Wastewater

Solvent Recovery and Separation

Oil sands processing in Northern Canada utilizes a variety of solvents and naphtha to assist in the separation of the Bitumen from the water and sand. These fluids can help promote chemical reactions, accelerate processing time, and reduce processing costs. Many of these
must recovered due to their high costs, importance of water recovery, or issues associated with release of the chemicals to the environment.

Issues Associated with Oil Sands Processing

• The sand that is separated is very abrasive and can cause excessive wear. Devices that accelerate flow or cause impingement will wear very rapidly.
• Bitumen and froth are not well suited for heating in traditional heating devices due to issues with pressure drop, abrasion, and plugging/fouling.
• Solvents sometimes require high temperatures for processing yet can be very unstable and flash in the pipe if temperatures are not controlled properly.

PSX Heater Solution

The PSX heater can be installed to heat up the process fluid prior to the flash vessel or recovery tank, and has a high heating capacity and can achieve up to a 250 °F temperature rise in a single pass. For difficult to pump slurries or unstable solvents, the PSX heater can be arranged in a Multi-stage configuration to stage the heating to optimize the process. The key to efficient, safe, and predictable steam injection is to inject steam at sonic velocity to achieve choked flow. By achieving choked flow, sonic velocity conditions can be achieved for steam injection. All steam injectors need to operate in a choked flow manner for good, non-violent mixing. The PSX heater is an internally modulated heater that varies the mass flow rate of steam by changing the area in which the steam may pass. This type of modulation allows the full steam pressure to always be present at the point of injection regardless of plug position. Flow rates can range from 1 – 10,000 gpm.

Key PSX Heater Direct Steam Injection Benefits

• Eliminate Process Upsets as the internal steam control design of the PSX heater controls the steam mass flow and not the steam pressure thus eliminating steam hammer and vibration issues.
• Lower maintenance due to the PSX heater’s self cleaning design (no scaling or plugging/fouling).
• Low pressure drop (typically 1-2 psig) reduce pump integration issues and flow disruptions, and provides energy savings by lowering slurry pump demand.
• Improved temperature control (typically +/- 1 °F ) allows for a more reliable heating process.
• Improved Reliability as a variety of alloys and wear coatings are available to address wear issues.

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Sludge Heating

Inline process heating with Direct Steam Injection has multiple applications in a variety of process and utility applications. Many applications such as mineral processing, pulp and fiber slurry pre-treatment, oil sands mining and others are not well suited for traditional methods of heating. Typical challenges encountered are corrosive fluids, abrasive particulate, viscosity changes, plugging and fouling, eating for water, slurry, sludge, and aggressive fluid heating applications. Direct Steam Injection for Inline Heating is a very good choice for a variety of applications. One of the fundamental principals for efficient and reliable steam injection is the ability to produce and deliver high velocity steam. High velocity steam is what assures rapid and complete condensation and mixing of the steam in the fluid.

Internally Modulated Steam Control – ProSonix’s unique method of steam injection utilises an internal steam control to precisely deliver the appropriate mass flow of steam, and not the pressure, for the required heating. This is achieved via and integral pneumatic actuator, and a variable position stem plug in the steam jet diffuser. We do not throttle or regulate steam pressure. This design offers a precise method of steam control through a choked flow control delivery of the steam. ‘Choked flow’ is the phenomenon of accelerating a vapor to maximum velocity by creating a pressure differential through an engineered nozzle. By establishing choked flow, the steam mass flow can be metered to precisely control the heating of the liquid. This produces predictable results based on the position of the stem plug. Through a variable area steam diffuser, steam flow is metered at the point where steam and liquid first contact and mix. Internally Modulated DSI heating controls the mass flow of the steam and not the pressure.

