THERMAL OIL HEATER

INTRODUCTION

AB&CO Thermal Oil Heaters (also called Thermal Oil Boilers, Thermal Fluid Boilers, Hot Oil Units or Diathermic Heaters) are developed and designed especially for demanding process heating  operations where no compromise on quality are accepted and where reliability is the key word.

The heater solutions from AB&CO are not characterised by low purchase price - but instead low over-all costs including low maintenance and operational costs, and long life-times.
 

Oil & Gas-fired Unit
 

Consequently the AB&CO heaters are made of first class material and components, without any compromise on quality. The pressure part are designed as standard between 10 bar and up to 40 bar pressure (although operation often are atmospheric and unpressurised).

The heaters for thermal oil or heat transfer fluid (HTF) are delivered as complete and fully equipped units with all necessary armatures, instrumentations and safety features.

The thermal oil heaters are delivered as oil-fired, gas-fired, for dual fuel or electrical heated. Other customised options are numerous and include free choice of horizontal alternatively vertical types. The models are designed for minimum 10 bar pressure with capacities in normal range up to 3000 kW, - and up to 10.000 kW on request.

THE BENEFITS OF USING  OIL

Water and steam are typically used as heat carriers in heating systems. But at high temperatures which is often required in process heating systems, water and steam requires a corresponding high operating pressure. Consequently high temperature heating systems with water and steam can be very controversial and expensive - both in relations to personal safety issues, economy, design and projecting.

In Thermal Oil Heating Systems, this special oil-based Heat Transfer Fluid (HTF) is used instead of steam or water as the heat carrier. With this fluid it is quite simple to achieve operating temperatures up to 300°C even at atmospheric pressure. Comparing this to water and steam, it would require a pressure above 85 bar to obtain 300°C operating temperature.

There are several advantages by using the oil-based heat transfer fluid - often you compare Thermal Fluid versus Saturated Steam. Here the most obvious advantages are:

 

	High operating temperatures up to 300°C at atmospheric pressure
	Optional temperature level set-points
	No pre-treatment of boiler feed water
	No heat loss due to hot condensate and flash steam
	No risk of corrosion and no risk of freezing damages.
	Low maintenance costs
	Quiet in operation (no steam stroke and flash steam noise)
	Easy to operate (does not require steam boiler certified staff)

 

 

Why  thermal fluid instead of steam ?  Read more

 

 

EXTENT OF DELIVERY

The thermal oil heaters can be delivered in horizontal design (with low height), or in vertical design (occupying limited floor space).

See the sketches below.

The heater units are delivered thermal insulated and with heat shields. The enclosure is stainless steel cover sheets. The unit design includes burner (or electrical heating elements), armatures, instrumentation, safeties and control panel - and with full documentation including the necessary certificates.

Accessories can be chosen in order to complete the thermal oil heating system. Many of these accessories can be build on a complete skid-mounted unit  - or the can be build into a container-solution.

AB&CO also deliver complete thermal fluid heating systems (read more about the system solutions in column on the right column).

SPECIAL DESIGNS

Beside the standard execution, the heaters can be delivered in e.g. following variations:

	Electrical heated
	Flue gas heated
	Steam heated
	Combination of heat sources
	Container-solutions
	Skid-mounted units
	Complete heating systems
	Parts made in stainless steel
	Customised design - special requests

CONSTRUCTION & THERMAL DESIGN

The oil/gas-fired heaters from AB&CO are made with an internal arrangement of winded-up tube coils made of 3.1/PED-certified steel pipes. The oil-based Heat Transfer Fluid (HTF) is heated gradually to the operational temperature during the circulation inside the coiled up tubes - while the heat is transferred to the HTF. Firstly it is done as radiant heat in the combustion chamber, where the inner cylindrical tube coil and a flat tube coil forms the chamber wall and the bottom respectively (consequently refractory concrete is avoided). Secondly the heat is transferred as convection heat from the combustion gasses (consequently being cooled) through the tube wall to the HTF. This takes place in the outer surrounding convection part i.e. the outer tube coil, as the gasses pass the space gab between the two tube coils, and thereafter the outer tube coil and shell. The thermal design ensures both a defined and constant velocity of the thermal oil, but also a modest volume of the thermal oil relative to the size of the heater. The coil design allows unlimited thermal expansion caused by the high fluid temperature.

The heater and the complete thermal oil heating system in general are constructed and equipped according to the recognised and comprehensive German standard DIN 4754, while atmospheric vessels and pressure vessels are made according the European regulations including the pressure vessel code PED 2014/68 EU, and according to all relevant EN-norms.

