive environments, a PTFE-lined option is available.

If the pipeline does not allow for tapping, please consider the PS7010 clamp-on type instead.

PS7000 vs nuclear density gauges: which costs less over the life cycle?

On purchase price alone, ultrasonic and nuclear gauges sit in a similar bracket. The gap opens over 5 to 10 years of ownership.

Hidden cost list of a Cs-137 / Co-60 nuclear gauge:

  • Radiation safety licensing and annual reviews, plus operator training and certification;
  • Licensed transport and installation filing for the source;
  • Dose monitoring and record keeping during service;
  • Source replacement as activity decays (purchase, transport, commissioning, return of the old source);
  • End-of-life disposal of the spent source — often the single largest bill.

PS7000 acoustic-impedance ultrasonic gauge: no radioactive source and no permits of any kind; non-contact sensor with zero wear and zero clogging, sensor life of 5 years or more, virtually maintenance free with no consumables. Power plant, potash and iron ore sites have run 2+ years at near zero maintenance.

Bottom line: on a 5-year basis the total cost of ownership of the PS7000 is typically far below a nuclear gauge. Where a nuclear principle is genuinely required (such as dense-medium coal washing), the PS7500 with an exempt-activity Na-22 source needs no license, though the roughly 2.6-year half-life still implies periodic source renewal.