Cost of a valve is less compared to a turbine cost so can we match the enthalpy drop using a valve for approximate work done by a turbine. using valve we can easily change the enthaply drop.
Sure you can use a valve the expansion process in pipes. Other ideas is to use orifices inside the pipe or even change the pipe diameter from smaller to larger (use pipe segments with different diameter). As long as you are conserving mass, energy, and momentum, you should be fine.
you can use throttling valve for this mission but you should notice that using valves in pressure decrease requires a specific pressure drop range as it could make a pressure drop up to 5 bars if you want higher pressure drop so you need another item such as turbines
Well, I think the early contributors have said it all. Pressure can be dropped or reduced using various devices but a particular choice will depend on the purpose that you want to use the expanded fluid for. Valves you know, are used to regulate the flow of fluids while the turbine is used to do work. This is to add to the other suggestions made by the early respondents. Thanks.
In addition to what I wrote before, as long as you understand Bernoulli equation and the laws of conservation of mass (i.e., the continuity equation), energy, and momentum, you replace the need for a turbine or a diffuser for pipe fluid expansion by any method like adding a valve, an orifice meter, or just change the diameter in piping segments.