Heat recovery systems and cogeneration units for DG and gas-powered electrical generators

Techexpo LLC delivers heat recovery systems (HRS) for diesel and gas-powered gensets with rated power from 120 to 2500 kW. The main element of the system is a thermal module, also known as a heat recovery unit: it recovers heat from the genset and delivers it to the consumer through the collection point. Combining the HRS with the cooling system of DG and gas-powered gensets (cooling radiators, pumps, piping) provides the thermal and mechanical system of the facility.

Equipping internal combustion engines with a heat recovery system makes it possible to increase the efficiency of electric units by up to 80%.

According to the requirements of Appendix No. 2 to the Order of the Ministry of Energy of the Russian Federation of 16.12.2002 N 448 "On Approval of the Regulations Necessary for the Implementation of the Rules for the Use of Gas and the Provision of Gas Supply Services in the Russian Federation", technological equipment using natural gas as a fuel with a flue gas temperature of more than 200°C, shall be equipped with heat recovery units.

Тепловой модуль утилизации тепла выхлопных газов – фото 1 из 5

Тепловой модуль утилизации тепла выхлопных газов – фото 2 из 5

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Prices for options for thermal modules for diesel and gas-powered gensets:

ТТММ-ТМ.1350 thermal module for a diesel genset based on the MTU-12 V 4000 G21R engine with a power of 1100 kW for 3.5 million rubles.

• Exhaust gas rate – 13 680 m3/h;
• Exhaust gas temperature - 457 °С;
• The maximum heat removal from flue gases at maximum load and temperature drop down to 120 °C after the recovery thermal module will be about 744 kW
• The total heat removal from the coolant will be 600 kW;

The TM is divided into three assemblies inside the container:

• TMM-TMVV.600 (thermal water-to-water module), which includes an antifreeze recovery unit in full piping;
• TMM-TMVG.750 750 (thermal water-gas module), which includes a completely piped exhaust gas recovery unit;
• Automatic control cabinet (control of temperature, water level and pressure in exhaust gas recovery unit and antifreeze recovery unit, start and stop of heat recovery system);

Thermal module for heat recovery of exhaust gases and engine cooling circuit of a 1000 kW diesel genset with a Cummins KTA50-G3 engine: ТММ-ТМ.1350 for 6.3 million rubles.

• Flue gas rate – 5915 kg/h;
• Exhaust gas temperature – 520 °C;
• The maximum heat removal from flue gases at maximum engine load and temperature drop down to 150 °С after the exhaust gas recovery unit will be about 733 kW;
• Name of the exhaust gas heat recovery unit: TMM-TMVG.750;
• The total heat removal from the coolant will be approximately 600 kW;
• Name of the antifreeze heat recovery unit: TMM-TMVV.600;
• Thermal module TMM-TM.1350 consisting of two TMM-TMVG.750 and two TMM-TMVV.600 with control cabinets.

Two TMM-TM.650 thermal modules for a 526 kW gas-powered unit based on a Perkins 4008-30TRS2 engine for 4.7 million rubles.

• Exhaust gas rate on the engine at 100% load -105 m3/min;
• Exhaust gas temperature - 485 °С;
• The maximum heat removal from the exhaust gases at the maximum load of the gas-powered unit and lowering the temperature after the exhaust gas recovery unit to 120 °C is 338 kW;

Thermal module ТММ-ТМ .650 – 2 pieces.

Heat recovery scheme with separate thermal modules

Heat recovery scheme with the sequential passage of antifreeze through a thermal module of exhaust gases and a water-cooled thermal module Installation costs for heat recovery systems

Installation costs for heat recovery systems

An example of the calculation of a feasibility study based on a thermal module for a 1 165 kW gas-powered genset:

• Maximum heat output = 1 350 kW;
• Average thermal power = 1010 kW - when the internal combustion engine is loaded by 75%;
• Average annual operating time of the heat recovery system = 3,000 hours - with a heating season duration of 200 days and daily operation of the internal combustion engine for 15 hours;
• The cost of generating 1 kW/h of heat at the boiler house = 0.56 RUR including VAT - at the gas price of 5 rubles per 1 Nm3;
• Annual heat generation at the heat recovery system = 1010 kW * 3,000 h = 3,030,000 kW/h;

Thus, annual savings are: 0,56 * 3 030 000 = 1 697 000 RUR;

The price of this thermal module is about 3 300 000 RUR, pay-off period - 2 years.