Container Solutions - closed type container

 

Container Solutions - open type container
 

Horisontal Skid-mounted Unit
 

Vertical Skid-mounted Unit

The electrical heated thermal oil heaters are build-up as a battery of one or several pressure vessel modules equipped with with conventional tube type or pull-out ceramic heating elements.

 

Electrical Heated Unit

 

Electrical Heated Skid-Mounted Solution
 

These electric thermal oil heaters are not only designed as heaters, they are also calculated and designed as heat exchangers involving - for each project/application/task - individual heat transfer and flow calculations on the heater elements, and their surfaces and geometry.

This is done in order to control the surface temperature of the electrical heating elements and thereby preventing critical temperature in both heating elements and the oil film of the HTF (preventing element blow-off and oil cracking respectively).

All thermal oil heaters are carefully checked, controlled and functional tested prior to dispatch from the workshop.

BURNERS & ELECTRIC HEATING ELEMENTS

The oil/ and gas-fired thermal oil heaters are equipped  only with international recognised  high-quality burner brands - adapted to operation on gas, light fuel oil, heavy fuel oil or combinations (dual fuel) and even fish oil and solid fuel. Individual demands for special burner designs can be meet and adapted in the heater design - for instance burners for combustion of bio-gas and other low caloric or even corrosive fuel gasses.

The electrical heated units are delivered in two options. The conventional electrical tube heating elements are used typically for low temperature applications and the costs for these are correspondingly low. The elements are especially designed for demanding tasks which means a.o. using the special and extreme high temperature resistant Incoloy 825 alloy.

For other applications, low and easy maintenance might be an important demand. In that case it can be recommended to use full welded steel tube, where the inner heating wires place in ceramic elements can be pulled out, without emptying the heater for oil.

The engineers at AB&CO calculate the optimum heat load in the heater individually i.e. for each task, - ensuring that the film temperature of the thermal oil is never exceeded  even during stop and start.

FLUE GAS COOLERS - ECONOMISERS

Whenever it might not be possible to use electrical heating using electricity from wind power, nuclear power or water power, - the environmental challenge is to use oil and gas-fired solutions, but at the same time to reduce the fuel consumption and thus the emission.

In this context the low flue gas temperature  is the key word. The heat recovery is done by utilisation of  the quite large amount flue gas heat recovered in flue gas coolers also known as economisers. AB&CO offer complete systems that involves high efficiencies and at the same time very low pay-back times.
 

Economisers can be delivered as build-on to the oil or gas-fired heater, for heating external colder fluid e.g. water. Alternatively the thermal oil heater can be made as a flue gas heat exchanger - a recuperator where the external heat source is hot flue gas.

CO₂-REDUCTION, HEAT RECOVERY
AND OTHER ENVIRONMENTAL ISSUES

Heat recovery - for instance as described above - and other environmental considerations have always been a standard topic at AB&CO, long before these became a official worldwide protocol. A lot of money is available by thinking "green". For that reason AB&CO offers consultant services. This offered arrangement has become very popular worldwide. See more about this at AB&CO · CONSULT

THE HEAT TRANSFER FLUID
'THERMAL OIL'

The circulating heat transfer fluid, also known as the thermal thermal oil needs to be correct chosen. Compromise on this issue can easily result in huge problems - but economical and with respect to ensure personal safety. It cannot be emphasized strong enough how fatal bad, old and and inappropriate thermal oil can be for the thermal fluid heating system.

Use a quality brand of thermal oil and make sure that this fluid correspond how the heating system is operated.

An important maintenance detail is that every 6 - 12 months, a sample should be taken from the system and send to a qualified laboratory (make sure that they know about thermal fluid systems and what traces they should look for in the sample) or directly to AB&CO.

Due to this important issue, AB&CO has established a department dealing with thermal fluid supply and sample analysis:

It is recommended to use a non fouling, high temperature resistant thermal oil for the applications as decribed here as the  AB&CO Heat Transfer Fluid.
 

THERMAL OIL SYSTEM SOLUTIONS

A correct and safe system design is very important for high temperature systems. This can be ensured by using AB&CO as system supplier of the whole system.

The engineers of AB&CO will design the heating system in a close dialog with the customer and/or the contractors. Visits on site can be provided in connection with kick-off meeting, commissioning and start-up.

AB&CO have 20 years experience with thermal oil heating (hot oil) solutions world-wide - both new installations or modified systems.

Complete Thermal Fluid Heating Systems with heaters, heat exchangers, tanks, pumps, armatures, instrumentations and piping can be delivered as package solutions and as skid-mounted units - individually designed according DIN4754.

Consulting Assistance on design of systems and parts hereof, modification and trouble-shooting within thermal oil heating systems, can provided on request by AB&CO · CONSULT, who have more than 25 year experience working with thermal oil heating.
 

  
More info about
  the 'R&D Workshop'

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