Wastewater Evaporators for the Food and Dairy Industry

Quick links for this page:

Evaporation plants are used as thermal separation technology for the concentration or separation of liquid solutions, suspensions and emulsions.

GEA Process Engineering Inc. has extended its expertise in thermal separation technology to concentrating waste waters, and effluents, leaving food and dairy processing facilities.

This extensive technical know-how has naturally developed from research and development work, and from the operation of our multipurpose reference evaporators. The correct solution, employing efficient energy use strategies, for most products, operating conditions, and applications have been developed and proven.

The two main evaporator concepts we use when working with effluents are

  1. falling film evaporators, and
  2. forced circulation evaporators

Falling Film Evaporators

Design

A vertical shell-and-tube heat exchanger, with laterally or concentrically arranged centrifugal separator. The tube chest, top flange assembly (liquid distribution area), and lower part (evaporated vapor disengagement area) is often referred to as a "calandria".

Operation

The liquid to be concentrated is supplied to the top of the heating tubes and distributed in such a way as to flow down the inside of the tube walls as a thin film. The liquid film starts to boil due to the external heating of the tubes and is partially evaporated as a result. The downward flow, caused initially by gravity, is enhanced by the parallel, downward flow of the vapor formed. Residual film liquid and vapor is separated in the lower part of the calandria and in the downstream centrifugal droplet separator. It is essential that the entire film heating surface, especially in the lower regions, be evenly and sufficiently wetted with liquid. Where this is not the case, dry spots will result that will lead to incrustation and the build-up of deposits. For complete wetting it is important that a suitable distribution system is selected for the head of the evaporator. Wetting rates are increased by using longer heating tubes, dividing the evaporator into several compartments or by product recirculation.

Features

Best product quality - due to gentle evaporation, mostly under vacuum, and extremely short residence times in the evaporator.

High energy efficiency - due to multiple-effect arrangement or heating by thermal or mechanical vapor recompressor, based upon the lowest theoretical temperature difference.

Simple process control and automation - due to their small liquid content falling film evaporators react quickly to changes in energy supply, vacuum, feed quantities, concentrations, etc. This is an important prerequisite for a uniform final concentrate.

Flexible operation - quick start-up and easy switchover from operation to cleaning, and uncomplicated changes of product.


Forced Circulation Evaporators

Design

A horizontal (or vertical) shell-and-tube heat exchanger or plate heat exchanger ("heater" or "calandria"), with a flash vessel (vapor separator) arranged above, with a product circulation pump.

Operation

The liquid is circulated through the heater by means of a circulation pump, where it is superheated at an elevated pressure, higher than its normal boiling pressure. Upon entering the vapor separator, the pressure in the liquid is rapidly reduced resulting in some of the liquid being flash evaporated, or rapidly boiled off. Since liquid circulation is maintained, the flow velocity in the tubes and the liquid temperature can be controlled to suit the product requirements independently of the pre-selected temperature difference.

Features

Long operating periods - boiling/evaporation does not take place on the heating surfaces. Fouling due to incrustation and precipitation in the "heater" is therefore minimized.

Optimized heat exchange surface - flow velocity in the tubes determined by the circulation rate and tube dimensions.


Evaporator Design Criteria

During the design of evaporator system in general and for dairy effluent evaporators specifically, numerous, and sometimes conflicting, requirements have to be evaluated.

These factors determine the materials of construction and which equipment arrangement is used in the evaporator design.

One of the main problems with effluent evaporation is the fact that the characteristics of the processed products are seldom alike. Effluents bearing the same name often have a unique evaporation characteristics. The most important criteria are as follows:

  • Capacity and operation requirements, including flows, concentration, chemical analysis of the feed and annual operating hours.
  • Site utility costs.
  • Availability of steam, water, power, cleaning chemicals, and any limitations, etc.
  • The feed characteristics, heat sensitivity, viscosity, other flow properties, tendency to foam, inclusion of gases, and so on.
  • The need to test the effluent in a Pilot Evaporator or complete a corrosion study in a GEA facility.
  • Choice of fabrication materials and surface finishes.
  • Site conditions such as available space, indoor or outdoor location, platform requirements, etc.
  • Legal matters including sound emission, height restrictions, and regulatory requirements.
  • The type of control system desired, and the operating principle of the control system

GEA Process Engineering Inc.'s evaporation systems are characterized by high quality and operating efficiency. Attention is paid to the details and the criteria above taking into account individual requirements. It is particularly important that the evaporators delivered by GEA Process Engineering are reliable and easy to operate.