Calculation example for an 800 kW diesel genset

When recovering heat from a diesel genset, the pay-off period is 5 times faster because the cost of heat generation at a diesel-fired boiler house is 5 times higher than at a gas-fired boiler house.

When generating 1 kW/h of electric power, about 1,15 kW/h of heat is recovered, which is a bit less than 1 Mcal (0,001 Gcal).

The average annual loading of gensets usually does not exceed 5000 - 8000 hours. Typically, the annual operating time of TM is from 4000 hours.

DG electric power - 800 kW; DG annual load - 6000 hours;

Heating period - from October to May (8 months);

Then the annual heat generation - 4000 hours

Annual heat generation - 2760000 kW/h

Total annual savings:

2 760 000 * 2,92 = 8 060 000 RUR - compared to heat generation from a diesel boiler;

2 760 000 * 1,03 = 2 840 000 RUR - compared to heat generation from a coal-fired boiler.

Heat cost when generating heat using different kinds of fuel:

The thermal module consists of:

• Antifreeze heat recovery unit
• Exhaust gas heat recovery unit – also known as a heat-recovery boiler
• Bypass lines
• Flue gas flow switch (in a single housing or as part of two screens with a single electric drive and lever mechanism)
• Skid
• Piping manifold of heat recovery units along the routes of antifreeze and network coolant
• Instrumentation and control equipment kit
• Automatic control cabinet

During the operation of the internal combustion engine, thermal energy is recovered in the thermal module as follows:

Antifreeze heat recovery unit removes the heat of the engine antifreeze - instead of cooling the antifreeze on the cooling radiator (cooling tower), the antifreeze gives off its thermal energy to heat the consumer's water.

The exhaust gas heat recovery unit removes heat from the outgoing exhaust gases of the engine: the temperature of the outgoing flue gases at the engine outlet is about 550 °C, the temperature of the gases at the outlet of the exhaust gas heat recovery unit is 120 - 180 °C. This decrease in temperature allows heating the consumer's water.

Heat module design options

Ready-to-operate thermal module

Time of manufacture — from 1,5 months.

The full thermal module recovers all heat generated by ICE. It includes all assemblies for connecting the module to the engine. The control cabinet is included in the scope of delivery and allows the heat recovery unit to work autonomously. The purpose of the module is to heat the coolant (water, antifreeze).

The flow rate is set at the temperature mode of the network coolant (water or antifreeze) 70/95 and the temperature of the exhaust gases after the heat recovery boiler – 120C.

Exhaust gas recovery thermal module

Time of manufacture — 1 month.

It includes a heat recovery boiler and a flow switch mounted on the common base, bypassing gas exhaust line. The exhaust gas recovery thermal module separately from the antifreeze recovery unit is usually used when arranging a cogeneration unit on different floors in a power center building (in this case, the exhaust gas recovery thermal module is usually installed on a floor higher than ICE). Also, the breakdown of the complete thermal module into exhaust gas recovery thermal module and water-cooled thermal module takes place when the cogeneration unit is assembled in a block modular design.

The table shows data for shell boilers. The aerodynamic resistance of the heat recovery boiler does not exceed 3 kPa. The flow rate is set at the temperature mode of the network coolant (water or antifreeze) 80/95 and the temperature of the exhaust gases after the heat recovery boiler – 120C.

Water-cooled thermal module for antifreeze heat recovery

It includes an antifreeze recovery unit, piping manifold including pipeline valves and instrumentation and control equipment.

The rate is set at the temperature mode of the network coolant (water or antifreeze) 70/80.