26 July 2021

In the Republic of Kazakhstan, an investment project to enlarging Aktobe CHPP is being implemented. Here, a cogeneration power unit is being created - a gas turbine unit, which will be integrated into the existing process flow scheme of the facility to operate in a combined cycle. The launch of the GTU is scheduled for 2022.



The main generation will be provided by a Siemens SGT-800 gas turbine with generator with an electric capacity of 50 MW. The SGT-800 industrial turbine combines robust design, high efficiency and low emissions, as well as has high exhaust energy, that allows it to be effectively applied in the combined cycles.

From turbine, exhausted hot gases (fuel combustion products) enter waste-heat boiler manufactured by JSC Machine-Building Factory of Podolsk, which will generate steam with a pressure of 3.0 MPa and a temperature of 420°C in an amount of 70 tons per hour. The resulting superheated vapour of medium pressure is sent to the existing steam turbines of Aktobe CHPP for secondary electricity generation.

Thus, the scheme with the use of combined cycle technology will ensure combined energy generation, high gas fuel efficiency and overall power plant effectiveness. The designed capacity of the GTU is 57 MW.



The fuel supply for new power unit will be performed by the ENERGAS comprehensive gas treatment system which will provide the quality of gas in accordance with the pre-set parameters for purity, temperature, pressure and flow rate. The main elements of this system are a block-type gas treatment station (BGTS) and booster compressor station (BCS).

The BGTS, manufactured by ENERGAS under a special project, is intended for metering, filtration and pressure reduction of gas. The throughput of the station is 15,433 m3 / h – similar to the rated fuel consumption of GTU.

Process unit is equipped with separation system with a two-stage coalescing filters, the trapping of condensate and mechanical impurities occurs here in automatic mode. Gas filtration efficiency is 99.9% for particles larger than 3 microns. Subassembly for gathering and storage of purification products includes an underground drainage reservoir (storage tank) with a volume of 1 m3, a liquid level control device and equipment for removing condensate and sludge into a mobile cistern.

If the pressure in the supply pipeline is higher than the design parameters, then the gas flows through the reducing module. This element of BGTS guarantees a decrease and a stable maintenance of the pressure at a required level, as well as excludes its differences at the inlet to compressor units of the BCS.

To measure the volume of fuel entering the power generating unit, the BGTS is equipped with a two-line process gas-metering unit with a relative error of no more than 2%. Data from him is transmitted via communication channels to the upper level of the APCS.

The gas treatment station is additionally equipped with an outlet fuel quality control subassembly with measuring and analytical equipment. The BGTS is housed in a separate all-weather block-box with the integration of elements on a single frame, equipped with systems of working and emergency lighting, premise heating and ventilation, safety systems.



After preliminary treatment, the gas flow is directed to the ENERGAS BCS, which consists of two modular compressor units (1 in operation, 1 in the hot-standby) intended to compress and feed fuel to the GTU turbine at a pressure of 3.1 MPa.

Both compressor units (CU) made based on screw oil-filled compressors. The maximum capacity of each CU is 12,000 kg / h. Gas flow rate depends on the dynamics of changes in the load of the GTU and is controlled in the range from 0 to 100%. For this purpose, a special two-circuit regulation system is applied.

The process flow scheme of the CU provides for stable maintenance of the designed gas temperature necessary for the normal operation of turbine. The optimal fuel supply temperature is set by the manufacturer of turbo unit (Siemens) and is +60°C.

Taking into account the stringent requirements for the purity of fuel gas, filtration system in BCS is enhanced. Suction lines in compressor units are equipped with a pre-treatment subassembly, which consists of a protective strainer and a highly efficient filter-scrubber. In addition to the gas-oil filter-separator of the 1st stage of purification and the coalescing filter of the 2nd stage, standard placed on the delivery line, the additional (safety) filters for fine purification of gas are built into CU modules. As a result, the residual content of impurities in the fuel at the inlet to the GTU shut-off valve block does not exceed 0.1 ppmw (mg / kg).

Gas-booster units are housed in their own shelters of container type, equipped with life support systems. According to safety requirements, CUs are equipped with fire detection, gas detection, alarm systems, fire-extinguishing systems.



Gas treatment station and compressor station are fully automated. Their control systems are made based on microprocessor technology, using modern software, switching equipment and communication channels and protocols. The local ACSs will be integrated with the facility's APCS. They provide remote control of units, automatic protections and alarm; monitor the process parameters and indoor gas hazard; handle the parameters of the workflows and emergency events; issue information to the operator panel.

BGTS and CUs were delivered to the construction site of the power unit with the maximum degree of factory readiness (98%) what reduces the duration of the pre-start stage. The equipment is characterized by the high maintenance ability and long service life. The technical use ratio is 0.92+, the confirmed rating of operational reliability exceeds 97%.

Comprehensive commissioning of the gas treatment and fuel supply system for the new GTU at Aktobe CHPP (erection supervision, starting-up and adjustment, own and integrated tests) as well as training of operational personnel will be carried out by the specialists of ServicENERGAS (ENERGAS Group).



REFERENCE:

The Aktobe Central Heating and Power Plant is the only source of district heating in Aktobe, the largest city in Western Kazakhstan. In 2020, Aktobe CHPP produced 927.9 million kWh of electricity, which is more than 12% of the region's consumption. Electric and thermal capacity – 118 MW and 878 Gcal / h, respectively.

At the moment, there are six steam turbines and nine boilers installed here. The need for reconstruction and upgrade of the power plant, built in the 40s of the last century, is because some of the main and auxiliary equipment have entirely exhausted their resource.

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