Recent effluent evaporator projects

A summary of recent effluent evaporator projects follows offering a view of our capabilities in processing effluents from dairy processing:

Challenge #1: Reduce Wastewater from Cheese Plant Brining System.

A Customer came forward looking to reduce the costs associated with hauling excess brine from their cheese operation and continuously adding fresh salt.

During operation of the cheese brining system, the volume of water increases in the circulating salt solution. This accumulation also decreases the salt concentration.

As a result, excess brine is hauled from the Dairy facility twice weekly by a waste management company at a high cost, and salt continuously needs to be added to the brine system.

Solution #1: Apply a Niro Forced Circulation Evaporator to remove water

The Customer determined that removing 1000 PPH of water from their brining system would significantly reduce their waste hauling costs and achieve a valuable and rapid payback.

Forced Circulation Evaporator for Brine Concentration
Forced Circulation Evaporator for Brine Concentration

Pilot plant testing was completed to confirm the details of the required evaporator design.

The evaporator would have to have the product contact surfaces be built from Titanium as a brine solution would be very corrosive for a standard stainless steel evaporator.

GEA proposed a fully shop assembled, skid mounted, single effect Forced Circulation Evaporator, complete with motor starters and PLC control system, with thermal vapor recompressor heating. The project was designed, fabricated and delivered in 24 weeks.

Once installed on the customer's site, only electrical power, steam and compressed air needed to be brought to the Evaporator to put it into operation. GEA engineers then travelled to site to commission the evaporator.

The specific solution for this Customer operates under vacuum with a reduced boiling temperature to minimize, if not eliminate, heat treatment of organic materials in the circulating brine system.

 

Challenge #2: Process mixed Effluent with high BOD from a Dairy Plant

A Dairy Customer approached GEA about reducing the volume of liquid waste being hauled from their site. This effluent was being hauled from the facility by a waste management company at a high cost.

Their waste stream consisted of CIP rinse water, filtration system permeate waste, cheese plant cooker water, and waste brine solution. The combination of these materials held a very high electrical conductivity and BOD content generated by a large dairy processing plant.

The Customer required a tight delivery schedule.

Solution #2 - Apply a Niro Compact Evaporator to reduce effluent volume

The customer required a system to evaporate 28,000 pounds per hour of water from their waste stream on a continuous basis, 365 days per year.

GEA Niro Compact Evaporator in the GEA workshop before shipment
GEA Niro Compact Evaporator in the GEA workshop before shipment

A high nickel content stainless steel alloy was selected following a corrosion study as the fabrication material in contact with the effluent processed.

A fully shop assembled, skid mounted, multiple effect short tube Compact Falling Film Evaporator, complete with motor starters and PLC control system, and with thermal vapor recompressor (TVR) heating.

The resulting liquid concentrate was spray dried, therby completely eliminating the BOD effluent from the plant's wastewater stream.

The unit was delivered in less than 16 weeks after order as a complete system with all access platforms, conduit and wiring, pneumatics, and utility distribution piping. Connection of power, connection of utilities and final testing took 10 days to complete after arrival of the evaporator on site.

The unit was immediately started up at full capacity, 18 weeks after order.

 

Challenge #3 - Two effluent streams - One solution

A Customer approached us stating that they had two very different products to manage.

The first effluent stream was from a water treatment membrane plant containing a high electrical conductivity, and high entrained gas content, and the purchaser needed to reduce the volume of the effluent by 90%.

The second effluent stream was from a membrane plant producing whey permeate from a cheese plant prior to crystallization.

Solution #3: Apply a Niro Compact Evaporator to reduce effluent volume.

The Customer had determined that they required 35,000 pounds per hour of water removal from the waste stream on a continuous basis, 365 days per year.

Several options for Niro Evaporators were reviewed with the Customer, specifically targeting investment and utility consumption optimization. Finally a multiple effect short tube Niro Compact Falling Film Evaporator was selected.