Advantages with Multi-Stage DSI Heating

• Eliminate process upsets as some fluids and slurries because of their hi-viscosity/hi-solids are not receptive to large volumes of steam addition. Splitting the heating load can result in improved steam condensation eliminating steam hammering (cavitation) and excessive wear
• The PSX inline heater can be designed to match the slurry design flow velocities eliminating flow disruptions, accelerated flow velocity areas and maintaining solids in suspension
• Rapid and complete condensation of the steam allows for more reliable temperature control of up to +/- 1°F (-17°C)
•  High velocity steam is self cleaning and eliminates issues associated with plugging and fouling along with scale and mineral build-up
• Lower maintenance costs as proper condensation of the steam eliminates excessive wear, thus improving equipment reliability and life
• Typically 1-2 psig reduces slurry pump demand which reduces energy consumption

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Anaerobic Digestion

More and more agricultural and dairy farms as well as beef, hog and poultry operations are considering the use of anaerobic digestion for biogas production. These operations typically produce a significant amount of organic matter in the form of manure. Anaerobic digestion is a biological process that breaks down organic solids. Manure can be processed in anaerobic digesters and the byproduct is methane gas. The methane gas can be captured, stored and used to run electrical generators and boilers for use in the farm operations. Heat exchangers can face the following challenges when heating sludge:

• Live steam used to provide heat for heat exchangers creates hot spots where sludge can burn and build-up plugging the heat exchanger tubes. This increases maintenance costs and an increased pressure drop across the heat exchanger
• Upgrading from mesophillic to thermophilic often require multiple heat exchangers in series to achieve the necessary temperature rise
• Increased pressure drop adds demand to the sludge pumps thus increasing energy usage
• Temperature control problems can be present as there is a lag time from slurry entering and then being discharged

To overcome these challenges, Direct Steam Injection (DSI) is a very good approach. There are correct ways to apply DSI and approaches that may not produce desirable results. One of the key factors to successful DSI is to inject steam at sonic velocity to achieve choked flow.

Spargers, Fixed Eductors &Venturi Style DSI

These units use a fixed nozzle to inject steam. Steam control is attempted via an externally modulated steam control valve. With an externally modulated steam injecton the steam pressure is adjusted to control the flow rate of steam with a control valve.

Problems arise when the steam pressure has dropped to a point where the steam flow is no longer choked. This can be seen most often at start up and shutdown of externally modulated steam injectors in the form of noise, vibration and hammering. With an external steam valve, there is always a pressure drop before the steam reaches the injector.

The use of external steam control devices to control the steam flow by modulating the steam pressure can lead to excessive steam hammering and vibration. Steam hammering and vibration often result from poor mixing and condensing of the steam. As temperature demand drops, steam pressure drops, lowering the steam velocity and potentially causing instability. Uncondensed steam bubbles will typically collapse when it comes in contact with a cold pipe wall in the liquid piping. When these bubbles collapse, the slurry rushes in to fill the void and impacts the pipe wall. In some cases this will result in some pinging noise and in severe cases, steam hammering and vibration.

PSX DSI Heater Solution

The PSX heater uses a unique method of steam injection via an integral steam control device. The key to efficient, safe and predictable steam injection is to inject steam at sonic velocity to achieve choked flow. All steam injectors need to operate in a choked flow manner for good, non-violent mixing. The PSX heater is an internally modulated injection heater that varies the mass flow rate of steam by changing the area through which the steam may pass. This type of modulation allows the full steam pressure to always be present at the point of injection regardless of the plug position. The PSX heater has an integrated Pneumatic Actuator that allows the engineered steam diffuser opening to vary according to the temperature demand.

Flow rates can range from 1 – 5,000 gpm. The PSX heater has a high heating capacity and can achieve a temperature rise of up to 250°F (121°C) in a single pass through the heater.

Key PSX Heater Direct Steam Injection Benefits

• Stable operation due to the internal steam modulation design which controls the steam mass flow and not the steam pressure thus eliminating steam hammering and vibration issues
• Low maintenance due to the PSX heater’s self cleaning design
• Low pressure drop reduces demand on the sludge pumps lowering energy costs
• Better temperature control allows for a more reliable heating process (typically +/- 1%)
• Reduced installation and operational costs with the elimination of the condensate return system
• Direct mechanical control of the steam injector allows for linear process heating control
• Control is maintained by the plant PLC/DCS or local controller with no proprietary software required
• PSX heater can be installed in the piping requiring no floor space

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