GEA designed and fabricated a fully shop assembled, skid mounted, multiple effect short tube Compact Falling Film Evaporator, complete with motor starters and PLC control system, and with thermal vapor recompressor heating.

Multiple Effect GEA Niro Compact Evaporator prior to installation Multple Effect GEA Niro Compact Evaporator
Multiple Effect GEA Niro Compact Evaporator prior to installation Multple Effect GEA Niro Compact Evaporator

GEA delivered unit in accordance with 3A specifications.

 

Challenge #4: Reduce Dairy Effluent with High ph and high Electrical Conductivity.

A Customer approached GEA looking for a solution to reduce wastewater hauling costs.

The facility was hauling large volumes of the effluent at a very high cost by a wastewater management company.

The volume of the effluent had to be reduced by a large factor to make the project viable.

Solution #4: A singe effect Mechanical Vapor Recompression (Turbofan) Evaporator

A GEA Niro Single Effect Mechanical Vapor Recompression Evaporator
A GEA Niro Single Effect Mechanical Vapor Recompression Evaporator

The Customer needed to evaporate 74,000 pounds per hour of water from their waste stream and needed to consistently reduce the wastewater volume by a factor of 20. They required that under certain conditions that the concentration factor be up to 30 times.

The unit was designed to have very high energy efficiency, evaporating 190 pounds per hour of water for every kilowatt consumed by the Turbofan.

GEA designed, fabricated, installed and commissioned a multiple pass single Effect Mechanical Vapor Recompressor (Turbofan) Heated Falling Film Evaporator.

High tube wetting rates are employed to minimize fouling of evaporative surface areas, allowing the system to operate over long periods of time before cleaning is required.

Another unique feature of this system is that no cooling water is needed during operation.

 

Challenge #5: Capture recoverable by-products from Soy Processing Effluent

A Customer approached GEA stating that they had effluent from a Soy Processing Facility containing recoverable by-products.

The discharge volume from the existing process was very high, more than 440 GPM holding approximately 2% total solids. The Customer wanted to recover these valuable solids.

Engineering studies confirmed that the use of an evaporation system to capture the by-product would also eliminate the need for the owner to increase his wastewater system as the distillate (condensate) produced from the evaporator would be recycled back as clean water into the upstream processes.

Solution #5: A MultipleEffect MVR Evaporator to concentrate high value solids

A "Multiple Turbofan Mechanical Vapor Recompressor Heated Falling Film Pre-Evaporator" acting as single effect system coupled to a single effect "Forced Circulation Thermal Vapor Recompressor Heated High Concentrator" was supplied.

The evaporator installation was designed to operate with a concentration ratio in excess of 20, and typically operates with a concentration ratio in excess of 25. The design evaporation rate of the unit is 215,000 PPH.

The Turbofan heated Pre-Evaporator operates with a very low boiling temperature to minimize heat treatment of the by-products in the effluent. As a result six large Turbofans heating three large Falling Film Evaporator assemblies are employed, two Turbofans per Falling Film Evaporator.

High tube wetting rates in the Falling Film Evaporator assemblies are employed to minimize fouling of evaporative surface areas, allowing the system to operate over long periods of time before cleaning is required. The Forced Circulation High Concentrator naturally operates for extended times between cleanings.

 

Challenge #6: Reduce effluent with high BOD

A Customer approached GEA regarding concentrating the effluent from a Protein(s) processing facility containing a high BOD to reduce the volume of wastewater.

The operator of the facility had to reduce the BOD content of the effluent prior to its discharge into a wastewater system.

Solution #6: A Multiple Effect TVR Evaporator

The Customer required a water removal rate of 12,100 pounds per hour from the effluent stream.

A Multiple Effect Thermal Vapor Recompressor Heated Evaporator was supplied and installed.

A Product
B Concentrate
C Condensate
CC Vapor Condensate
CD Heating steam condensate
D Heating steam

The unit occupies a small footprint (The Thermal Vapor Recompressor operates over the first effect.

A unique feature of this evaporator is that the two effects are combined into a single cylinder - saving floor space.

Request more information Click here to request more information